Speed definitions

Q: Kindly tell me, what is the difference between rated speed, design speed and normal speed of a compressor? What is the significance of maximum continuous speed?

A: These terms are generally applied to centrifugal or axial compressors.

Rated speed: The highest rotational speed required to meet the specified operating conditions, sometimes called 100% speed.

Design speed: A speed value assigned by the manufacturer.

Normal speed: A speed that the user expects to operate most of the time.

Maximum continuous speed: The significance of the maximum continuous speed is the highest speed at which the compressor is built and tested. The compressor is capable of continuous operations at this speed. For variable speed compressors, this value is 105% of rated speed.