1、 STD*BSI BS EN 12495-ENGL 2000 Lb24hb7 OALI9109 15T = BS EN BRITISH STANDARD Cathodic protection for fixed steel offshore structures The European Standard EN 124952000 has the status of a British Standard ICs 47.020.01; 77.060 12495:2000 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYR
2、IGHT LAW STDmBSI BS EN 1,2t95-ENGL 2000 D Lb2rlbb9 08rl9L10 971 AmdNo. BS EN 124962000 Date Comments ThisBritjshstandard,having been prepared under the di - present to the responsible European committee any enquiries on the - monitor related intrnational and European developments and promulgate inim
3、pretation, or proposals for change, and keep the UK interess inform4 them in the UK. A iist of organktions represented on this committee can be obtained on request to its secretary. Cross-references “he Briish Standards which implement international or European publications referred to in this docum
4、ent may be found in the BSI Standards catalogue under the section entitled “International Standards Correspondence Index“, or by using the “Find“ facility of the MI Standards Electronic Catalogue. A Brtkh standard does not purport to include ali the necessary provisions of a contract Users of Britis
5、h 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, pages 2 to 32, an inside back cover and a back co
6、ver. The BSI copyright notice isplayed in this document indicates when the document waslastissued. I I EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12495 January 2000 ICs 47.020.01; 77.060 English version Cathodic protection for fixed steel offshore structures Protection cathodique des struc
7、tures en acier fixes en mer Katodischer Korrosionsschutz von ortsfesten Offshore- Anlagen aus Stahl This European Standard was approved by CEN on 3 December 1999. CEN members are bound to comply with the CENICENELEC Internal Regulations which stipulate the conditions for giving this Europsan Standar
8、d the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning sich national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, Ge
9、rman). A version in any other language made by traislation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as tie official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark,
10、Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG COMIT EUROPEN DE NORMALISATION Central Secretariat: rue de Stassart, 36 6-1050 Br
11、ussels 8 2000 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12495:2000 E Page 2 EN 12495:2000 Contents Page Foreword 4 Introduction . 5 1 i . 1 I . 2 1.3 a 3 4 4.1 4.2 4.3 4.4 4.5 5 5.1 5.2 5.3 5.4 5.5 6 6.1 6.2 6.3 6.4 7 7.1 7.2
12、 Scope 5 Structural parts 5 Materials . 5 Environment . 6 Normative references 6 Terms and definitions . 6 Design basis 8 Objectives 8 Cathodic protection criteria . . 9 Electrical current demand 9 Coatings . 10 Cathodic protection systems . Anode dimensions . 11 Design of galvanic anodes system 11
13、General . 11 Design considerations 12 Galvanic anode materials . 12 Location of anodes 13 Anodes inserts and attachments design . 14 Design of impressed current system 15 General . 15 Design considerations 15 Equipment considerations . 16 Location considerations . 17 Design of monitoring systems . 1
14、7 Objectives 18 Description . 18 Q BSI 05-2000 STD-ES1 ES EN 12q15-ENGL 2000 E Lb24bb9 0649LL3 bAO I 7.3 7.4 7.5 7.6 8 9 9.1 9.2 9.3 10 10.1 Page 3 EN 124952000 Potential measurements 19 Measurement of the anode electrical current output 19 Transmission of data 20 Control and monitoring of impressed
15、 current generators . 20 Installation of cathodic protection and monitoring systems . 20 Commissioning and surveying of cathodic protection systems . 20 Objectives 20 Galvanic anode system 21 Impressed current system . 21 Documentation 21 General . 21 10.2 Galvanic anodes system 21 10.3 11 Impressed
16、 current system . 22 Safety and cathodic protection . 22 11.1 Objectives 22 11.2 Physical obstructions . 23 11.3 Electric shock 23 11.4 Gas evolution 23 Annex A (informative) Guidance on current requirement for cathodic protection of fixed steel offshore structures . 24 Annex B (informative) Anode r
17、esistance and life duration formulae 26 Annex C (informative) Recommendations for anode installation . 29 Annex D (informative) Safety precautions for impressed current system . 30 Annex E (informative) Typical electrochemical characteristics for commonly used impressed current anodes 31 Bibliograph
18、y 32 O BSI 05-2000 Page 4 EN 124952000 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 te
19、xt or by endorsement, at the latest by July 2000, and conflicting national standards shall be withdrawn at the latest by July 2000. According to the CENCENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria
20、, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Noway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Annexes A, B, C, D, and E of this European Standard are informative. 8 BSI 05-2000 Page 5 EN 12495:2000 Introduc
21、tion Cathodic protection, possibly together with protective coating or paint, is usually applied to protect the external surfaces of fixed steel offshore structures and appurtenances from corrosion due to sea water or marine sediments. The general principles of cathodic protection are detailed in pr
22、EN 12473:1999. The cathodic reaction ensures the protection from corrosion of the submerged areas of the structure and associated appurtenances which are exposed to the marine environment. Cathodic protection involves the supply of sufficient direct current to the external surface of the structure i
23、n order to reduce the steels electrolyte potential down to values where corrosion is insignificant. I Scope This European Standard defines the means to be used to cathodically protect the submerged areas of fixed steel offshore structures and appurtenances. 1.1 Structural parts This European Standar
24、d defines the requirements for the cathodic protection of fixed structures, including sub sea production and related protective structures whether connected or not to each other by pipelines and/or walkways. It also covers the submerged areas of appurtenances attached to the structure, when these ar
25、e electrically connected to the structure. It does not cover the cathodic protection of floating structures such as ships, semi-submersible units, or elongated structures such as pipelines or cables. This European Standard concerns only the cathodic protection of external surfaces, in contact with t
26、he sea water or with the sea bed. It covers the immersed or buried external surfaces of the jacket, conductor pipes, well casings, piles, J-tubes, production or utility risers, etc. It does not cover the corrosion protection of the sections of the structure above the sea level, .e. the splash zone a
27、nd atmospheric zone. This standard does not include the internal protection of any components such as jacket members, legs, conductor pipes; the protection of these is often performed using chemicals. I .2 Materials This European Standard covers the cathodic protection of bare or coated steels with
28、a specified minimum yield strength (S.M.Y.S.) not exceeding 500 Nmm. 1.2.1 Overpolaritation and high strength steels If the potential of the structure becomes too negative the structure will become overpolarized and this can induce a penetration of hydrogen into the steel wall, resulting in emmttlem
29、ent of the metal, and subsequently a possible detrimental effect, including propagation of cracks. As a general indication the higher the tensile properties, the greater is the risk of hydrogen induced damage. However, material hardness and microstructure are also important. These phenomena can occu
30、r on conventional steels used for offshore fixed structures (grade S355 as per EN 10025) at potentials more negative than -1,l O V vs. Ag/AgCl/sea water. Relevant tests should be performed for the use of cathodic protection outside these limits. O BSI 05-2000 STD=BSI BS EN 22495-ENGL 2000 W lb24bb7
31、OB4711b 3T Page 6 EN 124952000 1.2.2 Galvanic coupling Some parts of the structure can be made of metallic materials other than carbon manganese steel. The cathodic protection system should be designed to ensure that there is complete control over any galvanic corrosion arising from this coupling. 1
32、.3 Environment This European Standard is applicable for the whole submerged zone in any kind of sea water or sea bed. For surfaces which are alternately immersed and exposed to the atmosphere, the cathodic protection is only effective when the immersion time is sufficiently long for the steel to bec
33、ome polarized. This is the case on about the lowest third part of the tidal zone. A different method of corrosion protection shall be therefore used for the protection of the wetted surface located above this level, .e. by using a protective coating, cladding, sheathing or increasing the thickness o
34、f the structural material. 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, subsequ
35、ent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendement or revision. For undated references the latest edition of the publication referred to applies. prEN 12473:1999, General principles of cathodic protection in sea wate
36、r: prEN 12496:1997, Sacrificial anodes for cathodic protection in sea water. EN 10025, Hot rolled products of non-alloy structural steels - Technical delivery conditions. 3 Terms and definitions For the purpose of this European Standard the terms and definitions in prEN 12473;1999 and the following
37、apply. 3.1 atmospheric zone zone located above the splash zone, .e. above the level reached by the normal swell 3.2 buried zone zone located under the mud line 3.3 conductor pipe first installed casing of an offshore well 3.4 doubler plate plate welded onto a member to locally reinforce it or to iso
38、late it from further welding work 3.5 extended tidal zone zone including the tidal zone, the splash zone and the transition zone 3.6 H.A.T. level of the highest astronomical tide Q BSI 05-2000 STD-BSI BS EN 12495-ENGL 2000 3b211bb9 08119337 22b 3.7 immersed zone zone located below the extended tidal
39、 zone and above the mud line Page 7 EN 12495:2000 3.8 J-tube curved tubular conduit designed and installed on a structure to support and guide one or more pipeline risers or cables 3.9 L.A.T. level of the lowest astronomical tide 3.10 marine sediments top layer of the sea bed composed of water satur
40、ated solid materials of various densities 3.1 1 M.T.L. mean tide level (also known as M.S.L. or M.W.L.) 3.12 pile deep foundation element supporting a fixed offshore structure 3.13 riser vertical or near vertical portion of an offshore pipeline between the platform piping and the pipeline at or belo
41、w the seabed, including a length of pipe of at least five pipe diameters beyond the bottom elbow, bend or fitting 3.14 salinity amount of inorganic salts dissolved in the sea water. The standardized measurement is based on the determination of the electrical conductivity of the sea water. Salinity i
42、s expressed in grams per kilogram or in ppt 3.15 splash zone height of the structure which is intermittently wet and dry due to the wave action just above the H.A.T 3.16 submerged zone zone including the buried zone, the immersed zone and the transition zone 3.1 7 tidal zone zone located between the
43、 L.A.T. and the H.A.T 3.18 transition zone zone located below the L.A.T. and including the possible level inaccuracy of the platform installation and a depth with a usually higher oxygen content due to the normal swell 3.19 well casing string of steel pipes lowered into oil, gas or water producing w
44、ells to shut off water or to prevent the caving in of loose ground O BSI 05-2000 Page 0 1 EN 124952000 Extended tidal zone Submerged zone Atmospheric zone Splash zone H.A.T. Tidal zone M.T.L. Transition zone Immersed zone Figure I - Schematic representation of levels and zones in sea water environme
45、nt 4 Design basis 4.1 Objectives The major objective of a cathodic protection system is to deliver sufficient current to protect each pari of the structure and appurtenances and distribute this current so that the steel to sea water potential of each part of the structure is within the limits given
46、by the potential criteria (refer to 4.2). Potentials should be as homogeneous as possible over the whole structure. This aim may only be approached by an adequate distribution of the anodes over the structure. This is difficult to achieve in some areas such as complex nodes or frames of conductor gu
47、ides where little room can be allocated for the installation of anodes though large surfaces are to be protected. Therefore consideration should be given at the structure design stage: O BSI 05-2000 STD-BSI BS EN 12495-ENGL 2000 Lb24bb OB4LL OT Page 9 EN 12495:2000 - - - A protective coating may be
48、used near anodes where their current output and proximity to the structure may lead to overpolarization (see 1.2.1 ). The cathodic protection system should normally be designed for the lifetime of the structure. In order to achieve an appropriate design of the cathodic protection system it should be
49、 carried out by a cathodic protection specialist. 4.2 Cathodic protection criteria The cathodic protection criteria are detailed in prEN 12473:1999. To achieve an adequate cathodic protection level, steel structures should have protective potentials as indicated in the following table. by avoiding complex configurations, .e. tubular elements are preferred rather than T or H profiles; by reducing the number of ancillary surfaces; by limiting the ratio of steel surfaces over electrolyte volume in congested areas. Table 1 - Summary of potential versus silverlsilv
