SIST EN ISO 17945:2015

SLOVENSKI STANDARD
01-julij-2015
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Petroleum, petrochemical and natural gas industries - Metallic materials resistant to
sulfide stress cracking in corrosive petroleum refining environments (ISO 17945:2015)
Erdöl-, petrochemische und Erdgasindustrie - Metallische Werkstoffe beständig gegen
Schwefelwasserstoff-Rissbildung in korrosiver Erdölraffinerieumgebung (ISO
17945:2015)
Industries du pétrole, de la pétrochimie et du gaz naturel - Matériaux métalliques
résistant à la fissuration sous contrainte induite par les sulfures pour utilisation dans des
environnements corrosifs de raffinage du pétrole (ISO/FDIS 17945:2014)
Ta slovenski standard je istoveten z: EN ISO 17945:2015
ICS:
75.180.10 Oprema za raziskovanje in Exploratory and extraction
odkopavanje equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 17945
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2015
ICS 75.180.10
English Version
Petroleum, petrochemical and natural gas industries - Metallic
materials resistant to sulfide stress cracking in corrosive
petroleum refining environments (ISO 17945:2015)
Industries du pétrole, de la pétrochimie et du gaz naturel - Erdöl-, petrochemische und Erdgasindustrie - Metallische
Matériaux métalliques résistant à la fissuration sous Werkstoffe beständig gegen Schwefelwasserstoff-
contrainte induite par les sulfures pour utilisation dans des Rissbildung in korrosiver Erdölraffinerieumgebung (ISO
environnements corrosifs de raffinage du pétrole (ISO 17945:2015)
17945:2015)
This European Standard was approved by CEN on 7 February 2015.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17945:2015 E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 17945:2015) has been prepared by Technical Committee ISO/TC 67 “Materials,
equipment and offshore structures for petroleum, petrochemical and natural gas industries” in collaboration
with Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for petroleum,
petrochemical and natural gas industries” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2015, and conflicting national standards shall be withdrawn at
the latest by October 2015.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 17945:2015 has been approved by CEN as EN ISO 17945:2015 without any modification.
INTERNATIONAL ISO
STANDARD 17945
First edition
2015-04-15
Petroleum, petrochemical and
natural gas industries — Metallic
materials resistant to sulfide stress
cracking in corrosive petroleum
refining environments
Industries du pétrole, de la pétrochimie et du gaz naturel —
Matériaux métalliques résistant à la fissuration sous contrainte
induite par les sulfures pour utilisation dans des environnements
corrosifs de raffinage du pétrole
Reference number
ISO 17945:2015(E)
©
ISO 2015
ISO 17945:2015(E)
© ISO 2015
All rights reserved. Unless otherwise specified, no part of 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 of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2015 – All rights reserved

ISO 17945:2015(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Responsibilities . 3
5.1 Responsibilities of the end user . 3
5.2 Responsibility of the manufacturer . 4
6 Factors contributing to SSC . 4
6.1 General parameters affecting SSC . 4
6.2 Effect of material condition and stress level on susceptibility to SSC . 4
6.3 Effect of hydrogen permeation flux on SSC . 5
6.4 Effect of elevated temperature exposure on SSC . 5
6.5 Factors affecting time to failure due to SSC . 6
6.6 Bases for establishing whether equipment falls within the scope of this
International Standard . 6
7 Materials included in this International Standard . 6
8 Hardness requirements . 7
9 Procedure for the addition of new materials or processes . 8
9.1 General balloting requirements . 8
9.2 Field experience data requirements . . 8
9.3 Laboratory test data requirements . 8
10 New restrictions and deleted materials . 8
11 Qualification of unlisted alloys, conditions, and/or processes for specific applications .9
12 Standard road map . 9
13 Ferrous materials .11
13.1 Carbon and alloy steels .11
13.1.1 Requirements for all carbon and alloy steels .11
13.1.2 Requirements for carbon steels listed as P-No. 1 Group 1 or 2 in Section IX
of the ASME BPVC .11
13.1.3 Requirements for other carbon steels .11
13.1.4 Requirements for alloy steels listed with P-numbers in Section IX of the
ASME BPVC .12
13.1.5 Requirements for other alloy steels .12
13.1.6 Requirements for cold-formed carbon and alloy steels .12
13.1.7 Welding requirements for carbon steels listed as P-No. 1 in Section IX of
the ASME BPVC .12
13.1.8 Welding requirements for alloy steels listed as P-No. 3, 4, or 5A in Section
IX of the ASME BPVC .13
13.1.9 Corrosion resistant weld overlays, hard facing weld overlays, cladding,
and thermal spray coatings on carbon steels and alloy steels .13
13.2 Cast iron and ductile iron .13
13.3 Ferritic stainless steels .14
13.4 Martensitic stainless steels .14
13.4.1 Conventional martensitic stainless steels .14
13.4.2 Low-carbon martensitic stainless steels .14
13.4.3 Welding and overlays on martensitic stainless steels .15
13.5 Austenitic stainless steels .15
ISO 17945:2015(E)
13.6 Specific austenitic stainless steel grades .16
13.7 Highly alloyed austenitic stainless steels .16
13.8 Duplex stainless steels.16
13.8.1 General requirements for duplex stainless steels .16
13.8.2 Welding requirements for duplex stainless steels .17
13.9 Precipitation-hardenable stainless steels .17
13.9.1 Austenitic precipitation-hardenable stainless steel .17
13.9.2 Martensitic precipitation-hardenable stainless steels .17
13.9.3 Welding requirements for precipitation-hardenable stainless steels .18
14 Nonferrous materials .19
14.1 Nickel alloys .19
14.1.1 Solid-solution nickel alloys .19
14.1.2 Precipitation-hardenable nickel alloys .20
14.2 Cobalt-Nickel-chromium-molybdenum alloys .20
14.3 Cobalt-nickel-chromium-tungsten alloys .21
14.4 Titanium alloys .21
14.5 Aluminium alloys .22
14.6 Copper alloys .22
15 Fabrication requirements .22
15.1 General fabrication requirements .22
15.2 Corrosion resistant overlays, hard facing overlays, and cladding .22
15.3 Welding .22
15.4 Cladding on carbon steels, alloy steels, and martensitic stainless steels .23
15.5 Identification stamping .23
15.6 Threading .24
15.6.1 Machine-cut threads .24
15.6.2 Cold-formed (rolled) threads .24
15.7 Cold-deformation processes .24
16 Bolting .24
16.1 General bolting requirements .24
16.2 Exposed bolting .24
16.3 Nonexposed bolting .25
17 Plating, coatings, and diffusion processes .25
18 Special components .25
18.1 General requirements for special components .25
18.2 Bearings .25
18.3 Springs .26
18.4 Instrumentation and control devices .26
18.4.1 General requirements for instrumentation and control devices .26
18.4.2 Diaphragms, pressure-measuring devices, and pressure seals .26
18.5 Seal rings and gaskets .26
18.6 Snap Rings .27
18.7 Special process parts .27
19 Valves .27
20 Compressors and pumps .27
Annex A (informative) Sulfide species plot .29
Annex B (informative) Background information on hardness testing and requirements .30
Annex C (normative) Welding procedure qualification hardness survey layouts .34
Bibliography .43
iv © ISO 2015 – All rights reserved

ISO 17945:2015(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of any
patent rights identified during the development of 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 information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries.
ISO 17945:2015(E)
Introduction
The term “wet H S cracking”, as used in the refining industry, covers a range of damage mechanisms
that can occur because of the effects of hydrogen charging in wet H S refinery or gas plant process
environments. One of the types of material damage that can occur as a result of hydrogen charging
is sulfide stress cracking (SSC) of hard weldments and microstructures, which is addressed by this
International Standard. Other types of material damage include hydrogen blistering, hydrogen-induced
cracking (HIC), and stress-oriented hydrogen-induced cracking (SOHIC), which are not addressed by
this International Standard.
Historically, many end users, industry organizations (e.g. API), and manufacturers that have specified
and supplied equipment and products such as rotating equipment and valves to the refining industry
have used NACE MR0175/ISO 15156 to establish materials requirements to prevent SSC. However, it has
always been recognized that refining environments are outside the scope of NACE MR0175/ISO 15156,
which was developed specifically for the oil and gas production industry. In 2003, the first edition
of NACE MR0103 was published as a refinery-specific sour service metallic materials standard. This
International Standard is based on the good experience gained with NACE MR0175/ISO 15156, but
tailored to refinery environments and applications. Other references for this International Standard are
NACE SP0296, NACE Publication 8X194, NACE Publication 8X294, and the refining experience of the task
group members who developed NACE MR0103.
The materials, heat treatments, and material property requirements set forth in NACE MR0103
are based on extensive experience in the oil and gas production industry, as documented in NACE
MR0175/ISO 15156, and were deemed relevant to the refining industry by the task group.
This International Standard was developed on the basis of NACE MR0103.
vi © ISO 2015 – All rights reserved

INTERNATIONAL STANDARD ISO 17945:2015(E)
Petroleum, petrochemical and natural gas industries —
Metallic materials resistant to sulfide stress cracking in
corrosive petroleum refining environments
1 Scope
This International Standard establishes material requirements for resistance to SSC in sour petroleum
refining and related processing environments containing H S either as a gas or dissolved in an aqueous
(liquid water) phase with or without the presence of hydrocarbon. This International Standard does
not include and is not intended to include design specifications. Other forms of wet H S cracking,
environmental cracking, corrosion, and other modes of failure are outside the scope of this International
Standard. It is intended to be used by refiners, equipment manufacturers, engineering contractors, and
construction contractors.
Specifically, this International Standard is directed at the prevention of SSC of equipment (including
pressure vessels, heat exchangers, piping, valve bodies, and pump and compressor cases) and components
used in the refining industry. Prevention of SSC in carbon steel categorized under P-No. 1 in Section IX of the
ASME Boiler and Pressure Vessel Code (BPVC) is addressed by requiring compliance with NACE SP0472.
This International Standard applies to all components of equipment exposed to sour refinery
environments (see Clause 6) where failure by SSC would (1) compromise the integrity of the pressure-
containment system, (2) prevent the basic function of the equipment, and/or (3) prevent the equipment
from being restored to an operating condition while continuing to contain pressure.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NACE Standard TM0177, Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress
1)
Corrosion Cracking in H2S Environments
ANSI/NACE MR0175/ISO 15156, Petroleum and natural gas industries — Materials for use in H2S-
1)
containing environments in oil and gas production
ASTM A833, Standard Practice for Indentation Hardness of Metallic Materials by Comparison Hardness Testers
ASTM E384, Standard Test Method for Knoop and Vickers Hardness of Materials
ASTM E562, Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count
SAE AMS2430, Shot Peening, Automatic
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
lower transformation temperature
A
c1
temperature at which austenite begins to form during heating
1) NACE International, 1440 South Creek Dr., Houston, TX 77084-4906, USA.
ISO 17945:2015(E)
3.2
upper transformation temperature
A
c3
temperature at which transformation of ferrite to austenite is completed during heating
3.3
alloy steel
iron-based alloy containing carbon (usually less than 2,5 %) and manganese (usually not less than
0,25 %), that contains specified minimum quantities for one or more alloying elements other than
manganese, silicon, and copper, and that does not specify a minimum chromium content greater than or
equal to 10 %
3.4
austenitic stainless steel
stainless steel whose microstructure, at room temperature, consists predominantly of austenite
3.5
carbon steel
iron-based alloy containing carbon (usually less than 2,0 %) and manganese (usually not less than
0,25 %), with no specified minimum quantity for any alloying element other than manganese, silicon,
and copper, and that contains only an incidental amount of any element other than carbon, silicon,
manganese, copper, sulfur, and phosphorus
3.6
cladding
metallurgically bonded layer (roll bonded, explosion bonded, or weld overlaid) of a corrosion-resistant alloy
material applied to the entire wetted surface of a substrate material that is relatively less corrosion-resistant
Note 1 to entry: See also weld overlay.
3.7
duplex stainless steel
austenitic/ferritic stainless steel
stainless steel whose microstructure at room temperature consists primarily of a mixture of
austenite and ferrite
3.8
end user
company or agency that owns and operates the component (e.g. vessel, piping, pump, compressor, etc.)
3.9
ferritic stainless steel
stainless steel whose microstructure, at room temperature, consists predominantly of ferrite
3.10
stainless steel
iron-based alloy containing 10,5 % mass fraction or more chromium, possibly with other elements
added to secure special properties
3.11
sulfide stress cracking
SSC
cracking of a metal under the combined action of tensile stress and corrosion in the presence of water
and H S (a form of hydrogen stress cracking)
3.12
thermal spray coating
high-temperature process by which finely divided metallic or nonmetallic materials are deposited in a
molten or semi-molten condition to form a coating on a surface when cooled
2 © ISO 2015 – All rights reserved

ISO 17945:2015(E)
3.13
weld overlay, corrosion resistant
deposition of one or more layers of corrosion resistant weld metal to the surface of a base material in an
effort to improve the corrosion resistance properties of the surface
Note 1 to entry: See also cladding.
3.14
weld overlay, hard facing
deposition of one or more layers of a weld metal to the surface of a material in an effort to improve the
wear resistance properties of the surface
4 Symbols and abbreviated terms
ANSI American National Standards Institute
API American Petroleum Institute
ASME ASME (formerly American Society of Mechanical Engineers)
AWS American Welding Society
BPVC boiler and pressure vessel code
HAZ heat-affected zone
HI heat input
HIC hydrogen-induced cracking
NACE NACE International (formerly National Association of Corrosion Engineers)
ppmw parts per million by weight, commonly expressed as mg/kg in SI units
PQR procedure qualification record
PREN pitting resistance equivalent number
PWHT postweld heat treatment
SOHIC stress-oriented hydrogen-induced cracking
SSC sulfide stress cracking
UNS unified numbering system (for metals and alloys)
WPQT welding procedure qualification test
5 Responsibilities
5.1 Responsibilities of the end user
5.1.1 It is the responsibility of the end user (or the end user’s agent) to determine the operating
conditions and to specify when this International Standard applies.
5.1.2 It is the end user’s (or the end user’s agent’s) responsibility to ensure that a material is satisfactory
in the intended environment. The end user (or the end user’s agent) may select specific materials for
use on the basis of operating conditions that include pressure, temperature, corrosiveness, and fluid
ISO 17945:2015(E)
properties. A variety of candidate materials may be selected from this International Standard for any
given component. Unlisted materials may also be used based on either of the following processes.
a) If a metallurgical review based on scientific and/or empirical knowledge indicates that the SSC
resistance will be adequate, these materials may then be proposed for inclusion into the standard
using methods in Clause 9.
b) If a risk-based analysis indicates that the occurrence of SSC is acceptable in the subject application.
5.1.3 Other forms of wet H S cracking, environmental cracking, corrosion, and other modes of failure,
although outside the scope of this International Standard, should be considered in the design and
operation of equipment. Severely corrosive and/or hydrogen charging conditions may lead to failures
by mechanisms other than SSC and should be mitigated by methods that are outside the scope of this
International Standard.
5.2 Responsibility of the manufacturer
The manufacturer is responsible for meeting the metallurgical requirements of this International Standard.
6 Factors contributing to SSC
6.1 General parameters affecting SSC
SSC in refining equipment is affected by complex interactions of parameters including the following:
a) chemical composition, strength (as indicated by hardness), heat treatment, and microstructure of
the material exposed to the sour environment;
b) total tensile stress present in the material (applied plus residual);
c) hydrogen flux generated in the material, which is a function of the environment (i.e. presence of an
aqueous phase, H S concentration, pH, and other environmental parameters such as bisulfide ion
concentration and presence of free cyanides);
d) temperature;
e) time.
6.2 Effect of material condition and stress level on susceptibility to SSC
6.2.1 Material susceptibility to SSC is primarily related to material strength (as indicated by hardness),
which is affected by chemical composition, heat treatment, and microstructure. Materials with high
hardness generally have an increased susceptibility to SSC.
6.2.2 SSC has not generally been a concern for carbon steels typically used for refinery pressure vessels
and piping in wet H S service because these steels have sufficiently low hardness levels.
6.2.3 Improperly heat-treated metals, weld deposits, and heat-affected zones (HAZ), however, may
contain regions of high hardness.
6.2.4 Susceptibility for a given material increases with increased tensile stress.
6.2.5 Residual stresses contribute to the overall tensile stress level. High residual stresses associated
with welds increase susceptibility to SSC.
4 © ISO 2015 – All rights reserved

ISO 17945:2015(E)
6.2.6 Control of weldment hardness, with or without reduction of residual stresses, is a recognized
method for preventing SSC, as outlined in NACE SP0472 for P-No. 1 carbon steels.
6.3 Effect of hydrogen permeation flux on SSC
6.3.1 Susceptibility to SSC is also related to the hydrogen permeation flux in the steel, which is primarily
associated with two environmental parameters: pH and total sulfide content of the aqueous phase. In
–
a closed system at equilibrium condition, dissolved hydrogen sulfide (H S ), bisulfide ion (HS ), and
2 aq
2–
sulfide ion (S ) (sometimes called “soluble sulfide”) exist in an aqueous solution in different pH ranges.
6.3.2 The sulfide species plot exhibited in Figure A.1 shows their relative amounts present in an aqueous
solution at 25 C (77°F) as a function of pH. At pH less than 6, H S is the dominant (>90 % of total) sulfide
2 aq
specie present in the aqueous phase. At pH between 8 and 11, the dominant (>90 % of total) sulfide specie
–
present in the aqueous phase is HS . At pH greater than 13, the dominant (>90 % of total) sulfide specie
2– –
present in the aqueous phase is S . At pH 7, the system contains 50 % H S , 50 % HS , and virtually no
2 aq
2– – 2–
S . At pH 12, the system contains 50 % HS , 50 % S , and virtually no H S . The total sulfide content,
2 aq
therefore, refers to the total amount of all three sulfide species present in the aqueous phase (i.e. the sum
– 2–
of H S , HS , and S ).
2 aq
6.3.3 Typically, the hydrogen flux in steels has been found to be lowest in near-neutral pH solutions,
with increasing flux at both lower and higher pH values. Corrosion at lower pH values is typically caused
–
by H S , whereas corrosion at higher pH values is typically caused by high concentrations of HS .
2 aq
6.3.4 In many refinery sour water environments, the presence of dissolved ammonia (NH ) increases
–
the pH, thereby increasing the solubility of H S and resulting in a high HS concentration. At elevated
pH, the presence of free cyanides, which include dissolved hydrogen cyanide (HCN ) and cyanide ion
aq
–
(CN ), can further aggravate the degree of atomic hydrogen charging into the steel. Even though SSC
susceptibility is known to increase with total sulfide content of the aqueous phase, the presence of as little
as 1 ppmw total sulfide in the aqueous phase can cause SSC under conditions that promote aggressive
hydrogen charging.
6.3.5 For carbon steel, some environmental conditions known to cause SSC are those containing an
aqueous (liquid water) phase and either of the following:
a) >50 ppmw total sulfide content in the aqueous phase;
b) ≥1 ppmw total sulfide content in the aqueous phase and pH < 4;
c) ≥1 ppmw total sulfide content and ≥20 ppmw free cyanide in the aqueous phase, and pH > 7,6;
d) >0,3 kPa absolute (0,05 psia) partial pressure H S in the gas phase associated with the aqueous
phase of a process.
6.3.6 The high-pH sour environments differentiate refinery sour service from the oil and gas production
sour environments covered by NACE MR0175/ISO 15156, because many wet sour streams in oil and gas
production also contain carbon dioxide and, hence, exhibit a lower pH. Another major difference is that
chloride ion concentrations tend to be significantly lower in refinery sour services than in oil production
sour services.
6.4 Effect of elevated temperature exposure on SSC
The hydrogen charging potential increases with increasing temperature provided the aqueous
phase is not eliminated by the elevated temperature. Elevated temperature promotes dissociation of
H S (thereby producing more monatomic hydrogen), and increases the diffusion rates of monatomic
hydrogen in metals, thereby promoting hydrogen charging. However, cracking potential is maximized
at near-ambient temperature. This distinction is important because metals can become charged during
ISO 17945:2015(E)
high-temperature exposure and subsequently crack during excursions to lower temperatures (such as
during shutdowns).
6.5 Factors affecting time to failure due to SSC
The time to failure decreases as material strength, total tensile stress, and environmental charging
potential increase. Exposure time to cause SSC can be very short, if the other SSC factors favour
susceptibility. Some susceptible equipment can fail even during short sour water excursions such as
those encountered during equipment shutdowns.
6.6 Bases for establishing whether equipment falls within the scope of this
International Standard
The end user (or the end user’s agent) shall determine whether the parameters necessary to cause SSC
exist in the process environment, and whether the equipment falls within the scope of this International
Standard. The end user (or the end user’s agent) may rely on experience, risk-based analysis, or the
above guidance (notably that related to environmental conditions provided in 6.3 and 6.4) to make this
determination. When determining whether the equipment falls within the scope of this International
Standard, consideration should be given to all plant operating scenarios and the likely impact on the
materials of construction, i.e. normal operations, operational upsets, alternate (possible future)
operations, and start-up/shutdown conditions (e.g. presulfiding of catalysts).
7 Materials included in this International Standard
7.1 Materials included in this International Standard are resistant to, but not necessarily immune to,
SSC. Materials have been included based on their demonstrated resistance to SSC in field applications, in
SSC laboratory testing, or both.
7.2 Listed materials do not all exhibit the same level of resistance to SSC. Standard laboratory SSC
tests, such as those addressed in NACE Standard TM0177, are accelerated and severe tests. Materials that
successfully pass these tests are generally more resistant to cracking in sour service than materials that
fail the tests. Many alloys included in this International Standard perform satisfactorily in sour service
even though they may crack in laboratory tests.
7.3 Improper design, processing, installation, or handling can cause resistant materials to become
susceptible to SSC.
7.4 No effort has been made in this International Standard to rank materials based on their relative
resistance to SSC. Selection of the appropriate material for a given application depends on a number
of factors, including mechanical properties, corrosion resistance, and relative resistance to SSC, and is
beyond the scope of this International Standard.
7.5 There are a number of instances where this International Standard specifically references the
ASME BPVC. There are other instances where this In
...