Hydraulic motors are used in any app requiring rotational force, also known as torque. A hydraulic motor converts hydrostatic energy into mechanical energy by pressing vanes, gears or pistons attached to a crankshaft.
Hydraulic motors are utilized for most applications now such as for example winches and crane drives, wheel motors for military vehicles, self-driven 
cranes, excavators, conveyor and feeder drives, cooling fan drives, mixer and agitator drives, roll mills, drum drives for digesters, trommels and kilns, shredders, drilling rigs, trench
Hydraulic motors are rotary actuators that convert hydraulic, or fluid energy into mechanical power. They function in tandem with a hydraulic pump, which converts mechanical power into liquid, or hydraulic power. ... Fixed-displacement motors drive lots at a constant speed while a constant input stream is provided.