A turbo molecular pump needs very little maintenance, but what it needs runs on a clock. Its rotor spins at high speed, and unless it floats on magnets, it rides on bearings that wear, fed by a lubricant that ages. The manufacturer sets the interval for each. Keep to it, and the pump stays available and lasts longer; Pfeiffer calls regular service essential to both availability and service life.
What wears out
A turbo pump with mechanical bearings runs its rotor on ball bearings, often ceramic, lubricated with oil or grease. At these speeds the bearings and their lubricant are the parts that wear. A pump on full magnetic bearings has no bearing contact at all, and Leybold counts those pumps as maintenance free.
What the makers recommend
Each maker sets the interval for its own pumps. Published examples:
Pfeiffer, hybrid-bearing turbo pumps. An inspection once a year, including a check of the operating fluid (Pfeiffer's term for the bearing lubricant) for discoloration. New operating fluid and new bearings every 4 years. Alternatively, a full service-center overhaul every 4 to 5 years; for the HiPace 80 Neo, 350 and 450, every 5 years.
Leybold, ceramic-bearing turbo pumps. A ceramic bearing exchange every 2 years, by its field service or by trained customers. On the TURBOVAC i, end users can replace the motor-side bearing with a kit, and the TURBOVAC 850 i to 1450 i warn when service is due.
Edwards nEXT55 and nEXT85. A new oil cartridge and bearings every 35,000 hours. Edwards encourages owners to do this themselves.
Pfeiffer notes that its intervals depend on operating and application conditions, so a pump on a hard process may be due sooner. Your pump's own manual has the figure that applies to it.
For bearing types and the signs of a failing bearing, see Bearings in Turbo Molecular Pumps.
Between services
- Keep a log of the pump's running hours. An interval only helps if you know where the pump stands.
- Once a year, look, listen and check the operating fluid for discoloration, as Pfeiffer's yearly inspection does.
- Leave the splinter guard in the inlet. Leybold says a turbo pump should only run with one.
- Do not knock or move a running pump. Leybold warns against sharp shocks and sudden changes of position.
- Vent a pump with a spinning rotor only as the operating instructions allow.
When not to wait
A pump that sounds different from last month, is years past its bearing service, or keeps tripping its controller is telling you something. Plan the service before it stops on its own. When a turbo pump fails, it is the pump, the controller or both, so look at the two together.