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Hi everybody, today I will introduce the Screw Vacuum Pumps and Dry Screw Pumps Explained
- Design : Basically as shown in the figure below
- Operating principle : Two parallel intermeshing, bearing supported screw rotors (3, as shown in the figure below) that have opposite threads contactlessly and synchronously counter-rotate within a cylindrical housing (2, as shown in the figure below) which encloses them tightly, and forms a multi-stage pump.
The two rotor's counter-mesh design seals in the volumes at each thread and advances them along the rotors leading to the outlet (4, as shown in the figure below). The pump does not have valves in either outlet or inlet (1, as shown in the figure below). When a volume of displacement reaches the opening, pressure is then equalized in relation to the atmosphere. This, in turn proves that atmospheric air goes into displacement volume, then discharged once more at the turn of the rotor. The pulsing gas flow provides an immense level of dissipated energy, which heats the pump. Internal compression can help in minimizing dissipated energy. This can be done by reducing pitch of the thread to the outlet's direction. The gaps in between the rotors and housing, and the gaps between rotors relative to each other determines the screw pump's ultimate achievable pressure. The resulting configuration and the gap's geometry in relation with the mesh in the middle of the rotors also influence ultimate pressure significantly.
For the reason that the dissipated energy that comes from the pulsing gas heats up the pump's outlet side, cooling is needed at this exact location. The gap between rotors and the housing is a temperature differential function between the cooled housing and the warmer motors. The temperature and the amount of heat produced are the inlet pressure range's function. Temperatures are found to be lowest (nearly atmospheric) in high inlet pressures, as there is virtually no compression work done at this point and sufficient heat is removed out of the pump by the moving air. Plus, oscillation of gas in the last stages are prevented by the high gas flow. When operating at ultimate pressure, in which (p < 1 mbar), the atmospheric air oscillates and produces a much higher temperature in the outlet area, because no has passes through the pump, and no heat is being transferred out of the pump.
Dry screw pumps are screw vacuum pumps that are equipped with internal compression. Each of these screw rotors have a completely symmetrical geometry, coupled with a variable pitch. These pumps don't have end plates that are attached to control openings; rather, the pulsing gas is axially discharged against atmospheric pressure. The resulting volume of the pulsing gas is lower due to the internal compression.
- Application notes:
- Design : Basically as shown in the figure below
The two rotor's counter-mesh design seals in the volumes at each thread and advances them along the rotors leading to the outlet (4, as shown in the figure below). The pump does not have valves in either outlet or inlet (1, as shown in the figure below). When a volume of displacement reaches the opening, pressure is then equalized in relation to the atmosphere. This, in turn proves that atmospheric air goes into displacement volume, then discharged once more at the turn of the rotor. The pulsing gas flow provides an immense level of dissipated energy, which heats the pump. Internal compression can help in minimizing dissipated energy. This can be done by reducing pitch of the thread to the outlet's direction. The gaps in between the rotors and housing, and the gaps between rotors relative to each other determines the screw pump's ultimate achievable pressure. The resulting configuration and the gap's geometry in relation with the mesh in the middle of the rotors also influence ultimate pressure significantly.
For the reason that the dissipated energy that comes from the pulsing gas heats up the pump's outlet side, cooling is needed at this exact location. The gap between rotors and the housing is a temperature differential function between the cooled housing and the warmer motors. The temperature and the amount of heat produced are the inlet pressure range's function. Temperatures are found to be lowest (nearly atmospheric) in high inlet pressures, as there is virtually no compression work done at this point and sufficient heat is removed out of the pump by the moving air. Plus, oscillation of gas in the last stages are prevented by the high gas flow. When operating at ultimate pressure, in which (p < 1 mbar), the atmospheric air oscillates and produces a much higher temperature in the outlet area, because no has passes through the pump, and no heat is being transferred out of the pump.
Dry screw pumps are screw vacuum pumps that are equipped with internal compression. Each of these screw rotors have a completely symmetrical geometry, coupled with a variable pitch. These pumps don't have end plates that are attached to control openings; rather, the pulsing gas is axially discharged against atmospheric pressure. The resulting volume of the pulsing gas is lower due to the internal compression.
- Application notes:
In recent years, screw pumps have been replacing
oil-lubricated rotary vane pumps in the high pumping speed segment (100 – 600 m3/ h)
Their advantages include:
- No contamination of the medium to be pumped
- No lubricant in the gas displacement area
- Higher efficiency thanks to internal compression
- High-quality axial face seals
- Low noise level thanks to standard-feature silencers and outlet valve
- Low energy consumption
- Lower ultimate pressure PB < 10-1 mbar
- Virtually constant pumping speed between 1 and 1,000 mbar
- Good liquid and particulate matter tolerance
- Bearings and seals are protected through low gas pulsation as a result of internal compression
- Temperature-regulated cooling
- Extensive use of standard components
- Mounted ready for connection on a frame with vibration dampers
- Ideal backing pump for Roots pumps
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