1、Designation:D 2772 90(Reapproved 1997)e1An American National StandardStandard Test Method forSieve Analysis of Electrical Grade Magnesium Oxide1This standard is issued under the fixed designation D 2772;the number immediately following the designation indicates the year oforiginal adoption or,in the
2、 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.e1NOTE Keywords were added editorially in October 1997.1.Scope1.1 This test method covers the determina
3、tion of the particlesize distribution in a representative sample of granular electri-cal grade magnesium oxide.1.2 The values stated in acceptable metric units are to beregarded as the standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It
4、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.Referenced Documents2.1 ASTM Standards:D 2755 Test Method of Sampling and Reduction to TestWeight of Electrical Grade Magn
5、esium Oxide2E 11 Specification for Wire-Cloth Sieves for Testing Pur-poses33.Summary of Test Method3.1 A representative sample of MgO is sifted through aseries of sieves and the amount caught on each sieve isweighed and recorded as a percentage of the total sample.4.Apparatus4.1 Sieve Shaker.44.2 U.
6、S.Standard Brass or Stainless Steel Sieve(half-height):4.2.1 Required:40,60,80,100,140,200,325,pan,andcover.4.2.2 Optional:35,45,50,120,and 170.4.3 Timer.4.4 Triple-Beam Balance.4.5 Receiving Pan,approximately 20 cm(8 in.)long by 10cm(4 in.)wide by 7.6 cm(3 in.)deep.4.6 Nonmetallic Brush.4.7 Small R
7、ubber-Rod or Mallet.5.Calibration of Sieves5.1 Each test station should possess two sets of sieves.Thefirst set should be in normal use.The second set should be keptas a calibration set5and run on a comparison sample with thefirst set after every 50 sieve analyses.5.2 When the sieves on the first se
8、t wear out,they shall bereplaced by ones from the second set.New sieves shall beobtained to replace the second or calibration set.5.3 Sieve openings may be checked using one of thefollowing methods:5.3.1 Comparison with a New SieveThis may be done byobtaining two similar 100-g test samples of MgO fr
9、om thesame lot of material,using Test Method D 2755.One samplelot of material should then be put through each sieve,using thesame procedure.The amount of MgO through the sieve beingtested must be within a tolerance of 63%by weight whencompared with that put through the new sieve.5.3.2 Follow the Pro
10、cedure Outlined in Specification E 11.Table 1 is from Specification E 11.5.4 Sieve openings should be checked(a)if a sievebecomes slack,(b)if a sieve becomes clogged and(c)when asieve has been used 200 times or after a period of 6 months,whichever occurs first.5.5 Sieves used for testing electrical
11、grade MgO should beused for this purpose only.5.6 Sieves should be kept clean by using a soft brush andwhen necessary,may be cleaned by using(a)a trichloroethyl-ene degreaser,(b)ultrasonic cleaning,or(c)by tapping with asmall rubber hammer.Wire brushes should not be used.6.Procedure6.1 Nest the desi
12、red sieves in order,with the coarsest beinguppermost and the pan being on the bottom.6.2 Obtain a sample between 100 and 125 g,using TestMethod D 2755.6.3 Weigh to the nearest 0.1 g and record the sample weight.1This method is under the jurisdiction of ASTM Committee D-9 on Electricaland Electronic
13、Insulating Materials and is the direct responsibility of SubcommitteeD09.14 on Electric Heating Unit Insulation.Current edition approved July 27,1990.Published September 1990.Originallypublished as D 2772 69.Last previous edition D 2772 84.2Annual Book of ASTM Standards,Vol 10.02.3Annual Book of AST
14、M Standards,Vol 14.02.4Ro-Tap Sieve Shaker,W.S.Tyler Co.,has been found suitable for this purpose.5National Institute of Standards and Technology(NIST)Standards 1017A,1017B,and 1004A can be used to calibrate this set of sieves.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Cons
15、hohocken,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.6.4 Place the sample on the coarsest sieve,place the coveron top,and mount the sieve assembly in the s
16、ieve chamber.6.5 Operate the shaker for 15 min.6.6 Weigh the grain fractions as follows:6.6.1 Transfer the grain to the receiving pan from each sieveand then brush the bottom surface very carefully,allowinggrains to fall into pan from the top surface of the sieve.Lightlyknock the side of the sieve frame with a small rubber-coveredrod or mallet to remove the last grains.6.6.2 Weigh the following fractions separately:(35),40,(45),(50),60,80,325,pan.6.6.3 Weigh the following as one group or separat