The weight of the hammer is lifted by cable operation, by steam or by hydraulic pressure. To start the single acting hammer, the piston is lifted to a preset height and automatically released. The falling piston compresses the air in the compression chamber and activates the fuel pump to spray fuel on top of the impact block. The impact of the piston on the impact block atomizes the diesel fuel, which ignites in the highly compressed air. The explosive energy throws the piston upwards thus driving the pile downward and restarting the hammer cycle.
Diesel hammers perform especially well in cohesive or very dense soil layers.
Driving caps of flat anvil blocks are necessary to protect the pile heads during driving. The correct denomination should be double acting hydraulic hammer. This type of hammer consists of an enclosed ram which is lifted by hydraulic pressure. On the downward stroke, additional energy is delivered to the ram, producing an acceleration of 2 g. The maximum stroke of 1 meter thus correspond to a free fall drop of 2 meters.