INTERNATIONAL STANDARD ISO 11114-4 Second edition 2017-04 Transportable gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 4: Test methods for selecting steels resistant to hydrogen embrittlement Bouteilles gaz transportables — Compatibilité des matériaux et des robinets avec les contenus gazeux — Partie 4: Méthodes d’essai pour le choix des aciers résistants la fragilisation par l’hydrogène Reference number ISO 11114-4:2017(E) © ISO 2017 ISO 11114-4:2017(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Contents Page Foreword iv Introduction v Scope Normative references Terms, definitions, symbols and abbreviated terms General requirements Test methods 5.1 Disc test (method A) 5.1.1 Principle of test 5.1.2 Test conditions and procedure 5.1.3 Treatment and interpretation of test results 5.1.4 Failure in conducting test 5.1.5 Test report 5.2 Fracture mechanics test (method B) 10 5.2.1 Principle of the test method 10 5.2.2 Test procedure 10 5.2.3 Test results 14 Terms and definitio ns Symb o ls and ab b reviated terms Tes t metho d to determine the res is tance to hydro gen as s is ted cracking o f s teel 14 General 14 f 15 15 5.3.4 Specimen testing procedure 15 5.3.5 Test procedure 16 16 17 5.3.8 Failure in conducting test 17 5.3.9 Test report 17 Tensile tests 17 cylinders (metho d C ) 5.3.1 5.4 S p ecimen co nfiguratio ns and numb ers o 3 Fatigue p recracking C rack gro wth examinatio n Cylinder material qualificatio n tes ts Bibliography 18 © ISO 2017 – All rights reserved iii ISO 11114-4:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f 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 o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the meaning o f ISO specific terms and expressions related to formity assessment, as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html The committee responsible for this document is ISO/TC 58, Gas cylinders This second edition cancels and replaces the first edition (ISO 11114-4:2005), which has been technically revised with the following changes: — improvement o f the procedure corresponding to Method C and adjustment o f acceptance criteria; — light modifications on procedures corresponding to Method A and Method B A list of parts in the ISO 11114 series can be found on the ISO website iv © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Introduction It is widely recognized that compressed hydrogen and some hydrogen bearing gases can have an embrittling e ffect on steels This embrittling e ffect has resulted in the failure o f hydrogen gas cylinders (including some bursts) that has led gas cylinder users and manu facturers to adopt specific measures The adoption o f these measures has eliminated all known failures o f hydrogen cylinders from this embrittlement phenomenon as far has been reported The basic recommendation is to limit the tensile strength of the steels (see ISO 11114-1) and eliminate manufacturing defects This tensile strength limit o f 950 MPa was developed for quenched and tempered gas cylinders o f 34 Cr Mo type steels using steelmaking practices, chemistry and manu facturing techniques typical o f those used during the early 1980’s and success fully used for filling pressures up to 300 bar This practice has been in widescale use up to the current time Other higher pressures, although at lower tensile strength limits, have also been used In recent years, improvements in steelmaking, e.g by reducing the sulphur and phosphorus contents, have indicated the possibility o f increasing the tensile strength limit o f 950 MPa for embrittling gas service Experimental work has shown that the relevant parameters a ffecting hydrogen embrittlement are the following: a) microstructure resulting from the combination o f the chemistry and the heat treatment; b) mechanical properties o f the material; c) applied stress; d) internal sur face imper fections resulting in local stress concentrations; e) characteristics o f the gas contained (composition, quality, pressure, etc.) When developing this document, only the material aspects, a) and b) and the characteristics o f the gas e) above, were considered Other essential features, c) and d), are covered by the relevant parts o f ISO 9809 Some low alloy steels other than 34 Cr Mo may require tensile strength to be lower than 950 MPa, or may be permitted to be higher than 950 MPa, to be suitable for the manu facture o f gas cylinders for embrittling gas service This document specifies test methods to identi fy steels which, when combined with the cylinder manu facturing requirements specified in ISO 9809 (all parts), will result in cylinders suitable for use in embrittling gas service These tests have been developed following an extensive world-wide programme which incorporated laboratory and full scale tests See also AFNOR FD E29-753 © ISO 2017 – All rights reserved v INTERNATIONAL STANDARD ISO 11114-4:2017(E) Transportable gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 4: Test methods for selecting steels resistant to hydrogen embrittlement Scope T h i s c u ment s p e ci fie s te s t me tho d s a nd the eva luation o f re s u lts s te el s s u itable for from the s e te s ts i n order to qua l i fy u s e i n the manu fac tu re o f ga s c yl i nders (up to 0 l) bearing embrittling gases for hyd ro gen a nd hyd ro gen T h i s c ument on ly appl ie s to s e a m le s s s te el gas c yl i nders The requirements of this document are not applicable if at least one of the following conditions for the i ntende d gas s er vice i s — fu l fi l le d: the worki ng pre s s ure o f the fi l le d embrittl i ng gas i s le s s than % o f the te s t pre s s u re o f the c yl i nder; — the p a r ti a l pre s s u re o f the fi l le d embrittl i ng ga s o f a ga s m i x tu re i s le s s th an M Pa (5 b a r) i n the c a s e o f hyd ro gen and o ther embrittl i ng ga s e s , with the e xcep tion o f hyd ro gen s u lph ide and me thyl merc ap tan; i n s uch c a s e s , the p a r ti a l pre s s u re s l l no t e xce e d , M Pa (2 , b ar) NO TE I n s uch c a s e s , it i s p o s s ib le to de s ign the c yl i nder a s fo r o rd i n a r y (non- emb r ittl i ng) ga s e s Normative references T he fol lowi ng c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content s titute s re qu i rements o f th i s c u ment For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c ument (i nclud i ng a ny amend ments) appl ie s ISO 7539-1, Corrosion ofmetals and alloys — Stress corrosion testing — Part 1: General guidance on testing procedures ISO 7539-6:2011, Corrosion of metals and alloys — Stress corrosion testing — Part 6: Preparation and use of precracked specimens for tests under constant load or constant displacement ISO 9809-1, Gas cylinders — Refillable seamless steel gas cylinders — Design, construction and testing — Part 1: Quenched and tempered steel cylinders with tensile strength less than 100 MPa ISO 9809-2, Gas cylinders — Refillable seamless steel gas cylinders — Design, construction and testing — Part 2: Quenched and tempered steel cylinders with tensile strength greater than or equal to 100 MPa ISO 11114-1:2012, Gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 1: Metallic materials ISO 11120, Gas cylinders — Refillable seamless steel tubes of water capacity between 150 l and 3000 l — Design, construction and testing © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Terms, definitions, symbols and abbreviated terms 3.1 Terms and definitions For the purposes o f this document, the following terms and definitions apply Some o f the definitions used are based upon those in ISO 7539-1 and ISO 7539-6 ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia org/ • ISO Online browsing platform: available at http://www.iso org/obp 3.1.1 embrittling gases gases which can cause cracking o f metal due to the combined action o f stress and hydrogen atoms Note to entry: Embrittling gases are listed as groups and 11 in ISO 11114-1:2012, A.4 3.1.2 hydrogen rupture pressure PH2 maximum pressure recorded during the hydrogen rupture pressure test 3.1.3 helium rupture pressure PHe maximum pressure recorded during the helium rupture pressure test 3.1.4 hydrogen embrittlement index maximum value of the ratio PHe/PH2 as a function of the pressure rise rate 3.1.5 environmentally-assisted cracking synergistic e ffect on a metal caused by the simultaneous action o f a particular environment and a nominally static tensile stress, which results in the formation o f cracking 3.1.6 threshold stress stress above which a crack will initiate and grow, for the specified test conditions 3.1.7 plane strain stress intensity factor K1 unction o f applied load, crack length and specimen geometry having dimensions o f stress × which uniquely define the elastic-stress field intensification at the tip o f a crack subjected to opening f length mode displacements (mode I) Note to entry: K1 uniquely defines the elastic stress field intensification at the tip o f a crack subjected to opening mode displacements 3.1.8 threshold stress intensity factor for susceptibility to environmentally-assisted cracking K1H stress intensity factor above which an environmentally-assisted crack will initiate and grow, for the specified test conditions under conditions o f high constraint to plastic de formation, i.e under essentially plane strain conditions © ISO 2017 – All rights reserved ISO 11114-4:2017(E) 3.2 Symbols and abbreviated terms a e ffective crack length measured from the crack tip to the loading plane a0 average value of a B specimen thickness em mean disc thickness E modulus o f elasticity KIAPP applied elastic stress-intensity factor threshold stress intensity factor K1H elastic displacement per unit load applied load actual rupture pressure corrected rupture pressure m P Pr Pr ′ Pr ′ H2 corrected hydrogen rupture pressure Pr ′ He theoretical helium rupture pressure corresponding to the same pressure rise rate as for the Rm actual value of tensile strength V crack-mouth opening displacement (CMOD) defined as the mode (also called opening-mode) component o f crack displacement due to elastic and plastic de formation, measured at the location on a crack sur face that has the greatest elastic displacement per unit load, m W e ffective width o f a compact specimen, measured from the back face to the loading plane Y stress intensity factor coe fficient derived from the stress analysis for a particular specimen geometry, which relates the stress intensity factor for a given crack length to the load and HAC hydrogen test, calculated by regression from the corrected helium rupture pressure specimen dimensions hydrogen assisted cracking General requirements The test methods as described in Clause are valid for all designed working pressures The test shall be per formed at room temperature at not less than the designed working pressure All tests shall be conducted to evaluate the hydrogen embrittlement taking into account conditions that will be found in the intended application The composition of the tested gas shall have a concentration of embrittling gas not less than the maximum concentration in the intended application The tests shall be performed for selecting steels for hydrogen/embrittling gases and mixtures cylinders Chromium-molybdenum steels, quenched and tempered with a guaranteed maximum actual ultimate tensile strength of 950 MPa, not need to be tested and can sa fely be used for the construction o f hydrogen/embrittling gases cylinders; however, H S mixtures at more than 100 bar working pressure need to be tested For carbonmanganese steels, di fferent limits on ultimate tensile strength apply (as described in ISO 9809-1) The tests described in Clause are “qualification tests” for a given steel composition and heat treatment This means that the tests need not be repeated for each type, as defined in ISO 9809 (all parts), o f cylinder once a steel has been qualified for a specific design strength level © ISO 2017 – All rights reserved ISO 11114-4:2017(E) The test samples shall be taken from a representative cylinder or from a piece o f tube (for long cylinders, according to ISO 11120), representative o f the relevant manu facturing process including heat treatment The test samples shall have a mechanical strength not lower than the maximum intended tensile strength to be used for the cylinders to be manu factured I f it is intended later to increase the maximum strength o f the steel, a new qualification test shall be per formed With respect to the possible variation o f the chemical composition, the chemistry o f the steel tested shall be recorded in the qualification test report and the di fference in chemistry for the steels actually used for the cylinders shall not exceed the “permissible di fference” according to ISO 9809-2 In addition, for sulphur and phosphorus, these permissible di fferences are limited to 0,005 % and 0,010 %, respectively In no case shall the phosphorus content o f either the qualification or the production cylinders exceed 0,015 % With respect to the heat treatment, the manu facturer shall speci fy the relevant temperatures and times, and the quenching conditions (i f relevant) Any modification to the heat treatment needing a new type approval according to ISO 9809-2 requires a new qualification test For the qualification o f a given steel for the manu facturing o f gas cylinders, method A, B, or C can be used (see 5.1, 5.2 and 5.3 , respectively) Additionally, tensile tests shall be carried out (see 5.4) Test methods 5.1 Disc test (method A) 5.1.1 Principle of test A mounted test piece in the shape o f a disc is subjected to an increasing gas pressure at constant rate to burst or to crack The embrittling e ffect o f hydrogen (or other embrittling gas) is evidenced by comparing the hydrogen rupture pressures, PH2 , with the helium rupture pressures, PHe , helium being chosen as a reference gas The ratio PHe/PH2 shall be determined The lower the ratio, the less susceptible the steel will be to embrittlement This ratio is dependent on the pressure rise rate, which shall remain constant during the whole test NOTE Hydrogen/embrittling gases rupture pressures also depend on the hydrogen purity Oxygen or traces o f water vapour can partially inhibit the hydrogen embrittlement e ffect 5.1.2 5.1.2.1 Test conditions and procedure Sample disc The sample disc shall be flat and ground (or machined to an equivalent sur face finish), and shall have the following characteristics Dimensions: — diameter: 58 −0,0 05 mm; — thickness: 0,75 mm ± 0,01 mm; — flatness: less than 1/10 mm deflection NOTE The hydrogen rupture pressures are in the range o f 300 bar I f it is intended to evaluate the steel for higher working pressure, thickness higher than 0,75 mm can be used © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Key dis c is s ub j ected to P dis c is s ub j ected to P NO TE H2 on the lower side N2 on the upper side T he d i s c i s lo ade d with Δ P = P H2 – PN2 Figure — Compensating pressure disc test principle T he rate o f pre s s u re compre s s ibi l ity fac tor ri s e sh a l l be regu la r a nd kep t as s tant as p o s s ible, negle c ti ng the gas with pre s s u re To eva luate the b ehaviour o f s te el s at pre s s u re h igher tha n 0 b ar, either a th icker d i s c s l l b e u s e d (see 5.1.2.1) or a compensating pressure of inert gas (see Figure f 5.1.1 at 700 bar) to evaluate the behaviour of the steel at about 700 bar) The rupture pressures shall be noted from the recorded readings at the end of the test The pressure ) sh a l l b e i ntro duce d pro gre s s ively i n the upp er p ar t o f the d i s c cel l at the s a me rate and pre s s u re a s hyd ro gen (e g up to 0 b a r) T hen, the hyd ro gen pre s s u re i s ur ther i ncre as e d as i nd ic ate d i n gauge s l l b e acc u rate to ± % for at a s tant rate to bu rs t or to c rack (e g the i ntende d me a s u re d rup tu re pre s s u re T he te s ts s l l b e c a rrie d out with hyd ro gen (for qua l ity, s e e 5.2.2.3) and with helium (H O < µl/l) for a nge o f pre s s ure ri s e rate s even ly d i s tribute d b e twe en ,1 b ar/m i n a nd 0 b ar/m i n O nce a nge o f pre s s ure ri s e rate s showi ng ma xi mu m hyd ro gen s en s itivity has b e en e s tabl i s he d, th re e add itiona l tests shall be conducted within this area, in order to establish the minimum value for the rupture pressure (see Figure f thorough material evaluation ) Si x hel iu m te s ts a nd ni ne hyd ro gen te s ts (i e te s ts i n to ta l) are enough 5.1.3 5.1.3.1 or a Treatment and interpretation of test results Disc thickness Rupture pressure Pr s l l b e s ys tematic a l ly corre c te d for devi ation from the “ide a l” va lue corre s p ond i ng to the te s t o f a s ta nda rd th ickne s s d i s c © ISO 2017 – All rights reserved ISO 11114-4:2017(E) The corrected rupture pressure, Pr Pr' = where em ′, s l l b e given b y Formula (1): Pr × , 75 em (1) i s the me an d i s c th ickne s s 5.1.3.2 Presentation and interpretation of test results Rupture pressures, corrected as indicated in 5.1.3.1, shall be plotted against the pressure rise rate Figure 3) Formula (2): Pr ′ He Pr ′ H2 (2) (ac tua l rup ture pre s s u re d ivide d b y the te s t du ration) expre s s e d i n b a r/m i n (s e e For e ach hyd ro gen te s t, c a lc u late the ratio given i n where Pr ′ He Pr ′ H2 is the theoretical helium rupture pressure corresponding to the same pressure rise rate as for the hyd ro gen tes t, ca lc u late d b y regre s s ion from the corre c te d hel ium rup ture pre s s ure; i s the corre c te d hyd ro gen rup tu re pre s s ure Ratios of Pr He/Pr H2 shall be plotted against the pressure rise rate (see Figure 4) The embrittlement index of a material is the maximum value of the above-mentioned ratio The material f f than or equal to two ′ ′ sh a l l b e s idere d as s u itable 5.1.4 or compre s s e d hyd ro gen/embrittl i ng gas c yl i nders i the i nde x i s le s s Failure in conducting test If it is found that a failure occurred during the conduction of a test (e.g inappropriate surface condition, abnormal hardness, irregular pressure rise), the test shall be repeated 5.1.5 Test report T he de tai le d te s t cond ition s (ga s pu rity, rup tu re pre s s ure, rd ne s s o f the s p e c i men, ratio embrittlement i nde x) / Pr ′ He Pr ′ H2 a nd the c yl i nder de s ign d rawi ng i nclud i ng the materia l prop er tie s , , chem ic a l comp o s ition and he at tre atment cond ition s o f the te s te d c yl i nder sh a l l b e rep or te d © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Key f discharge port bolt hole high-strength steel ring p o rt o r evacuatio n and flo w adj us tment up p er flange NO TE disc O-ring gas inlet lower flange T h i s figu re i s no t to s c a le S e e d i men s ion s i n 5.1.2.1 and 5.1.2.2 Figure — Schematic test installation (test cell) © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Key regression curve helium corrected rupture pressures (Pr′ He) hydrogen corrected rupture pressures (Pr′H2 ) X pressure rise rate (bar/min) Pr′ corrected rupture pressure (bar) Figure — Examples of hydrogen and helium corrected rupture pressures as a function of the pressure rise rate © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Key X pressure rise rate (bar/min) Z Pr He/Pr H2 hydro gen emb rittlement index ′ ′ Figure — Examples of the ratio Pr He/Pr H2 as a function of the pressure rise rate ′ ′ 5.2 Fracture mechanics test (method B) 5.2.1 This Principle of the test method s p e c i fie s a me tho d for the de term i nation o f the th re shold s tre s s fac tor i nten s ity K1H ) ( s u s cep tibi l ity to c racki ng o f me ta l l ic materi a l s i n gas e ou s hyd ro gen (or o ther embritl l i ng ga s e s) for The procedure covers the use of machined compact tension test pieces, as described in ISO 7539-6, for the de term i nation o f the th re shold s tre s s i nten s ity fac tor, as de s crib e d i n I S O 75 -1 T he te s t i nvolve s a s p e ci men contai n i ng a mach i ne d no tch T h i s no tch i s ex tende d b y fatigue c racki ng and then s ubj e c te d to an i ncrementa l ly i nc re a s i ng ten s i le lo ad du ri ng exp o s u re to a pre s s u ri s e d , ga s e ou s hyd ro gen envi ron ment T he obj e c tive is to qua nti fy the cond ition s u nder wh ich envi ron menta l ly- as s i s te d c rack prop agation c a n o cc u r If the specimens pass the test requirements, then the material is characterized as suitable for gas c yl i nders fi l le d with compre s s e d hyd ro gen NO TE T he te s t c a n be c a r rie d o ut with a ny o ther emb r ittl i n g ga s o r ga s T he accep ta nce c riter i a o f the s idere d ga s wi l l then b e de fi ne d s i m i l a rl y 5.2.2 5.2.2.1 m i x tu re (e g H S, hyd r ide s) Test procedure Specimen type T he te s t i nvolve s the u s e o f a comp ac t ten s ion (C T ) typ e s p e ci men, accord i ng to the ge ome tr y given in Figure (ISO 7539-6:2011, Figure 3), with a W dimension of 26 mm and B equal to the greatest th ickne s s a l lowe d by the c yl i nder wa l l c u r vatu re a nd th ickne s s , but no t le s s than % o f the de s ign th ickne s s o f the c yl i nder b ei ng qua l i fie d T he s p e c i men orientation ( Y-X ) relative to the c yl i nder a xi s i s shown in Figure 10 © ISO 2017 – All rights reserved ISO 11114-4:2017(E) At least three specimens taken 120° apart from the cylindrical wall shall be tested Flattening o f specimen blanks is not allowed I f the test specimen thickness cannot meet the validity requirements o f ISO 7539-6, then the thickest possible specimen as specified above shall be tested Dimensions in millimetres Surface roughness values in micrometres Key W net width C total width, 1,25 W minimum B thickness, 0,5 W H half height, 0,6 W D hole diameter, 0,25 W F half distance between hole outer edges, 1,6 D N notch width, 0,065 W maximum l effective notch length, 0,25 W to 0,40 W a e ffective crack length, 0,45 W to 0,55 W Figure — Proportional dimensions and tolerances for compact tension test pieces © ISO 2017 – All rights reserved 11 ISO 11114-4:2017(E) Figure — Test piece: type and orientation 5.2.2.2 Specimen preparation Prior to fatigue pre-cracking, all necessary electrical contacts and wires required for crack monitoring shall be attached to the specimen The specimen shall be thoroughly degreased, with particular attention paid to the notch tip region During all subsequent operations, especially the fatigue pre-crack, the specimen shall not be contaminated in order to ensure a clean crack front Fatigue pre-cracking shall be conducted to meet the general requirements detailed in ISO 7539-6:2011, Clause for the initiation and propagation o f fatigue cracks The final maximum pre-cracking load shall give a final maximum stress intensity lower than the initial stress intensity required for the test On completion o f fatigue pre-cracking, the specimen shall be measured as detailed in ISO 7539-6:2011, Clause to determine the thickness, B, width, W, and average length o f the fatigue pre-crack on the specimen sur faces The last o f these values shall be used in assessing the load necessary to produce the required initial stress intensity To prevent oxidation o f the crack tip, the specimen shall now be put on test I f, for any reason, this is not possible, the specimen shall be stored in a clean, desiccated environment until ready for testing 5.2.2.3 Gas purity and pressure The gas pressure in the test chamber shall be not less than the working pressure at which the cylinder needs to be evaluated In the case o f hydrogen, a purity o f at least 99,999 %, and O ≤ µl/l and H O ≤3 µl/l For other gases, the purity shall be equivalent to that of the gas being used This gas shall be covered by a batch certificate o f formity As an alternative, gas with a 99,999 % purity (O2 ≤ 0,1 µl/l and H O ≤ 0,5 µl/l) and covered by an individual certificate of formity may be used 5.2.2.4 Test apparatus The tests shall be conducted in a stainless steel chamber such as shown together with the loading bars and specimen in Figure 7, and installed on a servo-hydraulic test machine (Figure 8) 12 © ISO 2017 – All rights reserved ISO 11114-4:2017(E) Figure — Stainless steel chamber, showing loading bars and specimen Figure — Servo-hydraulic test machine After installation of the specimen, it is recommended that the test chamber be evacuated to a pressure f f f 5.2.2.3 o