MENCK

A single acting hammer lifts the ram weight and then allows it to drop, with only gravity to accelerate the weight downwards. On a double acting hammer, after lifting the ram is also hydraulically accelerated downwards to achieve a higher velocity before impact, thereby resulting in a higher impact energy.

The ballast is required for under water pile driving to compensate for the buoyancy of the hammer, as the hammer needs a certain minimum weight to counteract the hydraulic downward acceleration forces.

In the past steam boilers were available on many vessels. Technological developments mean that steam boilers are no longer available. Steam hammers also have a greater impact on the environment than hydraulic hammers. The transition to hydraulic drive systems has enabled the design of more efficient and compact hammers that work under water.

All MENCK hydraulic hammers can be operated both above and under water which allows for continuous pile driving starting above water and ending under water. To achieve this the hammer will be equipped as an underwater hammer for the entire driving activity.

A typical pile driving spread for above water driving consists of the hammer, hydraulic power pack(s), hydraulic hoses and umbilical, workshop container and as an option a winch(es) for handling of the operating lines.

A typical pile driving spread for underwater driving consists of the hammer with underwater ballast, hydraulic power pack(s), an air compressor, hydraulic/air hoses and umbilical, workshop container and as an option a winch(es) for handling of the operating lines.

A typical deep water pile driving spread consists of the hammer surrounded by a special electro-hydraulic underwater power pack, winch for the highly integrated umbilical, air compressor and auxiliary containers.

First, operating lines are the hydraulic hoses which supply the hammer with the hydraulic energy provided by the power pack. They consist of supply and return line(s). Second, there is an umbilical which is a cable for energy supply to the valves, control and supervision. In case of under water operation there is also an air hose which supplies the hammer with pressurized air.

Typically electricity is provided from the on-board mains supply.

For underwater pile driving an air supply is necessary to fill the hammer housing and upper part of the pile sleeve with a slight overpressure against the outside hydrostatic pressure at the given water depth.

The use of biodegradable oil is generally possible. As the behaviour of biodegradable oil is quite different, depending on its base every special type of oil needs to be checked and approved by MENCK to avoid operational issues and damage to the hydraulic system.

The maintenance intervals depend on the hammer components which experience different wear and tear. These intervals are given in the maintenance manual. They range from frequent intervals for easy checks to intervals of 400,000 blows when some main wear components are replaced for safety reasons.

Pile driving deeper than approx. 300 m (1000 ft) is generally considered to be deep water driving. This is usually a far more complex project and as a result is more expensive than conventional shallow water driving.

The installation of inclined (non-vertical) piles requires special investigation and project planning dependant on the angle of inclination. Most important is the appropriate guidance of the hammer on the inclined pile to avoid misalignment. Moreover, a stick up analysis should be considered for the pile to avoid overloading.

The impact energy of a hammer is generated by a downward acceleration due to gravity and hydraulic forces. The boost option increases the hydraulic force and hence the impact energy of the hammer. The boost option is not a feature of the hammer itself, it is generated by valves in the power pack or as a separate unit. The boost option is a feature to temporarily increase the impact energy for a short period in case the nominal energy is not sufficient to drive a pile to final penetration. It is not available for continous use.