Start with Your Application Requirements

Before comparing pump models, define what your application actually needs. Buying a scroll pump based on price or brand name alone — without mapping specifications to process requirements — is one of the most common and costly mistakes. Answer these questions first:

  • What ultimate vacuum (base pressure) does the process require?
  • What volume must be evacuated, and how fast (required pump-down time)?
  • What gases will the pump handle — clean dry air, moisture-laden air, reactive or corrosive gases?
  • Is contamination-free (oil-free) operation mandatory?
  • What are the duty cycle requirements — continuous, intermittent, cyclic?
  • What are the installation constraints — footprint, noise level, power supply, exhaust routing?

Key Specifications to Evaluate

Pumping Speed (Volume Flow Rate)

Pumping speed, measured in liters per minute (L/min), cubic feet per minute (CFM), or m³/h, describes how quickly the pump displaces gas volume. Critically, pumping speed varies with inlet pressure — always review the pump's speed curve, not just the peak figure. A pump rated at 30 CFM at atmosphere may deliver significantly less at your target operating pressure.

Ultimate Vacuum (Base Pressure)

This is the lowest pressure the pump can achieve under ideal conditions with no gas load. It's specified in Torr, mbar, or Pa. Common single-stage dry scroll pumps achieve ultimate vacuums in the range of 10–100 mTorr. If your process requires pressures below this, you may need a multi-stage scroll pump or a scroll pump combined with a turbomolecular pump.

Inlet Flange Size and Compatibility

Match the pump's inlet flange to your existing vacuum system. Common standards include ISO-KF (NW), ISO-K, and CF flanges. Adapters are available but add complexity and potential leak points.

Gas Compatibility

Standard scroll pumps are designed for clean, dry, non-corrosive gas. If your process involves:

  • Moisture or condensable vapors: Look for pumps with a gas ballast feature or heated pump bodies.
  • Corrosive gases (HF, Cl₂, etc.): Require special tip seal materials (e.g., Viton, Kalrez) and corrosion-resistant scroll coatings.
  • Oxygen-enriched atmospheres: Demand oxygen-compatible lubricants in any oil-wetted components.
  • Explosive gases: ATEX/IECEx-rated pumps with appropriate motor and electrical certifications.

Power Requirements

Confirm the pump's motor voltage and phase requirements match your facility supply (e.g., 115V/60Hz single-phase, 208–230V/60Hz three-phase). Also check the motor's starting current requirements to size circuit breakers and wiring correctly.

Total Cost of Ownership vs. Purchase Price

The sticker price of a scroll pump is rarely the most important financial metric. Consider:

  • Tip seal replacement cost and interval: A pump with a lower purchase price but expensive, frequent tip seal kits may cost more over five years.
  • Energy consumption: Continuous-duty pumps running 8,760 hours per year make motor efficiency a significant operating cost.
  • Downtime cost: Pumps supporting critical processes have high downtime costs; factor in spare parts availability and service network responsiveness.
  • Warranty and support: Multi-year warranties and local service availability add real value.

New vs. Refurbished Scroll Pumps

Reputable refurbished scroll pumps from qualified service centers can offer significant savings — sometimes 40–60% of new pump pricing — with acceptable reliability for non-critical applications. Key questions to ask:

  • Were the scroll wraps inspected and tip seals replaced?
  • Were bearings replaced or only inspected?
  • Is a performance test certificate provided showing achieved ultimate vacuum?
  • What warranty does the refurbisher offer?

Questions to Ask Your Supplier

  1. What is the pump's performance curve across the full pressure range?
  2. What is the recommended tip seal replacement interval for my application?
  3. Are tip seal kits and wear parts available off-the-shelf?
  4. What is the lead time for replacement scrolls if wraps become damaged?
  5. Does the pump include onboard diagnostics or hours counters?

Summary

Choosing the right scroll pump comes down to matching specifications to your actual process needs, evaluating total cost of ownership over the pump's service life, and ensuring your supplier can support you with parts and service. A thoughtful selection process upfront saves significant time and money over the pump's operational lifetime.