What You Need to Know About Rotary Screw Compressor Lubricants

Description: Rotary Screw Air CompressorsAn important part of rotary screw compressors is lubricant.  It is useful to know about different lubricant types as that knowledge ensures correct use and even helps to extend the life of the compressor.
What are the Types of Lubricants?

  • Mineral Oils – this type has been used for a long time.  Its use began to decrease when it began to cost money to dispose of oil.  A benefit of using mineral oil is that contaminants in the compressor are taken out with the oil.  A drawback of mineral oils is that they tend to oxidize quickly around higher temperatures and pressures which forms varnish and sludge.
  • Synthetic Hydrocarbons – a plus of this type of lubricant is that polyalphaolefin (PAO) base stock is usually used and the PAOs are chemically stable and therefore predictable.  PAOs, however, are not good solvents.  PAO lubricants may be considered the best lubricants for rolling element bearings used in these compressors.
  • Organic Esters – the two main types are dibasic acid (diesters) and polyol.  Diesters have the same consistency over a range of temperatures which makes them desirable and they are also good solvents which makes them customizable for the application.  A drawback is that they will dissolve paint and varnish.  Polyol esters are similar to diesters but remain stable at higher temperatures.    
  • Phosphate Esters – these have a very limited use.  They are not very tolerant of heat of moisture which means that they need changed very often.  A plus of these esters is that they can be made fire resistant.
  • Polyglycols – these were first created for natural gas compressors.  For use in air compressors these fluids serve as compromise fluids.  They do not form varnish so there is no visual sign that the lubricant has failed.
  • Silicones – this type is resistant to heat, oxidation, and vaporization.  High cost, leakage, and poor lubricating properties limit their correct use.
  • Semi-Synthetics (Blends) – the idea behind blends is to provide the benefits of a pure synthetic at a cost that is not as high. 

For all of your rotary screw compressor needs Air Center, Inc. will be able to help.  Air Center stocks many air compressor parts and filters for major manufacturers, designs and installs compressed air systems, and employs technicians who are able to service any compressed air equipment.