of the personnel who service and maintain theequipment. During installation, maintenance, andrepair of hydraulic equipment, the retention ofcleanliness of the system is of paramountimportance for subsequent satisfactory per-formance.The following maintenance and servicingprocedures should be adhered to at all times toprovide proper contamination control:1. All tools and the work area (workbenchesand test equipment) should be kept in a clean,dirt-free condition.2. A suitable container should always beprovided to receive the hydraulic liquid that isspilled during component removal or disassembly.NOTE: The reuse of drained hydraulicliquid is prohibited in most hydraulic systems. Insomelarge-capacity systems the reuse of fluid ispermitted. When liquid is drained from thesesystems for reuse, it must be stored in a clean andsuitable container. The liquid must be strainedand/or filtered when it is returned to the systemreservoir.3. Before hydraulic lines or fittings aredisconnected, the affected area should be cleanedwith an approved dry-cleaning solvent.4. All hydraulic lines and fittings should becapped or plugged immediately after discon-nection.5. Before any hydraulic components areassembled, their parts should be washed with anapproved dry-cleaning solvent.6. After the parts have been cleaned indry-cleaning solvent,they should be driedthoroughly with clean, low-lint cloths andlubricated with the recommended preservative orhydraulic liquid before assembly.NOTE: Only clean, low lint type I or IIcloths as appropriate should be used to wipe ordry component parts.7. All packings and gaskets should be replacedduring the assembly procedures.8. All parts should be connected with care toavoid stripping metal slivers from threaded areas.All fittings and lines should be installed andtorqued according to applicable technicalinstructions.9. All hydraulic servicing equipment shouldbe kept clean and in good operating condition.Some hydraulic fluid specifications, such asMIL-H-6083, MIL-H-46170, and MIL-H-83282,contain particle contamination limits that are solow that the products are packaged under cleanroom conditions. Very slight amounts of dirt,rust, and metal particles will cause them tofail the specification limit for contamination.Since these fluids are usually all packaged inhermetically sealed containers, the act of openinga container may allow more contaminants into thefluid than the specification allows. Therefore,extreme care should be taken in the handling ofthese fluids. In opening the container for use,observation, or tests, it is extremely important thatthe can be opened and handled in a cleanenvironment. The area of the container to beopened should be flushed with filtered solvent(petroleum ether or isopropyl alcohol), and thedevice used for opening the container should bethoroughly rinsed with filtered solvent. After thecontainer is opened, a small amount of thematerial should be poured from the container anddisposed of prior to pouring the sample foranalysis. Once a container is opened, if thecontents are not totally used, the unused portionshould be discarded. Since the level of con-tamination of a system containing these fluidsmust be kept low, maintenance on the system’scomponents must be performed in a cleanenvironment commonly known as a controlledenvironment work center. Specific informationabout the controlled environment work center canbe found in the Aviation Hydraulics Manual,NAVAIR 01-1A-17.HYDRAULIC FLUID SAMPLINGThe condition of a hydraulic system, as wellas its probable future performance, can best bedetermined by analyzing the operating fluid. Ofparticular interest are any changes in the physicaland chemical properties of the fluid and excessiveparticulate or water contamination, either ofwhich indicates impending trouble.Excessive particulate contamination of thefluid indicates that the filters are not keeping thesystem clean. This can result from improper filtermaintenance, inadequate filters, or excessiveongoing corrosion and wear.Operating equipment should be sampledaccording to instructions given in the operating3-10
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