EN 746-3:2021
(Main)Industrial thermoprocessing equipment - Part 3: Safety requirements for the generation and use of atmosphere gases
Industrial thermoprocessing equipment - Part 3: Safety requirements for the generation and use of atmosphere gases
This part of the EN 746 series specifies safety requirements for generation and use of protective and reactive atmosphere gases that are part of industrial thermo-processing equipment (TPE).
The general safety requirements common to TPE are provided in EN 746 1:1997+A1:2009 (see Introduction).
This part of the EN 746 series deals with significant hazards, hazardous situations and events relevant to the generation and use of protective and reactive atmosphere gases created by thermochemical reactions and their use in TPE that are part of TPE as listed in Clause 4 and Clause 5, when used as intended and under the conditions foreseen by the manufacturer.
This part of the EN 746 series covers:
- pipework downstream of and including the manual isolating valve,
- equipment for the generation of atmosphere gases,
- additional equipment for the use of atmosphere gases in TPE,
- safety devices, and
- functional requirements for safety related control system
for the generation and use of protective and reactive atmosphere gases.
It applies to the supply of atmosphere gas, source gas, inert gas and process liquids to TPE and their removal from TPE, confined to equipment integrated in the TPE.
This part of the EN 746 series also details the anticipated significant hazards associated with atmosphere gas systems and their use in TPE and specifies the appropriate preventative measures for the reduction or elimination of these hazards.
The pressure hazard of the piping and components covered by this standard is within the maximum pressure/size relationship of group 1 as described in Annex C.
This part of the EN 746 series:
- specifies the requirements to be met to ensure the safety of persons and property during installation, commissioning, start up, operation, shutdown and maintenance,
- does not cover the relevant risks involved in the flue gas ducting system when it is not considered a part of TPE,
- is not applicable to utility supply upstream of the TPE main disconnects,
- does not apply to TPE for semi-conductor devices,
- does not apply to TPE with atmosphere, such as air and flue gas from an over stoichiometric combustion,
- does not cover the decommissioning of the TPE,
- does not cover vacuum furnaces,
- does not cover blast furnaces, converters (in steel plants), boilers and equipment not covered under EN ISO 12100:2010.
- does not deal with the hazard of noise which is covered in EN 746 1:1997+A1:2009,
- is not applicable to generation and use of atmosphere gas in TPE and associated plant which is manufactured before the date of its publication, and
- gives the necessary requirements for the information for use.
A TPE designed according to this part of EN 746 series does not create any potentially explosive atmosphere in the area around the TPE and is not designed to be located in an area with a potentially explosive or hazardous atmosphere.
This part of the EN 746 series deals with significant hazards which are described in Annex A.
A table of typical protective and reactive gases is given in Annex B.
Industrielle Thermoprozessanlagen - Teil 3: Sicherheitsanforderungen für die Erzeugung und Anwendung von Schutz- und Reaktionsgasen
Dieser Teil der Normenreihe EN 746 legt die Sicherheitsanforderungen an die Erzeugung und Nutzung von Prozessgasen, die Teil einer industriellen Thermoprozessanlage (TPE) sind, fest.
Für TPE übliche allgemeine Sicherheitsanforderungen werden in EN 746 1:1997+A1:2009 festgelegt (siehe Einleitung).
Dieser Teil der Normenreihe EN 746 behandelt erhebliche Gefährdungen, Gefährdungssituationen und ereignisse, die mit der Erzeugung und Anwendung von Prozessgasen, die durch thermochemische Reaktionen erzeugt werden, und ihrer Anwendung in TPE zusammenhängen und die nach der Auflistung in Abschnitt 4 und Abschnitt 5 Teil von TPE sind, wenn diese wie beabsichtigt und in den vom Hersteller vorhergesehenen Bedingungen angewendet werden.
Dieser Teil der Normenreihe EN 746 behandelt:
Rohrleitungssysteme in Strömungsrichtung beginnend mit dem handbetätigtem Absperrventil,
Anlagen für die Erzeugung von Prozessgasen,
zusätzliche Anlagen zur Anwendung von Prozessgasen in TPE,
Sicherheitseinrichtungen, und
funktionale Anforderungen an sicherheitsbezogene Steuerungen
zur Erzeugung und Anwendung von Prozessgasen.
Er ist anzuwenden für die Versorgung von TPE mit Prozessgasen, Ausgangsgasen, Inertgasen und Prozessflüssigkeiten und deren Entfernung aus TPE. Er betrifft nur Anlagen, die in TPE integriert sind.
Dieser Teil der Normenreihe EN 746 gibt die zu erwartenden signifikanten Gefährdungen an, die bei Prozessgassystemen und ihrer Verwendung in TPE vorhanden sind, und legt die entsprechenden Vorsorgemaßnahmen zur Verringerung oder Beseitigung dieser Gefährdungen fest.
Die Druckgefährdung der Rohrleitungen und Komponenten, die in dieser Norm abgedeckt sind, liegt innerhalb des maximalen Druck-/Größenverhältnisses der Gruppe 1, wie in Anhang C beschrieben.
Dieses Teil der Normenreihe EN 746:
— legt die Anforderungen fest, die zur Sicherstellung der Sicherheit von Personen und Eigentum während der Installation, der Inbetriebnahme, dem Anfahren, dem Betrieb, der Abschaltung und der Instandhaltung zu erfüllen sind,
— behandelt nicht die relevanten Risiken, die Rauchgasanlage betreffen, wenn diese nicht als Teil der TPE betrachtet werden,
— ist nicht anzuwenden für die Versorgungsinfrastruktur, die den Haupttrenneinrichtungen der TPE vorgelagert ist,
— ist nicht anzuwenden für TPE für die Halbleiterfertigung,
— ist nicht anzuwenden für TPE mit Atmosphäre, wie etwa Luft und Rauchgas aus überstöchiometrischer Verbrennung,
— behandelt nicht die Außerbetriebnahme der TPE,
— behandelt nicht Vakuumöfen,
— gilt nicht für Hochöfen, Konverter (in Stahlwerken), Kessel und Anlagen, die nicht unter EN ISO 12100:2010 fallen
— behandelt kein Lärmgefährdungen; diese werden in EN 746 1:1997+A1:2009 behandelt,
— ist nicht auf die Erzeugung und Anwendung von Prozessgas in TPE und zugehörigen Anlagen anwendbar, die vor dem Veröffentlichungsdatum hergestellt werden, und
— beinhaltet auch notwendige Anforderungen für die Benutzerinformation.
Eine TPE, die nach diesem Teil der Normenreihe EN 746 konstruiert wurde, erzeugt im Bereich um sich herum keine potenziell explosionsfähige Atmosphäre. Sie ist auch nicht für die Aufstellung in einem Bereich mit explosionsfähiger oder gefährlicher Atmosphäre vorgesehen.
Dieser Teil der EN 746-Reihe befasst sich mit signifikanten Gefährdungen, die in Anhang A beschrieben sind.
Anhang B enthält eine Tabelle typischer Prozessgase.
Équipements thermiques industriels - Partie 3 : Prescriptions de sécurité pour la génération et l'utilisation des gaz d'atmosphère
La présente partie de la série des EN 746 spécifie les prescriptions de sécurité pour la génération et l'utilisation des gaz d’atmosphère protectrice et réactive qui font partie des équipements thermiques industriels (TPE).
Les prescriptions générales de sécurité communes aux TPE sont fournies dans l'EN 746 1:1997+A1:2009 (voir Introduction).
La présente partie de la série des EN 746 traite des phénomènes dangereux significatifs, des situations et des événements dangereux relatifs à la génération et à l'utilisation des gaz d’atmosphère protectrice et réactive créés par des réactions thermochimiques et leur utilisation dans les TPE qui font partie des TPE tels qu’énumérés à l’Article 4 et à l’Article 5, lorsqu'ils sont utilisés comme prévu et dans les conditions prévues par le fabricant.
La présente partie de la série des EN 746 couvre :
- la tuyauterie en aval du robinet de barrage à commande manuelle et y compris celui-ci,
- les équipements pour la génération des gaz d’atmosphère,
- les équipements supplémentaires pour l’utilisation des gaz d’atmosphère dans les TPE,
- les dispositifs de sécurité, et
- les prescriptions fonctionnelles pour le système de commande relatif à la sécurité
pour la génération et l'utilisation des gaz d’atmosphère protectrice et réactive.
Elle s’applique à la fourniture en gaz d’atmosphère, en gaz source, en gaz inerte et en liquides de procédé aux TPE et à leur évacuation des TPE, confinés aux équipements intégrés dans les TPE.
La présente partie de la série des EN 746 détaille également les phénomènes dangereux significatifs anticipés associés aux systèmes à gaz d'atmosphère et à leur utilisation dans les TPE et spécifie les mesures préventives appropriées pour la réduction ou l'élimination de ces phénomènes dangereux.
Le phénomène dangereux engendré par la pression dans la tuyauterie et les composants couverts par la présente norme correspond à la relation pression maximale/dimensions de groupe 1 telle que décrite dans l'Annexe C.
La présente partie de la série des EN 746 :
- spécifie les prescriptions à satisfaire pour assurer la sécurité des personnes et des biens pendant l'installation, la mise en service, la mise en marche, l’utilisation, l’arrêt et la maintenance,
- ne couvre pas les risques pertinents impliqués dans le système de conduits de fumées lorsqu'il n’est pas considéré comme une partie de TPE,
- ne s'applique pas à l'alimentation en électricité en amont des sectionnements principaux des TPE,
- ne s’applique pas aux TPE pour les dispositifs semi-conducteurs,
- ne s’applique pas aux TPE avec atmosphère, tels que l’air et les gaz de combustion provenant d’une combustion sur-stœchiométrique,
- ne couvre pas la mise hors service des TPE,
- ne couvre pas les fours sous vide,
- ne couvre pas les hauts-fourneaux, les convertisseurs (dans les aciéries), les chaudières et les équipements non couverts par l’EN ISO 12100:2010.
- ne traite pas du phénomène dangereux engendré par le bruit qui est couvert dans l’EN 746-1:1997+A1:2009,
- ne s’applique pas à la génération et à l'utilisation des gaz d’atmosphère dans les TPE et lesinstallations associées qui sont fabriquées avant la date de sa publication, et
- donne les prescriptions nécessaires pour les informations pour l’utilisation.
Un TPE conçu conformément à la présente partie de la série des EN 746 ne crée aucune atmosphère potentiellement explosible dans la zone entourant le TPE et n’est pas conçu pour être situé dans une zone avec une atmosphère potentiellement explosible ou dangereuse.
La présente partie de la série EN 746 traite des phénomènes dangereux significatifs qui sont décrits dans l'Annexe A.
Un tableau des gaz d'atmosphère protectrice et réactive types est donné dans l’Annexe B.
Industrijska termoprocesna oprema - 3. del: Varnostne zahteve za pridobivanje in uporabo atmosferskih plinov
Ta del skupine standardov EN 746 določa varnostne zahteve za proizvodnjo in uporabo zaščitnih in reaktivnih atmosferskih plinov, ki so del industrijske opreme za termoprocesiranje (TPE).
OPOMBA: Splošne varnostne zahteve, ki so skupne za opremo za termoprocesiranje, so navedene v standardu EN 746 1 (glej Uvod).
Ta del skupine standardov EN 746 obravnava večje nevarnosti, nevarne situacije in dogodke v povezavi s pridobivanjem ter uporabo zaščitnih in reaktivnih atmosferskih plinov, ki nastanejo pri termokemičnih reakcijah (in njihovo uporabo v opremi za termoprocesiranje) in so del te opreme, kot je navedeno v točkah 4 in 5, če se uporabljajo v skladu s predvidenim namenom in pod pogoji, ki jih je predvidel proizvajalec.
Ta del skupine standardov EN 746 zajema:
– cevovod za ročnim zapornim ventilom in vključno z njim,
– opremo za pridobivanje atmosferskih plinov,
– dodatno opremo za uporabo atmosferskih plinov pri termoprocesiranju,
– varnostne naprave in
– funkcionalne zahteve za varnostni nadzorni sistem
pri pridobivanju ter uporabi zaščitnih in reaktivnih atmosferskih plinov.
Uporablja se za dobavo atmosferskega plina, izhodnega plina, inertnega plina in procesnih tekočin v opremo za termoprocesiranje oziroma iz nje, omejenega na opremo, vgrajeno v opremo za termoprocesiranje.
Ta del skupine standardov EN 746 podrobno opisuje tudi pričakovane večje nevarnosti, povezane s sistemi atmosferskih plinov in njihovo uporabo v opremi za termoprocesiranje, ter določa ustrezne preventivne ukrepe za zmanjšanje ali odpravo teh nevarnosti.
Nevarnost tlaka v ceveh in komponentah, ki jih zajema ta standard, je znotraj razmerja največjega tlaka/velikosti skupine I, kot je opisano v dodatku C.
Ta del skupine standardov EN 746:
– določa zahteve, ki jih je treba izpolniti za zagotovitev varnosti oseb in premoženja med montažo, pripravo, zagonom, delovanjem, zaustavitvijo in vzdrževanjem,
– ne zajema ustreznih tveganj, povezanih s sistemom kanalov za dimne pline, če niso del opreme za termoprocesiranje,
– se ne uporablja za oskrbo z napajanjem pred glavnim električnim stikalom opreme za termoprocesiranje,
– se ne uporablja za opremo za termoprocesiranje za polprevodniške naprave,
– se ne uporablja za opremo za termoprocesiranje z atmosfero, kot sta zrak in dimni plini zaradi prekomerno stehiometričnega zgorevanja,
– ne zajema razgradnje opreme za termoprocesiranje,
– ne zajema vakuumskih peči,
– ne obravnava nevarnosti hrupa, ki je zajet v standardu EN 746-1:2019,
– se ne uporablja za pridobivanje in uporabo atmosferskega plina v opremi za termoprocesiranje ter povezanih obratih, izdelanih pred datumom objave standarda, in
– podaja potrebne zahteve za informacije za uporabo.
Oprema za termoprocesiranje, zasnovana v skladu s tem delom skupine standardov EN 746, ne ustvarja potencialno eksplozivne atmosfere v okolici te opreme, in ni zasnovana tako, da bi jo bilo mogoče namestiti v območju s potencialno eksplozivno ali nevarno atmosfero.
Preglednica tipičnih zaščitnih in reaktivnih plinov je podana v dodatku B.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2022
Nadomešča:
SIST EN 746-3:2000+A1:2009
Industrijska termoprocesna oprema - 3. del: Varnostne zahteve za pridobivanje in
uporabo atmosferskih plinov
Industrial thermoprocessing equipment - Part 3: Safety requirements for the generation
and use of atmosphere gases
Industrielle Thermoprozessanlagen - Teil 3: Sicherheitsanforderungen für die Erzeugung
und Anwendung von Schutz- und Reaktionsgasen
Équipements thermiques industriels - Partie 3 : Prescription de sécurité pour la
génération et l'utilisation des gaz d'atmosphère
Ta slovenski standard je istoveten z: EN 746-3:2021
ICS:
25.180.01 Industrijske peči na splošno Industrial furnaces in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 746-3
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2021
EUROPÄISCHE NORM
ICS 25.180.01 Supersedes EN 746-3:1997+A1:2009
English Version
Industrial thermoprocessing equipment - Part 3: Safety
requirements for the generation and use of atmosphere
gases
Équipements thermiques industriels - Partie 3 : Industrielle Thermoprozessanlagen - Teil 3:
Prescriptions de sécurité pour la génération et Sicherheitsanforderungen für die Erzeugung und
l'utilisation des gaz d'atmosphère Anwendung von Schutz- und Reaktionsgasen
This European Standard was approved by CEN on 24 October 2021.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 746-3:2021 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 7
2 Normative references . 8
3 Terms and definitions .10
4 Safety requirements and/or protective/risk reduction measures .13
4.1 General .13
4.2 Pipework .13
4.2.1 General .13
4.2.2 Connections .14
4.2.3 Unconnected pipework .15
4.2.4 Galvanic cells .15
4.2.5 Flexible tubing and couplings .15
4.2.6 Marking of pipework .15
4.2.7 Soundness/Tightness .15
4.2.8 Condensate drains .16
4.2.9 Purge points .16
4.2.10 Blow-off and breather pipes or conduits .16
4.2.11 Pressure relief devices and flame arrestors on pipework .16
4.2.12 Pressure oscillations .16
4.2.13 Combustible gas by-pass .17
4.2.14 Isolation of required safety devices .17
4.2.15 Vents .17
4.3 Required safety devices .17
4.3.1 Atmosphere gas control equipment .17
4.3.2 Other safety devices .21
4.4 Requirements for the use of atmosphere gases .22
4.4.1 Prevention of potential ignitable atmospheres .22
4.4.2 Monitoring of TPE doors movements .23
4.4.3 Supervision of the means of ignition at the point of combustible atmosphere gas
discharge .23
4.4.4 Emergency safety purge .23
4.5 Change of atmosphere .24
4.5.1 General .24
4.5.2 Purge with purge gas .24
4.5.3 Purge with self-ignition .25
4.5.4 Change of atmosphere by burning .25
4.5.5 Purge by evacuation .26
4.6 Interfaces to exhaust systems for combustible or toxic atmosphere gases .26
4.6.1 Exhaust of burned gases .26
4.6.2 Gathering of gases without burning and a closed system .27
5 Additional requirements for the generation of atmosphere gases .27
5.1 General .27
5.2 Gas and process liquid supplies .28
5.2.1 Air supplies .28
5.2.2 Reaction mixture supplies. 28
5.2.3 Generated atmosphere gas distribution . 28
5.3 Flame detection . 28
5.4 Burners generating exothermic gases . 29
5.5 Special requirements for different types of generator . 29
5.5.1 Requirements for endothermic generators . 29
5.5.2 Requirements for exothermic generators . 29
5.6 Post-treatment of generated atmosphere gases . 30
6 Verification of the safety requirements and/or measures . 30
7 Information for use . 34
7.1 General . 34
7.2 Marking . 34
7.3 Instruction handbook . 35
7.3.1 General . 35
7.3.2 Description of equipment . 35
7.3.3 Inspection procedures . 35
7.3.4 Commissioning, start-up and operating procedures . 36
7.3.5 Shutdown procedures . 37
7.3.6 Maintenance procedures . 37
7.3.7 Documentation . 38
Annex A (informative) List of significant hazards . 39
Annex B (informative) Typical protective and reactive atmosphere gases . 41
Annex C (normative) Allowed maximum pressure . 43
Annex D (informative) Principle procedures for the change of atmosphere. 48
Annex E (informative) Examples for the determination of safety integrity level SIL and
performance level PL using the risk graph method . 49
Annex F (informative) Basic configuration of piping system of TPE using protective or
reactive atmosphere gases . 61
Annex G (informative) Overview of the terms defined in ISO 13574 (Vocabulary) . 63
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered . 70
Bibliography . 72
European foreword
This document (EN 746-3:2021) has been prepared by Technical Committee CEN/TC 186 “Industrial
thermoprocessing - Safety”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2022, and conflicting national standards shall be
withdrawn at the latest by June 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 746-3:1997+A1:2009.
Based on EN 746-3:1997+A1:2009, ISO 13577-3 was developed in 2016. This ISO standard differs
considerably from the original EN 746-3:1997+A1:2009. The contents of this completely renewed
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of EU
Directive(s) / Regulation(s).
For relationship with EU Directive(s) / Regulation(s), see informative Annex ZA, which is an integral part
of this document.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
Introduction
This document is a type-C standard as stated in EN ISO 12100:2010.
This document is of relevance, in particular, for the following stakeholder groups representing the market
players with regard to machinery safety:
— machine manufacturers (small, medium and large enterprises);
— health and safety bodies (regulators, accident prevention organizations, market surveillance etc.).
Others can be affected by the level of machinery safety achieved with the means of the document by the
above-mentioned stakeholder groups:
— machine users/employers (small, medium and large enterprises);
— machine users/employees (e.g. trade unions, organizations for people with special needs);
— service providers, e.g. for maintenance (small, medium and large enterprises);
— consumers (in case of machinery intended for use by consumers).
The above-mentioned stakeholder groups have been given the possibility to participate at the drafting
process of this document.
The machinery concerned and the extent to which hazards, hazardous situations or hazardous events are
covered are indicated in the Scope of this document.
When requirements of this type-C standard are different from those which are stated in type-A or type-B
standards, the requirements of this type-C standard take precedence over the requirements of the other
standards for machines that have been designed and built according to the requirements of this type-C
standard.
Industrial furnaces and associated thermo-processing equipment (TPE) generally consists of the
following components:
— processing chamber (e.g. steel construction with lining and/or refractory);
— heating systems;
— protective system;
— control and instrumentation system/operator-control level.
EN 746-1:1997+A1:2009 provides the general safety requirements common to TPE. This part of the
EN 746 series details in addition specific safety requirements for generation and use of protective and
reactive atmosphere gases that are part of TPE as listed in the scope. These requirements establish the
minimum acceptable requirements for safety functions required for various processes. Where a process
is not part of the TPE, the requirements do not apply.
For example, the minimum requirements for the opening and closing of doors on a TPE does not apply to
TPE that do not have doors in their design.
NOTE As stated in its scope, EN 746-1:1997+A1:2009 does not cover blast furnaces, converters (in steel plants),
boilers and equipment not covered under EN ISO 12100.
The requirements of protective system are specified in ISO 13577-4:2014.
If a general provision of EN 746-1:1997+A1:2009 counters provisions in this part of the EN 746 series,
the provisions of this part of EN 746 take precedence.
It is assumed that TPE will only be operated and maintained by trained personnel.
1 Scope
This part of the EN 746 series specifies safety requirements for generation and use of protective and
reactive atmosphere gases that are part of industrial thermo-processing equipment (TPE).
The general safety requirements common to TPE are provided in EN 746-1:1997+A1:2009 (see
Introduction).
This part of the EN 746 series deals with significant hazards, hazardous situations and events relevant to
the generation and use of protective and reactive atmosphere gases created by thermochemical reactions
and their use in TPE that are part of TPE as listed in Clause 4 and Clause 5, when used as intended and
under the conditions foreseen by the manufacturer.
This part of the EN 746 series covers:
— pipework downstream of and including the manual isolating valve,
— equipment for the generation of atmosphere gases,
— additional equipment for the use of atmosphere gases in TPE,
— safety devices, and
— functional requirements for safety related control system
for the generation and use of protective and reactive atmosphere gases.
It applies to the supply of atmosphere gas, source gas, inert gas and process liquids to TPE and their
removal from TPE, confined to equipment integrated in the TPE.
This part of the EN 746 series also details the anticipated significant hazards associated with atmosphere
gas systems and their use in TPE and specifies the appropriate preventative measures for the reduction
or elimination of these hazards.
The pressure hazard of the piping and components covered by this standard is within the maximum
pressure/size relationship of group 1 as described in Annex C.
This part of the EN 746 series:
— specifies the requirements to be met to ensure the safety of persons and property during installation,
commissioning, start up, operation, shutdown and maintenance,
— does not cover the relevant risks involved in the flue gas ducting system when it is not considered a
part of TPE,
— is not applicable to utility supply upstream of the TPE main disconnects,
— does not apply to TPE for semi-conductor devices,
— does not apply to TPE with atmosphere, such as air and flue gas from an over stoichiometric
combustion,
— does not cover the decommissioning of the TPE,
— does not cover vacuum furnaces,
— does not cover blast furnaces, converters (in steel plants), boilers and equipment not covered under
EN ISO 12100:2010.
— does not deal with the hazard of noise which is covered in EN 746-1:1997+A1:2009,
— is not applicable to generation and use of atmosphere gas in TPE and associated plant which is
manufactured before the date of its publication, and
— gives the necessary requirements for the information for use.
A TPE designed according to this part of EN 746 series does not create any potentially explosive
atmosphere in the area around the TPE and is not designed to be located in an area with a potentially
explosive or hazardous atmosphere.
This part of the EN 746 series deals with significant hazards which are described in Annex A.
A table of typical protective and reactive gases is given in Annex B.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7-1:1994, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions,
tolerances and designation
ISO 49:1994, Malleable cast iron fittings threaded to ISO 7-1
EN 88-1:2011+A1:2016, Pressure regulators and associated safety devices for gas appliances - Part 1:
Pressure regulators for inlet pressures up to and including 50 kPa
EN 88-2:2007, Pressure regulators and associated safety devices for gas appliances - Part 2: Pressure
regulators for inlet pressures above 500 mbar up to and including 5 bar
EN 161:2011+A3:2013, Automatic shut-off valves for gas burners and gas appliances
EN ISO 228-1:2003, Pipe threads where pressure-tight joints are not made on the threads - Part 1:
Dimensions, tolerances and designation (ISO 228-1:2000)
EN 331:2015, Manually operated ball valves and closed bottom taper plug valves for gas installations for
buildings
EN 334:2019, Gas pressure regulators for inlet pressure up to 10 MPa (100 bar)
EN 746-1:1997+A1:2009, Industrial thermoprocessing equipment - Part 1: Common safety requirements
for industrial thermoprocessing equipment
EN 746-2:2010, Industrial thermoprocessing equipment - Part 2: Safety requirements for combustion and
fuel handling systems
EN 751-1:1996, Sealing materials for metallic threaded joints in contact with 1st, 2nd and 3rd family gases
and hot water - Part 1: Anaerobic jointing compounds
EN 751-2:1996, Sealing materials for metallic threaded joints in contact with 1st, 2nd and 3rd family gases
and hot water - Part 2: Non-hardening jointing compounds
EN 1643:2014, Safety and control devices for gas burners and gas burning appliances - Valve proving
systems for automatic shut-off valves
EN 1854:2010, Pressure sensing devices for gas burners and gas burning appliances
EN 10241:2000, Steel threaded pipe fittings
EN 10242:1994, Threaded pipe fittings in malleable cast iron
EN ISO 5817:2014, Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding
excluded) - Quality levels for imperfections (ISO 5817:2014)
ISO 7005-1:2011, Pipe flanges — Part 1: Steel flanges for industrial and general service piping systems
ISO 7005-2:1988, Metallic flanges — Part 2: Cast iron flanges
EN ISO 8434-1:2018, Metallic tube connections for fluid power and general use - Part 1: 24° cone connectors
(ISO 8434-1:2018, Corrected version 2018-10)
ISO 8434-2:2007, Metallic tube connections for fluid power and general use — Part 2: 37 degree flared
connectors
ISO 8434-3:2005, Metallic tube connections for fluid power and general use — Part 3: O-ring face seal
connectors
EN ISO 10352:2020, Fibre-reinforced plastics - Moulding compounds and prepregs - Determination of mass
per unit area and fibre mass per unit area (ISO 10352:2020)
EN ISO 12100:2010, Safety of machinery - General principles for design - Risk assessment and risk reduction
(ISO 12100:2010)
EN 14382:2019, Gas safety shut-off devices for inlet pressure up to 10 MPa (100 bar)
ISO 13574:2015, Industrial furnaces and associated processing equipment — Vocabulary
ISO 13577-4:2014, Industrial furnace and associated processing equipment — Safety — Part 4: Protective
systems
EN ISO 13849-1:2015, Safety of machinery - Safety-related parts of control systems - Part 1: General
principles for design (ISO 13849-1:2015)
EN ISO 19879:2021, Metallic tube connections for fluid power and general use - Test methods for hydraulic
fluid power connections (ISO 19879:2021)
EN 60204-1:2018, Safety of machinery - Electrical equipment of machines - Part 1: General requirements
EN 60730-2-5:2015, Automatic electrical controls - Part 2-5: Particular requirements for automatic
electrical burner control systems
EN 61508-1:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 1: General requirements
This document is impacted by the amendments EN 10242:1994/A1:1999 and EN 10242:1994/A2:2003.
EN 61508-2:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems
EN 61508-3:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 3: Software requirements
EN 61508-4:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 4: Definitions and abbreviations
EN 61508-5:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 5: Examples of methods for the determination of safety integrity levels
EN 61508-6:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
EN 61508-7:2010, Functional safety of electrical/electronic/programmable electronic safety-related
systems - Part 7: Overview of techniques and measures
EN 61511-1:2017, Functional safety - Safety instrumented systems for the process industry sector - Part 1:
Framework, definitions, system, hardware and application programming Requirements
EN 61511-1:2017/A1:2017, Functional safety - Safety instrumented systems for the process industry sector
- Part 1: Framework, definitions, system, hardware and application programming Requirements
EN 61511-2:2017, Functional safety - Safety instrumented systems for the process industry sector - Part 2:
Guidelines for the application of IEC 61511-1
EN 61511-3:2017, Functional safety - Safety instrumented systems for the process industry sector - Part 3:
Guidance for the determination of the required safety integrity levels
EN 62061:2005, Safety of machinery — Functional safety of safety-related electrical, electronic and
programmable electronic control systems (IEC 62061:2005)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13574:2015 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
NOTE See Annex G for the list of terms specified in ISO 13574:2015.
This document is impacted by the amendments EN 62061:2005/A1:2013 and EN 62061:2005/A2:2015.
3.1
safety shutdown
function that takes the TPE out of operation and brings it in a defined safe state
Note 1 to entry: The definition is different from safety shutdown according ISO 13574:2015, 2.166 which is
applicable to ISO 13577-2:2014 and EN 746-2:2010.
3.2
flame failure
loss of flame from the normally detected position by any cause other than the action of de-energising the
automatic shut-off valves system
Note 1 to entry: The term is used in ISO 13577-2 and EN 746-2:2010.
3.3
gas generator
equipment that converts or modifies a fluid or a mixture of fluids (gaseous or liquid) into a gas which can
be utilized as the controlled atmosphere within the thermo-processing equipment
3.4
endothermic generator
gas generator that produces atmosphere gas by an endothermic reaction
3.5
exothermic generator
gas generator that produces atmosphere gas by an exothermic reaction
3.6
combustible atmosphere gas
any gas mixture that is capable of forming ignitable mixtures with air or oxygen under the conditions of
temperature and pressure used in the process, according to the lower explosion level (LEL) of the actual
gas mixture
3.7
inert gas
non-combustible gas which will not support combustion and does not react at all
Note 1 to entry: Nitrogen, helium and argon are typical inert gases.
3.8
purge gas
gas which can be used to purge a TPE
Note 1 to entry: A purge gas can safely be used for pre- and post-purging of cold and hot enclosures of TPE.
Note 2 to entry: Typically, purge gases are nitrogen, argon, helium and lean exothermic gas.
3.9
safety purge volume
volume of purge gas needed to displace either air or a combustible gas from a furnace chamber/enclosure
to achieve a volume fraction of 1 % or less oxygen and/or a non-combustible atmosphere gas and/or
25 % of the lower flammability limit
Note 1 to entry: Typically, this will be a volume equal to five times the volume of the thermo-processing
equipment chamber to be purged, if the purging gas is an inert gas.
Note 2 to entry: Non-combustible atmosphere gas as defined in 3.6.
3.10
multi-turn valve
valve which, in order to operate from the fully closed to the fully open position, requires a number of
revolutions of the operating key or handwheel to be completed
3.11
safe ignition temperature
minimum temperature at which spontaneous, safe auto-ignition of combustible gases occurs
Note 1 to entry: The safe ignition temperature has been established at 750 °C.
3.12
toxic atmosphere gas
gas which, in addition to having asphyxiating properties, also acts as a poison
3.13
internal gas generator
gas generator integrated into or directly connected to a TPE
3.14
gas control equipment
centralized mounting of components such as: pipework, safety components, pressure and flow
accessories, assembled in a functional unit
3.15
atmosphere gas
gas that is supplied into or formed in TPE in accordance with a defined specification for thermo-
processes
Note 1 to entry: Atmosphere gas is used to react with the material processed or to avoid a reaction with the
material processed.
3.16
process liquids
liquids that are supplied to TPE to create an atmosphere gas
4 Safety requirements and/or protective/risk reduction measures
4.1 General
Protective and reactive atmosphere gases in TPE are used to react with the material processed or to avoid
a reaction with the material processed. Protective and reactive atmosphere gases are fed into the TPE at
determined points and are discharged out of the TPE at determined points too.
Protective and reactive atmosphere gases shall only be used in TPE that has been constructed to avoid
leakage of the protective and reactive atmosphere gases out of the TPE or ambient air into the TPE.
Machinery shall comply with the safety requirements and/or protective/risk reduction measures of this
clause. In addition, the machine shall be designed according to the principles of EN ISO 12100:2010 for
relevant but not significant hazards which are not dealt with by this document.
Electrical circuits shall be designed in accordance with EN 60204-1:2018.
A risk assessment according to EN ISO 12100:2010 shall be carried out. Safety functions shall be designed
in accordance with ISO 13577-4:2014, where the use of standards for functional safety EN 62061:2005,
EN ISO 13849-1:2015, EN 61511-1:2017, EN 61511-1:2017/A1:2017, EN 61511-2:2017,
EN 61511-3:2017, EN 61508-1:2010, EN 61508-2:2010, EN 61508-3:2010, EN 61508-4:2010,
EN 61508-5:2010, EN 61508-6:2010 and EN 61508-7:2010 is included. Annex E provides information
for the determination of the SIL or PL of safety-related functions covered in this part of EN 746 series.
CAUTION — Toxic hazards for persons occur at lower concentrations than hazards by generation of
ignitable atmospheres.
NOTE Requirements for maximum allowable concentrations values are identified by national regulations.
The choice of materials shall consider the specific properties of the engaged gas and liquids (e.g. non-
ferrous metals are not suitable for NH and natural rubber is not suitable for natural gas).
For basic configuration of piping system of TPE using atmosphere gas, see Annex F.
4.2 Pipework
4.2.1 General
The pipework design shall take into account the composition and properties (e.g. pressure, temperature,
corrosiveness, specific gravity, velocity) of gas and liquids and the need for venting, purging and cleaning.
Due to durability, steel is the preferred material for pipes and components but where appropriate and
the same safety levels can be achieved, then other materials may be utilized. Such materials and
conditions of service shall be specified in the instruction handbook.
Oscillations which may cause damage to pipework, components or safety systems shall be prevented (by
firm anchoring and/or use of flexible couplings).
Pipework shall be arranged so that safe isolation of atmosphere gas and process liquids to all parts of the
TPE can be guaranteed
NOTE An example is shown in Figure F.1.
The isolation method shall be clearly identified (e.g. by removable spool piece painted in red, blanking
plate), and provision for blanking opened pipes shall be provided secured against loss (e.g. by an attached
chain).
For steel pipes, compliance with EN ISO 3183:2019, EN 13480-2:2017, or EN 10255 is considered
appropriate. For copper pipes, compliance with EN 1057 is considered appropriate. Copper soldering
connections shall not be used for gas carrying parts where the temperature could exceed 100 °C .
Threaded pipe fittings shall comply with EN 10241:2000 or EN 10242:1994 .
Use of brass or other copper alloy components in contact with ammonia or dissociated ammonia is not
allowed.
4.2.2 Connections
Pipework connections shall be metallic and shall be of threaded, compression, press fittings, flanged,
welded or brazed types. The number of connections shall be kept to a minimum.
Threaded connections shall be used only for the following pressure/diameter combinations:
— pressures up to 15 kPa and diameters up to DN 100;
— pressures up to 200 kPa and diameters up to DN 50;
— pressures up to 500 kPa and diameters up to DN 25;
— pressures up to 1 MPa and diameters up to DN 15.
For other combinations of pressures and diameters, connections shall be made by means of welded
flanges or welded joints. The number of connections shall be kept to a minimum.
For fittings according to ISO 49:1994, the following limitations shall be observed:
— fittings are class “A”;
— maximum allowed pressure is 50 kPa;
— for dimensions DN 25 or less, the maximum pressure is 500 kPa.
Where the equipment has a threaded connection, this thread shall comply with EN ISO 228-1:2003 or
ISO 7-1:1994, as appropriate. The use of threads complying with EN ISO 228-1:2003 is limited to
diameter up to DN 50. In the case of threads according to EN ISO 228-1:2003, the tightness shall be
ensured by a ring gasket. Hemp shall not be used in threaded connections unless reinforced with a
suitable sealant.
Sealants for threads according to ISO 7-1:1994 shall comply with EN 751-1:1996 or EN 751-2:1996 as
appropriate.
Other threaded connections shall only be used providing they ensure tight connections and are suitably
identified.
The design of pipework shall be such as to avoid tensile loading of the joints.
Compression fittings shall comply with EN ISO 8434-1:2018, ISO 8434-2:2007 and ISO 8434-3:2005 or
EN ISO 19879:2021. They shall only be used for pressures up to 500 kPa and diameters up to 42 mm.
Where press fitting according to EN ISO 10352:2020 are used, they shall comply with the application
restrictions (e.g. temperature, vibration, gas, liquids).
Paragraph is not in the body text of ISO 13577-3.
Paragraph is not in the body text of ISO 13577-3.
Any pipe passing through an unventilated space shall not have a connection except welded joints.
Flanges shall comply with ISO 7005-1:2011 and ISO 7005-2:1988 as appropriate.
Arc welding shall comply with EN ISO 5817:2014, quality Level C.
4.2.3 Unconnected pipework
Any unconnected pipework shall be plugged, capped or blank flanged by means of metallic parts.
4.2.4 Galvanic cells
Corrosion in pipelines can be caused by the unintentional formation of a galvanic cell. Galvanic cells are
formed when materials with different electrochemical potentials are conductively connected (e.g. copper
screw in an aluminium sheet, stainless steel sheet screwed to steel sheet). This shall be taken into account
when selecting the material for piping.
4.2.5 Flexible tubing and couplings
Flexible tubing shall comply with the general requirements of 4.2.1, together with the following:
— shall be as short as practicable;
— shall be suitable for the maximum and minimum working temperatures;
— shall be suitable for a pressure 1,5 times the working operating pressure (with a minimum of 15 kPa),
at the maximum and minimum working temperatures;
— shall have a directly accessible, upstream manual shut-off valve;
— shall be mounted in such a way as to avoid distortion, whiplash and damage;
— shall have end fittings as integral parts of the tubing;
— shall be constructed from suitable material both metallic and/or non-metallic selected for the
application duty and not be easily damaged.
— Couplings for removable equipment shall ensure a gastight connection with the equipment
connected and disconnected.
4.2.6 Marking of pipework
Marking of pipework is required which enable medium and flow direction to be identified.
NOTE Identification of gas pipework is dealt with by national regulations.
4.2.7 Soundness/Tightness
The pipework shall be tight and shall be designed to withstand the internal pressure. After assembly, the
pipework shall be submitted to its test pressure and tested for tightness. The test pressure shall be not
less than 1,1 times the maximum working pressure at any point with a minimum of 5 kPa.
The external leakage rate shall not give rise to a dangerous condition, combustible and/or toxic, in the
foreseen circumstances of the equipment or installation. The frequency of testing to determine the
external leakage shall be specified in the instruction handbook.
3 3
NOTE It is generally agreed that an external leak rate of ~1 dm (n)/h for gas or 1 cm (n)/h for methanol will
not create a dangerous condition in typical ventilated industrial installation. The actual leak rate will depend upon
the volume, number of connections, test gas, number of valves and component parts contained.
The external leak rate test method shall take into account the volume, number of connections, test gas,
number of valves and component parts contained and temperature. Methods of testing shall include
spray bubble leak identification and/or pressure decay test.
4.2.8 Condensate drains
In cases where condensates can create a hazard, means shall be provided at the lowest points of the
equipment for draining any condensate. When moist gases are being used, condensate drains of a suitable
type shall be installed. Any condensate drains, siphons, etc. shall be in a position such that they can be
easily checked. Combustible condensates shall be collected by an appropriate means (e.g. piped into a
container).
Valves in condensate drains shall be suitably plugged, capped or blank flanged by metallic parts.
4.2.9 Purge points
Means shall be provided to facilitate purging of pipework during commissioning and maintenance to
prevent the forming of an ignitable atmosphere or build-up of flammable substances.
All distribution pipework and storage vessels for atmosphere gas shall be designed so that purging
procedures in accordance with 4.5 or in such a manner which excludes the simultaneous presence of
combustible gas/air mixtures and an ignition source can be done. Each purging point shall be provided
with a valve which shall either
— be fitted with a device to prevent unauthorised operation, or
— be blanked off during normal operation of the plant.
4.2.10 Blow-off and breather pipes or conduits
Where blow-off or breather pipes or conduits are fitted on regulators or relief valves or vent valves,
adequate means shall be provided to facilitate the venting of gas from the system to a safe discharge area.
In case breathers or blow-off pipes are gathered, the cross section of the collector shall be suitable to
evacuate simultaneously total flow rates of the exhaust sources.
4.2.11 Pressure relief devices and flame arrestors on pipework
For equipment designed for situations in which flash-backs can occur, flame arrestors and/or pressure
relief devices shall be fitted.
Pressure relief devices shall be designed to yield at a pressure below the design pressure of the pipework
and shall be positioned such that the discharge flow and the pressure relief device does not constitute a
risk to the equipment, personnel or third parties.
A flash-back shall trigger an alarm. The required measures after a flash-back shall be described in the
instruction handbook.
4.2.12 Pressure oscillations
The pipework shall be designed so as to avoid the possibility of gas velocities and pressure fluctuations
causing oscillations which could cause damage to pipework, components or safety systems (e.g. by
designing the correct sizing of pipes or using pressure regulators).
4.2.13 Combustible gas by-pass
By-passes shall not be fitted in parallel with any item of safety equipment.
This requirement shall not apply to valve proving systems (see EN 1643:2014 ) on automatic shut-off
valves.
4.2.14 Isolation of required safety devices
Required safety devices (e.g. pressure switche
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