Abstract: The present invention relates generally to a hydraulic braking system for use in equipment such as cranes that rotate about a fixed base. The braking system described herein utilizes a twin piston hydraulically activated system wherein separate service and parking brake pistons are applied to opposite sides of a common brake pack. The two braking pistons may be independently actuated. The brake pack consists of interleaved rotor disks (friction disks) which are splined to a central rotating shaft and stationary (stator) disks which are secured against movement by interlocking them with the casing of the device. The brake pack is movable axially such that in operation an active parking brake piston presses against the brake pack which moves until it is supported on its reverse face by a passive service brake piston. Similarly, when the service brake is applied the brake pack moves and is supported on its opposite face by a passive parking brake piston.