ASTM_D_6793_-_02_2012.pdf

Designation:D679302(Reapproved 2012)Standard Test Method forDetermination of Isothermal Secant and Tangent BulkModulus1This standard is issued under the fixed designation D6793;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 isothermalsecant and tangent bulk modulus of liquids which are stableand compatible with stainless steel under the conditions of test.1.2 This test method is designed to be used over thetemperature range from-40 to 200C and from ambient to68.95 Mpa(10 000 psig).NOTE1Because of the design of the test apparatus,the upper limit ofpressure which can be attained is limited by the bulk modulus of the testfluid.Pressures as high as 68.95 Mpa will not be attained for fluids ofrelatively low bulk modulus at the test temperature.1.3 This test method assumes that the user is proficient inthe assembly and use of medium pressure(m/p)threaded andconed fittings which are intended for use at pressures up to137.9 Mpa(20 000 psig).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 practices and determine the applica-bility of regulatory limitations prior to use.NOTE2Because hydraulic pressure in the test system is produced bypurely mechanical means,the test method is not subject to the hazardsassociated with systems which are pressurized pneumatically.Even smallleaks will result in immediate drop in pressure to ambient withoutproduction of a high pressure liquid stream or mist.2.Referenced Documents2.1 ASTM Standards:2D235 Specification for Mineral Spirits(Petroleum Spirits)(Hydrocarbon Dry Cleaning Solvent)D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsE300 Practice for Sampling Industrial Chemicals3.Terminology3.1 Definitions:3.1.1 isothermal secant bulk modulus,nthe product oforiginal fluid volume and the slope of the secant drawn fromthe origin to any specified point on the plot of pressure versusvolume change divided by volume at constant temperature.3.1.2 isothermal tangent bulk modulus,nthe product offluid volume at any specified pressure and the partial derivativeof fluid pressure with respect to volume at constant tempera-ture.4.Summary of Test Method4.1 Determination of Isothermal Secant Bulk Modulus:4.1.1 A piston in the form of a medium pressure valve isforced into a chamber which is liquid-filled.The pressurecreated by the insertion of the piston is measured.4.2 A system constant V/V is determined by use of astandard of known bulk modulus as follows:SVVD5BHiP5BHiPn2 Po!(1)where:Bi=isothermal secant bulk modulus,Po=pressure at the origin before insertion of the piston,andPn=pressure of the system at insertion of piston to Positionn.NOTE3V/V is thus a constant determined by system volume andpiston displacement only.It is independent of temperature and whenknown,can be used to determine isothermal secant bulk modulus frompressure data obtained for various degrees of piston insertion.4.3 Isothermal tangent bulk modulus and sample density,ifdesired,may be determined from isothermal secant bulkmodulus data determined as a function of pressure by use of thecalculations in Section 12.5.Significance and Use5.1 Isothermal secant bulk modulus(static bulk modulus)isa property that measures the compressibility of a liquid.Thegreater the value,the less the compressibility of the liquid.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.L0.07 on Engineering Sciences of High Performance Fluids andSolids(Formally D02.1100).Current edition approved April 15,2012.Published May 2012.Originallyapproved in 2002.Last previous edition approved in 2007 as D679302(2007).DOI:10.1520/D6793-02R12.2For 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 5.2 Isothermal secant bulk modulus is employed in thedesign of high performance hydraulic fluid and braking sys-tems.High bulk modulus is desirable in that the response timeof a system is faster when applied pressure more directlyeffects the action of the system rather than in the compressionof the working liquid.5.3 If isothermal secant bulk modulus is known as afunction of pressure,the data may be used to calculateisothermal tangent bulk mod