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Oil-Injected Air Compressors

Imagine you are driving your car on a hot day. Your dashboard indicates you are low on oil and need an oil change. Your engine is running hot. You change the oil, which gets filtered through your car engine and cools the vehicle down. The car runs smoother because the oil is lubricating the engine and making everything run more efficiently and reliably.

Now think of a rectangular air compressor device, about six feet high and five feet wide, inside a furniture manufacturing facility. Using oil to lubricate the air compressor motor within that facility will make the manufacturing process run efficiently and smoothly. The air, which gets hot when compressed, won’t overheat because the oil will keep it cool. The compressor will function well because the oil will keep the engine lubricated and running efficiently so the furniture-making process progresses accurately and efficiently while minimizing energy consumption and accelerates the manufacturing environment. 

This is an example of an oil-injected air compressor application! These machines are absolutely essential in powering a large variety of applications and industries - many of which wouldn't function without oil-injected compressors.

 

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What is an oil-injected air compressor?

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.

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How do oil-injected air compressors work?

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.
  • 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.
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Oil-Free vs. Oil-Injected Air Compressors

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.

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!

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Top Industries for Oil-Injected Air Compressors?

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:

Manufacturing:
  • 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.

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