The ICE power pack uses a diesel engine to power hydraulic pumps that drive pressurized hydraulic oil to deliver eccentric force to the vibratory hammer. The pump’s purpose is to pressurize the hydraulic fluid so that it will travel down the line and perform work on the other side. In an ‘open loop’ system such as used in the ICE equipment the hydraulic oil is drawn from a reserve tank and returned into the same tank after it has done its work. In a ‘closed loop’ system the fluid is brought directly back to the hydraulic pump after passing through a hydraulic filter. 
 
Fixed Displacement Pumps
A fixed-displacement pump has a set flow rate — every stroke of the motor moves the same amount of fluid. Fixed-displacement pumps have an efficiency of ±75% and generate a lot of heat. Fixed pumps have the advantage of providing a high rate of flow at relatively low pressures but when used to power a vibratory hammer there is a high likelihood of overheating the equipment when maximum driving pressure is achieved. This leads to damage to the hammer rapid degeneration of the oil damage to sealing materials such as O-rings which in turn causes leakage and therefore lots of downtime to cool the equipment down to avoid equipment breakdown.
 
Variable Displacement Pumps as used by ICE
In an axial variable-displacement pump as used by ICE power packs the flow rate and outlet pressure can be changed as the pump operates. 
The most common type of variable-displacement pump is the variable displacement axial  piston pump which is a variation of the gear pump in which the ‘gear’ is offset and the ‘cogs’ aren’t fixed but rather extend and retract as the gear turns allowing the pump to increase the pressure of the fluid by compacting it as it pushes the fluid through. As the hammer reaches its maximum pressure of about 350 bar during difficult driving the hydraulic flow is automatically reduced by 50% to ensure the hammer doesn’t overheat. The operator can then retract the hammer and pile a short distance until suitable working pressure is once again reached and then continue downwards driving.  This means that even during heavy driving the ICE hammer doesn’t heat up the hydraulic oil over 85 degrees Celsius. Therefore the risk of damaging the gearbox is eliminated the oil doesn’t spoil and the hammer can work continuously without needing time to cool off.
 
Simple fixed-displacement pumps are perfect for single jobs that need to be repeated indefinitely over long periods of time not for heavy duty equipment with changing flow requirements; variable-displacement pumps are necessary to power more demanding applications such as driving a vibratory hammer where the flow requirements vary with the driving conditions. When choosing a vibro make sure you chose a power pack with a variable pump!

The diesel engine in the power pack drives a number of hydraulic pumps. One or more pumps for driving the hydraulic engines and one pump for operating the clamping system. The pumps feed the oil to the vibratory hammer via a hydraulic hose set.