ISO 15590-2:2021

Petroleum and natural gas industries - Factory bends, fittings and flanges for pipeline transportation systems - Part 2: Fittings

This document specifies the technical delivery conditions for unalloyed or low-alloy steel seamless and welded pipeline fittings for use in pipeline transportation systems for the petroleum and natural gas industries as defined in ISO 13623. This document is applicable to welding-end fittings such as elbows, caps, tees, single or multiple extruded headers, reducers, and transition sections made from seamless and welded pipe of unalloyed or low-alloy steels. This document specifies two classes of fitting one related to material used in non-sour service and one for material to be use in sour service environment as shown in Table 1. This document is not applicable to the selection of the fitting class. This document is not applicable to the materials for, or the attachment of, factory-welded extensions.

Industries du pétrole et du gaz naturel — Coudes d'usine, raccords et brides pour systèmes de transport par conduites — Partie 2: Raccords

General Information

• Status: Published
• Publication Date: 03-Aug-2021
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: ISO/TC 67/SC 2 - Pipeline transportation systems
• Drafting Committee: ISO/TC 67/SC 2/WG 10 - Pipeline flanges, fittings and shopbends
• Current Stage: 6060 - International Standard published
• Start Date: 04-Aug-2021
• Due Date: 11-Mar-2021
• Completion Date: 04-Aug-2021

Relations

• Revises: ISO 15590-2:2003 - Petroleum and natural gas industries - Induction bends, fittings and flanges for pipeline transportation systems - Part 2: Fittings
• Effective Date: 23-Apr-2020

Overview - ISO 15590-2:2021 (Fittings for pipeline transportation systems)

ISO 15590-2:2021 establishes the technical delivery conditions for unalloyed and low-alloy steel factory fittings used in pipeline transportation systems for the petroleum and natural gas industries (as defined in ISO 13623). It covers welding-end fittings made from seamless or welded pipe - for example elbows, caps, tees, reducers, transition sections and extruded headers - and defines two service classes: Class B (non‑sour service) and Class S (sour service). The standard does not choose the fitting class for a project nor apply to materials or attachments for factory‑welded extensions.

Key topics and technical requirements

• Scope and designation of fittings for pipeline use, aligned with ISO 13623.
• Pressure rating and design considerations (including specific treatment for tees).
• Information to be supplied by the purchaser, including dimensional, material and testing requirements.
• Manufacturing controls: manufacturing procedure specification (MPS), starting material, forming, welding, heat treatment and end preparation.
• Testing and inspection: extent of testing, chemical composition analysis, mechanical tests (tensile, Charpy V‑notch, hardness), metallography and specialized tests (HIC, SSC, CTOD, guided weld bend) where applicable.
• Non‑destructive testing (NDT): acceptance of ISO, EN and ASTM NDT methods - liquid penetrant, magnetic particle, radiography and automated ultrasonic testing for weld seams and bodies; personnel qualification per ISO 9712.
• Dimensional checks, gauging, hydrostatic testing, inspection documents and marking requirements.
• Normative annexes for design calculations and proof testing procedures.

Practical applications - who uses ISO 15590-2:2021

• Pipeline designers and engineers specifying fittings for oil and gas transmission systems.
• Fitting manufacturers and fabricators implementing MPS, welding and heat‑treatment controls.
• Procurement and QA/QC teams creating purchase orders and acceptance criteria.
• Inspection bodies and NDT technicians ensuring compliance with testing and marking rules.
• Operators and asset owners defining requirements for non‑sour vs sour service applications.

Related standards

Commonly used with:

• ISO 13623 (pipeline transportation systems)
• ISO 3183 (steel pipe for pipeline systems)
• ISO 3834-2 (welding quality requirements)
• ISO 10474, ISO 148-1, ISO 9606-1, ISO 9712 (inspection, testing and personnel qualifications)

ISO 15590-2:2021 is essential when specifying and verifying steel pipeline fittings for petroleum and natural gas projects, ensuring consistent manufacturing, testing and acceptance practices for both sour and non‑sour service environments.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 15590-2
Second edition
2021-08
Petroleum and natural gas
industries — Factory bends,
fittings and flanges for pipeline
transportation systems —
Part 2:
Fittings
Industries du pétrole et du gaz naturel — Coudes d'usine, raccords et
brides pour systèmes de transport par conduites —
Partie 2: Raccords
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 3
4 Symbols and abbreviated terms . 3
4.1 Symbols . 3
4.2 Abbreviated terms . 4
5 Designation of fittings . 5
6 Pressure rating and design . 5
6.1 General . 5
6.2 Tees . 5
7 Information to be supplied by the purchaser. 6
7.1 General information . 6
7.2 Additional information . 6
8 Manufacturing . 7
8.1 Manufacturing procedure specification . 7
8.2 Starting material . 7
8.3 Fitting manufacture . 7
8.3.1 Forming . 7
8.3.2 Welding . 8
8.3.3 Heat treatment. 8
8.3.4 End preparation . . . 8
9 Testing and inspection .10
9.1 General requirements .10
9.2 Extent of testing and inspection .11
9.3 Chemical composition .13
9.4 Mechanical testing .13
9.4.1 Preparation of test pieces.13
9.4.2 Tensile testing .13
9.4.3 Charpy V-notch impact testing .14
9.4.4 Through-thickness hardness testing .16
9.4.5 Surface hardness testing .17
9.4.6 Metallographic examination .17
9.4.7 HIC testing .17
9.4.8 SSC testing .17
9.4.9 CTOD testing .17
9.4.10 Guided weld bend testing .17
9.5 Non-destructive testing .18
9.5.1 NDT procedures and personnel .18
9.5.2 Condition of fittings .18
9.5.3 Treatment of imperfections . .18
9.5.4 Fitting ends .19
9.5.5 Weld seams .20
9.5.6 Guide bar attachment welds .20
9.5.7 Fitting body .20
9.5.8 Residual magnetism .20
9.6 Dimensions .20
9.7 Gauging .20
9.8 Hydrostatic testing .20
10 Inspection document .20
11 Marking .20
Annex A (normative) Design calculations .22
Annex B (normative) Proof test .24
Bibliography .27
iv © ISO 2021 – All rights reserved

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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore
structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline
transportation systems.
This second edition cancels and replaces the first edition (ISO 15590-2:2003), which has been
technically revised. The main changes compared to the previous edition are as follows:
a) changed title;
b) updated the list of applicable international standards with the latest applicable editions;
c) added the possibility to execute NDE following the ISO, EN and ASTM standards;
d) updated the assembly categories in only two types (sour service and non-sour service);
e) removed references to extruded headers (they are not accessories but special products);
f) modified the references to the final preparation, now in line with MSS SP-75 (Figure 1) and body
conical according to the ASME B16.9 criteria (Figure 3);
g) greater clarity on the sampling criteria (paragraph 9.2);
h) reviewed the chemical analysis to align with the ISO 3183 requirements (additional notes
concerning Pcm);
i) updated applicable standards relating to HIC and SSC;
j) modified paragraph relating to hydrotest;
k) applicability lighter than caliber (applicable only to tees);
l) added the range of qualifications of the “design proof test” in Clause B.5.
A list of all parts in the ISO 15590 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
vi © ISO 2021 – All rights reserved

Introduction
Further or differing requirements might be needed for individual applications. This document is
not intended to inhibit a manufacturer from offering, or the purchaser from accepting, alternative
equipment or engineering solutions for the individual application. This can be particularly applicable
where there is innovative or developing technology. Where an alternative is offered, the manufacturer
should identify any variations from this document and provide details.
INTERNATIONAL STANDARD ISO 15590-2:2021(E)
Petroleum and natural gas industries — Factory bends,
fittings and flanges for pipeline transportation systems —
Part 2:
Fittings
1 Scope
This document specifies the technical delivery conditions for unalloyed or low-alloy steel seamless and
welded pipeline fittings for use in pipeline transportation systems for the petroleum and natural gas
industries as defined in ISO 13623.
This document is applicable to welding-end fittings such as elbows, caps, tees, single or multiple
extruded headers, reducers, and transition sections made from seamless and welded pipe of unalloyed
or low-alloy steels.
This document specifies two classes of fitting one related to material used in non-sour service and one
for material to be use in sour service environment as shown in Table 1.
Table 1 — Fitting class and service
Fitting class Service
Class B NON-SOUR SERVICE
Class S SOUR SERVICE
This document is not applicable to the selection of the fitting class.
This document is not applicable to the materials for, or the attachment of, factory-welded extensions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 377, Steel and steel products — Location and preparation of samples and test pieces for mechanical
testing
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 6892-2, Metallic materials — Tensile testing — Part 2: Method of test at elevated temperature
ISO 2566-1, Steel — Conversion of elongation values — Part 1: Carbon and low alloy steels
ISO 3183, Petroleum and natural gas industries — Steel pipe for pipeline transportation systems
ISO 3834-2, Quality requirements for fusion welding of metallic materials — Part 2: Comprehensive quality
requirements
ISO 4885, Ferrous materials — Heat treatments — Vocabulary
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 7438, Metallic materials — Bend test
ISO/TS 7705:2017, Guidelines for specifying Charpy V-notch impact prescriptions in steel specifications
ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 10474, Steel and steel products — Inspection documents
ISO 10893-4, Non-destructive testing of steel tubes — Part 4: Liquid penetrant inspection of seamless and
welded steel tubes for the detection of surface imperfections
ISO 10893-5, Non-destructive testing of steel tubes — Part 5: Magnetic particle inspection of seamless and
welded ferromagnetic steel tubes for the detection of surface imperfections
ISO 10893-6, Non-destructive testing of steel tubes — Part 6: Radiographic testing of the weld seam of
welded steel tubes for the detection of imperfections
ISO 10893-8, Non-destructive testing of steel tubes — Part 8: Automated ultrasonic testing of seamless and
welded steel tubes for the detection of laminar imperfections
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 15614-1, Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys
EN 10204, Metallic components: Types of inspection documents
ASTM E112, Standard test methods for determining average grain size
ASTM E213, Standard Practice for Ultrasonic Testing of Metal Pipe and Tubing
ASTM A388, Standard Practice for Ultrasonic Examination of Steel Forgings
ASTM A578, Standard Specification for Straight-Beam Ultrasonic Examination of Rolled Steel Plates for
Special Applications
ASTM E165, Standard Practice for Liquid Penetrant Testing for General Industry
ASTM E709, Standard Guide for Magnetic Particle Testing
ASME BPVC Section V Nondestructive Examination
ASME BPVC Section VIII Rules for Construction of Pressure Vessels Division 1
ASME B16.9, Factory-made wrought butt welding fittings
ASME B31.8, Gas transmission and distribution piping systems
ASME B31.4Pipeline Transportation Systems for Liquids and NDTSlurries
ASME BPVC Section IX Welding, Brazing, and Fusing Qualifications
MSS SP-75, Specification for high test wrought butt welding fittings
NACE TM0177-2016-SG, Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress
Corrosion Cracking in H2S Environments
NACE TM0284-2016-SG, Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-
Induced CrackingTerms and definitions
2 © ISO 2021 – All rights reserved

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4885 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
by agreement
agreed between manufacturer and purchaser
3.2
extrados
outer curved section of the elbow
[SOURCE: ISO 15590-1:2018; 3.8, modified]
3.3
heat
batch of steel prepared in one steel-making process
[SOURCE: ISO 15590-1:2018; 3.9, modified]
3.4
intrados
inner curved section of the elbow
[SOURCE: ISO 15590-1:2018; 3.15, modified]
3.5
manufacturing procedure specification
MPS
document that specifies the process control parameters and the acceptance criteria to apply for all
manufacturing, inspection and testing activities performed during fitting manufacture
3.6
tangent
straight section at the ends of the fitting
[SOURCE: ISO 15590-1:2018; 3.25, modified]
3.7
test unit
fitting or test piece of the same type (tee, elbow, reducer or cap), starting material wall thickness, heat
(3.3), manufacturing procedure specification, and heat treatment condition
4 Symbols and abbreviated terms
4.1 Symbols
A original cross-sectional area of the parallel length of a tensile test specimen
o
D outside diameter
D outside diameter at the point under consideration, measured perpendicular to the longitu-
dinal axis
D outside diameter of the larger end of the reducer
L
D specified outside diameter of matching pipe
p
D minor outside diameter of a conical reducer or reducing tee at any point, n, under considera-
n
tion, measured perpendicular to the longitudinal axis
E factor used to calculate t (see A.1)
i
f factor used to calculate proof test pressure (see Table B.1)
P crack measurement parameter (see Table 4)
cm
p design pressure
p numerical value of the computed proof pressure
p
R tensile strength
m
R allowable tensile strength of a reducer
m, red
R yield strength for 0,5 % total elongation
t0,5
R specified minimum yield strength
smys
T minimum design temperature specified by the purchaser
d, min
t nominal wall thickness
t wall thickness of thicker component for joints of unequal thickness (see Figure 1)
D
t nominal wall thickness of the larger end of the reducer
DL
t minimum wall thickness required in the intrados
i
t nominal wall thickness of matching pipe
p
t specified wall thickness of reducers and reducing tees at diameter D
n n
α included angle of a reducer (eccentric, concentric or conical)
ρ radius of curvature of the external contoured portion of the outlet of a tee
o
4.2 Abbreviated terms
CE carbon equivalent (see Table 4)
CTOD crack tip opening displacement
DN nominal size
HIC hydrogen-induced cracking
HFW high-frequency electric welding process for pipe during manufacturing
MT magnetic particle testing
NDT non-destructive testing
PT liquid penetrant testing
4 © ISO 2021 – All rights reserved

PWHT post-weld heat treatment of the fitting
RT radiographic testing
SMYS specified minimum yield strength
SAWH submerged arc helical welding process for pipe during manufacture
SSC sulfide stress-cracking
UT ultrasonic testing
5 Designation of fittings
Designation of fittings, according to this document, i.e. ISO 15590-2, shall take the form:
ISO 15590-2 YY xxx-Z,
where
— YY is a textual description of the type of fitting, corresponding to one of the following: EL for elbow,
TE for tee, CA for cap, CR for concentric reducer, ER for eccentric reducer and NR for conical reducer,
preceded by the size designation (e.g. “DN 600 EL” is a DN 600 elbow);
— xxx is the specified minimum yield strength requirement in MPa;
— Z is the suffix B or S, B to identify the fitting class for use in non-sour service, or the suffix S to
identify the use in sour-service conditions.
6 Pressure rating and design
6.1 General
The capability of the fitting to withstand internal pressure shall equal or exceed that of the matching
pipe. The verification of the capability shall be made by calculation or proof testing. The calculations
shall be made in accordance with Annex A. The proof test procedure shall be as defined in Annex B.
Additional requirements on strength design verifications or different method of calculation, such as
resistance to internal pressure under special load cases in accordance with ISO 13623, ASME B31.8,
ASME B31.4 or other recognized international standards, shall be indicated at the time of enquiry or
order.
The design calculations and/or results of proof testing shall be available for review at the manufacturer’s
facility.
If the SMYS of the fitting material is less than that of the matching pipe, the minimum thickness of
the fitting end shall be increased such that the product of its thickness times its SMYS shall at least
equal the product of the specified wall thickness and the SMYS of the matching pipe, in accordance with
MSS SP-75.
6.2 Tees
Outlet branches in tees manufactured from seam-welded pipe shall be positioned diametrically opposite
the longitudinal weld. When this positioning is not possible, the location shall be decided by agreement.
The design and welding for the attachment of guide bars of barred tees shall be decided by agreement
prior to manufacture of the tee.
7 Information to be supplied by the purchaser
7.1 General information
The purchaser shall provide the following information in the order given below:
a) fitting designation;
b) required fitting dimensions, including:
— nominal wall thickness;
— radius and type of radius (e.g. long-radius);
— the angle (for elbows);
NOTE Guidance on specific dimensions to specify is given in ISO 3545-3.
c) whether the purchaser wishes to approve the MPS prior to commencement of manufacturing.
7.2 Additional information
If applicable, the purchaser shall specify the following supplementary information:
a) minimum design temperature;
b) maximum design temperature;
c) design conditions (design pressure, design factor, corrosion allowance and design code);
d) special dimensional requirements;
e) requirements for supplementary inspection and testing;
f) requirements for gauging and other measurements of dimensions where different from document;
g) mechanical property requirements at the maximum design temperature;
h) requirements for proof, burst, or hydrostatic testing;
i) activities for witnessing and approval by purchaser;
j) coating or painting requirements;
k) marking requirements where different from this document;
l) packaging and shipping instructions;
m) third-party inspection organization;
n) ISO 10474 or an equivalent regional standard, EN 10204, standard designation of inspection
document required;
o) requirements for format and additional content of the inspection document;
p) whether testing of welding procedures, welders, or welding operators specific to the order is
required;
q) whether approval of the MPS is to be by review of previous production data or by testing;
r) PWHT (see 9.1);
s) HIC testing (see 9.4.7);
6 © ISO 2021 – All rights reserved

t) SCC testing (see 9.4.8);
u) end-preparation details.
8 Manufacturing
8.1 Manufacturing procedure specification
Fittings shall be manufactured in accordance with a documented MPS. If specified by the purchaser,
manufacturing shall not proceed until the MPS has been accepted by the purchaser.
The MPS shall specify the following items (as appropriate):
a) for the starting material:
— name of manufacturer;
— steel-making process;
— steel grade;
— product form and dimensions;
— chemical composition, including that of the weld seam;
— welding procedure specification.
b) for fitting manufacture:
— forming procedure;
— welding procedure specification and approval record;
— heat treatment procedure including thermal cycles;
— machining requirements;
— inspection and test requirements;
— traceability.
c) additional requirements such as end preparation, coating, and marking.
An approval of the MPS might be required, either by review of the manufacturer’s previous production
data or by performance of the mandatory tests listed in Table 2, at the beginning of production.
8.2 Starting material
The starting material for fittings shall be blooms, billets, slabs, forging quality bar, plate, fusion-welded
with filler metal or seamless tubular products, produced from fully-killed steels; the chemical
composition shall conform to Table 4. Steel shall be produced by basic oxygen or electric arc furnace
process. Steel shall be made to fine grain practice.
HFW and SAWH pipes shall not be used.
8.3 Fitting manufacture
8.3.1 Forming
All forming operations shall be performed in accordance with the MPS.
8.3.2 Welding
Welding operations shall be conducted in accordance with those elements of ISO 3834-2 decided by
agreement and the requirements of this document.
Welding and repair welding shall be performed in accordance with procedures qualified in accordance
with ASME BPVC Section IX or ISO15614-1.
Welders and welding operators shall be qualified in accordance with ASME BPVC Section IX or
ISO 9606-1.
Acceptance criteria for all tests shall be as specified in Clause 9.
Where practicable, longitudinal butt welds should be double-sided. Backing rings shall not be used. All
welds shall have complete penetration and shall be finished in accordance with Clause 9.
Temporary welded attachments shall be removed, where possible, before heat treatment and the weld
area shall be treated in accordance with 9.5.3.4 and 9.5.3.5.
Fittings shall not contain girth welds.
All welds that will remain in the fitting shall be heat-treated in accordance with 8.3.3.
8.3.3 Heat treatment
All fittings shall be normalized, normalized and tempered, or quenched and tempered after welding
and/or forming. The heat treatment shall be performed in accordance with a documented procedure.
The procedure shall define the following parameters, where appropriate, for the type of heat treatment:
a) heating schedule;
b) soaking temperature;
c) soaking time;
d) cooling schedule;
e) quenching temperature;
f) quenching medium, including commencing and final medium temperature.
g) maximum transfer time to quench
A record shall be maintained of each heat treatment. Submission of heat treatment record shall be
specified at PO stage and it shall be included in the inspection document.
The tolerances on specified nominal values of soaking temperature and soaking time shall be ±15 °C
and +20 %, respectively.
8.3.4 End preparation
Unless otherwise specified, the details of the welding end preparation shall
...