ISO 7291:1990
(Main)Welding, cutting and allied processes — Manifold regulators
Welding, cutting and allied processes — Manifold regulators
Soudage, coupage et techniques connexes — Détendeurs des centrales de bouteilles (de gaz industriels)
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Standards Content (Sample)
ISO
INTERNATIONAL
7291
STANDARD
First edition
19904 1-01
Welding, cutting and allied processes -
Manifold regulators
des centrales de
Soudage, coupage et techniques connexes - D6 tendeurs
bou teilles fde gaz indus triels)
Reference number
ISO 7291 : 1990 (E)
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ISO7291 :1990 (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. Esch 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, govern-
mental 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.
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.
International Standard ISO 7291 was prepared by Technical Committee ISO/TC 44,
Welding and alfied processes, Sub-Committee SC 8, Gas welding equipment.
0 ISO 1990
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any
means, electronie or mechanical, including photocopying and microfilm, without Permission in
writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
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INTERNATIONAL STANDARD ISO 7291 : 1990 (E)
Welding, cutting and allied processes -
Manifold regulators
1 Scope 3 Definitions
For the purposes of this International Standard, the following
This International Standard specifies requirements and test
definitions apply.
methods for manifold regulators for welding, cutting and allied
processes.
3.1 manifold regulator: Device for regulating a generally
variable inlet pressure to as constant as possible an outlet
lt is applicable to regulators used to regulate the pressure at the
outlet of high-pressure lines from manifold gas cylinders to pro- pressure, and intended to equip a manifold of cylinders.
vide a feed with compressed gases or dissolved acetylene.
3.2 Pressures
lt is not applicable to regulators fitted directly to the gas
cylinders, as defined in ISO 2503, or to regulators for liquefied
3.2.1 nominal (maximum) inlet pressure, pl: Nominal
gases.
(maximum) upstream pressure for which the manifold regulator
is desig ned .
3.2.2 nominal (maximum) outlet pressure, p2: Nominal
2 Normative references
(maximum) downstream pressure corresponding to the
nominal discharge, Q, , indicated by the manufacturer.
The following Standards contain provisions which, through
reference in this text, constitute provisions of this international
3.2.3 upstream pressure for type testing, p3: The
Standard. At the time of publication, the editions indicated
pressure, in bars l), given by the equation
were valid. All Standards are subject to revision, and Parties to
agreements based on this International Standard are encour-
2p2 + 1 bar (0,l MPa)
P3 =
aged to investigate the possibility of applying the most recent
editions of the Standards indicated below. Members of IEC and
3.2.4 stabilized outlet pressure; Stabilkation pressure,
ISO maintain registers of currently valid International Stan-
p4: The pressure recorded 1 min after discharge ceases, with
dards.
the pressure regulator set to the Standard initial conditions p2,
~31 QI.
ISO 554 : 1976, Standard atmospheres for conditioning and/or
testing - Specifica tions.
3.2.5 highest or lowest outlet pressure,p5: The highest or
lowest value of the outlet pressure during a test in which the
ISO 2503 : 1983, Pressure regula tors for gas c yfin&rs used in
welding, cutting and allied processes. inlet pressure varies from pl to p3 for a flow equal to the
nominal discharge Q, indicated by the manufacturer (see
figure 1).
ISO 5171 : 1980, Pressure gauges used for welding, cutting
and allied processes.
3.3 Flow rates (sec figures 1 and 2)
ISO 9090 : 1989, Gas tightness of equipment for gas welding
and allied processes.
3.3.1 maximum discharge, Qmax: The maximum flow rate
obtained at pressures p3 and p2. At these conditions the
ISO 9539 : 1988, Materials for equipmen t used in gas welding, stabilized outlet pressure p4 shall not exceed the allowable
cutting and allied processes.
value given in 3.4.1.
1) 1 bar = 105Pa
1
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ISO7291:1990(E)
P3 O
‘Pl P3 O
Inlet pressure Inlet pressure
a) with rising characteristic b) with falling characteristic
Figure 1 - Typical dynamic expansion curves
Flow rate
Q
max
Figure 2 - Flow rate characteristics
3.3.2 nominal discharge, QI: The maximum flow rate for 3.4.2 irregularity coefficient, i: The coefficient given by the
the manifold regulator defined by the manufacturer for a par-
equation
ticular gas.
Ps - P2
i =
Q, cannot be less than 0,5 Qmax.
p2
3.4 Coefficients The resulting value shall be in conformity with
-0,3 < i G + 0,5
3.4.1 coefficient of pressure increase upon closure, R:
The coefficient given by the equation
3.4.3 combined coefficient, i + R: The combined coef-
P4 - P2 ficient i + R is given by :
RZ-------
P2
i + R G 0,7
The resulting value shall be in conformity with
The combined coefficient shall be considered when the
regulator does not include a relief valve (see 5.1.2.6).
R < 0,5
2
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ISO 7291 : 1990 (El
shall comply with the requirements specified in 6.5. All com-
4 Units
ponents and accessories shall be thoroughly cleaned and
Pressures specified in this International Standard are gauge
degreased before assembly.
pressures, i.e. pressures exceeding atmospheric pressure. They
are expressed in bars (or in Pascals or multiples thereof).
5.1.2.2 Acetylene manifold regulators
Flow rates are measured in cubic metres per hour, at reference
The nominal (maximum) outlet pressure, ~2, of acetylene
conditions 23 OC and 1,013 bar (0,101 3 MPa).
manifold regulators is a function of the nominal diameter of the
distribution line. These values are specified in the Standards
Temperatures are measured in degrees Celsius.
and regulations applicable in each country.
In any event, the requirements specified in 5.1.2.8 and 6.3.2
5 Design and safety requirements
shall be met.
NOTE - In some countries there may be a legal Obligation for rules,
5.1.2.3 Filters
directives and mandatoty tests concerning Oxygen or acetylene
manifold regulators.
Irrespective of its Position, a filter shall be placed upstream of
the pressure regulator valve. The useful Cross-section shall be
Figure 3 Shows a manifold regulator as an illustration only.
compatible with the average flow rate. The filter shall retain
Optional design characteristics shall not be incompatible with particles > 0,l mm.
the safety requirements specified in this International Standard.
5.1.2.4 Inlet connections
Choice of inlet connections for manifold regu lators is left to the
manufacturer’s discretion.
If cylinder valve connections are used, they shall conform to the
relevant national Standard.
4
2
5.1.2.5 Pressure regulator cover
)
1
t [
The manifold regulator shall be designed and assembled in
such a way that, if the low pressure chamber or the in-
5 termediate chamber (in the case of a two-Stage regulator) is
subjected to direct full cylinder pressure, for example if the
1
regulator valve is jammed in the open Position or if the outlet
Union is closed (for example by a valve or a Seal) high pressure
gas is either contained or is vented safely without ejecting com-
ponent Parts.
Pneumatically controlled regulators, in which the diaphragm is
KeY
held by the pressure of the control gas, shall comply with the
1 Regulator housing
safety requirements.
2 Inlet connection
3 Pressure gauges
4 Relief valve 5.1.2.6 Relief valve
5 Outlet connection
6 Pressure regulator cover
5.1.2.6.1 Location
7 Pressure-adjusting screw
Manifold regulators may be fitted with a relief valve. lt may be
Figure 3 - Manifold regulator
located on the regulator or on the distribution line downstream
‘of the regulator valve.
5.1 Design requirements
The relief valve shall be designed to vent the gas safely verti-
cally up or through a special Pipe, fixed to the outlet orifice of
the relief valve, leading outside.
5.1 .l Materials
5.1.2.6.2 Operation
Materials used for the construction of regulators shaii comply
with the requirements specified in ISO 9539.
The relief valve, if fitted, shall be tight against a pressure
greater than the maximum pressure attained when the flow rate
5.1.2 Design and manufacture
is set for the initial pressure, ~2, plus an overpressure cor-
responding to the real coefficients i and R.
5.1.2.1 Oxygen manifold regulators
When the gas to be vented is at a pressure of 2p2, the flow
rate of the relief valve shall be equal to at least half the nominal
Oxygen manifold regulators shall be so designed, machined
and assembled as to minimize the risk of internal burning and discharge, Q, (2 0,5 Q1,, of the manifold regulator.
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ISO7291 :1990 (EI
During its response, when the pressure falls, the relief valve 5.1.2.9 Outlet connections
shall seal when the downstream pressure is again equal or
slightly superior to the maximum value, p2. Choice of outlet connection is left to the manufacturer’s dis-
cretion.
5.1.2.7 Pressure gauges
Manifold regulators shall be fitted with pressure measuring
5.2 Functional characteristics
devices complying with the functions and safety requirements
specified in ISO 5171. Upstream pressure gauges may form an
integral part of the regulator or they may be fitted to the
5.2.1 Mechanical resistance
manifold.
The pressure chambers of compressed gas and dissolved
Downstream pressure gauges shall be fitted directly to the
acetylene manifold regulators shall withstand at least 1,5 times
regulator or close to the latter without a possibility of shut-off.
the supply pressure or the nominal (maximum) outlet pressure,
with a minimum of 300 bar for the upstream section and a
Gauges fitted downstream shall satisfy the requirements
minimum of 30 bar for the downstream section.
resulting from a possible pressure rise due to the coefficients i
and R.
5.2.2 Gas tightness
5.1.2.8 Pressure-adjusting device
Manifold regulators shall be gas-tight to the exterior, for
This device shall be designed in such a way that it is not
example to the atmosphere, and to the interior, i.e. betvveen
possible for the pressure regulator valve to be held in the open
the high-pressure and low-pressure Parts, at all normal
Position, for example as a consequence of the spring going
pressures for relevant gases but shall not exceed the following
solid.
requirements.
If the dimensions of the pressure-adjusting screw are important
for the safe Operation of the manifold regulator, then the
5.2.2.1 lnternal leakage, Tf
pressure-adjusting screw shall not be removable.
Maximum allowable internal leakage, Tf, of a manifold
The threaded patt of the pressure-adjusting screw of acetylene
regulator is a function of its nominal discharge, Q, (see
manifold regulators shall be restricted, in Order to obtain a
figure 4).
maximum permissible nominal outlet pressure, p2 (see table 1).
Table 1 - Pressures l) For Q, < 30 m3/h, Tf < 50 cm3/h
Tf G 2500 cm3/h
Q, > 1 500 m3/h,
Nominal (maximum)
Gas type outlet pressure, p2
Between these two pairs of values the allowable leakage rate
bar
I
shall satisfy the condition
3,521
Compressed gases, 8
10
Pl = 150 to 200 bar
Tf (cm3/h) > f Q, (m3/h)
20
1) In the special case of acetylene, ~2, p4 and ps shall not exceed
1,5 bar.
5.2.2.2 External leakage
2)
...
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