Vacuum Pumps

Frequently asked questions

Rotary vane vs. diaphragm vs. scroll pump — which do I need?

Choose by vacuum depth and chemical exposure. Rotary vane pumps reach the deepest vacuum (millitorr range) for distillation but require oil changes. Oil-free diaphragm pumps resist corrosive solvent vapor and excel at filtration and rotovap duty at moderate vacuum. Dry scroll pumps split the difference: deeper than diaphragm, oil-free, quiet, low maintenance. Match the technology to your lowest required pressure and your solvents.

How deep a vacuum (ultimate pressure) do I actually need?

It depends on the process. Vacuum filtration and basic degassing need only a rough vacuum (tens to hundreds of torr). Rotary evaporation typically targets the low-tens of millibar. Short-path or wiped-film distillation needs deep vacuum, often below 1 torr down to the millitorr range. Buy a pump whose ultimate vacuum comfortably exceeds your deepest setpoint so it holds steady under gas load.

What CFM or pumping speed should I size for?

Pumping speed (free-air displacement) sets how fast you reach vacuum and how well you hold it against vapor load, not how deep you go. Larger chambers, freeze dryers, and big rotovaps need higher CFM/L-per-minute; a single small filter flask needs little. Undersizing leaves you waiting and unable to keep up with boil-off; oversizing wastes money and can pull product over. Match speed to chamber volume and inlet diameter.

Will a vacuum pump handle corrosive solvents and vapor?

Only if it is built for it. Oil-sealed rotary vane pumps absorb solvent into the oil, degrading it and the ultimate vacuum, so they need a cold trap and frequent oil changes (or a gas ballast). For ethanol, acetone, and acidic vapors, oil-free chemical-resistant diaphragm or scroll pumps with PTFE-wetted paths are the safer choice. Always add a cold trap to protect any pump from solvent carryover.