in its portfolio, with pumping speeds that cover the range from 25 to 26,500 cubic metres per hour.


Supply and removal of operating fluid can happen in three ways:

1. Non-recirculating operation
This is the simplest variant for operating a liquid ring vacuum pump and is used any time there is sufficient operating fluid available. The compression stage is constantly supplied with operating fluid. The fluid is then discharged together with the gas and the condensate.

2. Open fluid circuit
In an open circuit (fig. 4), the operating fluid is diverted into a liquid separator together with the gas after it exits the vacuum pump. Liquid and gas are separated there. The gas is discharged or transferred while fresh operating fluid is supplied in the liquid separator. This guarantees that there is enough liquid in the circuit and that the temperature does not rise. This type of open circuit can save up to 50 percent of the fluid when compared to non-recirculating operation.

Fig. 4: Dolphin liquid ring vacuum pump with an open operating fluid circuit (Source: Busch Dienste GmbH)

3. Closed fluid circuit
There is also a liquid separator downstream from the pump in a closed circuit (fig. 5). Gas is discharged from it while the operating fluid is diverted using a heat exchanger before it enters the vacuum pump again. The operating fluid is thus constantly cooled. This configuration saves up to 95 percent of the operating fluid. This means that only small amounts of fresh fluid need to be added via the liquid separator. We therefore recommend the closed circuit any time that sufficient operating fluid is not available or when as much operating fluid as possible should be conserved.

Fig. 5: Dolphin liquid ring vacuum pump with a closed operating fluid circuit (Source: Busch Dienste GmbH)

Tailored vacuum systems

Liquid ring vacuum pumps are exceptionally well suited for use as modules in vacuum systems and installations. Lower ultimate pressures can be realized in combination with steam jets. Technically and economically optimum solutions can be found for vacuum systems that are directly tailored to the individual application. Busch Vacuum Pumps and Systems has decades of experience in designing, configuring and building these types of systems, which are used in economical and safe operation worldwide in chemical processing technology, petroleum production and processing, power generation and many other areas. The individual Dolphin liquid ring vacuum pump sizes from Busch are available in different ATEX-certified versions.

Fig. 6: Vacuum system with five one-stage Dolphin liquid ring vacuum pumps for degassing process fluid (Source: Busch Dienste GmbH)