ASTM G55-2007 Standard Test Method for Evaluating Pipeline Coating Patch Materials《管道涂层修补材料的评估用标准试验方法》.pdf

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1、Designation: G 55 07Standard Test Method forEvaluating Pipeline Coating Patch Materials1This standard is issued under the fixed designation G 55; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in

2、parentheses indicates the year of last reapproval.Asuperscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides an accelerated means ofdetermining the relative sealing abilities of pipeline patchingmaterials that are used to seal ho

3、lidays in pipeline coatings onsteel pipe. This test method is intended for utilization ofspecimens of pipeline coatings on small-diameter pipe, forrepresenting coatings used for buried or submerged service,and where the purpose of the coating is to provide an electricalbarrier between the steel pipe

4、 and its environment.1.2 This test method is not intended for evaluating patchmaterials that are overlapped upon themselves.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all o

5、f thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Summary of Test Method2.1 Patched pipeline coating specimens ar

6、e suspended in anaqueous, alkaline, low-resistivity electrolyte. The specimensare individually connected to a magnesium anode or rectifier ata point external to the electrolyte. The coated, patched pipelinespecimens are sealed at the base and at all other areas exceptthe patch boundaries, such that

7、the only paths for current floware at the boundaries of the patches. Current flow in each patcharea is averaged from monthly readings taken for one year.3. Significance and Use3.1 Holidays in pipeline coatings may be repaired bycircumferential wrapping with a suitable pipe wrap tape.However, this te

8、chnique is not always practicable and patchingmay be required. The effectiveness of a patch material dependsupon its adhesion to the original pipeline coating to effectsealing.3.2 The results of this accelerated test have been found toyield comparative data useful for the selection of patchingmateri

9、als. The user is cautioned against the use of this methodfor absolute material properties characterization.3.3 This procedure provides an accelerated method byexposing the patch to a severe radius of curvature on small-diameter pipe. The specimen is also exposed to a stress voltagein the presence of

10、 a highly conductive electrolyte.4. Apparatus4.1 Test VesselA cylindrical glass battery jar (or equiva-lent), approximately 300 mm (12 in.) in diameter and 300 mmin height. One magnesium anode shall be contained in eachbattery jar, with a maximum of eight pipe specimens, and witheach specimen measur

11、ing about 25 mm (1 in.) in diameter byapproximately 300 mm in length of coated pipe. (See 4.3 andFig. 1 and Fig. 2.)4.2 SuspensionThe suspension ring for supporting thepipe specimens shall be an electrically nonconductive circulardisk, measuring approximately 300 mm (12 in.) in diameterand approxima

12、tely 5 mm (316 in.) in thickness. (See 6.4.) Drilla 15-mm (12-in.) diameter hole through the center of the ringfor external extension of the anode lead wire. Drill eightsuspension holes, about 45 mm (134 in.) in diameter, throughthe suspension ring for the pipe specimens; these holes shall becentere

13、d 110 mm (412 in.) from the center of the suspensionring and evenly spaced around the ring at 45 increments asmeasured from the center of the suspension ring.4.3 PotentialA high-purity magnesium anode shall beused, weighing approximately 2.3 kg (5 lb), and having anopen-circuit potential of approxim

14、ately 1.7 d-c V relative to acopper-copper sulfate electrode, and complete with a factory-sealed lead wire. The magnesium anode may be replaced by acontrolled d-c voltage from a rectifier, and then maintaining thepotential between the specimen having the least current flowand a copper-copper sulfate

15、 reference cell (with the cell beingproperly immersed in the electrolyte) at 1.50 6 0.05 d-c V.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.48 on Durability of Pipeline

16、Coating and Linings.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1977. Last previous edition approved in 1998 as G 55 88 (1998) which waswithdrawn March 2007 and reinstated in July 2007.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh

17、ohocken, PA 19428-2959, United States.(See Note 1.) The anode should be composed of a suitablenonconsumable material.2This option will avoid the precipi-tation of magnesium salts on the specimens.NOTE 1The potential of the magnesium anode will approximate thisrange over the life of the test. If a ca

18、lomel electrode is used for thereference cell, the potential should be 1.43 6 0.05 d-c V.4.4 ElectrolyteUse 1 % each by weight of anhydrous puregrades of sodium chloride, sodium sulfate, and sodium carbon-ate, dissolved in either distilled water or demineralized water.This electrolyte shall never be

19、 less alkaline than pH = 10.0 andshould be within a resistivity range from 20 to 35 V cm.4.5 Instruments:4.5.1 Resistivity Meter, capable of measuring 20 to 40Vcmin an aqueous solution.4.5.2 pH meter, capable of measuring 0 to 14 pH.4.5.3 Thermometer, ASTM Type 17C or equivalent, 19 to27C.4.5.4 Micr

20、oammeters, d-c, 0 to 100-A and 0 to 500-A.4.5.5 Voltmeter, for direct current, having an internal resis-tance of not less than 10 MV and having a range from 0.01 to5.0 V.4.5.6 Full-Wave Rectifier, optional, 0 to 0.05 % ripple,capable of maintaining 1.50 6 0.05 d-c V relative to acopper-copper sulfat

21、e cell, and having a capacity for at least 10A of direct current.5. Test Specimens5.1 DimensionsThe specimen shall be steel pipe approxi-mately 25 mm (1 in.) in diameter, approximately 300 mm (12in.) in length, and previously coated with the desired originalpipeline coating.5.2 Circuit TapA 5-mm (31

22、6-in.) diameter hole shall bedrilled or tapped (or a self-tapping screw may be used) at apoint 13 mm (12 in.) below the top of each specimen. This tapis for a machine screw anode lead wire connection.5.3 Pipe Suspension Support HolesA 6-mm (14-in.) di-ameter hole shall be drilled completely through

23、both walls ofthe coated pipe specimen at a point 20 mm (34 in.) from the topend of the specimen and located vertically beneath the circuittap hole. A short length of wooden dowel pin about 5 mm (316in.) in diameter shall be used as an insertion through thesuspension holes to support and level the pi

24、pe specimen on thecircular suspension ring when the suspension ring is mountedon the battery jar.5.4 Intentional HolidaysA 4-fluted 13-mm (12-in.) diam-eter facing bit shall be used to drill intentional holidays throughthe original pipeline coating to the metal. Drilling suchholidays shall be practi

25、ced on scrap pieces of small-diametercoated pipe, prior to drilling the holidays in the test specimens.Drilling shall not be any deeper than necessary into the metalof the pipe. Three holidays shall be prepared on each specimenin a vertical line directly underneath the circuit tap to corre-spond to

26、electrolyte immersions of 38 mm (112 in.), 114 mm(412 in.), and 190 mm (712 in.), as measured from the top of theholiday to the surface of the electrolyte. The thickness of thesuspension ring shall be considered for its effect in elevatingthe pipe specimens in the electrolyte.5.5 PatchesA square pat

27、ch configuration of 25 by 25 mm(1 by 1 in.), evenly centered about the holiday, shall be lightlymarked. This will provide a minimum patch overlap of 6 mm(14 in.) as measured perpendicular to the center of each patchedge to the circumference of the holiday. The top and bottomedges of each patch shall

28、 be in the horizontal plane. Eachmarked patch area shall be lightly buffed with 120-grit sand-paper. A primer shall be applied using clean cotton on a stickto extend the primer to the edges of the marked patch areawhen specified by the manufacturer of the patch. The manu-facturers specified drying t

29、ime shall be used for primers beforeapplication of the patch. Scissors or a knife shall be used to cuttape patches to size; tape patches shall be applied by a firmpressure of the thumb. Wax patches shall be applied bydripping or pouring the melted wax on the patch area to thedesired patch thickness.

30、 Each mastic patch or each liquid patchshall be applied with a new, clean brush. The number of coatsapplied shall be recorded and the patch thickness shall beindicated. The balance of the circumferential band that is notcovered by a patch is then covered either with the patchmaterial under test or w

31、ith another material that has beendemonstrated to maintain an effective seal with the originalpipeline coating. The base of each specimen shall be sealed2The sole source of supply of a nonconsumable anode, Durachlor 51 anode,Type B, 18-in. with cable, known to the committee at this time is Duriron C

32、o., P.O.Box 1145, Dayton, OH 45401. If you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments willreceive careful consideration at a meeting of the responsible technical committee,1which you may attend.FIG. 1 Test Assembly for Evaluat

33、ing Pipeline Coating PatchMaterialsG55072with a material capable of preventing current flow at the baseof the specimen.All prepared specimens shall be conditioned aminimum of 48 hours at room temperature prior to immersionin the electrolyte. Current leakage at the base seal shall belimited to not mo

34、re than 1 A.5.6 WiringIndividual 150-mm (6-in.) lengths of 18-gageinsulated copper wire and small alligator clips shall be used forthe electrical connection from the machine screw of thespecimen to the lead wire of the anode.6. Procedure6.1 Place the anode in the bottom of the battery jar. Extendthe

35、 anode lead wire vertically through the center of thesuspension ring; then center the suspension ring on the batteryjar.6.2 Mount each patched pipe specimen through one of thelarge holes in the suspension ring, with patches facing out, untilthe wooden dowel pin in the suspension hole of the specimen

36、is supported by the suspension ring. When all specimens havebeen suspended into the battery jar, pour the room temperatureelectrolyte into the battery jar to a point 32 mm (114 in.) abovethe topmost patch. The electrolyte will then be the requiredheight above each patched holiday. Mark and maintain

37、thislevel of electrolyte by additions of distilled water or deminer-alized water. Maintain the assembly at room temperature forthe entire test.6.3 WiringUse alligator clips to connect the 150-mm(6-in.) length of 18-gage insulated copper wire from themachine screw in the patched specimen to the lead

38、wire of theanode.6.4 DataSee the suggested report (Fig. 3) for the collec-tion of data. Record the data at the start of the test exposure as0 month test duration. Record the data (microamperes ofcurrent flow, pipe to electrolyte potential relative to a copper-copper sulfate reference cell, and the e

39、lectrolyte with respect topH, resistivity, and temperature) each month for 12 consecutiveFIG. 2 Alternative Test Assembly for Evaluating Pipeline Coating Patch MaterialsG55073months. Select a date for taking data within 62 calendar daysof the day of the month that the initial data were recorded (for

40、example, a test beginning on the 19th day of a particular monthshould have successive monthly data taken between the 17thand 21st days of the next 12 months).6.5 Current Flows:6.5.1 Determine current flows by temporarily disconnectingthe 18-gage insulated wire from the anode, connecting thepositive

41、lead froma0to100microammeter (d-c) to thepatched specimen, and connecting the negative lead to the wirefrom the anode, external to the battery jar. If there is ameasurable current flow for a patched specimen (1 A ormore), remove that specimen from the battery jar, taking carenot to allow the specime

42、n to contact the edge of the hole in thesuspension ring. Gently rinse the specimen with either dem-ineralized water or distilled water (at room temperature) toremove all traces of electrolyte. Then, with the microammeterconnected in series from the patched specimen to the anode,slowly lower the patc

43、hed specimen into the electrolyte and notethe current flow just below, and then just above, each patch.The difference in microamperes is the amount of current flowthat is being transmitted by that particular patch.6.5.2 Record only 100 A when the current flow for a patchexceeds 100 A. When 100 A has

44、 been recorded for twoconsecutive readings, remove the patch, clean the patch area,and then permanently patch the area with a material capable ofsealing the holiday for the remainder of the test. The currentflow data for the original patch is assumed to continue at themaximum value of 100 A for the

45、remainder of the test. Theresealing will permit the continuance of accurate readings ofthe current flows for the remaining test patches on that pipespecimen. The 0 to 500 d-c microammeter can be used asnecessary during the first month of failure of one or morepatches on a pipe specimen, when the tot

46、al current flow of apipe specimen exceeds 100 A.7. Report7.1 The report shall be a copy of the data collection form(Fig. 3) with all computations completed. The averages areobtained by adding all of the numbers accumulated in a column(initial reading plus 12 monthly readings), and dividing thesummat

47、ion by 13. Determine average values for the microam-peres of current flow for each patch, the pipe to electrolytepotential, and for the pH, resistivity, and temperature of theelectrolyte. The summary section also provides space for alisting of the average current flow for each set of three patches.8

48、. Precision and Bias8.1 Precision data are limited to the comparison of the threesamples of any one patch material sealing the holidays on anyFIG. 3 Suggested Form for Collecting and Summarizing DataG55074one original pipeline coating. These data are based on limitedinformation, but statistically ha

49、ve been shown, by round-robintesting by four laboratories, to provide a reasonable basis forcomparing the sealing abilities of various patching materialsand various pipeline coatings.8.2 The average values of triplicate samples of the samematerials, excluding values of 0 A, by the same worker shouldnot be considered suspect unless they differ by more than afactor of 2. For example, an average value of 20 Afor one setrequires a second set of the same materials to be between 10 to40 A for the same worker.8.3 The average values of triplicat