The HHK AL-series is a new generation of hydraulic impact hammers with an adjustable stroke of up to 0.8 m (2.6 ft) and an open hammer body. This hammer type can be delivered also with a stroke of 1.2 m (3.9 ft). The open hammer body makes the hammer lighter and allows higher pile weights than the heavier traditional free-fall hammer. Because of the lower stroke, the hammer is also shorter.
The hammer is suitable for driving all types of piles: precast concrete, steel tube, sheet and timber piles. The design of the hammer frame and drive cap makes for low impact noise and less vibration while piling. All impact energy is concentrated in the centre of the pile. The construction of the hammer makes it possible to use biodegradable hydraulic oils. The hammer is easy to connect to different hydraulic systems. It can be operated by the hydraulic system of the rig or by a separate power pack. The hammer can be mounted on all kinds of leaders, or can be freely suspended.