1、 Standard Practice Design, Installation, Operation, and Maintenance of Impressed Current Deep Anode Beds 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 preclude any
2、one, 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 or othe
3、rwise, 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 as a res
4、triction 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 interpretation or
5、 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 this NA
6、CE 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 and saf
7、ety 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 practices, i
8、n 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 CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any ti
9、me 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 reaffirmation or revision. The user is cauti
10、oned 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, Texas 77084-4906 (telephone +1 281/22
11、8-6200). Reaffirmed 2007-03-14 Revised 2001-03-10 Revised March 1995 Revised January 1985 Approved June 1972 NACE International 1440 South Creek Drive Houston, TX 77084-4906 +1 (281)228-6200 ISBN 1-57590-117-X 2007, NACE International NACE SP0572-2007 (formerly RP0572) Item No. 21007 SP0572-2007 NAC
12、E International i _ Foreword The purpose of this NACE International standard practice is to present procedures and practices for the design, installation, operation, and maintenance of deep anode beds used for the control of external corrosion of underground or submerged metallic structures by impre
13、ssed current cathodic protection (CP). It is intended to be used in conjunction with NACE SP01691and SP0177.2This standard is intended to be used by corrosion engineers, corrosion consultants, representatives from manufacturers, and others concerned with corrosion control of underground structures.
14、This standard was originally prepared in 1972 by NACE Task Group (TG) T-10A-7, a component of Unit Committee T-10A on Cathodic Protection, and was revised in 1985, 1995, and 2001, and reaffirmed in 2007 by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings. This standard is iss
15、ued by NACE under the auspices of STG 35. In NACE standards, the terms 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. Should is used to
16、 state something considered good and is recommended but is not mandatory. May is used to state something considered optional. _ SP0572-2007 ii NACE International _ NACE International Standard Practice Design, Installation, Operation, and Maintenance of Impressed Current Deep Anode Beds Contents 1. G
17、eneral. 1 2. Definitions. 1 3. Environmental Considerations . 3 4. Design 4 5. Installation 7 6. Operation, Maintenance, and Replacement. 9 References 10 Bibliography 11 Appendix A, Typical Deep Anode Designs (Nonmandatory) 11 FIGURES Figure A1: Closed Hole 11 Figure A2: Closed Hole with Surface Cas
18、ing. 12 Figure A3: Open Hole with Surface Casing . 13 Figure A4: Environmentally Addressed System. 14 Figure A5: Typical Replaceable Closed Hole. 15 _ SP0572-2007 NACE International 1 _ Section 1: General 1.1 This standard presents acceptable methods for the design, installation, operation, and main
19、tenance of deep anode beds that discharge impressed current for CP of underground or submerged metallic structures. 1.2 This standard is based on the best available technology and methods that have been used successfully by experienced corrosion engineers. 1.3 This standard does not designate method
20、s for every specific situation because the complexity of some environ-mental conditions precludes standardizing all design and installation procedures. 1.4 The provisions of this standard should be applied under the direction of a competent corrosion engineer. The term corrosion engineer, as used in
21、 this standard, refers to a person who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics acquired by education and related practical experience, is qualified to engage in the practice of corrosion control of underground or submerged structures. 1.5 Ot
22、her types of groundbeds should be investigated before the decision is made to use a deep anode bed, because more economical alternatives may be available. 1.6 Codes, laws, and regulations in a local geographic area may require supplements to or deviation from this standard. 1.7 Necessary precautions
23、 must be taken to prevent damage to existing underground structures and deleterious modification of ground water quality. 1.8 Adequate records containing information showing site right-of-way, installation procedures, operation data, maintenance, repair, and test records should be maintained._ Secti
24、on 2: Definitions Abandonment: The discontinued use of a deep anode system. Active Zone: The segment of the deep anode system that is designed to discharge current. In this standard, the active zone refers to that length of deep anode bed that is made up of carbonaceous backfill. In an open-hole ins
25、tallation, the active zone is the aqueous electrolyte. Annular Space: The space between the well casing and the well bore or the space between two or more strings of well casing. Anode: The electrode of an electrochemical cell at which oxidation occurs. Electrons flow away from the anode in the exte
26、rnal circuit. Corrosion usually occurs and metal ions enter the solution at the anode. In this standard, the anode is the positive terminal of the impressed electrical system from which current is discharged. Anode Cap: An electrical insulating material placed over the end of the anode at the lead w
27、ire connection. Anode Connection Encapsulation: An electrical insulating material placed over the end of the anode or within the interior of the anode body to maintain the electrical integrity of the anode-to-lead-wire connection. For the purposes of this standard, it is understood that some interna
28、l anode-to-lead-wire connections do not require the addition of electrical insulating encapsulation. Aquifer: A water-bearing stratum of permeable rock, sand, or gravel. Backfill: Material placed in a hole to fill the space around the anodes, vent pipe, and buried components of a cathodic protection
29、 system. Blowdown: (1) Injection of air or water under high pressure through a tube to the anode area for the purpose of purging the annular space and possibly correcting high resistance caused by gas blockage. (2) In conjunction with boilers or cooling towers, the process of discharging a significa
30、nt portion of the aqueous solution in order to remove accumulated salts, deposits, and other impurities. Bore Hole: A hole drilled into the earth for the installation of a deep anode bed system. Cathodic Protection (CP): A technique to reduce the corrosion of a metal surface by making that surface t
31、he cathode of an electrochemical cell. Closed Hole: A groundbed installation in which the anodes have been surrounded by backfill. Typically, in a closed-hole installation, the backfill consists of a conducting carbonaceous backfill around the anodes, and above the active zone is native soil sealing
32、 material or other suitable material. Alternately, the top of the anode hole may be sealed with a plastic casing from the surface to the top of the anode backfill and left open. Conductive Carbon Seal: Conductive seal (nonporous conductive material). SP0572-2007 2 NACE International Continuous Anode
33、: A single anode with no electrical discontinuities. For the purposes of this standard, the active zone of the groundbed may be considered a conducting continuous anode. Continuous Rail Groundbed: A rail groundbed to be used as an anode and extending from the earths surface to a depth greater than 1
34、5 m (50 ft) below the earths surface. Continuous Steel Pipe Groundbed: A steel pipe to be used as an anode and extending from the earths surface to a depth greater than 15 m (50 ft) below the earths surface. Corrosion: The deterioration of a material, usually a metal, that results from a reaction wi
35、th its environment. Cross Contamination: Fluid flow between two aquifers. Current Density: The current to or from a unit area of an electrode surface. Deep Anode Bed: One or more anodes installed vertically at a nominal depth of 15 m (50 ft) or more below the earths surface in a drilled hole for the
36、 purpose of supplying cathodic protection. Electrolysis: The process that produces a chemical change in an electrolyte resulting from the passage of electricity. In this standard, electrolysis is the dissociation of an electrolyte by passage of direct current, which causes anions to migrate to the a
37、node and cations to the cathode. Elements released at the anode may include oxygen, chlorine, and other gases. Hydrogen is commonly released at the cathode. Electrolyte: A chemical substance containing ions that migrate in an electric field. For the purpose of this standard, electrolyte refers to th
38、e soil or liquid, including the moisture and other chemicals dissolved therein, within which a groundbed and a metallic structure are buried or submerged. End Effect: The more rapid loss of anode material at the end of an anode, compared with other surfaces of the anode, resulting from higher curren
39、t density. The end effect does not occur on all impressed current anodes used in deep anode beds. Foreign Structure: Any metallic structure that is not intended as a part of a system under cathodic protection. Gas Blockage: An envelopment of the anode by oxygen, chlorine, or other gas in sufficient
40、volume to reduce the anodes contact with the electrolyte, thereby increasing resistance and lowering the anodes current discharge. Ground Water: Water beneath the earths surface between saturated soil and rock that supplies wells and springs. Grout: A thin mortar used to fill cracks and crevices to
41、create a permanent, impervious, watertight bond. Hydrology: The scientific study of the properties, distribution, and effects of water on the earths surface, in the soil and underlying rocks, and in the atmosphere. Impressed Current: An electric current supplied by a device employing a power source
42、that is external to the electrode system. (An example is direct current for cathodic protection.) Lithology: The microscopic study, description, and classification of rock. Notch Propagation: The tendency of a cut, nick, or scratch in a material to increase in depth or length when the material is st
43、ressed. Open Hole: An installation in which the anodes are surrounded only by an aqueous electrolyte. Packaged Anode: An anode that is supplied in a conductive container, typically metallic. The anode is centered in the container and surrounded with a conductive backfill. Packaged anodes in metallic
44、 containers should be in electrical contact with the container through an internal wire arrangement. The container is electrochemically consumed during current activation. Potable Water: Water that is considered safe for use and consumption by the general public. Reference Electrode: An electrode wh
45、ose open-circuit potential is constant under similar conditions of measurement, which is used for measuring the relative potentials of other electrodes. Replaceable Deep Anode Bed: A deep anode bed design that allows for the removal and subsequent replacement of components or backfill without drilli
46、ng a new hole. Resistance Profile Test: A log of resistance versus depth in the drilled hole for a deep anode bed. Seal: The use of bentonite or grout to prevent the flow, migration, or movement of fluids into ground water. Shallow Groundbed: One or more anodes installed either vertically or horizon
47、tally at a nominal depth of less than 15 m (50 ft) for the purpose of supplying cathodic protection. Spoils: Waste material or fluid generated during the installation of a deep anode bed. Stratigraphy: The study of rock strata, especially of their distribution, deposition, and age. Surface Casing: A
48、 casing in the upper nonactive portion of the deep well that holds back unstable surface soils or functions as a portion of the fluid mitigation design. Test Hole: Any excavation constructed for the purpose of determining the geologic, hydrologic, and water quality SP0572-2007 NACE International 3 characteristics of underground formations. Vent Pipe: A nonmetallic pipe installed along the length of the deep groundbed to assist in the removal of gases. The vent
