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1、SP0169-2007 Standard Practice Control of External Corrosion on Underground or Submerged Metallic Piping Systems This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect precl
2、ude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by implication
3、or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted a
4、s a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpreta
5、tion or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of
6、this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health
7、and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard.Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practi
8、ces, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at
9、any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE Inter
10、national standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281 228-6200). Reaffirmed 2007-03-15 Reaffirmed 2002-04-11 Reaff
11、irmed 1996-09-13 Revised April 1992 Revised January 1983 Revised September 1976 Revised January 1972 Approved April 1969 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-035-1 2007, NACE International NACE SP0169-2007 (formerly RP0169-2002) Item No. 21
12、001 Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/18/2007 22:16:20 MDTNo reproduction or networking permitted without license from IHS -,-,- SP0169-2007 NACE International i _ Foreword This standard practic
13、e presents procedures and practices for achieving effective control of external corrosion on buried or submerged metallic piping systems. These recommendations are also applicable to many other buried or submerged metallic structures. It is intended for use by corrosion control personnel concerned w
14、ith the corrosion of buried or submerged piping systems, including oil, gas, water, and similar structures. This standard describes the use of electrically insulating coatings, electrical isolation, and cathodic protection (CP) as external corrosion control methods. It contains specific provisions f
15、or the application of CP to existing bare, existing coated, and new piping systems. Also included are procedures for control of interference currents on pipelines. This standard should be used in conjunction with the practices described in the following NACE standards and publications, when appropri
16、ate (use latest revisions): SP05721 RP01772 RP02853 SP01864 SP02865 SP03876 SP01887 TPC 118 TM04979 For accurate and correct application of this standard, the standard must be used in its entirety. Using or citing only specific paragraphs or sections can lead to misinterpretation and misapplication
17、of the recommendations and practices contained in this standard. This standard does not designate practices for every specific situation because of the complexity of conditions to which buried or submerged piping systems are exposed. This standard was originally published in 1969, and was revised by
18、 NACE Task Group (TG) T-10- 1 in 1972, 1976, 1983, and 1992. It was reaffirmed in 1996 by NACE Unit Committee T-10A on Cathodic Protection, and in 2002 and 2007 by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings. This standard is issued by NACE International under the auspic
19、es of STG 35, which is composed of corrosion control personnel from oil and gas transmission companies, gas distribution companies, power companies, corrosion consultants, and others concerned with external corrosion control of buried or submerged metallic piping systems. In NACE standards, the term
20、s shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something considered good and is recommended but is n
21、ot mandatory. The term may is used to state something considered optional. _ Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/18/2007 22:16:20 MDTNo reproduction or networking permitted without license from IH
22、S -,-,- SP0169-2007 ii NACE International _ NACE International Standard Practice Control of External Corrosion on Underground or Submerged Metallic Piping Systems Contents 1. General.1 2. Definitions.1 3. Determination of Need for External Corrosion Control .3 4. Piping Systems Design.4 5. External
23、Coatings6 6. Criteria and Other Considerations for CP12 7. Design of Cathodic protection Systems.17 8. Installation of CP Systems.20 9. Control of Interference Currents 22 10. Operationa and Maintenance of CP Systems24 11. External Corrosion Control Records25 References 26 Table 1.8 Table 2.8 Table
24、3.9 Table 4.10 Table 5.11 Bibliography for Section 614 Bibliography for Section 720 Appendix A 28 Appendix B 28 Appendix C 28 Appendix D 29 _ Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/18/2007 22:16:20 M
25、DTNo reproduction or networking permitted without license from IHS -,-,- SP0169-2007 NACE International 1 _ Section 1: General 1.1 This standard presents acknowledged practices for the control of external corrosion on buried or submerged steel, cast iron, ductile iron, copper, and aluminum piping sy
26、stems. 1.2 This standard is intended to serve as a guide for establishing minimum requirements for control of external corrosion on the following systems: 1.2.1 New piping systems: Corrosion control by a coating supplemented with CP, or by some other proven method, should be provided in the initial
27、design and maintained during the service life of the piping system, unless investigations indicate that corrosion control is not required. Consideration should be given to the construction of pipelines in a manner that facilitates the use of in-line inspection tools. 1.2.2 Existing coated piping sys
28、tems: CP should be provided and maintained, unless investigations indicate that CP is not required. 1.2.3 Existing bare piping systems: Studies should be made to determine the extent and rate of corrosion on existing bare piping systems. When these studies indicate that corrosion will affect the saf
29、e or economic operation of the system, adequate corrosion control measures shall be taken. 1.3 The provisions of this standard should be applied under the direction of competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics, acquired b
30、y education and related practical experience, are qualified to engage in the practice of corrosion control on buried or submerged metallic piping systems. Such persons may be registered professional engineers or persons recognized as corrosion specialists or CP specialists by NACE if their professio
31、nal activities include suitable experience in external corrosion control of buried or submerged metallic piping systems. 1.4 Special conditions in which CP is ineffective or only partially effective sometimes exist. Such conditions may include elevated temperatures, disbonded coatings, thermal insul
32、ating coatings, shielding, bacterial attack, and unusual contaminants in the electrolyte. Deviation from this standard may be warranted in specific situations provided that corrosion control personnel in responsible charge are able to demonstrate that the objectives expressed in this standard have b
33、een achieved. 1.5 This standard does not include corrosion control methods based on chemical control of the environment, on the use of electrically conductive coatings, or on control of internal corrosion. _ Section 2: Definitions (1) Amphoteric Metal: A metal that is susceptible to corrosion in bot
34、h acid and alkaline environments. Anode: The electrode of an electrochemical cell at which oxidation occurs. Electrons flow away from the anode in the external circuit. Corrosion usually occurs and metal ions enter solution at the anode. Anodic Polarization: The change of the electrode potential in
35、the noble (positive) direction caused by current across the electrode/electrolyte interface. (See Polarization.) Backfill: Material placed in a hole to fill the space around the anodes, vent pipe, and buried components of a cathodic protection system. Beta Curve: A plot of dynamic (fluctuating) inte
36、rference current or related proportional voltage (ordinate) versus the corresponding structure-to-electrolyte potentials at a selected location on the affected structure (abscissa) (see Appendix A nonmandatory). Cable: One conductor or multiple conductors insulated from one another. Cathode: The ele
37、ctrode of an electrochemical cell at which reduction is the principal reaction. Electrons flow toward the cathode in the external circuit. Cathodic Disbondment: The destruction of adhesion between a coating and the coated surface caused by products of a cathodic reaction. _ (1) Definitions in this s
38、ection reflect common usage among practicing corrosion control personnel and apply specifically to how the terms are used in this standard. In many cases, in the interests of brevity and practical usefulness, the scientific definitions are abbreviated or paraphrased. Copyright NACE International Pro
39、vided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/18/2007 22:16:20 MDTNo reproduction or networking permitted without license from IHS -,-,- SP0169-2007 2 NACE International Cathodic Polarization: The change of electrode potential in the acti
40、ve (negative) direction caused by current across the electrode/electrolyte interface. See Polarization. Cathodic Protection: A technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Coating: A liquid, liquefiable, or mastic composition tha
41、t, after application to a surface, is converted into a solid protective, decorative, or functional adherent film. Coating Disbondment: The loss of adhesion between a coating and the pipe surface. Conductor: A material suitable for carrying an electric current. It may be bare or insulated. Continuity
42、 Bond: A connection, usually metallic, that provides electrical continuity between structures that can conduct electricity. Corrosion: The deterioration of a material, usually a metal, that results from a reaction with its environment. Corrosion Potential (Ecorr): The potential of a corroding surfac
43、e in an electrolyte relative to a reference electrode under open-circuit conditions (also known as rest potential, open-circuit potential, or freely corroding potential). Corrosion Rate: The rate at which corrosion proceeds. Criterion: Standard for assessment of the effectiveness of a cathodic prote
44、ction system. Current Density: The current to or from a unit area of an electrode surface. Diode: A bipolar semiconducting device having a low resistance in one direction and a high resistance in the other. Distributed-Anode Impressed Current System: An impressed current anode configuration in which
45、 the anodes are “distributed” along the structure at relatively close intervals such that the structure is within each anodes voltage gradient. This anode configuration causes the electrolyte around the structure to become positive with respect to remote earth. Electrical Isolation: The condition of
46、 being electrically separated from other metallic structures or the environment. Electrical Survey: Any technique that involves coordinated electrical measurements taken to provide a basis for deduction concerning a particular electrochemical condition relating to corrosion or corrosion control. Ele
47、ctrode: A conductor used to establish contact with an electrolyte and through which current is transferred to or from an electrolyte. Electroosmotic Effect: Passage of a charged particle through a membrane under the influence of a voltage. Soil or coatings may act as the membrane. Electrolyte: A chemical substance containing ions that migrate in an electric field. For the purpose of this standard, electrolyte refers to the soil or liquid adjacent to and in contact with a buried or submerged metallic piping system, including the moist