SIST EN ISO 7291:2012

Gas welding equipment - Pressure regulators for manifold systems used in welding, cutting and allied processes up to 30 MPa (300 bar) (ISO 7291:2010)

This standard specifies requirements and test methods for pressure regulators in manifold systems for wel-ding, cutting and allied processes. This is applicable to pressure regulators normally used for compressed gases up to 300 bar (30 MPa), for dissolved acetylene, methylacetylene-propadiene-mixtures (MPS) and carbondioxide (CO2), to regulate the pressure at the outlet of high-pressure lines from manifold gas cylinders. It is not applicable to pressure regulators fitted directly to the gas cylinders, as defined in ISO 2503 or to pressure regulators for liquefied petroleum gases.

Gasschweißgeräte - Hauptstellendruckregler für Schweißen, Schneiden und verwandte Prozesse bis 30 MPa (300 bar) (ISO 7291:2010)

Diese Internationale Norm legt fest die Anforderungen und die Prüfmethoden für Hauptstellendruckregler, die angewendet werden für:
   komprimierte Gase bis zu 300 bar )  (30 000 kPa);
   gelöstes Acetylen;
   verflüssigte Erdgase (LPG);
   Methylazetylen-Propadien-Gemische (MPS);
   Kohlendioxid (CO2);
   Schweißen, Schneiden und verwandte Prozesse.
Sie gilt nicht für unmittelbar an Gasflaschen angebrachte Druckregler, wie in ISO 2503 enthalten, oder für Druckregler für Flüssiggase.

Matériel de soudage aux gaz - Détendeurs de centrale de bouteilles pour le soudage, le coupage et les techniques connexes jusqu'à 30 MPa (300 bar) (ISO 7291:2010)

L'ISO 7291:2010 spécifie les exigences et les méthodes d'essai relatives aux détendeurs de centrale de bouteilles utilisés pour le soudage, le coupage et les techniques connexes, pour: a) les gaz comprimés jusqu'à 30 MPa (300 bar); b) l'acétylène dissous; c) les gaz de pétrole liquéfiés (GPL); d) les mélanges de méthylacétylène-propadiène (MPS); e) le dioxyde de carbone (CO2).
Elle n'est pas applicable aux détendeurs directement fixés sur les bouteilles de gaz, tels que définis dans l'ISO 2503.

Oprema za plamensko varjenje - Glavni regulatorji tlaka plina za varjenje, rezanje in sorodne postopke za tlake do 30 MPa (300 bar) (ISO 7291:2010)

Ta mednarodni standard določa zahteve in preskusne metode za glavne regulatorje tlaka plina, ki se uporabljajo za: - stisnjene pline do 30 000 kPa (300 bar); - raztopljeni acetilen; - utekočinjene naftne pline (UNP); - metilacetilen-propadienove zmesi (MPS); - ogljikov dioksid (CO2); - za uporabo pri varjenju, rezanju in sorodnih postopkih. Ne velja za regulatorje tlaka, nameščene neposredno na plinske jeklenke, kot je opredeljeno v ISO 2503.

General Information

• Status: Published
• Publication Date: 28-Nov-2011
• ICS: 23.060.40 - Pressure regulators
• ICS: 25.160.30 - Welding equipment
• Technical Committee: VAR - Welding
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 23-Nov-2011
• Due Date: 28-Jan-2012
• Completion Date: 29-Nov-2011
• Ref Project: EN ISO 7291:2010 - Gas welding equipment - Pressure regulators for manifold systems used in welding, cutting and allied processes up to 30 MPa (300 bar) (ISO 7291:2010)

Relations

• Replaces: SIST EN ISO 7291:2002 - Gas welding equipment - Pressure regulators for manifold systems used in welding, cutting and allied processes up to 300 bar (ISO 7291:1999)
• Effective Date: 01-Jan-2012
• Amended By: SIST EN ISO 7291:2012/A1:2015 - Gas welding equipment - Pressure regulators for manifold systems used in welding, cutting and allied processes up to 30 MPa (300 bar) (ISO 7291:2010/AMD 1:2015)
• Effective Date: 01-Jul-2015
• Replaces: SIST EN ISO 7291:2002 - Gas welding equipment - Pressure regulators for manifold systems used in welding, cutting and allied processes up to 300 bar (ISO 7291:1999)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 7291:2012
01-januar-2012
1DGRPHãþD
SIST EN ISO 7291:2002

Oprema za plamensko varjenje - Glavni regulatorji tlaka plina za varjenje, rezanje

in sorodne postopke za tlake do 30 MPa (300 bar) (ISO 7291:2010)

Gas welding equipment - Pressure regulators for manifold systems used in welding,

cutting and allied processes up to 30 MPa (300 bar) (ISO 7291:2010)

Gasschweißgeräte - Hauptstellendruckregler für Schweißen, Schneiden und verwandte

Prozesse bis 30 MPa (300 bar) (ISO 7291:2010)

Matériel de soudage aux gaz - Détendeurs de centrale de bouteilles pour le soudage, le

coupage et les techniques connexes jusqu'à 30 MPa (300 bar) (ISO 7291:2010)
Ta slovenski standard je istoveten z: EN ISO 7291:2010
ICS:
23.060.40 7ODþQLUHJXODWRUML Pressure regulators
25.160.30 Varilna oprema Welding equipment
SIST EN ISO 7291:2012 de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 7291:2012
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SIST EN ISO 7291:2012
EUROPEAN STANDARD
EN ISO 7291
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2010
ICS 25.160.30 Supersedes EN ISO 7291:2001
English Version
Gas welding equipment - Pressure regulators for manifold
systems used in welding, cutting and allied processes up to 30
MPa (300 bar) (ISO 7291:2010)

Matériel de soudage aux gaz - Détendeurs de centrale de Gasschweißgeräte - Hauptstellendruckregler für

bouteilles pour le soudage, le coupage et les techniques Schweißen, Schneiden und verwandte Prozesse bis 30

connexes jusqu'à 30 MPa (300 bar) (ISO 7291:2010) MPa (300 bar) (ISO 7291:2010)
This European Standard was approved by CEN on 23 October 2010.

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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7291:2010: E

worldwide for CEN national Members.
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SIST EN ISO 7291:2012
EN ISO 7291:2010 (E)
Contents Page

Foreword ..............................................................................................................................................................3

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SIST EN ISO 7291:2012
EN ISO 7291:2010 (E)
Foreword

This document (EN ISO 7291:2010) has been prepared by Technical Committee ISO/TC 44 "Welding and

allied processes" in collaboration with Technical Committee CEN/TC 121 “Welding” 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 May 2011, and conflicting national standards shall be withdrawn at the

latest by May 2011.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 7291:2001.

According to the CEN/CENELEC Internal Regulations, the national standards organizations 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, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
Endorsement notice

The text of ISO 7291:2010 has been approved by CEN as a EN ISO 7291:2010 without any modification.

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SIST EN ISO 7291:2012
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SIST EN ISO 7291:2012
INTERNATIONAL ISO
STANDARD 7291
Third edition
2010-11-01
Gas welding equipment — Pressure
regulators for manifold systems used in
welding, cutting and allied processes up
to 30 MPa (300 bar)
Matériel de soudage aux gaz — Détendeurs de centrale de
bouteilles pour le soudage, le coupage et les techniques connexes
jusqu'à 30 MPa (300 bar)
Reference number
ISO 7291:2010(E)
ISO 2010
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
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All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

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Published in Switzerland
ii © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
Contents Page

Foreword ............................................................................................................................................................iv

1 Scope......................................................................................................................................................1

2 Normative references............................................................................................................................1

3 Terms and definitions ...........................................................................................................................2

4 Units........................................................................................................................................................3

4.1 Pressure .................................................................................................................................................3

4.2 Flow.........................................................................................................................................................3

4.3 Temperature...........................................................................................................................................3

5 Manufacturing requirements................................................................................................................3

5.1 Materials .................................................................................................................................................3

5.2 Design, machining and assembly........................................................................................................4

6 Physical characteristics .......................................................................................................................6

6.1 General ...................................................................................................................................................6

6.2 Pressures ...............................................................................................................................................7

6.3 Flow rates...............................................................................................................................................7

6.4 Operating characteristics .....................................................................................................................9

7 Marking.................................................................................................................................................10

7.1 Pressure regulator...............................................................................................................................10

7.2 Pressure relief devices .......................................................................................................................10

8 Instructions for use.............................................................................................................................10

9 Type test procedure ............................................................................................................................11

9.1 General .................................................................................................................................................11

9.2 Test conditions....................................................................................................................................11

9.3 Functional tests...................................................................................................................................12

9.4 Tests for mechanical resistance of pressure regulators ................................................................14

9.5 Test for durability of markings...........................................................................................................18

Bibliography......................................................................................................................................................19

© ISO 2010 – All rights reserved iii
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 7291 was prepared by Technical Committee ISO/TC 44, Welding and allied processes, Subcommittee

SC 8, Equipment for gas welding, cutting and allied processes.

This third edition cancels and replaces the second edition (ISO 7291:1999), which has been technically

revised.

Requests for official interpretations of any aspect of this International Standard should be directed to the

Secretariat of ISO/TC 44/SC 8 via your national standards body. A complete listing of these bodies can be

found at www.iso.org.
iv © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
INTERNATIONAL STANDARD ISO 7291:2010(E)
Gas welding equipment — Pressure regulators for manifold
systems used in welding, cutting and allied processes up
to 30 MPa (300 bar)
1 Scope

This International Standard specifies requirements and test methods for pressure regulators in manifold

systems used in welding, cutting, and allied processes for:
a) compressed gases up to 30 MPa (300 bar);
b) dissolved acetylene;
c) liquefied petroleum gases (LPG);
d) methylacetylene-propadiene-mixtures (MPS);
e) carbon dioxide (CO ).
[2]

It is not applicable to pressure regulators fitted directly to the gas cylinders, as defined in ISO 2503 .

2 Normative references

The following referenced documents are indispensable for the application 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 5171, Gas welding equipment — Pressure gauges used in welding, cutting and allied processes

ISO 9090, Gas tightness of equipment for gas welding and allied processes

ISO 9539, Gas welding equipment — Materials for equipment used in gas welding, cutting and allied

processes

ISO 15296, Gas welding equipment — Vocabulary — Terms used for gas welding equipment

1) The value 30 MPa relates to maximum cylinder filling pressure at 15 °C.
© ISO 2010 – All rights reserved 1
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 15296 and the following apply.

3.1
pressure regulator for manifold systems

device for regulating a generally variable inlet pressure to as constant as possible an outlet pressure when

controlling the output of a manifold of cylinders

NOTE The diagram of the pressure regulator is an example only. Optional design characteristics are to be

compatible with the safety requirements specified in this International Standard. See Figure 1.

Key
1 pressure regulator body
2 inlet connector
3 upstream pressure gauge
4 relief valve
5 downstream pressure gauge
6 outlet connector
7 pressure regulator cover
8 pressure adjusting screw
Figure 1 — Example of pressure regulators and designation of its components
3.2
manifold

assembly of devices generally linking two or more gas sources coupled to a user pipeline system, delivering a

regulated pressure under specified safe conditions

NOTE A manifold can include components like collectors, safety devices, and pressure regulators.

2 © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
4 Units
4.1 Pressure

The pressures measured are gauge pressures and are expressed in megapascals or bars.

4.2 Flow

Flow rates are measured in cubic metres per hour corrected to a standard atmosphere , taking into account

the relevant conversion coefficient for the gas used (see Table 1).
Table 1 — Conversion coefficient, U
Conversion coefficient
Test gas
LPG, e.g.
air oxygen nitrogen argon hydrogen helium acetylene
propane
air 1 0,950 1,02 0,851 3,81 2,695 1,05 0,800 0,808
nitrogen 0,983 0,930 1 0,837 3,75 2,65 1,03 0,784 0,792
The conversion coefficient, U, is given by Equation (1):
U = (1)
where
γ is the density of test gas;
γ is the density of gas used.
4.3 Temperature
Temperatures are measured in degrees Celsius.
5 Manufacturing requirements
5.1 Materials
Materials for pressure regulators shall conform to the requirements of ISO 9539.
2) Pressure exceeding atmospheric pressure.
[1]
3) A standard atmosphere at 23 °C and 0,101 3 MPa (1,013 bar), ISO 554 .
© ISO 2010 – All rights reserved 3
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
5.2 Design, machining and assembly
5.2.1 Oxygen pressure regulators

Pressure regulators for oxygen shall be designed and manufactured giving consideration to the possibility of

internal ignition. Pressure regulators for oxygen shall not ignite or show evidence of burning when submitted

to the ignition test in 9.4.4.

All components and accessories shall be thoroughly cleaned and degreased before assembly.

5.2.2 Acetylene pressure regulators

Pressure regulators shall be designed and constructed in such a way that they withstand acetylene

decomposition. The test shall be carried out in accordance with 9.4.6.
5.2.3 Connections
5.2.3.1 Inlet connections
Choice of inlet connections is left to the manufacturer's discretion.
5.2.3.2 Outlet connections
Choice of outlet connection is left to the manufacturer's discretion.
5.2.4 Filter

A particle filter, having an effective cross-section compatible with the discharge, shall be mounted within or

directly fitted to the pressure regulator upstream of the pressure regulator valve. The filter shall not be

removable without the use of a tool. The filter shall retain particles of size greater than or equal to 0,1 mm.

5.2.5 Pressure-adjusting device

This device shall be designed in such a way that it is not possible for the pressure regulator valve to be held in

the open position, for example, as a consequence of the spring being compressed fully (to its solid length).

If the dimensions of the pressure-adjusting screw are such as to prevent the spring becoming fully

compressed, then the pressure-adjusting screw shall not be removable.

Using the adjusting device, it shall not be possible to obtain a pressure at which the pressure relief device

vents.
5.2.6 Pressure gauges

The pressure regulator shall be supplied with upstream and downstream pressure gauges complying with the

functions and safety requirements specified in ISO 5171.

Inlet connection threads shall conform to international, regional or national standards for pressure gauges.

Pressure gauges shall be designed and constructed in such a way that they withstand acetylene

decomposition. The test shall be carried out in accordance with 9.4.7.
4 © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
5.2.7 Gas leakage
5.2.7.1 General

The pressure regulator shall be gastight to the exterior, e.g. to the atmosphere, and internally, i.e. between the

high-pressure and low-pressure parts. At all normal pressures for relevant gases, the leakage shall not

exceed the limits specified in 5.2.7.2 and 5.2.7.3.
5.2.7.2 External leakage

Pressure regulators shall be gastight to the atmosphere and shall conform to the requirements of ISO 9090.

The total leakage shall be less than 10 cm /h.
5.2.7.3 Internal leakage, q

Maximum allowable internal leakage, q , in cubic centimetres per hour, of the pressure regulator is a function

of its standard discharge, Q , in cubic metres per hour (see Figure 2).
3 3
For Q < 30 m /h, q < 50 cm /h and
1 f
3 3
for Q > 1 500 m /h, q < 2 500 cm /h.
1 f

Between these two pairs of values the allowable leakage rate shall satisfy Condition (2):

u (2)
Key
q internal leakage
Q standard discharge
Figure 2 — Allowable internal leakage rates
5.2.8 Mechanical resistance
5.2.8.1 Resistance to internal pressure

Pressure regulators shall be designed and constructed in such a way that the application of pressures given in

Table 2 in the high-pressure and low-pressure chambers does not lead to permanent deformation

(see 9.4.2.1).
© ISO 2010 – All rights reserved 5
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
Table 2 — Test pressures
Gas High-pressure chambers Low-pressure chambers
Oxygen and other compressed gases,
p u 1 MPa (10 bar)
3 MPa (30 bar)
Acetylene
MPS
1,2 × 1,5 × p
Oxygen and other compressed gases,
6 MPa (60 bar)
1 MPa (10 bar) < p u 2 MPa (20 bar)
Oxygen and other compressed gases,
p > 2 MPa (20 bar)
5.2.8.2 Pressure retention of the low-pressure side

Pressure regulators shall be designed and constructed so that if the low-pressure chamber of the pressure

regulator, or intermediate chamber in the case of two-stage pressure regulators, is in direct communication

with a full cylinder of gas, for example, the pressure regulator valve is held in the open position and the outlet

connection is closed by an attached stop valve or a blind plug, the high-pressure gas shall either be safely

retained or vented (see 9.4.2.2).

A pressure relief device may be fitted to the manifold pressure regulator to fulfil this requirement. For

flammable gases, a means of safely venting shall be provided.
6 Physical characteristics
6.1 General
The symbols used are given in Table 3.
Table 3 — Symbols used
Symbol Explanation
i irregularity coefficient
p pressure
p nominal inlet pressure
p nominal outlet pressure
p acetylene outlet pressure used for calculation of R (see 9.3.3.3)
p acetylene outlet pressure used for calculation of i (see 9.3.5.3)
p upstream pressure for type testing: p = 2 p + 1 (0,100 MPa)
3 3 2
p stabilized outlet pressure (stabilization after flow ceases)

p highest or lowest outlet pressure during a test of determination of irregularity coefficient according to 6.4.2

p inlet pressure
p outlet pressure
Q standard (nominal) discharge
Q maximum discharge
max
q internal leakage
R coefficient of pressure increase upon closure
t time
6 © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
6.2 Pressures
6.2.1 Nominal inlet pressure, p
Nominal inlet pressure specified by the manufacturer.
6.2.2 Nominal outlet pressure, p

Nominal outlet pressure for the standard discharge, Q , specified by the manufacturer.

NOTE This nominal pressure is defined for testing, and can be above the normal operating pressure of the pressure

regulator.
For acetylene pressure regulators, the standard discharge is measured at p .
6.2.3 Outlet pressure for acetylene pressure regulators

For acetylene pressure regulators the outlet pressures p , p , and p shall not exceed 0,150 MPa (1,5 bar) in

2 4 5

any case, but lower values may be applicable depending on the intended maximum pipeline diameter.

NOTE The nominal outlet pressure, p , is a function of the nominal diameter of the distribution line. It is possible that

maximum values for the outlet pressures are specified in national standards and regulations.

6.3 Flow rates
6.3.1 Maximum discharge, Q
max

The maximum discharge which the pressure regulator can provide for an upstream pressure, p , in

megapascals, which is given by the expression:
p = 2 p + 1 (3)
3 2

NOTE It is possible that Q is lower than the actual flow, which the pressure regulator can allow under different

max
conditions.
6.3.2 Standard discharge, Q

The standard discharge for the pressure regulator is defined by the manufacturer for a particular gas

(see Figure 3) at the rated outlet pressure p (see Table 4).
The following condition shall be satisfied: Q W 0,5 Q .
1 max
For acetylene pressure regulators, the standard discharge is measured at p .
© ISO 2010 – All rights reserved 7
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
Key
p outlet pressure p maximum stabilized outlet pressure
o 4,max
p nominal outlet pressure Q flow rate
p upstream pressure for type testing Q standard discharge
3 1
p stabilized outlet pressure Q maximum discharge
4 max
Figure 3 — Flow rate characteristics
Table 4 — Pressures
Nominal inlet pressure Nominal outlet pressure
Gas p p
1 2
MPa (bar) MPa (bar)
0,2 (2)
0,4 (4)
0,6 (6)
Oxygen and other compressed gases
0 to 30 (0 to 300)
up to 30 MPa (300 bar)
1,0 (10)
1,25 (12,5)
2,0 (20)
u 0,15 (u 1,5)
Dissolved acetylene 2,5 (25)
0,15 (1,5)
MPS
2,5 (25)
0,4 (4)
0,2 (2)
0,4 (4)
20 (200)
1,0 (10)
For acetylene, p , p and p shall be less than or equal to 0,150 MPa (1,5 bar).
2 4 5

If other values for the application of pressure are required, they should be selected preferably from the R20 series containing the

values given.

Vapour pressure for MPS at 65 °C. This value shall change depending on components of the gas mixture.

Pressure for CO at 53 °C.
Pressure relating to maximum cylinder charging pressure at 15 °C.
8 © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
6.4 Operating characteristics
6.4.1 Coefficient of pressure increase upon closure, R
This coefficient is defined by:
pp−
R = (4)
where

p is the nominal outlet pressure (for acetylene pressure regulators, p = p , see Table 3);

2 2 2R

p is the stabilized outlet pressure (stabilization pressure) noted 1 min after discharge ceases — for

acetylene pressure regulators, set to initial conditions Q , p for inlet p .
1 2R 3

For standard discharge Q , the coefficient R of pressure increase upon closure shall be less than 0,5.

6.4.2 Irregularity coefficient, i
This coefficient is defined by:
pp−
i = (5)
where

p is the nominal outlet pressure (for acetylene pressure regulators, p = p , see Table 3);

2 2 2i

p is the highest or lowest value of the outlet pressure (see Figure 4) during a test in which the inlet

pressure varies from p to p for a flow equal to the standard discharge, Q .
1 3 1
The limits shall be: −0,3 < i < +0,5.
a) With rising characteristic b) With falling characteristic
Key
p outlet pressure p upstream pressure
o 3
p inlet pressure p stabilized outlet pressure
i 4
p nominal inlet pressure p extreme pressure during i determination
1 5
p nominal outlet pressure
Figure 4 — Typical dynamic expansion curves
© ISO 2010 – All rights reserved 9
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
6.4.3 Operating temperature range

The pressure regulators shall be capable of operating normally in the temperature range −20 °C to +60 °C.

7 Marking
7.1 Pressure regulator

The following information shall be clearly and permanently marked in accordance with 9.5 on the pressure

regulator body or cover or on a label permanently fixed to the pressure regulator:

a) number of this International Standard (ISO 7291:2010);
b) name or trade mark of the manufacturer or distributor;
c) the standard discharge, Q , and nominal outlet pressure, p ;
1 2
d) nominal inlet pressure, p ;

e) the gas intended for use (use the full name of the gas or the symbols shown in Table 5);

f) the designation of the pressure regulator model, if necessary;

g) identification number, if the pressure relief device is supplied as a separate unit;

h) an indication of inlet or an arrow showing the direction of flow.

Table 5 — Recommended code letters for gases to be used for marking of pressure regulators

Gas type Letter code
Air AIR or D
Acetylene A
Carbon dioxide CO2
Coal or town gas C
Ethylene E
Fuel gas or fuel gas mixtures
Hydrogen H
Oxygen O
MPS Y
Natural gas, methane M
Nitrogen, inert gases N
Propane or LPGs P
Propylene L
See Clause 8 for instructions for use.
7.2 Pressure relief devices

Pressure relief devices that are supplied as a separate unit shall be clearly and permanently marked with the

same identification number as the pressure regulator.
10 © ISO 2010 – All rights reserved
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SIST EN ISO 7291:2012
ISO 7291:2010(E)
8 Instructions for use

The manufacturer, supplier or distributor shall supply instructions for use with each pressure regulator,

covering at least:
a) the field of application of the pressure regulator;
b) a description of the pressure regulator and the meaning of the marking;

c) the safe and correct installation of the pressure regulator, including the safe venting of pressure relief

devices, if fitted;

d) the commissioning tests that are necessary to prove safe and correct installation prior to service;

e) the use and maintenance of the pressure regulator (intended for the operator), including hazards and

safety precautions in the case of oxygen.
9 Type test procedure
9.1 General

Checking conformity to this International Standard of a pressure regulator of a given type consists of:

a) tests;
b) checking o
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