What preventative maintenance techniques should I use to detect and reduce the risk of motor failure?

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Answer by Hugh Falkner (Atkins)

Preventative maintenance is the monitoring, detection and correction of incipient faults before they become major problems, so reducing the cost of unexpected downtime.  The challenge for all organisations is to implement a programme that is effective without excessive cost, and so lower cost or easy to use techniques are of particular interest.

Even without any test equipment, operatives will often comment on increases in vibration, noise or heat from a motor, which is a clue that there is a serious problem developing.  But by the time a problem is this obvious, it is likely that it is so bad that any mitigating measure will be costly. Fortunately the cost of specialist equipment that can be used for assessing the condition of motors makes it feasible for even smaller sites to be able to undertake some critical measurements.

Two non contact methods are suggested for organisations new to preventative maintenance, the equipment which can be used in a wide variety of other applications too.

• Thermal Imaging cameras will show the heat distribution over the whole of the motor body, with hotspots on the housing indicating a possible winding fault, and high temperatures where the shaft exits the motor being indicative of a bearing fault.  Care needs to be taken in the interpretation of thermal images, but comparisons between motors undertaking very similar duties will clearly indicate problems.

• Vibration monitoring equipment can detect early stage bearing problems, also vibration from other driven equipment such as gearbox wear, eccentric loads.

In addition, simple electrical tests such as monitoring the line voltage and voltage imbalance will show if remedial action needs to be taken in order to reduce these sources of excessive motor loss.