Vibration free hydraulic pressing allows up to 4 single piles to be driven at a time. Piles are manoeuvered into position with pitching chains or a winch at the rig mast then gripped in the hydraulic jaws. The pressing force is achieved by using the weight of the piling rig as the reaction force. Hydraulic rams drive the piles in increments of 800mm individually before adjusting and repeating the process. Further kentledge force is provided by using previously driven piles. Pressing forces of up to 800kN can be achieved, which is particularly useful in cohesive strata. Pile installation is often preceded by pre-auguring in very stiff clays.
There is no limit potentially on the length of pile which can be installed, unlike with other silent or vibration free techniques. Additional sheets can be jointed, allowing pile lengths greater than the rig mast height, the only limiting factor being the available reaction forces needed to press the piles. The installation process is suited to both U and Z section piles, and is particularly suited to smaller schemes.