A turbomolecular pump is one of the more expensive components in a GCMS or high-vacuum setup, and it’s also one where “powers on” and “actually works” can be very different claims. Here’s what we check before listing any turbo pump, and what’s worth asking about if you’re buying one used.
1. Check bearing noise and spin-down time
A healthy turbo pump spins up smoothly and, once at speed, runs quietly with minimal vibration. On shutdown, it should coast down gradually over a predictable period rather than stopping abruptly or grinding as it slows. Rough bearing noise or an unusually short spin-down time are early signs of bearing wear, which is one of the more common failure points on these pumps.
2. Verify the controller communicates properly
Most turbo pumps run through a separate controller unit, and the pump and controller need to be tested as a pair — a good pump paired with a faulty controller will still show fault codes or fail to reach target speed. Confirm the controller reports normal status, actual rotational speed, and no active error codes, not just that the display lights up.
3. Check oil or grease condition on non-magnetic bearing designs
Pumps that use oil-lubricated or grease-lubricated bearings (as opposed to fully magnetically levitated designs) should show clean lubricant with no discoloration or metal particulate. Cloudy or dark lubricant usually means the pump is due for service, which is a cost worth factoring into any purchase decision.
4. Ask for a pump-down curve, not just “it powers on”
The real test of a turbo pump is whether it can actually reach and hold its rated vacuum level. A pump-down curve — time versus pressure, from atmosphere down to base pressure — tells you far more than a seller simply confirming the unit runs. If a seller can’t provide this, ask what vacuum level they achieved during testing and how it was measured.
5. Confirm mounting flange and voltage match your system
Turbo pumps aren’t universal — flange size (CF, ISO-K, ISO-KF), backing pump requirements, and controller voltage all need to match your existing system. This sounds obvious, but it’s the single most common reason a “great deal” on a used pump turns into an unusable purchase.
What “tested” means for the pumps we sell
Every turbomolecular pump we list has been run through this full sequence, including an actual pump-down test rather than a simple power-on check — see our verification protocol for the details. Browse our current tested vacuum pumps.