Oil-Injected Air Compressors

In more technical terms, oil-injected air compressors (also known as oil-flooded or oil-lubricated compressors), are compressors that use oil to lubricate the air compression chamber, lubricate parts, and seal in the air. In this device, a liquid is injected into the compression chamber and often into the compressor bearings. Its function is to cool and lubricate the compressor element's moving parts and the air being compressed internally. The compressor also reduces return leakage to the inlet. Oil is the most commonly injected liquid due to its effective lubricating and sealing properties. If the oil gets too hot, the substance gets funneled to a cooler within the compressor.

Oil injected rotary screw compressors follow this same principle but apply it within a rotary mechanism, where two interlocking screws compress air continuously. This design allows for smoother airflow, reduced pulsation, and higher efficiency compared to intermittent compression systems. 

Air compression involves two steps. As air gets compressed its volume declines; then the pressure rises.

Two of the most common oil-injected air compressors are:

• Oil-injected rotary screw compressor: This type of compressor injects a liquid into the compression chamber to cool and lubricate the compressor’s moving parts, cool the air being compressed in the chamber, and help minimize leaks from returns into the chamber during discharge. While oil is the most common liquid used today because of its lubricating and sealing properties, water and other polymers are sometimes used. The oil then separates and passes through a filter and cooler before it cycles back into the process again. The compressed air can still be hot and often travels through a cooler, depending on end usage.
  
  In industrial applications, oil injected rotary screw compressors operate continuously, making them suitable for facilities that require steady air supply over long production cycles. Their design minimizes wear and supports consistent pressure, even under variable demand conditions. 
• Oil-injected piston compressor: In a piston compressor, as the piston moves downward, it creates a vacuum and draws air into the cylinder through the inlet valve. As the piston moves back up, it pressurizes the air. The compressed air is then forced through the hole in the outlet valve seat and delivered to the tank. In the oil-injected piston, the compression chamber is lubricated with oil, either through splash lubrication or pressure lubrication. These are also called oil-injected reciprocating compressors.
  
  Compared to piston systems, oil injected rotary screw compressors are typically used in larger industrial setups where airflow demand is continuous rather than intermittent. 

Air purity is critical for many applications where even the tiniest drop of oil, or air contaminated with oil can cause product spoilage, product recall or damage production equipment. Your specific application will determine which type of air compressor is best for you to use in your facility.

In instances where the threat & consequences of oil contamination are too high, like medical procedures, having an oil-free air compressor is a must. In applications where the consequences of oil contamination are not as great, such as general manufacturing & in industrial and small workshops, oil-injected air compressors are used.

For many industrial users, oil injected rotary screw compressors offer a practical balance between performance, efficiency, and durability, especially when air purity requirements do not demand oil-free standards. 

Key takeaway: Oil-free air compressors are not necessarily “better” than oil-lubricated compressors. The compressor you choose depends on your specific application requirements and the air quality that you need to achieve!

For some industries, such as food and beverage, oil-injected air compressors are not ideal. The oil presents too high a risk of contamination. For many other industries, air compressors that use oil are better suited. They are generally those that are not as susceptible and sensitive to contaminated air. Following are several examples:

• General manufacturing – Clamping, stamping, tool powering and cleaning, controls and actuators
• Furniture manufacturing – Air piston powering, tool powering, clamping, spraying, controls and actuators
• Plastics, silicone and rubber manufacturing – Mold press powering, tool powering, clamping, and forming, injection molding
• Metal Fabrication – Assembly station powering, controls and actuators, injection molding, tool powering, and spraying
• Glass, Stone, Clay – Conveying, blending, mixing, controls and actuators, glass blowing and molding, cooling
• Automotive: delivering air that powers tools and operations along the production line, from car to engine assembly & more.

What are oil injected rotary screw compressors used for? 

Oil injected rotary screw compressors are used in industrial applications that require continuous compressed air, such as manufacturing lines, automotive assembly, and material processing operations.

Why are oil injected rotary screw compressors preferred in industrial settings? 

They provide continuous airflow, stable pressure, and efficient operation over long duty cycles, making them suitable for demanding industrial environments.

Do oil injected rotary screw compressors require regular maintenance? 

Yes. Regular oil changes, filtration checks, and system monitoring are required to maintain performance, reduce wear, and ensure reliable operation. 

How do oil injected rotary screw compressors improve efficiency? 

They reduce internal leakage, maintain optimal operating temperatures, and support consistent compression, which helps improve overall system efficiency.