EN 12474:2001
(Main)Cathodic protection of submarine pipelines
Cathodic protection of submarine pipelines
This European Standard establishes the general criteria and recommendations for the design, installation, monitoring and commissioning of the cathodic protection systems for submarine pipelines.
This standard is applicable to all grades of carbon manganese steel and to stainless steel pipelines; it covers all types of sea water and seabed environments encountered in submerged conditions.
The cathodic protection of short lengths of submarine pipelines and their branches, which are directly connected to cathodically protected onshore pipelines, are outside of the scope of this standard (see EN 12954:2001).
The cathodic protection of risers is included in this standard only if they are insulated from the supporting structure. The cathodic protection of the risers in direct electrical contact with the supporting structure is included in EN 12495.
Kathodischer Korrosionsschutz für unterseeische Rohrleitungen
Anwendungsbereich
Diese Europäische Norm stellt allgemeine Kriterien und Empfehlungen für die Auslegung, Installation,
Überwachung und Inbetriebnahme kathodischer Korrosionsschutzsysteme für unterseeische Rohr-leitungen
auf.
Diese Norm gilt für Rohrleitungen aus Kohlenstoff-Mangan-Stahl aller Güteklassen und aus nicht
rostendem Stahl. Sie behandelt sämtliche Arten von Meerwasser- und Meeresgrundumgebungen, die
unter Wasser anzutreffen sind.
Diese Norm gilt nicht für kurze Abschnitte unterseeischer Rohrleitungen oder ihrer Abzweigungen, die
mit kathodisch geschützten Festlandsrohrleitungen leitend verbunden sind (siehe EN 12954:2001).
Der kathodische Korrosionsschutz von Steigleitungen ist in dieser Norm nur dann einbezogen, wenn
sie von ihren Trägerstrukturen isoliert sind. Der kathodische Korrosionsschutz von Steigleitungen, die in
direkter elektrischer Verbindung mit ihren Trägerstrukturen stehen, ist in der EN 12495 enthalten.
Protection cathodique des canalisations sous-marines
La présente Norme européenne définit les critères et les recommandations d'ordre général relatifs à l'étude, à l'installation, au contrôle et à la mise en service des systèmes de protection cathodique des canalisations sous-marines.
La présente norme est applicable à des canalisations en acier au carbone manganèse et en acier inoxydable de toutes nuances ; elle couvre tous les types d'eau de mer et de fonds marins susceptibles d'être rencontrés dans les conditions d'immersion.
La protection cathodique de courtes longueurs de canalisations sous-marines et de leurs ramifications qui sont directement connectées à des canalisations terrestres protégées par un système de protection cathodique, ne fait pas partie du domaine d'application de la présente norme (voir EN 12954:2001).
La protection cathodique des colonnes montantes (risers) est couverte par la présente norme uniquement si ces dernières) sont isolées de la structure porteuse. La protection cathodique des colonnes montantes (risers) en contact électrique direct avec la structure porteuse est couverte par l'EN 12495.
Katodna zaščita podmorskih cevovodov
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2003
.DWRGQD]DãþLWDSRGPRUVNLKFHYRYRGRY
Cathodic protection of submarine pipelines
Kathodischer Korrosionsschutz für unterseeische Rohrleitungen
Protection cathodique des canalisations sous-marines
Ta slovenski standard je istoveten z: EN 12474:2001
ICS:
25.220.40 Kovinske prevleke Metallic coatings
47.020.30 Sistemi cevi Piping systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN 12474
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2001
ICS 23.040.99; 77.060
English version
Cathodic protection of submarine pipelines
Protection cathodique des canalisations sous marines Katodischer Korrosionsschutz für unterseeische
Rohrleitungen
This European Standard was approved by CEN on 7 March 2001.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12474:2001 E
worldwide for CEN national Members.
Page 2
Contents
Foreword.3
Introduction .4
1 Scope.4
2 Normative references.4
3 Terms and definitions.4
4 Criteria and principles for cathodic protection design .5
5 Design of sacrificial anodes system .8
6 Installation of sacrificial anodes.10
7 Design of impressed current systems.11
8 Installation of impressed current systems.12
9 Commissioning of cathodic protection systems.13
10 Control of interference currents .14
11 Monitoring and surveying of cathodic protection system.16
12 Safety.17
13 Documentation .18
Annex A (informative) Guidance on current requirements for cathodic protection of pipeline and risers .19
Annex B (informative) Anode sizing calculations.21
Annex C (informative) Attenuation curves.22
Annex D (informative) Safety precautions for impressed current system .24
Annex E (informative) Typical electrochemical characteristics for commonly used impressed current
anodes.25
Bibliography.26
Page 3
Foreword
This European Standard has been prepared by Technical Committee CEN/TC 219 "Cathodic Protection", the
secretariat of which is held by BSI.
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 2001, and conflicting national standards shall be withdrawn at the latest
by October 2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland and the United Kingdom.
Page 4
Introduction
Cathodic protection, together with a corrosion protection coating, is usually applied to protect the external surface
of submarine pipelines from corrosion due to sea water or saline mud.
The corrosion protection coating is applied on the external surface of the pipeline to insulate the steel surface from
the aggressive environment into which the pipeline is surrounded.
The cathodic protection ensures the protection of the areas of the pipeline which are directly exposed to the
aggressive marine environment due to damage or defects in the coating.
The cathodic protection supplies sufficient direct current to the external surfaces of the pipeline to reduce the pipe
to electrolyte potential to values where there is insignificant corrosion.
The general principles of cathodic protection are detailed in EN 12473.
1 Scope
This European Standard establishes the general criteria and recommendations for the design, installation,
monitoring and commissioning of the cathodic protection systems for submarine pipelines.
This standard is applicable to all grades of carbon manganese steel and to stainless steel pipelines; it covers all
types of sea water and seabed environments encountered in submerged conditions.
The cathodic protection of short lengths of submarine pipelines and their branches, which are directly connected to
cathodically protected onshore pipelines, are outside of the scope of this standard (see EN 12954:2001).
The cathodic protection of risers is included in this standard only if they are insulated from the supporting structure.
The cathodic protection of the risers in direct electrical contact with the supporting structure is included in
EN 12495.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 12473:2000, General principles of cathodic protection in sea water.
EN 12495, Cathodic protection for fixed steel offshore structures.
prEN 12496:1996, Sacrificial anodes for cathodic protection in sea water.
EN 12954:2001, Cathodic protection of buried or immersed metallic structures - General principles.
EN ISO 8044, Corrosion of metals and alloys – Basic terms and definitions (ISO 8044:1999).
3 Terms and definitions
For the purposes of this European Standard the terms and definitions in EN ISO 8044 and the following apply:
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3.1
weight coating
coating usually made of steel wire reinforced concrete, applied to the pipes to provide anti-buoyancy and/or
mechanical protection of the pipeline
3.2
remotely operated vehicle (R.O.V.)
unmanned submarine vehicle operated by a surface vessel and used for inspection and survey of the pipeline
3.3
"J" tube
curved tubular conduit designed and installed on a structure to support and guide one or more pipeline risers or
cables
3.4
riser
vertical or near vertical portion of an offshore pipeline which connects the platform piping to the pipeline at or below
the sea bed
4 Criteria and principles for cathodic protection design
4.1 Protective criteria
4.1.1 Protective potentials
To achieve adequate cathodic protection a submarine pipeline should have the protective potentials indicated in
the following table. These potentials apply to saline mud and normal sea water compositions (salinity 32 ‰ to
38 ‰).
Table 1 — Summary of potential versus silver/silver chloride/sea water reference electrode recommended
for the cathodic protection of steel materials in sea water
Material Minimum negative potential Maximum negative potential
volt volt
Iron and steel
aerobic environment -0,80 -1,10
anaerobic environment -0,90 -1,10
Stainless steel
Austenitic steel
-0,30 no limit
- (PREN 40)
- (PREN < 40) -0,60 (see note 1) no limit
-0,60 (see note 1) (see note 2)
Duplex
NOTE 1 For most applications these potentials are adequate for the protection of crevices although more negative
potentials may be considered.
NOTE 2 Depending on metallurgical structure these alloys may be susceptible to cracking and more negative
potentials should be avoided (in accordance with 8.3.2.2 of EN 12473:2000).
4.1.2 Reference electrodes
The following types of reference electrodes may be used to measure the potential between the pipeline surface
and sea water:
- silver-silver chloride/seawater (Ag/AgCl/sea water);
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- high purity zinc (99,9 % min. of zinc with iron content not exceeding 0,0014 %)/sea water;
- anode zinc alloy/seawater;
- saturated KCl calomel (Hg/HgCl /KCl saturated) for reference electrode calibration purposes only.
4.2 Corrosion protection coating
A corrosion protection coating is normally applied to a submarine pipeline in conjunction with cathodic protection to
control external corrosion. The coating reduces the current required to achieve effective cathodic protection and
enhances the distribution of the cathodic protection current over the pipeline surface (see table A.3).
4.3 Basic parameters
The following should be taken into consideration when designing a cathodic protection system:
- characteristics of the submarine pipeline to be protected, such as diameter, wall thickness, length, route, laying
conditions on the sea bottom, temperature profile along its whole length, type and thickness of corrosion
protection coating(s) for pipes and fittings, presence, type and thickness of thermal insulation, mechanical
protection, and/or weight coating;
- existing or proposed installations (pipelines, platforms etc.) in close proximity to or crossing of the pipeline
route;
- the requirement for electrical isolation from adjoining steel structures, platform, onshore pipelines etc.;
- presence of "J" tubes, risers and clamps;
- environmental conditions;
- design life of the pipeline;
- pipeline lay method;
- protection criteria;
- offshore site i.e. accessibility for repair and replacement;
- performance data of cathodic protection systems in the same environment site;
- availability of electric power;
- safety requirements;
- applicable codes;
- risk assessment.
4.4 Environmental parameters
The following environmental parameters should be evaluated through field measurements if experience from the
area is limited.
- temperature;
- sea water and mud resistivity;
- sea water velocity;
-pH;
- water pressure (depth) along the route;
Page 7
- presence and quantity of H S producing bacteria (e.g. SRB);
- water composition with particular reference to the oxygen content;
- presence of stray and/or telluric currents in the area (see 10.2).
4.5 Protective current density
One of the main parameters to be defined in the design of the cathodic protection system for a submarine pipeline
is the current density required to protect the steel surface of the pipeline throughout all its design life.
Three values of current density are significant. The initial, maintenance and repolarization values which refer
respectively to the current density required to polarize the pipeline within a reasonable time period (i.e. 1 to 2
months) the current density necessary to maintain the polarization and the current density necessary for an
eventual repolarization which may occur for example after an heavy storm.
The selection of the design current densities may be based on experience from similar pipelines in the same
environment or on field measurements carried out in the same area.
Due consideration should be given to the following:
- the current density demand is normally not constant with time; for bare steel areas of pipelines in seawater or
the seabed the current density requirements may decrease due to the formation of calcareous deposits
caused by the cathodic current;
- for coated areas of pipelines the current requirements may increase with time as the coating deteriorates.
Guidelines on the design current densities are given in annex A.
4.6 Selection of the cathodic protection system
Either sacrificial anode and/or impressed current cathodic pr
...
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