Principle of Explosion Protection

Principles ofExplosion Protection

Cooper Crouse-Hinds GmbHYour Partner for Explosion Protection

406

1Cooper Crouse-Hinds GmbH

Foreword 3

The history of explosion protection 4

Fundamental principles of explosion protection 6

Explosive atmosphere 6Ignition sources 6Flash point 7

Primary and secondary explosion protection 8

Potentially explosive atmospheres 9

Zone classification 9

EC directives on explosion protection 11

Directive 94/9/EC of the European Parliament and Council dated March 23rd, 1994 ATEX Directive 12

Scope of application 12Essential safety requirements 13Groups and categories of apparatus 13Putting in circulation and commissioning of apparatus 15Procedures in event of unsafe apparatus 15Marking 15Provisional arrangements 15

CE marking 16

Apparatus safety law (GSG) 18Decree concerning the putting into circulation of apparatus and protectivesystems for use in potentially explosiveatmospheres – explosion protectiondecree (ExVO) 18Directive 1999/92/EC of the EuropeanParliament and Council dated December 16, 1999 19Structure of Directive 1999/92/EC 19Zone classification 19Explosion protection document 20

Decree on health and safety protectionrelating to the provision of work equipmentand the use thereof during operation,safety during the operation of installationsrequiring supervision and the organisationof operational safety provisions (Operatio-nal Safety Decree – BetrSichV) 21

Electrical apparatus for use in potentiallyexplosive atmospheres 22

Principles 22

Types of protection for explosion-protected apparatus 24

General requirements acc. to EN 50 014 24

Oil immersion ”o”: EN 50 015/VDE 1070/0171, Part 2 25

Pressurization ”p”:EN 50 016/VDE 0170/0171, Part 3 25

Sand filling ”q”:EN 50 017/VDE 0170/0171, Part 4 26

Flameproof enclosure ”d”:EN 50 018/VDE 0170/0171, Part 5 27

Increased safety ”e”: EN 50 019/VDE 0170/0171, Part 6 28

Encapsulation ”m”:EN 50 028/VDE 0170/0171, Part 9 29

Intrinsic safety ”i”:EN 50 020/VDE 0170/0171, Part 7 30

· Technical terms 30· Fundamental data 30· Limiting ignition curves 31Safety levels of intrinsically safe and associated electrical apparatus 31Constructional requirements 32Types of limiting modules 32· Isolation of intrinsically safe circuitsfrom non-intrinsically safe circuits 32

Apparatus for intrinsicallysafe circuits 32Design of intrinsically safe circuits 33Working on and testing of intrinsically safe circuits 33

Intrinsically safe electrical systems ”i”EN 50039 / VDE 0170/0171, Part 10 34

Cap lamps for use in mines susceptible to firedamp EN 50033/VDE 0170/0171, Part 14 35

Zone 0 apparatusEN 50284/VDE 0170/0171, Part 12 36

Zone 2 apparatus 37Type of protection ”n”EN 50 021/VDE 0170/0171, Part 16 37

Electrical apparatus for use in areas withcombustible dusts 39

Ignition sources 39Electrical apparatus for use in areas with combustible dust with protection by the enclosure 39

Electrical installations in potentially explosive atmospheres Assessment of explosion hazard 41

Obligations of the manufacturer 42Obligations of the installer 42Obligations of the operator 43

Table of Contents


Selection criteria for electrical apparatus 44Fundamental installation requirements 45Electrical protection and monitoring devices 46Cables 46Additional requirements 46

Maintenance and repair of explosion-protected apparatus 48

Rules, regulations and decrees 48Maintenance 48Special safety measures 48Operation 49Constant supervision 50Servicing 50Repairs 51

Definition of potentially explosive atmospheres and requirements for explosion-protected apparatus on the world market 52

NEC 52Table of comparison NEC IEC/EN 52

IP degrees of protection 54

Table 1 Procedure for the assessment of the zone classification acc. to BetrSichV,EX-RL and VDE 0165 55

Table 2Explosion protection at a glance 56

Annex 1 Sample of an installation certificate 57

Annex 2Sample of a hot work permit 58

Annex 3Bibliography 59

Annex 4Harmonized standards to Directive 94/9/EC 60


Foreword

This publication provides a brief survey of theessential aspects of explosion protection. Thestatutory regulations define the obligatory dutiesof manufacturers, installers and operators ofelectrical installations in explosive atmospheres.Important information can also be found in thedirectives of the employers” liability insuranceassociations and the VDE regulations.At the end of this publication there is a list ofliterary references for the interested reader.

The history of explosion protection

In 1909 Concordia Elektrizitäts-Aktiengesell-schaft, later called CEAG, began to manufacturefiredamp protected electrical miners lamps forthe mining industry. Up to that time, only lampswith a naked flame had been available. The firstcontributions regarding safety had been made in1815 by the English chemist, Sir Davy whodeveloped an oil lamp that prevented the propa-gation of the flame through a close meshedscreen.

The fundamental experiments made by Dr.-Ing.e.h. Carl Beyling, a mining engineer, relating tosafety against firedamp of specially protectedelectrical motors and apparatus in coal mineswas a decisive step in the development ofexplosion protection. The governing design prin-ciples of firedamp protection devices on electri-cal machines, transformers and switchgeardating from 1912 were based on the results ofthese experiments. As protective measures, thefollowing types of protection were accepted:

• Flameproof enclosure (at that time called closed encapsulation)

• Plate encapsulation• Oil immersion• Close meshed screen

Since 1924 only incandescent lamps were per-mitted for lighting hazardous areas, the luminouselement of which was hermetically sealed. Theincandescent lamps had to be protected withstrong glass bells which also tightly enclosed thelampholder.

Light switches had to be installed outside of thehazardous locations, and in the case of a failureor the lack of explosion-protected lighting,access to these locations was only permittedwith safety lamps. Therefore, in general electricalinstallations in hazardous locations were dispen-sed with.

Machines containing slip rings or commutatorshad to be designed so that the slip ring or com-mutator space was at least enclosed andthoroughly purged under overpressure withextraneous air or a suitable gas. Purging had tostart prior to switching on the machine, or themachine had to have a flameproof enclosure.This requirement applied to any locations thatwere subject to the hazard of gas or vapour/airmixtures.

The guiding principles issued in 1935 on themounting of electrical installations in hazardousproduction areas and storage rooms (VDE0165/1935) were to be the first German regulati-ons on the protection of hazardous installations.

The fundamental revision of these regulationsbegan with the VDE regulations 0171 ”Con-structional regulations for explosion protectedapparatus” which finally came into force in 1943.They provided the manufacturers of electricalequipment for use in explosive atmosphereswith the necessary documents for a safe designand construction. This regulation not onlydescribed the individual types of protection andtheir scopes of application, but also included anumber of constructional specifications andintroduced the identification marking (Ex) for theelectrical apparatus made in compliance with it.

The governing principles and specifications ofthe VDE regulations 0165 and 0171 constitutedthe basis of the police decree dated October 13,1943 for electrical apparatus in hazardous loca-tions and in mines subject to the hazard of fire-damp. The police decree primarily aimed at themanufacturers of electrical apparatus. It laiddown that explosion protected electrical equip-ment was only allowed to be put in circulation,installed and operated if it conformed to the so-called VDE regulations and had successfullypassed the type and routine tests specified wit-hin.

The factory inspectorate division was chosen tobe the competent authority to define whatextent a room or plant might be subject to the hazard of explosion.

The decree of 1963 regarding electrical installati-ons in explosive atmospheres (ExVO), today cal-led ElexV, not only imposed the obligation tohave the explosion protected apparatus testedby the Federal Physico-Technical Institute (Phy-sikalisch-Technische Bundesanstalt PTB) or theMining Test Station (BVS), but also the obliga-tion to obtain the design approval from the aut-horities of the competent federal state.

Miner”s lamp



Research papers by

C. Beyling, mining engineer

In 1975 the Council of the European Communityissued basic directives on explosion protection.The European standards for hazardous areaswere worked out by CENELEC, the Europeancommittee for electrotechnical standardization.In Germany the new European standards EN 50014 to EN 50 020 were adopted as VDE stan-dards as part of the national standards works.These new standards DIN EN 50014 to50020/VDE 0170/0171, Parts 1 to 7, designa-ted as VDE regulations, came into force on May 1, 1978, and the new statutory provisionson July 1, 1980.

By means of this statutory order now calledElexV, the expertise of the testing establish-ments and the design approval are replaced bya type sample test. The type sample test is car-ried out by any authorized testing establishmentof the member states of the EU. The certificatesof conformity and inspection granted on thebasis of the said test are mutually acknowledgedas type sample test certificates by all memberstates of the EU.

The directive 94/9/EC for the harmonization sta-tutory provisions of the member states relatingto apparatus and protective systems for useaccording to the rules in potentially explosiveatmospheres, issued on March 23, 1994 by theEuropean Parliament and Council, substitutesany directives concerning explosion protectionexisting on a European level as from July 1,2003. The European Parliament determinedMarch 1, 1996 as the date for conversion of thisnew directive into national law.

On December 12, 1996 the directive 94/9/ECwas converted into national law by the seconddecree concerning the equipment safety lawand the changes relating to the equipmentsafety law by the explosion protection decree(ExVO). With this decree the acetyl decree, VbFand Elex were also assimilated with the Euro-pean law. On account of a transition period uptill June 30, 2003, manufacturers, testing autho-rities and operators were now confronted withvarious decrees that were similarly worded.

On January 28, 2000 the second importantdirective relating to explosion protection waspublished in the official gazette of the Europeancommunities. The directive 1999/92/EC relatingto minimum requirements for the improvementof the health protection and the safety ofemployees who may be endangered by potenti-ally explosive atmospheres was issued onDecember 16, 1999 by the European Parliamentand council.

This directive was converted into national law on03.10.2002 in the ”Decree on health and safetyprotection relating to the provision of workequipment and the use thereof during operation,safety during the operation of installations requi-ring supervision and the organisation of opera-tional safety provisions (Operational SafetyDecree – BetrSichV). The BetrSichV replaces theElexV for explosion protection. However, withinthe scope of the transitional regulations, theElexV can still be applied for installations thatwere commissioned before 03.10.2002.


Fundamental principles ofexplosion protection

Explosive atmosphere

An explosive atmosphere is built up of a mixtureof flammable gases, vapours, mists or dustswith air, including the usual constituents such ashumidity. After ignition, a reaction in the explo-sive atmosphere is automatically propagatedunder atmospheric conditions.

Atmospheric conditions are defined as an abso-lute pressures ranging from 0.8 to 1.1 bar andmixture temperatures from -20° to + 60°C.

Although it is often not mentioned, a normaloxygen content of air of ca. 21 per cent byvolume is just as important. This limitation isnecessary, as the essential safety parametersfor the explosion protection of flammable sub-stances are a function of the pressure, tempera-ture and oxygen content and can only be consi-dered to be sufficiently constant if they are wit-hin the limits stated above for these parameters.

The European directives and their implementarydecrees are, however, based on this definition.

In addition to this, the risk of explosion existswhen two other conditions are fulfilled at thesame time:

• The proportion of flammable matter is sohigh that an explosive mixture can be formed.

• There is an ignition source in the same areathat can ignite the mixture.

Such a mixture is capable of exploding when,under atmospheric conditions its concentrationis within certain limits specific to the type of sub-stance. The lower explosive limit defines theconcentration up to which a mixture is not yetcapable of exploding. The upper explosive limitdefines the concentration up to which the mix-ture is capable of exploding. Under conditionsother than atmospheric, the explosion limitschange. As the proportion of oxygen increases,e. g. the upper explosive limit is raised.

Generally, the explosive limits are indicated inpercent by volume. Percent by volume, abbre-viated %/vol., means the volume percent of thecombustible matter in the mixture. The lowerexplosive limit of hydrogen is 4.0 % by volume,and the upper explosive limit 75.6 % by volume.The safety coefficients define quantitative dataabout the properties of most of the known sub-stances.

If, in the event that an explosive mixture is igni-ted, people are directly or indirectly endangered,this is then classed as a potentially explosiveatmosphere. Whether or not an atmosphere ispotentially explosive can be roughly assessed. Inenclosed rooms, regardless of their size, 10 lit-res of explosive atmosphere are already consi-dered hazardous. If the volume of the room isless than 100 m3, this also applies to smallerquantities.

Ignition sources

Ignition sources that can cause an explosion,are:• Electric sparks and arcs, e. g.

– when circuits are opened and closed,– when electrostatically charged components

are discharged,– at the contact points of switchgear,– when cables are ruptured,– in the event of a short-circuit, or electric

compensating currents• mechanical sparks produced by friction,

impact and grinding• hot surfaces such as live conductors in

windings of motors, heat conductors,bearings, shaft bushings

• electrostatic charges as a result of a separating process involving at least onechargeable substance. (Running down of foilsover rollers, driving belts, filling andemptying of liquids and powdery substances.)

Although of minor importance, the following igni-tion sources should also be mentioned:• glowing particles • flames• compression and shock waves e. g. when

vacuum flasks and fluorescent lamps break• electromagnetic waves in the optical region of

the spectrum• ultrasonics: causes temperature rise• radiation

– high-frequency– radioactive radiation– X-radiation

• chemical reactions


Flash point

An explosion hazard can also result when aflammable liquid evaporates at the surface. Thisresults in a vapour/air mixture which, under givenconditions, forms an explosive atmosphere.

In order to do so, the temperature must havereached the flash point of the liquid. The flashpoint is the lowest temperature at a pressure of1013 hPa (normal air pressure) at which vapoursdevelop in such a quantity that a flammable mix-ture forms above the liquid.

In accordance with the ”Technical directive onflammable liquids” (TRbF), flammable liquids aredivided into four classes according to their flashpoints:

When the Operational Safety Decree (BetrSichV)came into force, this classification was replacedby the classification according to the HazardousSubstance Decree:

Highly flammable• Liquid substances and preparations with a

flash point below 0 ºC and a boiling point ofmax. 35 ºC

• Gas-like substances and preparations that areflammable at a normal temperature and nor-mal pressure when they come into contactwith air

Easily flammable• Solid substances and preparations that can

be easily ignited by the short-term effect of anignition source and that continue to burn orglow after the ignition source has been remo-ved

• Liquid substances and preparations with aflash point below 21 ºC, but that are not highlyflammable

Flammable• Liquid substances and preparations with a

flash point of at least 21°C and max. 55 ºC

The old classification may still be applied for exi-sting installations during the transitional periodstated in the Operational Safety Decree.

If they are whirled up, combustible dusts thatare evenly distributed in a layer of less than 1 mm and at normal room heights can alsocompletely fill a room with an explosive dust/airmixture.

More details on this subject can be found in thechapter ”Potentially explosive atmospheres”.

Class of hazard Flash point

AI < 21° C

AII 21 to 55° C

AIII > 55 to 100° C

B < 21° C, at 15° C soluble in water

Oil terminal


Primary and secondaryexplosion protection

Avoiding the danger of an explosion is alwayspreferable to any protection against explosion.An explosion can be prevented if the creation ofan explosive atmosphere can be excluded.Measures to this end are summarized under theheading Primary Explosion Protection.

Avoidance of flammable substancesFlammable substances should, whenever possi-ble, be substituted by substances that are notcapable of forming an explosive mixture.

Observance of the flash pointHere distinction is made between two procedures.

Raising the flash pointThe flash point of a flammable liquid must be atleast 5 K above the processing temperature orthe room temperature. In the case of water-soluble, flammable substances this can beachieved by adding water.

Lowering the processing temperatureWith this method it is necessary to apply techni-cal measures (e.g. cooling) to ensure that theprocessing temperature is always at least 5-10K lower than the flash point. It is, however,necessary to keep faults, standstills, leakagesand other influence factors safely under control.

Limitation of the concentrationThe build-up of an explosive atmosphere can beprevented if it is possible to limit the concentra-tion of a substance to the range below the loweror above the upper explosive limit. This can frequently be achieved with gases. Dif-ficulties arise in the event of gas leaks or if theignition range has to be passed when the plantis started or switched off. With liquid substances, the concentration isusually kept below the lower explosive limit,since it requires a very high effort to keep theconcentration in the upper range.Such measures cannot be applied for dusts,since it is practically impossible to achieve aneven distribution.

InertisationIf the proportion of oxygen in a mixture is lessthan 10 percent by volume, then, as a generalrule, an explosive mixture does not exist. Inorder to reach such a low proportion, so-calledinert gaseous substances such as nitrogen, car-bon dioxide, water steam or halogenatedhydrocarbon are added to the mixture until thedesired concentration is obtained.If the percent by volume of the inert gas to theflammable gas is in the minimum ratio of 25:1,an explosive atmosphere cannot build up,regardless of the quantity of air added.

VentilationThe formation of a hazardous explosive atmos-phere can be prevented or restricted by ventila-tion. In rooms above ground level and withoutspecial ventilation, the air is renewed by naturalventilation once per hour. By way of compari-son, the exchange of air in cellar rooms takes upto 2.5 hours. The concentration of the mixturecan, however, only be calculated if the escapingquantity per unit of time of a flammable sub-stance is known and if an equal distribution canbe assumed.

The natural flow conditions in a room can beassessed by an expert on ventilation, who willthen usually recommend an artificial ventilation.Compared to natural ventilation, it ensures theexchange of larger quantities of air and a morecarefully directed air flow. Moreover, the con-centration occurring can be determined with aconsiderably higher degree of reliability. On theother hand, the drawback of a ventilation bytechnical means is that it needs constant servi-cing. In addition to this, precautions have to betaken in case the installation should operate at alower output or fail altogether.

Explosion-proof designThe explosion-proof design is a constructionalmeasure that does not prevent an explosion, butrestricts its effect to a harmless degree. Theapparatus must be designed in such a way thatit withstands the maximum explosion pressureand, in extreme cases, even the detonationpressure. With pipes and other long, stretched-out constructions a detonation is easily possible.If the explosion-proof design is not able to with-stand the increased pressure, effective pressurerelief must be provided.

Secondary explosion protectionAfter all the possibilities of primary explosionprotection have been exhausted, there can stillbe areas where a hazardous explosive atmos-phere occurs. These areas are called hazard-ous areas or potentially explosive atmospheres.Secondary explosion protection with protectivemeasures against ignition that render ignitionsources ineffective applies for such areas.Secondary explosion protection encompassesall electrical apparatus for use in hazardousareas.

Examples for the avoidanceof flammable substances

Flammable Substitutesubstance

Flammable solvents Hydrous solutionsand detergents

Flammable Non-flammablepulverized filling substancessubstances


Potentially explosiveatmospheres

Zone classification

Potentially explosive atmospheres are dividedinto six zones in accordance with EC-Directive1999/92. This was converted into German law inthe Operational Safety Decree BetrSichV. The classification is based on the probability ofthe build-up of a potentially explosive atmos-phere. In addition, distinction is made betweenflammable gases, vapours and mists on the onehand, and flammable combustible dusts on theother. Information on the zone classification can alsobe found in the Explosion Protection Rules ofthe Employers” Liability Insurance Associationfor the Chemical Industry and EN 60079-10.

Classification of potentially explosiveatmospheresZone 0An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists is present for long periods orfrequently.Zone 1An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists can form occasionally undernormal operating conditions.Zone 2An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists does not normally occur oronly occurs for a short period under normal ope-rating conditions.Zone 20An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair can be present for long periods or frequently.Zone 21An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair can form occasionally under normal opera-ting conditions.Zone 22An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair normally does not occur or occurs for a shortperiod only under normal operating conditions.Notes:1. Layers, deposits and accumulations of com-bustible dust are to be considered in the sameway as any other source that form an explosiveatmosphere 2. ´Normal operation` is understood as beingwhen installations are being used within theirdesign parameters.

Which explosion protected electrical apparatusmay be used in the individual zones?

Zone 0Zone 0 mainly encompasses areas such as theinside of enclosed containers, pipes and appa-ratus that contain flammable liquids. The res-pective operating temperature lies above theflash point. The potentially explosive atmospherelies above the surface of the liquid and not in theliquid. Most gases of flammable liquids are hea-vier than air and spread in a similar way toliquids.

Cavities such as pits or pump sumps canusually accommodate these explosive gases forlonger periods, so that here it is also necessaryto expect a Zone 0 area.

With apparatus for Zone 0, ignition sourcesmust be protected against explosion even if theoccurrence of failures is only rare. Hence, theapparatus must meet the following require-ments:Should one type of protection fail or shouldtwo faults occur simultaneously, sufficient pro-tection against explosion must still be ensured.

The constructional requirements EN 50284 (VDE0170/0171, Part 12-1) state that the necessaryexplosion protection is attained if the apparatus

• is built in accordance with the type of protec-tion ”ia” to EN 50 020, or

• conforms to at least one type of protectionaccording to EN 50 015 to EN 50 020, and ifthe scope of the protective measures includesa second independent type of protection.

For example, flameproof luminaires were addi-tionally pressurized, or intrinsically safe appara-tus were additionally encapsulated acc. to EN50 028. According to the directive 94/9/EC,apparatus for Zone 0 must comply with theCategory 1G.

In Zone 0 the hazard of an ignition due to elec-trostatic charge is particularly high. For this rea-son the relevant standard DIN EN 50 284 con-tains extremely detailed requirements thatexceed the requirements of DIN EN 50 014.

Zone 1Flammable or explosive substances are made,processed or stored in Zone 1. This includes thearea surrounding charging doors and in theclose vicinity of filling and discharging facilities,the vicinity of fragile equipment, pipes andglands on pumps and slides that do not sealadequately. It is likely that an ignitable concen-tration will occur during normal operation. Igni-tion sources that occur during normal, trouble-free operation and those that usually occur inthe event of operating disturbances, must beexplosion-proof.The chapter ”Electrical apparatus for use inpotentially explosive atmospheres” describes theindividual types of protection. According toDirective 94/9/EC, Zone 1 apparatus must com-ply with the Category 2G.

Ex-protected torch for use in Zone 0: specially certified for

the increased requirements in this hazardous area

Ex-control switch and ex-safety switch with pipe fixing,

certified for use in Zones 1 and 21


Zone 2Zone 2 encompasses areas around Zone 0 andZone 1, as well as areas around flanged jointson pipelines in enclosed rooms. Furthermore, itincludes such areas in which, due to natural orforced ventilation, the lower explosive limit isonly reached in exceptional cases, such as theenvironment of outdoor installations. Zone 2 applies to areas where flammable orexplosive substances are manufactured or sto-red. The probability that an ignitable concentra-tion will occur is rare and then exists only for ashort period.

During normal, trouble-free operation, ignitionsources must be explosion-proof.The use of all apparatus that satisfies the requi-rements for Zone 0 and Zone 1 apparatus ispermitted. According to Directive 94/9/EC, apparatus forZone 2 must comply with the Category 3 G.

Zone 20Apparatus for Zone 20 shall be specially appro-ved for this purpose, e.g. grain silos. Construc-tional requirements for apparatus for this zonewhere protection is afforded by the surroundingenclosure, can be found in DIN EN 50281-1-1.Further standards, e.g. for apparatus in the typeof protection Intrinsic Safety, are being prepa-red. According Directive 94/9/EC, apparatus forZone 20 must comply with the Category 1D.

Zone 21Among others, Zone 21 encompasses mills,warehouses for coal or grain, and the area sur-rounding filling stations. Here explosive clouds ofdust can develop due, for example, to the occa-sional escaping of dust from the opening. Therisk of hazards due to dust deposits is oftenunderestimated. Explosive dust/air mixtures candevelop due to the formation of a smoulder spotor of a low temperature carbonization gas, aswell as due to the deflagration of a low tempera-ture carbonization gas or to the whirling-up ofgas caused by glowing combustion. Accordingto Directive 94/9/EC, apparatus for Zone 21must comply with the Category 2D.

Zone 22Under normal operating conditions it is notnecessary to expect the occurrence of an explo-sive dust/air mixture in Zone 22. It is only neces-sary to expect an explosive atmosphere due, forexample, to whirled-up dust deposits in theevent of a breakdown. According to Directive94/9/EC, apparatus for Zone 22 must complywith the Category 3D. According to DIN/EN50281-1-1, in the event that conductive dustsare present in an installation, the apparatus usedshall be in the IP degree of protection that corre-sponds to that specified for the Category 2D.

Detailed information on all zones can be found inthe chapter ”Erection and operation of electricalinstallations in potentially explosive areas”.

Ex-protected fluorescent light fitting with electronic ballast

for use in Zones 2 and 22


ces with potentially explosive atmospheres and,as a result of it, graded safety features for the”apparatus” being used. Since the new directive was formulated inaccordance with the ”New Approach” of the EC,this involved the introduction of the manufactu-rer”s declaration of conformity in conjunctionwith a CE marking of the products for explosionprotected apparatus as well.A detailed explanation with regard to the direc-tive 94/9/EC is included in the chapter ”Directive94/9/EC of the European Parliament and Coun-cil of March 23rd, 1994”.

The adjacent chart shows a brief comparison ofthe main differences between the rulings accor-ding to the old and the new directive.

Directive 79/196/EEC Directive 94/9 EC

Scope Electrical apparatus Electrical and non-electrical apparatus and protective systems

Potentially explosive gas Potentially explosive gasatmospheres and dust atmospheres

Distinctive communitymark for the freemovement of goods

Certificate Certificate of conformity Manufacturer”s declaration Inspection certificate of conformityby a notified body The basis is a type

certificate issued bythe notified body

Quality assurance Not referred to Requiredsystem

Fields of application Regulated by standards Direct regulationand construction of in the directivethe apparatus – Apparatus groups

– Apparatus categories – Basic safety requirments

Marking of apparatus Regulated by standards Laid down in the directive

Free trade within the EuropeanCommunity

The basis for the free movement of goods withinthe European trade area was established in thearticles of association of the EEC.

Article 100a of the contractNew version of Article 95A series of European standards for explosionprotected apparatus was drawn up by the Euro-pean Standards Committee for electrical appa-ratus (CENELEC) to provide the basis for theenforcement of the requirements. Directive79/196/EEC of the European committee provi-ded the legal basis.

This ”old” directive was restricted to explosion-protected electrical apparatus and the regulati-ons that were required for the free movement ofgoods. By rigidly referring to the European stan-dards, the normative basis for the certification ofexplosion-protected electrical apparatus wasregulated by ”notified bodies”.

The ”new” directive 94/9/EC regulates the requi-rements for ALL apparatus and protectivesystems for use in potentially explosive atmos-pheres. In addition, the directive now includesthe ”Basic safety requirements” for explosion-protected apparatus. Manufacturers of explo-sion-protected apparatus must provide evidenceof a quality assurance system that is to be veri-fied by a ”notified body”. Another new features isa description of the hazardous areas in workpla-

EC directives on explosion protection


Set-up of the directive 94/9/EC

Disposing part

Chapter Clause Heading

I 1 – 7 Scope of application, putting in circulation and free movement of goods

II 8 – 9 Conformity assessment procedures

III 10 – 11 CE marking of conformity

IV 12 – 16 Concluding provisions

Annexes

I Criteria of decision for the classification of groups of apparatus in categories

II Essential safety and health requirements for the conception and construction of apparatus and protective systems for use in potentially explosive atmospheres

III Module: EC- type-examination

IV Module: Quality assurance of the production

V Module: Inspection of the products

VI Module: Conformity with the design

VII Module: Quality assurance of the product

VIII Module: Internal production control

IX Module: Individual test

X CE marking and contents of the EC certificate of conformity

XI VMinimum criteria to be taken into account by the member states for the authorization of testing laboratories

Directive 94/9/EC of theEuropean Parliament and Council dated March 23, 1994- ATEX directive –

The purpose of this directive is the assimilationof the statutory stipulations of the member sta-tes of the European Union concerning apparatusand protective systems for use in potentiallyexplosive atmospheres.

As of July 1, 2003 it replaced any existing direc-tives concerning explosion protection on a Euro-pean level. The European Parliament fixed July1st, 1996 as the date for the conversion of thenew directive into national law.

The four chapters of the disposing part are sub-divided into 16 clauses. In the chapters refe-rence is made to the annexes I to XI, whichinclude 7 modules

Scope of applicationThe directive, also known as the ATEX directive,applies to apparatus and protective systemsthat are designed for use in potentially explosiveatmospheres. Safety devices and controlsystems for use outside of potentially explosiveatmospheres also come under this directive.This applies when such devices are required forthe safe operation of apparatus and protective

systems or contribute to it. The definitions for some terms relating to explo-sion protection in this directive are different tothose found in the International Electro-technicalDictionary.Apparatus and protective systems designed foruse in hazardous areas:

Apparatus is machinery, equipment, stationaryor portable devices, control units and parts ofequipment, as well as warning and preventivesystems that, either individually or in combina-tion, are designed for the generation, transmis-sion, storage, measurement, control and con-version of energy and for the processing ofmaterials that feature inherent ignition sourcesand are, therefore, capable of causing an explo-sion.

Protective systems are all devices that imme-diately stop an explosion in its very beginningand/or limit the area covered by an explosion.They are put into circulation as independentsystems. The components of the apparatusdefined above are not regarded as protectivesystems.

Components are those parts that are requiredfor the safe operation of apparatus and protec-tive systems without, however, fulfilling an inde-pendent function.

An explosive atmosphere is a mixture of airwith flammable gases, vapours, mists or dustsunder atmospheric conditions in which, afterignition has occurred, the process of combus-tion is propagated to the whole unconsumedmixture.

In a potentially explosive atmosphere theatmosphere can become explosive due to localand operational conditions.

The scope of application of this directive doesnot include:• medical equipment designed for use in

medical areas,• apparatus and protective systems with which

an explosion hazard is only possible if explosives or chemically unstable substancesare present,

• apparatus intended for use in domestic andnon-commercial surroundings in which anexplosive atmosphere can only rarely be formed, and then only as a result of an inadvertent leakage of fuel,

• personal protective outfits,• ocean-going vessels and mobile offshore

plants, as well as the equipment on board of these vessels or plants,

• vehicles and the associated trailers that areexclusively intended for the transportation of people by air, road, rail, or water, andtransportation means designed for the transport of goods by air, public road andrailway systems, or water. Vehicles intendedfor use in potentially explosive atmospheresare not excluded and,

• possibly, products for military purposes, if thisis deemed necessary by any of the memberstates of the European Union.


The German interests will be represented by theGerman Institute for Standardizaton (DIN) andthe German Electrotechnical Commission (DKE).A list of the harmonized Standards to Directive94/9/EC can be found in Annex 4.

Groups and categories of apparatusApparatus is subdivided into groups and cate-gories:Apparatus Group I applies to apparatus formining operations above ground and underground that may be endangered by methanegas and/or combustible dusts.Apparatus Group II applies to apparatus foruse in all other areas that can be subject tothe hazard of an explosive atmosphere. The apparatus group I is subdivided into theCategories M1 and M2:

Essential safety requirementsA product is considered to be safe if, when it isused as directed, the essential safety and healthrequirements for the design and construction ofapparatus and protective systems according tothe directive are fulfilled. With regard to associated equipment, the basicsafety requirements only apply inasmuch as theyare necessary for a safe and reliable functioningand handling of this equipment in order toensure the explosion protection.

In order to make it easier to furnish proof that apiece of apparatus or a protective system con-forms to these requirements, uniform standardshave to be established on a European level. Thisapplies, in particular, to the non-electrical field ofexplosion protection. In the past standards onlyexisted for electrical apparatus in Europe. Thesestandards, if not already in existence, shalldescribe the conception, design and testing ofapparatus and devices. If standards are publis-hed by the European Commission in the officialgazette of the European Communities as assig-ned to a given directive, they are valid as so-cal-led „harmonized standards”. Compliance withthese standards ensures that a product con-forms to the basic requirements of Directive94/9/EC (so called „presumption principle”).These standards will be drawn up by the Euro-pean Standardization Committee (CEN) and theEuropean Committee for Electrotechnical Stan-dardization (CENELEC).

Group II apparatus with potential ignition source

Apparatus Category 1 Apparatus Category 2 Apparatus Category 3

Electricalapparatus

yes no

Motorwith internalcombustion

EC-Type Examination

Documentationfrom a notified body

Documentationfrom manufacturer

Essential safety and health requirements

Internal production control

yes

no


Category Apparatus Group II

1 The apparatus is intended for use in areas in which an explosiveatmosphere is present continuously or for long periods or fre-quently.Even if apparatus failures only occur infrequently, the apparatus mustensure the required degree of safety and feature such explosion pro-tection measures that• if one constructional protective measure fails, at least one other

independent constructional protective measure ensures the required degree of safety, or

• if two independent faults occur in combination, the required degree of safety is still ensured.

2 The apparatus is intended for use in areas in which an explosiveatmosphere occurs occasionally.Even in the case of frequent apparatus failures or faulty conditions thatare normally to be expected, the constructional explosion protectionmeasures ensure the required degree of safety.

3 The apparatus is intended for use in areas in which no occurrence ofan explosive atmosphere due to gases, vapours, mists or whirled-updust is to be expected. If, however, it occurs, then in all probabilityonly rarely or for a short period.During normal operation the apparatus ensures the required degree ofsafety.

Apparatus Group II is subdivided into the Categories 1, 2 and 3:

Category Apparatus Group I

M 1 The apparatus must continue to work even in the event of infrequent failures coinciding with an existing explosive atmosphere and must fea-ture such protective measures against explosion that• if one constructional protective measure fails, at least one other

independent constructional measure will ensure the required safety, or

• if two independent faults occur in combination, the required safety is still ensured.

M 2 If an explosive atmosphere occurs, it must be possible to switch off the apparatus. The constructional explosion-protection measures ensure the requireddegree of safety during normal operation, even under severe operatingconditions and, in particular, in cases of rough handling and changingenvironmental influences.

Group IIII 1G Category 1 (Zone 0 apparatus) (G = gases, vapours, mists)



Group IIII 1D Category 1 (Zone 20 apparatus) (D = dust)




Apparatus, protective systems or devices areregarded as unsafe if, when used for their inten-ded purpose, they represent an imminent dan-ger to the safety of people, domestic animals orgoods.

The member state is required to notify the com-mission of the European Union of such measu-res and to give the reasons for its decision. Thecommission will immediately contact the com-panies concerned and inform all member statesif these measures has are justified. If the fault is the result of a standard, a commit-tee will deal with it. Great importance is attachedto the uniformity of the practical implementation.The standing committee will review questionsrelating to the application of this directive.

MarkingEach piece of apparatus and each protectivesystem must be marked in a clear and indeliblemanner with the following minimum data: • manufacturer”s name and address • CE marking• designation of the series and of the type• serial number, when required• the year of construction• the community marking for explosion-

protected apparatus in accordance with the directive 76/117/EEC in conjunction with the marking relating to the category

• the letter ”G” for apparatus group II for areasin which explosive mixtures of gas, vapour or mist with air mixtures are presentand/or the letter ”D” for areas where anexplosive atmosphere can form due to dust.

In addition and where required, any details thatare indispensable for the safety of operation alsohave to be affixed.

Provisional arrangementsFrom 1.3.1996, the date on which the directivefirst became applicable, to the completion ofharmonization on 1.7.2003 there was a transitio-nal period during which the old regulations andthe new directive could be applied parallel toeach other. This long transition period facilitatedthe implementation of the new quality assurancesystem according to the requirements of thedirective for the manufacturers. The apparatusmust be marked clearly so that the user can tellwhether the ”old” or the ”new” directive wasapplied.

Putting into circulation and commissioning of productsThe member states must not forbid, restrict orimpede the putting into circulation and commis-sioning of apparatus, protective systems anddevices that conform to the terms of this direc-tive. Similarly, the putting into circulation of com-ponents covered by a certificate of conformityshall not be forbidden, restricted or impeded ifthey are to be built into a piece of equipment ora protective system in line with this directive.

The EU member states assume conformity withthis directive and with the conformity asses-sment procedures if the apparatus, protectivesystems and devices are accompanied by theEC Certificate of Conformity and if the productsare provided with the CE mark. Products that do not yet meet the requirementsof this directive may be displayed at exhibitions,fairs and demonstrations, if a visible label clearlypoints to the fact that it will not be possible topurchase the product until compliance with thedirective has been ensured.

Procedure in the event of unsafe productsShould a member state discover that any appa-ratus, protective systems or devices with CEmark are unsafe, it can withdraw these from themarket and forbid their being put into circulationor commissioning, or restrict their free circula-tion.

Marking examples:


CE marking

Products that fall within the scope of givendirectives must be provided with the CE markingby the manufacturer. This refers to products thatare covered by the directives according to thenew concept, that include requirements relatingto the technical properties of products. These EC directives constitute binding regulati-ons of the ”European Union”. That means thatthe compliance with these requirements is thecondition for marketing the products in Europe.When a product is provided with the CE mark,the conformity of the product with the relevantbasic requirements of all directives applicableto the products is confirmed. The marking is,therefore, an imperative requirement for the put-ting into circulation of the products within theCommunity, as well as in the country of origin.

The CE marking is only meant as evidence ofthe conformity with the directives for the supervi-sing authorities. It is, however, often mistaken asa quality mark and is, therefore, also requestedwithout a legal basis by the users.

The following directives are of special impor-tance for electrical apparatus:

• Directive 73/23/EEC Electrical apparatus for use within defined voltage limits

• Directive 89/336/EEC Electromagnetic compatibility

• Directive 89/392/EEC Safety of machinery

• Directive 91/263/EEC Telecommunication equipment

• Directive 94/9/EC Apparatus and protective systems for use inpotentially explosive atmospheres

When assessing which directives must beapplied to explosion-protected apparatus,it is necessary to differentiate between whetherthese directives are to be applied generally oronly to certain products.

• Directive 73/23/EECThis directive does not apply to ”Electricalapparatus for use in explosive atmospheres” (Exclusion as per Annex II of the directive)

• Directive 89/336/EECThis directive is to be applied to any productsthat may cause electromagnetic interferencesor the operation of which may be impaired bysuch interferences

• Directive 89/392/EECArticle 1, clauses 4 and 5 of the directiveclearly state that this directive is not to beapplied to explosion-protected electrical apparatus

• Directive 91/263/EECThis directive only applies to ”Electrical appa-ratus for use in explosive atmospheres” to avery limited extent. (Products for connection to the public tele-communication network)

• Directive 94/9/ECThis directive is to be applied to all products(including non-electric products) for use in apotentially explosive atmosphere

In addition to marking products with the CEmark, the manufacturer must issue a declara-tion of conformity for the product. This decla-ration of conformity must clearly state

which directive was applied and accordingto which standards the tests were carriedout.

At present, due to the fact that the various direc-tives came into force at different times and tran-sitional periods have been determined, thedeclaration of conformity is the only means toclearly discern which directive was taken as abasis for the CE marking (e. g. directive94/9/EC, applicable as of: March 1st, 1996;obligatory application as of: July 1st, 2003).

As explained in the first paragraph, this allapplies to directives according to the new con-cept. Unlike for many other products, directivesfor explosion-protected apparatus already exi-sted at a very early date. Thus, the Europeaninterstate market had already been establishedfor these products.

Directives 76/117/EEC; 79/196/EEC;82/130/EEC

These directives defined as the distinctivemark for the putting into circulation of explosion-protected apparatus within the whole commu-nity.

Type label according to new ATEX directive 94/9/EC

PTB Nr. Ex-92.C.1801 X

Type label according to previous directive

eLLK 92036/36CEAG Sicherheitstechnik GmbH

EEx ed IIC T4 110-254 V 50-60 Hz

Lampe: G13-IEC-1305-2 110-230 V DC

Ser. Nr.: D189115 Tu ≤ 50 °C


Conformity assessment procedure

Apparatus Group I and II I and II I and II II

Category M 1 and 1 M 2 and 2 M 2 and 2 3

Field of • any apparatus • electrical apparatus • other apparatus • any apparatus application • if applicable • if applicable, • components (*) • safety and control

safety and safety and devicescontrol devices control devices • components (*)

• components (*) • components (*) • independent protective systems • I.C. engines

Combination of EC type sample EC type sample Internal production Internal productionprocedures acc. test to Annex III test to Annex III control acc. to control acc. toIto Annexes plus quality plus quality Annex VIII Annex VIIIIII to IX ass. of production ass. of product plus submitting of

acc. to Annex IV acc. to Annex VIII technical documents or inspection of or conformity with to the designated products acc. to Annex V design IV test lab

Alternative: Individual EC test acc. to Annex IX

(*) Components without CE mark

Conformity assessment proceduresfor apparatus according to Directive 94/9/ECDepending upon the conformity assessmentprocedure to be applied, a notified body can beactive during the design and engineering phase,during the production phase or during both pha-ses. The applicable evaluation procedure is laiddown in the directive 94/9/EC in relation to theproduct, the apparatus group and the apparatuscategory.

Apparatus Groups I and II, ApparatusCategories M1 and 1In order to be permitted to affix the CE markingto his product, the manufacturer must arrangefor the following procedures to be carried out:

• EC-type examination by a notified bodyand

• either an inspection of the quality assu-rance for the production process or

• an inspection of the products.

Apparatus Groups I and II, ApparatusCategories M2 and 2With internal combustion motors and electricalapparatus, in order to be permitted to affix theCE marking on the product, the manufacturermust arrange for the following procedures to becarried out and/or ensure the following measu-res:

• EC-type examination by a notified bodyand

• either guarantee of constructional confor-mity or

• verification of the required quality level bymeans of the quality assurance procedurefor the products.

The internal production control procedure shallbe applied for all other apparatus in thesegroups and categories.

Apparatus Group II, Apparatus Category 3In order to be permitted to affix the CE markingto the product, the manufacturer shall apply theinternal production control procedure.

The EC declaration of conformity must be inclu-ded with all products or batches of identical pro-ducts that are put into circulation. This does notapply to the report issued by the notified bodyas part of the inspection of the quality assurancesystem of the manufacturer or for the EC-typeexamination certificate.


The Equipment Safety Law(GSG)

As of January 1, 1993 electrical apparatus foruse in hazardous areas is covered by the equip-ment safety law. Untill then, the requirements forthe qualification of equipment were based onthe Factory Act (GewO), the statutory regulati-ons (RVO) and the Equipment Safety Law. Thissplit responsibilty has been eliminated.

Now all measures relating to the puttinginto circulation of technical equipment arecombined in the Equipment Safety Law. These measures serve for the protection ofemployees and consumers in accordance withthe harmonized laws in the European Union.

If, however, you look for ”hazardous areas” inthe equipment safety law, you will not find them.Instead it refers to ”installations requiring super-vision”. These also include ”electrical installati-ons in particularly hazardous locations”.

The equipment safety law now makes it possibleto enforce the safety requirements for installationsand parts of these requiring supervision upon themanufacturers and importers. Moreover, it is noweasier to implement EC directives relating to theputting into circulation of apparatus.

Decree concerning the puttinginto circulation of apparatusand protective systems for usein potentially explosive atmos-pheres – explosion protectiondecree (ExVO)

§1 Scope §2 Definitions§3 Safety requirements§4 Conditions for putting into circulation§5 CE conformity marking§6 Breaches of the regulations§7 Provisional regulations

The decree concerning explosion protectiondirectly converts the directive 94/4/EC intonational law. It applies to all apparatus, protec-tive systems, safety and control devices for usein, and for, potentially explosive atmospheres.The range of application for such apparatus(including non-electrical apparatus) applies toapparatus that features an inherent potentialignition source and can cause an explosion.Such apparatus, protective systems and devicesmay only be put into circulation if they fulfil therequirements of the directive 94/9/EC. The legis-lative body garanted a transition period up toJune 30, 2003. Until this time apparatus couldbe put into circulation according to the law fromMarch 23, 1994.


Directive 1999/92/EC ofthe European Parliamentand Council dated December 16, 1999

Structure of Directive199/92/EC

Ruling part

Section Article HeadingI 1-2 General requirementsII 3-9 Duties of employer

3 Prevention of and protec-tion against explosions

4 Assessment of the explo-sion risks

5 General obligations6 Coordination obligations7 Areas with explosive

atmospheres8 Explosion protection

document9 Special regulations relating

to working materials andplaces of work

III 10-15 Other requirements

AnnexesI Classification of areas in which explo-

sive atmospheres can be present1. Areas in which explosive atmospheres

can be present 2. Classification of potentially explosive

atmospheres

II A Minimum requirements for theimprovement of the safety andhealth protection of employeeswho could be endangered byexplosive atmospheres

1. Organizational measures2. Explosion protection measures

B Criteria for the selection of appa-ratus and protective systems

III Warning signs for marking areasin which explosive atmospherescan occur

The aim of the European directive is to lay downminimum requirements for the improvement ofthe health protection and safety of employeeswho could be endangered by explosive atmos-pheres. The national legislative bodies are obli-ged to implement these requirements, but mayalso lay down additional measures on a nationalbasis.

Scope:The scope of application covers the areas inwhich employees can be endangered by explo-sive atmospheres. Here an explosive atmos-phere is defined as being a mixture of flammablegases, vapours, mists or dusts with air.

Reductions of and assessment of explosionrisksIt is the duty of the employer to carry out mea-sures according to the following order of prece-dence:1. Prevention of explosive atmospheres,

where possible by the substitution of materi-als.

2. Prevention of the ignition of explosiveatmospheres.

3. Harmful effects to a minimum.This concept is already known in Germany dueto the explosion protection directives of theemployers” liability insurance association and ithas been put into practice for many years. Thenew aspect of this directive is the systematicmethod according to which the measures arelaid down and documented.After assessment of all the remaining explosionrisks, whereby the interaction of installations, thematerials being used, the processes and theirpossible interactions were taken into considera-tion, measures for the safety of employees atwork must be laid down to ensure their healthand safety at all times. Here special require-ments are imposed regarding the coordinationduties of the employer at the place of work.

Zone classification

The areas in which explosive atmospheres canoccur must be subdivided into zones accordingto Annex I of the directive. Here gases anddusts are each divided into three zones accor-ding to the probability of their occurrence.

Flammable gases, vapours or mists:

Zone 0An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists is present for long periods orfrequently.

Zone 1An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists can form occasionally undernormal operating conditions.

Zone 2An area in which an explosive atmosphere com-prising a mixture of air with flammable gases,vapours or mists does not normally occur oronly occurs for a short period under normaloperating conditions.


Combustible dusts:

Zone 20An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair can be present for long periods or fre-quently.

Zone 21An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair can form occasionally under normal ope-rating conditions.

Zone 22An area in which an explosive atmosphere in theform of a cloud of combustible dust found in theair normally does not occur or occurs for ashort period only under normal operating con-ditions.

With combustible dusts it is also necessary toconsider the layers, deposits and accumulationsas a source for possible explosive atmospheres.Normal operation is understood as being wheninstallations are used according to the specifiedparameters.

Explosion protection document

After the employer has classified the zones andmarked these areas in accordance with Annex IIIof the directive, he then has to issue the explo-sion protection document. First all the ascertai-ned explosion risks and the measures taken (pri-mary explosion protection) are documentedhere, together with the zone classification. Thisis followed by the documentation of the measu-res according to Annex IIA relating to the fulfil-ment of the minimum requirements. This inclu-des the areas of installations located in the non-potentially hazardous atmospheres that arenecessary for the safety of the potentially explo-sive atmosphere.

Annex II AMinimum requirements for the improvement ofthe safety and health protection of employeeswho can be endangered by explosive atmos-pheres.

1. Organizational measures- Appropriate instruction of employees- Written instructions and work release

notes• If necessary, written instructions for work

assignment• Work release system for hazardous tasks• Work release by authorized person

2. Explosion protection measures- Rendering any escaped Ex-atmosphere

harmless- Design according to the highest risk

potential- Avoidance of all ignition hazards

(e.g. static charge of persons)- Taking into operation if authorized in the

explosion document - Installation and operation according to

lowest explosion risk- If necessary, warning of Ex-atmosphere

(visual/acoustical)

- Provision of escape facilities- Initial inspection by qualified person- Measures for risk assessment

• Hazards due to power failures• Manual operation of apparatus and protective

systems• Safe reduction of stored energy

Annex II BCriteria for the selection of apparatus and pro-tective systems

Unless otherwise specified in the explosion pro-tection document taking into account the riskevaluation, apparatus and protective systemsare selected in accordance with Directive94/9/EC.

Zone Category0 or 20 11 or 21 1 or 22 or 22 1, 2 or 3

Annex IIIWarning sign for marking areas in which explo-sive atmospheres can occur.

In addition to these measures, it is necessary todocument how the place of work and the wor-king materials, including the warning sign, aresafely designed, serviced and operated. Themeasures for the safe use of working materialsare also to be documented in accordance withDirective 89/655/EEC.Before work is commenced, this documentmust be drawn up and revised in such a waythat any significant changes, extensions or rear-rangements of the place of work, the workingmaterials or the work process are taken intoconsideration.

Special regulations for working materials andplaces of work- up to 30.06.03 working materials

(Annex ll A)- from 01.07.03 new working materials

(Annex ll A+B)- from 01.07.03 new places of work (Annex ll)- up to 30.06.03 rearrange old places of work- from 01.07.03 rearrange places of work in the

event of changes

Directive 1999/9/92 EC applies the dates anddeadlines stated above to regulate the imposingof the minimum requirements for work equip-ment and places of work for new installations,as well as for the adaptation of existing installati-ons in which potentially explosive atmospherescan occur. As, in this case, changes are permit-ted during the conversion of this directive intothe national law of the member states, the res-pective national rules and regulations shall beobserved. It is necessary to note that, depen-ding upon the respective situation, various timelimits can apply.


With this decree, that came into force onOctober 3, 2002, among other things, Direc-tive 1999/92/EC was converted into Germanlaw. Within the scope of the interim provisionsin the BetrSichV, it replaces the ElexV for thefield of explosion protection.

Table of contentsSection 1

General regulations§ 1 Scope of application§ 2 Definitions

Section 2§ 3 Assessment of degree of hazard§ 4 Requirements relating to the provision

and use of work equipment§ 5 Potentially explosive atmospheres§ 6 Explosion protection document § 7 Requirements relating to the quality of

work equipment§ 8 Further protective measures§ 9 Information and instruction§ 10 Testing of work equipment§ 11 Records

Section 3Special regulations for installations

requiring supervision§ 12 Operations§ 13 Required permits§ 14 Testing before putting into operation§ 15 Recurrent tests§ 16 Prescribed special tests§ 17 Testing of special pressure apparatus§ 18 Accident and damage reports§ 19 Test certificates§ 20 Notice of defects§ 21 Approved supervisory authorities§ 22 Supervisory authorities for installations

requiring supervision owned by theFederal Government

§ 23 Operation of portable pressure apparatuswithin the boundaries of an industrialplant

Section 4Joint regulations, concluding provisions

§ 24 Commission for operational safety § 25 Breaches of regulations§ 26 Punishable offences§ 27 Provisional rulings

Annex 1: Minimum requirements for workequipment in acc. with § 7, Section1, No. 2

Annex 2: Minimum requirements for theimprovement of the safety andhealth protection of employeeswhen using work equipment

Annex 3: Zone classification of potentiallyexplosive atmospheres

Annex 4: A:Minimum requirements for theimprovement of the safety andhealth protection of employeeswho could be endangered bypotentially explosive atmospheres

B:Criteria for the selection of equip-ment and protective systems

Annex 5: Testing of special pressure appara-tus according to § 17

As this table of contents shows, the BetrSichVdoes not only lay down rules for the field ofexplosion protection, but it also replaces aseries of other decrees, e.g. the decree onflammable liquids or the pressure tanksdecree. Due to the large scope of the rulingsof the decree, it is not necessarily easy to findthe individual provisions of the EC Directivediscussed in the previous section immediately.However, they have all been incorporated inaccordance with the European law. The Ger-man legislator made avail of the aforementio-ned possibility to expand on the minimumrequirements of the directive during conver-sion into national law, inasmuch as the Ger-man law includes clearly defined requirementsfor testing apparatus before putting it intooperation for the first time, for recurrent testsand testing after apparatus repairs.

Decree on health andsafety protection relatingto the provision of workequipment and the usethereof during work,safety during the opera-tion of installations requi-ring supervision and theorganisation of operatio-nal safety provisions (Ope-rational Safety Decree –BetrSichV)


Electrical apparatus foruse in potentially explosiveatmospheres

There is a certain interrelation between the limit-ing gap widths and the ratio of minimum ignitioncurrent. In order to be able to classify gases andvapours to meet the requirements of explosionprotection, it is, therefore, sufficient to defineonly one of the two properties for most of theindustrially employed gas/air and vapour/air mix-tures. Annex A to VDE 0170/0171/part 1/3.94 -DIN EN 50 014 states the classification of anumber of industrially important gases andvapours according to their limiting gap widthand their minimum ignition current.

PrinciplesDivision into explosion groupsIt would not be economical to construct allexplosion-protected electrical apparatus to meetthe most stringent requirements with regard toignition temperature, explosive force and ignitioncapability of the gases. For this reason, electricalapparatus is divided into explosion groups andtemperature classes. Group I: encompasses electrical apparatus

for underground mines that are sus-ceptible to the hazard of firedamp,e.g. coal mines

Group II: encompasses electrical apparatusfor all other hazardous areas

Sub-division of the explosion groupsaccording to the explosive force andminimum igniting currentA sub-division into A, B and C is prescribed forsome types of protection for Group II electricalapparatus. For flameproof enclosures it is basedon the maximum experimental safe gap (MESG),and for intrinsically safe apparatus on the mini-mum igniting current (MIC).

Maximum experimental safe gap(MESG)In the case of electrical apparatus in which arcsor sparks occur during normal operation, anexplosive atmosphere that has penetrated intothe enclosure can be ignited. However, the pro-pagation of an already initiated ignition from wit-hin the enclosure to the surrounding atmos-phere can be prevented if the flame is forced topass through narrow gaps. As it passes throughthe gap, heat is taken away from the flame andthe temperature is reduced to such a degreethat combustion no longer takes place and theflame is extinguished. With electrical apparatusin the type of protection ”Flameproof enclosure”the classification of the gases and vapoursbased on the maximum experimental safe gap(MESG) are carried out in testing vessels with agap length of 25 mm. The testing vessel descri-bed in the IEC publication 60079-1 A must beused as the standardization method for determi-ning the MESG.

Minimum ignition current (MIC)As far as intrinsically safe electrical apparatusare concerned, gases and vapours are classifiedaccording to their ratio of minimum ignition cur-rent. In order to ignite an explosive atmosphere,the ignition spark must contain a minimumenergy content. The necessary minimum energycontent is a specific property of the ignitablegases and vapours. A criterion for this is theratio of the minimum ignition current (MIC) to theminimum ignition current of laboratory methane.The MIC is determined according to a standardi-zed method and must be carried out with appa-ratus as defined in EN 50 020 annex B.

Explosion Limiting gap Ratio ofgroups width minimum

in mm ignition current

II A > 0,9 > 0,8

II B 0,5 to 0,9 0,45 to 0,8

II C < 0,5 < 0,45


Ignition temperature and temperatureclasses

The maximum surface temperature of the elec-trical apparatus must not reach the ignition tem-perature of the potentially explosive atmosphere.The ignition temperature of a flammable sub-stance is determined by means of a test appara-tus. It is the lowest temperature on a heated wallat which the flammable substance will just aboutignite in a mixture with air. The ignition tempera-ture of liquids and gases is determined accor-ding to the method defined in DIN 51 794. Thedetermination of the ignition temperature ofcombustible dusts is specified in the IEC publi-cation IEC 61241-2-1.The ignition temperatures of the different mixtu-res vary considerably. Whereas a mixture of airwith town gas will only ignite at 560 °C, a mixture of air and petrol will already ignite at ca.250 °C.This classification makes it possible to take eco-nomical aspects into account for the design ofthe electrical apparatus. The requirements rela-ting to the construction increase with the ascen-ding order of the letters marking the explosiongroups. The requirements relating to the admis-sible temperature of the surfaces that come intocontact with the explosive atmosphere,(decrease in surface temperature), rise with theascending order of the numerals for the tempe-rature classes. It is, therefore, left to the manu-facturer to decide the requirements accordingto which he wants to design and be permitted tomark his explosion-protected electrical appara-tus. It goes without saying that apparatus thatfulfils the requirements of temperature class T3is also suitable for use in explosive atmospheresin the temperature classes T1 and T2.

Classification of maximum surface temperatureson group II electrical apparatus

Temperature Max. admiss. surface temperature Ignition temperatures of in-class of the apparatuses in °C flammable substances in °C

T 1 450 > 450

T 2 300 > 300 ≤ 450

T 3 200 > 200 ≤ 300

T 4 135 > 135 ≤ 200

T 5 100 > 100 ≤ 135

T 6 85 > 85 ≤ 100

Classification of gases and vapours in explosion groups and temperature classes

T 1 T 2 T 3 T 4 T 5 T 6

I Methane

II A Acetone Ethylalcohol Petrol AcetaldehydeEthane I-amyl acetate Diesel fuel EthyletherEthylacetate n-butane Aviation fuelAmmonia n-butylalcohol HeatingBenzol oilsAcetic acid n-hexaneCarbonmonoxideMethanolPropaneToluene

II B Town gas Ethylen(lamp gas)

II C Hydrogen Acetylene Carbondisulphide


Types of protection for explosion-protected apparatus

General requirements acc. toEN 50 014

According to the European standard DIN EN 50014 (VDE regulations 0170/0171/Part 1) explosion-protected apparatus can bedesigned to meet the requirements of varioustypes of protection. Here seven types of protec-tion based on different principles are taken intoconsideration.

Electrical apparatus for hazardous areas mustconform to the general terms of the Europeanstandard EN 50 014 and to the specific require-ments for the type of protection for which it isbuilt. Particularly harsh operating conditions, theeffects of moisture, high ambient temperaturesand other special stresses might possiblyrequire additional measures.Special requirements listed in the standard mustbe observed for enclosures made of plasticsand light alloys. Special requirements apply to: • locks and fixings,• bushings and connecting pieces,• cables and conduit entries

In accordance with the requirements of the stan-dards, electrical apparatus built to Europeanstandards must be subjected to a type test byan independent testing station and to a routinetest by the manufacturer. The type test esta-blishes whether the technical documents(description and drawings) and the test samplesare in conformity with the respective standards.The mechanical strength is verified by an impactand drop test.

Compliance with admissible surface and windingtemperatures is verified by measurements. Spe-cial tests are specified for• the surface resistance,• the verification of the thermal resistance of

plastic,• the thermal shock resistance of glass parts of

luminaires and inspection windows.

Explosion-protected electrical apparatus mustbe marked in a clearly visible position. Accordingto EN 50 014, it is not necessary to certify ormark apparatus where none of the values of 1.2 V, 0.1 A, 20 µJ or 25 mW is exceeded.

Explosive atmosphere Explosive atmosphere Explosive atmosphere

Oil immersion ”o” – EN 50 015 Pressurization ”p” – EN 50 016 Sand filling ”q” – EN 50 017


Generalrequirements


Flameproof enclosure ”d” – EN 50 0158 EN 50 014 Increased safety ”I” – EN 50 019

Explosiveatmosphere


”n”

Intrinsic safety ”I” – EN 50 020 Encapsulation ”m” – EN 50 028 ”n” – EN 50 021

Sandfilling

inert gas

Oil filling

Pottingcompund

Types of protection


Oil immersion ”o”EN 50 015/VDE 0170/0171, Part 2Definition: A type of protection for electrical appa-ratus where the complete electrical apparatus orparts of electrical apparatus are rendered safeby immersing them in oil, so that the explosiveatmosphere cannot come into contact with thepotential ignition source.With this type of protection, the ignition source isso deeply immersed in an oil-filled enclosure thata transmission of the flame to the area above theoil level is prevented. This requires that the ther-mal output fed to the oil, the thermal energy andthe resulting energy density be taken intoaccount.

This type of protection is chiefly applied to swit-chgear and transformers. With such switchgear,the switching arc is drawn in oil and does not,therefore, come into contact with the explosivemixture. Besides making sure that a sufficient oillevel is provided in any operating position of theswitchgear, the use of a suitable oil that must notdecompose as a result of the switching arc is ofspecial importance. In addition to this, care hasto be taken to ensure that the temperature of theswitchgear does not rise too high. An increasedoil temperature could, in turn, become an ignitionsource. The long term quality of the oil must alsobe monitored, as soot changes the properties ofthe oil.

Oil-immersed switchgear was widely used by thechemical industry for the local switching ofmotors. As a result of the transition to remotecontrols and an increase in the number ofinterlocks, it has lost much of its significance.Nowadays oil-immersed switches are only instal-led in exceptional cases. Moreover, the use of oil-immersed switches for portable equipment is notpermitted. They also require a lot more mainten-ance. Repairs are more difficult, because the oilbox has to be removed prior to starting. This isoften undesirable inside the work area.

Pressurization ”p”EN 50 016/VDE 0170/0171, Part 3The type of protection Pressurization preventsthe penetration of an explosive atmosphere intothe enclosure containing electrical apparatus.This is achieved by means of an inert gas insidethe enclosure that is maintained at a pressureabove that of the surrounding atmosphere. Theoverpressure of at least 0.5 mbar can be main-tained with or without continuous purging withinert gas. As a rule, air serves as an inert gas. Previouslythis type of protection was called separateventilation ”f”.There are two types of pressurization: • Pressurization with continuous purging• Pressurization with leakage compensation

The inert gas must enter into or exit the enclo-sure outside of the hazardous area. With bothtypes, the enclosure of the apparatus and all itsducts must be purged prior to operation by avolume of gas that equals the five-fold volume ofthe enclosure. During operation the overpres-sure must be monitored and, if the overpressuredrops, a warning signal given or the apparatusswitched off. Normally, a flow gauge is used in conjunctionwith a time lag relay to monitor the purging. Thetime lag relay starts running at the same time aspurging. As soon as the required volume of inertgas has flown through, the time lag relay relea-ses the switching-on of the apparatus that isbuilt into the enclosure. If the purging fails orthere is a drop in the overpressure during opera-tion, the flow gauge or a manometer closes acontact which switches off the apparatus orgives a warning signal.The encapsulation of the apparatus must con-form to a minimum degree of protection IP 40 toEN 60529. It must prevent the propagation offlames, sparks or ignitable particles to thepotentially explosive atmospheres.

Examples for pressurization ”p”• Electrical machinery with higher rating • Switch cabinets• Control panels• Switch rooms• Transformers• Measuring instruments• Resistor instruments• Liquid starters• Luminaires• Current and voltage transformers• Communication devices

Example of pressurized apparatus


Ex-floodlight for high pressure discharge lamps:

flameproof enclosure in combination with a terminal

compartment in type of protection ”increased safety”

Sand filling ”q”EN 50 017/VDE 0170/0171, Part 4With the type of protection Sand filling, theenclosure of an electrical apparatus is filled witha fine-grained filling material. This prevents thedevelopment of an arc inside the enclosure thatcould ignite the explosive atmosphere surroun-ding the enclosure. In addition to this, neither anignition caused by flames nor an ignition as aresult of increased temperatures on the enclo-sure surface should be possible.

With this type of protection the enclosure isgenerally filled with quartz sand that has to meetspecific requirements with regard to the grainsize, purity, moisture content and disruptivestrength. A filling material other than quartz ispermitted if it conforms to the requirements. Theenclosure must preferably be made of metal.Other materials are only permitted if theirmechanical and thermal properties have beensubjected to a test and described in detail. Inany case, the resistance to pressure must beverified by a static pressure test.

The built-in electrical components must be ade-quately insulated, irrespective of the insulatingeffect of the filling material. With naked live partsthere must be sufficient space between theparts and between the parts and the enclosurewall.

The filling material is compressed, whereby,depending on the built-in instruments and requi-rements, the layers of filling material must have aspecified thickness. A perforated metal sheetmay be laid in the filling as a screen to reducethe thickness of the layers.

Examples for sand filling ”q”:• capacitors• bell transformers• control circuits with hot or sparking parts• electronic apparatus

Flameproof enclosure ”d”EN 50 018/VDE 0170/0171, Part 5With this type of protection those parts that arecapable of igniting an explosive atmosphere arebuilt into a flameproof enclosure that withstandsthe explosion pressure if a flammable mixture isignited inside it. In this way a transmission of theexplosion to the explosive atmosphere surroun-ding the enclosure is prevented

The flameproof enclosure principle can be com-pared to a one-way street • an explosive atmosphere can penetrate into

the enclosure of the electrical apparatus,• but, in the event of an explosion inside the

enclosure, a transmission of the explosion tothe outside is prevented.

The flameproof enclosures generally featurejoints for the reduction of the high gas pressurethat is generated in the event of an explosion.These joints have two functions. On the onehand, the reduction of the gas pressure, and, onthe other hand, the cooling down of the tempe-rature of the explosion gas being releasedthrough the joint to such a degree that an explo-sive atmosphere surrounding the flameproofenclosure is not ignited.

A series of experiments was carried out todetermine the gap dimensions for each type ofexplosive so that the flammable atmospheresurrounding the atmosphere is not ignited.Information on the determination of the maxi-mum gap widths can be found in the section”Fundamental principles of explosion protec-tion”.

The type label of the flameproof apparatus mustshow the explosion group. Group II C apparatuscan also be operated in areas for the Groups II Band II A, and group II B in areas for Group II A.

The temperature class of apparatus indicatesthe permitted limiting temperature up to whichthe outer surfaces of such apparatus may rise.

The type of protection ”d” is often used formotors and switchgear. Very little heat is gene-rated in switchgear, so that the surface tempe-rature of the enclosure during operation is onlyslightly higher than the temperature of theatmosphere surrounding the apparatus. In gene-ral, the switchgear satisfies the requirements ofthe temperature classes T5 and T6 and, there-fore, also the requirements of the classes withhigher permissible temperatures.


By comparison, motors dissipate more heat,especially with higher outputs. In order not toexceed the permissible limiting temperature, itmay be necessary to lower the rated output of aflameproof motor as compared to that of a stan-dard motor. Oil and liquids that can form explosive mixtureswith air during decomposition must not, underany circumstances, be introduced into flame-proof apparatus.

Examples for the application of type ofprotection ”d”• Motors with sliprings and commutators• Three-phase squirrel cage motors • Switchgear with N/O and N/C contacts such

as motor protection switches, circuit breakers,air-break contactors

• Control units, plugs and sockets• Fusegear• Transformers• Measuring instruments• Current and voltage transformers• Resistors• Luminaires• Communication apparatus

Ex-distribution in type of protection ”increased

safety” with flameproof built-in components

Combined types of protectionUntil now it has been common practice in Ger-many to combine a flameproof enclosure with aconnection box in the type of protection ”increa-sed safety”. Such a combination is used forluminaires and motors.

This has the advantage that the installer doesnot have to open the flameproof enclosure whencarrying out installation maintenance. In compli-ance with the degree of protection IP 54, thecable can be lead into the ”increased safety”type connection box.


Increased safety ”e”EN 50 019/VDE 0170/0171, Part 6The protection category ”increased safety” isused for electrical aparatus that, under normaloperating conditions, does not form an ignitionsource. Consequently, apparatus that producesarcs or sparks in the course of normal operationor apparatus that generates ”excessive” heat isnot suitable for this type of protection. There-fore, this type of protection is not used for switchgear, pushbuttons and slip ring motors.

In particular, this type of protection has provedeconomical and practical for electrical apparatussuch as terminal boxes, junction boxes, three-phase squirrel cage motors, luminaires, solenoidvalves and transformers.

It must not be possible for leakage currents orarcs as a result of external influences, such aswater and foreign matter, to develop. Enclosu-res that contain uninsulated live parts must fulfila minimum degree of protection IP 54. Thedegree of protection IP44 is sufficient for enclo-sures that contain insulated parts only. If rotatingelectrical machines that are installed in cleanrooms and are regularly controlled by qualifiedpersonnel, IP 20 is sufficient for group II. Therestricted operation range of use is stipulated onthe machine. All enclosures are submitted to amechanical impact test as part of the type test.

It is possible to establish a flexible lead connec-tion by means of a trumpet-shaped cablegland. To eliminate the possibility of damageduring normal operation, all parts of the cableentry must comply with the mechanical impactrequirements. Connection terminals must besafeguarded against self-loosening and mustprovide sufficient contact pressure.

The increased safety is ensured by means of theimproved insulation of live parts and by largerclearances and creepage distances comparedto standard apparatus. With this type of protec-tion the limiting temperature also applies to allsurfaces inside the enclosure.

All insulating material is subject to naturalageing. In order to prolong the service life of theinsulating materials of windings, compared tothe windings in standard apparatus, the limitingtemperature is decreased. This reduces thedanger of damage to the windings as a result ofearth leakages or interturn short-circuits.

The following table lists the limiting temperaturesfor insulated windings in apparatus in the type ofprotection ”increased safety”.

Ex-terminal box in the type of protection

”increased safety”

Limiting temperatures for Measuring Insulation classinsulated windings procedure A E B F H

All windings, except insulated R* °C 90 105 110 130 155single-layer windings in nominal operation

T* °C 80 95 100 115 135

Single-layer insulated windings R* °C 95 110 120 130 155in nominal operation

T* °C 95 110 120 130 155

Limiting temperature at the end of time tE R* °C 160 175 185 210 235

*) R = resistance measuring procedure, T = thermometer measuring procedure


Protective devices for windings shall ensure thatonly the reduced limiting temperature valuesspecified in the table are reached.

Motors are used with overcurrent protectiondevices that are released in the event of difficultstarting conditions or of a failure. After severalhours of operation at nominal rating a motor rea-ches its continuous operating temperature. If therotor stalls due to a malfunction and the supplyof voltage is not disconnected, the motor drawsan increased current, the starting current IA, thatis the rated current IN many times over. If themotor is not switched off, it reaches the limitingtemperature after the time tE. The time tEdepends on the starting current ratio IA/IN.

The overcurrent protection device must switchoff the motor before it reaches the limiting tem-perature, i. e. within the time tE. The protectiondevice fulfils the same function when the motoris stalled, irrespective of whether the motor iswarm or cold.

If the rotor and the stator take different times toheat up, the shorter time will be taken as tE. Thetype label and the certificate of approval of themotor state the time tE and the ratio of the star-ting current IA to rated current IN.

The protection devices must keep the specifiedtripping times within a tolerance of +/-20 %.

Fig. 3 shows the characteristic of a thermal relaywith an example for checking. The relay, that isset at the rated current of the motor, triggers at7.4 times the rated current within a period that isshorter than the time tE. The relay is suitable forprotecting the motor.

The protection devices must also switch off themotor in the event of the failure of one phase.Here, current-dependent thermal overcurrentrelays or circuit breakers can be used if, forexample, they are equipped with a phase failureprotection to VDE 0660.

With motors in connection the protectivedevice must fulfil the following conditions. In theseized motor and with phase failure, the trippingtime shall be tested with 0.87 times the motorstarting current, whereby the tripping time mustbe within the time tE. This test is necessary todetect the increased temperature caused by theunequal loads of the windings, as it cannot beidentified by means of the mains-current con-sumption.

In general, electrical motors of the type ”increa-sed safety” may only be used in continuousoperation and for normal, seldom recurringstarts so as to prevent that the rises in tempera-ture occurring during the start exceed the per-missible limiting temperatures. In the case ofmotors in the low-voltage range, thermal motor

protection has the advantage that, due to itstemperature gauges with positive temperaturecoefficient embedded in the windings, the rise intemperature during the start-up period in swit-ching operation is monitored.

Examples for increased safety ”e”• Three-phase or single-phase rotor with cage

rotor• Transformers• Current and voltage transformers• Measuring instruments• Ballasts for luminaires• Luminaires• Resistors• Liquid starters• Accumulators• Communication apparatus• Connection boxes for any electrical apparatus

Encapsulation ”m”EN 50 028/VDE 0170/0171, Part 9With the type of protection encapsulation ”m”,those parts that are capable of igniting an explo-sive atmosphere are embedded in a compoundwith sufficient resistance to environmental influ-ences. The explosive atmosphere can neither beignited by sparking nor by heating, both ofwhich may occur within the encapsulation.

Duromers, thermoplastics and elastomers withand without fillers and/or other additivies may beused as compounds. The properties of the com-pound must fulfil the requirements of EN 50 028(e.g. temperature index T1 to IEC 60216-1) wit-hin the given temperature range.The selection of the compound for a specificapplication depends on the function that thecompound has to fulfil in the apparatus. Theencapsulation must ensure the efficiency of thetype of protection, even in the event of permissi-ble overloads and certain internal fault conditi-ons.

The compound may contain hollow spaces forthe accommodation of components such asrelays, transistors etc. up to a volume of 100cm3.

If the compound in encapsulated apparatus isdirectly exposed to the surroundings, the com-pound must comply with the requirements of EN 50 014 for non-metallic materials.

Examples for encapsulation ”m”• Relays, signal and control units• Transistors, sensors• Film resistors, indicators• Ballasts (conventional type)• Electronic ballasts • Subfractional horsepower motors• Solenoid valves

3 4 5 6 7 8 9 10

2

5

10

20

40

t E m

in

IA / IN

s

Fig. 1: Minimum values for the time tE

0

A

B

C

1

θ in

°C

t (1) in h t (2) in s

2

tE

3 4 5 6 7,4 8

2

5

10

20

40

t in

s

IA /IN

11

1

Fig. 2: Explanation how to calculate the time tEA max. permissible ambient temperatureB temperature in rated operationC limiting temperaturet timeθ temperature1 heating-up in rated operation2 heating-up with motor being stalled

Fig. 3: Tripping characteristic of the thermal relay

from cold

Time tE of the motor to be protected 11 s

IA/IN of the motor to be protected 7.4


Intrinsic safety ”i”

EN 50 020/VDE 0170/0171, Part 7The most recent type of protection againstexplosion hazards by electrical apparatus andinstallations is called ”intrinsic safety”. The mostcommon types of protection were conceived forelectrical power engineering applications. As aresult of increasing automation within hazardousareas, there has been an ever increasingdemand for explosion-protected measurementand control devices. Intrinsically safe circuitsonly have a low energy content, that is not suffi-cient to ignite an explosive mixture. Thus, forthese circuits, the creation of a type of protec-tion that makes use of this physical principle isthe obvious solution.

Technical terms

Intrinsically safe circuitUnlike all the other types of explosion protection,where the explosion protection is always relatedto the individual apparatus, the type of protec-tion ”Intrinsic safety” takes the complete circuitinto account.

Definition of an ”Intrinsically safe circuit”An intrinsically safe circuit is a circuit in which nospark or thermal effect will be produced that iscapable of causing the ignition of a definedexplosive atmosphere, whereby the test conditi-ons for normal operation and defined fault con-ditions specified in the standard are to be takeninto account.

Intrinsically safe electrical apparatusDepending on the design and purpose, appara-tus in the type of protection ”intrinsic safety” issubdivided into ”intrinsically safe” and ”associa-ted” electrical apparatus.

Intrinsically safe electrical apparatusIntrinsically safe electrical apparatus is electricalapparatus in which all the circuits are intrinsicallysafe.Distinction is made between the following typesof intrinsically safe apparatus:– Active intrinsically safe apparatus– Passive intrinsically safe apparatus without

stored energy– Passive intrinsically safe apparatus with stored

energy

Associated electrical apparatusAssociated electrical apparatus is apparatus inwhich not all circuits are intrinsically safe, butwhich contains circuits that can affect the safetyof the intrinsically safe circuits to which it isconnected. Associated apparatus can be:– either electrical apparatus conforming to

another type of protection stated in the”General requirements” of the European standard 50 014, on account of which it is suitable for use in the respective potentiallyexplosive atmospheres;

– or electrical apparatus that does not conformto any type of protection and, therefore, may not be used in potentially explosiveatmospheres.

Fundamental data

Minimum ignition energy A minimum ignition energy is required to ignitean explosive mixture. As the result of an externalignition source, for example an electric spark, ahigh temperature is generated locally in a smallvolume area of an explosive atmosphere, resul-ting in combustion. The heat produced by thespark and the ensuing combustion heats theneighbouring layers, while, at the same time,due to heat conduction, energy is dissipated tothe outside. If the dissipated heat is higher thanthe heat supplied and generated, a propagationof the combustion to neighbouring volume areasis not possible.

Only if the amount of energy supplied by theexternal ignition source is sufficient for the tem-perature of the neighbouring layers to rise abovetheir ignition temperature, the combustion isautomatically propagated and an explosionresults.

The type of protection ”intrinsic safety” makesuse of this fundamental knowledge. The electri-cal values of a circuit are limited to such adegree that the minimum ignition energy requi-red for an ignition is not reached.

Definition of the minimum ignitionenergyThe minimum ignition energy of a gas/air or avapour/air mixture is the lowest possible electrical energy occurring when a capacitor isdischarged that is still capable of igniting themost volatile ignitable mixture of gas/air orvapour/air at atmospheric pressure and20 °C.

FB remote I/O for Zone 1

LB remote I/O Zone 2 in instrumantation compartment


Fig. 1:

Ohmic circuits

Minimum ignition current to

be applied for electrical

apparatus containing cad-

mium, zinc, magnesium or

aluminium

10 V 20 V 50 V 100 V 200 V 500 V10 mA

20 mA

50 mA

100 mA

200 mA

500 mA

1 A

2 A

5 A

II C

I

II AII B

Sub-division into groupsDepending on their minimum ignition energy,flammable substances are divided into thegroups I, IIA, IIB and IIC. The sub-division isidentical to that according to the ignition break-down capacity that is also decisive for to thetype of protection ”flameproof enclosure”. In thecase of intrinsically safe electrical apparatusgases and vapours are sub-divided on the basisof the ratio of their respective minimum ignitioncurrent (MIC) to the minimum ignition current oflaboratory methane.

Sub-division A ratio of the MIC > 0.8Sub-division B ratio of the MIC between

0.8 and 0.45Sub-division C ratio of the MIC < 0.45

Limiting ignition curves

The energy set free in an intrinsically safe circuitin the event of a failure must be limited to such adegree that the occurrence of an ignition isunfailingly prevented.The limiting ignition curves for the individualgroups are established with the aid of a standar-dized spark test apparatus.

As the probability of the ignition of a mixture alsodepends on the number of switchingoperations, according to EN 50020 at least1000 switching operations must be performed,whereby an ignition must not take place underany circumstances.

Depending on the design of the intrinsically safecircuit, the existence of stored energy has to betaken into account. If there are capacitances inthe intrinsically safe circuit, these are loadedonto the voltage of the circuit. The energy storedin the capacitor is 0.5 CU2 (C = capacitance, U = voltage). In the event of a short-circuit, theenergy stored in the capacitor is released inaddition to the energy supplied by the associa-ted apparatus.

The same conditions apply when there are induc-tances in the circuit. If there is a flow of currentthrough an inductance, the stored energy will be0.5 LI2 (L = inductance, I = current). This energy isreleased additionally in the event of an interrup-tion.For these reasons all three borderline cases, i. e.ohmic circuits, capacitive circuits and inductivecircuits have to be taken into consideration.The European standard EN 50 020 contains limiting ignition curves for these conditions.

Safety levels of intrinsically safe and associated electrical apparatus

Intrinsically safe electrical apparatus and intrinsi-cally safe components of associated electricalapparatus are divided into two safety levels, -ia- or -ib-.

Safety level -ia-If a single fault or any combination of two faultsoccurs during normal operation, the electricalapparatus of the category -ia- must not becapable of causing an ignition. Here the following safety factors have to betaken into consideration:Safety factor 1.5 during normal

operation and with one faultSafety factor 1.0 with two faults

Explosion Limiting gap Ratio ofgroups width minimum

in mm ignitingcurrent

II A > 0.9 > 0.8

II B 0.5 upto 0,9 0.45 upto 0.8

II C < 0.5 < 0.45


Fig. 2: Capacitive circuits

Minimum igniting voltages to be applied to group IIC

electrical apparatus. The curve marked Sn is only to

be applied to electrical apparatus not containing any

cadmium, zinc, magnesium or aluminium.

Fig. 3: Inductive circuits

Minimum igniting currents to be applied to

electrical apparatus containing cadmium, zinc,

magnesium or aluminium at E = 24 V.

1 V 3 V 10 V 30 V 100 V 300 V 1000 V

C = 40 Ω (Cd)

C = 15 Ω (Cd)C =5,6 Ω (Cd)

(Cd)

(Sn)

0,01 µF

0,03 µF

0,1 µF

0,3 µF

1,0 µF

3 µF

10 µF

30 µF

100 µF

300 µF

1000 µF

3000 µF

10.000 µF

5 mA 10 mA 20 mA 50 mA 100 mA 200 mA 500 mA 1 A100 µH

200 µH

500 µH

1 mH

2 mH

5 mH

10 mH

20 mH

50 mH

100 mH

200 mH

500 mH

1 H

I

II AII B

II C

Safety level -ib-Category -ib- electrical apparatus must not becapable of causing an ignition during normaloperation and with the occurrence of a singlefault.Here the following safety factors have to betaken into consideration:Safety factor 1.5 in normal operation and

with one fault

Constructional requirements

Any components on which the intrinsic safetydepends (with the exception of transformerswhich are subject to special conditions), mustnot be charged with more than 2/3 of their ratedcurrent, rated voltage or rated capacity, even inthe event of faults (e. g. mains voltage at theinput side of electronic circuits).

Types of limiting modules

Safety barriers with diodesSub-assemblies comprising diodes or Zenerdiodes that are protected by a fuse or a resistormay be used as safety barriers between intrinsi-cally safe circuits and a non-intrinsically safe cir-cuit. The input current of such barriers must besuch that they can be connected to a mainssupply with a maximum short-circuit current of1.5 kA.

Apparatus with galvanic isolationTransformers that, for example, are built into intrinsically safe power supplies must ensure asafe galvanic isolation between the primary andthe secondary circuit. The data that is relevantfor the intrinsically safe circuit is determined bythe output characteristic of the transformer andany external circuits (voltage limitation by diodes,current limitation by resistors or by the electro-nics).

Isolation of intrinsically safecircuits from non-intrinsicallysafe circuits

Connection piecesIn order to avoid any mistakes when connectingor bridging conductors, the connection piecesfor intrinsically safe circuits must be safely isola-ted from the connection pieces of a non-intrinsi-cally safe circuit. For this purpose the connec-tion terminals of the intrinsically safe circuit can,for example, be installed at a distance of at least50 mm from the connection pieces of each non-intrinsically safe circuit or they can be separatedby an isolating barrier or an earthed metal bar-rier. These barriers must either reach up to 1.5mm from the enclosure wall or they must ensurea minimum clearance of 50 mm between theconnection pieces.

Isolation of insulated leads of intrinsi-cally safe circuits and non-intrinsicallysafe circuitsThe distance between the conductors ofinsulated leads must satisfy specifiedrequirements. With the exception of varnishesand similar coatings, this insulation is consideredto be a solid insulation. The clearances aredetermined by the addition of the radial thickn-ess of the insulation on the wires. The minimumclearances are laid down in EN 50 020.e. g. when U =/≤ 060 V 0,5 mm

when U =/≥ 750 V 1,4 mm

The voltage U is the sum of the voltages of theintrinsically safe and the non-intrinsically safe cir-cuits. This clearance is not required, – if the leads of the intrinsically safe or the non-

intrinsically safe circuits are furnished with anearthed screen, or,

– if, with safety level -ib- electrical apparatus,the insulation of the leads of the intrinsicallysafe wires withstands an AC test voltage of2000 V. In addition to this, care must be takenthat no inductive or capacitive interferencesfrom the non-intrinsically safe circuit can resultin the intrinsically safe circuit.

Apparatus for intrinsically safecircuits

As with all other types of protection, generally allassociated electrical apparatus used in the in-trinsically safe circuit and the intrinsically safeapparatus must be tested and certified. Accor-ding to EN 50014 the only exception is appara-tus where, according to the data given by themanufacturer, none of the values 1.2 V; 0.1 A;20 µJ or 25 mW is exceeded.

Intrinsically safe apparatus where the electricaldata and the thermal behaviour can be clearlydefined and that conform to the applicable con-structional requirements, do not need to betested or certified.This applies, for example, to:• switches• plugs and sockets• terminal boxes• measuring resistors• single semi-conductor components• coils (moving coil instruments)• capacitors• electric position sensors (DIN 19 234)

It is absolutely essential to comply with thegeneral requirements according to EN 50 014and with the requirements for the design ofenclosures and connection boxes with regard tothe surface resistance or the choice of alumi-nium alloy (surface resistance of plastic enclosu-res < 109 ohms).


Design of intrinsically safe circuits

When setting up an intrinsically safe circuit withonly one intrinsically safe apparatus and oneassociated apparatus, the limiting values for thepermissible external capacitance and induc-tance indicated on the type label of the associa-ted apparatus are binding for that circuit.

Based on the maximum possible feed-in energyof the associated electrical apparatus, it is onlynecessary to check the thermal behaviour of theintrinsically safe apparatus. When several intrin-sically safe circuits are interconnected (e. g.several pieces of associated apparatus act onone piece of intrinsically safe apparatus), a moredetailed check of the intrinsic safety is required.

It is necessary to determine the maximum vol-tage and current values which, due to the inter-connection, occur in a fault condition. Here thefault consideration in accordance with EN 50020 (for example, 1 fault with one intrinsicallysafe circuit or safety level -ib-) has to be appliedto the interconnected system.

The simplest method is based on the assump-tion that all the associated electrical apparatustakes on the sum of the maximum values of cur-rent and voltage values. If this fault considerationis not successful (inadmissibly high values), amore thorough check has to be carried outbased on the assumption of the faults possiblefor the individual categories. The check relating to the intrinsic safety of a cir-cuit is to be documented in detail.

Specification of permissible externalinductances and capacitances of sup-ply units for intrinsically safe circuitsUntil now the maximum values for La and Ca ofsupply units for intrinsically safe circuits were laiddown by some testing and certification authori-ties in such a way that the operator only had tocheck whether the connected inductances andcapacitances La and Ca (including cables andconductors) were always less than the maxi-mum values. Here it was assumed that theconnected inductances and capacitances areconnected to the supply unit simultaneously andin concentrated form, thus constituting a criticalload. These testing institutes took this simulta-neous occurrence of La and Ca into considera-tion for ia circuits and non-linear ib circuits. Asother testing institutes work on the assumptionthat either an external capacitance (with negli-gible inductance) or an external inductance (withnegligible inductance) is connected, they certi-fied the data that was more favourable for themanufacturer. Due to pressure from the market,the testing institutes that had previously workedon the basis of a simultaneous occurrence ofcapacitance and inductance when specifyingthe safety-related data now felt forced to adoptthe less restrictive approach. By way of a theo-

retical example (full utilization of the externalconnected load), it can, however, be proved thatthe safety factor 1.5 (according to the old data)can be reduced to 0.91 based on the newobservations. Therefore, in critical cases wherethere is a simultaneous occurrence of concen-trated inductances and capacitances, it isnecessary to consult a specialist (manufacturer,expert).

Intrinsically safe circuits with ZenerbarriersNormally intrinsically safe circuits must be insula-ted. They may be connected to earth, if this isnecessary for functional reasons They must,however, be earthed, if this is imperative forsafety reasons. Earthing is only permitted at onepoint by connection to the potential equalizationwhich must exist in the whole area where theintrinsically safe circuit is set up.

Since, with safety barriers, there is no galvanicisolation between the intrinsically safe and thenon-intrinsically safe circuits, for safety reasonsthere must be a perfect connection to earth.

Working on and testing of int-rinsically safe circuits

As intrinsically safe circuits must be designed sothat they cannot cause an ignition, it is generallypermitted to work on them while they are live.When using measuring instruments it is, howe-ver, necessary to bear in mind the fact that suchinstruments may contain inner energy stores (e.g. the inductance of a moving coil instrument)that might neutralize the intrinsic safety.


Intrinsically safe electrical systems ”i”EN 50039 / VDE 0170/0171, Part 10

Technical terms

Intrinsically safe electrical systemsAll the interconnected electrical apparatus docu-mented in a system description, where the cir-cuits that are to be used wholly or partly in apotentially explosive atmosphere are intrinsicallysafe.

Certified intrinsically safe electricalsystemsAn intrinsically safe electrical system for which acertificate has been issued confirming that thetype of that electrical system conforms to theEuropean standards.

Provided that the electrical apparatus can beclearly identified, a certificate for each individualpiece of electrical apparatus in an intrinsicallysafe electrical system is not necessary.

Non-certified intrinsically safe electrical systemsAn intrinsically safe electrical system where theintrinsic safety can be verified without a doubtbased on the knowledge of the electrical cha-racteristics of the certified intrinsically safe elec-trical apparatus, the certified associated electri-cal apparatus and of the non-certified ”simpleapparatus” and based on the knowledge of theelectrical and physical characteristics of theconnecting leads.

System descriptionA document drawn up by the system designengineer in which the electrical apparatus, theelectrical characteristics there of and the characteristics of the connecting leads aredescribed. The term ”system design engineer”designates a person who is responsible for theintrinsic safety of the system.

Each part of an intrinsically safe electrical systemthat is used in a potentially explosive atmos-phere must be classified as safety level ia or ib.This does not mean that the whole system hasto be assigned to one single safety level. Thesafety levels ia and ib are explained in detail inthe chapter Intrinsic safety ”i”.

Further information on intrinsically safe circuitscan be found in EN 60 079-14 VDE 0165, Part 1”Electrical installations in potentially explosiveatmospheres”.


Cap lamps for use inmines susceptible to firedampEN 62013-1/ VDE 0170/0171 Part 14

The requirements relating to the design andtesting of cap lamps for use in mines suscep-tible to firedamp (electrical apparatus for use inGroup I potentially explosive atmospheres) arelaid down in this standard

Technical terms

Cap lampAn apparatus comprising a headpiece, aconnecting cable and rechargeable secondarycell(s)/battery in a container.

Constructional requirements The cap lamp must be designed in such a waythat, if a fuse or thermal cicuit breaker is used asover-current protection,• the rated voltage does not exceed 6 V,• the current does not exceed 1.5 A when ope-

rated as intended,• the lamp rating is not higher than 6 W,• the circuit behaves as if it only contains active

resistances.

The housing of the cap lamp headpiece must-provide protection against the ingress of dustand water according to the minimum degree ofprotection IP 54. The headpiece housing must have a speciallocking device according to EN 50 014..

The transparent protective lens of the headpiecemust withstand the mechanical requirements inaccordance with EN 50 014. It must only bepossible to remove the protective lens and, ifavailable, the protective guard and collar afterthe locking mechanism has been released.

The battery container must provide a minimumprotection against the ingress of dust and wateraccording to IP 54 for the electrical connections.The fuse must be protected in such a mannerthat, if it ruptures, the surrounding mixture of airand gas (methane or charging gas) is not igni-ted.

The flexible cable connecting the battery contai-ner and the headpiece shall be provided with asheathing that is resistant to fatty acids and toflames.

Firedamp-protected cap lamp with nickel-cadmium

battery


Zone 0 apparatusEN 50 284 VDE 0170/0171Part 12

EN 50 284 VDE 0170/0171, Part 12-1:”Special requirements for the design, testing andmarking of electrical apparatus in apparatusGroup II, Category 1G” This European standard lays down detailedrequirements for apparatus in apparatus Group II, Category 1G. The apparatus must bedesigned in such a way that it guarantees a veryhigh degree of safety in normal service. Category 1 apparatus is intended for use inpotentially explosive atmospheres in whichexplosive mixtures of air with gases, vapours ormists occur continuously, for long periods or fre-quently. This standard also applies to apparatusthat is mounted in the barriers between differentpotentially explosive atmospheres. It also inclu-des requirements for apparatus that is installedoutside the potentially explosive atmosphere,but that is connected electrically to Category 1apparatus (associated apparatus).

It supplements the standards EN 50 014 andEN 50 020 to EN 50 028 and is intended toadapt the safety level provided for by thesestandards to the extremely high risks.

In order to eliminate the ignition hazards that canemanate from the electrical circuits of the appa-ratus, the necessary measure of safety must eit-her be guaranteed, even if two faults that areindependent of each other occur, by applying asingle constructional protection measure, or, ifone constructional protection measure fails, itmust be ensured by a second, independentconstructional protection measures.

Permissible individual constructional protection measures are:• Apparatus and circuits in accordance with

the requirements of EN 50 020, safety level ”ia”

• Encapsulated apparatus in accordance withthe requirements of EN 50 028 supple-mented by the additional requirements ofthis standard.

Combinations of constructional protection measuresElectrical apparatus must fulfil the requirementsof two standards of the series EN 50 014 to EN50 020 (ib) and EN 50 028 independently ofeach other. These combined standardized typesof protection must be based on different physi-cal protection principles. It must be possible totest them independently of each other. Theadjacent table illustrates the possible combinati-ons of barriers with the types of protectionwhere barrier elements are used.

Apparatus and parts thereof for use in Zone 0must also be built in such a way that• ignition sources due to impact or friction

sparks are excluded.In the case of apparatus with parts thatmove during operation, light metals mustnot be used at the possible friction orimpact points or at other accessible points.

• no ignition hazards due to dangerous elec-trostatic charges can occur. Special conditi-ons apply to enclosures and parts of enclo-sures made of moulded plastic

Connection techniqueAs far as possible, connections for Zone 0apparatus and parts thereof should be locatedoutside the Zone 0.

Hazardousarea1)

Barrier

Less hazardous area2)

Electricalapparatus

Hazardousarea1)

Barrier3)Electricalapparatus

Gap3)

Barrier3)

Naturalventilation

(Gap3))

1) Category 1 apparatus required2) Category 2 apparatus or less required3) Flameproof joint and barrier can be swapped round

Type of construction

Requirements according to the thickness t of the barrier(i) t ≥ 3 mm, no additional measures

(ii)3 mm > t ≥ 1 mm

(iii)1 mm > t ≥ 0.2 mm

(“X“ symbol)

(iv)t < 0.2 mm

(“X“ symbol)

– standardizedtype ofprotection and

– no ignitablesparks duringoperation(e.g. no openswitchingcontacts)

Type of protectionIntrinsicSafety “ib“

Not permissible

– standardizedtype ofprotection and

– no ignitablesparks duringoperation(e.g. no openswitchingcontacts)

– standardized type of protection

– standardized type of protectionand

– flameproof joint (broken line)

– standardizedtype ofprotection

a) Barrier

b) Barrier and gap

c) Barrier and ventilation


Hazardousarea1)


Electricalapparatus


Zone 2 apparatusType of protection ”n”EN 50 021/VDE 0170/0171Part 16

The type of protection ”n” applies to electricalapparatus of the apparatus category 3G, that,under normal and certain abnormal operatingconditions, are not able to ignite a surroundingexplosive atmosphere. These operating conditi-ons are laid down by the manufacturer as partof the electrical and mechanical design data andit is essential that the user observe them. Theaim of this type of protection is to find an econo-mical compromise between the normal industrialstandard and the high safety requirements forthe types of protection for apparatus in theCategory 2G.

General requirementsAs with the already familiar types of protectionfor the apparatus category 2G, the generalrequirements for electrical apparatus (e.g. sur-face temperature, design, cables, clearancesand creepage paths, …) also apply here.

Potential ignition sourcesBasically distinction is made between non-spar-king apparatus, that does not give off anypotential ignition sparks during operation, andapparatus that gives off arc or sparks or produ-ces hot surfaces during normal operation. In thecase of this apparatus, that, on principle, fea-tures potential ignition sources, it is necessary totake additional protective measures to allow itssafe operation.

Non-sparking apparatusDepending upon the type of apparatus (e.g.electric machines, luminaires), non-sparkingapparatus must fulfil additional conditions, sothat no potential ignition sources can developduring normal operation. In addition to the appa-ratus category 3G, the apparatus is also markedwith ”nA”, whereby this combination of lettersstands for ”non-sparking apparatus”.

Apparatus that gives off arcs or sparksor produce hot surfaces Apparatus that gives off arcs or sparks or pro-duces hot surfaces during normal operationmust be safeguarded by additional measures insuch a way that these ignition sources cannotignite a surrounding explosive atmosphere. Themeasures that are necessary for this are model-led on the familiar types of protection for appa-ratus category 2G, whereby the safety require-ments are less stringent. Parts of apparatus can,of course, be protected by the types of protec-tion of EN 50 014 ff. A group of additional mea-sures involves the safe isolation of the potentialignition source from the explosive atmosphereby means of the technical construction, gene-rally a special enclosure, or designing the appa-ratus in such a way that flame transmissionthrough the enclosure is not possible.

The ”hermetically sealed devices”, the ”sea-led devices” and the ”encapsulated devi-ces” are based on the fact that the explosiveatmosphere and the potential ignition sourceremain safely isolated from each other. The”enclosed switching devices” are modelledon the familiar type of protection ”Flameproofenclosure” to.With EN 50 018 the ”non-ignitable compo-nent” ignition is prevented by constructionalmeasures, while, at the same time, the type ofgas is taken into consideration. The marking”nC” is used for this group of measures, whe-reby the permissible type of gas (IIA, IIB, IIC)must also be stated. The ”restricted breathingenclosure” is another permissible explosionprotection measure with the marking with ”nR”.The enclosure is designed in such a way that anexplosive atmosphere can only enter it in arestricted measure. The ”simplified pressu-rization” is modelled on the familiar type of pro-tection ”Pressurization”, whereby simplifiedmeasures were approved. This apparatus ismarked with ”nP”.A further explosion protection measure is the”restricted energy apparatus” with the mar-king ”nL” and the marking for the suitable gasgroup (IIA, IIB, IIC). This is based on the type ofprotection ”Intrinsic safety”, whereby the safetyfactors are less stringent.

DocumentationAs it is possible to have a combination of variousexplosion protection measures for apparatuscategory 3G, it is strongly recommended thatthe operator study the associated documenta-tion carefully, because all the safety instructionsissued by the manufacturer must be observedfor maintaining safety.

Explosion-protected plugs and sockets for Zones 2 and 22





Explosive atmosphere Explosive atmosphere

Hermetically sealed devices ”nC” Sealed devices ”nC” Encapsulated devices ”nC”

Enclosed switching device ”nC” Non-sparking apparatus ”nA” Non-ignitable component ”nC”

Retricted energy apparatus ”nL” Restricted breathing ”nR” Simplified pressurization ”nP”

Inert gas

Types of protection ”n”

Selection for Zone 2 to EN 60 079-14

Apparatus forZones 0,1

Apparatus designed for Zone 2

(EN 50 021 ”n”)

Recognized industrial standard

No IEC standardavailable => ”s”

No ignitable hot surfaces

Arcs or sparks

Energy restrictionSafety factor 1 to EN 50 021

Written evaluation by a specialist

no

yes


Ignition sources

Combustible dust can be ignited by electricalapparatus in various ways:- by apparatus surface temperatures that are

higher than the ignition or glow temperatureof the respective dust. The temperature atwhich the dust ignites is dependent on theproperties of the dust, on whether it is pre-sent in the form of a cloud or deposits, onthe thickness of the layer and on the type ofheat source;

- by sparks at electrical parts such as swit-ches, contacts, commutators, brushes orsimilar;

- by the discharge of stored electrostaticenergy;

- by radiated energy (e.g. electromagneticradiation);

- by magnetic impact or friction sparks or arise in temperature originating from theapparatus.

To avoid ignition hazards, it is necessary that:- the temperature of any surfaces on which

dust deposits can form or that can comeinto contact with a cloud of dust are keptat a temperature that is lower than the limiting temperatures laid down in EN 50028-1-2;

- all parts with electric sparks or with tempe-ratures above the ignition or glow tempera-ture of the dust are built into an enclosurethat prevents the ingress of dust in a suit-able manner, or

- the energy of the electric circuits is limited tosuch a degree, that sparks or temperaturethat could ignite combustible dust are avoided;

- all other ignition sources are avoided.

Electrical apparatus for use in areas with combustible dustwith protection by the enclosure

Design and testingEN 50028-1-1 VDE 0170/0171Part 15-1-1This European standard applies to apparatuswhere protection is afforded by the enclosurewith limitation of the surface temperature. Itincludes requirements for the design, construc-tion and testing of this electrical apparatus ofapparatus group II, categories 1, 2 and 3. Thetype of protection is based on the limitation ofthe maximum surface temperature of the enclo-sure and on the limitation of the ingress of dustby the use of ”dust-tight” or ”dust-protected”enclosures. The principles of this standard canalso be applied if the hazard is caused by fibresor flue dusts. The use of electrical apparatus inareas that contain both explosive gases andcombustible dusts – simultaneously or separa-tely – requires additional protective measures.

Requirements on electrical apparatusin the categories 1 and 2For the main part it is necessary to fulfil therequirements of EN 50 014:e.g. mechanical strength of enclosures, thermalstability, thermal shock tests.In addition to this, it is also necessary to takespecific requirements for dusts, that are descri-bed in the standard EN 500281-1-1, intoaccount. For example, with plugs and sockets itis necessary to ensure that no dust can fall intothe socket.This apparatus must be tested and certified byan independent testing station.

Requirements for electrical apparatusin category 3 The requirements relating to the strength hasbeen reduced to the measure required for industrial apparatus. It is, however, necessary totake into account that the TI value is decisivewhen selecting materials. The specified IPdegree of protection for conductive dusts is 5Xor 6X. It should only be possible to releaselocking devices that are necessary to maintainthe type of protection with a tool.

MarkingApparatus in categories 1 and 2

Name/symbol of testing stationCertification number1 or 2 to show the categoryD for dust explosion protection followed by themaximum surface temperature T as definedcoefficient, e.g. T 170 °C

Apparatus in category 3

3 to show the categoryD for dust explosion protection followed by themaximum surface temperature T as definedcoefficient, e.g. T 170 °C

The following table (page 40) lists further stan-dards or intended standards for dust explosionprotection.

Electrical apparatus foruse in areas with combustible dusts

Ex-installation units for use in Zones 1 and 21


IEC 61241 Electrical apparatus for use in the presence of combustible dust

IEC 61241-1Electrical apparatusprotected by enclosures

IEC 61241-1-1Design and testEN 50281-1-1:1998-09DIN EN 50281-1-1(VDE 0170/0171 Part 15-1-1): 1999-10

IEC 61241-1-2Selection, installation andmaintenanceEN 50281-1-2:1998-09DIN EN 50281-1-2(VDE 0165 Part 2): 1999-11

IEC 61241-2-2Method for determiningminimum ignition energyof dustDIN EN 61241-2-2(VDE 0170/0171Part 15-2-2): 1996-04

IEC 61241-2-3Methods for deter-mining the minimumignition energy ofdust/air mixturesEdition: 1994-09[under modification, workshift to CEN/TC 305]

IEC 61241-2-4Methods for determi-ning minimum ignitionenergy of dust[under modification, workshift to CEN/TC 305]

IEC 61241-2-1Method for determiningminimum ignitionenergy of dustEN 50281-2-1:1998-09DIN EN 50281-2-1 (VDE 0170/0171Part 15-2-1): 1999-11

E DIN IEC 31H/47/CDV(VDE 0170/0171 Part 1505):1995-05[Intended asVDE 0165 Part 102]

E DIN IEC 31H/67/CD(VDE 0170/0171 Part 15-4):1997-08[Intended asVDE 0170/0171 Part 15-4]

IEC 31H/84/CD[Intended asVDE 0170/0171 Part 15-5]

IEC 61241-2Methods for determining

IEC 61241-3Classification of areaswhere combustible dustare or may be presentEN 61241-3:199X-XX

IEC 61241-4Electrical apparatus;type of protection pressurization ”p” (pD)

IEC 61241-5Electrical apparatus –intrinsic apparatus

Notes:Documents with figure ”6” in front were mainly prepared by IECDocuments with figure ”5” in front were mainly prepared by CENELECDocuments in square brackets have not been published yet

Table taken from EN 50 028-1-1 (VDE 0170/0171, part 15-1-1) 1999-10.3 page 3

In order to be able to assimilate the standardsfor gas explosion protection and dust explosionprotection in the future, IEC SC 31 H has deci-ded to rename the standards for dust explosionprotection. The following reference table illustra-tes the connections.

Existing standards Newly assigned numbers SubjectIEC 61241-1-1 IEC 61241-0 General requirements

IEC 61241-1 Protection by enclosureIEC 61241-1-2 IEC 61241-14 Selection and installationIEC 61241-2-1 IEC 61241-20-1 Test proceduresIEC 61241-2-2 IEC 61241-20-2 Test proceduresIEC 61241-2-3 IEC 61241-20-3 Test proceduresIEC 61241-3 IEC 61241-10 Zone classificationIEC 61241-4 IEC 61241-2 Protection by pressurization

IEC 61241-11 Protection by intrinsic safetyIEC 61241-18 Protection by encapsulationIEC 61241-17 Testing and maintenanceIEC 61241-19 Repairs and overhauling


Electrical installations in potentially explosiveatmospheres

Assessment of the explosionhazard

The BetrSichV §3 (2) obligates the employer todo the following: ”If, according to the provisionsof § 16 of the hazardous substance decree, theformation of potentially explosive atmospherescannot be prevented, the employer shall assess1. the probability and duration of the occurrenceof potentially explosive atmospheres,2. the probability of the presence, activation andtaking effect of ignition sources, including elec-trostatic discharges, and3. the extent and anticipated effects of explosi-ons.”

This assessment is the basis for the requiredclassification into potentially explosive atmos-pheres according to §5 of the BetrSichV. Thisclassification shall be carried out according toAnnex 3, BetrSichV.

Annex 3Zone classification of explosive atmospheres1. Preliminary remarkThe following zone classification applies to areasin which the measures in accordance with §§ 3,4 and 6 are to be taken. This classificationdetermines the scope of the required measuresaccording to Annex 4, Section A. Layers, depo-sits and accumulations of combustible dust areto be treated in the same way as any othersource that can form an explosive atmosphere.Normal operation is defined as being the condi-tion under which installations are used within thescope of their design parameters.

2. Zone classificationHazardous areas are classified into zones accor-ding to the frequency and the duration of thepresence of potentially explosive atmospheres.

2.1 Zone 0An area in which an explosive atmosphere con-sisting of a mixture with air of flammable substan-ces in the form of gas, vapour or mist is presentcontinuously or for long periods or frequently.

2.2 Zone 1An area in which an explosive atmosphere con-sisting of a mixture with air of flammable sub-stances in the form of gas, vapour or mist islikely to occur occasionally during normal opera-tion.2.3 Zone 2An area in which an explosive atmosphere con-sisting of a mixture with air of flammable sub-stances in the form of gas, vapour or mist is notlikely to occur during normal operation but, if itdoes occur, it will persist for a short period only.

2.4 Zone 20An area in which an explosive atmosphere in theform of a cloud of combustible dust in air is pre-sent continuously or for long periods or fre-quently.

2.5 Zone 21An area in which an explosive atmosphere in theform of a cloud of dust in air is likely to occuroccasionally during normal operation.

2.6 Zone 22An area in which an explosive atmosphere in theform of a cloud of combustible dust in air is notlikely to occur during normal operation but, if itdoes occur, it will persist for a short period only.

For the sake of completeness, the old zoneclassifications for areas with combustible dustare listed here. Provided that no changes havebeen made to installations, these continue toapply during the interim period (max. until 2007).

Zone 10Zone 10 covers areas in which an explosiveatmosphere is present for long periods or fre-quently.

Zone 11Zone 11 covers areas in which the occurrenceof an explosive atmosphere as the result of thestirring-up of dust deposits is to be expectedoccasionally for short periods.

The results of the hazard assessment shall berecorded in an Explosion Protection Document.According to § 6 (2) of the BetrSichV, this shall,above all, specify:1. that the explosion hazards have been deter-

mined and assessed,2. that appropriate measures have been taken,

in order to fulfil the explosion protection goals,3. which areas were classified into zones in

accordance with Annex 3 4. for which areas the minimum requirements in

accordance with Annex 4 apply.

Example of application: Explosion-protected apparatus in an oil terminal


In accordance with § 6 (3), the Explosion Pro-tection Document shall be drawn up beforework commences. It shall be revised if anychanges, extensions or modifications are madeto the work equipment or the work processes.

Once the zones have been determined, the localareas in which the occurrence of an explosiveatmosphere is to be expected shall be markedin a clearly discernible and durable manner withthe prohibition sign V2 ”Fire, open flames andsmoking prohibited” (Fig. 1) and the warningsign ”Warning – explosive atmosphere” (Fig. 2”)in accordance with VBG 1, VBG 125 and DIN40012, Part 3.

The following are useful when assessing thedegree of hazard and determining the zone clas-sification:The Explosion Protection Regulations (EX-RL),rules and regulations for the avoidance ofhazards due to explosive atmospheres withcollection of examples,EN 1127-1, Explosive atmospheres – Explosionprotection – Part 1: Fundamental principles andmethodsandEN 60079-10, DIN VDE 0165, Part 101, Classifi-cation of potentially explosive atmospheres withflammable gas.

Assistance for the drawing-up of the explosionprotection document can be found in theNAMUR reference document NE 99, ”ExplosionProtection Document”.

Obligations of the manufacturer

The manufacturer shall develop and manufac-ture electrical apparatus for use in potentiallyexplosive atmospheres in accordance with therequirements of Directive 94/9/EC.If specified in the standards, testing by an inde-pendent testing station must be arranged. Theapprovals issued by the testing station and/orthe declarations issued by the manufacturersare to be placed at the disposal of the operator.It is the duty of the manufacturer to manufactureeach piece of electrical apparatus in such a waythat it complies with the test documentation andthe test samples. Finally, he is also obligated tosubject each piece of explosion-protected appa-ratus manufactured to a routine verificationand test and, after successful completion ofthis test, to mark the apparatus accordingly. If”special conditions” apply to the use of theapparatus, the manufacturer must provide theinstaller or the operator with this information in asuitable form together with the apparatus.

Obligations of the installer

Electrical installations in potentially explosiveatmospheres shall be installed in compliancewith the statutory regulations. The BetrSichVhas been in force here since 03.10.2002. ElexVapplied until this time. As with the ElexV, theBetrSichV also requires that the latest technolo-gical developments be taken into consideration.

Extract from BetrSichV:§ 12Operation(1) Installations requiring supervision shall be

installed and operated in keeping with thelatest technological developments. The rulesand findings determined by the Committeefor Operational Safety and published by theFederal German Ministry of Labour andSocial Order in the Federal Work Sheet shallbe taken into consideration for maintainingthe latest technological developments.

As long as the Committee for Operational Safetydoes not issue any other specifications, thelatest technological developments are determi-ned, among other things, by the valid standards.

Thus, apparatus shall be installed in accordancewith VDE 0165 ”Regulations for the setting-upof electrical installations in hazardous areas”and VDE 0100 ”The setting-up of power plantswith rated voltages up to 1000 V.” Inasmuch asthe provisions of VDE 0101 ”The setting-up ofpower plants with rated voltages of more than1 kV” and/or VDE 0800 ”Telecommunication”apply to the respective installations, these mustalso be observed.

With regard to areas with combustible dust, theGerman translation of EN 50281-1-2 as the Ger-man standard DIN VDE 0165, Part 1-2, ”Electri-cal apparatus with protection by the enclosure –selection, installation and maintenance, in theedition dated November 1999, applies.

If the installer is not also the operator, the instal-ler shall issue an installation certificate at theoperator”s request. This certificate confirms thatthe electrical installation conforms to the validrequirements. If such a certificate is available,additional testing by the operator prior to com-missioning is no longer necessary.

Fig. 1: Prohibition sign V2

”Fire, open flames and smoking prohibited”

Fig. 2: Warning sign ”Warning – explosive atmosphere”


Obligations of the operator

According to §§ 14 and 15 of the BetrSichV, theoperator is obligated to have the electrical instal-lations in the hazardous areas of his plantchecked by a qualified electrical engineer withregard to their proper condition, namely

• prior to commissioning (§14)(can be omitted if an installation certificate isavailable) and

• at regular intervals (§15).

Here, with regard to the operational require-ments, the operator shall calculate the intervalsin such a way that any faults occurring areascertained in time. The tests shall, however, becarried out at least every three years. Recordsshall be kept on the execution and results of theprescribed or ordered tests. These records shallbe stored at the operating site of the installationrequiring supervision and shall be presented tothe responsible authorities on request.

According to §12 (3) of the BetrSichV it is theduty of the operator to keep an electrical instal-lation in a potentially explosive atmosphere in aproper state, to operate it accordingly, to moni-tor it constantly and to carry out any necessaryrepair or maintenance measures immediately.

Finally, it is also the duty of the operator toensure that the electrical installation is operatedcorrectly. According to § 18 of the BetrSichV theoperator shall report the following to the respon-sible authorities immediately:

1. Any accident involving the death or injury of a person.

2. Any damages involving the failure of ordamage to components or safety installations.

The responsible authorities can demand that theoperator has an occurrence that is subject tonotification assessed by an approved controlauthority, if possible one agreed on by both par-ties, with regard to safety aspects and that hepresents them with a written assessment report.This safety assessment report shall, in particular,be based on the determination of1. what the occurrence is attributed to,2. whether the installation that was subject to

supervision was in correct order and whether,once the fault has been eliminated, there is nolonger any hazard

3. whether, based on new findings, other oradditional protective measures are necessary.

Ignitions that take place inside flameproof appa-ratus and that are not propagated to the surro-undings need not be reported.


Selection of electrical apparatus

Now, after completion of the zone classificationand the determination of the most critical tem-perature class and the explosion group, theelectrical apparatus can be selected.

Here the ruling principle is that only the electricalapparatus that is absolutely essential should beinstalled in the potentially explosive atmosphere.

On principle, the apparatus must be selectedand installed in such a way that it is sufficientlyprotected against external influences that canaffect the explosion protection, e.g. chemicalinfluences (solvents), moisture (spray water, con-densation), or vibration.

Apparatus according to the ATEX directive, itmust also be marked with the symbol . Inaddition to this, the mark shall also be affixedto the apparatus. Here it should be noted thatapparatus exists according to the old law withthe CE marking, namely if it was already subjectto another legal area that has already been har-monized (e.g. EMC, machine directive). Markingapparatus with the apparatus category is alsorequired. In the case of apparatus group II(apparatus group I = mines subject to firedampand any surface installations thereof; apparatusgroup II = other areas) this marking is carried outin conjunction with the category number and theletter G (GAS) for gases or D (DUST) for dusts:

1G for Zones 0, 1, 2 1D for Zones 20, 21, 222G for Zones 1, 2 2D for Zones 21, 223G for Zone 2 3D for Zone 22

The manufacturer or the person authorized byhim has to provide a Declaration of confor-mity in which he declares the conformity of theapparatus with the valid regulations. In additionto this, the manufacturer must draw up opera-ting instructions in a community languageand, if required, in the language of the country ofuse.One aspect of the operating instructions is thedescription of the intended use. Another newaspect is the description of all the necessarysafety information (e.g. from the type examina-tion certificate) and of all details relating to thesafe use of the apparatus. The operator of theapparatus must observe these operatinginstructions in full, otherwise the apparatus losesits approval. The Type Examination Certificate isno longer a compulsory part of the documenta-tion.

Selection of apparatus according tothe temperature classesAs already described in the previous section,based on the ignition temperature (Ti = 270° C),a temperature class (T3) is allocated to aflammable substance (e.g. hydrogen sulphide).For this example only apparatus with the tempe-rature class T3 to T6 may be used. Thus, themaximum surface temperature of the apparatuscannot ignite the surrounding explosive atmos-phere. When determining the temperature classof apparatus, one generally works on theassumption that the ambient temperature ran-ges from –20° C to +40° C. If the apparatus isto be used in another (usually higher) ambienttemperature, this apparatus must be designedfor this temperature, certified and marked accor-dingly. In the case of certain apparatus, a tem-perature class range (e.g. T3-T4) is given. Here,for example, it is necessary to consider the influ-ence of the medium (measurement medium) onthe maximum surface temperature and, there-fore, on the temperature class. The connectionof the measurement medium with the tempera-ture class is stated in the type examination certi-ficate or in the operating instructions. The instal-ler and, later, the operator are responsible forthe correct selection and maintaining of the tem-perature class.


Fundamental installation requirements

On principle, the VDE regulations DIN VDE0100, 0101, ….etc. and, in additon, EN 60 7914VDE 0165, Part 1, ”Electrical apparatus for usein potentially explosive gas atmospheres, Part14: Electrical installations in potentially explosiveatmospheres (with the exception of mines)” andEN 50281-1-2, VDE 0165, Parts 1-2 ”Electricalapparatus with protection by enclosure – selec-tion, installation and maintenance”.

Protection against contactProtective measures against direct contact arealready required in VDE 0100. With explosionprotection, the protective aim is to prevent, asfar as possible, any formation of sparks as aresult of contact with bare active parts (with theexception of intrinsically safe parts). Measuresrelating to protection against indirect contact arelisted in EN 60 079-14 for the individual networkforms.

Potential equalizationAccording to VDE 0165/EN 60 079-14, potentialequalization is required for the avoidance of igni-table sparks within the potentially explosiveatmosphere. Thus, any conductive parts that areassociated with the construction or installationand with which a potential shift is to be expec-ted must be incorporated in the potential equa-lization.

Examples of potential equalization:• via compensators (non-conductive) insula-

ted pipelines• insulated seals

The following need not be incorporated:• conductive window frames• conductive door frames.

It is not necessary to additionally connect enclo-sures to the potential equalization, provided that,by means of the fixing facilities, they have relia-ble contact to parts of the installation that, inturn, are incorporated in the potential equaliza-tion.

Lightning protection installationsIn VDE 0165 reference is made to the need for afunctioning lightning protection installation (seealso EX-RL). The individual requirements can befound in VDE 0185, Part 2. The protective aimformulated in EN 60 079-14 says that the effectsof lightning striking shall be reduced to a non-hazardous degree. An overvoltage protectiondevice is only required for intrinsically safe cir-cuits that lead into Zone 0.

Electrostatic chargesThe installation standards only formulate the fol-lowing protective aims against static charges:Electrical installations shall be installed in such away that ignition hazards as a result of elec-trostatic charges are not to be expected.

Electrostatic charges are the result of separatingprocesses involving at least one chargeablesubstance. The discharging of charged particlesof non-conductive materials (e.g. plastics) isusually the result of bunch discharges that canbe ignitable. In the case of fast separating pro-cesses (e.g. pulling-off of foils from rolls, drivebelts) sliding bunch discharges are possible.These are bursting with energy and, as a result,they are capable of ignition.

In Zone 0 discharges capable of ignition mustbe excluded, also taking rare operational faultsinto considerationIn Zone 1 discharges capable of ignition mustnot be expected in plants that operate properlyor in the event of operational faults that are to bereckoned with. Measures against discharges arenecessary in Zone 2 if they occur frequently. Adischarge resistance of 106 Ω is considered tobe sufficient electrostatically.


Electrical protection and monitoring devices

Overcurrent trips, safety thermal cut-outs, pres-sure switches and many more besides, that,after tripping, disconnect the part of the installa-tion in all external conductors, are considered tobe electrical protection and monitoring devices.The devices must not be able to automaticallyswitch the installation part back on again. Whenswitching on again or releasing them, it is neces-sary to ensure that the protection device is inworking order. If, as a result of the disconnec-tion, an expansion of the hazard is to be expec-ted, instead of disconnecting, it is sufficient togive a warning signal. In addition, EN 60 079-14requires the specification of measures thatafford immediate relief in this case.

Emergency shut-downAccording to EN 60 079-14, it must be possibleto disconnect the ”supply of the potentiallyexplosive atmosphere” from a safe location, Itshall be possible to continue to operate electri-cal apparatus for the avoidance of additionalhazards. These are supplied from seperatecicuits.

IsolationIn addition to this, to ensure safe operation, a disconnection device to is required for eachcircuit (or each group). This shall be marked toidentify the circuit.

Cables

On principle, cables must be selected in such away that they withstand any mechanical, electri-cal, chemical and thermal stress to be expected.After clarifying the type of stress and the loca-tion, the type of cable can be selected accor-ding to the marginal conditions of EN 60 079-14/VDE 0165, Section 9.

Cables that are not laid in the earth or in sand-filled ducts shall be protected to prevent firefrom spreading. Bushings for cables leading intonon-hazardous areas shall be sealed in an ade-quately tight way (e.g. sand cups, mortar seal).Unused openings in electrical apparatus forcable entries must be sealed in accordance withEN 50 014.

Parts of cables that are subjected to specialstress must be specially protected (e.g. conduit).However, closed conduit systems must not belaid, unless they are suited for potentially explo-sive atmospheres due to their special design(e.g. US standard).

Additional requirements

In addition to the basic requirements describedabove, there are further requirements accordingto the type of protection or apparatus.

Installations with intrinsically safe circuitsThe protection principle of the type of protectionIntrinsic Safety assumes that the energy in aninstalled circuit is always less than the ignitionenergy of an explosive atmosphere that mightsurround it. In this way, the ignition of the explo-sive atmosphere cannot occur.

An intrinsically safe circuit consists of the intrinsi-cally safe apparatus located in the potentiallyexplosive atmosphere and the associated appa-ratus for the isolation of the intrinsically safe fromthe non-intrinsically safe circuit. The associatedapparatus is installed in the non-hazardous area.Both types of apparatus are connected to eachother by cable

Selection of intrinsically safe apparatusWhen installing the intrinsically safe circuit (withjust one piece of associated apparatus), it isnecessary to ensure that, together with thecables, the maximum permissible values for thecircuit (e.g. inductance, capacitance) are notexceeded.

The temperature class and the explosion groupof the explosive atmosphere are further selectioncriteria that have to be taken into account.


Special conditions in intrinsically safecircuitsBefore installing intrinsically safe circuits, it isabsolutely essential to take the special conditi-ons of the type examination certificate (X-certifi-cate) and the operating instructions intoaccount. Additional requirements relating to theinstallation and earthing are often listed here.

Cables for intrinsically safe circuitsThe following requirements apply, on principle,for cables in intrinsically safe circuits:• Insulated cables only• Test voltage: conductor-earth-screen min.

500V AC• Fine-wire conductor ends – multicore cable

ends• Conductor diameter > 0.1 mm (also for fine-

wire conductors)• Protection against electro-magnetic input

couplings• Wires of intrinsically safe and non-intrinsi-

cally safe circuits must not be routedtogether

• Mechanical protection

Cables of intrinsically safe circuits must be mar-ked. If the sheathing or sleeves are to be mar-ked by colour-coding, they must be light blue.This means that light blue cables must not beused for non-intrinsically safe circuits in such aninstallation.

Interconnection of intrinsically safecircuitsWhen interconnecting intrinsically safe circuitswith more than one piece of associated appara-tus, the intrinsic safety must be guaranteed inthe event of a fault and must be verified by cal-culation.

Electrical machineryMost explosion-protected motors are designedin the type of protection Increased Safety.Electrical machinery must be protected againstinadmissible heating-up due to overload. Thefollowing protective devices are possible:

• Overcurrent protection devices with current-dependent delayed release

• Temperature monitoring by means of ther-mometer probes

• Other devices that provide equivalent pro-tection as required.

If the overload protection of an Ex-e machine isprovided exclusively by temperature monitoringdevices, the design of the machine must bespecially tested and certified for this. In general,current-monitored motors may only be used forcontinuous operation with easy and infrequentstarts. Variable speed Electric motors for varia-ble voltages and frequencies (frequency conver-ter) shall:

a) if designed in the type of protection Increa-sed Safety ”e”, be certified as a unittogether with the converter

b) if designed in the type of protection Flame-proof Enclosure ”d”, be approved for con-verter operation in the type examination cer-tificate.

LuminairesOnly those lamps specified by the manufacturerin the documentation (type label) may be usedfor luminaires.

CommissioningIn accordance with BetrSichV §14, after aninstallation has been set up and before it is putinto operation for the first time, the operator musthave the correct state of the installation inspec-ted by a specialist. Until now in Germany anelectrician is considered to be such a specialist,who, of course, must also have a good know-ledge of explosion protection. The latest techno-logical developments must be considered as thebasis for testing. The tests may also be carriedout by a specialist from an outside company,provided that he has been trained accordingly.The results of the tests shall be recorded (§ 19BetrSichV). If the planner and the installer comefrom different companies, they must reach anexact agreement regarding their respectiveareas of responsibility. In the case of intrinsicallysafe circuits, the planning documents that act asthe basis for the proof of the intrinsic safetymust be coordinated with the installation, sinceany changes during installation can influence thebasis for the intrinsic safety.


When work is carried out in potentially explosiveatmospheres, the safety of people and installati-ons depends, to a high degree, on the strictadherence to all safety regulations. The com-pany management, the operators and the main-tenance personnel must work together in thebest possible way to guarantee a high degree ofsafety. Thus, the maintenance personnel wor-king in such plants has a special responsibility.

Rules, regulations and decrees

The following shall be observed when setting-upelectrical installations in potentially explosiveatmospheres:• Decree on health and safety protection for the

provision of work equipment and the use the-reof during operation, on safety during theoperation of installations requiring supervisionand on the organisation of operational safetyprovisions (Operational Safety Decree – BetrSichV)

• Decree concerning the putting into circulationof apparatus and protective systems for use inpotentially explosive atmospheres – explosionprotection decree (ExVO)

• Harmonization of the laws of the member sta-tes relating to apparatus and protectivesystems intended for use in potentially explo-sive atmospheres (94/9/EC)

• Minimum regulations for the improvement ofthe health protection and safety of employeesthat can be endangered by explosive atmos-pheres (1999/92/EC)

• Explosion protection rules (EX-RL) with collec-tion of examples issued by the Employers Lia-bility Insurance Association of the chemicalindustry

• Directives for the prevention of ignitionhazards as a result of electrostatic chargeslaid down by the central union of the employ-ers” liability insurance association

• Accident prevention regulations issued by theemployers” Insurance Liability AssociationBGV A2 ”Electrical installations and appara-tus”.

On principle, the following VDE specificationsapply to the setting-up of electrical installations:• VDE 0100, 0101, 0107, 0113, 0141, 0185,

0190, 0800 Part 1 - 4

In addition, the following VDE specificationsmust be observed for potentially explosiveatmospheres: • VDE 0165 (2/91), VDE 0165-1, VDE 0165-2

and VDE 0170/0171 (all parts).

The following applies to the operation and main-tenance of existing installations:• VDE 0105 Operation of power plants

– Part 1 General specifications

Maintenance

Maintenance includes all measures (inspection,servicing and repairs) for maintaining and resto-ring the nominal state, as well as for the determi-nation and evaluation of the actual state. Inspec-tions and supervision help prepare servicingwork and outline trends indicating possibledamages. The inspection in the form of a visualcheck shows the experienced specialist, e.g. bydrips at the switch box, whether more intensivechecks are necessary.

Special safety measures

For all work carried out in potentially explosiveatmospheres it is necessary to ensure that nei-ther sparks capable of causing an ignition norsurfaces that are too hot occur, that, in conjunc-tion with the explosive atmosphere, could leadto an explosion. On principle, work on live elec-trical installations and apparatus in hazardousareas is forbidden.Exceptions are work on intrinsically safe circuitsand, in special cases, on other electrical installa-tions. In this case the works management mustissue a hot work permit as written confirmationthat no explosion hazard exists at the workplacefor the duration of the work in hand. Theabsence of voltage may only be measured withexplosion-protected measuring instruments. Thespecial cases named above are the only excep-tions. Earthing or short-circuiting in hazardousareas is only permitted if there is no explosionhazard.

Prevention of sparkingThe types of protection of the electrical appara-tus being used ensure that sparks capable ofcausing an ignition or hot surfaces do not comeinto contact with the explosive atmosphere. If noother organisational measures are taken, onlyexplosion-protected measuring instruments maybe used for the measurement of electric values.Sparks capable of causing an ignition can alsoresult when connecting or disconnecting cablesalthough no voltage is connected. The reasonsfor this can be possible energy stores of electri-cal installations, as well as induction or electro-magnetic fields. The electrician must, at alltimes, be aware of whether or not sparks capa-ble of causing an ignition are to be expected.Another hazard area, where sparks capable ofcausing an ignition can occur, is the dischargingof static charges. The possible formation of sparks must also betaken into consideration when using hand tools.Here distinction is made between two types oftools. Tools where a single spark is given offduring use, e.g. screwdrivers or spanners, andtools that give off a shower of sparks during use,e.g. cutting or grinding tools. In general, the useof tools that can give off sparks is not permittedin Zones 0 and 20. According to EN 1127 onlysteel tools that can only give off a single sparkmay be used in Zones 1 and 2, provided that nosubstances of the explosion group II C are pre-sent in this area. The use of steel tools that cangive off a single spark is permitted in Zones 21

Maintenance and repair of explosion-protectedapparatus


and 22. Tools that give off a shower of sparksmay, on principle, only be used in conjunctionwith a so-called ”hot work permit” if it has beenascertained that no explosive atmosphere ispresent for the duration of the work. The appro-priate safety measures must be specified in thepermit.

Hot work permit for work involvingignition hazards in potentially explo-sive atmospheres(See Annex 2 for sample)Many tasks, such as the use of tools that giveoff showers of sparks, torch cutting and wel-ding, the use of non-explosion-protected mea-suring devices or repair work with different typesof protection may only be carried out in thehazardous area if, at the same time, no explo-sive atmosphere exists. After measures (primaryexplosion protection) have been taken to ensurethat no explosive atmosphere is present in thework area, the works manager or his represen-tative tests the effectiveness of the measuresthat have been taken. If required, before work iscommenced the atmosphere is tested using agas warning device that is calibrated, explosion-protected and suitable for the type of gas to bedetected.The person responsible now issues a writtenrelease note (hot work permit) for the necessarymaintenance measures that involve the possibleformation of sparks capable of causing an igni-tion. The place, the time for the beginning ofwork, the duration and the types of protectivemeasures required are laid down in this docu-ment. Additional protective measures are alwaysnecessary if a renewed formation of an explosiveatmosphere cannot be excluded. Approachingclouds of explosive atmosphere can be detec-ted using gas warning devices, provided that thecorrect types are used for the respective type ofgas (heavier or lighter than air) and ambient con-ditions (see Gas warning devices for explosionprotection – use and operation 1/2003 – T 023).The gas warning devices must, however, beused in such a way that, after an optical oracoustic alarm warning has been given, suffi-cient time remains to make possible ignitionsources ineffective.After the work has been completed and this hasbeen reported, the effectiveness of the neces-sary explosion protection measures must nowbe re-established.

Operation

Once an installation has been installed correctly,it is then necessary that it is operated in keepingwith the latest technological developments andstandards. In accordance with §12 BetrSichV,the responsible operator must observe the follo-wing important principles:• Maintaining the electrical installation in due

order• Monitoring of the electrical installation• Immediate execution of necessary repair

measures• Stopping operation in the event of faults that

cannot be repaired and can endanger thepersonnel

Maintaining in due working orderAfter commissioning an installation, it is alsonecessary to ensure that it remains in due order.This requires the testing of installations accor-ding to §15 BetrSichV at given intervals, whe-reby installations shall be tested at least everythree years. EN 60079-17/VDE 0165, Part 10”Testing and maintenance of electrical installati-ons in potentially explosive atmospheres” can beapplied here. In Section 4.5 of this standardconstant supervision is described as onemethod for maintaining the correct state ofinstallations.


Constant supervision

”Constant supervision” is defined as being thecontinuous supervision of electrical installationsby specialized personnel that is familiar with thelocality, the aim of which is the permanent main-taining of the installation in due working order,the fast recognition and immediate elimination ofany faults that may occur, and the early detec-tion of changes with the implementation of suita-ble countermeasures. In order to put this continuous supervision intopractice, the responsible operator of the installa-tion must employ specialized personnel on apermanent basis and must allow them sufficientfreedom for the supervision of the installations.Special knowledge of the installation and theparticular stresses are necessary to be ableidentify possible weak points at an early stage. In the course of his supervisory tasks, such as,for example, check patrols, inspections, servi-cing, cleaning, trouble-shooting, switchingactions, connection and disconnection ofcables, setting and adjustment work, modificati-ons and installation work, the electrician detectsany faults or changes at a very early stage, thusmaking it possible to take the necessary repairmeasures in good time. Constant supervisionshall be carried out at the responsibility of a spe-cialist in a key position (responsible engineer).For the qualification of the responsible engineer,priority is given to the function description andnot the course of his training. The position requi-res a responsible person in a leading functionand the position can, for example, be filled by atrained technician with the appropriate speciali-zed knowledge. On the basis of this knowledge,he controls the qualification of specialized staffand the execution of the constant supervision byspecifying appropriate operation sequences andby analyzing changes in the ambient conditions,the feedback relating to repair work and randomindividual tests, in order to use the informationgained to undertake the necessary measures foradapting the electrical installations. at an earlystage. If the constant supervision is documentedin an appropriate manner, under certain circum-stances a large part of the recurrent tests accor-ding to § 15 BetrSichV can be covered.

Servicing

Based on these findings, maintenance workshall be carried out according to the type of pro-tection used. In the case of apparatus that ismanufactured and approved according to theATEX directive 94/9/EC, the necessary mainten-ance measures can be found in the operatinginstructions. Some possible maintenance tasksare listed below.Since, due to the joint specified in VDE 0171 forflameproof enclosures, the protection againstwater of flameproof enclosures and of EEx-eenclosures is only limited (IP 44 and IP 54), spe-cial attention must be paid to any accumulationof water in the enclosure. Slightly rusty joints shall not be cleaned with anabrasive or wire brushes, but with chemicalagents such as non-resinous and non-acidreducing oils. Afterwards the joint surfaces mustbe carefully preserved.Particular attention must be paid to ensure thatany covers that were removed are put backonto the associated enclosure base and scr-ewed down well. Covers of the same type mustnot be interchanged. The gasket on EEx-eenclosures must be checked for damages and,if necessary, replaced.Terminals, in particular inan EEx-e enclosure, are to be tightened. Anydiscoloration indicates a rise in temperature.Cable glands, blanking plugs and flanges are tobe checked for tightness and close fit. Whenreplacing incandescent lamps, it is necessary toensure that only lamps have been certified forthe luminaire may be used. Overcurrent protec-tion devices and the suitability of fuses, motoroperating currents and tE times must bechecked. Windings and bearings of motors must– as far as possible – be checked for damages(running noises) and changes (rise in tempera-ture). Sand fillings in cable ducts and wall bushingsshall be checked. Cable trenches and ductsshall be checked for water. Cable sheaths mustbe checked for perfect condition and cable traysfor mechanical and chemical damage. Thisrequires a good knowledge of the valid regulati-ons and requirements.


Repairs

Repair measures should be planned and, as arule, be carried out during a scheduled shut-down.

Replacement of apparatusWork on electrical apparatus and installations inexplosive atmospheres may only be carried outif a work permit stating the necessary safety pre-cautions has been issued by the works managerand if these measures have already been carriedout.When replacing electrical apparatus, attentionmust be paid to the intended application , i.e. tothe temperature class, explosion class and (Ex)zone or apparatus category. Moreover, the certi-ficate of conformity, PTB test certificates anddesign approvals must be available. The manu-facturer”s declaration of conformity and theassociated operating instructions must be avai-lable for apparatus according to the ATEX direc-tive 94/9/ECIn the case of EEx-e motors, the time tE must beobserved. Lamps in stationary light fittings may only bereplaced if• in Zone 0 the external and neutral conductor

are switched off, • in Zone 1 at least the external conductor(s)

is/are switched off.

Lamps in portable lights may only be replacedoutside of hazardous areas.Lamps may only be replaced by lamps whoserating and type correspond to the data on theluminaire.In the case of luminaires in the type of protection”Increased Safety” only general-purpose lampsaccording to DIN EN 60 064 may be used. Inthe case of special lamps only lamps whoseidentification number is given on the rating plateof the luminaire may be used. In areas containing substances in the explosiongroup IIC, an ignition hazard in the event of abroken lamp already exists when no voltage isapplied. For this reason, fluorescent lamps mayonly be replaced if it is ensured that no explo-sion hazard exists during the relamping of thelight fitting or transport of the lamps.

After completion of the work, • cable ducts must be refilled with sand or

well ventilated and drained,• bushing openings of cables to non-hazar-

dous areas shall be sealed tightly,• unused cable entries in electrical apparatus

must be sealed reliably and safeguardedagainst self-loosening,

• cable glands must be tight.

Repair of apparatusAfter apparatus parts upon which the explosionprotection depends have been repaired, thisapparatus shall be inspected by a recognizedexpert (§ (6) BetrSichV). If the result of theappraisal is positive, he will issue an expert”scertificate or affix a test mark. Only then may theapparatus be put back into operation. Inspec-tion by an expert is not required if the repair ofthe apparatus was carried out by the manufac-turer and the apparatus was submitted to arenewed routine test.


Definition of potentially explosive atmospheres andrequirements for explosion-protected apparatus on theworld market

Summary of the explosion protection measures,standards, categories and classifications thatare applicable worldwide.

On the world market potentially explosiveatmospheres are divided into areas with variousdegrees of hazard according to the IEC publica-tion IEC 60079-10 (EN 60079-10 in Europe) orthe NEC (National Electrical Code).

The following is a brief overview of the NECrequirements and a comparison of the require-ments/specifications to IEC (EN) and NEC.More detailed information can be found in theCrouse-Hinds Code Digest. This publication canbe ordered on the Crouse-Hinds web site”www.crouse-hinds.com” or downloaded as aPDF file.

NEC:

Classification according to the explosive medium

Class I Mixtures of gas or vapour with airClass II Mixture of dust with airClass III Mixture of fibres with air

Subdivision of potentially explosiveatmospheres:

Division 1 Areas in which flammable gasesor vapours can be present:– under normal operating

conditions– frequently in the case of repair

and maintenance work– in the event of breakdowns or

faulty functioning of apparatus orin the process flow if, at thesame time, faults to electricalapparatus can be caused

In class III areas in which fibres orfloating substances can be pre-sent in such quantities that, if theyare whirled-up, they can form anignitable mixture with air belong toDivision 1.

Division 2 Areas in which flammable gases,vapours or easily vaporized liquidsin closed systems or suitable con-tainers are to be found; areas inwhich, under normal operatingconditions, the formation of ignita-ble mixtures is prevented by a for-ced ventilation; areas that borderonto Division 1, so that clouds ofthe explosive atmosphere canoccasionally enter it.

In Class III areas in which easilyflammable fibres are stored orprocesses belong to Division 2.

Division of explosive mixtures intoexplosion groups:

Group A Acetylene

Group B Hydrogen

Group C Ethylene

Group D Propane

Group E Metal dust

Group F Coal dust

Group G Flour dust

Division into temperature classes:

T1 max. 450°CT2 300°CT2A 280°CT2B 260°CT2C 230°CT2D 215°CT3 200°CT3A 180°CT3B 165°CT3C 160°CT4 135°CT4A 120°CT5 100°CT6 085°C

Table of comparison NEC IEC/EN

Hazard categories/gas groups

Examples NEC 500-503 NEC 505

IEC 60079-0

EN 50014

Class I Gases and vapoursAcetylene Group A Group IICHydrogen Group B Group IICEthylene Group C Group IIBPropane Group D Group A

Class II DustsMetal dust Group ECoal dust Group FGrain dust Group G

Class III FibresWood, paper No subdivision

for material processing


Classification of potentially explosive atmospheres

Long-term or Occasional hazard Hazard only in event of frequent hazard fault and short-term

North America NEC 500-503 Division 1 Division 1 Division 2

North America NEC 505 Zone 0 (gas) Zone 1 (gas) Zone 2 (gas)IEC / EN Zone 20 (dust) Zone 21 (dust) Zone 22 (dust)

Apparatus categories to G1 (gas) G2 (gas) G3 (gas)directive 94/9/EN D1 (dust) D2 (dust) D3 (dust)

Division into temperature classes

Maximum permissible surface temperature NEC IEC 60079-0Table 500-3(d) EN 50014

450°C T1 T1300°C T2 T2280°C T2A260°C T2B230°C T2C215°C T2D200°C T3 T3180°C T3A165°C T3B160°C T3C135°C T4 T4120°C T4A100°C T5 T585°C T6 T6

Overview of the types of protection and their permissible use in potentiallyexplosive atmospheres

Type of protection Symbol IEC EN For use in For use in standard standard division zone

General IEC 60079-0 EN 50014requirements

Oil immersion o IEC 60079-6 EN 50015 1 and 2 1 and 2

Pressurization p IEC 60079-2 EN 50016 1 and 2 1 and 2

Sand filling q IEC 60079-5 EN 50017 2 1 and 2

Flameproof enclosure d IEC 60079-1 EN 50018 1 and 2

Increased safety e IEC 60079-7 EN 50019 2 1 and 2

Intrinsic safety i IEC 60079-11 EN 50020 1 and 2 0*,1 and 2

Electrical apparatus n IEC 60079-15 EN 50021 2 2in type of protection ”n”

Encapsulation m IEC 60079-18 EN 50028 1 and 2

Table of comparison NEMA classification and IP degree of protection

NEMA IP

3 IP 543R IP 543S IP 544 and 4X IP 565 IP 526 and 6P IP 6712 and 12 K IP 52


Degrees of protection against water designated by the second code No.Degree of protection

SecondcodeNo. Brief description Definition

0 No special protection –

1 Protected against Vertically falling drops must not have a harmful effect.dripping water

2 Protected against Drops falling vertically must not have a harmful effect dripping water when the enclosure is inclined at an angle up to 15°when the enclosure on either side of the vertical. is inclined up to 15°

3 Protected against Water being sprayed at an angle of up to 60° on spray water either side of the vertical must not have a harmful effect.

4 Protected against Water being splashed against the enclosure from any splash-water direction must have no harmful effect.

5 Protected against Jet water from a nozzle turned on the enclosure from jet water any direction must have no harmful effect.

6 Protected against There must be no harmful effect from powerful water powerful water jets jets being turned on the enclosure from any direction.

7 Protected against Water must not enter in harmful quantities when the water when the enclosure is immersed in water at specified conditionsenclosure is of pressure and time. immersed in water for a specified time

8 Protected against Water must no enter in such a quantity as might have awater when the harmful effect when the enclosure is continuously sub-enclosure is conti- merged in water at conditions which are to be agreednuously submerged upon between the manufacturer and the user. Conditions

must, however, be more stringent than those for code No. 7

Degrees of protection against foreign matter designated by the first code No.Degree of protection

FirstcodeNo. Brief description Definition

0 No special protection –

1 Protected against solid The object probe, a ball of 50 mm dia.foreign bodies 50 mm dia. must not fully penetrate *)and bigger

2 Protected against solid The object probe, a ball of 12.5 mm dia.foreign bodies 12.5 mm dia. must not fully penetrate *)and bigger

3 Protected against solid The object probe of 2.5 mm dia.foreign bodies 2.5 mm dia. must not penetrate at all *)and bigger

4 Protected against solid The object probe of 1 mm dia.foreign bodies 1 mm dia. must not penetrate at all*)and bigger

5 Dust protected Ingress of dust is not totally prevented, but the dust must not enter in such an amount as to interfere with satisfactory operation or with the safety of the apparatus.

6 Dusttight No ingress of dust

*) Note: The full diameter of the object probe must not pass through any opening of the enclosure.

The IP degrees of protection havebeen defined in accordance with EN60529 (protection against accidentalcontact, foreign matter and water):

IP degrees of protection


Table 1 – Procedure for theassessment of the zone classification according to ElexV, directives on explosionprotection (EX-RL) and VDE 0165

1. Are there explosive substances being used?

Yes / No

2. If yes:Do electrical

installations/apparatushave to be taken into

operation ina hazardous area?

If yes, then:

3. Determination of the zone acc. to ElexV, EX-RL

and VDE 0165,whether

Zone 0Zone 1Zone 2Zone 20Zone 21Zone 22

3.1

Clarify:Whichsubstanceswill be used?1. Flash point2. Volume

percent orweight per-cent

3. Density4. Glow

temperature5. Ignition

temperature6. Explosion

group

3.2

Apply dataacc. to 3.1 of EX-RLCheckwhether thepractical caseis in confor-mity with theexample inthe EX-RL;adopt thezone andextent of zone.

3.3

Where appro-priate, refer to otherstandards forzone classifi-cation e. g.VbF/TRbF orothers.

4. Decisionbased on TABLE 2

4.1 Is a type sampletest certificate required?

4.2 Type ofinstallation according

to zone


Table 2 Explosion protection at aglance

Electrical installations in potentially gas atmospheres in the Federal Republic of Germany: Overview in accordance with 94/9/EC, 199/92/EC, ExVO, BetrSichV; EX-RL; VDE 0165

Zone Explosive Flammable Apparatus Electrical installationatmosphere media/substances category

0 Constantly, Gases, vapours, mists 1G to VDE 0165 Part 1

1 Occasionally Gases, vapours, mists 2G to VDE 0165 Part 1

2 Not to be expected, Gases, vapours, mists 3G to VDE 0165 Part 1 for short periods

20 Constantly, Dusts 1D to VDE 0165 Part 2for long periods

21 Occasionally Dusts 2D to VDE 0165 Part 2

22 Not to be expected, Dusts 3D* to VDE 0165 Part 2for short periods

* For conductive dusts IP 66 required


Appendix 3 – Sample of an installationcertificate

Installationcertificate 1)

Complies with the rule of prevention of accidents”Electrical installations and apparatures (BGV A2)“

Complies to German regulation for safety provisions(BetrSichV. § 14 (1) – (3))

The installation set up by us

electrical installation up to 1000 V

Date: Order-No.:

Building: Plant:

Is set up in accordance to the engineering documents in attention to the rules of technique.

The tests required in the order are accomplished.

The accordiner inspection sheets are listed.

________________ _________________Place, Date Signature

1) Up to final regulation


Hot work permit for hazardous areasTick off where applicable. Delete what is not applicable in lines ticked off.

Permit for welding, burning and other hot work, for drilling, grinding, impact and calking work, for the use of non-explosionprotected apparatus.

A 1. Contractor: Building: Tel.: Foreman:2. Place and kind of work

3. Hot work permit from o’clock to o’clock, for the time4. For workshop/Messrs Building Foreman:

B Dangerous places in the environmentof the workplace, buildings, equipment etc. Person responsible Building Tel.

1.

2.

3.

4.

C Security precautions To be executed by: Settled 1. Checking the tightness of pipes, equipment in the environment of the workplace 2. Fire fighting and other security precautions a. Placing in readiness at the workplace of water for fire fighting and fire extinguishers b. Connecting the fire hose c. Placing look-out man

craftsman staff member supervisor fireman d. Removal of inflammable substances, vapours, gases or dust deposits e. f.

3. Signposting of the workplace (road, railroad tracks etc.) a. By means of red flags (20 m on either side of the workplace) b. By means of signs (e.g. hot work on pipe bridge) c. Blockage, diversion for tank lorries, blockage for rail cars

4. Protection of the environment from welding sparks a. Covering of the adjacent conduits b. Setting up of a protective wall, protection of the roof surface, possibly keeping wet c. Stopping of hot work with running of trains d. Keeping a min.distance of m from tank wagons, tank farms etc. with fire hazard e. Covering and sealing of pipe openings, gratings, light wells and gully holes f.

5. In case of hot work in and on containers, apparatus, pits, pipework, dismantled parts of installations, in confined rooms etc. Additional measures such as:

a. Travelling permit No. dated b. Work permit No. dated c. Test certificate for electrical apparatus No. dated d.

6. a. Before starting to work, daily report to B 1, 2, 3, 4. b. Report end of the work daily to B 1, 2, 3, 4.

7. a. Check of the security precautions ticked off by (name) b. Check of the workplace after ending the work by (name)

C Consent of responsibilities Starting time reportedfor the dangerous places on: to:For B 1 measures C figureFor B 2 measures C figureFor B 3 measures C figureFor B 4 measures C figure

Date Signatures

Hot work permit issuedDate Signature of the works supervisor or his mandatary

Look-out man (name)

Annex 2 –Sample of a hot workpermit


Annex 3Bibliography

Title Author Obtainable from

”Explosion protection: Commentary on Fähnrich Ralph/Mattes, Hatto. Erich Schmidt Verlag GmbH, BerlinExVO and BetrSichV”ISBN 3-503-01881-6

”ZH 1/10 Rules on health and safety protection at work; Employers´ Liability Insurance Jedermann-Verlag, Heidelberg;Explosion protection rules” Company of the Chemical Industry Werbe Druck Winter, Sandhausen

Electrical explosion protection to Linienklaus, Erich/ VDE Verlag, BerlinDIN VDE 0165 (VDE Publication, Volume 65) Wettingfeld, Klaus ISBN 3-8007-2410-3

Esplosion protection by intrinsic safety Dose, Wolf-Dieter VDE Verlag, BerlinISBN 3-8007-1950-9

”VDE regulations: Selection for explosion protection;2004-03” VDE VDE Verlag Berlin

Explosion protection manual Steen, Hennikus Wiley-VCH VerlagISBN 3-5272-9848-7

Electrical installations and equipment in Olenik, Heinz/Dose, Wolf-Dieter/ Hüthig & Pflaum Verlag, Heidelbergpotentially explosive atmospheres Rading, Herbert F. ISBN 3-8101-0130-3

Explosion-protected electrical installations Pester, Johannes Verlag TechnikISBN 3-3410-1174-9

Mining decree on the general certification Gazette No. 54, Part 1 Bundesanzeiger Verlags mbHof firedamp-protected electrical apparatus (1983)(mining decree on the approval of electrical apparatus– ElZulBergV)

The new equipment safety law (1980) Jeiter, W. Verlag C. H. Beck, MunichISBN 3-4063-7260-0

Safety coefficients of flammable gases and vapours; Narbert, K./Schön, G. Deutscher Eichverlag GmbHBraunschweig

Directives for the prevention of ignition hazards Central union of the Employers Carl Heymanns Verlag KG, as a result of electrostatic charges – Liability Insurance Association, CologneDirectives ”Static electricity” BER 132 Central Office for

Industrial Medicine,Bonn

New procedure for the testing and certification Dreier H./Hofer D. PTB Info No. 4 (1980)of explosion-protected electrical apparatus



EN 1127: 1997 CEN VDE-Verlag GmbHExplosive atmospheres – Explosion prevention and protection – 10625 BerlinPart 1: Basic concepts and methodology

EN 1127-2: 2002 CEN VDE-Verlag GmbHExplosive atmospheres – Explosion prevention and protection – 10625 BerlinPart 2: Basic concepts and methodology for mining

EN 1755: 2000 CEN VDE-Verlag GmbHSafety of industrial trucks – Operation in potentially 10625 Berlinexplosive atmospheres – Use in flammable gas, vapourmist and dust

EN 1834-1: 2000 CEN VDE-Verlag GmbHReciprocating internal combustion engines – Safety requirements 10625 Berlin

for design and construction of engines for use in potentially explosive atmospheres – Part 1: Group II engines for use in flammable gas and vapour atmospheres

EN 1834-2: 2000 CEN VDE-Verlag GmbHReciprocating internal combustion engines – Safety requirements 10625 Berlinfor design and construction of engines for use inpotentially explosive atmospheres – Part 2: Group Iengines for use in underground workings susceptible to firedamp and/or combustible dust

EN 1834-3: 2000 CEN VDE-Verlag GmbHReciprocating internal combustion engines – Safety requirements 10625 Berlinfor design and construction of engines for use inpotentially explosive atmospheres – Part 3: Group IIengines for use in flammable dust atmospheres

EN 12847: 2001 CEN VDE-Verlag GmbHFlame arresters – Performance requirements, test methods 10625 Berlinand limits for use

EN 13012: 2001 CEN VDE-Verlag GmbHPetrol filling stations – Construction and performance of 10625 Berlinautomatic nozzles for use on fuel dispensers

EN 13160-1 : 2001 CEN VDE-Verlag GmbHLeak detection systems – Part 1: General Principles 10625 Berlin

EN 13237 : 2003 CEN VDE-Verlag GmbHPotentially explosive atmospheres – Terms and definitions 10625 Berlinfor equipment and protective systems intended for use inpotentially explosive atmospheresEN 13463-1 : 2001 CEN VDE-Verlag GmbHNon-electrical equipment for potentially explosive atmospheres – 10625 BerlinPart 1: Basic methodology and requirements

EN 13673-1 : 2003 CEN VDE-Verlag GmbHDetermination of the maximum explosion pressure and the 10625 Berlinmaximum rate of pressure rise of gases and vapours – Part 1: Determination of the maximum explosion pressure

EN 13760: 2003 CEN VDE-Verlag GmbHAutomotive LPG filling system for light and heavy duty 10625 Berlinvehicles – Nozzle, test requirements and dimensions

EN 13821: 2002 CEN VDE-Verlag GmbHPotentially explosive atmospheres – Explosion prevention 10625 Berlinand protection – Determination of minimum ignition energyof dust/air mixtures

EN 13980: 2002 CEN VDE-Verlag GmbHPotentially explosive atmospheres – 10625 BerlinApplication of quality systems

Annex 4Harmonized standards toDirective 94/9/EC



EN 50014: 1997 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 0625 BerlinGeneral requirementsAmendment A1:1999 to EN 50014:1997 Note 3 – Amendment A2:1999 to EN 50014:1997 Note 3 –

EN 50015: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 10625 BerlinOil immersion ”o”

EN 50017: 1998 CENELEC VDE-Verlag GmbHElektrische Betriebsmittel für explosionsgefährdete Bereiche – 10625 BerlinPowder filling ”q”

EN 50018: 2000 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 10625 BerlinFlameproof enclosure ”d”Amendment A1:2002 to EN 50018:2000

EN 50019 / EN 60079-7 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 10625 BerlinIncreased safety ”e”+ Corrigendum 4.2003

EN 50020 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 10625 BerlinIntrinsic safety ”i”

EN 50021 / EN 60079-15 CENELEC VDE-Verlag GmbHElectrical apparatus for potentially explosive atmospheres – 10625 BerlinType of protection ”n”

EN 50054 / EN 61779-1 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlincombustible gases – General requirements and test methods

EN 50055 / EN 61779-2 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlincombustible gases – Performance requirements for Group Iapparatus indicating up to 5 % (v/v) methane in air

EN 50056: 1998 CENELEC VDE- Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlincombustible gases – Performance requirements for Group Iapparatus indicating up to 100 % (v/v) methane in air

EN 50057: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlincombustible gases – Performance requirements for GroupII apparatus indicating up to 100 % lower explosive limit

EN 50058: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlincombustible gases – Performance requirements for GroupII apparatus indicating up to 100 % (v/v) gas

EN 50104: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinoxygen – Performance requirements and test methods

EN 50104: 2002 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinoxygen – Performance requirements and test methodsAmendment A1:2004 to EN 50104: 2002

EN 50241-1: 1999 CENELEC VDE-Verlag GmbHSpecification for open path apparatus for the detection of 10625 Berlincombustible or toxic gases and vapours – Part 1: Generalrequirements and test methods




EN 50241-2: 1999 CENELEC VDE-Verlag GmbHSpecification for open path apparatus for the detection of 10625 Berlincombustible or toxic gases and vapours – Part 2:Performance requirements for apparatus for the detection ofcombustible gases

EN 50281-1-1: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for use in the presence of combustible 10625 Berlindust – Part 1-1: Electrical apparatus protected by enclosures – Construction and testing+ Corrigendum 8.1999Amendment A1:2002 to EN 50281-1-1:1998

EN 50281-1-2: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for use in the presence of combustible 10625 Berlindust – Part 1-2: Electrical apparatus protected by enclosuresSelection, installation and maintenance – + Corrigendum 12.1999Amendment A1:2002 to EN 50281-1-2:1998

EN 50281-2-1: 1998 CENELEC VDE-Verlag GmbHElectrical apparatus for use in the presence of combustible 10625 Berlindust – Part 2-1: Test methods – Methods for determiningthe minimum ignition temperatures of dust

EN 50284: 1999 CENELEC VDE-Verlag GmbHSpecial requirements for construction, test and marking of 10625 Berlinelectrical apparatus of equipment group II, Category 1 G

EN 50303: 2000 CENELEC VDE-Verlag GmbHGroup I, Category M1 equipment intended to remain functional 10625 Berlinin atmospheres endangered by firedamp and/or coal dust

EN 60079-7: 2003 CENELEC VDE-Verlag GmbHElectrical apparatus for explosive gas atmospheres – Part 7: 10625 BerlinIncreased safety ”e”(IEC 60079-7:2001, EN 50019:2000)

EN 60079-15:2003 CENELEC VDE-Verlag GmbHElectrical apparatus for explosive gas atmospheres – Part 15: 10625 BerlinType of protection ”n”(IEC 60079-15:2001, EN 50021:1999)

EN 61779-1:2000 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement 10625 Berlinof flammable gases – Part 1: General requirements and test methods (IEC 61779-1:1998 EN 50054:1998)Amendment A11:2004 to EN 61779-1:2000

EN 61779-2:2000 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinflammable gases – Part 2: Performance requirements for group I apparatus indicating a volume fraction up to 5 % methane in air(IEC 61779-2:1998, EN 50055:1998)

EN 61779-3:2000 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinflammable gases – Part 3: Performance requirements for group I apparatus indicating a volume fraction up to 100 % methane in air (IEC 61779-3:1998, EN 50056:1998)




EN 61779-4:2000 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinflammable gases – Part 4: Performance requirements for 10625 Berlingroup II apparatus indicating a volume fraction up to 100 % lower explosive limit(IEC 61779-4:1998, EN 50057:1998)

EN 61779-5:2000 CENELEC VDE-Verlag GmbHElectrical apparatus for the detection and measurement of 10625 Berlinflammable gases – Part 5: Performance requirements for group II apparatus indicating a volume fraction up to 100 % gas(IEC 61779-5:1998, EN 50058:1998)

EN 62013-1:2002 CENELEC VDE-Verlag GmbHCaplights for use in mines susceptible to firedamp – 10625 BerlinPart 1: General requirements - Construction and testing in relation to the risk of explosion (IEC 62013-1:1999)



All rights reserved, in particular the right to reproduce and circulate, as well as the right to translate.

The data was compiled and verified with due care in keeping with the latest standardsand regulations. The prevailing technological and statutory rules are binding.

© 2004 Cooper Crouse-Hinds GmbHSenator-Schwartz-Ring 26D-59494 Soest/Germany

No liability will be assumed for any damages that may arise from the use of thisdata.

Setting: Scholz-Druck, DortmundPrinting: Scholz-Druck, Dortmund

Publication No.1258/8/07.04/SDPrinted in the Federal Republic of Germany

Cooper Crouse-Hinds GmbHNeuer Weg-Nord 49, D-69412 EberbachPhone +49 (0) 62 71/806-5 00, Fax +49 (0) 62 71/806-4 76Internet www.ceag.dee-mail [email protected]

All you need for explosion protection from one source

Explosion-protected

Fluorescent light fittings

Floodlights

Portable lamps

Plugs and sockets

Switchgear

Terminal boxes

Intrinsically safe signal conditioning

eXLink

3008

0001

258/

4/07

.04/

SD

Tech

nica

l det

ails

sub

ject

to a

ltera

tion

Principle of Explosion Protection

Documents

Transcript of Principle of Explosion Protection