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Technology, Oil-Injected Air Compressors

Splash and Pressure Lubrication Systems in Piston Compressors


Piston compressors have been around for centuries. They can be either oil-injected or oil-free, depending on the application and end use. In oil-injected models, the oil typically serves three crucial purposes: cooling, sealing and lubricating. But not all oil-injected piston compressors lubricate components the same way. There are two common systems for lubricating the pump in piston compressors: splash and pressure lubrication.

Splash Lubrication Systems

In splash lubrication systems, oil is applied to the cylinders and pistons by rotating dippers on the connecting-rod bearing caps. Each time they rotate, the dippers pass through an oil-filled trough. After running through the oil trough, the dippers splash oil onto the cylinders and pistons to lubricate them.

While splash lubrication is effective for smaller engines and pumps, it’s not a precise process. Parts of the pump may be insufficiently oiled or oiled too much. The amount of oil in the trough is vital for proper operation. If there is not enough oil, wear between critical components may occur, and too much oil will cause excessive lubrication, which can lead to hydraulic lock.

The type of oil used and its viscosity is also important in a splash lube system. The oil must be thick enough to provide sufficient lubrication and cling to the dippers, but not so viscous that it heats up as it is churned about in the oil trough. Oil purity is also critical; oil should be filtered regularly and replenished when necessary.

Pressure Lubrication Systems

Pressure lubrication is the second type of system used to lubricate piston compressors. It is a more technically advanced and usually more costly method, but it results in longer life for a compressor.

Pressure lubrication is a process where an oil pump precisely distributes oil to key areas of the pump. Typically, the oil is pumped through an oil filter and into the pump where it is then recycled and reused; using a replaceable oil filter can further improve the life of the oil. The oil is transported to the key area by use of an oil pump. Therefore, the viscosity of the oil is not as critical as with a splash tube system.

Either method has been used extensively in many various pump and engine applications, and both are suitable for piston compressor applications. When purchasing a new piston compressor, decide what’s important for you. If upfront cost is important, a splash lubricated compressor may be the way to go. But if you are willing to invest more in a pressure lubricated piston compressor, you’ll be rewarded with added longevity and reliability.

What kind of lubrication system does your piston compressor use? Let us know in the comments below, and visit us at www.atlascopco.com/air-usa to learn more!


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