Pilot-operated valve with floating piston

A pilot-operated proportional cartridge valve (10) that has low internal leakage and long life, without requiring close spool clearances that add cost to comparable prior art valves. The flow control valve uses two axially spaced-apart spring energized wiper seals (70, 72) which floatingly support a flow control piston (58) within a cylindrical chamber to allow transaxial shifting movement of the piston for proper alignment with mating components, such as a valve seat (56). The spring energized wiper seals are preferably oriented in opposite directions for sealing against pressure differentials at opposite ends of the valve piston. In a preferred embodiment, the seals are spring energized cup seals.