1、BRITISH STANDARD Cathodic protection of submarine pipelines The European Standard EN 12474:2001 has the status of a British Standard ICs 23.040.01 NO COPYING WITHOUT nsI PERMISSION EXCEPT AS PERMITTED nY COPYRIGHT LAW BS EN 12474:2001 BS EN 12474:2001 National foreword This British Standard, having
2、been prepared under the direction of the Electrotechnica Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 25 October 2001 This British Standard is the official English language version of EN 12474:2001. Attention is drawn to th
3、e fact that BS 7361-1:1991, Cathodicprotection - Part i: Code of practice for land and marine applications, provides general information on cathodic protection. Note that BS 7361-1:1991 will eventually be withdrawn when all the CEN standards relating to cathodic protection currently being prepared a
4、re published. The UK participation in its preparation was entrusted to Technical Committee GEL/603, Cathodic protection which has the responsibility to: - - aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for chang
5、e, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or E
6、uropean publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the n
7、ecessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page,
8、 pages 2 to 26, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. IDate I Comments 0 BSI 25 October 2001 ISBN O 580 38543 4 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NO
9、RM EN 12474 April 2001 ICs 23.040.99; 77.060 English version Cathodic protection of submarine pipelines Protection cathodique des canalisations sous marines Katodischer Korrosionsschuh fr unterseeische Rohrleitungen This European Standard was approved by CEN on 7 March 2001. CEN members are bound to
10、 comply with the CENICENELEC 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 Manage
11、ment 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 of
12、ficial versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland. Ireland, Italy, Luxembourg, Netherlands, Noway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMI
13、TE EUROPEEN DE NORMALISATION EUROPISCHES KOMITEE FOR NORMUNG Management Centre: rue de Stassart, 36 8-1050 Brussels O 2001 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12474:2001 E Page 2 EN 12474:2001 Contents Foreword 3 Introd
14、uction . 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 8 9 10 11 12 Safety 17 13 Documentation 18 Annex A (informative) Guidance on curr
15、ent requirements for cathodic protection of pipeline and risers . 19 Design of impressed current systems 11 Installation of impressed current systems . 12 Commissioning of cathodic protection systems . 13 Control of interference currents 14 Monitoring and surveying of cathodic protection system 16 A
16、nnex 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 EN
17、 12474:2001 Foreword This European Standard has been prepared by Technical Committee CENTTC 21 9 “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 t
18、he latest by October 2001, and conflicting national standards shall be withdrawn at the latest by October 2001. According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Rep
19、ublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Page 4 EN 12474:2001 Introduction Cathodic protection, together with a corrosion protection coating, is usually applied to protect
20、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
21、ensures the protection of the areas of the pipeline which are directly exposed to the aggressive manne 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
22、to values where there is insignificant corrosion. The general principles of cathodic protection are detailed in EN 12473. i Scope This European Standard establishes the general criteria and recommendations for the design, installation, monitoring and commissioning of the cathodic protection systems
23、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 branc
24、hes, 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
25、 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 nonnative references are cited at the appropriate places in the text and the public
26、ations 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 ame
27、ndments). 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
28、- General principles. EN IS0 8044, Corrosion of metals and alloys - Basic terms and definitions (IS0 8044:1999). 3 Terms and definitions For the purposes of this European Standard the terms and definitions in EN IS0 8044 and the following apply: Page 5 EN 12474:2001 3.1 weight coating coating usuall
29、y made of steel wire reinforced concrete, applied to the pipes to provide anti-buoyancy andlor 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 t
30、ubular conduit designed and installed on a structure to support and guide one or more pipeline risers or cables Material 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 Minimum negative potential volt 4 Cr
31、iteria and principles for cathodic protection design -0,30 -0,60 (see note 1) -0,60 (see note 1) 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 a
32、pply to saline mud and nonnal sea water compositions (salinity 32 %O to 38 %o). Table 1 - Summary of potential versus silver/silver chloridelsea water reference electrode recommended for the cathodic protection of steel materials in sea water Iron and steel aerobic environment anaerobic environment
33、Stainless steel Austenitic steel - (PRENr40) - (PRENC40) Duplex -0,ao -0.90 Maximum negative potential volt -1,lO -1,lO I no limit no limit (see note 2) NOTE 1 For most applications these potentials are adequate for the protection of crevices although more negative potentials may be considered. NOTE
34、 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 pi
35、peline surface and sea water: - silver-silver chlondelseawater (Ag/AgCl/sea water); ., . .-. :, . ., :. .,: *. . .,. Page 6 EN 12474:2001 - - anode zinc alloylseawater; - high purity zinc (99,9 % min. of zinc with iron content not exceeding 0,0014 %)/sea water; saturated KCI calomel (Hg/HgCI$KCI sat
36、urated) 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
37、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 protect
38、ed, 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
39、 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, platorm, onshore pipelines etc.; presence of “J“ tubes, risers and clamps; - - - - environmental
40、 conditions; - design life of the pipeline; - pipeline lay method; - protection criteria; - - - availability of electric power; - safety requirements; - applicable codes; offshore site .e. accessibility for repair and replacement; performance data of cathodic protection systems in the same environme
41、nt site; - 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 velocity; - PH; - sea water and mud resistivity; water pressure (depth) along the route;
42、 Page 7 EN 12474:2001 - presence and quantity of H2S producing bacteria (e.g. SRB); - - 4.5 Protective current density water composition with particular reference to the oxygen content; presence of stray and/or telluric currents in the area (see 10.2). One of the main parameters to be defined in the
43、 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
44、 to the current density required to polarize the pipeline within a reasonable time period (.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
45、 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
46、pipelines in seawater or the seabed the current density requirements may decrease due to the formation of calcareous deposits caused by the cathodic current; - Guidelines on the design current densities are given in annex A. 4.6 Selection of the cathodic protection system for coated areas of pipelin
47、es the current requirements may increase with time as the coating deteriorates. 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 impre
48、ssed 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 c
49、oated pipeline versus the surrounding electrolyte at the end of its design service life (see annex C), - the lack of a source of external power may preclude the use of impressed current systems; the longitudinal resistance of the pipeline (see annex C); - - 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 neighbounng structures, whereas impressed current system may have a significant effect. - 4.7 Electrical isolation Electrical isol
