Roots Liquid Ring Vacuum Pump (Unit)
Ordinary Roots vacuum pumps cannot be used alone, they must be paired with a suitable backing vacuum pump to form a unit. The backing vacuum pump's function is to reduce the pump's discharge pressure, thereby keeping the pressure differential between the pump's inlet and outlet, and the compression ratio, within a certain range. Because the pump's compression ratio is limited, selecting the right pumping speed for the backing vacuum pump is crucial. The pump's maximum compression ratio varies with discharge pressure. At high discharge pressures, the maximum compression ratio is 3:1. Roots liquid ring vacuum units, however, can achieve compression ratios of up to 40:1 or even higher.
