Claw Vacuum Technology Brings Energy and Maintenance Savings in Lowering Groundwater
In the process, GW Kanalabsperrung offers its customers customized service that includes installation of the system with all filters and hose lines through to daily monitoring of functionality and correct operation. This has enabled GW Kanalabsperrung to build up a customer base throughout the entire state of North Rhine-Westphalia.
Until now, systems from different manufacturers were sold. In 2015, Managing Director Gerhard Wagner himself developed a new system and, after many years of experience with different vacuum pumps, he decided to use the MINK claw vacuum technology from Busch.
Whilst the first systems were delivered to customers last year, GW Kanalabsperrung unveiled this new system approach to a larger audience of specialists for the first time at Bauma 2016 in Munich.
To prevent groundwater from penetrating an excavation pit or, alternatively, to prevent an excavation pit from having to be drained, suction pipes with filters are placed around the pit one to two metres apart from each other. These can be up to six to seven metres deep in the ground. The number of these suction pipes, their distance from one another and the filters used depend on ground conditions.
Fig. 2: The operating principle of the vacuum method for groundwater lowering: 1 Groundwater lowering system, 2 Manifold, 3 Excavation, 4 Suction pipe, 5 Suction filter, 6 Groundwater. Source: Busch Vacuum Soultions.
- When the system is turned on, the vacuum pumps pump all the air out of the container and the entire pipe network.
- The vacuum created by this process sucks groundwater from the vicinity of the individual filters, which lowers the overall water table.
- The water is sucked into the container by the vacuum.
- As soon as a certain level is reached in the container, the water pump, usually a centrifugal or submersible pump, begins to pump the water out of the container and directs it into the sewer system or a body of water via a hose.
- Once the level of water in the container is reduced to a minimum, the water pump shuts off and the vacuum once again sucks groundwater into the vacuum container.
This process repeats itself constantly around the clock to ensure that the excavation pit is drained during the construction phase. Depending on how long the excavation lasts, this process can go on for weeks to months.
Despite circulatory operation, fresh water must be regularly fed into the system during operation of the liquid ring vacuum pump. In practice, this can be difficult during excavation work. Groundwater that has been sucked in must not enter this circulatory system in any case because, despite filtering, groundwater often carries fine and abrasive sand that quickly causes wear on the liquid ring vacuum pumps.
Fig. 3: Cross section of a dry, non-contact Mink claw vacuum pump. Source: Busch Vacuum Solutions.
Whereas the oil in oil-lubricated rotary vane vacuum pumps creates a protective film inside the pump, protecting it against corrosion,
dry-running rotary vane vacuum pumps always risk becoming corroded during downtimes, in which case they fail to start. Even after a break in operation of only one day, the vanes can become stuck in the rotor. When starting, they can break and lead to greater damage inside the vacuum pump.