Categories: Shaft Alignment,Machinery Maintenance,Other Topics

Compressors, Drivers and Alignment Considerations

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By on January 9, 2020

The two main types of compressors are dynamic and positive displacement.

The positive displacement compressor is probably the one you’re most familiar with.  It traps gas in a volume and then decreases that volume.  The decrease in volume causes a rise in pressure.

A dynamic compressor uses a rotating element (usually called an impeller) which increases the velocity of a gas stream and that is converted to pressure by then slowing it through a diffuser. When the same amount of air molecules that were spaced out are now jammed closer together – that’s pressure.


Three types of compressor drivers are typically available: gas or diesel engines, mechanical drive gas turbines and electric motors. A fourth choice is a steam turbine, which is used extensively in hydrocarbon processing plants and other industries that have ample supplies of steam.


When performing a precision shaft alignment on a compressor, consider the type compressor and driver. What types of bearings are in these units? Is there dynamic movement due to thermal growth or process? Are there thermal targets provided by the manufacturer? If not, how can those be determined?

VibrAlign has the tools to determine accurate correction values (targets) to compensate for dynamic movement. If you need help or have questions contact us!


About the Author

Mac was a Journeyman Millwright at a Kimberly-Clark paper mill in Washington State before moving into a Maintenance Team Leader position. Later, he moved to Kentucky where he went to work for Wausau Paper as Maintenance Team Leader on a new mill start-up. This is where Mac was first introduced to VibrAlign. “I was so impressed with the people, passion, and products of VibrAlign. I had always hoped to one day give back some of the knowledge I have been fortunate enough to gain from others in my field. VibrAlign has given me that opportunity.”

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