I've seen this around work before. It's like a dialysis machine for cleaning hydraulic fluid instead of changing it. It's basically a pump and lagre filter pack that they hook up to the hydraulic reservoir with two quick disconnects. Possiblities??

Interesting, we use a hydraulic purifier (PAL) on our Chinooks primarily to remove water/moisture in order to prevent corrosion in the flight control actuators and utility system. The PAL also have a set of filters that will catch 3 micron size particles and up.