NACE 7L198-2009 Design of Galvanic Anode Cathodic Protection Systems for Offshore Structures (Item No 24196)《海上结构物的电流阳极阴极保护系统的设计 项目编号24196》.pdf
《NACE 7L198-2009 Design of Galvanic Anode Cathodic Protection Systems for Offshore Structures (Item No 24196)《海上结构物的电流阳极阴极保护系统的设计 项目编号24196》.pdf》由会员分享,可在线阅读,更多相关《NACE 7L198-2009 Design of Galvanic Anode Cathodic Protection Systems for Offshore Structures (Item No 24196)《海上结构物的电流阳极阴极保护系统的设计 项目编号24196》.pdf(25页珍藏版)》请在麦多课文档分享上搜索。
1、 Item No. 24196 NACE International Publication 7L198 (2009 Edition) This Technical Committee Report has been prepared by NACE International Specific Technology Group 30,*“Oil and Gas ProductionCathodic Protection.” Design of Galvanic Anode Cathodic Protection Systems for Offshore Structures February
2、 2009, NACE International This NACE International (NACE) technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or usin
3、g products, processes, or procedures not included in this report. Nothing contained in this NACE report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifyi
4、ng or protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable c
5、ircumstances may negate the usefulness of this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and f
6、or determining their applicability in relation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this report
7、. Users of this NACE report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of t
8、his report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if more than 10 years old. Purchasers of NACE repo
9、rts may receive current information on all NACE International publications by contacting the NACE FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281-228-6200). Foreword This NACE technical committee report summarizes the approaches and experience of Task Gro
10、up T-7L-16 on the design of galvanic anode cathodic protection systems for offshore structures. Cathodic protection system designers can use this report as a guide for recently published data and theoretical developments. Although the concepts discussed here were developed for galvanic anode cathodi
11、c protection systems for offshore structures, some of the concepts may be applicable to other cathodic protection systems. The first part of this report describes a new design method based on first principles derivations. The second part of the report summarizes laboratory and field experimental dat
12、a related to the new design approach. The third part gives examples of how existing design criteria are incorporated into the new design equation and presents two example designs using the new equation. Appendix A presents an example of design procedures. The new design approach allows more precise
13、design of cathodic protection systems, particularly in areas such as deep water or new geographic areas where extensive experience is not available. _ * Chair Ian Rippon, Shell Global Solutions UK Ltd., Aberdeen, UK. NACE International 2 This report was originally prepared in 1998 by Task Group T-7L
14、-16, a component of Unit Committee T-7L, “Cathodic Protection,” under the auspices of Group Committee T-7, “Corrosion by Waters.” The report was reviewed and reaffirmed in 2009 by Specific Technology Group (STG) 30, “Oil and Gas ProductionCathodic Protection.” It is published under the auspices of S
15、TG 30. NACE technical committee reports are intended to convey technical information or state-of-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this informati
16、on are factual and are provided to the reader as input and guidance for consideration when applying this technology in the future. However, these statements are not intended to be recommendations for general application of this technology, and must not be construed as such. Introduction Historically
17、, cathodic protection system design for offshore structures using galvanic anodes was based on a single nominal maintenance current density intended to protect a structure over the system design life, after polarizing it to a protected potential within several months. This maintenance current densit
18、y was identified from service experience and was used simply to determine the amount of anode material to be used. Today, typical design practices incorporate three design current densities: initial, maintenance, and final. The reason behind using three design current densities compared to the earli
19、er single maintenance current density approach is because of the technical and economic benefits derived from the rapid polarization resulting from application of an initially high current density. Unless an effort is made to optimize anode size and shape, the use of three design criteria usually re
20、sults in three different answers for the number of anodes required, indicating a fundamental inconsistency among the typical values. If the three criteria are viewed as minimum criteria, the design for bare structures is normally driven by the initial current density criterion. For coated structures
21、, the design is normally driven by the final or maintenance current density criteria. In this case, the actual amount of anode material calculated is greater than has been shown in the past to provide the needed design life. Therefore, the result is increased life, not reduced cost. The experimental
22、 data and example designs in this report are appropriate for uncoated structures. Although the applicable standards1,2have been revised, published experimental data3,4,5and theoretical developments provide a simpler and more universal empirical option to describe the polarization process to cathodic
23、ally protected steel in seawater. This description leads to a simplified design procedure that incorporates both the rapid polarization and long-term maintenance current concepts into a single equation. The final current density concept is also sometimes included in the framework of this new method.
24、 In addition, these concepts are often applied to analysis of in-service cathodic protection survey data. Although polarization is a critical factor in the new offshore cathodic protection system design method, the details of the polarization process and deposition of calcareous films are beyond the
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