01 July 1997
a. Crane. After the hammer, the crane is the single most important part of a pile driving system. Its
proper selection is essential for correct, safe, and economical installation of the piling.
(1) Cranes for Impact Hammers. The crane must have adequate lifting capacity to lift the hammer,
leaders, driving accessories, and pile. It must have three lifting lines, one for the hammer, one for the pile, and
one for the leaders (if swinging leaders are used; if not, two will suffice). This lifting capacity must be adequate
to lift all of the parts of the system no matter how far the crane is boomed out to drive the piling in question.
This is important because frequently piling must be driven from a spot which is relatively far from the crane
cab, and thus the maximum capacity of the crane in the highest boom position is not available for the particular
job. Cranes for pile driving must have superior side loading capacity, and this must be watched for, especially
with hydraulic cranes.
(2) Boom Point Connection. With both underhung and fixed leaders, the boom point connection is
important. Inadequate or poorly designed and manufactured boom point connections can lead to accidents
and job delays. Types of boom point connections are shown in figure 3-23.
(3) Cranes for Vibratory Hammers. Vibratory hammers are generally not operated in leaders but are
free hanging from the crane. However, it is important that cranes for vibratory hammers have adequate
capacity to both lift the hammer and pile for driving and any possible extraction load that might be needed to
pull piles out of the ground. The boom must also be able to withstand any residual vibration transmitted to it by
b. Power Systems. All external combustion hammers and the vast majority of vibratory hammers require
some kind of power source to operate the equipment. This power source depends upon the nature of the
(1) Air/Steam Hammers. Except for the largest marine rigs, most air/steam hammers today are
powered by air compressors. These can be mounted either on the ground or, more commonly, on the back of
the crane as a substitute for the counterweight. Boilers still used with pile hammers are either of the fire tube
Scotch marine type or the vertical water tube Raymond type. Both compressors and boilers should be
configured in accordance with the manufacturer' recommendations. Also, essential for air/steam hammers is
a three-way shut-off valve that can blow pressure out of the lines after the hammer is stopped or in an
emergency, and a line oiler of the sight feed or pump type to provide a continuous stream of atomized oil to
(2) Hydraulic Vibratory Hammers. For a variety of reasons, hydraulic systems have become dominant
for vibratory hammers. These systems use a diesel engine to drive a hydraulic pump, which in turn drives the
motor on the exciter. A reservoir is used to store hydraulic fluid, to make up fluid in case of leakage, and to
assist in the cooling of the fluid. A system of valves is used to control the fluid flow, both in starting and
stopping the machine as well as during operation. Beyond these basics, there are specific differences
between the various hydraulic power packs available.
(a) Pump Drive and/or Gearbox. The hydraulic pump is connected to the engine through a pump
drive. Sometimes this pump drive is a gearbox acting as a speed changer to optimize the pump, but in others,
a direct drive is employed, eliminating gear losses.
(b) Clamp Pumps. Most units have separate pumps for the hydraulic clamps, but some integrate
these into the main power source.
(c) Variation of Frequency and Force. Both of these can be varied either by using variable
displacement pumps in the power pack or by simply varying the engine speed. Variable displacement pumps
can have very sophisticated flow control mechanisms.
(d) Control Type. These units can employ air, electric, or manual controls for the hydraulic