How to choose a dry screw vacuum pump
Two intermeshing screw rotors turn without touching each other or the housing, carrying gas axially from inlet to exhaust. Nothing lubricates the pumping chamber, so the pump handles vapour, dust and aggressive chemistry that would destroy an oil-sealed pump. Modern variable-pitch rotors compress progressively, which lowers power draw and discharge temperature compared with constant-pitch designs.
Start with pumping speed at your working pressure and the ultimate you need, then work through the process: what condenses, what corrodes, what deposits. That drives coatings, purge arrangements, jacket cooling and exhaust temperature. Check the motor rating and whether a variable-speed drive is offered — screw pumps spend most of their life at base pressure, where speed control saves real money. Confirm the inlet/outlet flange sizes and the cooling water or air requirement.
Typical duties: chemical and pharmaceutical process vacuum, solvent recovery, drying and distillation, semiconductor and coating lines, and central vacuum systems. Paired with a Roots booster, a screw pump gives a clean, oil-free system from atmosphere down to the 10⁻² mbar decade.
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FAQ
Why choose a dry screw pump over an oil-sealed pump?
There is no oil in the pumping chamber, so nothing backstreams into the process and there is no oil to change or dispose of. That matters for semiconductor, pharmaceutical and food processes, and for anything where solvent would contaminate the oil. The trade-off is higher purchase cost and higher noise.
How is a dry screw pump cooled?
By water jacket, air, or a combination, depending on model and gas load. Compression heat has nowhere to go without oil, so cooling is not optional — an undersized cooling circuit is the usual reason a dry screw pump trips on temperature. Confirm the required water flow and inlet temperature before installation.
Can a dry screw pump handle powder or condensate?
Better than most dry pumps, because the screw geometry conveys solids toward the exhaust rather than trapping them, and many models allow a nitrogen purge. Heavy powder loads still need an inlet filter, and sticky condensate needs the body heated so it does not solidify inside the rotors.
What maintenance does a dry screw pump need?
Gearbox oil changes on schedule, shaft seal inspection, cooling circuit descaling, and cleaning of the pumping chamber when the process deposits solids. There is no pump oil in the chamber, but the gearbox and bearings still have lubricant with a service interval.
Do you supply screw pumps as a complete system with a Roots booster?
Yes. A screw pump backing a Roots booster is the standard arrangement where you need both a low ultimate pressure and high throughput at that pressure. We supply the skid with pump, booster, valves, instrumentation and control assembled and tested as one unit — send the process conditions for sizing.