Little water and a high vacuum

When it is necessary to lower groundwater from depths of more than 7 meters, many dewatering pumps quickly reach their limits. If the situation is aggravated by the fact that the groundwater only flows slowly, any groundwater lowering unit is faced with a tricky task.

Vacuum-assisted diesel units can certainly provide relief via a separate vacuum pump, because the vacuum is built up outside the centrifugal pump with the aid of a vacuum generator. Piston or rotary lobe pumps, for example, generate the vacuum in the pump body and are technically limited at a low recharge rate, especially at depths beyond 6 meters.

Therefore, the following question is valid:

What are the better ways to deal with these parameters?

Hüdig has been using rotary vane vacuum pumps for decades. These generate a constantly high vacuum (-0.99 oil-lubricated, -0.92bar dry-running) and in addition they pump a large volume of up to 250m³/h (depending on type and size).

In the electrically operated HC488, both submersible motor pumps and rotary vane vacuum pumps are used. The highlight here is that the individual components of the unit are connected to each other in an automatic circuit. The individual units are controlled fully automatically via electrodes - if little water arrives, the vacuum is maintained, but the submersible motor pumps are switched off. As soon as the boiler of the unit is sufficiently filled with water, it is emptied by the water pumps - as said, everything is fully automatic! By using electrical energy and a sophisticated control system, only the pumps that are actually needed switch on and off again in time. This increases the efficiency of the entire unit and thus saves energy resources and, incidentally, the client's wallet. All in the spirit of sustainability.

During a project near Rotterdam, our customer found the conditions described above. The groundwater flowed slowly at a depth of more than 7m and threatened to delay the project. Only by deploying several HC488s at different strategic positions on the site, it was possible to control the inflowing water with little energy input.