BS EN 50016

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BRITISH STANDARD BS EN 50016:2002 Electrical apparatus for potentially explosive atmospheres — Pressurized apparatus “p” The European Standard EN 50016:2002 has the status of a Britis h Standard ICS 29.260.20  

description

BS EN 50016

Transcript of BS EN 50016

  • BRITISH STANDARD BS EN 50016:2002

    Electrical apparatus for potentially explosive atmospheres Pressurized apparatus p

    The European Standard EN 50016:2002 has the status of a British Standard

    ICS 29.260.20

  • BS EN 50016:2002

    This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 7 August 2002

    BSI 7 August 2002

    ISBN 0 580 40249 5

    National forewordThis British Standard is the official English language version of EN 50016:2002. It supersedes BS EN 50016:1996 which will be withdrawn on 2003-06-30.

    The UK participation in its preparation was entrusted by Technical Committee GEL/31, Electrical apparatus for explosive atmospheres, to Subcommittee GEL/31/17, Pressurization and other techniques, which has the responsibility to:

    A list of organizations represented on this committee can be obtained on request to its secretary.

    Cross-referencesThe British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled International Standards Correspondence Index, or by using the Search facility of the BSI Electronic Catalogue or of British Standards Online.

    This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

    Compliance with a British Standard does not of itself confer immunity from legal obligations.

    aid enquirers to understand the text;

    present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed;

    monitor related international and European developments and promulgate them in the UK.

    Summary of pagesThis document comprises a front cover, an inside front cover, the EN title page,pages 2 to 30, an inside back cover and a back cover.

    The BSI copyright date displayed in this document indicates when thedocument was last issued.

    Amendments issued since publication

    Amd. No. Date Comments

  • EUROPEAN STANDARD EN 50016NORME EUROPENNE

    EUROPISCHE NORM July 2002

    CENELECEuropean Committee for Electrotechnical Standardization

    Comit Europen de Normalisation ElectrotechniqueEuropisches Komitee fr Elektrotechnische Normung

    Central Secretariat: rue de Stassart 35, B - 1050 Brussels

    2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

    Ref. No. EN 50016:2002 E

    ICS 29.260.20 Supersedes EN 50016:1995

    English version

    Electrical apparatus for potentially explosive atmospheres Pressurized apparatus "p"

    Matriel lectrique pour atmosphresexplosibles Surpression interne "p"

    Elektrische Betriebsmittel frexplosionsgefhrdete Bereiche berdruckkapselung "p"

    This European Standard was approved by CENELEC on 1999-10-01. CENELEC members are bound tocomply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving thisEuropean Standard the status of a national standard without any alteration.

    Up-to-date lists and bibliographical references concerning such national standards may be obtained onapplication to the Central Secretariat or to any CENELEC member.

    This European Standard exists in three official versions (English, French, German). A version in anyother language made by translation under the responsibility of a CENELEC member into its ownlanguage and notified to the Central Secretariat has the same status as the official versions.

    CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

  • EN 50016:2002 - 2 -

    Foreword

    This European Standard was prepared by SC 31-7, Pressurization and other techniques, of the TechnicalCommittee CENELEC TC 31, Electrical apparatus for explosive atmospheres.

    It consists of the text of EN 50016:1995 and a new amendment (prA1:1999) which was submitted to theformal vote in April 1999 and was approved by CENELEC on 1999-10-01 for publication as a new edition ofthis European Standard.

    This European Standard supersedes EN 50016:1995.

    The European Standard was prepared under a mandate given to CENELEC by the European Commissionand the European Free Trade Association and covers essential requirements of the EC Directive 94/9/EC.

    This European Standard is to be read in conjunction with EN 50014:1997 - Electrical apparatus forpotentially explosive atmospheres General requirements, and with the European Standards for thespecific types of protection listed in the scope of EN 50014:1997. This European Standard should not beconsidered in conjunction with any editions of these standards and their amendments published before1997.

    The following dates were fixed:

    latest date by which the EN has to be implementedat national level by publication of an identicalnational standard or by endorsement (dop) 2003-02-01

    latest date by which the national standards conflictingwith the EN have to be withdrawn (dow) 2003-06-30

    Annexes designated normative are part of the body of the standard. Annexes designated informative aregiven only for information. In this standard annex D is normative and annexes A, B and C are informative.

    _________

  • - 3 - EN 50016:2002

    Contents

    Page

    1 Scope......................................................................................................................................... 42 Normative references................................................................................................................ 43 Definitions................................................................................................................................. 5

    REQUIREMENTS FOR PRESSURIZED ENCLOSURES

    4 Enclosures and ducting ........................................................................................................... 75 Temperature limits.................................................................................................................... 96 Safety provisions and safety devices (except for static pressurization)............................... 97 Safety provisions and safety devices for static pressurization ............................................. 118 Supply of protective gas ......................................................................................................... 12

    ADDITIONAL REQUIREMENTS FOR PRESSURIZED ENCLOSURES WITH CONTAINMENT SYSTEMS

    9 Introduction ............................................................................................................................. 1210 Release conditions ................................................................................................................... 1211 Design requirements for the containment system.................................................................. 1312 Protective gas and pressurizing technique............................................................................. 1413 Ignition capable apparatus....................................................................................................... 1614 Internal hot surfaces................................................................................................................. 16

    VERIFICATION AND TESTS

    15 Type verification and tests....................................................................................................... 1716 Routine tests............................................................................................................................. 21

    MARKING

    17 Marking ..................................................................................................................................... 21

    ANNEXES

    Annex A (informative) Ducting of protective gas.............................................................................. 23Annex B (informative) Infallibility test for a containment system.................................................... 28Annex C (informative) Function test of surveillance circuits .......................................................... 29Annex D (normative) Purging and dilution tests .............................................................................. 30

  • EN 50016:2002 - 4 -

    1 Scope

    1.1 This European Standard specifies the requirements for the construction and testing of pressurizedand purged electrical apparatus and Ex components forming part of the pressurized apparatus, with typeof protection p, intended for use in potentially explosive atmospheres of gas vapour and mist.

    1.2 This European Standard supplements EN 50014 in so far as it applies to pressurized and purgedelectrical apparatus with type of protection p.

    1.3 This European Standard is applicable to electrical equipment and components of Group I CategoryM2 and of Group IIG Category 2 using the technique of pressurize and purge.

    NOTE In this European Standard, the word apparatus has the same meaning as the word equipment in Directive 94/9/EC.

    1.4 This European Standard includes the requirements for the construction of the enclosure and itsassociated components, including, if any, the inlet and outlet ducts for the protective gas, and for the safetyprovisions and devices necessary for the type of protection pressurization p.

    1.5 This European Standard specifies the requirements for pressurized enclosures with or without aninternal source of release, with the exceptions given in 1.7 and 1.8.

    1.6 This European Standard specifies requirements for pressurized enclosures containing an unlimitedsource of release of flammable gas or vapour only where the unlimited source of release is from the surfaceof a liquid.

    1.7 This European Standard does not contain requirements for pressurized rooms or analyser houses (forwhich another standard is in preparation).

    1.8 This European Standard does not contain the requirements for pressurized enclosures where, in acontainment system with limited or unlimited release there is:

    a) air with an oxygen content greater than normal, or

    b) oxygen in combination with inert gas in a proportion greater than 21 %.

    1.9 Due to the safety factors incorporated in the type of protection the uncertainty of measurementinherent in good quality, regularly calibrated measurement equipment is considered to have no significantdetrimental effect and need not be taken into account when making the measurements necessary to verifycompliance of the apparatus with the requirements of this standard.

    2 Normative references

    This European Standard incorporates, by dated or undated reference, provisions from other publications.These normative references are cited at the appropriate places in the text and the publications are listedhereafter. For dated references, subsequent amendments to or revisions of any of these publications applyto this European Standard only when incorporated in it by amendment or revision. For undated referencesthe latest edition of the publication referred to applies (including amendments).

    EN 50014 1997 Electrical apparatus for potentially explosive atmospheres General requirementsA1 1999A2 1999

    EN 50015 Electrical Apparatus for potentially explosive atmospheres Oil immersion o

    EN 50017 Electrical apparatus for potentially explosive atmospheres Powder filling q

  • - 5 - EN 50016:2002

    EN 50018 Electrical apparatus for potentially explosive atmospheres Flameproofenclosures d

    EN 50019 Electrical apparatus for potentially explosive atmospheres Increased safety e

    EN 50020 Electrical apparatus for potentially explosive atmospheres Intrinsic safety i

    EN 50028 Electrical apparatus for potentially explosive atmospheres Encapsulation m

    EN 50033 Electrical apparatus for potentially explosive atmospheres Caplights for minessusceptible to firedamp

    EN 50039 Electrical apparatus for potentially explosive atmospheres Intrinsically safesystems i

    EN 954 Series Safety of machinery Safety related parts of control systems

    EN 60034-1 1998 Rotating electrical machines Rating and performance(IEC 60034-1:1996, modified)

    EN 60034-5 1986 Rotating electrical machines Part 5: Classification of degrees of protectionprovided by enclosures for rotating machines(IEC 60034-5:1981, modified)

    EN 60529 1991 Degrees of protection provided by enclosures (IP Code)(IEC 60529:1989)

    HD 214 S2 1980 Method for determining the comparative and the proof tracking indices of solidinsulating materials under moist conditions(IEC 60112:1979)

    3 Definitions

    For the purposes of this European Standard, the definitions of EN 50014 and also the following apply.

    3.1type of protection pressurization ptechnique of applying a protective gas to an enclosure in order to prevent the formation of an explosiveatmosphere inside the enclosure by maintaining an overpressure against the surrounding atmosphere, andwhere necessary by using dilution

    3.2pressurized enclosureenclosure in which a protective gas is maintained at a pressure greater than that of the external atmosphere

    3.3protective gasair or inert gas used for purging and maintaining an overpressure and, if required, dilution

    NOTE For the purpose of this standard inert gas means nitrogen, carbon dioxide, argon or any gas which, when mixed with oxygen in theratio 4:1 as found in air, does not make the ignition and flammability properties, such as explosive limits, more onerous.

  • EN 50016:2002 - 6 -

    3.4purgingoperation of passing a quantity of protective gas through the pressurized enclosure and ducts, so that:

    a) when the protective gas is air, any explosive atmosphere in the pressurized enclosure is reduced to asafe concentration;

    b) or when the protective gas is inert the concentration of oxygen in the pressurized enclosure is reducedto a safe level

    3.5static pressurizationmaintenance of an overpressure within a pressurized enclosure without the addition of protective gas in ahazardous area

    3.6pressurization with leakage compensationmaintenance of an overpressure within a pressurized enclosure so that, when the outlet apertures areclosed, the supply of protective gas is sufficient to compensate for any leakage from the pressurizedenclosure and its ducts

    3.7pressurization with continuous flow of the protective gasmaintenance of an overpressure within a pressurized enclosure with continuous flow of the protective gasthrough the enclosure

    3.8internal source of releasepoint or location from which a flammable substance in the form of a flammable gas or vapour or liquid maybe released into the pressurized enclosure such that in the presence of air an explosive gas atmospherecould be formed

    3.9containment systempart of the apparatus containing the flammable gas, vapour or liquid that may constitute an internal sourceof release

    3.10infallible containment systemconstruction of an infallible containment system is of such integrity that the possibility of a leak is so remotethat it can be ignored

    3.11dilutioncontinuous supply of a protective gas, after purging, at such a rate that the concentration of a flammablemixture inside the pressurized enclosure is maintained at a value outside the explosive limits except in adilution area

    NOTE Dilution of oxygen by inert gas may result in a concentration of flammable gas above the UEL.

    3.12ignition capable apparatusapparatus which in normal operation constitutes a source of ignition for a specified explosive atmosphere.This includes electrical apparatus not protected by a type of protection listed in clause 2

  • - 7 - EN 50016:2002

    3.13dilution areaarea in the vicinity of a source of release where the concentration of flammable gas or vapour is not dilutedto a safe concentration

    3.14limited releaserelease of flammable gas or vapour the maximum flow rate of which can be predicted

    3.15unlimited releaserelease of flammable gas or vapour the maximum flow rate of which cannot be predicted

    NOTE This refers to liquids which can evolve flammable gas or vapour where the rate of release cannot be predicted.

    3.16lower explosive limit (LEL)volume ratio of flammable gas or vapour in air below which an explosive gas atmosphere will not be formed

    3.17upper explosive limit (UEL)volume ratio of flammable gas or vapour in air above which an explosive gas atmosphere will not be formed

    3.18volume ratio (v/v)ratio of the volume of a component to the volume of the gas mixture under specified conditions oftemperature and pressure

    REQUIREMENTS FOR PRESSURIZED ENCLOSURES

    4 Enclosures and ducting

    4.1 General

    The pressurized enclosure, including any apertures for moving parts but excluding apertures for the inletand outlet of the protective gas, shall have a degree of protection in accordance with at least IP 40 ofEN 60529, or in the case of a rotating electrical machine, EN 60034-5.

    NOTE The degree of protection of IP 44 may be required on a coal face under humid and dusty conditions.

    4.2 Spark and particle barriers

    The pressurized enclosure and the ducting, if any, for the protective gas shall guard against the ejection ofignition capable sparks or particles into the hazardous area (see A.2).

    4.3 Mechanical strength

    The pressurized enclosure, ducts if any, and their connecting parts shall withstand a pressure equal to1,5 times the maximum overpressure specified by the manufacturer for normal service with all outletsclosed with a minimum of 200 Pa.

    If a pressure can occur in service that can cause a deformation of the enclosure, ducts if any, or connectingparts, a safety device shall be fitted by the manufacturer to limit the maximum internal overpressure to alevel below that which could adversely affect the type of protection.

  • EN 50016:2002 - 8 -

    4.4 Apertures

    NOTE The location, size and number of apertures should be suitable for effective purging. The number of apertures should be chosen withregard to the design and disposition of the apparatus, particular consideration being given to the needs of subcompartments into which theapparatus might be divided.

    4.4.1 In the case of static pressurization the enclosure shall have one or more apertures. After filling andpressurization all apertures shall be closed.

    4.4.2 In the case of pressurization with leakage compensation the enclosure shall have one or more inletapertures. It shall also have one or more outlet apertures constructed so that they can be closed afterpurging.

    4.4.3 In the case of pressurization with continuous flow of protective gas, the enclosure shall have one ormore inlet apertures and one or more outlet apertures for the connection of the inlet and outlet ducts for theprotective gas.

    4.5 Materials

    The materials used for the enclosure, ducts and connecting parts shall not be adversely affected by thespecified protective gas.

    4.6 Doors and covers

    4.6.1 Group I apparatus: For Group I pressurized enclosures, doors and covers shall either:

    have special fasteners complying with 9.2 of EN 50014; or

    except for the case of static pressurization, be interlocked so that the electrical supply to apparatus notprotected by a type of protection listed in clause 2 of this standard is disconnected automatically whenthey are opened and so that the supply cannot be restored until they are closed. The requirements of 6.6of this standard shall also apply.

    In the case of static pressurization, doors and covers shall carry the following warning:

    Do not open in hazardous area

    4.6.2 Group II apparatus: The requirements for fasteners for doors and covers in 9.1, paragraph 1, ofEN 50014 need not apply to Group II pressurized enclosures. Doors and covers, except for those which canbe opened only by the use of a tool or key, shall be interlocked so that the electrical supply to electricalapparatus not protected by a type of protection listed in clause 2 of this standard is disconnectedautomatically when they are opened and so that the supply cannot be restored until they are closed. Therequirements of 6.6 of this standard shall also apply.

    In the case of static pressurization, doors and covers shall only be opened by the use of a tool, and shallcarry the following warning:

    Do not open in hazardous area

    4.6.3 When doors and covers are provided to permit inspection in service, they shall carry the followingwarning:

    Do not open when energized

    except where provision is made for adjustment during operation, in which case the warning shall be

    See instructions before opening

  • - 9 - EN 50016:2002

    4.7 Insulating materials

    For Group I apparatus, insulating materials subjected to electrical stresses capable of causing arcs in airand which result from rated currents of more than 16 A shall have a comparative tracking index equal to orgreater than CTI 400M according to IEC 60112.

    5 Temperature limits

    5.1 The pressurized enclosure shall be classified in accordance with the temperature classificationrequirements of EN 50014.

    The maximum surface temperature shall be determined either:

    a) by the temperature of the hottest point of the external surface of the enclosure; or

    b) by the temperature of the hottest point of the surface of the internal parts which are protected by any ofthe types of protection listed in EN 50014, and which remain energized even when the supply ofprotective gas is removed (e.g. electrical heaters).

    5.2 If during normal service the temperature of any surface within the pressurized enclosure exceeds themaximum value permitted in EN 50014 for the temperature class, appropriate measures shall be taken toprevent, if pressurization ceases, any explosive atmosphere which may exist making contact with thatsurface before it has cooled below the permitted maximum value. This may be achieved either by thedesign and construction of the joints of the pressurized enclosure and ducts or by other means, e.g. bybringing auxiliary ventilation systems into operation or by arranging that the hot surface within the enclosureis in a gas tight or encapsulated housing.

    When determining the temperature for rotating electrical machines the duty type according to EN 60034-1as specified by the manufacturer shall be considered.

    6 Safety provisions and safety devices (except for static pressurization)

    6.1 All safety devices used to prevent electrical apparatus protected by pressurization from causing anexplosion shall themselves not be capable of causing an explosion or shall be mounted outside thehazardous area.

    6.2 The safety devices required by this standard form safety related parts of a control system. It is theresponsibility of the manufacturer to assess that the safety and integrity of the control system is consistentwith the level of safety required by this standard.

    NOTE See also EN 954, Safety of machinery Safety related parts of a control system.

    6.3 The safety devices shall be provided by the manufacturer of the apparatus or by the user. In the lattercase the apparatus shall be marked X and the description documents shall contain all necessaryinformation required by the user to ensure conformity with the requirements of this standard.

    NOTE An example of the information to be supplied by the manufacturer is given in annex C.

    6.4 Where the safety related control system forms part of the apparatus a functional sequence diagramshall be provided by the manufacturer, for example truth table, state diagram, flow chart, etc., to define theaction of the control system. The sequence diagram shall clearly identify and show the operational states ofthe safety devices and ensuing actions. Functional tests shall be required to verify conformity to thediagram. These tests need only be carried out under normal atmospheric conditions unless otherwisespecified by the manufacturer.

  • EN 50016:2002 - 10 -

    6.5 The manufacturer shall specify the maximum and minimum action levels and tolerances of the safetydevices. The safety devices shall be used within the normal operational limits as specified by themanufacturer taking due account of the most onerous conditions specified for normal service.

    6.6 Safety devices, such as time delay relays and devices for monitoring the flow of protective gas shallbe provided to prevent electrical apparatus within a pressurized enclosure becoming energized until purginghas been completed.

    The sequence of operations of the safety devices shall be as follows:

    following the initiation of the sequence, the purging flow through and the overpressure in the enclosureshall be monitored in accordance with this standard;

    when the minimum flowrate of protective gas is achieved and the overpressure is within the specifiedlimits the purge timer can be started;

    after the expiry of the time the apparatus is then available to be energized.

    In the event of failure of any step in the sequence the circuit shall be arranged to reset to the beginning.

    6.7 Where the protective gas is air, the concentration of flammable gas after purging shall not exceed25 % of the LEL.

    Where the protective gas is other than air, the concentration of oxygen after purging shall not exceed 2 %by volume.

    The minimum flow rate of protective gas required for purging is the rate specified by the manufacturer andverified by the type tests in 15.3 and 15.4. The minimum purging duration is the duration also specified bythe manufacturer and verified by the type tests. The purging flow rate shall be monitored at the outlet of thepressurized enclosure.

    NOTE To determine the free space of the associated ducts and to set up the additional purging time for the given minimum flowrate is theresponsibility of the user. The purge duration shall be increased by the time necessary to purge the free volume of those associated ductswhich are not part of the certified apparatus by at least five times their volume at the minimum flow rate specified by the manufacturer.

    6.8 One or more automatic safety devices shall be provided to operate when the overpressure falls belowthe minimum value specified by the manufacturer. It shall be possible to check the correct operation of thesafety devices. Their location and setting shall take into account the requirements of 6.9.

    When a minimum rate of flow of protective gas is specified by the manufacturer one or more automaticsafety device(s) shall be provided to operate when the flow rate of protective gas at the outlet falls below thespecified minimum value.

    NOTE The purpose(s) for which the automatic safety device(s) are used (i.e. to disconnect power or to sound an alarm or otherwise ensurethe safety of the installation) is the responsibility of the user.

    6.9 A minimum overpressure of 50 Pa shall be maintained relative to the external pressure at every pointwithin the enclosure and its associated ducts, at which leakage can occur.

    The manufacturer shall specify the minimum and maximum overpressure in service and the maximumleakage rate at the maximum overpressure.

    The distribution of pressure in different systems and ducts is illustrated in Figures A.1 to A.4.

    NOTE It is essential for the safety of an installation of pressurized enclosures that the installation of the associated ducts and of thecompressor or fan does not introduce a hazard. The basic recommendations for the installation of ducting systems are given in annex A.

    For variable speed motors, consideration must be given to the operational speed range to determine theposition and pressurization of the minimum pressure point within the enclosure.

  • - 11 - EN 50016:2002

    6.10 When a source of protective gas is common to a number of separate enclosures, the safety device ordevices may be common to several of these, provided that the resulting control takes account of the mostunfavourable conditions in the group of enclosures. When a common safety device is fitted, the opening ofa door or cover need not switch off all the electrical apparatus in the enclosures or initiate the alarm,provided that the following three conditions are met:

    a) the opening of the door or cover is preceded by disconnecting the supply to the electrical apparatus inthe particular pressurized enclosure, except electrical apparatus protected by any of the types ofprotection listed in clause 2 of this standard;

    b) the common safety device continues to monitor the overpressure in, and where necessary the flowthrough, all the other pressurized enclosures of the group;

    c) the subsequent connecting of the supply to the electrical apparatus in the particular pressurizedenclosure is preceded by the purging procedure specified in 6.6.

    6.11 Electrical apparatus within the pressurized enclosure that may be energized when type of protectionpressurization p, is not in operation, shall be protected by a type of protection listed in clause 2 of thisstandard.

    7 Safety provisions and safety devices for static pressurization

    7.1 All safety devices used to prevent electrical apparatus protected by pressurization from causing anexplosion shall themselves not be capable of causing an explosion or shall be mounted outside thehazardous area.

    7.2 The protective gas shall be inert. The concentration of oxygen after filling with inert gas shall be lessthan 1 % by volume.

    7.3 Internal sources of release of flammable substances are not permitted.

    7.4 The pressurized enclosure shall be filled with inert gas in a non-hazardous area using the procedurespecified by the manufacturer.

    7.5 Two automatic safety devices shall be provided to operate when the overpressure falls below theminimum value specified by the manufacturer. It shall be possible to check the correct operation of thedevices when the apparatus is in service. The automatic safety devices shall only be capable of being resetby the use of a tool or a key.

    NOTE The purpose for which the automatic safety devices are used (i.e. to disconnect power or to sound an alarm or otherwise ensuresafety of the installation) is the responsibility of the user.

    7.6 Electrical apparatus within the pressurized enclosure that may be energized when type of protectionpressurization p is not in operation, shall be protected by a type of protection listed in clause 2 of thisstandard.

    7.7 The minimum level of overpressure shall be greater than the maximum pressure loss in normalservice measured over a period not less than 100 times the time necessary for the cooling of enclosedcomponents according to 6.2 of EN 50014 with a minimum of 1 h. The minimum level of overpressure shallnot be less than 50 Pa above the external pressure under the most onerous conditions specified for normalservice.

    NOTE If the overpressure falls below the minimum specified, it is the users responsibility to ensure that the pressurized enclosure isremoved to a non-hazardous area before refilling.

    For variable speed motors, consideration must be given to the operational speed range to determine theposition and pressurization of the minimum pressure point within the enclosure.

  • EN 50016:2002 - 12 -

    8 Supply of protective gas

    8.1 The protective gas shall be non-flammable. The manufacturer shall specify the protective gas andany alternative permitted.

    NOTE 1 The protective gas should not, by reason of its chemical characteristics or the impurities that it may contain, reduce theeffectiveness of the type of protection pressurization p, or adversely affect the satisfactory operation and integrity of the enclosed apparatus.

    NOTE 2 When an inert gas is used and a risk of asphyxiation exists, a suitable warning label should be fixed to the enclosure.

    Normally the temperature of the protective gas to be taken into consideration is 40C at the inlet to thepressurized enclosure. In special circumstances a higher temperature may be permitted or a lowertemperature may be required, for example for cooling purposes, in which case the maximum inlettemperature of the protective gas shall be marked on the pressurized enclosure and stated in themanufacturers documentation.

    8.2 The manufacturer shall specify the density limits of the range of flammable gases for which thepressurized enclosure is designed except where the pressurized enclosure is designed for all flammablegases or for a specific flammable gas.

    ADDITIONAL REQUIREMENTS FOR PRESSURIZED ENCLOSURES WITH CONTAINMENT SYSTEMS

    9 Introduction

    This section specifies the additional requirements for pressurized enclosures with a containment system.

    The choice of protective gas for pressurized enclosures depends upon the probability, quantity andconstituents of the release from the containment system. The release conditions, containment systemdesign requirements, category of internal release and the appropriate pressurization techniques are given inclauses 10 to 14.

    NOTE Consideration should be given by the user to the possible formation of flammable mixture due to the possibility of air penetration intothe containment system and the resulting additional precautions that may be necessary.

    10 Release conditions

    10.1 No release

    10.1.1 There is no internal release when the containment system is infallible. See 11.1.

    10.1.2 No internal release is deemed to exist when the flammable substances inside the containmentsystem are in the gas or vapour phase when operating between the specified temperature limits and either:

    the gas mixture within the containment system is always below the LEL. The conditions to be met in thissubclause require the apparatus to be marked X, or

    the minimum pressure specified for the pressurized enclosure is at least 50 Pa higher than themaximum pressure specified for the containment system and an automatic safety device is provided tooperate if the pressure difference falls below 50 Pa.

    NOTE The purpose(s) for which the automatic safety device is used (i.e. to disconnect power or to sound an alarm or otherwisemaintain the safety of the installation) is the responsibility of the user.

  • - 13 - EN 50016:2002

    10.2 Limited release

    The rate of release of the flammable substance into the pressurized enclosure shall be predictable in allconditions of containment system failure. See 11.2.

    10.3 Unlimited release

    The rate of release of the flammable substance into the pressurized enclosure is not predictable. Thiscondition refers to liquids which can evolve flammable gas or vapour. See 11.3. If there may be, togetherwith the liquid, entrained oxygen, the maximum flowrate of oxygen shall be predictable.

    11 Design requirements for the containment system

    The design and construction of the containment system, which will determine whether leakage is likely tooccur or not, shall be based on the most onerous conditions of service specified by the manufacturer.

    The manufacturer shall specify the maximum inlet pressure to the containment system.

    Details of the design and construction of the containment system, the types and operating conditions offlammable substances it may contain and the expected release rate or rates at given locations, shall beprovided by the manufacturer, in order that the containment system can be classified into one of thecategories of 11.1, 11.2, or 11.3.

    11.1 Infallible containment system

    An infallible containment system shall not have any intentional leakage into the pressurized enclosure. Thiscondition is satisfied when the containment system comprises metallic, ceramic or glass, pipes, tubes orvessels which have no moving joints. Joints shall be made by welding, brazing, glass to metal sealing oreutectic methods 1).

    Low temperature solder alloys such as lead/tin composites are not acceptable.

    NOTE The manufacturer should consider carefully the requirements of clause 6 of EN 50014 in relation to a potentially fragile infalliblecontainment system. Adverse operating conditions to be agreed between manufacturer and user may include vibration, thermal shock anddamage to the infallible containment system during maintenance operations when doors or access covers of the pressurized enclosure maybe open. Good engineering practice in safety matters must be observed.

    11.2 Containment system with limited release

    The design of a containment system with limited release shall be such that the rate of release of theflammable substance is predictable in all conditions of containment system failure. The quantity offlammable substance released into the pressurized enclosure includes the quantity of flammable substancein the containment system and the flow of the flammable substance entering the containment system fromthe process. The flow shall be limited to a predictable rate by appropriate flow limiting devices, fitted outsidethe pressurized enclosure.

    However, if that part of the containment system from the entry point into the pressurized enclosure up toand including the inlet to the flow limiting device conforms to 11.1, the flow limiting device may be installedinside the pressurized enclosure, in which case the flow limiting device shall be permanently secured andhave no movable parts.

    If the flow limiting device is not included as part of the apparatus, the pressurized enclosure shall be markedX.

    1) A method of joining two or more components, normally metallic, employing a binary or ternary alloy system which

    solidif ies at a constant temperature which is lower than the beginning of solidif ication of any of the components beingjoined.

  • EN 50016:2002 - 14 -

    The process flow into the containment system need not be limited if the maximum release rate from thecontainment system into the pressurized enclosure can be predicted. This condition can be met when thematerial within the containment system is entirely in the gaseous phase; and

    the containment system comprises connected parts which individually meet the requirements of 11.1and the joints between the parts are so constructed that the maximum release rate can be predicted andthe joints are permanently secured; and/or

    the containment system includes nozzles or orifices for the purpose of release in normal operation(e.g. flames) but otherwise meets the requirements of 11.1.

    Pressurized enclosures containing a flame shall be assessed as though the flame had been extinguished.The maximum quantity of the fuel/air mixture which supplies the flame shall be added to the quantity ofrelease from the containment system.

    NOTE 1 Elastomeric seals, windows and other non-metallic parts of the containment system are permissible. Pipe threads and flangedjoints are also permissible.

    NOTE 2 It is the responsibility of the user to ensure that the maximum pressure and flow of the flammable substance into the containmentsystem do not exceed the ratings specified by the manufacturer.

    11.3 Containment system with unlimited release

    Containment systems conforming to 11.2 containing liquids from which can evolve flammable gases orvapours shall be designated as containment systems with unlimited release.

    NOTE Other conditions of unlimited release are outside the scope of this standard, see 1.6. Consideration shall be given to the possibleaccumulation of liquid inside the pressurized enclosures and the consequences thereof.

    12 Protective gas and pressurizing technique

    The design of the pressurized enclosure with a containment system and a limited or unlimited release shallbe such that no explosive gas atmosphere can be formed inside the pressurized enclosure, except in adilution area.

    Where inert gas is used as the protective gas, a label with the following wording shall be fixed to theenclosure:

    WARNING: THIS ENCLOSURE NORMALLY CONTAINS INERT GAS AND MAY RELEASEFLAMMABLE SUBSTANCE

    The applicable pressurizing techniques depend upon the category and on the constituents of the release asfollows.

    12.1 Pressurization with leakage compensation

    12.1.1 No release

    The protective gas may be air or inert gas.

    12.1.2 Limited release

    The protective gas shall be inert gas.

    The concentration of oxygen in the containment system shall not exceed 2 % (v/v).

    Leakage compensation with inert gas cannot be used when there is a deliberate release of flammablematerial from the containment, as part of its normal function, into the pressurized enclosure.

  • - 15 - EN 50016:2002

    When the flammable substance released from the containment system has a UEL greater than 80 % (v/v),leakage compensation is not permitted. Only dilution in accordance with 12.2.2a) is suitable.

    NOTE It is difficult or impossible to protect with leakage compensation using inert gas for apparatus which contains a release of gases orvapours which are capable of reacting exothermically even with little or no oxygen present, e.g. an UEL greater than 80 %.

    12.1.3 Unlimited release

    The protective gas shall be inert gas.

    Where oxygen is entrained with flammable substance in the containment system, the concentration ofoxygen in the gas phase of the containment system shall not exceed 2 % (v/v).

    Leakage compensation with inert gas cannot be used when there is a deliberate release of flammablematerial from the containment into the pressurized enclosure as part of its normal function.

    NOTE It is difficult or impossible to protect with leakage compensation using inert gas for apparatus which contains a release of gases orvapours which are capable of reacting exothermically even with little or no oxygen present, e.g. an UEL greater than 80 %.

    12.2 Pressurization with continuous flow of the protective gas

    Where the technique of continuous flow of the protective gas is applied, the flow rate must be sufficient tomaintain the minimum internal overpressure of the pressurized enclosure and to achieve the dilution whereappropriate.

    12.2.1 No release

    The protective gas may be air or inert gas.

    12.2.2 Limited release

    The flow rate of protective gas after purging shall be sufficient, under all conditions of containment systemfailure, to dilute the maximum release into the pressurized enclosure as follows:

    a) when the protective gas is air, the flammable substance in the release shall be diluted to aconcentration not exceeding 25 % of the LEL;

    b) when the protective gas is inert any oxygen in the release shall be diluted to a concentration notexceeding 2 % (v/v);

    at the outlet aperture and at any place within the pressurized enclosure except in the dilution area.

    Where the protective gas is inert, and there is not more than 2 % (v/v) oxygen in the containment system,the flow rate after purging may be reduced to that necessary to maintain the minimum overpressurespecified by the manufacturer.

    When the flammable substance released from the containment system has a UEL greater 80 %, air shall beused to dilute any release of flammable substance to a concentration not exceeding 25 % of the LEL. Onlydilution in accordance with 12.2.2a) is suitable.

    NOTE It is difficult or impossible to protect with continuous flow using inert gas for apparatus which contains a release of gases or vapourswhich are capable of reacting exothermically even with little or no oxygen present, e.g. an UEL greater than 80 %.

  • EN 50016:2002 - 16 -

    12.2.3 Unlimited release

    The protective gas shall be inert gas. The flow rate of protective gas after purging shall be sufficient, underall conditions of containment failures, to dilute the maximum release of entrained oxygen to a concentrationnot exceeding 2 % (v/v) at the outlet aperture and at any place within the pressurized enclosure except inthe dilution area.

    Where there is not more than 2 % (v/v) oxygen in the gas phase within the containment system, the flowrate after purging may be reduced to that necessary to maintain the minimum overpressure specified by themanufacturer.

    Dilution with inert gas cannot be used when there is a deliberate release of flammable material from thecontainment system into the pressurized enclosure as part of its normal function.

    13 Ignition capable apparatus

    Ignition capable apparatus shall not be located in the dilution area. Electrical apparatus in the dilution areashall be protected by a type of protection listed in clause 2 of this standard. Exceptions from thisrequirement are flames, ignitors or other similar apparatus intended to ignite a flame. The dilution areaemanating from the flame shall not overlap any other dilution area.

    NOTE 1 Generally any source of release should be near to the outlet and any ignition capable apparatus near to the inlet of the protectivegas, to allow the shortest possible way for released flammable materials to leave the pressurized enclosure, without passing ignition capableapparatus.

    NOTE 2 To avoid ignition from an ignition source within the containment system back into the plant the use of a flame arrestor can benecessary. Such measures are not covered by this standard.

    14 Internal hot surfaces

    If the pressurized enclosure contains any surface having a temperature which exceeds the ignitiontemperature of the flammable substance released from the containment system, the sample flow into thecontainment system shall be cut off automatically following the operation of the safety devices specified in6.8 and 10.1.2.

    Additionally:

    a) if the protective gas is air, the release of the remaining flammable substance in the containment systemshall not form a concentration greater than 50 % of the LEL in the vicinity of the hot surface(s); or

    b) if the protective gas is inert, the design and construction of the joints of the pressurized enclosure shallbe such as to prevent significant mixing of external air with the internal inert gas (or internal flammablegas) during the cooling period. The ingress of external air shall not increase the concentration of oxygento a value greater than 2 % (v/v).

    A warning label shall also be fitted to the pressurized enclosure stating the delay to be observed betweenthe removal of the source of heat within the pressurized enclosure and the opening of any doors or covers.This delay shall be the longer of the time taken for the hot surface to cool below the ignition temperature ofthe flammable substance released from the containment system or the temperature class of the pressurizedenclosure.

  • - 17 - EN 50016:2002

    VERIFICATION AND TESTS

    15 Type verification and tests

    The apparatus shall be subjected to the following tests applicable and in the following sequence.

    all relevant tests of EN 50014;

    overpressure test;

    leakage test;

    purging test, or filling procedure test for static pressurization;

    dilution test;

    verification of minimum overpressure;

    test for infallible containment system;

    overpressure test for containment systems with limited release.

    15.1 Overpressure test

    A pressure equal to 1,5 times the maximum overpressure specified for normal service with a minimum of200 Pa shall be applied to the pressurized enclosure and, where they are an integral part of the enclosure,the associated ducts and their connecting parts.

    The test pressure shall be applied for a period of 2 min 10 s.

    The test is considered to be satisfactory if no permanent deformation occurs which would invalidate the typeof protection.

    15.2 Leakage test

    15.2.1 The pressure in the pressurized enclosure shall be adjusted to the maximum overpressure specifiedby the manufacturer for normal service. With the outlet aperture closed, the leakage flow rate shall bemeasured at the inlet aperture.

    The measured flow rate shall be not greater than the maximum leakage flow rate specified by themanufacturer.

    15.2.2 In the case of static pressurization the pressure in the pressurized enclosure shall be adjusted to themaximum overpressure that can occur in normal service. With the aperture(s) closed, the internal pressureshall be monitored for a period of time, in accordance with 7.7. The change of pressure shall be not greaterthan the minimum overpressure specified for normal service.

    15.3 Purging test for pressurized enclosures with no internal source of release (pressurizationtechnique may be leakage compensation or continuous flow) and filling procedure test for staticpressurization

    15.3.1 Pressurized enclosure where the protective gas is air

    The pressurized enclosure shall be prepared for test as described in annex D.

    The pressurized enclosure shall be filled with the test gas to a concentration of not less than 70 % at anypoint.

    As soon as the pressurized enclosure is filled the test gas supply shall be turned off and the protective gassupply turned on at the minimum purging rate specified by the manufacturer. The time taken until there isno sample point where there is a test gas concentration in excess of that specified in D.2 shall be measured

  • EN 50016:2002 - 18 -

    and noted as the purging time. If a second test is required, the pressurized enclosure shall be filled with asecond test gas, representing the other end of the density range, to a concentration of not less than 70 % atany point and the purging time for the second test shall be gas measured.

    The minimum purging duration specified by the manufacturer shall be not less than the measured purgingtime or the longer of the two measured purging times where two tests are carried out.

    15.3.2 Pressurized enclosure where the protective gas is inert gas

    The pressurized enclosure shall be prepared for test as described in annex D. The enclosure shall be filledinitially with air at normal atmospheric pressure. The enclosure shall then be purged with the inert gasspecified by the manufacturer.

    The time taken until there is no sample point where there is an oxygen concentration exceeding thatspecified in D.3, shall be measured and noted as the purging time.

    The minimum purging duration specified by the manufacturer shall be not less than the measured purgingtime.

    15.3.3 Pressurized enclosure where the protective gas may be either air or an inert gas with adensity equal to air 10 %

    Where air and inert gas are permitted as alternative protective gases with the same purging time, thepurging time shall be measured by the method specified in 15.3.1.

    15.3.4 Filling procedure test for pressurized enclosures protected by static pressurization

    In the case of static pressurization the enclosure shall be filled with air. The apparatus shall then be filledwith inert gas in accordance with the manufacturers specifications. It shall then be verified that there is nosample point where there is an oxygen concentration exceeding 1 % (v/v), referred to atmosphericconditions.

    15.4 Purging and dilution tests for pressurized enclosures with an internal source of release

    The choice of test gas or gases shall take account of both the external gases and the internally releasedflammable materials.

    15.4.1 Pressurized enclosures with limited or unlimited release, pressurization by leakagecompensation or continuous flow, containment system with less than 2 % (v/v) oxygen and theprotective gas is inert gas

    15.4.1.1 Purging test

    The test shall be carried out using the test procedure specified in 15.3.2. The minimum purge flow rate shallnot be less than the maximum release rate from the containment system. To make allowance for oxygenthat could be released from the containment system during purging, the purging time confirmed in the testshall be increased by 50 %.

    The minimum purging time specified by the manufacturer shall be not less than 1,5 times the measuredpurging time.

    15.4.1.2 Dilution test

    A dilution test is not required because the containment system does not contain more than 2 % (v/v)oxygen.

  • - 19 - EN 50016:2002

    15.4.2 Pressurized enclosures with limited or unlimited release, pressurization by continuous flow,containment system with less than 21 % (v/v) oxygen and the protective gas is inert gas

    15.4.2.1 Purging test

    The enclosure shall be filled with air. Air shall also be injected into the enclosure through the containmentsystem at a flow rate corresponding to the maximum release rate in a manner representing the mostonerous conditions of release, taking into account the position, number and nature of the releases and theirproximity to ignition capable apparatus.

    The supply of the protective gas shall then be turned on at the minimum purging flow rate specified by themanufacturer.

    The time taken until there is no sample point where there is an oxygen concentration exceeding thatspecified in D.3 shall be measured and noted as the purging time. The minimum purging time specified bythe manufacturer shall be not less than the measured purging time.

    15.4.2.2 Dilution test

    Immediately after the purging test specified in 15.4.2.1 the supply of the protective gas shall be adjusted tothe minimum flow rate specified by the manufacturer, the oxygen flow rate from the containment systembeing maintained at that specified in 15.4.2.1.

    The oxygen concentration measured over a period of time not less than 30 min shall not exceed theconcentration as specified in D.3.

    A quantity of air containing an equivalent quantity of oxygen to that within the containment system shall thenbe released into the pressurized enclosure from the containment system together with a release of air inaccordance with 11.2.

    During the period of release the concentration of oxygen in the vicinity of ignition capable apparatus shallnot exceed 1,5 times the oxygen concentration specified in D.3 and shall, in a time not greater than 30 min,be reduced below the specified concentration.

    15.4.3 Pressurized enclosures with limited release, pressurization by continuous flow and theprotective gas is air

    15.4.3.1 Purging test

    The test shall be carried out using the test procedure specified in 15.3.1.

    In addition during the test, the test gas shall be injected into the pressurized enclosure through thecontainment system at the maximum release rate in a manner representing the most onerous conditions ofrelease taking into account the position, number and nature of the releases and their proximity to ignitioncapable apparatus.

    The time taken until there is no sample point where there is a test gas concentration exceeding thatspecified in D.2 shall be measured.

    If a second test is required the test shall be repeated using the second test gas and the purging timemeasured and noted as the purging time.

    The minimum purging time specified by the manufacturer shall be not less than the measured purging timeor the longer of the two measured purging times where two tests are carried out.

  • EN 50016:2002 - 20 -

    15.4.3.2 Dilution test

    Immediately after the purging test specified 15.4.3.1 the supply of protective gas shall be adjusted, ifnecessary, to the minimum dilution flow rate specified by the manufacturer, the test gas flow rate from thecontainment system being maintained at that specified in 15.4.3.1.

    The test gas concentration measured during a time period of not less than 30 min shall not exceed thatspecified in D.2.

    A quantity of test gas equivalent to the volume of flammable gas within the containment system shall thenbe released into the pressurized enclosure from the containment system together with a flow of test gasequivalent to the maximum release of flammable gas in accordance with 11.2.

    During the period of release the concentration of a test gas in the vicinity of ignition capable apparatus shallnot exceed twice the value specified in D.2 and shall within 30 min be reduced below the specified value.

    If a second test is required the test shall be repeated using the second test gas.

    15.5 Verification of minimum overpressure

    A test shall be made to verify that the pressurization system is capable of operating and maintaining anoverpressure complying with 6.9 under normal service conditions.

    The pressure in the enclosure shall be measured at points where leakage is likely to occur, and especiallywhere the lowest pressure will occur. Protective gas shall be supplied to the pressurized enclosure at thelowest pressure, and if necessary at the minimum flow rate, specified by the manufacturer. For rotatingelectrical machines the tests shall be carried out with the machine stopped and running at its maximumrated speed.

    15.6 Tests for infallible containment systems

    These tests are carried out on containment systems designed to be infallible.

    15.6.1 Overpressure test

    A test pressure of at least five times the maximum internal overpressure specified for normal service with aminimum of 1 000 Pa shall be applied to the containment system for a period of 2 min 10 s. Thecontainment system shall be tested under the most onerous conditions of rated temperature.

    The increase of the test pressure should achieve the maximum pressure within 5 s.

    The test is considered to be satisfactory if no permanent deformation occurs and the test specified in 15.6.2is passed.

    15.6.2 Infallibility test

    a) The containment system shall be surrounded by helium at a pressure equal to the maximum pressurespecified for normal service. The containment system shall be evacuated down to a pressure of 0,1 Paor better.

    b) Alternatively the containment system shall be located in a vacuum chamber and be connected to ahelium supply at the maximum pressure specified for normal service. The vacuum chamber shall beevacuated down to a pressure of 0,1 Pa or better.

    The test is considered satisfactory if a pressure of 0,1 Pa can be maintained.

    NOTE A schematic diagram of an infallibility test as described in 15.6.2a) is given in annex B.

  • - 21 - EN 50016:2002

    15.7 Overpressure test for containment systems with limited release

    This test is carried out on containment systems which have a limited release during normal operation.

    A test pressure of at least 1,5 times the maximum internal overpressure specified for normal service, with aminimum of 200 Pa shall be applied to the containment system and maintained for a time of 2 min 10 s.The test is considered to be satisfactory if no permanent deformation occurs.

    16 Routine tests

    The following tests shall be carried out after the completion of the relevant tests of EN 50014.

    16.1 Overpressure test

    A routine test shall be carried out as specified in 15.1.

    16.2 Leakage test

    A routine test shall be carried out as specified in 15.2.

    16.3 Tests for infallible containment systems

    Infallible containment systems tests shall be carried out as specified in 15.6.

    16.4 Test for containment systems with limited release

    Containment systems with limited release shall be tested as specified in 15.7.

    MARKING

    17 Marking

    Pressurized enclosures shall be marked in accordance with the requirements of EN 50014. The followingsupplementary information shall also be marked as appropriate.

    17.1 Pressurized enclosures other than those protected by static pressurization shall be markedadditionally with:

    a) the internal free volume, including ducts where they are an integral part of the enclosure;

    b) type of protective gas (where this is not air);

    c) minimum quantity of protective gas required to purge the enclosure specified by:

    minimum purging flow rate of protective gas;

    minimum purging duration;

    minimum additional purging duration per unit volume of additional ducting (where appropriate);

    NOTE It is the responsibility of the user to increase the quantity of protective gas to ensure purging of the ducts.

    d) the minimum and maximum overpressure;

    e) the maximum leakage rate from the pressurized enclosure;

  • EN 50016:2002 - 22 -

    f) a special temperature or range of temperatures for the protective gas at the inlet to the pressurizedenclosure when specified by the manufacturer;

    g) the point or points at which the pressure is to be monitored unless this is indicated in the relevantdocumentation.

    17.2 Pressurized enclosures with a containment system shall also be marked with the following whereappropriate:

    a) the category of internal release;

    b) the minimum flow rate of protective gas, if necessary;

    c) the maximum inlet pressure to the containment system;

    d) the maximum flow rate into the containment system;

    e) the maximum oxygen concentration in the containment system;

    f) the maximum permitted UEL in the containment system.

    17.3 For pressurized enclosures protected by static pressurization, a warning label (or labels) shall be fittedwith the following wording:

    a) THIS ENCLOSURE IS PROTECTED BY STATIC PRESSURIZATION.

    b) THIS ENCLOSURE SHALL BE FILLED ONLY IN A NON-HAZARDOUS AREA ACCORDING TO THEMANUFACTURERS INSTRUCTIONS.

    17.4 Certified safety related control systems and associated safety devices shall be marked [EEx p].

    17.5 Any other marking required.

  • - 23 - EN 50016:2002

    Annex A(informative)

    Ducting of protective gas

    A.1 Except for cylinder supplied gases and some Group I applications the points at which the protectivegas enters the supply duct(s) should be situated in a non-hazardous area.

    For Group I applications where the protective gas enters the supply ducts from a hazardous area thefollowing precautions should be taken:

    a) Two independent firedamp detectors should be fitted at the discharge side of the fan or compressor,each arranged to disconnect automatically the electricity supply to the pressurized enclosure if theconcentration of firedamp exceeds 10 % of the lower explosive limit.

    b) The time taken to achieve automatic disconnection should not be greater than one half the transit timefor the protective gas to flow from the detection point to the pressurized enclosure.

    c) In the event of automatic disconnection the pressurized enclosure should be repurged before theelectricity supply is restored. The purging time should not start until the firedamp concentration at thesource of protective gas falls below 10 % of the lower explosive limit.

    Any compressor or fan and the associated ducting should be designed and installed in such a way that thesurrounding atmosphere cannot enter the enclosure and duct(s).

    A.2 Ducts for exhausting the protective gas should preferably have their outlets in an area which would,apart from the area in close proximity to the outlets, be a non-hazardous area. Consideration shouldotherwise be given to the fitting of spark and particle barriers (that is devices to guard against the ejection ofignition capable sparks or particles) as shown in columns 3 and 4 in Table A.1.

    Table A.1 Use of spark and particle barriers

    Apparatus group Zone of purgeexhaust

    Enclosed apparatusA a

    Enclosed apparatusB b

    I Non-hazardous Not required Not requiredHazardous Required c Required c

    II Non-hazardous Not required Not requiredZone 2 Required Not requiredZone 1 Required c Required c

    a Apparatus which may produce ignition capable sparks or particles in normal service.b Apparatus which does not produce ignition capable sparks or particles in normal service.c If the temperature of the enclosed apparatus constitutes a hazard upon failure of pressurization, a suitabledevice should prevent the rapid entry of the surrounding atmosphere into the pressurized enclosure. See 5.2.

  • EN 50016:2002 - 24 -

    Figures: Examples of the changes in pressure in ducts and enclosures

    1

    9

    7

    2 3 2 4 52

    P1Pa mbar

    50 0,5 0 0

    Case a Protective gas outlet without a spark and particle barrier

    1

    9

    7

    2 3 2 4 52 8

    P1Pa mbar

    50 0,5 0 0

    Case b Protective gas outlet with a spark and particle barrier

    Figure A.1 Pressurized enclosures with continuous flow of protective gas

  • - 25 - EN 50016:2002

    1

    9

    7

    2 3 2 4 2 6

    P2Pa mbar

    50 0,5 0 0

    Figure A.2 Pressurized enclosures with leakage compensation,enclosures without moving parts

    9

    7

    4

    1

    2 3

    2

    P3Pa mbar

    50 0,5 0 0

    6

    B

    C

    B

    A

    A C

    NOTE Pressure at every point where leakage can occur is above the minimum of 50 Pa.

    Figure A.3 Pressurized enclosures with leakage compensation,rotating electrical machine with an internal cooling fan

  • EN 50016:2002 - 26 -

    910

    11

    1

    2 3 2 4

    Pa

    P5

    P4mbar

    0,5

    mba

    r5

    0 P

    a

    0 0

    7

    62

    Figure A.4 Pressurized enclosures with leakage compensation,rotating electrical machine with an external cooling fan

  • - 27 - EN 50016:2002

    Key to Figures A.1 to A.4

    NOTE In the figures examples are shown where the overpressure is maintained by a fan. This can however, also be provided by othermeans, e.g. by feeding air from compressed air cylinders, compressors, etc. In such cases there would be different pressure drops up theenclosure entry.

    P1 : Pressure of the protective gas (determined by the flow resistance through the ducting, the parts withinthe enclosure and in certain cases through a choke or spark and particle barrier).

    P2 : Pressure of the protective gas (almost constant).

    P3 : Pressure of the protective gas (determined by the flow resistance of the internal parts, and influencedbetween A, B and C by the internal cooling fan).

    P4 : Pressure of protective gas (determined by the flow resistance of the internal parts and by theuppermost value of pressure of the external air).

    P5 : Pressure of the external air, caused by the external cooling fan.

    1 : Protective gas inlet (in a non-hazardous area).

    2 : Ducting

    3 : Fan

    4 : Enclosure

    5 : Choke (where required to maintain the overpressure)

    6 : Outlet valve

    7 : Protective gas outlet

    8 : Spark and particle barrier

    9 : Overpressure

    10: Internal pressure

    11: External pressure

  • EN 50016:2002 - 28 -

    Annex B(informative)

    Infallibility test for a containment system

    PPressuremonitoringdevice

    V

    V1

    2

    Critical orificediameter

    Evacuatingsystem

    System under test

    IVIV1 2

    Connectingorifice diameter

    DDx

    Helium filledchamber

    Figure B.1 Schematic diagram of infallibility test described in 15.6.2a)

    1) The volume V2 > the volume V1 of the system under test.

    2) The cross-sectional area of the critical orifice diameter D < the cross-sectional area of theconnecting orifice Dx.

    3) The pressure monitoring device P shall be corrected to take account of the properties of the leaktesting gas (e.g. helium).

    4) The test is satisfactory if a pressure of 0,1 Pa can be maintained in V2 with both valves open (IV1and IV2).

    5) The leak rate (if any) can be determined with IV1 open and IV2 closed.

  • - 29 - EN 50016:2002

    Annex C(informative)

    Function test of the surveillance circuits

    The following is an example of information to be provided by the manufacturer for a simple control systemfor a pressurized enclosure with leakage compensation.

    S0

    S1

    S3

    S2

    S0

    1111111111110000

    S1

    0000000000001000

    S2

    0000000000000100

    S3

    0000000000000011

    MOP

    0011100100001111

    XOP

    1011110110010000

    PFLO

    0010111000110101

    PTIM

    1101111000000011

    LEAKAGE COMPENSATION LOGICAL DEFINITIONS

    Excess over pressureOver pressure > 50 Pascals

    Purge flow > minimumPurge time incomplete

    Purge time complete

    Initial state[MOP]&NOT[XOP]&NOT[PFLO]&NOT[PTIM]

    [MOP]&NOT[XOP]&[PFLO]&NOT[PTIM][MOP]&NOT[XOP]&[PTIM]

    =====

    ====

    [XOP][MOP][PFLO]NOT[PTIM][PTIM]

    S0S1S2S3

    Minimum conditions to start purgePurgingPurging complete, power connected

    State diagram and truth table of a leakage compensation purge control

    Each STATE of the system is defined in response to the inputs of the monitoring devices. The states areunique. Transitions between states are only allowed along paths defined by the arrows and in the directionof the arrows. The logical conditions for the occupation of each state are uniquely defined by BOOLEANlogical expressions. All possible combinations of input conditions are shown in the table. Other systems withmore monitoring devices can be described by this method provided each operational state uniquely definedby its inputs.

  • EN 50016:2002 - 30 -

    Annex D(normative)

    Purging and dilution tests

    D.1 General

    The internal atmosphere of the pressurized enclosure shall be tested at different points where it isconsidered that the test gas is most likely to persist during the tests except in the dilution areas where notest shall be made.

    The gas concentration at the test points shall be analysed or measured throughout the period of the test(s).If the test consists of taking samples, the quantities taken should not significantly influence the test.

    For example, the pressurized enclosure may be fitted with a number of small bore tubes, the open ends ofwhich shall be located inside the pressurized enclosure at sampling points where it is considered that thetest gas is most likely to persist during the tests. Where the enclosure contains an internal source of release,some of the test points shall be located in the vicinity of ignition capable apparatus.

    If necessary apertures in the pressurized enclosure may be closed to enable the pressurized enclosure to befilled with the specified test gas provided that they are reopened for the purging and dilution tests.

    Where air is used as the protective gas the test method shall be as follows:

    When required for specific applications tests may be carried out for a specific range of flammable gasesand vapours. In this case the potentially hazardous gases shall be specified and test gases chosenhaving densities similar to the upper and lower boundaries of the stated hazardous gases so that thetests cover all gases in the stated density range.

    In the case of a single specified gas, a single test shall be carried out with a test gas having a densitysimilar to that of the specified gas.

    When it is required to cover all flammable gases two tests shall be carried out, one to cover lighter thanair gases, where the test gas shall be helium, the other test to cover heavier than air gases, where thetest gas shall be either argon or carbon dioxide.

    NOTE Generally test gases should be non-flammable and non-toxic.

    D.2 Criteria for compliance where the protective gas is air

    The concentration of test gas at the sample points after purging, and where applicable dilution, shall notexceed:

    a value equivalent to 25 % of the more onerous LEL where 2 tests are carried out to cover a specificrange of flammable gases;

    a value equivalent to 25 % of the LEL where one specific flammable gas is covered;

    1 % for the helium test and 0,25 % for the argon or carbon dioxide test to cover all flammable gas.

    NOTE These values correspond approximately to 25 % of the LEL for the lighter than air gases and heavier than air gases respectively.

    D.3 Criteria for compliance where the protective gas is inert gas

    Where the protective gas is inert gas, the concentration of oxygen after purging, and where applicabledilution, shall not exceed 2 % (v/v).

  • blank

  • BS EN 50016:2002

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