1、Designation:D 6181 03Standard Test Method forMeasurement of Turbidity in Mineral Insulating Oil ofPetroleum Origin1This standard is issued under the fixed designation D 6181;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of
2、 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 the laboratory procedure thatascertains the quantity of suspensions in insulating oils ofpetroleu
3、m origin using a nephelometric measurement tech-nique to determine the fluids turbidity.This test method isdesigned to reveal changes that may occur to these oils.1.2 This test method is applicable for turbidities in the rangeof 0.1 to 500 Nephelometric Turbidity Units(NTU).1.3 The values stated in
4、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 of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health p
5、ractices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D 923 Test Method for Sampling Electrical Insulating Liq-uidsD 1533 Test Methods for Water in Insulating Liquids(KarlFischer Reaction Method)D 1698 Test Method for Sediments and
6、 Soluble Sludge inService Aged Insulating OilsD 1889 Test Method for Turbidity of WaterD 4652 Specification for Silicone Fluid Used for ElectricalInsulationD 5180 Test Method for Quantitative Test for Turbidity inClear LiquidsE 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods
7、3.Terminology3.1 Description of Terms Specific to This Standard:3.1.1 nephelometric turbidity unit(NTU),nintensity oflight scattered by a known aqueous suspension of formazine.One NTU is the turbidity of a formazine solution produced bymixing 12.5 g of hydrazine su1fate and 1.25 g of hexa-methylenet
8、etramine in 1 mL of turbidity-free water.SeeAppendix X1 for preparation instructions.3.1.2 turbidity,nthe reduction of transparency due to thepresence of particulate matter.4.Summary of Test Method4.1 The turbidity is determined by a calibrated,ratio turbi-dimeter,which measures scattered light at 0
9、.5 p rad(90)or0.5 and 1.5 p rad(90 and 270)angles to the incident beam.These instruments cannot be calibrated accurately in terms ofabsolute turbidity except in the case of fluids having uniform-size particles that are less than approximately one fifth of thewave length of the incident light.Standar
10、ds have been preparedby thoroughly mixing suitable amounts of finely dividedtitanium dioxide into partially polymerized polystyrene.Alter-natively,suspension of formazine has been used as a turbiditystandard,formed by reacting hydrazine sulfate and hexameth-ylenetetramine under carefully controlled
11、conditions.3Cali-brated commercial standards in sealed tubes also are available.4.2 The test specimen is placed in the cell and its turbidityis measured.The turbidimeter measures the light scattered bysuspended solids dispersed within the test specimen.Accuracyand sensitivity of the method is ensure
12、d by measuring theturbidity at a wavelength of light where there is little or noabsorption of the light by the test specimen.Use of a narrowbandwidth of light reduces interference that may be inherent tooxidized insulating oils.The narrow bandwidth is achievedthrough the use of an optical filter to
13、provide light at 600 nmwith a 40 nm bandwidth.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.07 on Physical Test.Current edition approved Oct.1,2003.Published December 2003.Originallyap
14、proved in 1997.Last previous edition approved in 1997 as D 6181-97.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website
15、.3For information,see Chevalier,P.,“Formazine Standard for Turbidity,”Brasserie,Vol 152,1959,pp.132133.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.4.3 This test method is recommended only for mineralinsulating oils and is not intended
16、 to be used on other fluids.5.Significance and Use5.1 This test method uses a ratio turbidimetric opticalsystem to measure the turbidity of insulating oils relative toturbidity standards.Cloudiness or turbidity is attributed tomatter whose diameter is approximately 20%of the wave-length of the incident light.Increasing turbidity signifiesincreasing transformer fluid contamination,either from exter-nal sources or internal chemical reactions(such as oxidation)that produce fine particulate matter.O
