ASTM D7739-11 (2020) pdf free

04-10-2021 comment

ASTM D7739-11 (2020) pdf free.Standard Practice for Thermal Oxidative Stability Measurement via Quartz Crystal Microbalance.
This laboratory practice covers the quantitative determination of surface deposits produced during the thermal oxidation of gas turbine fuels by monitoring the oscillation frequency 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.The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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 appropriate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.
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, the crystal frequency decreases.The shift in resonance frequencycan be quantitatively related, in real time, to surface depositaccumulation via a variation of the Sauerbrey equation.
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.A test temperature of 140 C 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.ASTM D7739 pdf download.

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