Changing Compatible Fluid in Hydraulic Power Units

**Document as reference only provided by Tronair. For up to date procedures, please request document from manufacturer.

Note: This procedure is acceptable for changing the following fluids: MIL-PRF-5606, MIL-PRF-83282, MIL-PRF-85257(only FROM this fluid).

1. Remove incoming electrical power from hydraulic power unit.

2. Remove cap from reservoir drain assembly and open drain valve to remove fluid from reservoir.

3. Remove plug fitting in lower portion of the cooler to drain fluid from cooler.

4. Remove and drain pressure filter bowl.

5. Drain return filter assembly:

A. Remove element from filter assembly and either:

I. Suck fluid from filter bowl or,

II. Remove top panel from unit and unscrew filter bowl from assembly and drain.

6. Return unit to running condition using original filter elements, replace fittings and close valve at the bottom of the reservoir.

7. Drain external pressure and return hoses, then connect external pressure hose to external return hose.

8. Add minimum amount of new fluid to unit reservoir.

9. Apply electrical power to unit, open bypass valve, put unit in hpu reservoir mode, make sure return and pressure ball valves are fully open, and start unit.

10. Open flow control valve to 1⁄2 maximum flow position.

11. Make sure ball valves on back of unit are open, close bypass valve and allow fluid to cycle for 30 minutes.

12. Shut down unit and repeat draining procedure (go to step 1).

13. Replace filter elements with new elements.

14. Change labels on unit to reflect the new fluid type.

15. Fill unit reservoir (do not exceed maximum level).

16. Refer to operation manual for bleeding procedure to eliminate trapped air from system.

17. Send a fluid sample for evaluation to the new fluid manufacture, if acceptable;

18. Unit is ready to return to service, else repeat starting at step 1.

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