In our previous article we explained the difference between piston compressors and rotary screw compressors. However, there is also an important difference between oil-free and oil lubricated compressors. We’ll discuss both in this article.
A piston compressor - obviously - uses a piston to compress air and deliver it at high pressure. Essentially it works according to the same mechanism as a combustion engine. A central shaft drives the pistons. When the piston is drawn backwards, gas enters the compressor through a valve. The gas is then injected into the cylinders of the pistons and the movement of the pistons compresses the air. In piston compressors, some sort of lubrication is needed to ensure smooth operation and prevent overheating.
A rotary screw compressor, on the other hand, uses rotors to compress air. Male and female rotors turn in opposite directions, thus trapping the air between them. There is no valve system. Overheating is not an issue here, but the fact remains that rotary screw compressors can deliver a continuous airflow: they need lubrication to keep going at full throttle, 24/7.
What about the types of lubrication?
In oil-lubricated air compressors, oil is used to keep everything running smoothly and prevent overheating. This, however, has a few disadvantages:
Because of these reasons, oil-lubricated air compressors are often used in industrial settings.They also offer a few advantages:
Oil-free air compressors use other means of lubrication, for instance pre-lubricated cylinders and an intercooler. An oil-free air compressor does technically contain oil, but that won’t come into contact with the compressor. The oil-free air compressor has a few disadvantages:
Oil-free air compressors are especially suitable in non-industrial settings like dentistry or smaller workshops where contamination is an issue. They are also particularly useful for home or DIY-applications. The advantages of an oil-free compressor: