STP1339: Rust Inhibitor Contamination-Related Problems in Military Aircraft Hydraulic Systems

    Sharma, SK
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio

    Snyder, CE
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio

    Gschwender, LJ
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio

    Liang, JC
    The University of Dayton Research Institute, Dayton, Ohio

    Schreiber, BF
    The University of Dayton Research Institute, Dayton, Ohio

    Pages: 11    Published: Jan 2001


    Abstract

    Stuck servovalves were observed during pre-flight checks in some aircraft using MIL-PRF-83282 hydraulic fluid. Analysis of hydraulic fluid samples and stuck valves as described in the paper provided a link between valve failures and barium dinonylnaphthalene sulfonate (BSN) content of the hydraulic fluid. The BSN contamination was traced to residual MIL-PRF-6083 preservative fluid that had not been drained from components before installation on the aircraft. The hypothesis was validated by laboratory tribological experiments using a reciprocating tribometer and grazing angle microscope Fourier transform infrared spectroscopy. Corrective actions included reemphasizing procedures to drain MIL-PRF-6083 from components and establishing a 10 ppm maximum limit for barium in new MIL-PRF-83282.

    Since the corrective actions were taken, no valves have locked up, further validation that the preservative fluid, MIL-PRF-6083, as a contaminant in the operational aircraft, is the root cause of the valve lockups. The recommended corrective actions were: 1) removing and cleaning the hydraulic valves; 2) assuring that the barium content of the aircraft hydraulic fluid does not exceed 15 ppm.

    Other factors besides the presence of BSN which contributed to the valve-sticking problem included: the elevated hydraulic fluid temperature, the valve design and materials, and the duty cycle. The simplest and most cost-effective solution to the problem was limiting the amount of BSN in the aircraft hydraulic system. Other aircraft hydraulic systems problems perceived to be caused by BSN contamination are discussed.

    Keywords:

    Hydraulic Components, Hydraulic Fluids, Barium Dinonylnaphthalene Sulfonate, Stuck Servovalve, Infrared Spectroscopy


    Paper ID: STP38297S

    Committee/Subcommittee: D02.N0

    DOI: 10.1520/STP38297S


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