Impact Hammer - Hammer Trip System Operation (Refer To Figure H-7.)
There are four stages of operation for the hammer trip system. The hammer trip assembly,
moving along the hammer trip track rails and controlled by the hammer line (main hoist) of the
crane, is used to start the impact hammer by raising and automatically releasing the piston at a
predetermined height. The predetermined height is determined by the position of the trip
disengage lug on the impact hammer. To start the impact hammer with the hammer trip
assembly, the weight of the impact hammer must be fully on a pile, allowing the following
sequence to occur:
With the trip safety lever cord (attached to the trip safety lever) pulled and held in
place by ground personnel, the trip engage lug is engaged. The hammer trip
assembly is then lowered by the crane operator, via the hammer line (main hoist)
of the crane, along the hammer trip track rails. The lifting pawl is in the vertical
As the hammer trip assembly is lowered, the cam attached to the lever and shaft
encounters the trip engage lug mounted at the bottom of the upper cylinder. The
trip engage lug pushes the cam (and lever and shaft) upward, rotating the lifting
pawl towards the horizontal, engaged position via the connecting links.
The hammer trip assembly is raised by the hammer line (main hoist). The lifting
pawl is in the horizontal engaged position. The connecting links have passed
"over-center" and rest against the stop pin. The leaf spring assists in rotating the
connecting links over-center and retaining them in position. As the lifting pawl
engages the lifting collar on the piston, the piston is lifted and the connecting
links bear against the stop pin.
The crane operator continues raising the hammer trip assembly, via the hammer
line (main hoist), until the lever and shaft encounters the trip disengage lug. The
connecting links will rotate away from the over-center position and the stop pin,
causing the lifting pawl to rotate to the vertical disengaged position. The piston
The crane operator must cease hoisting the hammer trip assembly
as soon as the piston falls.
The normal position of the trip safety lever is used to lock out the hammer trip assembly in order
to use the hammer line (main hoist) to raise and lower the entire impact hammer. The trip
safety lever is held in its normal position by a spring (when the trip safety lever cord is not
pulled) and maintains the trip engage lug in the disengaged position. The trip disengage lug is
out of alignment with the hammer trip assembly and will not engage with the cam attached to
the lever and shaft.
The trip safety lever is used 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. This is
accomplished by pulling and holding the trip safety lever cord attached to the trip safety lever.
This will rotate the trip engage lug into position in order to engage with the cam attached to the
lever and shaft of the hammer trip assembly when lowered.
Rotating the lever and shaft with a wrench can manually disengage the hammer trip assembly.
H-22 Change 1