ASTM_D_7739_-_11.pdf

Designation:D773911Standard Practice forThermal Oxidative Stability Measurement via Quartz CrystalMicrobalance1This standard is issued under the fixed designation D7739;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 laboratory practice covers the quantitative determi-nation of surface deposits produced during the thermal oxida-tion of gas turbine fuels by monitoring the oscillation fre-quency of a quartz crystal during thermal exposure.In thispractice,“thermal oxidative stability”refers to the tendency ofa fuel to resist surface deposit formation during heating.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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.Summary of Practice2.1 A quartz crystal,fitted with gold electrodes,is fullyimmersed in test fuel contained within a reactor.An oscillatorcircuit,connected to the crystal,supplies energy to excite thequartz crystal and monitors its resonant frequency(nominally5 MHz)over time via a computer interface.The reactor isequipped with a magnetic stir bar,pressure gauge/transducer,oxygen sensor(not recommended for certain test conditions,see 4.11),and thermocouple to monitor and control testconditions.Prior to testing,the fuel is bubbled with the test gasfor 30 min to equilibrate.After equilibration,the reactor vesselis isolated and raised to test temperature and pressure.Asdeposits accumulate on the crystal surface during the run,thecrystal frequency decreases.The shift in resonance frequencycan be quantitatively related,in real time,to surface depositaccumulation via a variation of the Sauerbrey equation.23.Significance and Use3.1 The tendency of a jet fuel to resist the formation ofdeposits at elevated temperature is indicative of its oxidativethermal stability.This practice provides a technique for thesimultaneous determination of deposit formation and oxygenconsumption during the thermal oxidation of jet fuels and otherhydrocarbon liquids.The practice can be used to evaluate thethermal stability of fuels and to determine the efficacy ofadditives in inhibiting deposition or slowing oxidation,or both.Atest temperature of 140C and run length up to 16 h has beenfound to be effective for the relative evaluation of fuels andfuel additives.This practice has also been employed for otherhydrocarbon liquids,such as gasoline and diesel fuels,butadditional safety issues may need to be addressed by the user.4.Apparatus4.1 All dimensions without tolerance limits are nominalvalues.4.2 ReactorA T316,100 mL stainless steel reactor cylin-der with an internal diameter of 5.23 cm(2.06 in.)and a depthof 4.93 cm(1.94 in.).3,4A T316 stainless steel reactor headwith several openings(for example,gas inlet via dip tube,gasrelease fitted with a dial gauge or pressure transducer,thermocouple,safetyrupturedisk,frequencysignalconnection,sleeve for oxygen concentration probe).A 0.952cm(3/8 in.)hole is drilled in the center of the reactor head toaccommodate the frequency signal connectors.This hole shallhave a 0.952 cm(3/8 in.)clearance from any adjacent opening.4.3 SMA Coaxial Connector AssemblyThis assembly pro-vides the electronic connection through the reactor head to thequartz crystal and consists of several key parts(see Fig.1).Thecable from the oscillator(see 4.6)connects to a subminiatureversion A(SMA)adapter plug.4,5The SMA adapter plug1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.J0.03on Combustion and Thermal Properties.Current edition approved June 1,2011.Published August 2011.DOI:10.1520/D773911.2Klavetter,E.A.,Martin,S.J.,and Wessendorf,K.O.,“Monitoring Jet FuelThermal Stability Using a Quartz Crystal Microbalance,”Energy&Fuels,Vol 3,1993,pp.582-588.3The sole source of supply of the apparatus(Parr Instrument cylinder model#452HC8(100 mL)known to the committee at this time is Parr InstrumentCompany,211 Fifty-Third St.,Moline,IL 61265-1770.4If you are aware of alternative suppliers,please provide this information toASTM International Headquarters.Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.5The sole source of supply of the apparatus(Part No.3037M-1)known to thecommittee at this time is Coaxial Components Corp.,10 Davinci Dr.,Bohemia,NY11716-2601.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-