RECOMMENDED PRACTICE
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DNV-RP-F103
CATHODIC PROTECTION OF SUBMARINE PIPELINES BY
GALVANIC ANODES
OCTOBER 2003
Since issued in print (October 2003), this booklet has been amended, latest in April 2006.
See the reference to “Amendments and Corrections” on the next page.
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FOREWORD
DET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life, prop-erty and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification and consultancy services relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out research in relation to these functions.
DNV Offshore Codes consist of a three level hierarchy of documents:
—Offshore Service Specifications. Provide principles and procedures of DNV classification, certification, verification and con-sultancy services.
—Offshore Standards. Provide technical provisions and acceptance criteria for general use by the offshore industry as well as
the technical basis for DNV offshore services.
—Recommended Practices. Provide proven technology and sound engineering practice as well as guidance for the higher level
Offshore Service Specifications and Offshore Standards.DNV Offshore Codes are offered within the following areas:A)Qualification, Quality and Safety Methodology B)Materials Technology C)Structures D)Systems
E)Special Facilities F)Pipelines and Risers G)Asset Operation H)Marine Operations J)Wind Turbines
Amendments and Corrections
This document is valid until superseded by a new revision. Minor amendments and corrections will be published in a separate document normally updated twice per year (April and October).
For a complete listing of the changes, see the “Amendments and Corrections” document located at: www.dnv/technologyservices/, “Offshore Rules & Standards”, “Viewing Area”.
The electronic web-versions of the DNV Offshore Codes will be regularly updated to include these amendments and corrections.
Amended April 2006,Recommended Practice DNV-RP-F103,  October 2003 see note on front cover Page 3
CONTENTS
1.GENERAL (5)
1.1Introduction (5)
1.2Scope (5)
1.3Objectives and use (6)
1.4Structure of document (6)
1.5Relation to DNV-OS-F101 and other DNV
documents on pipeline corrosion control (6)
2.REFERENCES (7)
2.1DNV (Det Norske Veritas) (7)
2.2EN (European Standards) (7)
2.3ISO (International Organisation for
Standardization) (7)
3.TERMINOLOGY AND DEFINITIONS (7)
4.ABBREVIATIONS AND SYMBOLS (7)
4.1Abbreviations (7)
4.2Symbols for CP design parameters (7)
5.CATHODIC PROTECTION DETAILED
DESIGN (8)
5.1General (8)
5.2Calculation of mean current demand for
cathodic protection (8)
5.3Calculation of Final Current Demand for
Cathodic Protection (9)
5.4Calculation of total anode net mass to
meet mean current demand (9)
5.5Calculation of total anode current output to
meet final current demand (10)
5.6Distribution of anodes (10)
5.7Documentation of completed CP
detailed design (12)
6.ANODE MANUFACTURING (12)
6.1General (12)
6.2Manufacturing procedure specification (12)
6.3Pre-production qualification testing (PQT) (13)
submarine6.4Quality control of production (13)
6.5Materials and casting (13)
6.6Inspection and testing of anodes (13)
6.7Documentation and marking (14)
6.8Handling, storage and shipping of anodes (14)
7.ANODE INSTALLATION (14)
7.1Design of anode attachment (14)
7.2Installation procedure specification (14)
7.3Pre-production qualification testing (PQT) (15)
7.4Quality control during production (15)
7.5Receipt and handling of anodes and materials for
installation (15)
7.6Anode installation (15)
7.7Inspection and testing of anode installation (15)
7.8Documentation (15)
8.ANNEX 1  RECOMMENDATIONS FOR
COATING BREAKDOWN FACTORS (16)
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Recommended Practice DNV-RP-F103,  October 2003Amended April 2006, Page 4see note on front cover
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Amended April 2006Recommended Practice DNV-RP-F103,  October 2003 see note on front cover Page 5
1.  General
1.1  Introduction
1.1.1  Submarine pipelines are designed with an external coat-ing as the primary system for corrosion control. Still, a cathodic protection (CP) system is normally provided as a back-up to account for any deficiency in the coating system. Such deficiencies may include holidays during coating manu-facturing, damage to the coating during transportation and installation of coated linepipe, and mechanical damage or other coating degradation during operation of the pipeline. In defining the required capacity of the CP system, the design of the pipeline coating system is the prim
ary factor.
Guidance note:
Pipeline coatings may have other objectives in addition to corro-sion control, including mechanical protection, thermal insulation and/or anti-buoyancy. In its widest sense, the term “pipeline coating” includes “linepipe coating” (or “factory coating”) applied on individual pipe joints in a factory, “field joint coating”
(FJC) and “coating field repairs” (CFR). In addition to the design of the coating system, the quality control of its application is essential for its performance and thus also for CP design.
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1.1.2  Cathodic protection of pipelines can be achieved using galvanic (or “sacrificial”) anodes, or impressed current from rectifiers. For submarine pipelines, galvanic anode systems are most commonly applied. Such systems have traditionally been designed as self-contained systems with all anodes installed directly on the pipeline itself (bracelet type anodes). However, the CP design in this document (as in ISO 15589-2) allows for CP by anodes installed on adjacent structures electrically con-nected to the pipeline such as platform sub-structures, subsea templates and riser bases.
For pipelines in CRA's susceptible to hydrogen induced stress cracking (HISC) by CP, this concept has the main advantage that the installation of anodes on the pipeline itself can be fully avoided for shorter lines.
Guidance note:
Apparently all failures of CRA pipelines due to HISC have been related to the welding of anodes to the pipeline causing stress concentrations, susceptible microstructure and defect coating.
The concept of installing anodes on adjacent structures also has the advantage that the complete anode surfaces are exposed to seawater, increasing the anode electrochemical performance and the anode current output compared to those for anodes partly or fully covered by seabed sediments. Moreover, the potential for damage to the pipeline coating during installation is reduced.
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1.1.3  The design of pipeline CP systems is mostly carried out in two steps; conceptual and detailed CP design. The ‘concep-tual CP design’ will typically include selection of anode mate-rial, tentative net mass and dimensions of anodes, and concept for fastening of anodes. The conceptual design sh
all further take into account potential detrimental effects of cathodic pro-tection such as the pipeline materials’ intrinsic susceptibility to hydrogen embrittlement by CP and the magnitude of local stresses induced during installation, commissioning and oper-ation of the pipeline that may lead to damage by HISC. For this conceptual CP design, reference is made to the applicable sec-tions of DNV-OS-F101 and ISO 15589-2 (see 1.3.1). During the ‘detailed CP design’ (i.e. as covered in this document), the final net anode mass and dimensions of anodes, and their dis-tribution on the pipeline are defined.
1.2  Scope
1.2.1  This Recommended Practice (RP) has been prepared to facilitate the execution of detailed CP design and the specifica-tion of galvanic anode manufacturing and installation. While the requirements and recommendations are general, the docu-ment contains advice on how amendments can be made to include project specific requirements. The document can also easily be amended to include requirements/guidelines by a reg-ulating authority, or to reflect the pipeline operator’s general philosophy on pipeline corrosion control.
Guidance note:
It is recommended that any additional conservatism is introduced by use of a “design factor” rather than modification of one or more of the many design parameters used for CP calculations.
For example, it may be specified that the design life shall be based on the maximum estimated lifetime of the pipeline multi-plied with some constant larger than 1 (one).
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1.2.2  The document covers the detailed design of CP for sub-marine pipeline systems (see 1.3.1) using galvanic anodes, either Al - or Zn -based, and the manufacturing and installation of such anodes. For CP of subsea manifold templates, riser bases and other subsea structures where components of a pipe-line system are electrically connected to major surfaces of structural C-steel, use of DNV-RP-B401 is recommended for CP design (see 1.5.3). For conceptual CP design, Sec.5 is applicable to preliminary calculations of the anode net mass and anode distribution. This RP is based on the sections in ISO 15589-2 that are applicable (see 1.3.1). For compliance with the general philosophy in DNV-OS-F101, primarily with respect to procedures for quality control, or for the purpose of clarification and guidance, some amendments are given. This RP further contains some formula for calculation of CP protec-tive range from adjacent structures and minimum distance betwe
en pipeline anodes that are not included in the ISO stand-ard. Default values for galvanic anode performance and design current densities that do not require any special qualification or field testing are also recommended.
1.2.3  By referring to specific pipeline coating systems for linepipe, field joints and field repairs in DNV-RP-F102 and DNV-RP-F106, and implementing the detailed requirements for the quality control of their manufacturing as defined in these documents, specific design parameters for calculation of current demands for CP are recommended in this RP. This is to enable a CP design without any arbitrary allowance for deficiencies associated with the design and quality control of such coatings, reducing the need for excessive conservatism in the design. In this RP, and contrary to ISO 15589-2, the current demands for cathodic protection are calculated for specific combinations of linepipe and field joint coating.
Guidance note:
In case certain deviations from the requirements to coating design and/or quality control of manufacturing in DNV-RP-F106 and DNV-RP-F102 are identified, the CP design parameters associated with pipeline coatings in this document (i.e. “coating breakdown factors”) may still be appl
icable. However, the user of this document should then carefully assess the significance of any such deviations.
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1.2.4  Full conceptual design of CP (see 1.1.3 and 1.2.2), detailed design of impressed current CP systems, testing of galvanic anode material for the purpose of either qualification or quality control, and the operation of pipeline CP systems are not addressed in this document. For these items, reference is made to the general guidelines in DNV-OS-F101 and the more detailed recommendations in ISO 15589-1, -2.
1.2.5  Although considerations related to safety and environ-mental hazards associated with galvanic anode manufacturing and installation are of great importance, such are never-the-less beyond the scope of this document.
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