The EH mechanical booster pump, based on the simple Roots principle, remains the favourite pump for applications where high pumping speeds are required for pressures in the region of 0.01 to 10 mbar. This pump must always be backed by another pump, which can deliver against a high-pressure differential to atmospheric pressure.

The EH250FX pump is supplied for use with PFPE oil. This enables them to be used in harsh (corrosive) processes, or where the presence of Oxygen will result in rapid degradation of hydrocarbon oils. Fomblin® must be purchased separately for PFPE prepared pumps.

Edwards recommends that the EH250FX pump should NOT run continuously on pressures >10 mbar.

Features and Benefits

  • Suitable for applications where high pumping speeds over 3000 m3h-1/1776 ft3min-1 are required in the pressure region of 0.01 to 50 mbar/0.0075 to 37.5 Torr.
  • Operating at relatively low pressures makes it highly reliable.
  • The EH pumps have a high quality, oil-free pumping mechanism. This offers:
    • Quiet, vibration free operation.
    • ­Rugged and corrosion resistant.
    • ­Advanced shaft-seal technology with no oil contamination of the process chamber
  • The corrosion resistant pumping mechanism is manufactured from high grade cast iron.
  • The proven shaft-seal arrangement ensures that no oil enters the pumping stator, and the absence of internal and external by-pass lines and valves which may corrode or stick minimizes maintenance requirements.
  • The design of the shaft seals is optimized to ensure that no lubricants can migrate into the pumping mechanism. This maintains booster pump performance in applications which demand the highest standard of cleanliness. In addition, this prevents the build-up of trapped particles on the rotor lobes and end-faces which have very close tolerances.
  • The dynamically balanced rotors and precision ground gears contribute to the smooth, quiet operation of the pumps, as demanded by manufacturers of advanced technology equipment.


  • Semiconductor processing
  • Vacuum distillation
  • Vacuum packaging
  • Steel de-gassing
  • Thin film coating
  • Vacuum metallurgy
  • Low density wind tunnels
  • Space simulation
  • Vacuum impregnation
  • Oil drying and de-gassing
  • Pharmaceutical freeze drying
  • CO2 lasers
Technical data  
Displacement (swept volume)  
 50Hz 310 m3h-1 / 185 ft3min-1
 60Hz 375 m3h-1 / 220 ft3min-1
Effective pumping speed with backing pump  
 E2M40 240 m3h-1 / 141 ft3min-1
 E2M80 274 m3h-1 / 161 ft3min-1
Pressure differential across pump  
 50Hz 0-180 mbar / 0-140 Torr
 60Hz 0-150 mbar / 0-115 Torr
Inlet connection ISO63
Outlet connection ISO40
Rotational speed  
  50Hz 0-2900 rpm
  60Hz 0-3500 rpm
Operating continuous inlet pressure 0-1000 mbar / 0-760 Torr
Maximum outlet pressure 1000 mbar / 760 Torr
Recommended backing pumps GV80, E2M40, E2M80, ES100, 212J
Motor power  
 Hydrocarbon 2.2 kW / 3 hp
 PFPE 2.2 kW / 3 hp
 ATEX 2.2 kW
 Explosion proof 3 hp
Ambient temperature range  
 Operating 5 to 40°C / 40 to 104°F
 Storage -10 to 80°C / 14 to 176°F
Maximum operating humidity 90% RH
Recommended oil Ultragrade 20
Oil capacity  
 Coupling cover 1.5 litre
 Shaft seal reservoir 0.125 litre
Weight 75 kg