Pile Design and Construction Practice, Fifth edition

Piling equipment and methods 81

Single-acting

hammer

Piling frame

Second-stage

driving completed

Leg guides

Diesel hammer

Ready for driving

First stage driving

complete

Pitching

pile

Trestle

guide

with gates

for 7 piles

Figure 3.9Driving piles in stages in conjunction with trestle guides.

Drop hammers are not used efficiently when operated from a pontoon-mounted piling frame
working in open waters, since the height of the drop cannot be controlled when the pontoon
is rising and falling on the waves. However, they can be used effectively in sheltered waters.
The American Vulcan hammer, which has been designed to operate within the leaders, is
shown in Figure 3.10.
The single-acting hammeris operated by steam or compressed air, which lifts the ram and
then allows it to fall by gravity. BSP single-acting hammers of the type shown in Figure 3.11
range in mass from 2.5 to 6 tonne with a maximum height of fall of 1.37 m; a solenoid
system can be used to control the drop of the hammer to avoid the operator fatigue of manual
operation. The single-acting hammer is best suited to driving timber or precast concrete
piles, since the drop of each blow of the hammer is limited in height and is individually
controlled by the operator. The single-acting hammer is suitable for driving all types of pile
in stiff to hard clays, where a heavy blow with a small drop is more efficient and less
damaging to the pile than a large number of lighter blows. The steam or air supply for both
single-acting and double-acting hammers should be at least 125% of the nominal consumption
stated by the hammer manufacturer. The Menck MRBS offshore hammers (Figure 3.12)