Do not select from catalogue maxima alone
Many selection errors come from buying the largest pumping speed on the datasheet. Catalogue speed is measured at a specific pressure, while real processes often run close to ultimate pressure where actual speed falls sharply. Work pressure, piping losses and simultaneous stations all belong in the calculation.
A four-step method
- Define target vacuum and working pressure range
- Calculate total speed for all simultaneous stations with 1.2–1.5× margin
- Check the real speed curve at the working pressure
- Assess gas composition, temperature, moisture and dust
Booster and screw systems also need a correctly matched backing pump — oversizing the booster while undersizing the backing pump is a common mistake.
