TM 5-3895-363-13&P
4. INTRODUCTION
The FEC Pile Hammer is a single acting diesel
hammer operating on the two-cycle diesel princi-
ple. It is completely self-contained and does not
require an auxiliary power source. Once started,
the hammer will continue to operate automatically
until the fuel supply is shut off or depleted.
4.1 OPERATING PRINCIPLE
The initial start up of the hammer requires the
piston (ram) to be raised to a point where the trip
automatically releases the piston, allowing it to fall
by gravity. As the piston falls, it activates the fuel
pump, which discharges a metered amount of fuel
into the ball pan of the impact block. The falling
piston also blocks the exhaust ports, and com-
pression of fuel trapped in the cylinder begins. The
compressed air exerts a pre-load force (approx.
44,000 lbs. or 20,000 kg.) to hold the impact block
firmly against the drive cap and pile. At the bottom
of the compression stroke, the piston strikes the
impact block, atomizing the fuel and starting the
pile on its downward movement. In the instant after
the piston strikes, the atomized fuel ignites, and the
resulting explosion exerts an even greater force on
the already moving pile, driving it further into the
ground. The reaction of the explosion rebounding
from the resistance of the pile drives the piston
upward. As the piston rises, the exhaust ports
Figure 1
4.1 OPERATING PRINCIPLE (cont’d.)
open, releasing the gases and force of the explo-
sion into the atmosphere. After the piston stops its
upward movement, it again falls by gravity to start
another cycle.
READ SECTIONS 5 THROUGH 8 BEFORE
STARTING THE HAMMER SECTION 9.
5. TRIPPING DEVICE
The tripping device (trip) which is mounted on the
starter guides is raised or lowered by the crane
operator. It serves two purposes:
A) To raise the entire hammer along the lead.
B) To start the hammer.
Figs. 1 & 2 show the tripping device and provide
the nomenclature and location of its related parts.
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