1、BRITISH STANDARD Cathodic protection for steel offshore floating structures The European Standard EN 13173:2001 has the status of a British Standard ICs 75.180.10; 77.060 BS EN 13173:ZOOl NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 13173:2001 Amd. No. National forewo
2、rd Date Comments This British Standard is the official English language version of EN 13173:2001. Reference should also be made to BS 7361, Code of practice for land and marine applications, which will eventually be withdrawn when all the CEN standards relating to cathodic protection currently being
3、 prepared, are published. The UK participation in its preparation was entrusted to Technical Committee GEU603, 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 proposa
4、ls for change, 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 intern
5、ational or European 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 inclu
6、de all the necessary 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. This British Standard, having been prepared under the direction of the Electrotechnic
7、al Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15June2001 Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 25 and a back cover. The BSI copyright date displayed in this document in
8、dicates when the document was last issued. O BSI 06-2001 ISBN O 580 37634 6 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM O EN 13173 January 2001 ICs 47.020.01; 77.060 English version Cathodic protection for steel offshore floating structures Protection cathodique des structures en acier flottan
9、t en mer Kathodischer Korrosionsschutz fr schwimmende Offshore- Anlagen aus Stahl This European Standard was approved by CEN on 6 July 2000. CEN members are bound to comply with the CENICENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a nati
10、onal 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
11、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,
12、Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMEE FOR STANDARDIZATION COMITE EUROPEEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels O 2001 CEN All rights
13、of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13173:2001 E Page 2 EN 131 73:2001 Contents Foreword 4 Introduction . 4 1 Scope 5 1.1 Structures 5 1.2 Materials . 5 1.3 Environment 5 1.4 Safety and environment protection . 6 2 Normative reference
14、s 6 3 Terms and definitions 6 4 Design basis . 7 4.1 Objectives 7 4.2 Cathodic protection criteria . 7 4.3 Design parameters 7 Cathodic protection systems . 1 0 4.6 Electrical continuity 11 4.4 Electrical current demand 8 4.5 4.7 Interactions 11 5 5.1 objectives 11 5.2 Design considerations 12 5.3 E
15、quipment considerations . 12 6 Galvanic anode system design . 14 6.1 Objectives 14 6.2 Design considerations 14 6.3 Factors determining the anode current output and operating life . 15 6.4 Location of anodes . 16 Impressed current system design 11 Page 3 EN 131 73:2001 7 Cathodic protection system m
16、onitoring 16 7.1 Objectives 16 7.2 Potential measurements 16 7.3 Measurement of the impressed current anode electrical current output 17 7.4 7.5 Additional monitoring methods . 17 8 Documentation . 18 Impressed current power source control . 17 8.1 Objectives 18 8.2 8.3 Annex A (informative) structu
17、res . 20 Impressed current system . 18 Galvanic anode systems 19 Guidance for current requirements for cathodic protection of offshore floating Annex B (informative) Anode resistance and life determination 21 Annex C (informative) Typical electrochemical characteristics of impressed current anodes .
18、 23 Annex D (informative) Typical cofferdam arrangements . 24 Page 4 EN 131 73:2001 Foreword This European Standard has been prepared by Technical Committee CEN/TC 21 9 “Cathodic protection“, the secretariat of which is held by BSI. This European Standard shall be given the status of a national stan
19、dard, either by publication of an identical text or by endorsement, at the latest by July 2001, and conflicting national standards shall be withdrawn at the latest by July 2001. According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are boun
20、d 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 EN 131 73:2001 Introduction Cathodic protection is usually
21、 applied, mostly as a complement to protective coating or paint, to protect the external surfaces of steel offshore floating structures and appurtenances from corrosion due to sea water or saline mud. Cathodic protection works by supplying sufficient direct current to the immersed surface of the str
22、ucture in order to change the steel to electrolyte potential to values where corrosion is insignificant. The general principles of cathodic protection are detailed in EN 12473. 1 Scope steel offshore floating structures and appurtenances in sea water and saline mud. 1.1 Structures This European Stan
23、dard defines the means to be used to cathodically protect the submerged metallic surfaces of This European Standard covers the cathodic protection of the external surface of offshore floating structures which are static during their usual operating conditions. This essentially includes: barges, jack
24、-ups, semi-submersible platforms, storage tankers, buoys, etc. It also covers the submerged areas of appurtenances, such as chains, attached to the structure, when these are not electrically isolated from the structure. It does not cover the cathodic protection of ships, fixed offshore structures, e
25、longated structures (pipelines, cables) or harbour installations, which are covered by other standards. This European Standard concerns only the cathodic protection of external surfaces immersed in sea water, including sea chests and water intakes up to the first valve. This EuroDean Standard does n
26、ot include the internal protection of surfaces of any components such as ballast tanks and hull internals of floating structures. 1.2 Materials This European Standard covers the cathodic protection of structures fabricated principally from bare or coated carbon manganese steels As some parts of the
27、structure may be made of metallic materials other than carbon manganese steels, the cathodic protection system should be designed to ensure that there is a complete control over any galvanic coupling and minimise risks due to hydrogen embrittlement or hydrogen induced cracking (see EN 12473). This E
28、uropean Standard does not cover concrete structures. 1.3 Environment This European Standard is applicable for the whole submerged zone in sea water, brackish waters, saline mud which can normally be found where the floating structure is anchored, moored or moving. This European Standard is also appl
29、icable to appurtenances which may be in contact with muds (e.g. chains). Page 6 EN 131 73:2001 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 become polarised. 1.4 Safe
30、ty and environment protection This European Standard does not cover safety and environmental protection aspects associated with cathodic protection. The relevant national or international regulations shall apply. 2 Normative references This European Standard incorporates, by dated or undated referen
31、ces, 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 incorporat
32、ed in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 12473, General principles of cathodic protection in sea water. prEN 12496, Galvanic anodes for cathodic protection in sea water. 3 Terms and definitions For
33、the purposes of this European Standard the terms and definitions in EN 12473 and the following apply: 3.1 atmospheric zone zone located above the wetted zone; that means above the level reached by the normal swell, whether the structure is moving or not 3.2 boot topping section of the hull between l
34、ight and fully loaded conditions, which may be intermittently immersed 3.3 Cathodic Protection zone that part of the structure which can be considered independently with respect to cathodic protection design 3.4 immersed zone zone located below the water line at draught corresponding to normal worki
35、ng conditions 3.5 submerged zone zone including the immersed and the buried zones 3.6 underwater hull part of the hull vital for its stability and buoyancy of a floating structure, .e. below the light water line Page 7 EN 131 73:2001 4 Design basis 4.1 Objectives The major objective of a cathodic pr
36、otection system is to deliver sufficient current to protect each part of the structure and appurtenances and distribute this current so that the potential of each part of the structure is within the limits given by the protection criteria (see 4.2). Potentials should be as uniform as possible over t
37、he whole structure. This objective may only be approached by an adequate distribution of the protective current over the structure during its normal service conditions. However, it may be difficult to achieve in some areas such as chains, water intakes, sea chests, when supplementary cathodic protec
38、tion systems should be considered. The cathodic protection system for a floating structure is generally combined with a coating system, even though some appurtenances, such as chains, may not benefit from a coating protection. Dielectric shields may be used in conjunction with anodes to minimise the
39、 risk of local over-protection. the maintenance dry-docking interval. 0 The cathodic protection system should be designed either for the life of the structure or for a period corresponding to The above objectives should be achieved by the design of a cathodic protection system using galvanic anodes
40、or impressed current systems or a combination of both. 4.2 Cathodic protection criteria The criteria for cathodic protection are detailed in EN 12473. To achieve an adequate cathodic protection level, steel structures should have potentials as indicated hereafter. The accepted criterion for protecti
41、on of steel in aerated sea water is a potential more negative than -0,80 V measured with respect to Ag/AgCVsea water reference electrode. A negative limit of -1,lO V (Ag/AgCl/sea water reference electrode) is generally recommended. Where there is a possibility of coating disbondment and corrosion fa
42、tigue, the negative limit should be more positive. This negative limit should be documented. 4.3 Design parameters The design of a cathodic protection system should be made in accordance with the following parameters: structure subdivision, components description and service conditions. 4.3.1 Struct
43、ure subdivision A floating structure can be divided into different Cathodic Protection zones, (CP zones), which are then considered independently with respect to cathodic protection design, although they may not necessarily be electrically isolated. EXAMPLE 1 therefore constitute a CP zone by themse
44、lves (e.g. : seachests). For a storage tanker, some specific components may not be included in the underwater hull CP zone and EXAMPLE 2 influenced part of the mooring chain(s). 4.3.2 Description of CP zones For buoys, a single zone is generally considered, including two components: the body of the
45、buoy and the Each C.P. zone may consist of several components which should be fully described including material, surface area and coating characteristics (type, lifetime and coating breakdown factor). O Page 8 EN 131 73:2001 4.3.3 Service conditions The design of the cathodic protection system(s) w
46、ill depend on service conditions which include: expected life time, environment and operating conditions. - - - Life time: either the whole design life or dry-docking interval(s) should be considered. Environment: the sea water properties should be established (see EN 12473). Operating conditions: t
47、he cathodic protection design normally considers only the static conditions of the structure because the durations when dynamic conditions prevail are generally negligible. 4.4 Electrical current demand 4.4.1 General To achieve the criteria for protection for the conditions outlined in 4.3, it is ne
48、cessary to select the appropriate current density for each component. The current demand of each metallic component of the structure is the result of the product of its surface area multiplied by the required current density. 4.4.2 Protection current density for bare steel The current density requir
49、ed may not be the same for all components of the structure as the environmental and service conditions are variable. e The selection of design current densities may be based on experience gained from similar structures in a similar environment or from specific tests and measurements. The current density depends on the kinetics of electrochemical reactions and varies with parameters such as the protection potential, surface condition, dissolved oxygen content in sea water, sea water velocity at the steel surface, temperature. The following should be evaluated for each design: - initial
