Lifetime & Major Maintenance Intervals of Plant and Equipment 4

[zinki]

Regarding electric motors,and equipent electrical : can we impose to supply only the Major Turnaround frequency is 5 years; therefore, the Equipment, Items and Systems shall be designed for continuous operation of 5 years (8760 hour per year) without any maintenance activities requiring an interruption of the service”.

 

[electricpete]

I think in general that is reasonable although obviously the motor design, application and environment play a role. Example - some motors in some environments may need to be taken out of service for more frequent cleaning.

There are also things that can emerge that will require a change in plan. An obvious event is winding failure, it makes the decision for you. Less obvious are rolling bearing defects that may announce themselves in vibration and noise with varying degrees of urgency.

 

[davidbeach]

You can design for that or you can worry about first cost. A 4.9hp load can be served by a 5hp motor but probably not for 43800 hours at a stretch. A 7.5hp motor might have a much greater chance of running that load that long.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Hoxton123]

It is a complex area. Motors with grease lubricated rolling element (ball / roller) bearings will require re greasing more often than 5 years, depending on motor speed, number of starts etc. Smaller motors may require repacking of the bearings if regreasing ports are not fitted.

See

https://www.machinerylubrication.com/Read/749/electric-motor-regreasing

Rolling element bearings have a statistical life.

Also, depending on the 'plant', there are many types of plant (oil refineries, sewage works, cement plants, power stations and so on). Some owners are willing to spend on competent initial design engineering and will be prepared to pay a premium for a plant designed for safe and practical maintenance.

Others will not...

So having realised that you do not know (in simple terms) how long the bearings will last, you fit two motors for every application. You may be introducing another problem as bearings can be damaged while stationary (search for false brinelling), so you operate the motors alternately, ensuring that both head for the statistical failure period at the same rate.

Get good plant operating and dowtime records with competent experienced staff and manage it.