All you need to know about oil-injected air compressors

Suppose you are driving your car on a chilly winter night and it breaks down in the middle of the road. Now, one of the many probable reasons that come into your mind is that your car needs an oil change. 

The car uses oil to keep its engine lubricated for smooth functioning. Similar is the case with oil-injected air compressors that use oil as a lubricant because of its viscosity. 

The oil injected in the air compressors also acts as a cooling agent to help cool down the compressed air. This enables oil-injected air compressors to work as reliable workhorses, delivering you the desired amount of compressed air without any disruptions.

ISO air quality standards -  To ensure the compressed air quality of oil-injected air compressors, the International Organization for Standardization (ISO) has put forward the ISO 8573-1:2010 standard that needs to be followed by every company. The reason being that the compressed air might be contaminated with oil vapors or particles that would not be suitable for your industrial processes. The ISO has formulated six different classes for air purity according to the number of particles per cubic meter as a function of particle size. The compressed air quality ranges from ISO Class 0-5 where Class 0 being 100% oil-free air and ISO Class 1 being technically oil-free air. The oil-free compressors need to comply with the ISO Class 0 standard whereas the ISO Class 1 is the best possible standard that can be achieved by an oil-injected air compressor. The ISO Class 1 specifies an oil concentration of 0.01 mg/m3 at 1 bar 14.5psia and 20°C.

    a.    Oil-injected rotary screw compressor - An oil-injected rotary screw compressor is generally used in those facilities, which    require a constant supply of highly pressurized compressed air. In an oil-injected rotary screw compressor, oil is inserted in the compression chamber to lubricate and cool down the compressed air. It also helps in reducing any leakages of compressed air from the valves of the chamber. The cooled air then passes through several oil filters to minimize the oil carryover in both liquid and vapor form in the compressed air and to make it ISO Class 1 compliant. The oil is then cooled within the compressor  before it is again circulated back in the compressor chamber.

    b.  Oil-injected piston compressor - Also known as a reciprocating compressor, a piston compressor is a positive-displacement compressor that uses its piston to compress air. When the piston moves downwards, air enters the compression chamber because of the vacuum created. As the piston moves upwards, the compressed air is pushed outside of the compression chamber with the help of outlet valves. The compression chamber of an oil-injected piston compressor is lubricated with oil using pressure lubrication or splash lubrication. This oil helps in cooling down the compressed air along with a reduction in friction generated due to the movement of the piston.