Oil Flushing Techniques for Converting to Biodegradable Fluids

"We will soon be converting our system to biodegradable fluids. Are there any specific steps that we should follow?"

Both new systems and used oil systems that are undergoing the installation of biodegradable fluids must be thoroughly drained, flushed and cleaned prior to the application of the new oil. Filters, strainers, magnetic plugs, reservoirs and breathers must be cleaned or replaced appropriately. In older systems, accumulated silt in reservoirs, sludge trapped in piping, hoses and valves, lacquer, old construction debris and other deposits must be thoroughly cleaned prior to the installation of the new biodegradable fluid.

New systems may contain welding slag in reservoirs, debris in piping, rubber and metal fragments in hoses and connections, rust preventives and other contaminants. These new oil systems must also be thoroughly cleaned and flushed (commissioned) with an appropriate flushing oil that will retain lubrication qualities but has an enhanced level of cleaning agents capable of loosening, suspending and solubilizing various contaminants.

Caution must be exercised when flushing systems that contain servo control valves or other components that have very fine tolerances. If the system is extremely contaminated, the flushing process may cause particles to loosen and pass through these components, and scoring damage and stiction (jamming) could result. In these cases, the valves must be bypassed during flushing.

There are advantages to using special flushing oils to thoroughly clean both new and old systems. These advantages include:

1. The system can be flushed and cleaned with a minimum of disassembly during the cleaning process.

2. The system can be operated at low speeds and pressures to allow for complete flushing of the entire system, including valves, cylinders, pumps, piping, filters and the reservoir itself.

3. The cleaned surfaces will be protected by the inhibitors and additives in the flushing oil.

4. There will be very little safety hazard to personnel.

5. The cost will be less than if disassembly is necessary. This flushing and cleaning process may take several hours or days, depending upon the complexity or size of the system. Flushing must continue, and filters changed during the process, until all evidence of old contamination is removed and the filters show no further evidence of contamination. Oil analysis will help determine when the system is clean.

Filters should be cut open and inspected thoroughly with a magnifying glass after each filter change during the flushing process. More information on flushing techniques may be found in ASTM D4174.