Rotary vacuum pumps, liquid ring

Positive displacement pumps diaphragm vacuum pumps, liquid ring vacuum pumps, rotary vane and rotary piston vacuum pumps as well as Roots vacuum pumps (dry compressing claw and screw pumps are not yet mentioned here but also belong to this group of pumps). 

The most used mechanical vacuum pumps or compressors are reciprocating, liquid-ring, rotary-vane, rotary blower, rotary piston, and diaphragm. 

Rotary blower—liquid ring vacuum pump... 

Vacuum capacities and operating ranges, table, 344, 355 Ejectors, 344, 357 Integrated systems, 344 Liquid ring pumps, 344 Rotary lobe blowers, 344 Rotary piston pumps, 344 Rotary vane pumps, 344 Vacuum equipment, 343 Applications diagram, 352 ASME Code, 344 Pumps, 382 Steam jets, 357 Vacuum flow,... 

Roots pumps must be combined with a backing pump/pump-set for normal vacuum applications. Used in combination with any of a range of backing pumps (oil-sealed rotary, dry, liquid-ring) Roots pumps allow higher pumping speeds and lower pressures to be achieved than can be obtained by the backing pump on its own. 

For vacuum production reciprocating, rotary positive displacement and liquid ring pumps can be used to pressures from 200 to 10 mmHg. Alternatively steam ejectors can be used when water self is a product, as in evaporation of aqueous solutions. The residual pressures can be lowered under 1 mmHg by using several ejectors in series. 

Vacuum systems with rotary vane vacuum pumps may be used where the process requires vacuums < 50 mbar or if liquid ring vacuum pumps cannot be used in the installation. These vacuum systems are designed to separate out as much of the process vapours and particles as possible on the intake side or to condense the process vapours into the atmosphere as moist air. Rotary vane vacuum pumps may be operated as recirculahng lubrication or blow-by vacuum pumps. The vacuum pump is built with a rotor turning eccentrically in a cylinder. The rotor has axial slots and rotating vanes are pressed against the cylinder by centrifugal force in these slots (Fig. 3). 

The liquid ring and rotary vane vacuum pumps that have long been used in many methods can now be replaced with vacuum pumps without pump... 

The liquid ring vacuum pump shares but one trait with the rotary vane vacuum pump — an eccentrically mounted rotor, driven by an electric motor. 

But the liquid ting pump has (1) multiple vanes (fins) vs. a single one (often) for the rotary vane pump (2) no vanes which contact the perimeter of the cavity as it s essential for aU to do so in a rotary vane pump (3) a point of entry for the vapor within the rotor and not at the circumference of the casing as is typical of other vacuum pumps and (4) a "pool" of liquid which acts a "collector" to remove vapor from the work chamher and also as a piston to compress the vapor not a good descriptive diagram of a liquid ring vacuum pump is shown in Figure 2.9. 

It is to be taken into account that with the employment of rotary piston vacuum pumps, the temperature of the fluid fed to the liquid ring compressor is higher than with the other combinations. In addition, this heat is to be dissipated by the ring liquid, so that the temperature of the liquid ring will be higher and with it the suction capacity will be lower. 

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