1、Designation:D 2771 90(Reapproved 1997)e1An American National StandardStandard Test Methods forCompaction Density of Electrical Grade Magnesium Oxide1This standard is issued under the fixed designation D 2771;the number immediately following the designation indicates the year oforiginal adoption or,i
2、n 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.e1NOTEKeywords were added editorially in October 1997.1.Scope1.1 These test methods cover the dete
3、rmination of thecompaction density of electrical grade magnesium oxide inheating units.1.2 Two alternative procedures are described:Test Method AWater Displacement,andTest Method BAbsorption.1.3 This standard does not purport to address the safetyproblems associated with its use.It is the responsibi
4、lity of theuser of this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2.Referenced Documents2.1 ASTM Standards:D 176 Test Methods for Solid Filling and Treating Com-pounds Used for Electrical Insulation23.Apparatu
5、s3.1 For either test method,a balance capable of weighing to0.1 mg is required.4.Sampling4.1 Specimens shall be obtained by cutting lengths of about25 mm from the heating unit.4.2 Rough edges,metal chips,or loose oxide resulting fromthe cutting operation shall be removed carefully before pro-ceeding
6、.TEST METHOD AWATER DISPLACEMENT5.Procedure5.1 Weigh the specimen to the nearest 1 mg.5.2 Seal the specimen against water absorption by the use ofone of the following materials,the density of which must beknown:5.2.1 Canada balsam,molten paraffin wax,RTV siliconerubber,3or heat-shrinkable poly(vinyl
7、 chloride)tubing.4NOTE1The sealant must cover each face of the sample and extend atleast 5 mm along the sheath from each end.5.3 Dry,cure,or otherwise fix the sealant according to thestandard procedure appropriate to the material used.5.4 Weigh the sealed specimen in air to the nearest 1 mg.5.5 Susp
8、end the specimen in distilled water and weigh whilesuspended.NOTE2Caution:Use the smallest and lightest suspension wire pos-sible to minimize error.5.6 Strip the seals from the specimen.Remove all magne-sium oxide from the specimen by deforming the sheath with avise or hammer to loosen the insulatio
9、n.Weigh the sheath andresistance wire together in air.5.7 Suspend the sheath and resistance wire together in waterand weigh while suspended(see Note 2).6.Calculation6.1 Calculate the compaction density of the magnesiumoxide as follows:Density,g/cm35W12 W4FW22 W3!2W42 W5!D2G2W22 W1!D1where:W15 weight
10、 of specimen in air,W25 weight of sealed specimen in air,W35 weight of sealed specimen in water,W45 weight of sheath and wire in air,W55 weight of sheath and wire in water,D15 density of sealant,andD25 density of water at test temperature.TEST METHOD BABSORPTION7.Procedure7.1 Weigh the specimen to t
11、he nearest 1 mg.1These test methods are under the jurisdiction of ASTM Committee D-9 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.14 on Electric Heating Unit Insulation.Current edition approved July 27,1990.Published September 1990.Originallyp
12、ublished as D 2771 69.Last previous edition D 2771 69(1979)e1.2Annual Book of ASTM Standards,Vol 10.01.3Silastic RTV 731,Dow Corning Corp.,has been found suitable for this purpose.Specific gravity is 1.15.4Type SCL,Rayclad Tubes,Inc.,has been found suitable for this purpose.Specific gravity is 0.935
13、.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.NOTICE:This standard has either been superceded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.7.2 Submerge the specimen in
14、 kerosine or low-viscosity oil5of known density,and soak for at least 12 h.7.3 Remove the specimen from the fluid and dry the surfacewith an absorbent paper or cloth,being careful to avoiddrawing the adsorbed fluid from the insulation.Immediatelyweigh the specimen to the nearest 1 mg.7.4 Remove all
15、magnesium oxide from the specimen bydeforming the sheath with a vise or hammer to loosen theinsulation.Clean the sheath and resistance wire throughly andweigh together.8.Calculation8.1 Calculate the compaction density of the magnesiumoxide as follows:Density,g/cm35W62 W8W72 W6D31W62 W8D4where:W65 we
16、ight of specimen,W75 weight of specimen with absorbed fluid,W85 weight of sheath and wire,D35 density of fluid,andD45 density of MgO,as determined per Methods D 176.9.Report9.1 Report the following information:9.1.1 Proper identification of the specimen,9.1.2 Results from 5.1 or 7.1 obtained from at least twodeterminations and their average,and.9.1.3 The test method used,A or B.10.Precision and Bias10.1 The compaction density when determined by TestMethod A is found to have a precision of 65%and
