Compressors, Drivers and Alignment Considerations

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?

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

by Bertrand Wascat | | January 9, 2020
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