Explosion Proof / Explosion Protected Electrical Products for ......teristics of explosion...

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pointed. First mining test facilities were set up to test the suitability of explosives. Al- ready in 1894 in the Ruhr region in Dortmund- Derne a larger mining test facility for coal mining was established under the direction of Bergassessor CARL BEYLING. In 1928 an- other Saxon mining test facility whose main focus was on brown coal was put into opera- tion at the Bergakademie Freiberg. With the increasing economic importance of lignite mining and the explosion hazards, that exist- ed therein, for example in the processing of coal in briquetting plants, there was a need to pay attention to machines and equipment for use in potentially explosive atmospheres [2]. History and present Explosion protection in the BAM by Rainer Grätz and Volkmar Schröder Explosion protection in the Chemisch- Technische Reichsanstalt The development of the Federal Institute for Materials Research and Testing (BAM), a federal institute under the auspices of the Federal Ministry of Economics and Technolo- gy (BMWi), is closely connected with the field of explosion protection. As in many oth- er European countries the roots of explosion protection in Germany are found in mining. Mine explosions caused by methane gas and coal dust led to systematic studies of explo- sion risks. At the end of the 19th Century with the use of new explosives the number of fire- damp explosions increased and in Prussia a national commission for firedamp, the Prus- sian-Schlagwetterkommission [1] was ap- Legislation, Standards and Technology Figure 1: Main building of the Federal Institute for Materials Research and Testing (BAM) in Berlin Page 26 | Ex-Magazine 2012

Transcript of Explosion Proof / Explosion Protected Electrical Products for ......teristics of explosion...

  • pointed. First mining test facilities were set up to test the suitability of explosives. Al-ready in 1894 in the Ruhr region in Dortmund-Derne a larger mining test facility for coal mining was established under the direction of Bergassessor CARL BEYLING. In 1928 an-other Saxon mining test facility whose main focus was on brown coal was put into opera-tion at the Bergakademie Freiberg. With the increasing economic importance of lignite mining and the explosion hazards, that exist-ed therein, for example in the processing of coal in briquetting plants, there was a need to pay attention to machines and equipment for use in potentially explosive atmospheres [2].

    History and presentExplosion protection in the BAMby Rainer Grätz and Volkmar Schröder

    Explosion protection in the Chemisch-Technische Reichsanstalt

    The development of the Federal Institute for Materials Research and Testing (BAM), a federal institute under the auspices of the Federal Ministry of Economics and Technolo-gy (BMWi), is closely connected with the field of explosion protection. As in many oth-er European countries the roots of explosion protection in Germany are found in mining. Mine explosions caused by methane gas and coal dust led to systematic studies of explo-sion risks. At the end of the 19th Century with the use of new explosives the number of fire-damp explosions increased and in Prussia a national commission for firedamp, the Prus-sian-Schlagwetterkommission [1] was ap-

    Legislation, Standards and Technology

    Figure 1: Main building of the Federal Institute for Materials Research and Testing (BAM) in Berlin

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  • Parallel to the activities in mining, at the beginning of the 20th Century in Germany there were efforts to ensure safety in the rapidly developing young chemical industry. Since 1880 activities to establish a national authority (Reichsbehörde) for chemistry, sim-ilar to the Physikalisch-Technische Reichsan-stalt (PTR) for physics, were taking place. This national institute was designed to pro-mote science in chemistry, as well as to set rules and standards for the chemical safety engineering. Whereas EMIL FISCHER, WALTHER NERNST and WILHELM OSTWALD demanded a national chemical research in-stitute, the Chemische Reichsanstalt, to en-courage ›scientific tasks which can only meet with high effort‹, CARL ALEXANDER VON MARTIUS, founder of the ›Aktien-Ge-sellschaft für Anilin-Fabrikation‹ (AGFA), rec-ommended in 1908 the establishment of a technical national authority: ›As science and technology became more important in social life, the need to create standards which de-veloped business activities in full, increased. On the other hand, the legitimate interests of the public and the individual against damage needed to be preserved‹ [3]. VON MARTIUS knew, and that was groundbreaking for its time, that the acceptance of new techniques by the people critically depends on the safe operation of the facilities. So in 1911 the Kaiser-Wilhelm-Institute für Chemie was built in Berlin-Dahlem for the promotion of research. In 1920, with the con-version of a military test department (Mil-itärversuchsamt), the founding of the Chemisch-Technische Reichsanstalt (CTR) in Berlin-Plötzensee followed. The CTR was a subsidiary institute of the national interior ministry, the Reichsinnenministerium, and carried out amongst other things technical studies on loss prevention in chemistry.

    The former tasks of the ›Chemisch-Techni- sche Reichsanstalt‹ were reflected in the working plan of 1921 [3]. It states in Part 1, ›Investigations in the field of loss prevention and occupational safety‹ amongst others:> Basic experimental chemical investigations,> Tests in preparation of legal regulations for production, storage, transport and use of fire hazardous and explosion hazardous substances,> Review the handling and transport safe- ty and chemical stability of mining ex- plosives, propellants, igniting devices and other inflammable materials, also cylinders with compressed gases,> Investigation of celluloid in regard to the fire and explosion hazard,> Monitoring of potentially hazardous plants,> Analysis of accidents caused by fires and explosions.

    In 1921, shortly after its inception, the CTR was entrusted with the investigation of one of the biggest explosion accidents in the ex-isting industrial history. On September, 21, 1921 a huge explosion devastated the new plant of the Badische Anilin- & Soda-Fabrik (BASF) in Oppau-Ludwigshafen. It claimed more than 500 lives; the site and surround-ings were badly damaged. The accident oc-cured during blasts being carried out to loos-en ammonium nitrate sulfate fertilizer stored in a warehouse.HERMANN KAST, Head of Department S ›Ex-plosives‹ of the CTR, assumed control during the investigation of the accident and pub-lished in 1924 in the ›Chemiker Zeitung‹ the final report. During the period before the Second World War questions about safety engineer-

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    ing and explosion protection were primarily executed in the Section C for general chem-istry. It was especially WALTHER RIMARSKI, head of department and chairman of the Ger-man acetylene association (Deutscher Acet-ylenverein), who integrated the rapidly devel-oping new field of ›Acetylene, industrial gases and welding technology‹ [3]. In 1937 RIMARSKI took over the directorship of the CTR and chaired it as its president until its closing in 1945. For the first time safety characteristics of flammable gases and liquids, which are im-portant for explosion protection, such as ex-plosion limits, flash points, ignition tempera-tures, etc., were systematically analyzed and archived in the form of a file at the CTR. Be-fore the Second World War the CTR was aligned with the war economy, and as a fol-lower of the military test office (Militärver-suchsamt) the CTR was primarily working for the German Wehrmacht during the war. Based on this, in 1945 the CTR had to discon-tinue its activities by the order of the Soviet occupying power. Confirmed by the Magistrat of Berlin, the association of the Materialprü-fungsamt with the Chemisch-Technischen Reichsanstalt (CTR) took place on August, 1, 1945 in the buildings of the Materialprüfung-samt in Berlin-Dahlem.

    Figure 2: Walther Rimar-ski (1874 – 1963), Presi-dent of Chemisch-Tech-nische Reichsanstalt 1937-1945

  • During the war, the file with the safety char-acteristics of flammable gases and vapors, necessary for explosion protection meas-ures, was lost in the CTR. The former employ-ee of CTR, KARL NABERT began to reassem-ble this data in the Physikalisch-Technische Reichsanstalt which was relocated from Ber-lin to Brunswick. By 1950 a preliminary draft of the table was completed and in 1953 the first edition of ›Safety characteristics of flam-mable gases and vapors‹ [4] was published. Using the safety characteristics, the table al-lowed a uniform assessment of explosion hazards and formed the material basis for the explosion protection regulations and stand-ards.

    Explosion protection in the BAM

    Today the BAM is a scientific institute with nearly 1,800 employees and a budget of more than 100 million Euros per year. Work content is determined by the social mission for ensur-ing safety in technology and chemistry. Ex-plosion protection has been a key aspect of Department 2, ›Chemical Safety Engineering‹ at BAM for a long time.This essentially covers the investigation and assessment of> hazardous substances and goods,> hazardous chemical reactions,> processes, plants, parts of plants and safety equipment for the handling of hazardous substances and systems.

    History and present - Explosion protection in the BAM

    Figure 3: The ›Oppau hole‹ (Oppauer Loch). Devastated BASF factory after the explosion of fertilizers in 1921 (Source: www.chemieonline.de/forum)

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    As a part of physical-chemical safety, engi-neering explosion protection can be consid-ered as the sum of the measures in unwant-ed oxidation reactions with a subsequent increase in temperature and pressure. In the classical sense atmospheric conditions with the oxidant ›air‹ are considered, but in the broader sense also conditions in closed sys-tems with non-atmospheric conditions are considered. Therefore explosion protection varies from the material properties of the mixture over dispersion of mixtures, control of ignition sources and limitation of the ef-fects of explosions, requirements for equip-ment, protective systems and plants to the operating requirements for plant safety, and for transport of dangerous goods.

  • Figure 4: Historical roots of BAM [5]

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    Division of work with the Physikalisch-Technische Bundesanstalt

    Because of the historical development the basic principles of explosion protection are now handled with a wide division of tasks between both federal institutes. Work is carried out in close cooperation within the framework of the main focus ›Physical and chemical safety engineering.‹ PTB focuses on electrical explosion protection, electrical and mechanical ignition sources and que-stions concerning the handling of flammable liquids. BAM is involved with flammable gases and dusts. In addition, the physical-chemical safety engineering as a whole, in-cluding explosives and dangerous chemical reactions, is the main task of BAM. This divi-sion of responsibilities is coordinated by a joint steering committee of BAM and PTB and has been working well for many years.

    Safety characteristics

    An important basis for identifying and as-sessing explosion risks as well as for the se-lection and design of explosion protection measures is the knowledge of relevant safety characteristics and their dependencies, es-pecially on pressure and temperature. The determination of safety characteristics is carried out in BAM and PTB, based on the di-vision of the tasks. PTB is focused on the de-termination of characteristics for flammable liquids and vapors, and BAM is focused on the determination of characteristics for flam-mable gases and dusts.

  • In the jointly well-maintained database CHEMSAFE [6] by BAM, PTB and DECHEMA, these parameters will be recorded and they are available for users in a simple way. It is an essential feature of CHEMSAFE that be-fore the substances are recorded in the data-base, an evaluation process takes place that leads to a special reliability of the available data. The database contains evaluated safety characteristics of currently 3600 flammable liquids, gases and dusts and 810 mixtures. These data are on hand not only for atmos-pheric, but also for non-atmospheric condi-tions. In a handbook of BAM and PTB [7, 8], which follows up the work of NABERT, SCHÖN and REDEKER [9], the main charac-teristics of explosion protection are summa-rized. In addition, in Volume 2 ›Explosion Re-gions of Gas Mixtures‹ explosion diagrams of systems of the type of fuel gas/inert gas/oxi-dizer are available, that allow extended statements for the inerting of explosive mix-tures.

    Prevention of explosive atmosphere

    An important measure for monitoring of activities relating to primary explosion pro-tection is the use of gas detectors. The divi-sion 2.1 ›Gases, Gas Plants‹ is an accredited laboratory for testing the measurement func-tion and the functional safety of gas detec-tors for warning of hazardous concentrations of flammable and/or toxic gases and oxygen. The whole test of gas detectors, which in-cludes both the measurement function and their property as electrical equipment, is car-ried out in cooperation with PTB. All neces-sary tests according to safety of electrical ig-nition sources happen here on these devices.

    Prevention of ignition sources on non-elec-trical equipment

    In mechanical devices such as gears, pumps, stirrers or dynamic seals, in the case of technical failures, effective ignition sourc-es may be generated as a result of impact events or continuous metallic friction. The ig-nitability of mechanically generated sparks depends on a lot of influencing factors, such as the kinetic impact energy or grinding ve-locity, the geometry of the impact or grinding partners, the contact pressure of the grinding partners, the kinematics, the materials used, the surface properties, the amount of rust and the composition of the explosive mixture – also within one gas group. For a long time in division 2.1 ›Gases, Gas Plants‹ investiga-tions are carried out with impact and grind-ing spark test apparatuses using different ex-plosive fuel/air-mixtures in close coordination with the PTB. Predominantly scientific investigations about impact sparks are executed at BAM and about rubbing and grinding sparks at PTB. The following param-eters can be varied at the apparatus of BAM:> Material pairings,> Impact energy,> Grinding velocity and contact pressure,> Fuel/air-mixture.

    History and present – Explosion protection in the BAM

    In division 2.1 ›Gases, Gas Plants‹ at BAM the following safety characteristics of flam-mable gases can be determined:> explosion limits,> limiting oxygen concentration (LOC),> minimum ignition temperature,> minimum ignition energy,> maximum experimental safe gap,> maximum explosion pressure and> rate of explosion pressure rise.

    For these studies various apparatuses are available that allow the determination of pa-rameters for both, atmospheric conditions and increased initial conditions (pressures up to 500 bar and temperatures up to 300 ° C). In division 2.2 the safety characteristics are determined for combustible dusts as lay-ered dusts and as dust clouds. These char-acteristics are:> the auto-ignition temperature, > the minimum ignition temperature of a dust layer (smouldering temperature).> the lower explosion limit,> the limiting oxygen concentration,> the minimum ignition energy,> the ignition temperature,> the maximum explosion pressure > the maximum rate of pressure rise or the KSt-Value for dust clouds.

    For the determination of these characteris-tics various sizes of explosion apparatuses (20 liter and 1 m3), a modified Hartmann Ap-paratur, a BAM-oven and a Godbert-Green-wald furnace are available.

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  • The results of these investigations form the basis for the assessment of mechanical igni-tion hazards on equipment, assemblies, plants and parts of plants. Furthermore these results influence the development of different European and international standards (i.e. EN 1127-1 [10], EN 13463-1 [11], EN 14986 [12]). The available test apparatuses can be used to investigate user-specific material pairings for the probability of formation of mechani-cally generated sparks and their ignitability under user-specific conditions.

    Constructional explosion protection

    Relatively small explosions can often lead to major damages by subsequent fires and failure of structures. Such order of events and consequential damages are avoidable if the incipient explosion propagation inside of vessels and other containers can be con-trolled. Technical measures to limit the incipi-ent explosions to a safe level are, for exam-ple:> explosion decoupling measures such as flame arresters,> explosion-proof design,> explosion relief,> explosion suppression.

    BAM deals in this context particularly with questions of propagation of deflagrations and detonations in pipes, the pressure relief of gas explosions and the investigation of dust explosions and dust explosion relief.

    The investigation of the propagation of defla-grations and detonations in pipes takes place with the goal of improving the basis for the design and testing of flame arresters. On the one hand, investigations about the transition of deflagrations to detonations and on the other hand, about the influence of obstacles on the propagation of explosions in pipes are focused on for this work. The relief of gas explosions is an object of investigation BAM has been dedicated for some years. Using relief devices it is possible to prevent bursting of equipment, vessels and piping in the event of an explosion. A key problem for the design of pressure relief is the consideration of turbulence-generating built-in components.

    Another important focus is the study of dust explosions and dust explosion relief. About 80% of industrial dusts are combusti-ble. This percentage explains why dust fires and dust explosions occur in almost each in-dustry as well as on transport, during the handling or the storage of powders. The determination of the safety characteristics of combustible dusts and the subsequent application of measures to prevent dust ex-plosions in industrial plants help to provide safety to men, real values and the environ-ment. To investigate these issues in addition to the BAM facilities on the main campus in Berlin-Lichterfelde, large-scale test facilities at the Test Site Technical Safety (TTS) in Horstwalde (60 km south of Berlin) are also available.

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    Figure 5: Area for deflagration and detonation experiments in pipes

  • History and present – Explosion protection in the BAM

    BAM activities as notified body according to directive 94/9/EC

    Explosion protection requirements for products are regulated by the European Di-rective 94/9/EC [13]. This European Directive covers both electrical and non-electrical equipment. The implementation of this Direc-tive in Germany is stated in the 11th Ordi-nance to the Equipment and Product Safety Act (11. GPSGV, Explosionsschutzverord-nung) [14]. The essential content of this Ordi-nance and the European Directive 94/9/EC are the definitions for equipment, protective systems and components, the system of con-formity assessment and the declaration of conformity, as well as essential health and safety requirements. Since 1997 BAM has been working as a Notified Body with identi-fication number 0589 in the system of con-formity assessment of products covered by Directive 94/9/EC. The BAM is notified for the relevant conformity assessment procedures (EC-type examination, production quality as-surance, product quality assurance) for non-electrical equipment, gas detectors and flame arresters. Furthermore, BAM as Noti-fied Body provides manufacturers of non-electrical equipment of equipment groups I and II, equipment category M2 and 2, the re-ceipt and storage of documents in the con-text of the module for internal control of pro-duction.

    Participation in national and international committees of explosion protection

    As a research institution of the Federal Government, the BAM, as well as the PTB, has the specific task of communication be-tween the interests of economy and society. An essential part of this function is to advise the federal government in safety committees. These include e.g. the Committee for Indus-trial Safety (Ausschuss für Betriebssicherheit (ABS)) and the Committee on Hazardous Sub-stances (Ausschuss für Gefahrstoffe (AGS)), the committee of the Federal Ministry of La-bour and Social Affairs (BMAS), the Commit-tee on Transport of Dangerous Goods (Aus-schuss Gefahrgutbeförderung (AGGB)) and the Dangerous goods traffic advisory board at the Federal Ministry of Transport, Building and Urban Development (Gefahrgut-Verkehrs-Beirat beim Bundesministerium für Verkehr, Bau und Stadtentwicklung (BM-VBS)), the Commission for Plant Safety (Kom-mission für Anlagensicherheit (KAS)) of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) with various sub-committees. Furthermore, repre-sentatives of BAM work in rule-making bod-ies of the Berufsgenossenschaften and ad-vise the market surveillance and commercial inspectorate of the federal states and other authorities, and also manufacturers of explo-sion-proof equipment and users of plants re-quiring supervision. Also as explosion pro-tection increases, as in many other industries, the importance of the internation-al market increases. Due to their large amount of export German machine and plant engineering companies are particularly de-pendent on the global trade in technology products and engineering services. There-fore, European and international standardiza-tion plays an increasingly important role.

    There is a test site for investigation of fire and explosion hazards.

    The experimental equipment includes in detail:> Building for experiments with oxygen,> Technical equipment building,> Test bunker with detonation pipe test facility,> Area for experiments with oxygen under high pressure,> Concrete area for explosion tests,> Test bunker,> Observation tower,> Silo test facility,> Pipe test facility.

    Figure 6: Silo for investigation of dust explosions

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  • The key elements are the harmonized Euro-pean standards, which cause the presump-tion of compliance with respect to European directives. For non-electrical equipment, pro-tective systems and safety parameters these are in particular the standards of CEN/TC 305 ›Potentially explosive atmospheres - Explo-sion prevention and protection‹, with their presumption of conformity in relation to Di-rective 94/9/EC. While the standards of the electrical explosion protection are now being developed almost exclusively at IEC level, this process is just beginning in the IEC/SC 31M ›Non-electrical equipment and protec-tive systems for explosive atmospheres‹, which creates ISO standards in this area. Employees of the department ›Chemical Safety Engineering‹ at BAM are working in collaboration with their colleagues of PTB at all levels of the standardization process in professional and managerial positions. They represent safety and technology principles, as they have been developed in Germany and Europe for years. Hence many SMEs that are not able to participate on their own in inter-national standardization are also supported. Research and development work in PTB and BAM on the properties of explosive atmos-pheres, ignition sources, and on the propaga-tion of explosion and detonation processes support as pre-normative research standard-ization and regulation work or form the basis for technical developments.

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    [1] Archive in Nordrheinwestfalen, http://www.archive.nrw.de[2] A. Pärnt ›IBExU – 80 Jahre Tradition im Explosionsschutz für Industrieanlagen‹, R.STAHL Ex-Zeitschrift 2009, S. 13 – 19[3] Walter Ruske: 100 Jahre Materialprüfung in Berlin, Bundesanstalt für Materialprüfung, Berlin, 1971[4] K. Nabert und G. Schön: Sicherheitstechnische Kennzahlen brennbarer Gase und Dämpfe, Deutscher

    Eichverlag Braunschweig, 1953[5] W. Ruske, G. Becker, H.Czichos: Die Chronik 1871 – 1996, Wirtschaftsverlag NW, Bremerhaven, 1996[6] DECHEMA, BAM und PTB: CHEMSAFE, eine Datenbank mit bewerteten sicherheitstechnischen

    Kenngrößen, Frankfurt/a.M., Update 2011[7] E. Brandes und W. Möller: Safety Characteristic Data,

    Volume 1: Flammable Liquids and Gases, Wirtschaftsverlag NW, Bremerhaven, 2008[8] M. Molnarne, Th. Schendler und V. Schröder: Safety Characteristic Data,

    Volume 2: Explosion Regions of Gas Mixtures, Wirtschaftsverlag NW, Bremerhaven, 2008[9] T. Redeker und G. Schön: 6. Nachtrag zu Sicherheitstechnische Kennzahlen brennbarer Gase und

    Dämpfe, Deutscher Eichverlag Braunschweig, 1990[10] EN 1127-1: Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and

    methodology [11] EN 13463-1: Non-electrical equipment for use in potentially explosive atmospheres - Part 1: Basic

    method and requirements [12] EN 14986: Design of fans working in potentially explosive atmospheres[13] DIRECTIVE 94/9/EC OF THE EUROPEAN PARLIAMENT AND THE COUNCIL of 23 March 1994 on the

    approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres

    [14] Elfte Verordnung zum Geräte- und Produktsicherheitsgesetz (11. GPSGV) vom 12. Dezember 1996 (BGBl. I Nr. 65 vom 19.12.1996 S. 1914) zuletzt geändert am 6. Januar 2004 durch Artikel 18 des Gesetzes zur Neuordnung der Sicherheit von technischen Arbeitsmitteln und Verbraucherprodukten (BGBl. I Nr. 1 vom 09.01.2004 S. 2)

    [15] M. Beyer, H. Bothe und T.Schendler ›Physikalisch-Chemische Sicherheitstechnik und Explosions-schutz in PTB und BAM‹, PTB-Mitteilungen 1/2011

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