Oil-Free Scroll Vacuum Pump for Freeze Dryers: Selection Guide
Why freeze drying needs a vapour-tolerant pump, how a dry scroll pump compares with an oil-sealed rotary vane pump, and which WAVE WDry model fits your dryer.
In this article
The short answer
An oil-free scroll vacuum pump compresses gas between two spiral-shaped scrolls without any oil in the pumping chamber. For freeze drying that means no oil changes, no oil mist at the exhaust and no risk of oil back-streaming towards the product. The WAVE WDry series covers 12.2 to 36 m³/h with an ultimate vacuum of 0.007–0.009 mbar; prices start at €3,200 net.
For most small and mid-size freeze dryers such as the WAVE FD260 and FD440, the WDry 36 is the usual choice: 36 m³/h, 0.009 mbar ultimate vacuum and 270 g/h water-vapour tolerance for €5,900 net.
What a freeze-drying pump must do
During primary drying the ice in the product sublimates and most of the vapour freezes out on the condenser. The vacuum pump removes the remaining gases and the vapour that the condenser does not catch, especially at the start of the cycle and after defrosting. A freeze-drying pump therefore has two jobs: reach a pressure well below the triple point of water and cope with water vapour without being damaged.
Suitable pump types reach 0.1 mbar or lower and tolerate vapour: oil-sealed rotary vane pumps with gas ballast, dry scroll pumps, dry screw pumps and Roots combinations. Diaphragm (membrane), water-ring and claw pumps are not suitable for freeze drying.
Scroll pump or oil-sealed pump?
| Dry scroll pump | Oil-sealed rotary vane pump | |
|---|---|---|
| Oil in the pumping chamber | None | Yes, oil seals and lubricates |
| Routine maintenance in freeze drying | Tip seals about every 2 years or 13,000 operating hours | Oil change every 100–200 operating hours |
| Exhaust | Oil-free | Oil mist, needs a filter |
| Water vapour | Specified vapour tolerance per model | Gas ballast needed; water contaminates the oil |
| Purchase price | Higher | Lower, especially refurbished |
Every WAVE freeze dryer ships as standard with a refurbished oil-sealed vacuum pump. An oil-free scroll pump is an optional upgrade. It costs more at purchase but removes the most frequent maintenance task in freeze drying: in a 24-hour cycle, an oil-sealed pump reaches its next oil change after a few batches.
WAVE WDry 10, 15 and 36
| Specification | WDry 10 | WDry 15 | WDry 36 |
|---|---|---|---|
| Net price | €3,200 | €3,900 | €5,900 |
| Displacement | 12.2 m³/h | 16.0 m³/h | 36.0 m³/h |
| Ultimate vacuum | 0.007 mbar | 0.007 mbar | 0.009 mbar |
| Water-vapour tolerance | 136 g/h | 268 g/h | 270 g/h |
| Motor power | 400 W | 400 W | 1,200 W |
| Inlet / outlet | KF25 / KF25 | KF25 / KF25 | KF40 / KF25 |
| Noise level | 53 dB(A) | 53 dB(A) | 56 dB(A) |
| Weight | 26 kg | 27 kg | 47 kg |
All three models run on 220–240 V at 50 or 60 Hz, are air-cooled, operate at 0–40 °C ambient and have a leak rate below 1 × 10−8 mbar·l/s. The pumps are suitable for freeze dryers of other brands as well as for other dry and wet vacuum processes.
Choosing the right size
Quick guide
- WDry 10: small laboratory freeze dryers and other small vacuum tasks.
- WDry 15: entry level for freeze drying and industrial applications with about twice the vapour tolerance of the WDry 10.
- WDry 36: the standard choice for small and mid-size production dryers such as the FD260 and FD440.
Chamber volume, the condenser and the product decide how much gas and vapour reach the pump. If you are unsure, send WAVE the model of your freeze dryer and your typical load; the team will confirm which pump fits. For larger machines, WAVE specifies the pump set in the quotation.
The WDry 36 has a KF40 inlet, the smaller models KF25. Check the flange on your dryer and plan an adapter if necessary.
Maintenance
The wear parts of a scroll pump are the tip seals in the spirals. On the WDry 36 they need replacing about every two years or 13,000 operating hours. Keep the cooling air path free, protect the pump from liquids and dust, and follow the defrost routine of your freeze dryer so that the condenser catches the vapour rather than the pump. The WDry 36 manual and specifications can be downloaded as a PDF.
Frequently asked questions
Can a scroll pump be used for freeze drying?
Yes. Dry scroll pumps reach the required vacuum and tolerate a defined amount of water vapour. The WAVE WDry 36 reaches 0.009 mbar and is specified for 270 g/h of water vapour.
How often does a scroll pump need maintenance?
On the WAVE WDry 36 the tip seals need replacing about every two years or 13,000 operating hours. There are no oil changes.
Which pump fits a WAVE FD260 or FD440?
The WDry 36 is the recommended oil-free pump for most smaller WAVE freeze dryers, including the FD260 and FD440.
How much does an oil-free scroll pump cost?
WAVE WDry pumps cost €3,200 (WDry 10), €3,900 (WDry 15) and €5,900 (WDry 36), net, excluding VAT and shipping.
Do the pumps work on 60 Hz?
Yes. All WDry models are specified for 220–240 V at 50 or 60 Hz.
Order a WDry scroll pump
Compare the three models, download the manual and order online — or ask WAVE which pump suits your freeze dryer.
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