A hydraulic power unit, or HPU for short, consists of four main components: a prime mover (either an engine or electric motor), a pump, a valve, and a reservoir. Each of these componets are constructed together and form the main component in a dump trailer?s hydraulic circuit. Together, these components provide the flow (movement) that the system needs to operate. Bailey International, LLC offers complete HPU solutions including accumulators, auto hoists, battery chargrse, breathers, double acting units, hand pumps, pumping stations, reservoir tanks, dock levelers, single acting units, strainers and snowplows.