Pumps Rootes blower

Pumping system of the BAK 1200 consisting of rotary vane pump. Roots blower and refrigerator cryopump. 

Three-phase AC induction motors were used in the power equipment (pump. Roots blower. 

Roots pumps (Roots blowers) which maybe used as a dry compressing backing pumps alone, also for pump combinations with all kinds of backing pumps ... 

Pump package (vacuum technology) A combination of pumps designed to work together in sequence. Examples Diffusion pump, roots blower, oil-sealed mechanical vane pump turbopump, molecular-drag pump, diaphragm pump. Also called a pumping stack. 

QMS) and an ellipsometer complete the setup. The typical pressure is in the range of 0.15-0.5 mbar. The deposition chamber has a volume of 180 1. During processing it is pumped by a stack of two Roots blowers and one forepump (total pumping capacity is about 1500 m /h) otherwise it is pumped by a turbo pump (4501/s), with which a base pressure of 10 mbar is reached. 

As shown in Figure 2.25, it is more efficient to use a backing pump combined with one or two roots blowers (Fig. 2.27). The backing pump requires only 40 m3/h capacity, combined with a roots pump of 200 m3/h. This system evacuates the 1000 L also in 8 min down to 0.01 mbar, but below 0.1 mbar the system has a capacity of 200 m3/h or 2.2 10 3 g/s at 0.05 mbar. Such a pumping system is preferable for freeze drying compared with a large two-stage pump alone. 

The system operates at about 400 mTorr and with flow rates of about 1 slm, so a roots blower is used to pump the system to base pressure ( 1 mTorr) and then handle the gas flow at these low pressures. 

The ultimate pressure of a Roots blower/backing pump combination is approximately that of the backing pump divided by the compression ratio (k0) for the Roots pump at this pressure. In practice, however, the calculated value should be multiplied by a factor of 4 to 5 to take into account performance deficiencies of the backing pump. 

Dry Vacuum Pumps (DVPs) These use the operating principles of rotary-lobe roots blowers, claw compressors or screw compressors, and hence require electrical power. They run dry and hence at very high temperature due to the heat of compression. Usually,... 

Vacuum pump set, one roots blower, two oil-free pumps in series, end pressure < 1 x 10 mbar, evacuation time of loaded plant down to 0.08 mbar 12 min. Pressure control during MD either by injection of dry N2 or by closing and opening the valve between condenser and pump set ... 

Figure 14.13 Vacuum pump system containing three vane pumps and one roots blower.

After having reached the operating pressure it is therefore recommended to limit the vacuum pumping speed using a throttle valve, controlled gas ballast and/or in case of rotating pumps like roots blowers a frequency controller. 

Blower (vacuum technology) A low compression mechanical, compression-type vacuum pump. Example Roots blower. 

Booster pump (vacuum technology) A pump used between the high vacuum pump (particularly the diffusion pump) and the backing pump in order to increase the throughput in the medium vacuum range and decrease the volumetric flow through the backing pump. Example Diffusion pump (DP) exhausts into a Roots blower (booster pump) then into an oil-sealed mechanical pump. See also Vacuum pump. 

Roots blower (vacuum technology) A compression-type mechanical pump that uses lobeshaped interlocking rotors to capture and compress the gas. The roots pump uses tight mechanical tolerances for sealing (no oil) and so is sometimes classed as a dry pump. See also Vacuum pump. 

The booster (blower or Roots) pumps are high-throughput pumps with a low compression ratio. A booster pump is schematically shown in Fig. 1.8. The gap between the two counter-rotating rotors is of the order of 0.1 mm. The rotation (about 50rps) of the rotors,... 

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. 

Figure 7.19. Some rotary positive displacement compressors (a) A two-lobe blower, (b) Performance of a two-lobe blower Roots-Connersville Co.), (c) A screw pump with one power and two idle rotors (Kristal and Annett, 1940). (d) Performance ot 3 5 screw pump handling oils at 1150 rpm against 325 psig Kristal mi Annett, 1940). (e) Rinciple of Ihe liquid ring seM compressor (Nash Et meemg Co.), (f) A shding vane Mower (Beach-Russ Co.).

Another pumping system may consist of a turbo-molecular pump, a Root s blower and a twin-stage rotary vane backing pump. 

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