oSIST prEN ISO 15589-2:2022

Petroleum, petrochemical and natural gas industries - Cathodic protection of pipeline transportation systems - Part 2: Offshore pipelines (ISO/DIS 15589-2:2021)

Erdöl- und Erdgasindustrie - Kathodischer Schutz für Transportleitungssysteme - Teil 2: Offshore-Pipelines (ISO/DIS 15589-2:2021)

Industries du pétrole, de la pétrochimie et du gaz naturel - Protection cathodique des systèmes de transport par conduites - Partie 2: Conduites en mer (ISO/DIS 15589-2:2021)

Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina - Katodna zaščita cevovodov - 2. del: Cevovodi na morju (ISO/DIS 15589-2:2021)

General Information

• Status: Not Published
• Public Enquiry End Date: 31-Jan-2022
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 98 - Abandoned project (Adopted Project)
• Start Date: 15-May-2024
• Due Date: 20-May-2024
• Completion Date: 15-May-2024
• Ref Project: prEN ISO 15589-2 - Petroleum and natural gas indurstries - Cathodic protection of pipeline transportation systems - Part 2: Offshore pipelines

Relations

• Revised: SIST EN ISO 15589-2:2014 - Petroleum, petrochemical and natural gas industries - Cathodic protection of pipeline transportation systems - Part 2: Offshore pipelines (ISO 15589-2:2012)
• Effective Date: 18-Jan-2023
• Revised: SIST EN ISO 15589-2:2014 - Petroleum, petrochemical and natural gas industries - Cathodic protection of pipeline transportation systems - Part 2: Offshore pipelines (ISO 15589-2:2012)
• Effective Date: 25-Dec-2019

Overview

prEN ISO 15589-2 / ISO/DIS 15589-2 addresses cathodic protection (CP) of offshore pipelines used in petroleum, petrochemical and natural gas industries. The available extract is a draft circulated for comment (ISO/DIS 15589-2:2021) and was adopted as a CEN draft (prEN ISO 15589-2). The full standard provides guidance on design, materials, manufacturing, installation, commissioning, operation and monitoring of CP systems specifically for submerged and offshore pipeline environments.

Keywords: ISO 15589-2, cathodic protection, offshore pipelines, pipeline corrosion, pipeline CP design

Key Topics

The standard covers technical requirements and practical guidance including:

• CP system requirements and selection

  • General principles and system selection considerations for offshore applications
  • Use of isolating joints and other system components

• Design parameters

  • Protection potential criteria and HISC (hydrogen‑induced stress cracking) evaluation for martensitic and duplex stainless steels
  • Design life and design current densities (including splash zone, buried sections, thermally sprayed aluminium coatings and elevated temperatures)
  • Coating breakdown factors and current drains

• Galvanic (sacrificial) anodes

  • Anode material selection, electrochemical properties, anode shapes and utilization factors
  • Mechanical, electrical and manufacturing requirements, plus quality control (chemical analysis, mass, dimensions, cracks, internal defects)

• Impressed-current CP systems

  • Current sources and controls, anode materials, system design, manufacturing and installation considerations

• Operation, monitoring and maintenance

  • Monitoring plans, commissioning procedures, documentation and maintenance/repair practices

• Normative and informative annexes

  • Design procedures, attenuation of protection, qualification testing of anode materials, CP monitoring and surveys, interference issues and pipeline design considerations for CP

Applications and Who Uses It

This standard is practical for:

• Corrosion and cathodic protection engineers designing offshore pipeline CP systems
• Pipeline operators and asset owners responsible for integrity management
• Fabrication and anode manufacturers ensuring compliant materials and production quality
• Installation contractors and survey teams performing commissioning and monitoring
• Regulators and inspectors assessing compliance and safety of offshore pipeline CP systems

Typical applications include selection and sizing of sacrificial anodes or impressed-current systems, setting protection potentials, creating monitoring and maintenance plans, and specifying manufacturing and testing requirements for anodes.

Related Standards

• ISO 15589-1 (Cathodic protection of pipeline transportation systems - Part 1: onshore pipelines) - companion document for onshore systems
• Other industry corrosion and CP standards (e.g., NACE/ISO guidance) are commonly used in conjunction with ISO 15589-2 for comprehensive integrity programs

Note: The extract provided is a draft; refer to the final published standard for authoritative requirements.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2022
Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina -
Katodna zaščita cevovodov - 2. del: Cevovodi na morju (ISO/DIS 15589-2:2021)
Petroleum, petrochemical and natural gas industries - Cathodic protection of pipeline
transportation systems - Part 2: Offshore pipelines (ISO/DIS 15589-2:2021)
Erdöl- und Erdgasindustrie - Kathodischer Schutz für Transportleitungssysteme - Teil 2:
Offshore-Pipelines (ISO/DIS 15589-2:2021)
Industries du pétrole, de la pétrochimie et du gaz naturel - Protection cathodique des
systèmes de transport par conduites - Partie 2: Conduites en mer (ISO/DIS 15589-
2:2021)
Ta slovenski standard je istoveten z: prEN ISO 15589-2
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT INTERNATIONAL STANDARD
ISO/DIS 15589-2
ISO/TC 67/SC 2 Secretariat: UNI
Voting begins on: Voting terminates on:
2021-11-19 2022-02-11
Petroleum, petrochemical and natural gas industries —
Cathodic protection of pipeline transportation systems —
Part 2:
Offshore pipelines
Industries du pétrole, de la pétrochimie et du gaz naturel — Protection cathodique des systèmes de
transport par conduites —
Partie 2: Conduites en mer
ICS: 75.200
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 15589-2:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2021

ISO/DIS 15589-2:2021(E)
© 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/DIS 15589-2:2021(E)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms.4
4.1 Symbols . 4
4.2 Abbreviated terms . 4
5 General . 5
5.1 Competence assurance . 5
5.2 Compliance . 5
6 Cathodic protection system requirements . 5
6.1 General . 5
6.2 Selection of CP systems. 6
6.2.1 General . 6
6.2.2 System selection considerations . 6
6.3 Isolating joints . 7
7 Design parameters .7
7.1 General . 7
7.2 Protection potentials . 9
7.2.1 Potential criteria . 9
7.2.2 HISC evaluation for martensitic and duplex stainless steel materials . 10
7.2.3 Thermally sprayed aluminium . 11
7.3 Design life . . 11
7.4 Design current densities for bare steel . 11
7.4.1 General . 11
7.4.2 Splash zone . 13
7.4.3 Buried pipelines .13
7.4.4 Thermally Sprayed Aluminum Coated Pipelines .13
7.4.5 Elevated temperatures . 13
7.4.6 Current drains .13
7.5 Coating breakdown factors . 14
8 Galvanic anodes .16
8.1 Design of system . 16
8.2 Selection of anode material . 17
8.3 Electrochemical properties . . 17
8.4 Anode shape and utilization factor . 18
8.5 Mechanical and electrical considerations . 19
9 Galvanic anode manufacturing .20
9.1 Pre-production test . 20
9.2 Coating . 20
9.3 Anode core materials . 20
9.4 Aluminium anode materials . 21
9.5 Zinc anode materials . 21
10 Galvanic anode quality control.22
10.1 General .22
10.2 Steel anode cores . 22
10.3 Chemical analysis of anode alloy . 22
10.4 Anode mass . 22
10.5 Anode dimensions and straightness . 22
iii
ISO/DIS 15589-2:2021(E)
10.5.1 Slender anodes . 22
10.5.2 Bracelet anodes . 22
10.6 Anode core dimensions and position . 23
10.7 Anode surface irregularities . 23
10.7.1 Slender anodes . 23
10.7.2 Bracelet anodes . 23
10.8 Cracks . 24
10.8.1 General . 24
10.8.2 Aluminium slender anodes. 24
10.8.3 Aluminium bracelet anodes . 24
10.9 Internal defects, destructive testing. 25
10.10 Electrochemical quality control testing . 25
11 Galvanic anode installation .26
12 Impressed-current CP systems .27
12.1 Current sources and control . 27
12.2 Impressed-current anode materials . 27
12.3 System design .28
12.4 Manufacturing and installation considerations .29
12.5 Mechanical and electrical considerations .29
13 Documentation .30
13.1 Design, manufacturing and installation documentation .30
13.2 Commissioning procedures . 30
13.3 Operating and maintenance manual . 31
14 Operation, monitoring and maintenance of CP systems .31
14.1 General . 31
14.2 Monitoring plans . . 31
14.3 Repair. 32
Annex A (normative) Galvanic anode CP design procedures .33
Annex B (normative) Attenuation of protection .40
Annex C (informative) Qualification testing of galvanic anode materials . 44
Annex D (normative) CP monitoring and surveys .45
Annex E (informative) Interference .52
Annex F (informative) Pipeline design for CP .54
Bibliography .60
iv
ISO/DIS 15589-2:2021(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 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15589-2 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offhore
structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline
transportation systems.
This third edition cancels and replaces the second edition (ISO 15589-2:2012), which has been
extensively revised, with the main changes as follows:
— In Clause 6 recommendations for isolating joints have been expanded.
— In Clause 7 Notes on Table 1 and text in Clause 7.4 have been updated to avoid discrepancies with
Figure 2. Coating breakdown factors have been revised for errors left in the previous edition and
less conservative values for some coating systems have been selected based on feedback from the
industry.
— In Clause 8 Notes and guidance on the design of the system have been updated including
recommendations for buried pipelines. Anode utilization factors have been expanded to cover
additional anodes types.
— In Clause 9, Table 6 has been updated to reflect anode compositions in line with current industry
practices and other standards.
— In Clause 10, additional references have been provided for guidance on core dimensions and position
as well as testing for quality control of anode electrochemical properties. .
— In Annex A, additional anode resistance equations have been provided to cover different anode
types. for the
— Annex B has been modified to present the NORSOK method as normative, while the alternative
method been made informative.
— Annex C has been updated as informative and the test method replaced with references to current
test methods in line with current industry practice.
— The previous Annex E has been removed and replaced by additional guidance on quality control
testing of anodes in Clause 10.10. .
— In the updated Annex E (Interference) additional references for alternating current interference
have been added.
A list of all parts in the ISO 15589 series can be found on the ISO website.
v
ISO/DIS 15589-2:2021(E)
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/DIS 15589-2:2021(E)
Introduction
The technical revision of this document has been carried out in order to accommodate the needs of
industry and to move this International Standard to a higher level of service within the petroleum,
petrochemical and natural gas industry.
Pipeline cathodic protection is achieved by the supply of sufficient direct current to the external pipe
surface, so that the steel-to-electrolyte potential is lowered on all the surface to values at which external
corrosion is reduced to an insignificant rate.
Cathodic protection is normally used in combination with a suitable protective coating system to
protect the external surfaces of steel pipelines from corrosion.
Users of this document should be aware that further or differing requirements may be needed for
individual applications. This document is not intended to prevent alternative equipment or engineering
solutions from being used for individual applications. This may be particularly applicable where there is
innovative or developing technology. Where an alternative is offered, it is intended that any variations
from this document be identified and documented.
This document can also be used for offshore pipelines outside the petroleum, petrochemical and natural
gas industries.
vii
DRAFT INTERNATIONAL STANDARD ISO/DIS 15589-2:2021(E)
Petroleum, petrochemical and natural gas industries —
Cathodic protection of pipeline transportation systems —
Part 2:
Offshore pipelines
1 Scope
This document specifies requirements and gives recommendations for the pre-installation surveys,
design, materials, equipment, fabrication, installation, commissioning, operation, inspection and
maintenance of cathodic protection (CP) systems for offshore pipelines for the petroleum, petrochemical
and natural gas industries as defined in ISO 13623. Hardware Subsea infrastructure used to aid in
the gathering of hydrocarbons, excluding pipelines, flowlines, risers and jumpers are not included in
ISO 15589 as they covered by different industry standards.
This document is applicable to carbon steel, stainless steel and flexible metallic pipelines in offshore
service.
This document is applicable to retrofits, modifications and repairs made to existing pipeline systems.
This document is applicable to all types of seawater and seabed environments encountered in
submerged conditions and on risers up to mean water level.
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 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test
methods
ISO 8044, Corrosion of metals and alloys — Vocabulary
ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates
and of steel substrates after overall removal of previous coatings
ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline
systems — Part 1: On-land pipelines
ISO 15607, Specification and qualification of welding procedures for metallic materials — General rules
ISO 18086, Corrosion of metals and alloys — Determination of AC corrosion — Protection criteria
1)
ASTM D1141, Standard Practice for the Preparation of Substitute Ocean Water
1) ASTM International , 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA.
ISO/DIS 15589-2:2021(E)
2)
AWS D1.1/D1.1M, Structural Welding Code — Steel
3)
EN 10025-(all parts), Hot rolled products of structural steels
EN 10204:2004, Metallic products — Types of inspection documents
NACE Publication 35110, AC Corrosion State-of-the-Art: Corrosion Rate, Mechanism, and Mitigation
Requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 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 https:// www .electropedia .org/
3.1
anode potential
anode-to-electrolyte potential
3.2
anode sled
anodes installed on a structure and connected to the pipeline by a cable
3.3
closed-circuit anode potential
anode potential while electrically linked to the pipeline to be protected
3.4
coating breakdown factor
f
c
ratio of current density required to polarize a coated steel surface as compared to a bare steel surface
3.5
cold shut
horizontal surface discontinuity caused by solidification of the meniscus of the partially cast anodes as
a result of interrupted flow of the casting stream
3.6
driving voltage
difference between the pipeline/electrolyte potential and the anode/electrolyte potential when the
cathodic protection is operating
3.7
electric field gradient
change in electrical potential per unit distance through a conductive medium, arising from the flow of
electric current
3.8
electrochemical capacity
ε
total amount of electric charge that is produced when a fixed mass (usually 1 kg) of anode material is
consumed electrochemically
Note 1 to entry: Electrochemical capacity is expressed in ampere hours.
2) American Welding Society, 550 NW Le Jeune Road, Miami, FL 33126, USA.
3) European Committee for Standardization, Rue de la Science 23, B-1040, Brussels, Belgium.
ISO/DIS 15589-2:2021(E)
3.9
final current density
estimated current density at the end of the lifetime of the pipeline
Note 1 to entry: Final current density is expressed in amperes per square metre.
3.10
hydrogen-induced stress cracking
HISC
cracking due to a combination of load and hydrogen embrittlement caused by the ingress of hydrogen
formed at the steel surface due to the cathodic polarization
3.11
IR drop
voltage due to any current, measured between two points of the metal of the pipe or two points of the
electrolyte, such as seawater or seabed, in accordance with Ohm’s law
Note 1 to entry: IR drop and electric field gradient are related terms.
3.12
Jumper
Rigid or flexible piping utilized to transport the pipe contents between manifolds, pipeline end
terminations/ manifolds and trees.
3.13
master reference electrode
reference electrode, calibrated with the primary calibration reference electrode, used for verification
of reference electrodes that are used for field or laboratory measurements
3.14
mean current density
estimated average cathodic current density for the entire lifetime of the pipeline
Note 1 to entry: Mean current density is expressed in amperes per square metre.
3.15
protection potential
structure-to-electrolyte potential for which the metal corrosion rate is considered as insignificant
3.16
pitting resistance equivalent number
PREN
number, developed to reflect and predict the pitting resistance of a stainless steel, based on the
proportions of Cr, Mo, W and N in the chemical composition of the alloy
3.17
primary calibration reference electrode
reference electrode used for calibration of master reference electrodes
3.18
remotely operated vehicle
ROV
underwater vehicle operated remotely from a surface vessel or installation
[SOURCE: ISO 14723:2009]
3.19
riser
part of an offshore pipeline, including any subsea spool pieces, which extends from the seabed to the
pipeline termination point on an offshore installation
[SOURCE: ISO 13623:2017]
ISO/DIS 15589-2:2021(E)
3.20
utilization factor
µ
fraction of the anodic material weight of a galvanic anode that can be consumed before the anode ceases
to provide the minimum required current output
4 Symbols and abbreviated terms
4.1 Symbols
ε electrochemical capacity
f coating breakdown factor
c
µ utilization factor
4.2 Abbreviated terms
CAT cold-applied tape
CE carbon equivalent
CP cathodic protection
CRA corrosion-resistant alloy
EPDM ethylene propylene diene monomer
FBE fusion-bonded epoxy
HISC hydrogen-induced stress cracking
HSS heat-shrinkable sleeve
PE polyethylene
PP polypropylene
PREN pitting resistance equivalent number
PU polyurethane
ROV remotely operated vehicle
SCE saturated calomel electrode
SMYS specified minimum yield strength
SRB sulphate reducing bacteria
3LPE three-layer polyethylene
3LPP three-layer polypropylene
ISO/DIS 15589-2:2021(E)
5 General
5.1 Competence assurance
Personnel who undertake the design, supervision of installation, commissioning, supervision of
operation, measurements, monitoring and supervision of maintenance of cathodic protection systems
shall have the appropriate level of competence for the tasks undertaken.
NOTE 1 EN 15257 or the NACE Cathodic Protection Training and Certification Programme constitute suitable
methods that can be used to assess competence of cathodic protection personnel.
NOTE 2 Competence of cathodic protection personnel to the appropriate level for tasks undertaken can be
demonstrated by certification in accordance with prequalification procedures such as EN 15257, the NACE
Cathodic Protection Training and Certification Programme or any other equivalent scheme.
5.2 Compliance
A quality system and an environmental management system should be applied to assist compliance
with the requirements of this part of ISO 15589.
NOTE ISO/TS 29001 gives sector-specific guidance on quality management systems and ISO 14001 gives
guidance on the selection and use of an environmental management system.
6 Cathodic protection system requirements
6.1 General
The CP system shall be designed to prevent external corrosion over the design life of the pipeline and
to:
— provide sufficient current to the pipeline to be protected and distribute this current so that the
selected criteria for CP are effectively attained on the entire surface;
— provide a design life of the anode system commensurate with the required life of the protected
pipeline, or to provide for periodic rehabilitation of the anode system;
— provide adequate allowance for anticipated changes in current requirements with time;
— ensure that anodes are installed where the possibility of disturbance or damage is minimal;
— provide adequate monitoring facilities to test and evaluate the system's performance.
The CP system shall be designed with due regard to environmental conditions and neighbouring
structures.
Electrical isolation of offshore pipelines protected by galvanic anodes from other pipelines, structures,
subsea facility or floaters that are protected by impressed-current systems shall be evaluated for
adverse interaction between the two systems. An assessment shall be performed to identify the
cathodic protection system of these facilities and review the electrical connectivity with the proposed
pipeline to ensure no detrimental effects on each side related to inadequate or excessive polarization.
Offshore pipelines shall be isolated from other unprotected or less protected structures, which could
drain current from the pipeline's CP system. If isolation is not practical or stray current problems are
suspected, electrical continuity should be ensured.
Care shall be taken to ensure that different CP systems of adjacent pipelines or structures are compatible
and that no excessive current drains from one system into an adjacent system.
The pipeline CP design shall take into account the pipeline installation method, the types of pipeline
and riser, and the burial and stabilization methods proposed. Further guidance is given in Annex F.
ISO/DIS 15589-2:2021(E)
The CP system based on galvanic anodes shall be designed for the lifetime of the pipeline system using
the calculation procedure given in Annex A.
For areas with high water velocities and areas with erosion effects (e.g. from entrained sand, silt, ice
particles), the design of the CP system needs special attention and additional design criteria shall be
considered.
Installation of permanent test facilities should be considered, taking into account specific parameters
such as pipeline length, water depth and underwater access related to the burial conditions.
ISO 15589-1 should be used for the cathodic protection of short lengths of offshore pipelines and their
branches that are directly connected to cathodically protected onshore pipelines.
6.2 Selection of CP systems
6.2.1 General
CP shall be achieved using either galvanic anodes or an impressed-current system. Galvanic anodes
shall be connected to the pipe, either individually or in groups
NOTE 1 Galvanic anodes are limited in current output by the anode-to-pipe driving voltage and the electrolyte
resistivity. Generally, anodes are attached directly to the pipe as bracelets. Sleds of anodes can also be placed at
regular intervals along the pipeline.
NOTE 2 Some pipelines can be protected by anodes located at each end. Typically, this type of installation
is used on inter-platform pipelines. Anodes for the pipeline can be attached to the platform if the pipeline is
electrically connected to the platform.
Items that shall be considered in selecting the system to be used are covered in 6.2.2.
6.2.2 System selection considerations
Selection of the CP system shall be based on the following considerations:
— magnitude of the protective current required;
— resistivity of the seawater;
— availability and location of suitable power sources for impressed-current systems;
— existence of any stray currents causing significant potential fluctuations between pipeline and
earth that can preclude the use of galvanic anodes;
— effects of any CP interference currents on adjacent structures that might limit the use of impressed-
current CP systems;
— limitations on the space available, due to the proximity of foreign structures, and related construction
and maintenance concerns;
— future development of the area and any anticipated future extensions to the pipeline system;
— cost of installation, operation and maintenance;
— reliability of the overall system;
— integrity of other pipelines and/or structures existing in the same area that could be affected by
impressed-current systems unless proper measures are taken to prevent these effects.
ISO/DIS 15589-2:2021(E)
NOTE Impressed-current systems can be preferred on short pipelines which terminate at platforms that
have impressed-current systems installed or where an impressed-current system is operated from the shore.
Impressed-current systems can also be preferred as a retrofit system on pipelines with galvanic anode failures,
excessive anode consumption, operation beyond original design life or excessive coating deterioration. Impressed
current can also be the preferred method for high-resistivity water.
6.3 Isolating joints
Isolating joints should be considered at the following locations:
— at connections to onshore pipelines or onshore receiving facilities;
— at connections to pipelines that require different protection criteria;
— between cathodically protected pipelines and non-protected facilities or less protected facilities;
— between pipeline systems (or structures) protected by impressed current and galvanic anodes.
— at connections between pipelines and appurtenances constructed from dissimilar metals (e.g
pumps and valves)
Electrical isolation of submarine pipelines from onshore electrical earthing systems is essential for
effective cathodic protection offshore and onshore. This isolation shall be provided using electrically
isolating joints.
Where offshore submarine pipeline CP is provided using galvanic anodes and onshore sections of
the pipeline are protected using either impressed current or galvanic anodes, electrical isolation is
necessary in order to enable the onshore section to be subject to the performance assessment as in
ISO 15589-1 Clause 6 which requires the measurement of IR Free pipe/soil potentials on the pipeline.
As current flowing to the onshore pipeline from offshore galvanic anodes cannot be interrupted, it is
necessary to electrically isolate the onshore pipeline from the offshore pipeline, in order to permit the
onshore pipeline CP system to be adequately performance assessed.
This isolation shall be provided using electrically isolating joints. These isolating joints are best located
at the landfall or on the seaward side of any emergency shut down valves, on the seaward side of any
electrical or control piping connections to the onshore pipeline, avoiding these short circuiting and
negating the effectiveness of the isolation joints.
NOTE 1 If these requirements for isolation joints are not followed, there is a considerable threat that cathodic
protection effectiveness will be severely impaired and that significantly costly remedial work will be necessary
in order to maintain pipeline integrity.
If isolating joints are used they shall be designed and installed to ensure long-term integrity and shall
be positioned to allow easy access for inspection and maintenance. Detailed design requirements are
given in ISO 15589-1 Clause 7.3.
NOTE 2 ISO 15589-1 clause 7.3.3. requires that monolithic or monobloc isolation joints should be used
wherever possible, for all electrical isolation requirements. Unless these joints are exposed to unplanned forces,
they have been shown to be much more reliable than the use of insulating gaskets, sleeves and washers in a
conventional flange. Due to the impact of isolation failure on pipeline integrity, monolithic or monobloc isolation
joints should be used at the interfaces between offshore and onshore pipelines.
7 Design parameters
7.1 General
The design of a pipeline CP system shall be based on:
— detailed information on the pipeline to be protected, including material, length, wall thickness,
outside diameter, pipe-laying procedures, route, laying conditions on the sea bottom, temperature
profile (operating and shut in) along its whole length, type and thickness of corrosion-protective
ISO/DIS 15589-2:2021(E)
coating(s) for pipes and fittings, presence, type and thickness of thermal insulation, mechanical
protection and/or weight coating;
— environmental conditions, including diurnal and seasonal variations, such as seawater salinity,
temperature and resistivity, tides and seabed resistivity along the whole length of the pipeline;
— burial status (extent of backfilling after trenching or natural burial) and soil resistivity;
— design life of the system;
— information on existing pipelines in close proximity to or crossing the new pipeline, including
location, ownership and corrosion-control practices;
— information on existing CP systems (platforms, landfalls, subsea structures, etc.) and electrical
pipeline isolation;
— availability of electrical power, electrical isolating devices, electrical bonds;
— applicable local legislation;
— construction dates, start-up date (required for hot lines);
— presence of fittings, J-tubes, risers, clamps, wyes, tees and other appurtenances; and
— performance data on CP systems in the same environment.
If CP performance data for similar environments is not available (for example when moving into deeper
water), data on the seawater characteristics (dissolved oxygen, salinity, pH, sea currents, and fouling)
shall be obtained as these can affect cathodic polarization and calcareous deposit formation. For these
situations, the required information shall be obtained from field surveys and/or corrosion test data
including the following:
— protective current requirements to meet applicable criteria;
— electrical resistivity of the electrolyte, including seasonal changes if relevant;
— pipe burial depth (if buried) and identification of exposed span lengths and locations;
— water temperature at the seabed;
— oxygen concentration at the seabed;
— water flow rate at the seabed, including seasonal changes if relevant;
— seabed topography.
When reviewing operating experience, the following additional data should be considered:
— electrical continuity;
— electrical isolation;
— external coating integrity;
— deviation from specifications;
— maintenance and operating data.
Design procedures for the CP based on galvanic anode systems shall be in accordance with Annex A.
oSI
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