1、StandardTest MethodMeasurement of Protective Coating ElectricalConductance on Underground PipelinesThis NACE International standard represents a consensus of those individual members who havereviewed this document, its scope, and provisions. Its acceptance does not in any respectpreclude anyone, whe
2、ther he 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, byimplication or otherwise, to manufact
3、ure, sell, or use in connection with any method, apparatus, orproduct covered by Letters Patent, or as indemnifying or protecting anyone against liability forinfringement of Letters Patent. This standard represents minimum requirements and should in noway be interpreted as a restriction on the use o
4、f better procedures or materials. Neither is thisstandard intended to apply in all cases relating to the subject. Unpredictable circumstances maynegate the usefulness of this standard in specific instances. NACE International assumes noresponsibility for the interpretation or use of this standard by
5、 other parties and acceptsresponsibility for only those official NACE International interpretations issued by NACE Internationalin accordance with its governing procedures and policies which preclude the issuance ofinterpretations by individual volunteers.Users of this NACE International standard ar
6、e responsible for reviewing appropriate health, safety,environmental, and regulatory documents and for determining their applicability in relation to thisstandard prior to its use. This NACE International standard may not necessarily address allpotential health and safety problems or environmental h
7、azards associated with the use ofmaterials, equipment, and/or operations detailed or referred to within this standard. Users of thisNACE International standard are also responsible for establishing appropriate health, safety, andenvironmental protection practices, in consultation with appropriate re
8、gulatory authorities ifnecessary, to achieve compliance with any existing applicable regulatory requirements prior to theuse of this standard.CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may berevised or withdrawn at any time without prior notice. NACE Internat
9、ional requires that action betaken to reaffirm, revise, or withdraw this standard no later than five years from the date of initialpublication. The user is cautioned to obtain the latest edition. Purchasers of NACE Internationalstandards may receive current information on all standards and other NAC
10、E Internationalpublications by contacting the NACE International Membership Services Department, 1440 SouthCreek Dr., Houston, Texas 77084-4906 (telephone +1 (281) 228-6200).Approved 2002-06-21NACE International1440 South Creek Dr.Houston, Texas 77084-4906+1 (281)228-6200ISBN 1-57590-155-2 2002, NAC
11、E InternationalNACE Standard TM0102-2002Item No. 21241TM0102-2002NACE International i_ForewordThis standard test method presents guidelines and procedures for use primarily by corrosioncontrol personnel in the pipeline industry to determine the general condition of a pipeline coating.These technique
12、s are used to measure the coating conductance (inverse of coating resistance) onsections of underground pipelines. This test method applies only to pipe coated with dielectriccoatings.When surveying a coated pipeline system, it may be necessary to determine the conductance ofthe coating. The conduct
13、ance of a coating can vary considerably along the pipeline. Variationsmay be caused by changes in average soil resistivity, terrain, and quality of construction. To obtaindata for coating conductance calculations, interrupted pipe-to-soil potentials and line currentreadings are taken at pre-selected
14、 intervals. It should be noted that the average soil resistivity hasa direct effect on the coating conductance measurement. Because soil resistivity can affect thecoating conductance, it must be known when evaluating a section of a pipeline coating.This standard was prepared by NACE Task Group 030 o
15、n Coating Conductance. This Task Groupwas administered by Specific Technology Group (STG) 03 on Protective Coatings and LiningsImmersion/Buried. Sponsoring STGs also included STG 05 on Cathodic/Anodic Protection; STG35 on Pipelines, Tanks, and Well Casings; and STG 62 on Testing and Monitoring Proce
16、dures.This standard is issued by NACE under the auspices of STG 03.In NACE standards, the terms shall, must, should, and may areusedinaccordancewiththedefinitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shalland must are used to state mandatory requirements.
17、 Should is used to state something consideredgood and is recommended but is not mandatory. May is used to state something considered optional._TM0102-2002ii NACE International_NACE InternationalStandardTest MethodMeasurement of Protective Coating Electrical Conductance onUnderground PipelinesContent
18、s1. General . 12. Definitions . 13. General Method 24. Attenuation Methods . 45. Normalizing Specific Coating Conductance to Evaluate Coating Condition. 6References 7Appendix AProcedure for Calibrating Four Wire Test Stations. 7Appendix BStandard Pipe Data Tables 9Appendix CExample of Coating Conduc
19、tance Test Procedure Using the GeneralMethod 12Figure 1Test Schematic 2Figure A1Diagram for Calibrating Four (4) Wire Stations . 7Figure C1Test Schematic 12Table 1Soil Resistivity Data 3Table 2Recorded Data, Calculated Potential and Current Changes 3Table 3Calculated Conductance Data 4Table 4Specifi
20、c Coating Conductance Normalized for 1,000 -cm Soil 6Table 5Table of Specific Coating Conductance vs. Coating Quality for1,000 -cm Soil 6Table B1Standard Pipe Formula. 9Table C1Soil Resistivity Data 12Table C2Recorded Data, Calculated Potential, and Current Changes 12Table C3Calculated Conductance D
21、ata 13Table C4Specific Coating Conductance Normalized for 1,000 -cm Soil 13_TM0102-2002NACE International 1_Section 1: General1.1 Protective coating conductance measurements areused to determine the general condition of the coating. Var-ious methods and techniques are used to measure the con-ductanc
22、e on sections of underground pipelines. The effect-ive coating conductance for a section of line tested isexpressed in terms of siemens (formerly Mho) or microsiemens (10-6siemens). The test segments involve shortand long sections along with single and multiple pipelines.Conductance tests are perfor
23、med whenever a significantchange in pipe-to-soil (P/S) potentials and current require-ments occurs and on newly installed pipelines, once backfillsettles and compacts (a minimum of one year).1.2 Coating conductance is dependent on soil resistivity,pipeline polarization level, and coating factors suc
24、h as type,age, thickness, degree of damage, and quality of inspectionduring installation of the pipeline. When specific areas withhigher (deteriorated coating) conductance values are foundon a given section of pipeline, this information assists inmitigating the problem.1.3 Test data may be taken at
25、intervals of approximately1.6 km (1.0 mile) or at each calibrated line current test sta-tion. To maximize the resolution and accuracy of the linecurrent and pipe-to-soil potential measurements, the mostinfluencing current source shall be cyclically interrupted.Attenuation current curves may be plott
26、ed on log log orsemilog graphs to serve as a reference in order to makecomparisons to other surveys in the determination of thelong-term performance of the coating.1.4 Voltmeters, data loggers, interrupters, test wires, reels,and electrodes are usually used to perform conductancetests. In addition,
27、four-wire calibrated pipeline test stationsare recommended to obtain accurate data (Refer toAppendix A). Insulated probes may be used as temporaryline current test stations. Standard pipe data tables (Referto Appendix B) are used to calculate line current factors.Appendix C includes an example of th
28、e coating conduct-ance test procedure using the general method.1.5 For the section of pipeline under test, the presence ofgalvanic anodes, shorted casings, shorted or poorly coatedvalves, poorly coated pipeline segments, etc., adverselyaffects the accuracy of the calculated specific coatingconductan
29、ce.1.6 For identifying a change in coating conductance, allperiodic coating conductance tests must be performed inthe same location._Section 2: DefinitionsAttenuation: Electrical losses in a conductor caused bycurrent flow in the conductor.Attenuation Method: The calculation of leakage conduct-ance
30、(g) for a section of pipe using the attenuation constant() for the section of pipe under test.Coating Conductance (g): The inverse of resistance (1/R)expressed as siemens (S). Conductance (g) for a length ofpipe between test sites is calculated by the attenuation orgeneral method. Conductance is aff
31、ected by:Physical characteristics and condition of the coatingResistivity of the earthContact between pipe and electrolytePolarizationCoating Resistance (R): The opposition of current from astructure to the earth.CSE: Saturated copper-copper sulfate reference electrode.Dielectric Coating: A coating
32、that does not conduct elec-tricity.Duty Cycle: A current interruption cycle expressed as theratio of the “on” time/total time per cycle. A minimum 75%duty cycle is recommended to limit depolarization.Dynamic Stray Current: A direct current in the pipelineunder test that originates from a source othe
33、r than the cath-odic protection system, and varies in magnitude or directionwith time. This also includes geomagnetically induced cur-rents (telluric current).Electrically Remote: A location on the soil surface wherethe voltage gradient produced by the test current is neg-ligible.General Method: The
34、 calculation of coating leakage con-ductance (g) for a section of pipe using the proportion of thetest current (I) in the test section divided by the averagepotential change (Vavg).Leakage Current: The average current measured in a sec-tion of pipe under testing.Longitudinal Resistance (r): The pipe
35、 resistance for alength of section.TM0102-20022 NACE InternationalMultiple Line: More than one pipeline in close proximity,electrically continuous to the other parallel pipeline(s), andcathodically protected.Single Line: A pipeline that is electrically isolated fromother parallel pipelines and catho
36、dically protected.Specific Coating Conductance (G): The average coatingconductance, calculated by dividing the conductance (g) fora section of pipe by the surface area of the pipe section,expressed in siemens/unit area.Telluric Current: Current induced on a pipeline because ofchanges in the earths e
37、lectromagnetic field._Section 3: General Method3.1 Test Arrangement3.1.1 The change in potential (V) measured at var-ious locations along a length of pipeline, as illustratedin Figure 1, can be used to determine the specificcoating leakage conductance (G) if the leakage currentmeasured (I1,2,3) in e
38、ach section of pipe is also known.The leakage current (I1) is determined by measuringthe pipe current at each test location and calculatingthe difference between the pipe current entering andleaving each test section. (See Appendix C for addi-tional details.)Section 3InterrupterI2VVaVbVVcVVdVIdIcIbI
39、aSection 1 Section 2I1I2I3Rectifier orTemporaryPower SupplyITab c dFIGURE 1: Test Schematic3.2 Interruption and Adjustment of Test Current3.2.1 The interrupter shall be set up at the most influ-encing current source for the section of pipeline to betested.3.2.2 The interrupter shall be set at a mini
40、mum dutycycle of 75% to prevent depolarization during testing.Example:Slow Cycle:“On” 3.00 Seconds, “Off” 1.00 SecondsFast Cycle:“On” 0.75 Seconds, “Off” 0.25 Seconds3.2.3 The test current (IT) output shall be adjusted sothat the instant “off” potential at the test location near-est to the test curr
41、ent source is less negative than1,100 mVCSE.Cautionary Note 1: If the instant “off” potential is morenegative than 1,100 mVCSEan error is introduced be-cause it no longer depends on the relationship betweenpotential and current.3.3 Soil Resistance Measurements and Calculation of SoilResistivity3.3.1
42、 The soil resistance at each test location shall bemeasured and recorded using the Wenner four-pinmethod (ASTM(1)G571) with the pin spacing equal tothe pipe depth.Cautionary Note 2: To minimize errors in the soilresistance measurements, the pins should be alignedperpendicular to the pipe, and the se
43、paration distancebetween the pipe and the nearest pin should be equalto or greater than the pin spacing. If required, soil con-ditions, such as wetness or dryness, and ground temp-erature should be recorded at the time of survey.3.3.2 The soil resistivity () at each test site shall becalculated acco
44、rding to Equation (1): =2 sR (1)where = soil resistivity (-cm)s = pin spacing and pipe depth (cm)R = resistance indicated on meter ()3.3.3 The average soil resistivity in each test sectionshall be calculated according to Equation (2):_(1)ASTM International, 100 Barr Harbor Drive, West Conshohocken,
45、PA 19428.TM0102-2002NACE International 32baavg,1+= (2)whereavg,1= average soil resistivity in the firstsection (-cm)a= soil resistivity at test point Ab= soil resistivity at test point B3.3.4 The data from Paragraphs 3.3.1, 3.3.2, and 3.3.3shall be recorded in Table 1.3.4 Pipe-to-Soil Potential and
46、Current Measurements andShift Calculations3.4.1 The “on” and “off” pipe-to-soil potential and pipecurrent shall be measured and recorded at two or morelocations on the pipeline. The groundbed of the inter-rupted current source must be located electricallyremote from the section of pipe being tested
47、so that theinfluence of the groundbed voltage gradient on thepotential measurements is negligible.TABLE 1: Soil Resistivity DataTestSitePipe Depth/Pin Spacing(cm in.)Soil ResistanceReading () (fromParagraph 3.3.1)Soil Resistivity at TestSite ( =2sR)(-cm)(from Paragraph 3.3.2)SectionNo.Average SoilRe
48、sistivity avg(-cm) (fromParagraph 3.3.3)Cautionary Note 3: The reference electrode shallalways be a minimum distance of one pipe diameterfrom the pipeline. The reference may be placed remotefrom the pipe being tested if direct current (DC) flow inthe earth to other structures does not affect the poten-tial measurement. This ma
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