HYDRAULIC FLUIDS:Control of Contamination

Control of Contamination

Maintaining hydraulic fluid within allowable contamination limits for both water and particulate matter is crucial to the care and protection of hydraulic equipment. Filters will provide adequate control of the particular contamination problem during all nor­ mal hydraulic system operations if the filtration system is installed properly and filter maintenance is performed regularly. Filter maintenance includes changing elements at proper intervals.

Control of the size and amount of contamination entering the system from any other source is the responsibility of the personnel who service and maintain the equipment. Dur­ ing installation, maintenance, and repair of hydraulic equipment, the retention of cleanli­ ness of the system is of paramount importance for subsequent satisfactory performance.

The following maintenance and servicing procedures should be adhered to at all times to provide proper contamination control:

1. All tools and the work area (workbenches and test equipment) should be kept in a clean, dirt-free condition.

2. A suitable container should always be provided to receive the hydraulic liquid that is spilled during component removal or disassembly.

Note: The reuse of drained hydraulic liquid is prohibited in most hydraulic systems. In some large-capacity systems the reuse of fluid is permitted. When liquid is drained from these systems for reuse, it must be stored in a clean and suitable container. The liquid must be strained and/or filtered when it is returned to the system reservoir.

3. Before hydraulic lines or fittings are disconnected, the affected area should be cleaned with an approved dry-cleaning solvent.

4. All hydraulic lines and fittings should be capped or plugged immediately after disconnection.

5. Before any hydraulic components are assembled, their parts should be washed with an approved dry-cleaning solvent.

6. After the parts have been cleaned in dry-cleaning solvent, they should be dried thoroughly with clean, low-lint cloths and lubricated with the recom­ mended preservative or hydraulic liquid before assembly.

Note: Only clean, low-lint type II or I cloth as appropriate should be used to wipe or dry component parts.

7. All packing and gaskets should be replaced during the assembly procedures.

8. All parts should be connected with care to avoid stripping metal slivers from threaded areas. All fittings and lines should be installed and torqued according to applicable technical instructions.

9. All hydraulic servicing equipment should be kept clean and in good oper­ating condition.

Some hydraulic fluid specifications contain particle contamination limits that are so low that the products are packaged under clean-room conditions. Very slight amounts of dirt, rust, and metal particles will cause them to fail the specification limit for con­ tamination. Since these fluids are usually all packaged in hermetically sealed contain­ ers, the act of opening a container may allow more contaminants into the fluid than the specification allows. Therefore, extreme care should be taken in the handling of these fluids. In opening the container for use, observation, or tests, it is extremely important that the can be opened and handled in a clean environment. The area of the container to be opened should be flushed with filtered solvent (petroleum ether or iso­ propyl alcohol), and the device used for opening the container should be thoroughly rinsed with filtered solvent. After the container is opened, a small amount of the mate­ rial should be poured from the container and disposed of prior to pouring the sample for analysis. Once a container is opened, if the contents are not totally used, the unused portion should be discarded. Since the level of contamination of a system con­ taining these fluids must be kept low, maintenance on the system’s components must be performed in a clean environment commonly known as a controlled environment work center.

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