The piston is a free piston that provides the impact energy delivered to the pile. The impact
block is located at the bottom of the lower cylinder and relays the energy from the piston to the
pile via the direct drive assembly. Piston compression rings and impact block compression
rings are installed to assist in compression and to prevent exhaust gases from entering the
upper cylinder and escaping from the bottom of the lower cylinder.
The upper and lower cylinders are porous-chrome-lined and bolted together to form cylinder that
enclose the piston and impact block. An o-ring, installed between the upper and lower
cylinders, provides an air-tight seal.
The upper cylinder contains the catch ring cap, fuel tank, and hammer trip system. Lifting lugs
are located on the front of the upper cylinder. A red-colored piston transportation pin, normally
housed in the tool box, can be installed in the top part of the upper cylinder to secure the piston
for shipping/transportation purposes. A red-colored weather cap with securing strap, normally
housed in the tool box, can be installed on the catch ring cap of the upper cylinder to keep out
moisture and foreign objects.
The lower cylinder contains the four upper and lower gibs, intake/exhaust port, cooling fins, fuel
injection system, fuel system guard, oil lubrication system, and lubricating oil tank. The lower
cylinder also contains the internal combustion chamber that is created by the ring-shaped area
on the nose of the piston and the cylinder walls. A cushion housing guide ring and cushion
housing guide ring support are located in the bottom of the lower cylinder. A red-colored
weather cap, normally housed in the tool box, can be installed on the intake/exhaust port to
keep out moisture and foreign objects.
The hammer trip system consists of the hammer trip assembly, hammer trip track rails, trip
disengage lug, trip safety lever and trip engage lug, trip safety lever cord, and trip transport bolt.
The hammer trip assembly, sliding along the hammer trip track rails and hoisted up and down
by the hammer line (main hoist) of the crane, contains a trip mechanism that is used to start the
impact hammer by raising and automatically releasing the piston at a predetermined height.
The trip mechanism of the hammer trip assembly consists of a lifting pawl, lever and shaft,
connecting links, stop pin, and cam mounted in a housing and backplate. The trip engage lug,
located on the trip safety lever in the lower portion of the upper cylinder, engages the trip
mechanism in the hammer trip assembly when it is lowered to allow lifting of the piston. The trip
disengage lug, located at the top of a slot in the upper cylinder and part of the upper cylinder,
activates the trip mechanism and causes the piston to be released when the hammer trip
assembly is raised to the predetermined height. The red-colored trip transport bolt, normally
housed in the tool box, can be installed in the hammer trip assembly to secure the hammer trip
assembly to the hammer trip track rails for shipping/transportation purposes.
The trip safety lever is used by ground personnel to engage the trip engage lug to allow the
hammer line (main hoist) to raise the hammer trip assembly (and piston) in order to start the
impact hammer. The trip safety lever cord, attached to the trip safety lever, is used to control
the position of the trip safety lever. When in the normal position (trip safety lever cord not
pulled), the trip safety lever locks out the hammer trip assembly allowing the hammer line (main
hoist) to raise and lower the entire impact hammer.
The direct drive system transfers the driving energy developed by the piston and impact block in
the lower cylinder to the pile being driven. This is provided by the direct drive assembly
connected to the bottom of the lower cylinder that houses a recoil dampening system and striker
plate (driving head). The direct drive assembly consists of the upper and lower drive housings
and is capable of driving up to 18-inch (45.7 cm) piles. Lifting lugs and adapter holes (used to
secure the square (concrete) and sheet pile adapters) are provided at the top of the direct drive
assembly. A blow count recorder and waste fuel drip tank are also installed at the top of the
direct drive assembly.
H-12 Change 1