Short answer: use a dry claw pump for CNC hold-down, conveying and packaging around 100 mbar; an oil-sealed rotary vane for clean, light duty to about 0.5 mbar; a liquid ring for wet, dirty or vapour-laden loads to about 33 mbar; a dry screw for clean deep vacuum around 1 mbar with solvents; and a rotary piston, alone or under a booster, for heavy deep vacuum such as transformer drying.
Side by side
| Technology | Ultimate vacuum | Oil or water in the gas path | Handles vapour and carryover | Typical uses | Sizes we sell |
|---|---|---|---|---|---|
| Dry claw | About 100 mbar (27 inHg) | None | Dry air only | CNC router hold-down, pneumatic conveying, packaging, central vacuum | 43 to 671 cfm, 2 to 30 hp |
| Rotary vane, oil sealed | About 0.5 mbar | Oil | Light vapour with gas ballast | Packaging, thermoforming, pick and place, lab | 7 to 460 cfm |
| Liquid ring | About 33 mbar with cool seal water | Water | Yes, very tolerant | Process vacuum, sterilizers, extrusion, solvent recovery | 75 to 950 acfm |
| Dry screw | About 0.01 mbar, full speed to 1 mbar | None | Yes, condensable vapours and solvents | Chemical, pharmaceutical, drying, transformer work | 71 to 441 cfm |
| Rotary piston | About 10 microns (0.013 mbar) | Oil | With gas ballast; robust on dirty duty | Transformer drying, vacuum furnaces, impregnation, degassing | 144 to 778 cfm |
| Booster system | Below 10 microns, fast pump-down below 50 torr | Oil in backing pump | As backing pump | Large vessels, transformer drying and oil filling | 540 to 2,000 cfm booster |
How to choose in four questions
- How deep? Rough vacuum (100 mbar and up) is claw or liquid ring territory. Below 1 mbar you need dry screw, rotary piston or a booster.
- Is anything wet or dirty coming in? Water, steam or solvent favour liquid ring or dry screw. Oil-sealed pumps need gas ballast and more oil changes.
- Can the process see oil? Food, pharmaceutical and clean processes favour dry claw or dry screw.
- How fast? Pump-down time sets the size: volume, target pressure and time go into the vacuum selector.
Common questions
Why not one pump for everything?
Each technology is efficient in one pressure band. A claw pump running at 1 mbar moves almost nothing; a rotary piston pump on a CNC table wastes power and oil. Matching the band cuts energy and maintenance.
What does acfm versus cfm mean on a vacuum pump?
Vacuum pumps are rated in actual volume at the inlet pressure. At lower pressure each cubic foot holds less gas, so capacity curves, not a single number, decide the size.
Can you supply the whole package?
Yes. Pumps can be packaged with separators, seal water recirculation, receivers, controls and the isolation transformer, with installation through licensed service partners.
Updated by PRP Reps, Mississauga. Questions about your own system? Send us the duty or call +1 647 717 6264, Monday to Friday, 7 to 5 Eastern.