Phosphate-ester fire-resistant oil — captive power station

Phosphate-ester fluid in a captive power station's turbine governing system had been laying varnish down on the servo valves. The varnish film index -- the number that predicts whether a valve will move when it is told to -- had run far out of specification. On a governing system that number decides whether the machine follows load or trips, and replacing the charge was both the obvious answer and the expensive one.

The fluid was treated in place with the nano ultra-clean screening unit, connected to the governing-system reservoir rather than drained. The membrane stage removes the sub-micron and soft contamination that depth filtration cannot resolve: the varnish precursors already dissolved in the fluid, which no conventional filter element ever sees. Treating in place also avoided the flush and refill a charge replacement would have demanded.

The varnish film index came back down to 26, inside the limit. The governing system stayed on the same fluid instead of a new charge, and the measurement that had been trending the wrong way was brought back into specification without taking the unit down. What the station gained was not the number itself but what it stands for: a servo valve that moves when it is told to.