Edwards HT20B (ANSI20/ISO630 inlet) diffusion pump is designed for all light and heavy duty industrial applications. The robust construction gives high pumping speed at high pressure.

Features and Benefits

  • Highest throughput of comparative sized pumps
  • Earliest crossover pressure of similar sized pumps
  • Excellent maximum backing line pressure and tolerance to gas surges
  • Comparative pumping speed to similar sized pumps
  • Integral cold cap for best performance and low backstreaming
  • Self fractionating for low ultimate pressures
Easy change heater assembly


  • Vacuum metallurgy
  • Distillation, drying and degassing
  • Thin film coating and metallizing
  • Large-scale research
Technical data  
Comparative pumping speed 18000 ls-1
ISO pumping speed†  
Nitrogen 8000 ls-1
Helium 16000 ls-1
Max throughput (nitrogen) 24 mbar ls-1
  18 Torr ls-1
Critical backing pressure (DC704EU) 1.3 mbar /1 Torr
Min backing pump displacement for max throughput 135 m3h-1
  80 ft3min-1
Recommended backing pump‡ GXS250, E2M175
Recommended fluid DC704
Fluid charge (dry) 3600 ml / 3.8 qt
Inlet/backing connection ANSI20/ANSI4 or ISO630/ISO160
Water connection 3/4 inch NPT female
Heater power 12.6 kW / 16.9 hp
Warm up time 60 min
Minimum cooling water flow at 25°C 960 l h-1 / 4.2 US gal min-1
Pressure drop across cooling water supply 1.2 bar / 17.4 psi
Weight 275 kg / 605 lbs

 † ISO speed and throughout data obtained with total pressure measurement. Partial pressure readings typically increase data by ~30%. ISO speed measurements are typically 10% less than AVS measurements for the same pump.
‡ These are given for guidance