Compressor Lubricants and Friction

Why is lubricant so important for your air compressor and how do you know exactly what you need?

Lubrication has four main functions in compressor and vacuum systems.

  • To reduce friction and wear
  • To cool
  • To seal
  • To protect from rust and corrosion

Let’s look at Friction, the reason why you need a good lubricant:

  • One of the primary purposes of lubrication is to reduce wear and friction. Friction is defined as resistance to movement.
  • This resistance to movement occurs when two surfaces make contact either by force or by movement (usually both)

The amount of friction developed is dependent on:

  • The force of the contact
  • Velocity
  • Roughness of the two surfaces

No matter how smooth a surface is, if we go to the microscopic level, the surface will have a certain degree of roughness. When we take two surfaces that are rough at the microscopic level and slide them against each other you get friction as the rough surfaces “grab” each other.

One of the primary purposes of lubrication is to reduce friction and wear by overcoming the roughness between the two surfaces. This is accomplished by minimizing the surface to surface contact.

During proper lubrication an “oil wedge” is formed between the bearing and shaft surfaces as the shaft rotates. The oil wedge allows the shaft to float on a film of oil, thus preventing surface to surface contact.

To visualize this, imagine a boat that needs to be moved over some large boulders. The boat can be dragged over the boulders but damage will occur to the boat and with repeated boats passing, the boulders will be slowly ground down too. Simply by covering the boulders with water so the boat floats over them we reduced the friction between the boat and boulders. The boat floats over the boulders. This is what happens with our oil wedge. It floats the shaft over the bearing surface on a wedge of oil.

It is up to the scientists to develop the optimal viscosity and chemical makeup of oils to give the best combination of economy and lubrication for a specific application and environment. At Northwest Compressor we will happily advise you on the best type of lubricant for your specific compressor or vacuum application to ensure years of life from your equipment.

Air compressor service by Northwest Compressor in Corvallis, Oregon.

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