SIST EN 12474:2003
(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 criteres et les recommandations d'ordre général relatifs a l'étude, a l'installation, au contrôle et a la mise en service des systemes de protection cathodique des canalisations sous-marines.
La présente norme est applicable a des canalisations en acier au carbone manganese et en acier inoxydable de toutes nuances ; elle couvre tous les types d'eau de mer et de fonds marins susceptibles d'etre rencontrés dans les conditions d'immersion.
La protection cathodique de courtes longueurs de canalisations sous-marines et de leurs ramifications qui sont directement connectées a des canalisations terrestres protégées par un systeme 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 dernieres) 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
SIST EN 12474:2003
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
SIST EN 12474:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST EN 12474:2003
---------------------- Page: 2 ----------------------
SIST EN 12474:2003
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: 3 ----------------------
SIST EN 12474:2003
Page 2
EN 12474:2001
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: 4 ----------------------
SIST EN 12474:2003
Page 3
EN 12474:2001
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: 5 ----------------------
SIST EN 12474:2003
Page 4
EN 12474:2001
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:
---------------------- Page: 6 ----------------------
SIST EN 12474:2003
Page 5
EN 12474:2001
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);
---------------------- Page: 7 ----------------------
SIST EN 12474:2003
Page 6
EN 12474:2001
- 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.
2
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: 8 ----------------------
SIST EN 12474:2003
Page 7
EN 12474:2001
- presence and quantity of H S producing bacteria (e.g. SRB);
2
- 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 protection system may be used to protect a submarine
pipeline.
The selection between the two systems should be based on the following considerations:
- the impressed current system may only protect a finite length of pipeline, determined by the following:
- practical limitations on the locations for impressed current system installations, e.g. the ends of the
pipeline and intermediate platforms or landfalls,
- the value of the insulation resistance of the coated pipeline versus the surrounding electrolyte at the end
of its design service life (see annex C),
- the longitudinal resistance of the pipeline (see annex C);
- the lack of a source of external power may preclude the use of impressed current systems;
- sacrificial anode systems do not require any operation control or maintenance during the service life of the
pipeline;
- sacrificial anode systems seldom cause serious interaction problems on foreign neighbouring structures,
whereas impressed current system may have a significant effect.
4.7 Electrical isolation
Electrical isolation between a submarine pipeline and other steel structures to which the pipeline is mechanically
connected may be used in order to improve or verify the effectiveness of the relevant cathodic protection system.
Cases where insulating devices may be used are as follows:
- between the offshore and the onshore sections of the same pipeline;
---------------------- Page: 9 ----------------------
SIST EN 12474:2003
Page 8
EN 12474:2001
- between a submarine pipeline and the platform where the pipeline starts and/or ends unless other constraints,
such as safety requirements, dictate that an insulating device should not be installed.
If used the insulating devices shall be placed above the water and splash zone and in compliance with relevant
regulations.
4.8 Electrical continuity
Electrical continuity is generally provided between the pipeline and any ancillary steel items by means of suitable
connecting cables.
4.9 Test points
To check the performance of the cathodic protection on a submarine pipeline measuring cables and test points
may be installed at both the ends of the pipeline if direct contacts are not possible.
For submarine pipelines protected by sacrificial anodes any permanent measuring devices along the pipeline route
may be omitted but the extremities shall remain accessible either directly or by means of a measuring cable.
4.10 Miscellaneous
During the design stage of the cathodic protection system of a submarine pipeline all the interested parties in the
area of the pipeline route should be notified of the proposed pipeline installation and the characteristics of the
cathodic protection system.
Cooperative investigations should be carried out to determine the possible effect of the proposed pipeline cathodic
protection system on the facilities of others in the proximity or area of the proposed pipeline.
5 Design of sacrificial anodes system
5.1 General
The sacrificial anodes system provides protection of the steel structure by connecting it to a more electronegative
alloy.
Generally the sacrificial anodes are electrically connected to the pipeline by welding.
The sacrificial anodes system shall be designed to ensure that the protective potential criteria is achieved on the
whole surface of the pipeline during its entire design life.
5.2 Selection of anodic material
The following types of anode materials may be used: alloys of aluminium, magnesium, or zinc.
The alloy selected shall be one that can be demonstrated by past field performance in similar conditions, or by
laboratory and field trials in simulated equivalent conditions, to perform satisfactorily in accordance with
prEN 12496:1996. The selection of anode composition is critical for effective performance in specific environments.
5.2.1 to 5.2.3 are a general guide only.
5.2.1. Aluminium alloy anodes
Aluminium alloy anodes can be used in sea water or in the sea bed.
Aluminium based alloys have a decreased electrochemical efficiency at elevated temperature. Some alloys may
not even be suitable when operated at elevated temperatures.
The behaviour of some aluminium alloys may be adversely affected when covered with mud and particularly at low
current output.
Some alloys may suffer intergranular corrosion even at low temperatures.
---------------------- Page: 10 ----------------------
SIST EN 12474:2003
Page 9
EN 12474:2001
Some alloys containing magnesium may suffer ageing with a loss of mechanical properties.
5.2.2. Magnesium alloy anodes
Magnesium alloy anodes can cause very negative potentials usually beyond the negative limit and have a high
practical consumption rate; however they may be used in special applications.
5.2.3. Zinc alloy anodes
Zinc alloy anodes can be used in sea water or in the sea bed.
Zinc based alloys should be formulated to minimize the risk of intergranular attack.
Zinc alloys may undergo a reduction in driving potential and should not be used at temperatures exceeding 50 °C
unless supported by appropriate test data.
Intergranular corrosion and/or a reduction of their current capacity may occur at elevated temperatures.
5.2.4. Anode performance
The electrochemical properties of the anodic material include:
- the driving voltage to polarized steel i.e. the difference between closed circuit anode potential and the positive
limit of the protective potential criteria;
- the practical current capacity (in ampere hour per kilogramme) or consumption rate (in kilogrammes per
ampere per year);
- the susceptibility to passivation;
- the susceptibility to intergranular corrosion.
The main parameters which affect anode electrochemical properties are:
- anode exposure conditions (if immersed in sea water or buried in mud);
- chemical composition of anode alloy;
- temperature;
- method and procedure of fabrication.
The electrochemical properties of the anodic material should be documented or determined by appropriate tests
approved by an independent body.
The environmental impact of the alloy should be taken into consideration.
5.3 Shape and dimensions of sacrificial anodes
Sacrificial anodes for submarine pipelines are typically half shell or segmented bracelet type, but other types may
be considered.
Bracelet anodes shall be provided with suitable steel inserts to allow the assembly and tightening of the bracelet
halves or segments around the pipe and to give adequate support to the anodic material.
The inserts should be located in such a way to achieve the design utilization factor (see annex B).
The dimensions of the anodes should be selected on the basis of the following:
- external pipe diameter;
- corrosion coating thickness;
---------------------- Page: 11 ----------------------
SIST EN 12474:2003
Page 10
EN 12474:2001
- any restraints due to the anode fabrication process;
- suitability to the pipeline laying method and relevant equipment;
- weight coating thickness, if present;
- current output and life requirements (see 5.4).
For submarine pipelines without a concrete weight coating or with the external diameter of the bracelet greater than
the external diameter of the concrete coated pipes, both ends of the bracelet anodes should be tapered to the
pipeline or external surface of the weight coating. Practical foundry techniques may limit the extent of this taper.
5.4 Sacrificial anode design
The design of the sacrificial anode system should be based on the following: (see also annex B)
- the total amount of anode material shall be sufficient to protect the pipeline for the whole of the design life;
- the available current output of the anodes shall be higher than the current required to protect the pipeline
during the service life;
- the anodes shall be spaced at intervals along the pipeline to ensure that the current delivered by the anodes is
distributed effectively on the pipeline surface;
- on pipeline systems close to other steel installations (e.g. platforms, submarine structures etc.) additional
anodes should be provided to take into account possible current drainage to other installations;
- at crossing with a previously installed pipeline the location of the anodes of both the pipelines close to crossing
should be checked to prevent any significant reduction of the protection levels and/or any increase in the rate
of anode consumption.
6 Installation of sacrificial anodes
6.1 Sacrificial anode assembly on pipes
The sacrificial anodes shall be mounted on the pipes in such a way as to avoid any slippage during pipeline laying
and to maintain a reliable electrical connection to the pipeline.
Several methods may be used; typical methods employed for the assembly of half shell bracelet anodes include
the fastening of the two halves of each bracelet anode around the pipe by welding together the coupling steel strip
inserts of the bracelet anodes or by bolting together the two bracelet anode halves.
6.2 Electrical connection between bracelet anode and steel pipe
To provide electrical continuity between bracelet anode and the pipeline the following methods may be used:
- insulated copper cables welded or brazed to the anode inserts and the steel pipe;
- fillet welding of the anode insert to the pipe directly, or, preferably, to a doubler plate pre-installed on the pipe
joint.
The connection between the insulated copper cable and the steel pipe may be carried out by the following two
general methods: thermite welding and brazing.
The welding procedure should be qualified to ensure that the mechanical strength and the electrical continuity of
the connection is adequate. It is also necessary to verify that the welding process does not affect the mechanical
properties of the steel pipe and that it does not induce any cracks in the pipe wall.
---------------------- Page: 12 ----------------------
SIST EN 12474:2003
Page 11
EN 12474:2001
6.3 Installation procedure
Bracelet anode installation should be carried out in such a way that any significant damage to the pipe coating
beneath the anode is minimised.
The bracelet anodes shall be tightened with adequate compressive strength around the linepipe to avoid any
slippage during the pipeline laying.
Where a connection cable is to be used each bracelet anode should be electrically connected to the pipe by at
least two attachments and preferably two for each half of the anode.
Suitable bonding cables shall be installed in a way that minimizes the possibility of their mechanical damage.
Welding should not be within 150 mm of any pipe welds.
At cable-to-pipe or fillet welding connections corrosion protection coating should be properly repaired.
After each anode installation with cable connections the electrical resistance between the anode and the relevant
pipe should be checked by a suitable technique to ensure adequate continuity.
Any steel reinforcement in the concrete weight coating should not be in electrical contact with pipe or anode.
6.4 Underwater installation
Only in exceptional cases, (e.g. the retrofit of a cathodic protection system or the use of remote anode assemblies,
for example on small diameter pipelines) should the underwater installation of anodes, utilizing either mechanical
fixing devices or welding connections, be carried out.
Welding should be performed in a dry environment.
Wet welding is not permitted on pipe walls. It should only be used on parts of the pipeline system where cracks and
defects would not be significant (i.e. doubler plate, existing anode inserts and supports).
Mechanical fixing devices may not give reliable electrical connections for long term applications.
7 Design of impressed current systems
7.1 General
Impressed current cathodic protection systems applied to submarine pipelines may consist of one or more cathodic
protection stations located at one or both the ends of pipeline or at intermediate landfalls or structures.
Each station consists of the following equipment:
- transformer - rectifier/s or direct current electric power generator/s;
- impressed current anodes;
- connecting cables and current distribution boxes where necessary.
Impressed current systems should not cause any detrimental effect on the integrity of other pipelines and/or
structures existing in the same area (see clause 9).
7.2 Materials
Impressed current anode materials may be high silicon cast iron, mixed metal oxides activated titanium, platinum
coated or clad niobium, tantalum or titanium, lead alloys, graphite, magnetite or scrap-steel.
See annex E for impressed current anode performance characteristics.
Rectifiers may be constant current, potential controlled or manually controlled.
---------------------- Page: 13 ----------------------
SIST EN 12474:2003
Page 12
EN 12474:2001
Cables should be provided with insulation sheathing suitable for marine environment and an external jacket for
adequate protection from mechanical damage.
The electrical connection between the anode and the anode cable should be watertight and mechanically sound.
7.3 Impressed current system sizing
The impressed current system should be capable of protecting the entire length of the pipeline with the number of
installed cathodic protection stations provided with remote groundbeds.
The current output capacity of the cathodic protection station/s should be based on the attenuation curve equations
of the pipeline (see annex C). These equations give the variation of the pipe-to-electrolyte potential and the
variation of the line current along the pipeline when the current is drained from one or more points of the pipeline
and discharged to earth at the same location.
The application of the attenuation curves requires the evaluation of the insulation resistance of the pipeline at the
time of the highest current demand, which may be at the end of its design life when, it has the lowest value due to
coating degradation, or may be at the time of peak operating temperature.
The transformer rectifier should have a current output at least 25 % over the current required for the protection of
the pipeline during the whole of its service life.
The impressed current anodes may be buried onshore or laid on the sea bed.
The anode should be sized to provide a low electrical resistance in the cathodic protection current circuit in order
that the output voltage of the transformer-rectifier at the maximum current output does not exceed 50 V for safety
reasons.
The total anodic material weight shall be greater than the anodic material consumed during all its design life at the
maximum current output of the transformer-rectifier.
In case of inert composite anodes (e.g. platinum coated titanium anodes) the anode operating voltage shall be
lower than the breakdown voltage of the oxide film of the anode base metal.
The minimum distance of the anode from the structure should be selected to avoid the protective potential of the
pipeline section close to the anode being beyond the negative limit of the protective criteria (see 4.1 and annex C).
The design anode c
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.