Downloaded from https://www.everyspec.com FM 1-509 A kit has been developed to sample fluid for contamination. Fluid samples are taken periodically and forwarded to area laboratories for analysis. The laboratory checks for viscosity, corrosion, oxidation, emulsion, fire resistance, vapor pressure, flash point, water, hydrolytic stability, viscosity-temperature coefficient, neutralization number, and pour point. Contamination checks should become routine; check for dirt, metal, and visible solids every time a unit is removed or disassembled. Normal contamination checks for most aircraft are made by examining the condition of the filter elements.
For example, a clogged filter or an extended filter indicator pin is a symptom of contaminated fluid. These findings, as well as pump failures, require flushing of the system. To prevent contamination-- Cap or plug all open connections when removing a part. Never use dirty rags to wipe off connections. Clean and deburr new tubing and fittings before installing them. Store new or overhauled parts in sealed containers. Fill the pump with hydraulic fluid before installing it. Take good care of test stands and ground equipment. Handle flexible hydraulic hoses carefully.
Particles from the hose walls may enter the system when hoses are kinked, run over, or when quick-disconnect couplings are not cleaned before being joined. CAUTION NEVER REUSE FLUID THAT HAS BEEN DRAINED FROM AN AIRCRAFT HYDRAULIC SYSTEM OR COMPONENT. Maintenance. A hydraulic unit, when disassembled and overhauled, must be cleaned with a suitable solvent to remove dirt, grit, sludge, or other foreign matter. Always check the applicable technical manual to find the correct procedure for disassembling, cleaning, assembling, and testing a unit.
If a particular type of solvent is not specified, use PD-680 to clean units operating with petroleum-base fluid; denatured alcohol for units using vegetable-base fluid; and trichloroethylene for units using synthetic-base fluid. Whatever type of solvent is used, thoroughly soak and wash the unit and its internal parts in the solvent. Use a small brush on the inside passageways and chambers; be sure that its bristles are not so stiff that it scratches the metal. All parts must be dried completely with compressed air or a lint-free cloth before being assembled. some solvents are very flammable, proper precautions should be taken to store them in tightly sealed containers.
The work area must be well ventilated when using solvents indoors. 1-9