SIST EN ISO 11120:2000
(Main)Gas cylinders - Refillable seamless steel tubes for compressed gas transport, of water capacity between 150 l and 3000 l - Design construction and testing (ISO 11120:1999)
Gas cylinders - Refillable seamless steel tubes for compressed gas transport, of water capacity between 150 l and 3000 l - Design construction and testing (ISO 11120:1999)
This International Standard specifies minimum requirements for the material, design, construction and workmanship, manufacturing processes and tests at manufacture of refillable quenched and tempered seamless steel tubes of water capacities from 150 litres up to and including 3000 litres for compressed and liquefied gases exposed to extreme world-wide ambient temperatures (normally between - 50 °C and + 65 °C). This International Standard is applicable to cylinders with a maximum tensile strength Rm of less than 1100 MPa.
Ortsbewegliche Gasflaschen - Nahtlose wiederbefüllbare Großflaschen aus Stahl mit einem Fassungsraum zwischen 150 l und 3000 l - Gestaltung, Konstruktion und Prüfung (ISO 11120:1999)
Diese Internationale Norm enthält Mindestanforderungen an den Werkstoff, Gestaltung, Konstruktion, Bau, Inspektion und Zulassung und das Herstellungsverfahren von wiederbefüllbaren vergüteten, nahtlosen Großflaschen aus Stahl mit einem Fassungsraum von 150 l bis einschließlich 3000 l, für verdichtete und verflüssigte Gase, die weltweit extremen Umgebungstemperaturen (normalerweise zwischen - 50°C und + 65°C) ausgesetzt sind. Diese Internationale Norm gilt für Flaschen mit einer maximalen Zugfestigkeit bis zu 1100 MPa.
Bouteilles a gaz - Tubes en acier sans soudure rechargeables d'une contenance en eau de 150 l a 3000 l - Conception, construction et essais (ISO 11120:1999)
La présente Norme internationale spécifie les exigences minimales concernant le matériau, la conception, la construction et la bonne exécution, les procédés de fabrication et les essais au moment de la fabrication des tubes en acier sans soudure, trempés et revenus, rechargeables, d'une contenance en eau de 150 litres à 3000 litres inclus, destinés aux gaz comprimés et liquéfiés exposés à des températures ambiantes extrêmes (généralement comprises entre - 50 °C et + 65 °C). La présente Norme internationale s'applique aux tubes de résistance à la traction maximale, Rm, inférieure à 1100 MPa. Ces tubes peuvent être utilisés seuls ou en batteries afin d'équiper des remorques ou des traîneaux (modules ISO) pour le transport et la distribution de gaz comprimés. La présente Norme internationale ne traite pas des contraintes supplémentaires pouvant se produire au cours de service ou du transport, par exemple, les contraintes de flexion, etc.
Plinske jeklenke - Ponovno polnljive velike jeklenke iz celega iz jekla za transport stisnjenega plina vodne prostornine od 150 do 3000 l - Konstruiranje, izdelava in preskušanje
Ta mednarodni standard določa minimalne zahteve za material, konstruiranje, izdelavo in izvedbo, postopke izdelave in preskuse ob času izdelave ponovno polnljivih velikih jeklenk iz kaljenega in popuščenega jekla vodne prostornine od 150 litrov do vključno 3000 litrov za stisnjene in utekočinjene pline, izpostavljene ekstremnim temperaturam okolja po vsem svetu (običajno med –50 °C in +65 °C). Ta mednarodni standard se uporablja za jeklenke z največjo natezno trdnostjo Rm, manjšo od 1100 MPa.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 11120:2000
01-januar-2000
Plinske jeklenke - Ponovno polnljive velike jeklenke iz celega iz jekla za transport
stisnjenega plina vodne prostornine od 150 do 3000 l - Konstruiranje, izdelava in
preskušanje
Gas cylinders - Refillable seamless steel tubes for compressed gas transport, of water
capacity between 150 l and 3000 l - Design construction and testing (ISO 11120:1999)
Ortsbewegliche Gasflaschen - Nahtlose wiederbefüllbare Großflaschen aus Stahl mit
einem Fassungsraum zwischen 150 l und 3000 l - Gestaltung, Konstruktion und Prüfung
(ISO 11120:1999)
Bouteilles a gaz - Tubes en acier sans soudure rechargeables d'une contenance en eau
de 150 l a 3000 l - Conception, construction et essais (ISO 11120:1999)
Ta slovenski standard je istoveten z: EN ISO 11120:1999
ICS:
23.020.30 7ODþQHSRVRGHSOLQVNH Pressure vessels, gas
MHNOHQNH cylinders
SIST EN ISO 11120:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 11120:2000
INTERNATIONAL ISO
STANDARD 11120
First edition
1999-03-15
Gas cylinders — Refillable seamless steel
tubes of water capacity between 150 l and
3 000 l — Design, construction and testing
Bouteilles à gaz — Tubes en acier sans soudure rechargeables
d'une contenance en eau de 150 l à 3 000 l — Conception, construction
et essais
A
Reference number
ISO 11120:1999(E)
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SIST EN ISO 11120:2000
ISO 11120:1999(E)
Contents Page
1 Scope .1
2 Normative references .1
3 Definitions .2
4 Symbols.3
5 Inspection and testing.3
6 Materials .3
7 Design.6
8 Construction and workmanship.7
9 Batch tests.8
10 Tests on every cylinder.9
11 Special requirements for tubes for embrittling gases .11
12 Marking .13
Annex A (normative) ISO High-pressure gas tube/cylinder chemistry groupings.14
Annex B (normative) Ultrasonic inspection .15
Annex C (informative) Description, evaluation of manufacturing defects and conditions for rejection of
seamless steel tubes at time of visual inspection.20
Annex D (informative) Acceptance certificate .27
(informative)
Annex E Checklist for production testing.29
Bibliography.30
© ISO 1999
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 the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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SIST EN ISO 11120:2000
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ISO 11120:1999(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 3.
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 11120 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee
SC 3, Cylinder design.
Annexes A and B form an integral part of this International Standard.
Annexes C, D and E are for information only.
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SIST EN ISO 11120:2000
© ISO
ISO 11120:1999(E)
Introduction
The purpose of this International Standard is to provide a specification for the design, manufacture, inspection and
testing of tubes for worldwide usage. The objective is to balance design and economic efficiency against international
acceptance and universal utility.
This International Standard aims to eliminate 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.
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SIST EN ISO 11120:2000
INTERNATIONAL STANDARD © ISO ISO 11120:1999(E)
Gas cylinders — Refillable seamless steel tubes of water capacity
between 150 l and 3 000 l — 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 quenched and tempered seamless
steel tubes of water capacities from 150 l up to and including 3 000 l for compressed and liquefied gases exposed to
extreme world-wide ambient temperatures (normally between 250 °C and 165 °C). This International Standard is
applicable to tubes with a maximum tensile strength R of less than 1 100 MPa.
m
These tubes can be used alone or in batteries to equip trailers or skids (ISO modules) for the transportation and
distribution of compressed gases.
This International Standard does not include consideration of any additional stresses that may occur during service
or transport, e.g. bending stresses, etc.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this
International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do
not apply. However, parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated references,
the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of
currently valid International Standards.
1)
ISO 148 , Steel — Charpy impact test (V-notch).
2)
ISO 6506 , Metallic materials — Hardness test — Brinell test.
ISO 6892, Metallic materials — Tensile testing at ambient temperature.
ISO 11114-1, Transportable gas cylinders — Compatibility of cylinder and valve materials with gas contents —
Part 1: Metallic materials.
ISO 11484, Steel tubes for pressure purposes — Qualification and certification of non-destructive testing (NDT)
personnel.
1)
To be replaced by ISO 148-1, ISO 148-2 and ISO 148-3.
2)
To be replaced by ISO 6506-1, ISO 6506-2 and ISO 6506-3.
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3 Definitions
For the purposes of this International Standard the following definitions apply.
3.1
yield stress
value corresponding to the 0,2 % proof stress, R
p 0,2
3.2
quenching
hardening heat treatment in which a tube, which has been heated to a uniform temperature above the upper critical
point Ac of the steel, is cooled rapidly in a suitable medium
3
3.3
tempering
softening heat treatment which follows quenching, in which the tube is heated to a uniform temperature below the lower
critical point Ac of the steel
1
3.4
tube
a double ended pressure gas cylinder manufactured from seamless tubing
3.5
batch
a quantity of up to 200 tubes of the same nominal diameter, thickness and design made from the same steel cast and
subjected to the same heat treatment for the same duration of time
3.6
test pressure
required pressure (p ) applied during a pressure test
h
3.7
design stress factor
F
ratio of the equivalent wall stress at test pressure (p ) to guaranteed minimum yield stress (R )
h e
2
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4 Symbols
Symbol Definition
a calculated minimum thickness, in millimetres, of the cylindrical shell
a' guaranteed minimum thickness, in millimetres, of the cylindrical shell
A percentage elongation
D nominal outside diameter of the tube, in millimetres
f a constant in the design stress factor (see 11.3)
design stress factor (see 3.7)
F
L original gauge length, in millimetres, according to ISO 6892
0
a
p
hydraulic test pressure, in bar above atmospheric pressure
h
a
R
guaranteed minimum value of yield stress, in megapascals
e
R value of the actual yield stress, in megapascals, determined by the tensile test
ea
R guaranteed minimum value of the tensile strength, in megapascals
g
R actual value of tensile strength, in megapascals, determined by the tensile test
m
S original cross-sectional area of tensile test piece, in square millimetres, according to ISO 6892
0
a 1 bar = 100 kPa; 1 MPa = 10 bar.
5 Inspection and testing
Evaluation of conformity is required to be performed in accordance with the relevant regulations of the country(ies)
where the tubes are to be used.
In order to ensure that tubes are in compliance with this International Standard they shall be subject to inspection in
accordance with clauses 9 and 10 by an authorized inspection body (hereafter referred to as “the inspector”)
recognized in the countries of use. The inspector shall be competent for inspection of tubes.
6 Materials
6.1 General requirements
6.1.1 Materials for the manufacture of tubes shall meet the requirements of 6.2, 6.3 and 6.4.
Steels for the fabrication of tubes shall be of nationally or internationally recognized compositions having proven
reliability. These steels shall fall within one of the chemical groups as shown in annex A.
New steel compositions, and steels for which limited experience exists in tube/cylinder service, shall be fully tested and
approved by a national authority and have been manufactured from not less than five casts of steel.
The manufacturer of the finished tube shall provide a detailed specification with tolerances for the supplied tubing
including:
chemical composition;
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SIST EN ISO 11120:2000
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ISO 11120:1999(E)
dimensions;
surface quality.
6.1.2 The steel used for the fabrication of tubes shall be fully killed.
6.1.3 The manufacturer of the tubing shall supply certificates of a reference heat treatment representative of the
final heat treatment.
NOTE Additional requirements related to tubes for use with embrittling gases are given in clause 11.
6.2 Controls on chemical composition
6.2.1 A steel is defined by the steel-making process and by its chemical composition.
Steel-making shall be defined by reference to a given process (oxygen converter, electric arc furnace or equivalent)
and to the killing method.
The chemical composition of the steel shall be defined at least by:
the carbon, manganese and silicon contents in all cases;
the chromium, nickel, molybdenum, vanadium or niobium contents when these are alloying elements
intentionally added to the steel;
the maximum sulphur and phosphorus contents in all cases.
The carbon, manganese and silicon contents and, where appropriate, the chromium, nickel, molybdenum, vanadium or
niobium contents shall be given, with tolerances, such that the differences between the maximum and minimum values
of the cast do not exceed the ranges shown in Table 1.
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SIST EN ISO 11120:2000
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Table 1 — Chemical composition tolerances
Element Content Permissible range
Carbon , 0,30 % 0,06 %
> 0,30 % 0,07 %
Manganese all contents 0,30 %
Silicon all contents 0,30 %
Chromium , 1,50 % 0,30 %
> 1,50 % 0,50 %
Nickel all contents 0,40 %
Molybdenum all contents 0,15 %
Vanadium all contents 0,10 %
Niobium all contents 0,10 %
Elements not included in the declared chemical composition shall not be deliberately added. The content of such
elements shall be limited to ensure that they have no detrimental effect on the properties of the finished product.
6.2.2 The maximum sulphur and phosphorus contents in the cast analysis shall not exceed 0,020 % each and their
sum shall not exceed 0,030 %. Check analyses of the supplied tubing shall not exceed 0,025 % and 0,035 %
respectively.
6.2.3 The manufacturer of the finished tube shall obtain and produce certificates of cast (heat) analyses of steels
supplied for the construction of tubes.
6.3 Heat treatment
6.3.1 Each tube shall be heat treated, and for each stage of treatment, i.e. quenching and tempering, the heat
treatment procedure shall include a record of:
the temperature;
the temperature holding time;
the cooling medium.
6.3.2 Heat treatment shall be carried out in such a way that it does not induce excessive stresses which may
initiate irreversible failures in the tube.
6.3.3 The austenization temperature prior to quenching shall be defined within ± 30 °C of the temperature retained
for the steel type under consideration, but it shall never be less than the upper critical point (Ac ) of the steel
3
concerned.
6.3.4 Quenching in media other than oil or air is permissible provided that the method produce tubes free of cracks
as verified by non destructive testing.
6.3.5 The tempering temperature shall be defined within ± 30 °C of the temperature for guaranteeing specified
mechanical properties but shall not be less than 540 °C.
6.4 Mechanical properties
The material of the finished tube shall satisfy the requirements of 9.2 and 10.4.
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6.5 Failure to meet test requirements
In the event of failure to meet test requirements, retesting or reheat treatment and retesting shall be carried
6.5.1
out as follows:
a) If there is evidence of a fault in carrying out a test, or an error of measurement, a further test shall be
performed. If the result of this test is satisfactory, the first test shall be ignored.
b) If the test has been carried out in a satisfactory manner, the cause of test failure shall be identified.
1) If the failure is considered to be due to the heat treatment applied, the manufacturer may subject all the
tubes of the batch to a further heat treatment.
2) If the failure is not due to the heat treatment applied, all the identified defective tubes shall be rejected or
repaired by an approved method. The non-rejected and repaired tubes are then considered as a new
batch.
In both cases the new batch shall be tested by the inspector. All the relevant batch tests needed to prove the
acceptability of the new batch shall be performed again. If one or more tests prove even partially
unsatisfactory, all the tubes of the batch shall be rejected.
Where reheat-treatment is required, the tubes shall be retempered or requenched and tempered.
6.5.2
A maximum of two reaustenitizing treatments is permitted.
Whenever tubes are reheat-treated the wall thickness can be affected by scale formation, therefore the minimum
design wall thickness shall be checked in the finished tube.
7 Design
7.1 Calculation of cylindrical shell thickness
The guaranteed minimum thickness of the cylindrical shell (a') shall be not less than the thickness calculated using
the Lamé-von Mises formula, as follows:
10 FR− 3 p
D
e h
a=−1
2 10 FR
e
0,65
where the value of F is the lesser of or 0,85
RR/
eg
R /R shall not exceed 0,90.
e g
Additional requirements related to tubes for use with embrittling gases are given in clause 11.
NOTE Regional international agreements may limit the magnitude of the factor used for design.
F
7.2 Design of tube ends
Tube ends shall be approximately hemispherical with thickness not less than the calculated minimum wall thickness, a.
The dimensions of the tube end profiles shall be specified for each design taking into consideration the stress
distribution and the manufacturing process.
To permit internal visual inspection of the tube, an adequate opening shall be provided at the neck ends. The nominal
diameter of the opening shall be greater than D/12.
NOTE Stress analysis should be carried out to ensure that design limits are not exceeded, in particular where this opening
is large.
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When the tube ends are threaded, the thickness at the thread root shall be sufficient to take into account the developed
stress in this part.
8 Construction and workmanship
8.1 General
The tube shall be manufactured from seamless steel tubing, typically hot rolled, extended or forged.
The ends shall be hot formed using either forging or spinning methods.
Metal shall not be added in the process of closure of the end.
Repair of defects by welding is prohibited.
8.2 Wall thickness
Each length of supplied tubing shall be examined to determine thickness.
The wall thickness at any point shall be not less than the minimum thickness specified.
Checking for wall thickness shall be by the ultrasonic method in accordance with annex B.
8.3 Surface defects
The internal and external surfaces of the finished tube shall be free from defects which would adversely affect the safe
working of the tube. See annex C for examples of defects and guidance on their evaluation.
8.4 Ultrasonic examination
Each tube shall be ultrasonically examined for defects in accordance with annex B.
Examination of tubes to be used for embrittling gases (e.g. hydrogen) shall be carried out both on the supplied
tubing and at completion of tube manufacture. For tubes containing other gases examination may be carried out
either during or at the completion of manufacture.
8.5 End closure (fitting)
Closure of the finished tube shall be accomplished by a method other than welding, brazing or brazewelding, and shall
be capable of preventing leakage.
8.6 Dimensional tolerances
8.6.1 Out-of-roundness
The out-of-roundness of the cylindrical shell, i.e. the difference between the maximum and minimum outside diameters
at the same cross-section, shall not exceed 2 % of the mean value of these diameters measured at least at the quarter
and mid-length locations on the tube.
8.6.2 Outside diameter
The mean external diameter shall not deviate by more than ± 1 % from the nominal design diameter; this shall be
verified at the quarter and mid-length locations on the tube.
8.6.3 Straightness
The maximum deviation of the cylindrical part of the shell from a straight line shall not exceed 3 mm per metre length.
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8.6.4 Eccentricity
The values of the minimum and maximum thicknesses shall differ by no more than 12,5 % from the mean value of
these two thicknesses; this shall be verified at least at the quarter and mid-length locations on the tubes.
8.6.5 Length
The tolerance on the design overall length of the tube only, excluding fittings, shall not exceed the lesser of ± 1,5 % or
± 50 mm.
8.6.6 Water capacity
+10
The tolerance on the design water capacity shall be within the range %.
0
8.6.7 Mass
The tolerance on design mass of any individual tube shall not exceed ± 10 %.
If tubes are intended to constitute a battery, the tolerance on the shipment average tube mass shall be within the range
+ 5
% of the unit design mass.
10
−
9 Batch tests
9.1 General requirements
The following tests and inspections shall be carried out under the responsibility of the inspector (see clause 5).
NOTE The type approval procedures normally used for cylinders of nominal water capacity less than 150 l are not
applicable to the production runs for tubes.
9.2 Mechanical tests
9.2.1 General
From each production batch, test pieces shall be selected for mechanical testing from a ring of material of minimum
length 200 mm taken from supplied tubing which is representative of the final condition of the tube(s), including any
heat treatment.
The sample as defined above shall be placed so it is subjected at the same time as the tube(s) to the same heat
treatment conditions, including with respect to single- or double-sided quenching.
9.2.2 Tensile test
The test shall be carried out in accordance with ISO 6892 on a cylindrical proportional test piece taken longitudinally
(along the axis of the ring) in the ring wall and machined. The gauge length of the test piece L shall be equal to
0
56,S5
0
The results of the tensile test shall be at least equal to the minimum guaranteed values of the properties, and in all
cases:
R shall not exceed 1 100 MPa;
m
the elongation after fracture shall be not less than 14 %;
the ratio R /R shall be not more than 0,95.
ea m
NOTE Additional requirements related to tubes for use with embrittling gases are given in clause 11.
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9.2.3 Impact testing
9.2.3.1 Except for the requirements set out below, the test shall be carried out in accordance with ISO 148.
The test shall be carried out on three test pieces taken longitudinally from the sample ring wall. The notch shall be
perpendicular to the face of the sample ring wall. The test pieces shall be machined on all six faces. If the wall
thickness does not permit a final test piece width of 10 mm, the width shall be as near as practicable to the nominal
thickness of the tube wall. If the wall thickness is greater than 10 mm, the test pieces shall be taken as near as
practicable to the inner surface of the sample ring and their thickness limited to 10 mm.
9.2.3.2 The impact test shall be conducted at a temperature of 220 °C and the impact test values shall meet the
following requirements:
2
individual values > 40 J/cm ;
2
mean value > 50 J/cm .
If agreed between the manufacturer and purchaser, impact tests at lower temperatures may be carried out according to
the condition of use provided that the foregoing test requirements are also satisfied.
9.3 Interpretation of results
Except as allowed for in 6.5, the finished tubes shall satisfy the requirements of clause 6, and of 9.2 and 10.4.
10 Tests on every cylinder
10.1 General
Following heat treatment, all tubes shall be subjected to the following tests and inspections under the responsibility of
the inspector:
either a hydraulic proof pressure test in accordance with 10.2.1 or a volumetric expansion test in accordance
with 10.2.2;
a hardness test in accordance with 10.3;
a visual inspection in accordance with 10.4;
a dimensional inspection in accordance with 10.5;
ultrasonic non-destructive testing (NDT) in accordance with 10.6.
10.2 Hydraulic test
10.2.1 Proof pressure test
The hydraulic pressure in the tube shall be increased at a controlled rate until the test pressure, p , is reached with a
h
+ 3
tolerance of %. The test is normally carried out using water. All necessary precautions shall be taken to guarantee
0
the safety of persons and property. The tube test pressure shall be held for a sufficiently long period (at least 2 min) to
ascertain that there is no tendency for the pressure to decrease or for permanent visible deformation and that the tube
does not leak.
The test mounting shall be so designed and arranged as to permit easy checking of the tube tightness. It shall be fitted
with calibrated pressure gauge(s). Any internal pressure applied to the tube after heat treatment and before the official
pressure test shall not exceed 90 % of the test pressure, p .
h
After testing the interior of the tube shall be dried to avoid oxidation.
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10.2.2 Volumetric expansion test
The hydraulic pressure in the tube shall be increased at a controlled rate until the test pressure, p , is reached with a
h
+3
tolerance of %. The test is normally carried out using water. The tube test pressure shall be held for a sufficiently
0
long period to ensure complete expansion of the tube, and in no case shall the pressure be held for less than 2 min.
The total volumetric expansion shall be measured. The pressure shall then be released and the volumetric expansion
remeasured.
The tube shall be rejected if it shows permanent expansion (i.e. volumetric expansion after the pressure has been
released) in excess of 10 % of the total volumetric expansion measured at the test pressure, p .
h
The total and permanent expansion reading shall be recorded, together with the corresponding serial number of the
tube tested so that the elastic expansion (i.e. total expansion minus permanent expansion), can be established for
each tube.
The test apparatus shall be fitted with at least two calibrated pressure gauges arranged in a parallel configuration to
check the accuracy of the pressure applied to the tube. Any internal pressure applied to the tube after heat treatment
and before the official pressure test shall not exceed 90 % of the test pressure, p .
h
After testing, the interior of the tube shall be dried to avoid oxidation.
10.3 Hardness testing
The purpose of this test is to check the homogeneity of the heat treatment of a tube batch.
A Brinell hardness test shall be conducted on each tube in accordance with ISO 6506, preferably with a ball having a
diameter of 10 mm and at a 29 420 N (3 000 kgf) load, except when circumstances do not permit.
The conversion of hardness test results into tensile strength values shall be determined by the tube manufacturer,
using test pieces representative of the manufactured tubes.
Hardness shall be measured and recorded at four diametrically opposed points in at least three circular cross-sections
distributed over the whole length of each tube at intervals of not greater than 3 m.
The average of the results on each circular cross-section shall be within the minimum-maximum tensile strength range
guaranteed by the manufacturer. The values may be plotted on a diagram to identify their position.
10.4 Visual inspection
The inner and outer surfaces of each finished tube shall be inspected visually for cleanliness and defects in
accordance with 8.3.
This is intended to check, in particular for the inner surface, that:
no foreign matter or grease is present;
no liquid or moisture is present inside the tube;
no shoulder cracks are present.
Light, tightly adhering scale or blush rust oxide is acceptable unless expressly prohibited by the final application.
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10.5 Dimensional inspection
10.5.1 Thickness
Inspection of wall thickness to check conformity with the requirements of 8.2 and 8.6.4 shall be carried out on each
tube at any manufacturing stage chosen by the manufacturer. The manufacturer shall ensure that no noticeable
reducti
...
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