Pumps are an essential component of laboratories and choosing a new pump to purchase when retiring an old one can be tricky. Here we want to highlight a couple points of differences between dry (diaphragm/scroll) and oil pump.

  

  Dry Pump / diaphragm / scroll (1 Torr) Oil pump / rotary vane pump (10^-3 Torr)

Best for
  • Aspiration of waste liquids (microbio), filtration, drying, evaporation, desiccator, and concentration.
  • Glove box, freeze dryers, schlenk lines, and molecular distillation.

Complications
  • Not deep enough
  • May evaporate the filtrate instead of collecting it, risking contamination.
  • Prone to bumping and foaming, risking sample loss.

Upfront Price
  • $2-5,000, varies
  • Varies, but generally cheaper than dry pump of the same function.

Operational Cost (cost of replacement, service, waste disposal, and labor.)
  • Possible replacement of diaphragm due to wear (annual change or less).
  • Cold trap (dry ice, liquid nitrogen) - to protect oil from degradation.
  • Oil mist filters - prevents vapors from escaping into lab air and coating surfaces.
  • Oil change - a few times a year.

Service Intervals
  • 10-15,000 hours.
  • If the usage is 20h/wk for 50wk/yr, servicing will be required every couple years.
  • 10,000 hours - oil change.

Misc.
  • Loud
  • Low noise level (75-80 dBA)

 

In sum, knowing what the experiments need would help with the most suitable purchase for the lab with the potential of eliminating cold traps and frequent services.

 

Citation

[1] Economic Advantage of Oil-free Vacuum for Labs

[2] What is the difference between Rotary Vane and Diaphragm vacuum pumps?