G62_14_Standard Test Methods for Holiday Detection in Pipeline Coatings

November 7, 2018 | Author: Syed Fadzil Syed Mohamed | Category: High Voltage, Pipe (Fluid Conveyance), Voltage, Pipeline Transport, Electromagnetism
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Designation: G62 − 14

Standard Test Methods for

Holiday Detection in Pipeline Coatings 1 This standard is issued under the fixed designation G62; the number immediately following the designation indicates the year of original adoption adopt ion or, in the case of revis revision, ion, the year of last revision. A number in parentheses parentheses indicates indicates the year of last reapproval. reapproval. A super superscrip scriptt epsilon (´) indicates an editorial change since the last revision or reapproval.

1. Sco Scope pe

2. Referenc Referenced ed Documents 2.1   ASTM Standards: 3 A742/A742M Specificatio A742/A742M  Specification n for Steel Sheet, Metallic Coated and Polymer Precoated for Corrugated Steel Pipe

1.1 These test methods cover the apparatus and procedure procedure for detecting holidays in pipeline type coatings. 1.2 Met Method hod A is des design igned ed to det detect ect holidays holidays such as pin pin-holes and voids in thin-film coatings from 0.025 to 0.254 mm (1 to 10 mils) in thickness using ordinary tap water and an applied voltage of less than 100 V d-c. It is effective on films up to 0.508 mm (20 mils) thickness if a wetting agent is used with the water. It should be noted, however, that this method will not detect thin spots in the coating. This may be considered to be a no nond ndes estr truc uctiv tivee te test st be beca caus usee of th thee re rela lativ tivel ely y lo low w voltage.

3. Terminology 3.1   Definitions: 3.1.1  holiday, n— small small faults or pinholes that permit current drainage through protective coatings on steel pipe or polymeric precoated corrugated steel pipe. 3.1.2   mil, n— 0.001 0.001 in. 3.2  Definitions of Terms Specific to This Standard: 3.2.1   holiday detector, n— a highly sensitive electrical device designed to locate holidays such as pinholes, voids, and thin spots in the coating, not easily seen by the naked eye. These The se are use used d on the coa coatin tings gs of rela relativ tively ely hig high-e h-elect lectric rical al resistance when such coatings are applied to the surface of  materials of low-electrical resistance, such as steel pipe.

1.3 Metho 1.3 Method d B is de desi sign gned ed to de dete tect ct ho holi lida days ys su such ch as pinhol pin holes es and voids in pip pipelin elinee coa coatin tings; gs; but bec becaus ausee of the higher applied voltages, it can also be used to detect thin spots in the coating. This method can be used on any thickness of  pipelinee coatin pipelin coating g and utilizes applied voltages voltages between 900 and 2 20 000 V d-c d-c.. This method is consid considered ered destructive destructive becaus becausee the high voltages involved generally destroy the coating at thin spots.

3.2.2   pipeline type coating, n— coatings coatings of relatively highelectrical electric al res resista istance nce app applied lied to sur surfac faces es of rel relativ atively ely low low-electrical resistance, such as steel pipe.

1.4 The values values stated in SI units to thr three ee sig signifi nifican cantt dec deciimals are to be regarded as the standard. The values given in parentheses are for information only.

4. Summ Summary ary of Test Test Methods 4.1 Both meth methods ods rely on elec electric trical al con contact tact bei being ng mad madee throug thro ugh h th thee pi pipe peli line ne co coat atin ing g be beca caus usee of a ho holi lida day y or a low-resistance path created by metal particles, or thin spots in thee co th coati ating ng.. Th This is el elect ectri rical cal co cont ntact act wi will ll act activ ivate ate an ala alarm rm alerting the operator of the incidence of a holiday.

standard d doe doess not purport purport to add addre ress ss all of the 1.5   This standar safet sa fetyy co conc ncer erns ns,, if an anyy, as asso socia ciated ted wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.

4.2 In Method Method A, the app applied lied voltag voltagee is 100 V d-c or less. 4.3 In Me 4.3 Meth thod od B, th thee ap appl plie ied d vo volta ltage ge is 90 900 0 to 20 000 V d-c.

1 These test methods are under the jurisdiction of ASTM Committee D01 on Paint and Rel Paint Relate ated d Coa Coatin tings, gs, Mat Materi erials als,, and Applicati Applications ons and are the dir direct ect responsibil respon sibility ity of Subco Subcommitte mmitteee   D01.48   on Dur Durabi abilit lity y of Pip Pipeli eline ne Coa Coatin ting g and Linings. Current edition approved July 1, 2014. Published July 2014. Originally approved in 197 1979. 9. Las Lastt pre previo vious us edi editio tion n app approv roved ed in 201 2013 3 as G62 – 07 (20 (2013) 13).. DOI DOI:: 10.1520/G0062-14. 2 This was taken from the pamphlet “Operating Instructions for Tinker and Rasor Model EP Holid Holiday ay Detec Detector tor.” .” Other manufacturers’ manufacturers’ holiday detec detectors tors can be expected to have similar voltage specifications.

5. Signi Significanc ficancee and Use 5.1  Method A— Method Method A descr describes ibes a quick, safe safe method for determining if pinholes, voids, or metal particles are protruding 3

For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [email protected] For  Annual Book of ASTM  Standards volume information, refer to the standard’s Document Summary page on the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States


G62 − 14 through the coating. This method will not, however, find any thin spots in the coating. This method will determine the existence of any gross faults in thin-film pipeline coatings.

a selected resistance, having a 1 ⁄ 2  W rating, is placed across its terminals. A common factory setting for sensitivity is 100 000 Ω. Most units can be reset to any predetermined sensitivity value in this manner.

5.2   Method B— Method B describes a method for determining if pinholes, voids, or metal particles are protruding through the coating, and thin spots in pipeline coatings. This method can be used to verify minimum coating thicknesses as well as voids in quality-control applications.

10. Procedure for Method A 10.1 Use the low-voltage holiday detector described in 6.1. 10.2 Assemble the wand and electrode according to the manufacturer’s instructions and attach the ground wire to the metal surface.

6. Apparatus 6.1   Low-Voltage Holiday Detector— A holiday detector tester having an electrical energy source of less than 100 V d-c, such as a battery; an exploring electrode having a cellulose sponge dampened with an electrically conductive liquid such as tap water; and an audio indicator to signal a defect in a high-electrical resistance coating on a metal substrate. A ground wire connects the detector with the low-resistance metal surface.

10.3 Attach the electrode clamps to the end of the wand, dampen the sponge electrode with tap water, and place it between the clamps. Then tighten the clamps with the screw until they are well down into the sponge electrode. Attach the ground wire (lead with battery clamp) and the wand to the terminals. Clip the ground wire to some point where the metal surface is bare. Now touch the electrode to a second point where the surface is bare and note that the audible signal will be activated. The detector is now ready to operate by passing the damp sponge over the coated surface. When a holiday is picked up by the audible alarm, the electrode can be turned on end and the exact spot of failure can be noted by searching with the tip of the electrode.

6.2  High-Voltage Holiday Detector— A holiday detector tester having an electrical energy source of 900 to 20 000 V d-c; an exploring electrode consisting of wire brush, coil-spring, or conductive silicon electrode capable of moving along the pipeline coating; and an audio indicator to signal a defect in a high-electrical resistance coating on a metal substrate. A ground wire connects the detector with the low-resistance metal surface.

10.4 The voltage between the electrode (sponge) and the metal surface upon which the coating lies shall not exceed 100 V d-c, measured between the electrode sponge and the coated metal when the detector is in its normal operating position.

6.3  Peak or Crest Reading Voltmeter— A kilovoltmeter capable of detecting a single pulse and holding it long enough for the meter circuits to indicate.

10.5 Prior to making the inspection, ensure that the coated surface is dry. This is particularly important if formed surfaces are to be inspected. If the surface is in an environment where electrolytes might form on the surface, such as salt spray, wash the coated surface with fresh water and allow to dry before testing. Take care to keep the electrolyte at least 12.7 mm (1 ⁄ 2 in.) from any bare sheared or slit edge.

7. Reagents and Materials 7.1   Tap Water,  plain or with a wetting agent. NOTE  1—Ordinary tap water will suffice to wet the sponge electrode when inspecting coatings up to 0.254 mm (10 mils) in thickness. On films between 0.254 and 0.508 mm (10 and 20 mils), a nonsudsing type wetting agent added to the water is recommended to allow for faster penetration of the liquid into pinhole defects.

10.6 A low-voltage holiday detector is not satisfactory for the inspection of pipeline coatings over 0.508 mm (20 mils) in thickness. This type of holiday detector will not detect thin spots in pipeline coatings.

8. Test Specimen 8.1 The test specimen shall be a representative length of  production-coated pipe or polymeric precoated corrugated steel pipe.

11. Procedure for Method B 11.1 Use the high-voltage holiday detector. 11.2 Determine the test voltage desired by multiplying the dielectric breakdown voltage per millimetre (mil) of the coating (Note 2) times the minimum allowable thickness of the coating in millimetres (mils).

9. Standardization of Instruments 9.1 The instruments shall be standardized with respect to voltage output in accordance with the manufacturer’s instructions, using a peak or crest reading voltmeter. This is used more commonly with Method B where voltage may vary from test to test but can also be used for verification of the voltage on a Method A test.

NOTE 2—The dielectric breakdown voltage per millimetre (mil) can be determined for each coating experimentally as follows: Increase the holiday detector voltage over a known coating thickness and measure the voltage at the point where the detector will just begin to ring. Divide this voltage by the known coating thickness to obtain the amount of volts per millimetre (mil). This can also be obtained from most coating manufacturers’ literature.

9.2 The low-voltage holiday detector shall be standardized with respect to sensitivity by having the alarm activated when


G62 − 14

FIG. 1 Suggested Form for Use in Presenting Data for Method A and Method B

11.2.1 An alternative method of determining test voltage is by use of one of the following equations depending on coating thickness. 11.2.2 If the coating thickness is less than 1.016 mm (40 mils): V  5 M =Tc

where: V  = Tc = M = M =

11.4 The detector is now ready to operate by passing the electrode over the test specimen. The detector will ring if it passes any void, pinhole, or area of the coating thinner than the minimum allowable thickness. When a holiday is detected by the audible alarm, the electrode can be repositioned to determine the exact holiday area by observing the origin of the spark   jump.

(1 )

11.5 Prior to making the inspection, ensure that the coated surface is dry. Dryness is critical in a high voltage test. Take care to keep the electrode at least 12.7 mm (1 ⁄ 2  in.) from any bare sheared or slit edge.

test voltage coating thickness 3294 if Tc is in millimetres 525 if Tc is in mils.

11.2.3 If the coating thickness is greater than 1.041 mm (41 mils): V  5 K  =Tc

where: V  = Tc = K = K =

12. Report 12.1 The report shall include the following (see Fig. 1):

(2 )

12.2 Complete identification of the specimen including names and code number of the coating, pipe diameter, source, production data, and production run number. For polymeric precoated corrugated steel pipe, the reporting requirements of  Specification A742/A742M  shall be used for identification,

test voltage coating thickness 7843 if Tc is in millimetres 1250 if Tc is in mils

12.3 Name and type of instrument used, method of  standardization, and whether Method A or Method B was used, and

11.2.4 These equations are predicated on the amount of  voltage needed to jump an air gap of the same length as the coating thickness. Therefore, they are useful for testing voids, pinholes and thin spots in the coating, but would not be useful as a coating thickness quality control tool.

12.4 If Method B was used, state the test voltage, the method used to calculate the voltage, and the minimum allowable thickness in millimetres (mils) of the test sample.

11.3 Ground the test specimen by attaching the ground wire to a bare metal spot on the pipe surface. Plug the ground wire into the holiday detector. Then make up the searching electrode in accordance with the manufacturer’s recommendations, using a brush wire or conductive silicon electrode. Plug the searching electrode into the holiday detector. Turn on the holiday detector. 11.3.1   CAUTION: Because of the high voltages involved, do not touch the ground wire and the metal part of the electrode at the same time if the instrument is on.

13. Precision and Bias 13.1 Precision data are limited to adjacent specimens taken from the production-coated pipe as for the polymeric corrugated steel pipe assuming that the production process was uniform with respect to pipe surface condition and coating material. Specimens that were not adjacent in the as-produced condition, or were taken from different lengths of pipe, may represent differing process conditions. 3

G62 − 14 13.2   Repeatability— When the same instrument is used by the same operator, duplicate measurements on the same specimen shall agree within 65 %.

13.4   Bias— This test detects the presence of a conductive path through the coating and is therefore not a measurement. No value for bias can be determined.

13.3   Reproducibility— Different operators using different instruments, set at the same voltage, inspecting the same specimen shall obtain average results agreeing with each other within 610 %.

14. Keywords 14.1 holiday detector; holidays; piping; pinhole; wet sponge detector

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