ISO/DIS 26444.2

Gas cylinders -- Refillable welded aluminium alloy gas cylinders for greater than 60 bar test pressure - Design, construction and testing

Bouteilles à gaz -- Bouteilles à gaz rechargeables en alliage d'aluminium soudées avec une pression d'essai supérieur à 60 bars -- Conception, construction et essais

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD ISO/DIS 26444.2
ISO/TC 58/SC 3 Secretariat: BSI
Voting begins on: Voting terminates on:
2010-02-19 2010-04-19

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Gas cylinders — Refillable welded aluminium alloy gas cylinders
for greater than 60 bar test pressure - Design, construction and
testing

Bouteilles à gaz — Bouteilles à gaz rechargeables en alliage d'aluminium soudées avec une pression d'essai

supérieur à 60 bars — Conception, construction et essais
ICS 23.020.30

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International Organization for Standardization, 2010
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ISO/DIS 26444.2
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ii ISO 2010 – All rights reserved
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ISO/DIS 26444
Contents Page

Foreword .............................................................................................................................................................v

Introduction........................................................................................................................................................vi

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

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

3 Terms, definitions and symbols ..........................................................................................................2

3.1 Terms and definitions ...........................................................................................................................2

3.2 Symbols..................................................................................................................................................2

4 Materials .................................................................................................................................................4

4.1 General provisions................................................................................................................................4

4.2 Heat treatment .......................................................................................................................................4

4.3 Gas/material compatibility....................................................................................................................5

5 Design.....................................................................................................................................................8

5.1 General provisions................................................................................................................................8

5.2 Calculation of wall thickness ...............................................................................................................8

5.3 Design of convex ends (heads and bases).........................................................................................9

5.4 Neck design .........................................................................................................................................14

5.5 Foot-rings.............................................................................................................................................14

5.6 Neck-rings ............................................................................................................................................14

5.7 Shroud ..................................................................................................................................................14

5.8 Design drawing....................................................................................................................................14

6 Construction and workmanship ........................................................................................................14

6.1 Seamless bodies .................................................................................................................................14

6.2 Welding.................................................................................................................................................14

6.3 Non-destructive examination of welds..............................................................................................15

6.4 Surface imperfections.........................................................................................................................15

6.5 Neck threads ........................................................................................................................................16

6.6 Out-of-roundness ................................................................................................................................16

6.7 Straightness.........................................................................................................................................16

6.8 Eccentricity ..........................................................................................................................................16

6.9 Stability.................................................................................................................................................16

7 Tests and examinations......................................................................................................................16

7.1 General .................................................................................................................................................16

7.2 Mechanical tests..................................................................................................................................16

7.3 Hydraulic burst test.............................................................................................................................24

7.4 Pressure cycling test ..........................................................................................................................27

7.5 Hydraulic test.......................................................................................................................................27

7.6 Check on the homogeneity of a batch ..............................................................................................28

7.7 Leakage test.........................................................................................................................................28

7.8 Capacity check ....................................................................................................................................28

7.9 Examination for neck folds ................................................................................................................28

8 Conformity evaluation.........................................................................................................................29

9 Identification marks.............................................................................................................................29

10 Records ................................................................................................................................................29

Annex A (normative) Corrosion tests.............................................................................................................30

A.1 Test for assessing susceptibility to intercrystalline corrosion......................................................30

A.2 Tests for assessing susceptibility to stress corrosion...................................................................40

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ISO/DIS 26444

Annex B (normative) Test method to determine sustained-load-cracking resistance of aluminium

alloy cylinders..................................................................................................................................... 45

B.1 Principle............................................................................................................................................... 45

B.2 General................................................................................................................................................. 45

B.3 Definitions and symbols .................................................................................................................... 45

B.4 Specimen configurations and number of tests ............................................................................... 46

B.5 Fatigue precracking............................................................................................................................ 46

B.6 Specimen testing procedure ............................................................................................................. 46

B.7 Crack growth examination................................................................................................................. 48

B.8 Cylinder thickness qualification........................................................................................................ 48

B.9 Report .................................................................................................................................................. 48

Annex C (normative) New design type testing and production testing.................................................... 51

C.1 New design type testing..................................................................................................................... 51

C.2 Production testing .............................................................................................................................. 52

C.3 Failure to meet test requirements..................................................................................................... 53

Annex D (normative) Description, evaluation of manufacturing imperfections and conditions for

rejection of welded aluminium alloy gas cylinders at time of visual inspection ......................... 55

D.1 Introduction......................................................................................................................................... 55

D.2 General................................................................................................................................................. 55

D.3 Manufacturing imperfections ............................................................................................................ 55

Annex E (informative) Examples of new design type approval and production test certificates .......... 61

E.1 Model new design type approval certificate .................................................................................... 61

E.2 Production testing certificate............................................................................................................ 63

Bibliography..................................................................................................................................................... 67

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ISO/DIS 26444
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 26444 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 3, Gas

cylinders design.
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ISO/DIS 26444
Introduction

The purpose of this International Standard is to provide a specification for the design, manufacture, inspection and

approval of refillable transportable welded aluminium alloy gas cylinders with a test pressure greater than 60 bar.

The specifications given are based on general knowledge of, and experience with, materials, design

requirements, manufacturing processes and control during manufacture, of cylinders.

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ISO/DIS 26444
Gas cylinders — Refillable welded aluminium alloy gas cylinders
for greater than 60 bar test pressure - Design, construction and
testing
1 Scope

This International Standard specifies minimum requirements for the material, design, construction and

workmanship, manufacturing processes and tests at manufacture of refillable transportable welded aluminium alloy

gas cylinders, with a test pressure greater than 60 bar, of water capacities from 0,5 litre up to and including 150 litres

for compressed, liquefied and dissolved gases.

This International Standard includes requirements for spherical receptacles and cylinders made from seamless

bodies with welded non-pressure bearing attachments such as shrouds and foot rings etc.

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 2107:1983, Aluminium, magnesium and their alloys – Temper designations
ISO 6892:1998, Metallic materials – Tensile testing at ambient temperature

ISO 7539-6:1995, Corrosion of metals and alloys – Stress corrosion testing – Part 6: Preparation and use of pre-

cracked specimens

ISO 7866:1999, Gas cylinders – Refillable seamless aluminium alloy gas cylinders – Design, construction and

testing

ISO 9606-2, Qualification test of welders – Fusion welding – Part 2: Aluminium and aluminium alloys

ISO 9956-4:1995, Specification and approval of welding procedures for metallic materials – Part 4: Welding

procedure tests for the arc welding of aluminium and its alloys

ISO 10042:2005, Arc-welded joints in aluminium and its weldable alloys; guidance on quality levels for

imperfections

ISO 11114-1, Transportable gas cylinders – Compatibility of cylinders and valve materials with gas contents – Part

1: Metallic materials

ISO 11116-1, Gas cylinders – 17E taper thread for connection of valves to gas cylinders – Part 1: Specifications

ISO 11116-2, Gas cylinders – 17E taper thread for connection of valves to gas cylinders – Part 2: Inspection

gauges
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ISO/DIS 26444

ISO 11117:1998, Gas cylinders – Valve protection caps and valve guards for industrial and medical gas cylinders –

Design, construction and tests

ISO 11191:1997, Gas cylinders – 25E taper thread for connection of valves to gas cylinders – Inspection gauges

ISO 13341, Transportable gas cylinders – Fitting of valves to gas cylinders
ISO 13769, Gas cylinders – Stamp marking

ISO 17636, Non-destructive testing of welds – Radiographic testing of fusion-welded joints

3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
yield strength

value corresponding to the 0,2 % proof strength (non proportional elongation), R ,

p0 2
3.1.2
solution heat treatment

thermal treatment which consists of heating the products to a suitable temperature, holding at that temperature long

enough to allow constituents to enter into solid solution and cooling rapidly enough to hold the constituents in

solution
3.1.3
quenching

controlled rapid cooling in a suitable medium to retain the solute phase in solid solution

3.1.4
artificial ageing

heat treatment process in which the solute phase is precipitated to give an increased yield stress and tensile

strength
3.1.5
batch

quantity of up to 200 cylinders, plus cylinders for destructive testing, of the same nominal diameter, thickness and

design, made successively from the same cast and subjected to the same heat treatment for the same duration of

time

NOTE The lengths of the cylinders in the heat treatment batch may vary by up to ± 12 %.

3.1.6
design stress factor (F) (variable)

ratio of equivalent wall stress at test pressure (p ) to guaranteed minimum yield strength (Reg)

3.1.7
non-destructive examination

examination or test that does not materially or adversely affect the item being examined

3.2 Symbols
A Percentage elongation after fracture, determined by the tensile test 7.2.3
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ISO/DIS 26444

a Calculated minimum thickness, in millimetres, of the cylindrical or spherical shell

a' Guaranteed minimum thickness, in millimetres, of the cylindrical or spherical shell

b Guaranteed minimum thickness, in millimetres, at the centre of a convex base

D Nominal outside diameter, in millimetres, of the cylinder, spherical cylinder or domed end (see Figure 2)

D Nominal inside diameter, in millimetres, of the cylinder, spherical cylinder or domed end (see Figure 2)

d Diameter of former, in millimetres (see Figure 4)
F Design stress factor (variable) (see 3.1.6)

h Internal height, in millimetres, of semi-ellipsoidal or torispherical domed end (convex head or base end) (see

Figure 2)
h Variable used in the determination of shape factor, K (see 5.3.1)

h External height, in millimetres, of a semi-ellipsoidal or torispherical domed end (convex head or base end) (see

Figure 2 and note below)

K Shape factor for a semi-ellipsoidal or torispherical domed end, obtained according to the values h /D and

e o
a/D , with interpolation where necessary, (see Figure 1)
L Original gauge length, in millimetres, according to ISO 6892

n The ratio of the diameter of the bend test former to actual thickness of test piece (t)

p Measured burst pressure, in bar above atmospheric pressure
p Hydraulic test pressure, in bar above atmospheric pressure
p Lower cyclic pressure, in bar above atmospheric pressure

p Observed yield pressure which produces a permanent volumetric expansion of 0,2 %, in bar above

atmospheric pressure

R Minimum guaranteed value of the yield strength (see 3.1.1), in MPa, for the finished cylinder

R Actual value of theyield strength, in MPa, as determined by the tensile test specified in 7.2.3 for the finished

cylinder

R Minimum guaranteed value of the tensile strength, in MPa, for the finished cylinder

R Actual value of the tensile strength, in MPa, as determined by the tensile test specified in 7.2.3 for the finished

cylinder
r Internal knuckle radius, in millimetres, of torispherical end (see Figure 2c))
) 5 5 2
1 bar = 10 Pa = 10 N/m
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ISO/DIS 26444

r′ Internal radius, in millimetres, of dishing of torispherical end (see Figure 2c))

r External knuckle radius, in millimetres, of torispherical end (see Figure 2c))

r′ External radius, in millimetres, of dishing of torispherical end (see Figure 2c))

s Straight flange length, in millimetres, for semi-ellipsoidal and torispherical domed ends (see Figure 2b)) and

2c))

S Original cross-sectional area of tensile test piece, in square millimetres, according to ISO 6892

t Actual thickness of test specimen, in millimetres
t Calculated minimum thickness, in millimetres, of a domed end
w Width, in millimetres, of tensile test piece

V Volumetric expansion attained at burst, expressed as a percentage of the initial volume (see 7.3)

exp
Z Stress reduction factor (see 5.2.1)
4 Materials
4.1 General provisions

4.1.1 Aluminium alloys may be used to produce gas cylinders provided that they satisfy the requirements of the

corrosion resistance tests described in Annex A, and meet all other requirements of this International Standard,

including Annex B.

4.1.2 Examples of the alloys most commonly used for the fabrication of gas cylinders are those given in Table 1.

4.1.3 After the completion of all welding (including that of the attachments) and before the hydraulic test each

cylinder shall be heat treated if required to meet the design criteria.
4.2 Heat treatment
4.2.1 General

Any welding on the pressure bearing part shall take place before any final heat treatment (see 6.2).

4.2.2 Heat treatable alloys

The manufacturer shall specify on the prototype testing documentation, where required, the solution heat treatment

and artificial ageing temperatures and the times for which the cylinders have been held at those temperatures. The

medium used for quenching after solution heat treatment shall be identified.

Unless the alloy is subjected to a temperature in excess of 400 °C during the forming process, a stabilizing

treatment shall be carried out and the temperature and the time at temperature, shall be identified by the

manufacturer.

However, the stabilizing treatment is not necessary for a cylinder of which the wall thickness in 5.2 is calculated

with the minimum guaranteed yield strength value of the O-tempered alloy (or the alloy annealed for complete re-

crystallization before forming of cylinder, as defined in ISO 2107: 1983).
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ISO/DIS 26444

If the cylinder is intended for dissolved gas service it shall only be used in the fully annealed condition, i.e. the

minimum guaranteed properties used for the material shall consider the heat treatment to be applied, e.g. during

the massing operation.
4.2.3 Non-heat treatable alloys

The manufacturer shall specify on the prototype testing documentation, where required, the type of metal forming

operation carried out (extrusion, drawing, ironing, head forming, etc.) Unless the alloy is subjected to a temperature

in excess of 400 °C during the forming process, a stabilizing treatment shall be carried out and the temperature,

and time at temperature, shall be identified by the manufacturer.
4.2.4 Control of specified heat treatment

During the heat treatment, the manufacturer shall comply with the specified temperatures and durations, within the

following ranges:
a) Temperatures
Solution temperature : maximum range 20 °C
Artificial ageing temperature : maximum range 20 °C
Stabilizing temperature : maximum range 20 °C
b) Durations
Time cylinders actually spend at temperature during treatments:
All treatments : maximum range 20 %
4.3 Gas/material compatibility
Gas/material compatibility shall be verified as specified in ISO 11114-1.
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ISO/DIS 26444
Table 1 — Chemical composition of aluminium alloys
Type of Type
Chemical composition - weight %
alloy AA
2), 3)
registered
Si Fe Cu Mn Mg Cr Zn Ti Pb Bi Others Aluminium
Each Total
designation
2,2 0,15
min.
- - - - - - Remainder
5052 A - - - -
0,25 0,40 0,10 0,10 2,8 0,35 0,10 - 0,05 0,15
max. - -
3,1 0,15
min. - - - - - - Remainder
5154 A - - - -
0,25 0,40 0,10 0,10 3,9 0,35 0,20 0,20 0,05 0,15
max. - -
0,40 4,0 0,05
min.
- - - - - - Remainder
5083A D - - -
0,40 0,40 0,10 1,0 4,9 0,25 0,25 0,15 0,05 0,15
max. - -
min.
- - - - - - Remainder
6061A D 0,40 - 0,15 - 0,8 0,04
max. 0,0030 0,0030
0,8 0,7 0,40 0,15 1,2 0,35 0,25 0,15 0,05 0,15

1) AA is the Aluminum Association Inc., 900 19th Street N.W., Washington D.C., 20006-2168, USA.

2) Type A and Type B may be used for the body and Type C for the non pressure bearing part.

3) Type D may be used for the body and the non pressure bearing part.
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ISO/DIS 26444
Table 1 — Chemical composition of aluminium alloys (cont.)
Type of Type
Chemica composition - weight %
alloy AA
2), 3)
registered
Si Fe Cu Mn Mg Cr Zn Ti Pb Bi Others Aluminium
Each Total
designation
min
6063 C 0,2 - - - 0,4 - - - - - - - Remainder
max
0,7 0,5 0,1 0,3 0,9 0,1 0,2 0,2 0,0030 - 0,05 0,15
min
6082 D 0,7 - - 0,40 0,60 - - - - - - - Remainder
max
1,3 0,50 0,10 1,0 1,2 0,25 0,20 0,10 0,0030 0,0030 0,05 0,15
min
6082 B 1,2 - - 0,8 1,0 - - - - - - - Remainder
max
1,6 0,5 0,1 1,0 1,4 0,1 0,2 0,2 0,0030 0,0030 0,05 0,15

1) AA is the Aluminum Association Inc., 900 19th Street N.W., Washington D.C., 20006-2168, USA.

2) Type A and Type B may be used for the body and Type C for the non pressure bearing part.

3) Type D may be used for the body and the non pressure bearing part.
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ISO/DIS 26444
5 Design
5.1 General provisions

5.1.1 The calculation of the wall thickness of the pressure-bearing parts shall be related to the yield strength

(R ) of the material to ensure elastic behaviour.

5.1.2 For calculation purposes the value of the yield strength (R ) is limited to a maximum of 0,9 R for

eg mg
aluminium alloys.

5.1.3 The internal pressure upon which the calculation of wall thickness is based shall be the hydraulic test

pressure (p ).

5.1.4 For dissolved gases, the manufacturing process of the porous mass can modify the characteristics of the

aluminium alloy used. This shall be considered when designing the
...