Vacuum lobe-type

Figure 6-48A. Typical performance of high vacuum booster lobe-type high volume draw-down for evacuating vacuum systems before use of higher vacuum (lower absolute pressure) pump. By permission, Roots Division, Dresser Industries, Inc.

Q. There are other types of vacuum pumps, seldom found in cleaning machines. A fifth type of pump is a dry pump, which can be a screw, scroll (high speed), or claw design. Booster pumps are also dry and a generally rotary lobe type. 

Figure 5.7 Lobe type (Roots) vacuum pump.

The dry helical lobe rotary compressors nonlubricated cylinder types of compressors are used for injecting of the fuel in gas turbines at the high pressure needed. The gas turbine application requires that the compressor be dry. This standard is primarily intended for compressors that are in special purpose application and covers the minimum requirements for dry helical lobe rotary compressors used for vacuum, pressure, or both in petroleum, chemical, and gas industry services. This edition also includes a new inspector s checklist and new schematics for general purpose and typical oil systems. 

Screw-type rotary lobe blower, 390-391 Vacuum relief, 435... 

Vacuum pumps reciprocating piston type decrease the pressure to 1 Torr rotary piston down to 0.001 Torr, two-lobe rotary down to 0.0001 Torr steam jet ejectors, one stage down to 100 Torr, three stage down to 1 Torr, five stage down to... 

In the past, environmental problems associated with the commonly used pump fluids, namely water and oil, have led to the development of dry vacuum pumps that compress without contact. Rotary lobe and screw-type vacuum pumps (Fig. 5 and 6) are the types most commonly used for industrial applications. 

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