What is the difference between: standby, backup and redundant equipment?

In reliability engineering one way to get high plant and equipment reliability is to provide an extra unit that is available to immediately replace the duty unit when it fails. The configuration of the second unit can be as a standby, or as a redundancy, or as a backup.


Hello Mike,

What the different between standby, backup and redundancy? Since before your online RCM training course, all for me were only standby items.



Dear Wael,

‘Standby’ means a separate unit, that is not operating, is provided beside the working unit and is ready to start when the duty unit stops.

‘Redundancy’ means a second unit is operating in parallel with the primary duty unit and both are sharing the demand. Should the primary unit fail, the second unit takes the full service.

‘Backup’ means another unit from somewhere else is brought into operation should the duty unit fail. For example, you hire a mobile air compressor (the back-up) when your plant air compressor fails (or you start an air compressor in another part of the operation and use it to supply the air when the duty unit stops).


My best regards to you,

Mike Sondalini
Managing Director
Lifetime Reliability Solutions HQ


P.S. If you require advice on industrial asset management, industrial equipment maintenance strategy, defect elimination and failure prevention or plant and equipment maintenance and reliability, please feel free to contact me by email at info@lifetime-reliability.com

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