Tiêu chuẩn iso 07866 2012

Reference number ISO 7866 2012(E) © ISO 2012 INTERNATIONAL STANDARD ISO 7866 Second edition 2012 09 01 Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and test[.]

Reference number ISO 7866:2012(E)

Second edition 2012-09-01

Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and testing

Bouteilles à gaz — Bouteilles à gaz sans soudure en alliage d'aluminium destinées à être rechargées — Conception, construction et essais

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Contents Page

Foreword v 

Introduction vi 

1 Scope 1 

2 Normative references 1 

3 Terms and definitions 1 

4 Symbols 2 

5 Inspection and testing 4 

6 Materials 4 

6.1 General requirements 4 

6.2 Thermal treatments 5 

6.3 Test requirements 6 

6.4 Failure to meet test requirements 6 

7 Design 7 

7.1 General requirements 7 

7.2 Calculation of cylindrical shell thickness 7 

7.3 Design of ends (heads and bases) 7 

7.4 Neck design 8 

7.5 Foot rings 11 

7.6 Neck rings 11 

7.7 Design drawing 11 

7.8 High-strength and/or low-elongation gas cylinder designs 11 

8 Construction and workmanship 11 

8.1 General 11 

8.2 End forming 11 

8.3 Wall thickness 12 

8.4 Surface imperfections and defects 12 

8.5 Neck threads 12 

8.6 Out-of-roundness 12 

8.7 Exposure to heat 13 

8.8 Straightness 13 

8.9 Mean diameter 13 

9 Type approval procedure 13 

9.1 General requirements 13 

9.2 Prototype tests 14 

9.3 Type approval certificate 15 

10 Batch tests 15 

10.1 General requirements 15 

10.2 Tensile test 17 

10.3 Bend test and flattening test 18 

10.4 Hydraulic burst test 19 

10.5 Test requirements for high-strength and/or low-elongation gas cylinder designs 21 

11 Gas cylinder tests and examinations 22 

11.1 General 22 

11.2 Hydraulic test 22 

11.3 Hardness test 23 

11.4 Leakage testing 23 

11.5 Examination for neck folds 23 

11.6 Marking verification 23 

11.7 Aluminium alloy gas cylinder surface features at time of manufacture 23 

12 Certification 24 

13 Marking 25 

Annex A (normative) Corrosion tests 26 

Annex B (normative) Test method to determine the sustained-load cracking resistance of aluminium alloy gas cylinders 36 

Annex C (informative) Typical type approval certificate 43 

Annex D (informative) Acceptance certificate 44 

Annex E (normative) Specific requirements for gas cylinders made of high-strength and/or low-elongation aluminium alloy 46 

Annex F (informative) Description and evaluation of manufacturing surface imperfections and conditions for rejection of seamless aluminium alloy gas cylinders at time of product acceptance 52 

Annex G (normative) Batch size 59 

Annex H (normative) Specific provisions for acetylene cylinder shells 60 

Bibliography 61 

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 7866 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 3, and by Technical Committee CEN/TC 23, Transportable gas cylinders in collaboration

This second edition cancels and replaces the first edition (ISO 7866:1999), which has been technically revised

The following significant technical changes have been carried out:

 a new subclause (11.7) has been added to address unacceptable manufacturing defects and unacceptable surface features at the time of manufacture and changes have been made to other

subclauses to compliment the new subclause;

 terms and definitions and the symbols have been revised;

 terminology changes included: “stress” changed to “strength”;

 various editorial errors were corrected;

 equipment calibration requirements were added;

 defining "defect" as a feature caused by the manufacturing/manufacturer; and

 defining "imperfection" as damage or feature not caused by manufacturing/manufacturer

Introduction

The purpose of this International Standard is to provide a specification for the design, manufacture, inspection and testing of a seamless aluminium alloy gas cylinder for worldwide usage The objective is to balance design and economic efficiency against international acceptance and universal utility

This International Standard aims to eliminate the concern about climate, duplicate inspections and restrictions currently existing because of lack of definitive International Standards This International Standard should not

be construed as reflecting on the suitability of the practice of any nation or region

Following publication, this International Standard will be submitted for reference in the UN Recommendations

on the Transport of Dangerous Goods – Model Regulations

Gas cylinders — Refillable seamless aluminium alloy gas

cylinders — Design, construction and testing

1 Scope

This International Standard specifies minimum requirements for the material, design, construction and workmanship, manufacturing processes and tests at time of manufacture of refillable seamless aluminium alloy gas cylinders of water capacities up to and including 150 litres for compressed, liquefied and dissolved gases for worldwide use (normally up to 65 °C)

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 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method

ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method (scales A, B, C, D, E, F, G,

H, K, N, T)

ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

ISO 7438, Metallic materials — Bend test

ISO 7539-6:2011, Corrosion of metals and alloys — Stress corrosion testing — Part 6: Preparation and use of

pre-cracked specimens for tests under constant load or constant displacement

ISO 10461, Gas cylinders — Seamless aluminium-alloy gas cylinders — Periodic inspection and testing ISO 11117, Gas cylinders — Valve protection caps and valve guards — Design, construction and tests

ISO 13341, Gas cylinders — Fitting of valves to gas cylinders

ISO 13769, Gas cylinders — Stamp marking

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply

NOTE See Table G.1 for batch size requirements

mass of a gas cylinder

combined mass of the gas cylinder and all permanently attached parts (e.g foot ring, neck ring), but without the valve

NOTE Mass is expressed in kilograms

3.7

quenching

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

3.8

solution heat treatment

thermal treatment which consists of heating products to a suitable temperature and holding them at that temperature long enough to allow constituents to enter into solid solution

3.9

stabilizing heat treatment

non-ageing heat treatment applied to 5 000-series aluminium alloys in order to minimize changes in mechanical properties and structure under service conditions

a calculated minimum wall thickness, in millimetres, of the cylindrical shell (see Figure 1)

a′ guaranteed minimum wall thickness, in millimetres, of the cylindrical shell

A percentage elongation after fracture

b guaranteed minimum thickness, in millimetres, at the centre of a convex base (see Figure 1)

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

d’ positive circular development of fracture

d’’ negative circular development of fracture

D nominal outside diameter, in millimetres, of the cylinder (see Figure 1 and Figure 2)

D1 nominal outside diameter, in millimeters, of the cylinder neck (see Figure 2)”

Df diameter, in millimetres, of the bend test former (see Figure 5)

E modulus of elasticity

F design stress factor (variable) (see 3.4)

H outside height, in millimetres, of the domed part (convex head or base end) (see Figure 1)

L′ length of short branch of fracture, in millimeters

L′′ length of long branch of fracture, in millimeters

Lo original gauge length, in millimetres, as defined in ISO 6892-1 (see Figure 4)

n ratio of the diameter of the bend test former to the actual thickness of the test specimen, t

pb actual burst pressure, in bars above atmospheric pressure

pf failure pressure, in bars

ph hydraulic test pressure, in bars above atmospheric pressure

pu upper cycling pressure, in bars

py observed pressure when gas cylinder starts yielding during hydraulic bursting test, in bars above

atmospheric pressure

r inside knuckle radius, in millimetres (see Figure 1)

rc tip radius, in millimeters

ri inside crown radius, in millimetres (see Figure 1)

R maximum stress value, in MPa

Rea actual value of the yield strength, in megapascals, as determined by the tensile test specified in 10.2

for the finished gas cylinder

Reg minimum guaranteed value of the yield strength (see 3.10), in megapascals, for the finished gas

cylinder

Rma actual value of the tensile strength, in megapascals, as determined by the tensile test specified in

10.2 for the finished gas cylinder

Rmg minimum guaranteed value of the tensile strength, in megapascals, for the finished gas cylinder

Rp0,2 0,2 % proof strength (0,2% non-proportional elongation), for aluminium alloys

So original cross-sectional area, in square millimetres, of the tensile test specimen in accordance with

ISO 6892-1

t actual wall thickness, in millimetres, of the test specimen

tm average cylinder wall thickness, in millimetres, in the position of testing during the flattening test

T titre of hydrogen peroxide in g per litre

u ratio of distance between knife edges at the end of test to the average cylinder wall thickness

w width, in millimetres, of the narrow, parallel-sided section of a tensile test specimen (see Figure 4)

z correction factor

5 Inspection and testing

NOTE Evaluation of conformity can be performed in accordance with the regulations recognized by the country(ies) where the gas cylinders are intended to be used

To ensure that the gas cylinders conform to this International Standard, they shall be subjected to inspection and testing in accordance with Clauses 9, 10 and 11 by an inspection body, hereafter referred to as the

“Inspection Body”, authorized to do so

Equipment used for measurement, testing and examination during production shall be maintained and calibrated within a documented quality managment system

6 Materials

6.1 General requirements

6.1.1 Aluminium alloys and their chemical composition limits shall be as specified in Table 1 Other

aluminium alloys may be used to produce gas cylinders provided they satisfy all the requirements of this International Standard and are approved by the relevant authority for cylinder use

6.1.2 The gas cylinder manufacturer shall identify the gas cylinders with the particular casts of the alloy

from which they are made, and shall obtain and provide certificates of the analysis of the casts used If check analysis is required, they shall be carried out either on test specimens taken from material in the form supplied

by the producer of the aluminium alloy or from finished gas cylinders

6.1.3 Some aluminium alloys are not compatible with certain gases and gas mixtures, e.g corrosive gases

(see ISO 11114-1) The manufacturer shall use materials compatible with the intended gas service when the purchaser indicates the intended gas

Table 1 — Chemical composition of materials

min 0,40 — 0,15 — 0,8 0,04 — — — — — — —

Remainder max 0,8 0,7 0,40 0,15 1,2 0,35 — 0,25 0,15 — 0,003 0 0,05 0,15

NOTE The above materials are used extensively throughout the world in preference to the alloy compositions quoted in ISO 209 They are included in this International Standard quoting the IAA registered designations, but making reference to ISO 209 where it is considered applicable

6.2 Thermal treatments

6.2.1 Heat-treatable alloys (see Table 1, groups 1, 3 and 4)

The manufacturer shall specify, in the type approval documentation, the solution heat treatment and ageing temperatures and the minimum times for which the gas cylinders have been held at those temperatures The medium used for quenching after solution heat treatment shall be identified

artificial-6.2.2 Non-heat-treatable alloys (see Table 1, group 2)

The manufacturer shall specify, in the type approval documentation, 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 heat treatment shall be carried out at a temperature above 220 °C, and the temperature and time at that temperature shall be identified by the manufacturer

6.2.3 Control of specified heat treatment

During the heat treatment, the manufacturer shall comply with the following tolerances:

a) temperatures:

 solution temperature 10 °C,

 artificial ageing temperature 5 °C,

 stabilizing temperature 10 °C;

b) time gas cylinders actually spend at this temperature during treatment:

 solution treatment 30 %,

 ageing treatment 20 %,

 stabilizing treatment 10 %

6.3 Test requirements

The material of the finished gas cylinders shall conform to Clauses 9, 10 and 11

6.4 Failure to meet test requirements

6.4.1 In the event of failure to meet test requirements, retesting or reheat treatment and retesting shall be

carried out as follows:

a) If there is evidence of a fault in carrying out a test, or an error of measurement, a second test shall be performed, on the same gas cylinder if possible If the result of this test is satisfactory, the first test shall

6.4.2 Two further gas cylinders selected at random from the same batch shall be subjected to the tests

specified in 10.1.3 a) and 10.1.3 b) If both gas cylinders meet the specified requirements, the batch shall be accepted Should either gas cylinder fail to meet the specified requirements, the batch shall

a) be rejected,

or

b) be treated in accordance with 6.4.3

6.4.3 The batch of gas cylinders shall be reheat-treated and two further gas cylinders shall be tested in

accordance with 10.1.3 a) and 10.1.3 b) If both gas cylinders meet the specified requirements, the batch shall

be accepted Should either gas cylinder fail to meet the specified requirements, the batch shall be rejected

6.4.4 For heat-treatable alloys, where it can be established that the heat treatment was at fault for failure of

a test, the batch of gas cylinders may additionally (more than once) be re-solution heat-treated and/or aged However, the batch may only be submitted to the Inspection Body one more time for testing after the initial submission If the batch presented to the Inspection Body for the second test or tests fails one or more tests, the batch shall be condemned

7 Design

7.1 General requirements

7.1.1 The calculation of the wall thickness of the pressure-containing parts shall be related to the yield

strength, Reg, of the material

7.1.2 For calculation purposes, the value of the yield strength, Reg, is limited to a maximum of 0,90Rmg for seamless aluminium alloy gas cylinders

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

pressure, ph

7.1.4 Wherever any exposure to heat is necessary (e.g for gas cylinders for dissolved acetylene, where the

process by which the porous material is manufactured can modify the characteristics of the aluminium alloy used; see Annex H), this shall be considered when designing the shell

7.2 Calculation of cylindrical shell thickness

The guaranteed minimum thickness of the cylindrical shell, a′, shall not be less than the thickness calculated

using relationships (1) and (2), and additionally condition (3) shall be satisfied:

Reg/Rmg shall not exceed 0,90

The wall thickness shall also satisfy the relationship:

1 mm

100

D

with an absolute minimum of 1,5 mm

The burst ratio shall be satisfied by test The following condition shall be met:

When choosing the minimum guaranteed value of the thickness of the cylindrical shell, a′, the manufacturer

shall ensure that the thickness is sufficient to satisfy both the calculations and the required verification testing NOTE It is generally assumed that ph  1,5  the service pressure for compressed gases for gas cylinders designed and manufactured to this International Standard

7.3 Design of ends (heads and bases)

7.3.1 The thickness and shape of the base and head of the gas cylinders shall be such as to meet the requirements of the tests specified in 10.4 (hydraulic burst test) and 9.2.3 (pressure-cycling test)

To achieve satisfactory stress distribution, the gas cylinder wall thickness shall increase progressively in the transition zone between the cylindrical shell and the ends, particularly the base Examples of typical shapes of convex heads and base ends are shown in Figure 1

7.3.2 The thickness at any part of a convex end shall be not less than the minimum wall thickness of the cylindrical part

7.3.3 The inside crown radius, ri, shall be not greater than 1,2  the inside diameter of the shell, and the

knuckle radius, r, shall be not less than 10 % of the inside diameter of the shell

7.3.4 Where the conditions of 7.3.3 are not fulfilled, the gas cylinder manufacturer shall prove by the prototype tests as required in 9.2 that the design is satisfactory

7.4 Neck design

7.4.1 The external diameter and thickness of the formed neck end of the gas cylinder shall be adequate for the stresses resulting from the fitting of the valve to the gas cylinder The stresses can vary according to the thread diameter, its form and the sealant used in fitting the valve The requirements specified in ISO 13341 (or

as recommended by the manufacturer where that International Standard does not apply) shall be applied, since permanent damage to the gas cylinder could otherwise result

7.4.2 In establishing the minimum thickness, consideration shall be given to obtaining a thickness of the wall in the gas cylinder neck which will prevent permanent expansion of the neck during the initial and subsequent fittings of the valve into the gas cylinder

In specific cases (e.g very thin walled cylinders), where the stresses resulting from the initial and subsequent fittings of the valve to the gas cylinder cannot be supported by the neck itself, the neck may be designed to require reinforcement, such as a neck ring or shrunk-on collar, provided the reinforcement material and dimensions are clearly specified by the manufacturer and this configuration is part of the type approval procedure

7.4.3 Gas cylinders may be designed with one or two openings but both shall be along the central gas cylinder axis

Figure 1 — Typical ends

Figure 1 — Typical ends (continued)

7.5 Foot rings

When a foot ring is provided, it shall be sufficiently strong and made of material compatible with that of the gas cylinder The shape should preferably be cylindrical and shall give the gas cylinder sufficient stability The foot ring shall be secured to the gas cylinder by a method other than welding, brazing or soldering To prevent ingress of water, any gaps which could form water traps shall be sealed by a method other than welding, brazing or soldering

Where the gas cylinder manufacturer fits valve protection, it shall be in accordance with the requirements specified in ISO 11117

7.7 Design drawing

A fully dimensioned drawing, including tolerances, shall be prepared which includes the specification of the material and makes reference to this International Standard

7.8 High-strength and/or low-elongation gas cylinder designs

Requirements for these designs are given in Annex E

8 Construction and workmanship

8.1 General

The gas cylinder shall be produced by

a) cold or hot extrusion from cast or extruded or rolled billet,

b) cold or hot extrusion from cast or extruded or rolled billet, followed by cold drawing,

c) cupping, flow forming, spinning and cold drawing sheet or plate,

d) open necking at both ends of an extruded or cold-drawn tube (see Figure 2), and

be used irrespective of the method employed for the manufacture of the shell

The end-forming operation chosen shall result in a visibly smooth surface, especially in the neck/shoulder areas, which has no feature or defect [e.g unacceptable folds (see 11.5) or cracks] which will adversely affect the performance or integrity of the gas cylinder

Figure 2 — Necked ends of tube

8.3 Wall thickness

Each gas cylinder shall be examined, at the time of production, for thickness The wall thickness at any point shall be not less than the minimum thickness specified

8.4 Surface imperfections and defects

Each gas cylinder shall be examined, at the time of production, for internal and external surface imperfections and defects

The internal and external surfaces of the finished gas cylinder shall be free from defects that would adversely affect the safe working of the gas cylinder

Such defects shall be removed by local dressing (where permitted) or the cylinder shall be condemned The wall thickness of any dressed areas shall not be less than the minimum thickness specified in the design Imperfections are subject to the requirements of 11.7

8.6 Out-of-roundness

The out-of-roundness of the cylindrical shell, i.e the difference between the maximum and minimum outside diameters in the same cross-section, shall not exceed 2 % of the mean of these diameters

8.7 Exposure to heat

Any exposure to heat after the heat treatment or stabilization treatment shall not modify the characteristics of the aluminium alloy used to the extent that the mechanical properties fall below the minimum guaranteed values When exposure to heat is necessary (see 7.1.4), extensive trials shall be performed to verify that the minimum design criteria are always met

A gas cylinder shall be considered to be of a new design compared with an existing approved design when a) it is manufactured in a different factory; or

b) it is manufactured by a different process (see 8.1) [this includes the case when major process changes (e.g a change in the neck-forming method) are made during the production period]; or

c) it is manufactured from an alloy of different composition limits from that used in the original prototype tests; or

d) it is given a different heat treatment that is outside the temperature and time ranges specified in 6.2.3; or e) the base profile and the base thickness have changed relative to the gas cylinder diameter and calculated minimum wall thickness; or

f) the overall length of the gas cylinder has increased by more than 50 % (gas cylinders with a length/diameter ratio less than 3 shall not be used as reference gas cylinders for any new design with this ratio greater than 3); or

g) the nominal outside diameter has changed; or

h) the design wall thickness has changed; or

i) the hydraulic test pressure has been increased (where a gas cylinder is to be used for lower-pressure duty than that for which design approval has been given, it shall not be deemed to be a new design); or j) the guaranteed minimum yield strength, Reg, and/or the guaranteed minimum tensile strength, Rmg, have changed

9.2 Prototype tests

9.2.1 General

A minimum of 50 gas cylinders, which are guaranteed by the manufacturer to be representative of the new design, heat treated to no more than the minimum times 10 % required in 6.2, shall be made available for prototype testing If the gas cylinders are likely to experience exposure to heat in further processing (e.g curing of porous material for acetylene service or heating for powder painting) (see 8.7), testing shall be carried out on representative gas cylinders However, if the total number of gas cylinders required is less than

50, enough gas cylinders shall be made to complete the prototype tests required, in addition to the production quantity, but in this case the approval validity is limited to this particular production batch

9.2.2 Inspection

In the course of the type approval process, the Inspection Body shall select the necessary gas cylinders for testing and then proceed as follows:

a) The Inspection Body shall verify that

 the materials conform to Clause 6;

 the design conforms to Clause 7;

 the thicknesses of the walls and ends on two of the gas cylinders taken for testing conform to 7.2, 7.3 and 7.4, the measurements being taken on three transverse sections of the cylindrical part and over the whole of a longitudinal section of the base and the head;

 the requirements of 7.5, 7.6 and 8.2 to 8.9 inclusive are met for all gas cylinders selected by the Inspection Body;

 the material meets the requirements of the intercrystalline and stress corrosion tests specified in Annex A [it is not necessary to carry out these tests when only condition 9.1 e) applies and/or when the nominal outside diameter has changed by less than 20 %];

 the sustained-load cracking test has been completed satisfactorily in accordance with Annex B NOTE This is a “material” qualification test (see Clause B.2) and not a prototype test

b) The Inspection Body shall then supervise the following tests on the gas cylinders selected:

 the tests specified in 10.1.3 a) (mechanical testing), but on two gas cylinders, the test specimens being identifiable with the batch;

 the tests specified in 10.1.3 b) (hydraulic burst test), but on two gas cylinders, the gas cylinders bearing representative markings;

 the tests specified in 9.2.3 (pressure-cycling test) on three gas cylinders, the gas cylinders bearing representative markings

9.2.3 Pressure-cycling test

This test shall be carried out with a non-corrosive liquid, subjecting the gas cylinders to successive reversals

at an upper cyclic pressure which is equal to the hydraulic test pressure, ph The gas cylinders shall withstand

12 000 cycles without failure

For gas cylinders with a hydraulic test pressure, ph,  450 bar, the upper cyclic pressure may be reduced to two-thirds of the test pressure In this case, the gas cylinders shall withstand 80 000 cycles without failure

The value of the lower cyclic pressure shall not exceed 10 % of the upper cyclic pressure, but with an absolute maximum of 30 bar

The gas cylinder shall actually experience the maximum and minimum cyclic pressures during the test

The frequency of reversals of pressure shall not exceed 0,25 Hz (15 cycles/min) The temperature measured

on the outside surface of the gas cylinder shall not exceed 50 °C during the test

After the test, the gas cylinder bases shall be sectioned in order to measure the thickness and to ensure that this thickness is sufficiently close, within the usual production tolerances, to the minimum thickness prescribed

in the design In no case shall the actual base thickness exceed that specified in the drawing by more than

15 %

The test shall be considered satisfactory if the gas cylinder attains the required number of cycles without developing a leak

9.2.4 Test requirements for high-strength and/or low-elongation gas cylinder designs

High-strength and/or low-elongation gas cylinder designs shall be subject to the requirements of Annex E

9.3 Type approval certificate

If the results of the prototype tests in accordance with 9.2 are satisfactory, the Inspection Body shall issue (if authorized by the regulatory authority), or recommend that the regulatory authority issue, a type approval certificate, a typical example of which is given in Annex C

10 Batch tests

10.1 General requirements

10.1.1 All tests for checking the quality of the gas cylinder shall be carried out on material from finished gas cylinders Gas cylinders for mechanical and burst testing need not have been pressure-tested

For the purpose of batch testing, the manufacturer shall provide the Inspection Body with

 the type approval certificate,

 certificates stating the cast analyses of the alloy supplied for the construction of the gas cylinders,

 a means of identifying the cast of the material from which each gas cylinder was made,

 a statement of the manufacturing processes utilized as specified in 8.1 and 8.2 and the relevant documentation relating to the heat and mechanical treatment,

 a list of the gas cylinders, stating serial numbers and stamp markings, as required,

 confirmation that threads conform to the approved manufacturer′s drawing [the gauges to be used shall

be specified (e.g using ISO 11363-2)], and

 verification that the water capacity conforms to the design drawing

10.1.2 During batch testing, the Inspection Body shall select the gas cylinders necessary for testing and then proceed as follows:

 The Inspection Body shall ascertain that the type approval certificate has been obtained and that the gas cylinders conform to it

 The Inspection Body shall then check that the markings are in accordance with the design specification

 The Inspection Body shall also check whether the requirements set out in Clauses 6, 7 and 8 have been met and, in particular, check by an external and, if physically possible, internal visual inspection of the gas cylinders whether their construction and the checks carried out by the manufacturer in accordance with 7.5, 7.6, 8.2 to 8.6, 8.8 and 8.9 are satisfactory This visual examination shall cover at least 10 % of the gas cylinders submitted Should an internal unaided visual examination be physically impossible, an alternative inspection method shall be agreed between the manufacturer and the Inspection Body At least 10 % of the batch shall be checked by this method

However, if a gas cylinder not meeting the above requirements is found, then all of the gas cylinders shall

be inspected

 The Inspection Body shall witness the tests and verify that the results of the tests specified in 10.1.3 a) (mechanical testing) and 10.1.3 b) (hydraulic burst testing) are satisfactory Where alternative tests are permitted, the purchaser and manufacturer shall agree which tests are to be carried out

 The Inspection Body shall check whether the information supplied by the manufacturer referred to in 10.1.1 is correct (random checks shall be carried out);

 Finally, the Inspection Body shall assess the results of the hardness testing specified in 11.3

10.1.3 The following tests shall be carried out on each batch of gas cylinders:

a) On one gas cylinder:

1) one tensile test in the longitudinal direction (see 10.2);

2) two bend tests in a circumferential direction (see 10.3.1) or a flattening test (see 10.3.2)

The location of the test specimens shall be in accordance with Figure 3

b) On a second gas cylinder:

1) one hydraulic burst test (see 10.4)

Key

1 bend test specimens

2 tensile test specimen

Figure 3 — Location of test specimens

10.2.2 With regard to the heat-treatable alloys referred to in Table 1, the percentage elongation after fracture,

A, shall be not less than 12 %, except for AA 2001 which is covered in Annex E

With regard to the non-heat-treatable alloys referred to in Table 1, the elongation after fracture shall not be less than 12 % when the test is carried out on a single test specimen taken from the gas cylinder wall The tensile test may also be carried out on four test specimens distributed uniformly throughout the gas cylinder wall The results shall be as follows:

 no individual value may be less than 11,0 %;

 the average of the results from all the test specimens shall be at least 12,0 %

Dimensions in millimetres

Test specimen dimensions when t  3 mm:

w  4t

w  D/8

Figure 4 — Tensile test specimen

10.3 Bend test and flattening test

10.3.1 Bend test

10.3.1.1 The bend test shall be carried out in accordance with ISO 7438 on two test specimens obtained

by cutting either one or two rings of width 25 mm or 3t, whichever is the greater, into four equal parts The two

test specimens shall be taken from the parts that were 180° apart Each test specimen shall be of sufficient length to permit the bend test to be carried out correctly Only the edges of each strip may be machined

10.3.1.2 The test specimen shall not crack when bent inwards around the former until the inside surfaces are not further apart than the diameter of the former (see Figure 5)

10.3.1.3 The diameter of the former, Df, shall be established, using the value of n given in Table 2 for the relevant actual tensile strength (Rma) range, from the formula:

Df  n  t

where t is test specimen thickness

Table 2 — Bend test and flattening-test requirements Actual tensile strength,

MPa

Value of n for bend test

and flattening test

a Distance between knife edges at end of test  u  tm, where tm is the average gas cylinder wall

thickness at the position of test

a calculated minimum thickness

Figure 5 — Illustration of bend test

10.3.2 Flattening test

10.3.2.1 The flattening test shall be performed on one gas cylinder selected from each batch after heat treatment

10.3.2.2 The test gas cylinder shall be flattened between wedge-shaped knife edges with a 60° included

angle The maximum radius of the knife edges shall be established, using the value of n given in Table 2 for the relevant actual tensile strength (Rma) range, from the formula:

Maximum radius  n  tm

where tm is the average gas cylinder wall thickness at the position of test

The length of the knife edges shall not be less than the width of the flattened gas cylinder The longitudinal axis of the gas cylinder shall be at approximately 90° to the knife edges

10.3.2.3 The test gas cylinder shall be flattened until the distance between the knife edges is in accordance with Table 2 The flattened gas cylinder shall remain visually uncracked

10.4 Hydraulic burst test

Key

1 test fluid reservoir

2 tank for measurement of test fluid (the feed tank may also be used as a measuring tank)

3 pump

4 pressure gauge

5 pressure/volumetric expansion curve recorder

6 vent or air release valve

During the test, pressurization shall be carried out in two successive stages:

a) In the first stage, the pressure shall be increased at a rate of not more than 5 bar/s up to a pressure value corresponding to the initiation of plastic deformation

b) In the second stage, the pump discharge rate shall be maintained at as constant a level as is possible until the gas cylinder bursts

10.4.3 Interpretation of test

10.4.3.1 The interpretation of the burst test shall involve

a) examination of a pressure/time curve or a curve of pressure vs volume of water used, in order to permit determination of the pressure at which plastic deformation of the gas cylinder commences, together with the burst pressure and volumetric expansion of the gas cylinder during the test, and

b) examination of the burst tear and of the shape of its edges

10.4.3.2 For the results of a burst test to be considered satisfactory, the following requirements shall be met:

a) The observed yield pressure, py, shall be equal to or greater than 1/F  the test pressure, i.e

10.4.3.3 The gas cylinder shall remain in one piece and shall not fragment

10.4.3.4 The main tear shall not be of a brittle type, i.e the edges of the fracture shall not be radial but shall be sloping in relation to a diametral plane The tear shall not reveal a significant defect in the metal

10.4.3.5 The fracture shall be considered acceptable only if it conforms to one of the following descriptions:

a) For gas cylinders of actual wall thickness 13 mm or less:

 the greater part of the fracture shall be unmistakably longitudinal except for gas cylinders where the ratio of length to outside diameter is less than 3:1;

 at each end of the fracture, no more than two branches (see L′ and L′′ in Figure 7) shall be allowed,

and only if the shorter branch, which may be at either end, is less than 20 mm long;

 the fracture shall not extend more than 90° around the circumference on either side of its main part

(see d′ and d′′ in Figure 7);

 the fracture shall not extend into those parts of the gas cylinder of thickness more than 1,5  the maximum thickness measured halfway up the gas cylinder (for gas cylinders with convex bases, the fracture shall not reach the centre of the gas cylinder base)

b) For gas cylinders of actual wall thickness over 13 mm, the greater part of the fracture shall be longitudinal

10.5 Test requirements for high-strength and/or low-elongation gas cylinder designs

High-strength and/or low-elongation gas cylinder designs shall be subject to the requirements of Annex E

Figure 7 — Illustration of circumferential development of fracture

11 Gas cylinder tests and examinations

11.1 General

At the time of production, the examinations required in 8.3 and 8.4 shall be performed on each cylinder

Following final heat treatment (see 6.2), all gas cylinders, except those selected for testing under Clause 10, shall be subjected to the following tests:

 Either a hydraulic proof pressure test in accordance with 11.2.1 or a hydraulic volumetric-expansion test

in accordance with 11.2.2 The requirements to be met are given in 11.2.1 and 11.2.2, respectively Additional guidance on these test methods and details of equipment calibration and maintenance can be found in ISO 10461 The purchaser and manufacturer shall agree which of these alternatives shall be carried out

 A hardness test in accordance with 11.3

 A leak test in accordance with 11.4

 An examination for neck folds in accordance with 11.5

11.2 Hydraulic test

11.2.1 Proof pressure test

The water pressure in the gas cylinder shall be increased at a controlled rate until the test pressure, ph, is reached

The gas cylinder shall remain under pressure ph for at least 30 s to establish that the pressure does not fall

and that there are no leaks The pressure may exceed ph by 3 % of ph or by 10 bar, whichever is the lower After the test, the gas cylinder shall show no visible permanent deformation

The gas cylinder shall be rejected if it shows a permanent expansion (i.e volumetric expansion after the pressure has been released) in excess of 5 % of the total volumetric expansion measured at the test

pressure, ph

The total and permanent expansion readings shall be recorded, together with the corresponding serial number

of each gas cylinder tested, so that the elastic expansion (i.e total expansion less permanent expansion) under the test pressure can be established for each gas cylinder

11.3 Hardness test

A hardness test in accordance with ISO 6506-1 (Brinell), ISO 6508-1 (Rockwell B) or another, equivalent, method (e.g the rebounding-ball, coefficient of restitution method) shall be carried out by the manufacturer The hardness values thus determined shall be within the limits specified by the gas cylinder manufacturer for the material and manufacturing route, dependent upon the final treatment used for the production of the gas cylinder The values may be expressed in Brinell, Rockwell B or other, equivalent, units

By agreement with the Inspection Body, the hardness test may be replaced by an electrical-conductivity test

11.4 Leakage testing

The manufacturer shall employ such manufacturing techniques and apply such tests as will demonstrate to the satisfaction of the Inspection Body that the gas cylinders do not leak

11.5 Examination for neck folds

Each gas cylinder shall be examined for neck folds by a suitable means (e.g scope, tactile, ultrasonic, etc) Severe folds might adversely affect the performance of the gas cylinder or the integrity of the gas cylinder To assess the effect of any severe folds in the gas cylinder, gas cylinders with such folds shall be used for batch pressure-cycling and burst tests In addition, gas cylinders with folds that exceed two continuous threads shall

be condemned

Folds that do not adversely affect the performance or the integrity of the gas cylinder may be machined until the lines are no longer visible (i.e repaired) Gas cylinders with folds running into two or less threads (as shown on the left-hand side of Figure 8) may be repaired If a gas cylinder is repaired in this way, the thread shall still meet the minimum requirements for length and number as per the relevant standard In addition, the remaining thickness of the machined area and the thread′s characteristics shall be at least those required to pass all necessary testing The whole internal shoulder area shall be re-inspected to verify that folding or its lines have been removed

11.6 Marking verification

Gas cylinder markings shall be verified to be in accordance with Clause 13

11.7 Aluminium alloy gas cylinder surface features at time of manufacture

11.7.1 Requirements

At the time of manufacture, finished gas cylinders shall have no feature which adversely affects gas cylinder performance or integrity (see 8.4 and specific unacceptable imperfections in other subclauses in Clause 8 and

in this subclause) Such features are considered to be defects

At the time of manufacture, finished gas cylinders shall have no surface imperfections which would be considered to be unacceptable according to ISO 10461

The integrity and performance of gas cylinders with questionable features identified by the Inspection Body shall be verified by testing samples from the batch in accordance with the test procedures and criteria in this International Standard The batch shall be condemned if the tests show unacceptable results and deemed acceptable if the tests show acceptable results

Surface imperfections may be dressed or repaired provided the gas cylinder wall thickness meets or exceeds the thickness required by this International Standard

11.7.2 Imperfection considerations

Annex F lists and describes gas cylinder surface imperfections and gives the criteria by which they may be assessed Those imperfections which are acceptable should be agreed upon between the manufacturer and purchaser Purchasers may specify surface imperfection criteria such as those listed in Annex F or establish their own criteria, provided such criteria do not conflict with the requirements specified in 11.7.1

Key

1 folds

2 folds machined away

Figure 8 — Example of gas cylinder neck folds before and after machining

12 Certification

Each satisfactory batch of gas cylinders shall be covered by a certificate, signed by a party designated by the relevant competent authority, to the effect that the gas cylinders meet the requirements of this International Standard in all respects An example of a suitably worded certificate is given in Annex D

Copies of the certificate shall be issued to the manufacturer The original certificate shall be retained by the Inspection Body and the manufacturer′s copies shall be retained by the manufacturer in accordance with the regulations of the relevant competent authority

to the etched surface

A.1.2 Taking specimens

Take specimens from the head, body and base of the gas cylinder (see Figure A.1) so that the tests with the solution specified in A.1.4.1 can be carried out on metal from three parts of the gas cylinder

Each specimen shall be of the dimensions and general shape indicated in Figure A.2

Faces a1a2a3a4, b1b2b3b4, a1a2b2b1 and a4a3b3b4 shall all be sawn with a band saw and then carefully trimmed with a fine file Surfaces a1a4b4b1 and a2a3b3b2, which correspond respectively to the inner and outer faces of the gas cylinder, shall be left in their rough state

A.1.3 Preparation of surface before corrosive etching

A.1.3.1 Reagents

A.1.3.1.1 Nitric acid (HNO3), analytical grade, density 1,33 g/cm3

A.1.3.1.2 Hydrofluoric acid (HF), analytical grade, density 1,14 g/cm3 (at 40 %)

A.1.3.1.3 Deionized or distilled water

Figure A.1 — Locations of specimens

Dimensions in millimetres

10 %

Key

1 hole, ∆ 3 mm

2 thickness of gas cylinder wall

Figure A.2 — Specimen shape and dimensions

Bring the solution to a temperature of 95 °C

Treat each specimen, suspended on a wire made of aluminium or another inert material, in this solution for

1 min

Wash in running water and then in deionized or distilled water (A.1.3.1.3)

Immerse each specimen in nitric acid (A.1.3.1.1) for 1 min at room temperature to remove any copper deposit which may have formed

Rinse in deionized or distilled water

To prevent oxidation of specimens, plunge them, as soon as they have been prepared, into the corrosion bath intended for them (see A.1.4.1)