Challenge The hydraulic oil in the braking system of trains must meet a very high standard of cleanliness, NAS 5. Solution Eastern Fluid Power Inc. custom designed a filtration unit to exceed this level. This is the last test a train undertakes before going into service. The oil is filtered and monitored by an integrated particle counter, which records and prints out a report on the cleanliness achieved. These units are sold globally. Result Validation of the required NAS 5 cleanliness is achieved.