Reconditioning of phosphate ester hydraulic control fluids

摘要

A method and apparatus for recovering or maintaining phosphate ester type hydraulic fluids in serviceable condition which comprises sequentially filtering the fluid through at least a coalescer type filter and a mole-sieve type filter, preferably in conjunction with an activated charcoal powder filter and a small pore particle filter. In maintaining a hydraulic system in service, a small quantity of the hydraulic fluid is continually circulated from a reservoir through the filters and returned to the reservoir.