Rotary piston blowers

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

Combination ejector/liquid-ring systems and mechanical systems that use rotary blowers backed with other mechanical pump types are versatile and energy efficient. Thermal efficiencies of combination pumping systems are shown in Figure 23-12. Ejector/liquid-ring systems offer the highest reliability and are versatile for both wet and dry loads over a wide range. Rotary-blower/ rotary-piston systems are the most efficient and have been extensively applied. 

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,... 

Evacuation of the chamber is achieved by means of a series of pumps initially a rotary piston pump takes the pressure down from atmospheric to around 30 Torr, then a blower of the Rootes-type reduces it further to about 0.1 Torr lastly, an oil-diffusion pump brings the chamber down to the condition required for the evaporation cycle—in the region of 0.0002 Torr. 

Hydrogen freed in the electrolyzer is sucked off by a liquid-piston type rotary blower and led under slight overpressure of 10 to 15 mm water column through an iron manifold to tubular water coolers, in which the temperature will drop from some 70—75 °C to 25 °0. From the cooler, the gas passes either directly... 

Rotary blowers are built for air pressures varying from 6 oz. to 10 lb. or even 12 lb. per square inch. The best efficiencies of this type of blower, however are usually secured below 5 lb. pressure, but the simplicity of the machine gives it an advantage over compressors of the piston type and frequently warrants its installation for the higher pressures indicated when designed for this purpose- As the machine operates by displacement, it is usually preferred for cupola practice, and copper and lead blast furnaces, because its positive action will not permit 2 reduction in air supply if the cupola tends to clog. For other uses of air at pressures below 8 oz. the fan is ordinarily more economical. 

---