1、 Standard Practice Corrosion Control of Submerged Areas of Permanently Installed Steel Offshore Structures Associated with Petroleum Production This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptan
2、ce does not in any respect preclude 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 gra
3、nting 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 indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and s
4、hould in no way be interpreted as 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 r
5、esponsibility for the interpretation 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
6、individual volunteers. Users of 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 necessari
7、ly 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 standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, an
8、d 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 this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, an
9、d may be revised or withdrawn at any time in accordance with NACE technical committee procedures.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 and subsequently from the date of each reaff
10、irmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International First Service Department, 1440 South Creek Dr., Houston
11、, Texas 77084-4906 (telephone +1 281/228-6200). Revised 2007-03-10 Revised 2003-06-21 Revised March 1994 Revised May 1983 Approved April 1976 NACE International 1440 South Creek Dr. Houston, TX 77084-4906 +1 (281)228-6200 ISBN 1-57590-170-6 2007, NACE International NACE SP0176-2007 (formerly RP0176-
12、2003) Item No. 21018 SP0176-2007 NACE International i _ Foreword Offshore structures represent large capital investments. Structures are being placed in offshore areas worldwide and are being designed to withstand forces resulting from hurricanes, arctic storms, tidal currents, earthquakes, and ice
13、floes. Moreover, platform structures are currently being placed in deeper waters and, therefore, have become larger, more complex, and more expensive. Control of corrosion on structures is necessary for the economic development of oil and gas production, to provide safe support for working and livin
14、g areas, and to avoid potential harm to the environment. For the purposes of this standard, offshore structures are considered to be stationary structures (platforms or subsea facilities) that are fixed to the sea floor by gravity, pilings, or mooring cables. This NACE standard is intended for use b
15、y corrosion control personnel concerned with the corrosion of steel fixed offshore platforms associated with petroleum production. It outlines materials, practices, and methods for control of corrosion for steel fixed structures associated with petroleum production located in offshore areas. The pur
16、pose is to facilitate more effective corrosion protection of structures by the presentation of reliable information. Corrosion on offshore structures can be divided into three major areas: the submerged zone, the splash zone, and the atmospheric zone. The submerged zone also includes that portion of
17、 the structure below the mudline. This standard does not include procedures for the control of internal corrosion of wells, piping, and associated equipment that may be in use on the structure, but does include external protection of these items in the atmospheric zone on the structure. This standar
18、d was originally issued in 1976 and revised in 1983 by Task Group (TG) T-1-2 on North Sea Corrosion Problems. It was revised in 1994 by TG T-1-5, and in 2003 and 2007 by TG 170 on Offshore Steel PlatformsCorrosion Control: Review of NACE Standard RP0176, which is administered by Specific Technology
19、Group (STG) 30 on Oil and Gas ProductionCathodic Protection. All editions of this standard prior to 2007 included a section on coatings on offshore platforms. However, it was determined this subject would be more appropriately covered in another standard. Therefore, NACE TG 313 was formed to develop
20、 the standard on coatings.1TG 170 is sponsored by STG 02 on Protective Coatings and LiningsAtmospheric and STG 05 on Cathodic/Anodic Protection. This standard is issued by NACE under the auspices of STG 30. In NACE standards, the terms shall, must, should, and may are used in accordance with the def
21、initions 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 not mandatory. The term may is used to state something considered o
22、ptional. _ SP0176-2007 ii NACE International _ NACE International Standard Practice Corrosion Control of Submerged Areas of Permanently Installed Steel Offshore Structures Associated with Petroleum Production Contents 1. General . 1 2. Definitions . 1 3. Structural Design for Corrosion Control 3 4.
23、Criteria for CP . 4 5. Design of Cathodic Protection Systems 5 6. Installation of Cathodic Protection Systems 15 7. Control of Interference Currents . 17 8. Dielectric Shields 18 9. Operation and Maintenance of Cathodic Protection Systems 18 10. Corrosion Control Records . 20 References 21 Bibliogra
24、phy 22 Appendix A: Typical Design Parameters for Offshore Petroleum Production (Nonmandatory) 23 Appendix B: Energy Capabilities and Consumption Rates of Various Commercial Galvanic Anodes Available for Cathodic Protection of Offshore Structures (Nonmandatory) 25 Appendix C: Consumption Rates in Sea
25、water of Various Commercial Types of Impressed Current Anodes Available for Cathodic Protection of Offshore Structures (Nonmandatory) 26 Appendix D: Typical Method for Calculation of Galvanic Anode Current Output Using Initial, Maintenance, and Final Current Densities (Nonmandatory). 27 Appendix E:
26、Typical Method for Calculation of Galvanic Anode Current Output Using Design Slope and Maintenance Current Density (Nonmandatory) . 29 FIGURES Figure 1: Nomogram for the Correction of Potential Readings Made with the Ag/AgCl Electrode in Waters of Varying Resistivity to the Saturated Calomel or Cu/C
27、uSO4Scale . 8 Figure 1A: Current Density/Temperature Curves . 25 _ SP0176-2007 NACE International 1 _ Section 1: General 1.1 This standard provides guidelines for establishing minimum requirements for the control of corrosion on steel fixed offshore structures associated with petroleum production, a
28、nd on the external portions of associated oil and gas handling equipment. Fixed structures include platforms, tension leg platforms (TLP), and subsea templates. This standard does not include guidelines for corrosion control of temporarily moored mobile vessels used in petroleum production. 1.2 For
29、this standard, corrosion on structures is divided into three zones: the submerged, splash, and atmospheric zones. However, only the submerged zone is addressed in this standard. The atmospheric and splash zones are addressed in a standard that is currently a work in progress by NACE TG 313. 1.3 This
30、 standard does not designate guidelines for every specific situation because of the complexity of environmental conditions. In many instances, the problem may have several solutions and, when appropriate, meritorious alternative solutions have been included. 1.4 This standard does not include guidel
31、ines for corrosion control of the internal portions of wells, piping, and associated equipment that may be installed on or attached to structures. 1.5 Underwater pipelines and pipeline risers are specifically excluded from this standard. 1.6 Alternative methods are acceptable to achieve a protected
32、potential over an adequate design life; however, deviation should be made only if, in the opinion of a competent corrosion specialist, the objectives expressed in the standard have been achieved. _ Section 2: Definitions NOTE: Additional definitions for cathodic protection (CP) and coatings technolo
33、gy may be found in NACE SP0169,2the NACE Corrosion Engineers Reference Book,3and the NACE International Glossaryof Corrosion-Related Terms.4Anode: The electrode of an electrochemical cell at which oxidation occurs. Electrons flow away from the anode in the external circuit. Corrosion usually occurs
34、and metal ions enter the solution at the anode. Atmospheric Zone: The zone of the structure that extends upward from the splash zone and is exposed to sun, wind, spray, and rain. Calcareous Coating or Deposit: A layer consisting of calcium carbonate and other salts deposited on the surface. When the
35、 surface is cathodically polarized as in cathodic protection, this layer is the result of the increased pH adjacent to the protected surface. Cathode: The electrode of an electrochemical cell at which reduction is the principal reaction. Electrons flow toward the cathode in the external circuit. Cat
36、hodic Protection: A technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Coating: A liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film. C
37、orrosion: The deterioration of a material, usually a metal, that results from a reaction with its environment. Corrosion Specialist: A person who, by reason of education and experience, is qualified to evaluate and solve problems related to the corrosion of materials. In this standard, corrosion spe
38、cialist refers to one who is qualified in the control of corrosion in marine environments. Current: (1) A flow of electric charge. (2) The amount of electric charge flowing past a specified circuit point per unit time, measured in the direction of net transport of positive charges. (In a metallic co
39、nductor, this is the opposite direction of the electron flow.) Current Density: The current to or from a unit area of an electrode surface. Depolarization: The removal of factors resisting the current in an electrochemical cell. Dielectric Shield: An electrically nonconductive material, such as a co
40、ating, sheet, or pipe, that is placed between an anode and an adjacent cathode, usually on the cathode, to improve current distribution in a cathodic protection system. SP0176-2007 2 NACE International Doubler Plate: An additional plate or thickness of steel used to provide extra strength at the poi
41、nt of anode attachment to an offshore platform. Electrical Isolation: The condition of being electrically separated from other metallic structures or the environment. Electrolyte: A chemical substance containing ions that migrate in an electric field. Fairlead: A sheave over which an anchor chain or
42、 cable passes. Foreign Structure: Any metallic structure that is not intended as a part of a system under cathodic protection. Galvanic Anode: A metal that provides sacrificial protection to another metal that is more noble when electrically coupled in an electrolyte. This type of anode is the elect
43、ron source in one type of cathodic protection. Holiday: A discontinuity in a protective coating that exposes unprotected surface to the environment. Impressed Current: An electric current supplied by a device employing a power source that is external to the electrode system. (An example is direct cu
44、rrent for cathodic protection.) Interference Current (Stray Current): Current through paths other than the intended circuit. For the purposes of this standard, interference current is current discharged to the electrolyte from a structure that may be either (1) not an intended part of the circuit or
45、 (2) an intended part of the circuit that is not adequately connected to the current source. J Tube: A curved tubular conduit designed and installed on a structure to support and guide one or more pipeline risers or cables. Mudline: The ocean floor at the location of interest. Node: The point on an
46、offshore structure at which two structural elements connect, for example, where a horizontal structural member is welded to the jacket leg. Pipeline: A conduit for carrying produced oil, water, and gas between structures or between structures and onshore processing facilities. Platform: An offshore
47、structure used to accommodate oil and gas wells, related production equipment, pipelines, and living quarters. Polarization: The change from the open-circuit potential as a result of current across the electrode/electrolyte interface. Reference Electrode: An electrode whose open-circuit potential is
48、 constant under similar conditions of measurement, which is used for measuring the relative potentials of other electrodes. Riser: (1) That section of pipeline extending from the ocean floor up to an offshore structure. (2) The vertical tube in a steam generator convection bank that circulates water and steam upward. Silver/Silver Chloride Electrode: For the purposes of this standard, a reference electrode that uses seawater as the junction electrolyte, for exampl
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