StandardTest Method

Measurement of Protective Coating ElectricalConductance on Underground Pipelines

This 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, whether 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 manufacture, 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 of 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 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.

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ISBN 1-57590-155-2© 2002, NACE International

NACE Standard TM0102-2002Item No. 21241

TM0102-2002

NACE International i

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Foreword

This 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 techniques 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 conductance 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 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 on Coating Conductance. This Task Groupwas administered by Specific Technology Group (STG) 03 on Protective Coatings and Linings—Immersion/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 Procedures.This standard is issued by NACE under the auspices of STG 03.

In NACE standards, the terms shall, must, should, and may are used in accordance with thedefinitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shalland must are used to state mandatory requirements. Should is used to state something consideredgood and is recommended but is not mandatory. May is used to state something considered optional.

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TM0102-2002

ii NACE International

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NACE InternationalStandard

Test Method

Measurement of Protective Coating Electrical Conductance onUnderground Pipelines

Contents

1. General ......................................................................................................................... 12. Definitions ..................................................................................................................... 13. General Method ............................................................................................................ 24. Attenuation Methods ..................................................................................................... 45. Normalizing Specific Coating Conductance to Evaluate Coating Condition................. 6References.......................................................................................................................... 7Appendix A—Procedure for Calibrating Four Wire Test Stations....................................... 7Appendix B—Standard Pipe Data Tables .......................................................................... 9Appendix C—Example of Coating Conductance Test Procedure Using the General

Method ........................................................................................................................ 12Figure 1—Test Schematic .................................................................................................. 2Figure A1—Diagram for Calibrating Four (4) Wire Stations ............................................... 7Figure C1—Test Schematic.............................................................................................. 12Table 1—Soil Resistivity Data ............................................................................................ 3Table 2—Recorded Data, Calculated Potential and Current Changes .............................. 3Table 3—Calculated Conductance Data ............................................................................ 4Table 4—Specific Coating Conductance Normalized for 1,000 Ω-cm Soil ........................ 6Table 5—Table of Specific Coating Conductance vs. Coating Quality for

1,000 Ω-cm Soil ............................................................................................................ 6Table B1—Standard Pipe Formula..................................................................................... 9Table C1—Soil Resistivity Data........................................................................................ 12Table C2—Recorded Data, Calculated Potential, and Current Changes ........................ 12Table C3—Calculated Conductance Data........................................................................ 13Table C4—Specific Coating Conductance Normalized for 1,000 Ω-cm Soil.................... 13

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Section 1: General

1.1 Protective coating conductance measurements areused to determine the general condition of the coating. Var-ious methods and techniques are used to measure the con-ductance 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 (10-6 siemens). The test segments involve shortand long sections along with single and multiple pipelines.Conductance tests are performed 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 such 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 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 most

influencing current source shall be cyclically interrupted.Attenuation current curves may be plotted 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, 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 the 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 coatingconductance.

1.6 For identifying a change in coating conductance, allperiodic coating conductance tests must be performed inthe same location.

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Section 2: Definitions

Attenuation: Electrical losses in a conductor caused bycurrent flow in the conductor.

Attenuation Method: The calculation of leakage conduct-ance (g) for a section of pipe using the attenuation constant(α) 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 affected by:

Physical characteristics and condition of the coatingResistivity of the earthContact between pipe and electrolytePolarization

Coating Resistance (R): The opposition of current from astructure to the earth.

CSE: Saturated copper-copper sulfate reference electrode.

Dielectric Coating: A coating 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 other 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 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 resistance for alength of section.

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Multiple 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 cathodically 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 earth’s electromagnetic field.

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Section 3: General Method

3.1 Test Arrangement

3.1.1 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 current

measured (I1,2,3) in each 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 3

Interrupter

I2

V

Va Vb

V

Vc

V

Vd

V

IdIcIbIa

Section 1 Section 2

I1 I2 I3

Rectifier orTemporaryPower Supply

IT

a b c d

FIGURE 1: Test Schematic

3.2 Interruption and Adjustment of Test Current

3.2.1 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 minimum 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 Seconds

3.2.3 The test current (IT) output shall be adjusted sothat the instant “off” potential at the test location near-est to the test current source is less negative than–1,100 mVCSE.

Cautionary Note 1: If the instant “off” potential is morenegative than –1,100 mVCSE an error is introduced be-cause it no longer depends on the relationship betweenpotential and current.

3.3 Soil Resistance Measurements and Calculation of SoilResistivity

3.3.1 The soil resistance at each test location shall bemeasured and recorded using the Wenner four-pinmethod (ASTM(1) G 571) 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 separation 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 (ρ) at each test site shall becalculated according to Equation (1):

ρ = 2 πs R (1)

whereρ = soil resistivity (Ω-cm)s = pin spacing and pipe depth (cm)R = resistance indicated on meter (Ω)

3.3.3 The average soil resistivity in each test sectionshall be calculated according to Equation (2):

2 NACE International

___________________________(1) ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

TM0102-2002

2

ρρρ ba

avg,1

+= (2)

whereρavg,1 = average soil resistivity in the first

section (Ω-cm)ρa = soil resistivity at test point Aρb = soil resistivity at test point B

3.3.4 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 Current Measurements andShift Calculations

3.4.1 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 so that theinfluence of the groundbed voltage gradient on thepotential measurements is negligible.

TABLE 1: Soil Resistivity Data

TestSite

Pipe Depth/Pin Spacing

(cm [in.])

Soil ResistanceReading (ΩΩΩΩ) (fromParagraph 3.3.1)

Soil Resistivity at TestSite (ρρρρ = 2ππππs R) (ΩΩΩΩ-cm)(from Paragraph 3.3.2)

SectionNo.

Average SoilResistivity ρρρρavg

(ΩΩΩΩ-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 may not be applicable whenparallel piping is less than the minimum distance fromthe reference electrode.

Cautionary Note 4: In dynamic stray current areas,simultaneous measurements of the pipe-to-soil poten-tial and current at both ends of the test section arerecommended in order to minimize errors.

3.4.2 The change in potential (∆V) at each test loca-tion shall be calculated according to Equation (3), anexample for test point “a”:

∆Va = Va,on – Va,off (V) (3)

3.4.3 The change in pipe current (∆I) at each test loca-tion shall be calculated according to Equation (4), anexample for the test point “a.” (A procedure for cali-brating current spans is outlined in Appendix A.)

∆Ia = I a,on – I a,off (A) (4)

Cautionary Note 5: The current magnitudes betweentest locations and between “on” and “off” conditionsmust be significantly different. Otherwise, a large erroris introduced.

3.4.4 Steps in Paragraphs 3.4.2 and 3.4.3 shall be re-peated for each test location and the results entered inTable 2. The ratio of potential shifts from each end ofeach test section shall be calculated according toEquation (5):

4)NoteCautionary(seeV

VRatio

b

a

∆

∆= (5)

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TABLE 2: Recorded Data, Calculated Potential, and Current Changes

P/S Potentials (V) Pipe Current (A)Test Site LocationKm (mile) Von Voff ∆∆∆∆V (from

Paragraph3.4.2)

Ratio∆∆∆∆V Ion Ioff ∆∆∆∆I (from

Paragraph3.4.3)

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Cautionary Note 6: If the ratio of the ∆V potentialsfrom each pair of adjacent test locations is between 1.6and 0.625, then the arithmetic mean of the two can betaken as the average potential change in the section ofpipeline between these test locations.2 However, if theratio is outside this range, then one or more intermed-iate locations should be selected for the potentialmeasurements until the ratio between two successivevalues is between 1.6 and 0.625. Alternatively, one ofthe attenuation methods outlined in Section 4 can beused.

3.4.5 The average change in pipe-to-soil potential(∆Vavg) and current pick-up (∆I) for each test sectionshall be calculated according to Equations (6) and (7).

2

V∆V∆∆V ba

(avg,1)

+= (6)

and ∆I1 = ∆Ia - ∆Ib (7)

where∆Vavg,1 = average change in potential in section

1 caused by test current∆I1 = change in current in section 1 caused

by test current

3.4.6 The conductance (g) for the section of pipe beingtested shall be calculated using Equation (8).

(S)∆V

∆Ig

avg,1

11

= (8)

whereg1 = conductance for the first section of pipe (S)

3.4.7 The average specific conductance (G) shall becalculated using Equation (9):

area)unit/(SA

gG

1

11 = (9)

whereG1 = average specific conductance for the first

section of coated pipe (S/unit area)A1 = surface area of pipe section between the

test locations in the first section of pipe inm2 (ft2)

= πd L

whered = pipe outside diameter in m (ft) from Table

B1, Appendix BL = length of the first pipe section in m (ft)

3.4.8 Data from Paragraphs 3.4.5, 3.4.6, and 3.4.7shall be recorded in Table 3.

TABLE 3: Calculated Conductance Data

PipeSection

SectionLength

Average PotentialChange in Section(from Paragraph

3.4.5)

Current Pick-Up in Section

(fromParagraph

3.4.5)

Conductance g(S/section )

(fromParagraph

3.4.6)

Pipe SurfaceArea in Section

(fromParagraph

3.4.7)

Average SpecificConductance G

(S/Unit Area)(from Paragraph

3.4.7)

Note: Refer to Table B1, Appendix B, to obtain pipe surface area data.

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Section 4: Attenuation Methods

4.1 When there is measurable attenuation of the pipe-to-soil potential and line current with distance along the pipe-line, coating conductance (g) can be determined alter-natively using the attenuation constant α because, accord-ing to Equation (10):3

gxrα = (10)

whereα = dimensionless attenuation constant for length

of pipe being testedr = the longitudinal resistance of the pipe for the

length being tested (Ω) (see Table B1)g = coating conductance of length of pipe being

tested (S)

therefore

rα

g2

= (10)

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4.2 Potential Attenuation Method

4.2.1 With the current interrupted, the “on” and “off”pipe-to-soil potential shall be measured and recordedat two locations, “a” and “b,” at each end of the pipelinesection being tested, as illustrated in Figure 1.

4.2.2 The shift in pipe-to-soil potential at each testlocation shall be calculated according to Equations (3a)and (3b):

∆Va = Va,on - Va,off (V) (3a)

∆Vb = Vb,on - Vb,off (V) (3b)

Cautionary Note 7: Test locations must be sufficientlyremote from the rectifier or groundbed location so thatthe influence of the groundbed voltage gradient is neg-ligible.

4.2.3 The attenuation constant (α) shall be calculatedusing Equation (11).4 An interrupted current is drainedand P/S potentials are taken at two points. One istaken at a distance far enough from the drain point toavoid the anode proximity effect and the other is takenat a point to obtain a reading usable for Equation (11).This is known as the long line method.

=

b

a

∆V

∆V1nLα (11)

therefore

L

∆V

∆V1n

α b

a

= (11)

whereL = length of pipe section between test loca-

tions “a” and “b” in m (ft)α = attenuation constant for the section of

pipe

4.2.4 The conductance (g) for the pipe section shall becalculated using Equation (10):

rα

g2

= (10)

wherer = longitudinal resistance of pipe section of

length “L” (Ω) (Table B1)g = leakage conductance of pipe section (S)α = attenuation constant

4.2.5 The average specific conductance (G) shall becalculated using Equation (12):

Ag

G = (12)

whereg = conductance of coated pipe section

having length “L” (S)G = average specific conductance of coated

pipe section (S/unit area)A = surface area of pipe section in m2 (ft2)

having length “L”

4.3 Current Attenuation Method

4.3.1 The pipe current shall be measured andrecorded at two points, “a” and “b,” that are “L” distanceapart on the pipeline with the test current interrupted.(A procedure for calibrating a current span is outlined inAppendix A.)

4.3.2 The change in current ∆Ia and ∆Ib when location“a” is closer to the test current source than location “b”shall be calculated using Equations (4a) and (4b).(See Figure 1.)

∆Ia = Ia,on - Ia,off (4a)

∆Ib = Ib,on - Ib,off (4b)

4.3.3 The attenuation constant (α) shall be calculatedusing Equation (13).5 This method is based on obtain-ing measurements for total current flow to a givensection, the average potential shift in that section dueto the current, and the length of the section. A currentratio of 2:1 and a potential shift no greater than 1.6:1are recommended. If these limits are not met, theinterval must be shortened or lengthened. This is alsoknown as the general method.

=

b

a

∆I

∆I1nLα (13)

therefore

L

∆I

∆I1n

α b

a

= (13)

whereL = length of pipe section between test points

“a” and “b” in m (ft)α = attenuation constant for pipe section

having length “L”

4.3.4 The conductance (g) for the pipe section shall becalculated using Equation (10):

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rα

g2

= (10)

wherer = longitudinal resistance of pipe length “L”

(Ω)g = conductance of pipe length “L” (S)α = attenuation constant for pipe section

having length “L”

4.3.5 The average specific conductance (G) shall becalculated using Equation (12):

Ag

G = (12)

whereg = conductance of coated pipe section

having length “L” (S)G = average specific conductance of coated

pipe section (S/unit area)A = surface area of pipe section in m2 (ft2)

having length “L”

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Section 5: Normalizing Specific Coating Conductance to Evaluate Coating Condition

5.1 The calculated specific coating conductance obtainedby any of the foregoing methods is, in part, a function of thesoil resistivity. For a more accurate coating quality com-parison, the specific coating conductance must be corrected(normalized) for a specific soil resistivity, such as 1,000 Ω-cm.

5.2 The normalized specific coating conductance (Gn) for1,000 Ω-cm soil shall be calculated using Equation (14):

cm-1,000

ρxGG

avg,11n Ω

= (14)

whereGn = normalized specific conductance in 1,000 Ω-

cm soilG1 = average specific conductance for the first

section of pipe (S/unit area)ρavg,1 = average soil resistivity in the first section (Ω-

cm)

5.3 The data shall be recorded in Table 4.

5.4 To estimate coating quality, the calculated normalizedspecific conductance value shall be compared to the valuein Table 5.

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TABLE 4: Specific Coating Conductance Normalized for 1,000 ΩΩΩΩ-cm Soil

TestSection

Average Soil Resistivityρρρρavg (ΩΩΩΩ-cm) (from Table B1,

Appendix B)

Specific Conductance(G) µµµµS/unit area (from

Table 3)

Normalized SpecificCoating Conductance

(Gn) µµµµS/unit area

EstimatedCoating Quality(from Table 5)

TABLE 5: Table of Specific Coating Conductance vs. Coating Quality6,7,8 for 1,000 ΩΩΩΩ-cm Soil

Coating Normalized Specific Conductance Range (Gn)

Quality (µS/m2) (µS/ft2)Excellent < 100 < 10

Good 101 to 500 10 to 50Fair 501 to 2,000 51 to 200Poor > 2,000 > 200

Note: Conductance values for directionally drilled pipe sections can also be related to % bare.9

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References

1. ASTM G 57 (latest revision), “Standard Test Method forField Measurement of Soil Resistivity Using the WennerFour-Electrode Method,” (West Conshocken, PA: ASTM).

2. M.E. Parker, E.G. Peattie, Pipeline Corrosion andCathodic Protection, 3rd ed. (Houston, TX: Gulf PublishingCo., 1984), p. 141.

3. R. Pope, “Attenuation of Forced Drainage Effects onLong Uniform Structures,” MP 20, 12 (1981): p. 29.

4. M.E. Parker, E.G. Peattie, Pipeline Corrosion andCathodic Protection, 3rd ed. (Houston, TX: Gulf PublishingCo., 1984), p. 141.

5. M.E. Parker, E.G. Peattie, Pipeline Corrosion andCathodic Protection, 3rd ed. (Houston, TX: Gulf PublishingCo., 1984), p. 142.

6. Cathodic Protection Design 1 (Houston, TX: NACE,1992), p. 5:16.

7. V.A. Pritula, “Cathodic Protection of Pipelines and Stor-age Tanks,” Department of Scientific and IndustrialResearch, USSR, English Translation, Her Majesty’sStationery Office, London, 1954, p. 26.

8. W.H. Seager, “The Evaluation of Pipeline Coatings inTerms of In-Situ Electrical Characteristics,” MP 19, 6 (1980):p. 13.

9. R.A. Gummow, S.M. Segall, “In-Situ Evaluation ofDirectional Drill/Bore Coating Quality—Evaluation of TestMethods,” PRC International Corrosion Supervisory Com-mittee, Final Report, Contract No. PR-262-9738, Oct. 1998.

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Appendix A: Procedure for Calibrating Four Wire Test Stations

1. Measure and record initial voltage between terminals 2and 3 as shown in Figure A1. Note voltage polarity.

2. Apply a test current, between test leads 1 and 4.

Assumed Current Flow

FIGURE A1: Diagram for Calibrating Four Wire Stations

Outside Terminals 1 and 4 for Calibration

Inside Terminals 2 and 3for Line CurrentMeasurements

3. Measure and record change in voltage betweenterminals 2 and 3 with the test current applied.

4. Determine the difference between current “on” andcurrent “off.”

5. Calculate resistance in span: Rp = ∆V/∆I.

6. Steps 3, 4, and 5 can be repeated with different currentamounts to verify results.

Example

1. Measure and record initial voltage between terminals 2and 3 with positive lead on 2 = +0.52 mV.

2. Apply 10 A between terminals 1 and 4 with positivelead on 1.

3. Measure mV drop between terminals 2 and 3 as inFigure A1. Determine the difference using Equation (A1) bysubtracting the “off “from the “on.”

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Current “on” +5.32 mV (A1)Current “off” +0.53 mVDifference [∆V] +4.79 mV

4. Calculate resistance in the pipe span using Equation(A2).

Rp = ∆V/∆I (A2)Rp = 0.00479 V/10 ARp = 0.000479 Ω

5. Apply 20 A between terminals 1 and 4 with positivelead on 1.

6. Measure mV drop between 2 and 3 using Equation(A1).

Current “on” +9.95 mV (A1)Current “off” +0.53 mVDifference [∆V] +9.42 mV

7. Calculate resistance using Equation (A2).

Rp = ∆V/∆I (A2)Rp =0.00942 V/20 ARp = 0.000471 Ω

8. Using average of 0.000475 Ω

V =I x Rp

I =V/Rp

I = 0.00045 V/0.000475 ΩI = 0.95 A

I or amps found in step 1 = 0.95 A. Line current is inthe positive direction.

9. Record

I = 0.95 A

Pipe Resistance Factor for Span = 0.475 mV/A orPipe Conductance Factor for Span = 2.105 A/mVTerminal 2 is positiveTerminal 3 is negative

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9

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al ExternalArea,ft2/ft

ExternalArea,m2/km

ExternalArea,

ft2/mile

99 0.65 199.5 3,45629 0.75 229.4 3,97479 0.92 279.3 4,83859 1.18 359.1 6,220

29 1.73 528.7 9,158

88 2.26 688.2 11,920

58 2.81 857.8 14,860

17 3.34 1,017 17,620

17 3.67 1,117 19,350

77 4.19 1,277 22,120

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Appendix B: Standard Pipe Data Tables

TABLE B1: Standard Pipe Formula

OutsideDiameter(OD), cm

OD,in.

Wall Thickness,mm

Wall Thickness,in.

Weight,kg/m

Weight,lb/ft µΩΩΩΩ/m µΩΩΩΩ/ft A/mV/m A/mV/ft

ExternArea,m2/m

6.350 2.500 5.232 0.206 8.616 5.790 122.281 37.271 8.178 26.830 0.17.303 2.875 7.010 0.276 11.399 7.660 92.429 28.172 10.819 35.496 0.28.890 3.500 5.486 0.216 11.280 7.580 93.404 28.470 10.706 35.125 0.2

11.430 4.500 6.020 0.237 16.057 10.790 65.617 20.000 15.240 50.000 0.38.560 0.337 22.293 14.980 47.263 14.406 21.158 69.416

16.828 6.625 5.563 0.219 22.278 14.970 47.295 14.415 21.144 69.370 0.57.112 0.280 28.230 18.970 37.322 11.376 26.794 87.9057.925 0.312 31.355 21.070 33.603 10.242 29.760 97.6379.525 0.375 37.249 25.030 28.286 8.622 35.353 115.987

10.973 0.432 42.532 28.580 24.773 7.551 40.367 132.43721.908 8.625 6.350 0.250 33.275 22.360 31.664 9.651 31.582 103.614 0.6

7.938 0.313 33.841 22.740 31.135 9.490 32.118 105.3758.179 0.322 42.487 28.550 24.799 7.559 40.325 132.2989.525 0.375 49.169 33.040 21.429 6.531 46.666 153.105

27.305 10.750 6.350 0.250 41.728 28.040 25.250 7.696 39.604 129.935 0.89.271 0.365 60.241 40.480 17.490 5.331 57.175 187.5819.525 0.375 61.833 41.550 17.040 5.194 58.686 192.539

11.125 0.438 71.714 48.190 14.692 4.478 68.064 223.30912.700 0.500 81.462 54.740 12.934 3.942 77.316 253.661

32.385 12.750 6.350 0.250 49.675 33.380 21.210 6.465 47.147 154.680 1.07.137 0.281 55.731 37.450 18.905 5.762 52.895 173.5407.938 0.313 61.773 41.510 17.056 5.199 58.630 192.3549.525 0.375 73.753 49.560 14.286 4.354 69.999 229.657

12.700 0.500 97.355 65.420 10.822 3.299 92.400 303.15135.560 14.000 6.350 0.250 54.630 36.710 25.605 7.804 39.055 128.133 1.1

7.925 0.312 67.979 45.680 20.577 6.272 48.598 159.4429.525 0.375 81.209 54.570 17.225 5.250 58.056 190.471

40.640 16.000 6.350 0.250 62.577 42.050 22.353 6.813 44.736 146.771 1.27.925 0.312 77.920 52.360 17.952 5.472 55.704 182.7579.525 0.375 93.129 62.580 15.020 4.578 66.577 218.429

NACE International

l ExternalArea,ft2/ft

ExternalArea,m2/km

ExternalArea,

ft2/mile

6 4.71 1,436 24,8806 5.24 1,596 27,650

6 5.76 1,756 30,4105 6.12 1,865 32,310

5 6.28 1,915 33,180

5 6.81 2,075 35,940

4 7.85 2,394 41,470

3 9.42 2,873 49,760

3 9.42 2,873 49,760

TM0102-2002

10

OutsideDiameter(OD), cm

OD,in.

Wall Thickness,mm

Wall Thickness,in.

Weight,kg/m

Weight,lb/ft µΩΩΩΩ/m µΩΩΩΩ/ft A/mV/m A/mV/ft

ExternaArea,m2/m

16.662 0.656 159.977 107.500 8.744 2.665 114.366 375.21845.720 18.000 6.350 0.250 70.524 47.390 19.835 6.046 50.417 165.410 1.4350.800 20.000 6.350 0.250 78.470 52.730 17.826 5.433 56.098 184.049 1.59

7.137 0.281 88.143 59.230 15.870 4.837 63.013 206.7367.925 0.312 84.393 56.710 16.575 5.052 60.332 197.9419.525 0.375 116.969 78.600 11.959 3.645 83.621 274.346

55.880 22.000 6.350 0.250 86.417 58.070 16.187 4.934 61.779 202.688 1.7559.373 23.375 9.525 0.375 137.193 92.190 10.196 3.108 98.079 321.780 1.86

11.913 0.469 170.751 114.740 8.192 2.497 122.069 400.48960.960 24.000 7.137 0.281 106.031 71.250 13.192 4.021 75.801 248.691 1.91

7.925 0.312 117.654 79.060 11.889 3.624 84.110 275.9518.738 0.344 129.246 86.850 10.823 3.299 92.397 303.141

10.312 0.406 152.343 102.370 9.182 2.799 108.909 357.31211.913 0.469 175.320 117.810 7.979 2.432 125.335 411.20412.700 0.500 186.749 125.490 7.490 2.283 133.506 438.01015.875 0.625 232.227 156.050 6.023 1.836 166.018 544.677

66.040 26.000 7.239 0.285 116.523 78.300 12.005 3.659 83.301 273.298 2.07

7.925 0.312 142.461 95.730 9.819 2.993 101.845 334.1368.255 0.325 132.624 89.120 10.547 3.215 94.812 311.0659.525 0.375 152.729 102.630 9.159 2.792 109.185 358.220

12.700 0.500 202.642 136.170 6.903 2.104 144.868 475.28876.2 30.000 7.925 0.312 147.447 99.080 9.487 2.892 105.409 345.829 2.39

8.255 0.325 153.116 102.890 9.136 2.785 109.462 359.1278.738 0.344 162.030 108.880 8.633 2.631 115.835 380.0359.144 0.360 169.590 113.960 8.248 2.514 121.239 397.7669.525 0.375 176.570 118.650 7.922 2.415 126.229 414.136

10.312 0.406 191.079 128.400 7.321 2.231 136.601 448.16811.125 0.438 205.559 138.130 6.805 2.074 146.953 482.12912.700 0.500 234.429 157.530 5.967 1.819 167.592 549.843

91.44 36.000 8.738 0.344 194.800 130.900 7.181 2.189 139.261 456.894 2.879.525 0.375 212.330 142.680 6.588 2.008 151.794 498.010

10.312 0.406 229.816 154.430 6.087 1.855 164.294 539.02311.913 0.469 264.713 177.880 5.284 1.611 189.242 620.87312.700 0.500 282.110 189.570 4.958 1.511 201.679 661.675

91.44 36.000 14.275 0.562 316.814 212.890 4.415 1.346 226.488 743.072 2.87

TM0102-2002

11

l ExternalArea,ft2/ft

ExternalArea,m2/km

ExternalArea,

ft2/mile

1 11.00 3,352 58,060

0 12.57 3,830 66,350

(B1)

(B2)

NACE International

OutsideDiameter(OD), cm

OD,in.

Wall Thickness,mm

Wall Thickness,in.

Weight,kg/m

Weight,lb/ft µΩΩΩΩ/m µΩΩΩΩ/ft A/mV/m A/mV/ft

ExternaArea,m2/m

15.875 0.625 351.398 236.130 3.981 1.213 251.213 824.18817.450 0.687 385.849 259.280 3.625 1.105 275.841 904.991

106.68 42.000 9.525 0.375 248.120 166.730 5.638 1.718 177.380 581.955 3.359.906 0.390 257.912 173.310 5.424 1.653 184.380 604.921

11.125 0.438 289.298 194.400 4.835 1.474 206.817 678.53412.700 0.500 329.835 221.640 4.241 1.293 235.797 773.61314.275 0.562 370.104 248.700 3.779 1.152 264.586 868.06315.875 0.625 411.058 276.220 3.403 1.037 293.863 964.119

121.92 48.000 12.700 0.500 377.515 253.680 3.705 1.129 269.884 885.445 3.8315.875 0.625 470.659 316.270 2.972 0.906 336.472 1,103.90919.050 0.750 563.297 378.520 2.483 0.757 402.698 1,321.187

The Standard Pipe Formula (Metric) is illustrated in Equation (B1):

Resistance (µΩ/m) = 58.55 (constant, k) x18 µΩcm for pipe diameter 32.38 cm (12.75 in.) and belowWeight (kg/m)

The Standard Pipe Formula (U.S. Customary) is illustrated in Equation (B2):

Resistance (µΩ/ft) = 11.98 (constant, k) x 18 µΩcm for pipe diameter 32.38 cm (12.75 in.) and belowWeight (lb/ft)

Where k = 77.76 (Metric Units), for pipe diameter 35.56 cm (14.00 in.) OD and aboveand k = 15.91 (U.S. Customary), for pipe diameter 35.56 cm (14.00 in.) OD and above

TM0102-2002

12 NACE International

________________________________________________________________________

Appendix C: Example of Coating Conductance Test Procedure Using the General Method

Tables C1 to C4 illustrate the coating conductance test procedure outlined in this standard for the arrangement depicted in FigureC1.

Section 3

Rectifier orTemporaryPower Supply

Interrupter

I2

V

Va Vb

V

Vc

V

Vd

V

6.8 km

IdIcIbIa

Section 1 Section 25.2 km3.0 km1.7 kmChainage (1.06 mi) (1.86 mi) (3.23 mi) (4.23 mi)

I1 I2 I3

.762m (30 in.)diameter

IT

a b c d

FIGURE C1: Test Schematic

TABLE C1: Soil Resistivity Data

Test SitePipe Depth/Pin Spacing,

cm (in.)

SoilResistance,

R

(ΩΩΩΩ)

SoilResistivity at

Test Site(ρρρρ = 2ππππs R)

SectionNo.

Average SoilResistivity

ρρρρ avg,

(ΩΩΩΩ-cm)

a 100 (39) 13.3 8,352 1 7,237

b 150 (59) 6.5 6,1232 4,710

c 250 (98) 2.1 3,297

d 125 (49) 4.5 3,533 3 3,415

Table C2: Recorded Data, Calculated Potential, and Current Changes

P/S Potentials (V) Pipe Current (A)TestSite

Distance,km (mile) Von Voff ∆∆∆∆V

Ratio∆∆∆∆V Ion Ioff ∆∆∆∆I

a 1.70 (1.06) -1.400 -1.000 0.400 3.0 1.4 1.6

1.14b 3.00 (1.86) -1.350 -1.000 0.350 2.9 1.4 1.5

1.40

c 5.20 (3.23) -1.200 -0.950 0.250 1.8 1.3 0.50.69

d 6.80 (4.23) -1.400 -1.040 0.360 1.65 1.20 0.45

Location0.762 m (30 in.)diameter

TM0102-2002

NACE International 13

TABLE C3: Calculated Conductance Data

PipeSection

SectionLength

Average PotentialChange in Section

Current Pick-Upin Section

Conductance,g (S)

Pipe Area inSection

(Table B1)

AverageSpecific

ConductanceG (µS/Unit

Area)

1 1,300 m(4,265 ft) 0.375

20.350400.0 =+ 1.6 – 1.5 = 0.1 0.266 3,112 m2

(33,481 ft2)85.5 µS/m2

(7.9 µS/ft2)

2 2,200 m(7,219 ft) 0.300

20.250350.0 =+ 1.5 – 0.5 = 1.0 3.33 5,267 m2

(56,672 ft2)632 µS/m2

(58.7 µS/ft2)

3 1,600 m(5,250 ft) 0.305

20.3600.250 =+ 0.5 – 0.45 = 0.05 0.164 3,830 m2

(41,209 ft2)42.8 µS/m2

(4.0 µS/ft2)

Note: Pipe Outside Diameter = 0.762 m (30 in.)Pipe Section Surface Area = πdL = 3.14 x 0.762 m x 1 m = 2.39 m2/lin m

= 3.14 x 30/12 x 1 ft = 7.85 ft2/lin ft

TABLE C4: Specific Coating Conductance Normalized for 1,000 ΩΩΩΩ-cm Soil

TestSection

AverageSoil Resistivity

ρρρρavg(ΩΩΩΩ-cm)(from Table C1,

Appendix C)

SpecificConductance (G)

µµµµS/m2

(from Table C3Appendix C)

NormalizedSpecificCoating

Conductance (Gn)µµµµS/m2

EstimatedCoating Quality(from Table 5)

1 7,238 85.5 619 Fair

2 4,710 632 2,976 Poor

3 3,415 42.8 146 Good