Pile Design and Construction Practice, Fifth edition

have masses ranging from 8.6 to 125 tonne with a maximum stroke of 1.75 m. They are fully

automatic with infinitely variable stroke. By adding a belled out section beneath the

hammer, Seacore have developed a rig capable of driving piles up to 4 m diameter into pre-

drilled holes for the ‘monopile’foundations for offshore wind turbine towers as in

Figure 3.13.

The characteristics of the various types of single-acting hammer are shown in Table 3.1.

The ram of hydraulic hammersis raised by hydraulic fluid under high pressure to a

predetermined height, and then allowed to fall under gravity or is forced down onto the pile

head. In the BSP CX and CG hydraulic hammers (Figure 3.14), a hydraulic actuator is

activated by a solenoid-operated control valve which raises the piston rod. At the required

stroke height the flow of the hydraulic fluid is cut off. Pressures within the actuator then

equalize allowing the ram to decelerate as it approaches the top of its stroke. The hammer

then falls freely under gravity and repositions the piston rod for the next stroke. Using a

remote control panel these hammers can deliver an infinitely variable stroke and blow rate

within the limits stated. BSP also manufacture two double-acting hammers for driving steel

sheet piles and bearing piles with blow rates of 84 blows per minute.

82 Piling equipment and methods

Figure 3.10Vulcan drop hammer.

571

159

Sling hooks

for packing

Jaws engaging

with leaders

Lifting hole

457

(18")

1 016(40")

(6 )

1 " 4

(22 )^12 "