Dry Scroll Pump Service, Tip Seals and Intervals
Servicing dry scroll pumps from Edwards, Leybold, Pfeiffer and Agilent. Wear signs, documented intervals, tip seal replacement and service kits.
Dry scroll pumps run without oil. Their typical wear part is the tip seal, a sealing strip in the scroll groove. This guide covers how to recognise wear, which intervals Edwards, Leybold, Pfeiffer Vacuum and Agilent (formerly Varian) state, and how a tip seal change works.
How tip seals wear
Tip seals close the gap between the fixed and the orbiting scroll. The process produces fine wear dust. According to Edwards (nXDS, A735-01-880), some of it collects in the exhaust duct and is blown out when the pump is vented. That is normal.
High exhaust pressure and operation outside the specified limits both reduce tip seal life, the nXDS manual says.
Signs of wear
No manufacturer gives a fixed ultimate pressure that triggers a change. Agilent says a change is due when the base pressure of the TriScroll has become unacceptable for the application. Edwards ties the decision on the nXDS to the performance reached. Pfeiffer recommends maintenance level 1 when the pumping capacity of the HiScroll is no longer sufficient.
Rule out other causes first. Edwards lists a system leak, unsuitable pressure measurement, dirty fittings, a blocked inlet strainer, a blocked exhaust line and process vapours.
| Symptom | Possible cause | Action according to the manual |
|---|---|---|
| Ultimate pressure creeps up over months, nothing else unusual | Worn tip seals (Edwards, Pfeiffer, Agilent) | Check for leaks, gauge, strainer and exhaust line, then fit a tip seal kit |
| Pressure too high after vapour use or storage | Moisture or condensate in the pump (Edwards, Pfeiffer, Leybold) | nXDS, run on gas ballast for at least an hour. XDS 5 and 10, one hour on setting II, then up to 24 hours on setting I |
| Leybold SC D does not reach ultimate pressure | Moisture or solvent condensed, damaged O-ring, clogged air flush port | Open the inlet to atmosphere briefly, then run about 24 hours with the inlet closed, fit a trap or filter |
| Pressure still poor after a fresh change | Tip seals not yet run in | Keep running without load (Pfeiffer), nXDS run-in 24 to 48 hours |
| Humming or grinding from the bearings | Worn bearings (Agilent, Pfeiffer, Edwards XDS) | Not a job for the tip seal kit, have bearings and shaft seals replaced |
| Service indicator flashes | Interval reached (Edwards nXDS and Pfeiffer HiScroll) | Check performance, reset the indicator after service |
Ultimate pressures from the manuals
These are manufacturer figures for a new pump in the stated manual edition. Use them for comparison, not as a replacement limit.
| Pump | Ultimate pressure in mbar | Source |
|---|---|---|
| nXDS6i | 0.02 without gas ballast, 0.05 at setting 1 | A735-01-880 issue B |
| nXDS10i and nXDS15i | 0.007 without gas ballast, 0.04 at setting 1 | A735-01-880 issue B |
| nXDS20i | 0.03 without gas ballast, 0.06 at setting 1 | A735-01-880 issue B |
| XDS 5 and XDS 10 | typically below 0.07 at 50 Hz, below 0.06 at 60 Hz, ballast closed | A726-01-880 issue M |
| SCROLLVAC SC 5 D | 0.05 or lower | GA01423_0102 |
| SCROLLVAC SC 15 D | 0.016 or lower | GA01423_0102 |
| SCROLLVAC SC 30 D | 0.01 or lower | GA01423_0102 |
| HiScroll 6 and 12 | tested base pressure 0.015 and 0.006 (stated in hPa) | Pfeiffer, HiScroll 6, 12, 18 |
| TriScroll 300 | 10 mTorr after 24 hours of running following service | Varian tip seal manual 699904280 |
The Varian manual recommends a capacitance or Pirani gauge for 5 to 20 mTorr at plus or minus 1 mTorr.
Service intervals
With solvents, aggressive vapours or continuous operation at the upper temperature end, the intervals get shorter. Edwards and Leybold both say so.
| Pump | Tip seals | Other items |
|---|---|---|
| Edwards nXDS i | No fixed change. The service indicator after 30 months calls for a performance check, change if performance is too low | Strainer and fan cover 12 months, bearings 60 months, controller 120 months |
| Edwards XDS 5 and 10 | Yearly or as required, together with the exhaust valve | Motor test at 15,000 hours, bearings at 35,000 hours |
| Leybold SCROLLVAC SC 5, 15, 30 D | Set at 16,000 hours or two years, at 8,000 hours or one year only if something goes wrong | The small interval covers shaft seals and exhaust valve, the large one adds bearings, spider and tip seals |
| Pfeiffer HiScroll | Level 1 as required, Pfeiffer cites about 2.5 years | Level 3 after 5 years or 40,000 hours by Pfeiffer Service |
| Agilent TriScroll 300 and 600 | No fixed value, change when base pressure is too high | With humming or grinding, replace bearings, shaft seals and O-rings |
At Leybold, whichever comes first counts, time or running hours. Manual GA01423_0102 asks that Leybold performs the service and users do not open the pump themselves. Pfeiffer allows level 1 to the user. Edwards has a separate nXDS tip seal manual and leaves bearing replacement to trained technicians.
Replacing tip seals, nXDS as an example
The steps come from Edwards manual A735-02-840 for the nXDS tip seal kit. They do not replace the manufacturer instructions. Edwards requires safety goggles, a positive pressure breathing mask if contamination is possible, and decontamination before maintenance.
- Run the pump on gas ballast for one hour to clear process gas. Then switch off, disconnect from the mains and let it cool.
- Undo the two screws of the fan cowl. Then undo the four screws of the fixed scroll and lift the scroll off at the levering slots. Disconnect the fan lead from the controller first.
- Remove the tip seals from both scrolls and the O-ring of the fixed scroll. Clean scrolls and grooves with a lint-free cloth and isopropanol.
- Press new tip seals into the groove from the scroll centre outward. Push firmly at the pinch points. Cut the seal at the groove end, leaving at least 20 mm clear of the groove end for expansion.
- Fit the new O-ring, moistened with water only. Reconnect the fan lead and set the assembly on with even pressure, watching the dowel. Tighten the four screws in small steps to 9 Nm, then turn the pump by hand with a 4 mm Allen key.
Check that the fan runs. The tip seal manual says bedding in takes a few hours, and the nXDS instruction manual gives 24 to 48 hours for full performance.
On the HiScroll, Pfeiffer presses the tip seals in from the inside and cuts them at the cut mark. Housing screws go on crosswise to 5 Nm, the fan cover to 3.5 Nm. For the TriScroll 300, the Varian manual (draft edition) asks for one to two hours of cooling and no compressed air into the bearings when removing wear dust.
Matching parts from the catalogue
Check fit against nameplate and part number before ordering.
- A735-01-801 is the nXDS tip seal kit by catalogue name.
- A735-01-803 is the exhaust and ballast valve kit for nXDS (standard and R). The manual advises fitting it together with bearing service.
- A73501802 is the nXDS bearing replacement kit. The manual leaves the work to trained staff.
- A72601805 and A726-01-824 are listed in the catalogue as tip seal kits for XDS 5 and 10.
- A730-01-801 is a tip seal and exhaust valve service kit in the catalogue. The name gives no series.
- 870000510 and 870000511 are tip seals for SCROLLVAC SC 5 D and SC 15 D. 870000496 is the minor maintenance kit for the SC 5 D after 8,000 hours, 870000499 the major kit after 16,000 hours.
- X3815-67000 is the tip seal kit for IDP 15. X3828-69500 is a TriScroll 620 exchange pump.
FAQ
Will a tip seal kit fix a noisy pump?
Not necessarily. Humming or grinding points to bearings, rotor or contaminated scrolls. Tip seals do not cure that, so have the pump checked by the manufacturer or a service shop.
How often should tip seals be replaced?
It depends on manufacturer and load. Documented are yearly or as required on the Edwards XDS, 16,000 hours or two years on the Leybold SC D and about 2.5 years at Pfeiffer. On the nXDS and TriScroll it follows performance.
May I service a scroll pump myself?
Pfeiffer allows the tip seal change (level 1) to the user, and Edwards describes it for the nXDS in a separate manual. Leybold requires service by Leybold for the SC D. Always follow the safety and decontamination rules of the manual.
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