1、Designation:D 2285 99Standard Test Method forInterfacial Tension of Electrical Insulating Oils of PetroleumOrigin Against Water by the Drop-Weight Method1This standard is issued under the fixed designation D 2285;the number immediately following the designation indicates the year oforiginal adoption
2、 or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a comparatively rapid proce-dure particularly applicable f
3、or field use for measuring,undernonequilibrium conditions,the interfacial tensions of electricalinsulating oils of petroleum origin against water.This testmethod has been shown by experience to give a reliableindication of the presence of hydrophilic compounds.This testmethod may not be applicable f
4、or highly viscous insulatingfluids.1.2 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior t
5、o use.2.Referenced Documents2.1 ASTM Standards:D 971 Test Method for Interfacial Tension of Oil AgainstWater by the Ring Method2D 1298 Practice for Density(Specific Gravity)or APIGravity of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer Method33.Summary of Test Method3.1 Interfacial te
6、nsion is determined by measuring thevolume of a drop of water formed in oil.A larger water dropmeans a higher interfacial tension.The instrument is calibratedto read approximately in millinewtons per metre(dynes percentimetre).The measurement is completed within 1 min afterthe formation of the water
7、 drop in oil.4.Significance and Use4.1 This test method indicates the presence of hydrophiliccompounds.These compounds can be an indicator of contami-nants in new oil and in used oil,oxidation or deterioration ofthe oil or materials of construction in contact with the oil.5.Apparatus5.1 Tensiometer4
8、that provides a simple way of injecting ameasured quantity of water into oil.The scale attached to thepiston forcing the water into the oil is graduated in millinew-tons per metre(dynes per centimetre).5.2 Test Specimen ContainerGlass beaker or transparentcylindrical vessel having a minimum diameter
9、 of 1 in.(25.4mm).5.3 Needle,supplied with the tensiometer having a bluntend with a 90 angle.Follow manufacturers guidelines forselection.6.Preparation of Apparatus6.1 Wipe the needle free of oil with clean lint free paper,avoiding any upward motion that may embed a bit of fiber onthe sharp needle.D
10、o not use an oil solvent on the needle orbarrel.6.2 Force distilled water through the barrel and needle toclean the inside.Only when contamination is suspected shoulddetergents or solvents be used for cleaning,followed by athorough rinsing with distilled water.Detergents will lowerinterfacial tensio
11、n results6.3 Clean the test specimen container by removing anyresidual oil with petroleum naphtha(see Note 1)or othersuitable hydrocarbon solvents followed by washing with adetergent solution.Rinse thoroughly with tap water,thendistilled water.NOTE1Warning:Petroleum naphtha is flammable and harmful
12、ifinhaled.7.Calibration of Apparatus7.1 Interfacial tension,in millinewtons per metre(dynes percentimetre),is determined by the following equation:1This test method is under the jurisdiction of ASTM Committee D-27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-m
13、ittee D27.07 on Physical Test.Current edition approved March 10,1999.Published May 1999.Originallypublished as D 2285 64 T.Last previous edition D 2285 98.2Annual Book of ASTM Standards,Vol 10.03.3Annual Book of ASTM Standards,Vol 05.01.4Use a tensiometer that employs the drop weight principle for m
14、easuringinterfacial tension.The sole source of supply of the apparatus known to thecommittee at this time is a tensiometer available from Gerin Corp.,1109 7thAvenue,Neptune,NJ 00753.If you are aware of alternative suppliers,pleaseprovide this information toASTM headquarters.Your comments will receiv
15、e carefulconsideration at a meeting of the responsible technical committee,which you mayattend.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMInterfacial tension,m N/m 5 R1D 2 d!S/R2!where:R15 re
16、ading of dial(divisions per drop)of water in oil,R25 reading of dial(divisions per drop)of water in air,D5 density of water at measuring temperature(0.998 at20C and 0.997 at 25C),d5 density of oil at measuring temperature(If density isnot known,use 0.885 average density),andS5 surface tension of water in air(72.75 at 20C and71.97 at 25C).7.2 Thus,the only calibration is in the R2value,and thisrequires a measurement of the volume,in terms of divisions onthe scale,of a drop of water expelled into
