ASTM_D_2668_-_07_2013.pdf

Designation:D266807(Reapproved 2013)Standard Test Method for2,6-di-tert-Butyl-p-Cresol and 2,6-di-tert-Butyl Phenol inElectrical Insulating Oil by Infrared Absorption1This standard is issued under the fixed designation D2668;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the weightpercent of 2,6-ditertiary-butyl paracresol(DBPC)and 2,6-ditertiary-butyl phenol(DBP)in new or used electrical insu-lating oil in concentrations up to 0.5%by measuring itsabsorbance at the specified wavelengths in the infrared spec-trum.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating LiquidsD2144 Practices for Examination of Electrical InsulatingOils by Infrared AbsorptionD3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus3.Significance and Use3.1 The quantitative determination of 2,6-ditertiary-butylparacresol and 2,6-ditertiary-butyl phenol in a new electricalinsulating oil measures the amount of this material that hasbeen added to the oil as protection against oxidation.In a usedoil it measures the amount remaining after oxidation hasreduced its concentration.The test is also suitable for manu-facturing control and specification acceptance.3.2 When an infrared spectrum is obtained of an electricalinsulating oil inhibited with either of these compounds there isan increase in absorbance of the spectrum at several wave-lengths(or wavenumbers).2,6 ditertiary-butyl paracresol pro-duces pronounced increases in absorbance at 2.72 m(3650cm1),and 11.63 m(860 cm1).2,6 ditertiary-butyl phenolproduces pronounced increases in absorbance at 2.72 m(3650cm1)and 13.42 m(745 cm1).3.3 When making this test on other than a highly oxidizedoil or when using a double-beam spectrophotometer,it hasbeen found convenient to obtain the spectrum between 2.5 m(4000 cm1)and 2.9 m(3450 cm1)because the instrument iscompensated for the presence of moisture and the band is notinfluenced by intermolecular forces(associations).However,when testing a highly oxidized oil or when using a single-beaminstrument better results may be obtained if the scan is madebetween 10.90 m(918 cm1)and 14.00 m(714 cm1).3.4 Increased absorption at 11.63 m(860 cm1)or 13.42m(745 cm1)or both,will identify the inhibitor as 2,6-ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol re-spectively(Note 1).NOTE1The absorbance at 745 cm1for 2,6-ditertiary-butyl phenoland at 860 cm1for 2,6-ditertiary-butyl paracresol for equal concentra-tions will be in the approximate ratio of 2.6 to 1.4.Apparatus4.1 With equipment description referring to compliance,theequipment shall be in accordance with Section 6 of PracticesD2144.Accordingly,the use of Fourier-transform rapid scaninfrared(FTIR)spectrophotometers is permitted by referenceto that test method.5.Sampling5.1 Obtain the sample in accordance with Practices D923.6.Calibration and Standardization6.1 When the manufacturer of the oil is known and the baseoil is available,use it to prepare the standards.For oils ofunknown origin,use base oils which meet the requirements ofSpecification D3487.Some base oils may provide a bettermatch than others and therefore it is desirable to have severalavailable.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.03 on Analytical Tests.Current edition approved Nov.1,2013.Published December 2013.Originallyapproved in 1967.Last previous edition approved in 2007 as D2668 07.DOI:10.1520/D2668-07R13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2 Prepare standards containing between 0.05 and 0.4weight percent of 2,6-ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol dissolved in an uninhibited base oil.Alternatively,the range of prepared standards may be in-creased to 0.5 weight percent if certain oils to be investigatedare believed to contain greater amounts of inhibitor.Obtain aspectrum,at the desired band,of each standard in accordancewith Pract