Impact Hammer - Direct Drive System Operation (Refer To Figure H-10.)
The direct drive system transfers the impact 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 the recoil dampening system and
striker plate (driving head). During operation of the impact hammer the following sequence
At the bottom of the piston downstroke, the nose of the piston strikes the top of
the impact block in the lower cylinder.
The impact block moves unimpeded and strikes the top of the striker plate in the
direct drive assembly, transferring the impact energy from the impact block to the
The impact energy from the striker plate is then delivered to the pile being driven
by the striker plate. The striker plate evenly distributes and transfers the impact
energy to the pile head to minimize mushrooming/splitting of the piling.
The pile is driven into the soil.
The recoil dampening system, consisting of the six cushion rings and cushion
compression ring in the direct drive assembly, dissipates the rebound energy to
allow up to 95% of the impact energy to be transmitted to the pile and only 5% of
the rebound energy back to the impact hammer.
The following general safety precautions should be observed during installation and operation:
Safe pile driving piles is a three-person operation. Always use two ground
assistants and one crane operator for set-up and operation. Accept direction
from only one person. However, obey a stop signal from anyone in the vicinity.
All other non-essential personnel should be cleared from the area.
Ensure all mounting hardware is in place and tight. Ensure no loose articles such
as tools, clothing, and shipping/lifting equipment are resting on the impact
Check the working pile to be sure it is strong enough to withstand the force of the
Verify that driving a pile will not cause damage from vibration to adjacent
When unloading or loading the shipping/storage container, visually inspect each
component for damage.
Observe the following precautions before starting the impact hammer:
Always wear personal protective equipment including ear and eye protection, work
gloves, and a hard hat.
Do not use starting fluids as a cold weather starting aid as they can cause
excessive piston stroke and damage to the impact hammer.
Never stand directly under the pile driving head.
Do not start the impact hammer until it is squarely positioned over the pile.