According to data from IPIECA, electric motors account for more than 80% of electricity use at oil refineries, with 60% driving pumps, 15% powering air compressors and 9% running fans. With the oil industry very much reliant on the successful operation of electric motors, preventing their failure becomes an important priority.
Yet despite our best preventative efforts, electric motor failure does still occur. When it does strike, it can be difficult to know just what to do. As business downtime and losses mount, it's very easy to make a panicked decision over whether to rewind and repair or replace your motor.
When faced with such a conundrum, motor owners must carefully consider how they act. With new high-efficiency motors available, do they take the plunge and invest in a whole new motor altogether that promises higher efficiency levels but with significantly greater costs? Or, do they commit to a motor repair or rewind? While the cost is often lower, many are concerned about the potential inefficiencies that an electric motor rewind can bring — yet are these worries grounded in fiction?
The association of motor rewinds with inefficiencies can be attributed to a limited number of studies involving smaller motors. It is claimed that carrying out a rewind can drop efficiency by between 1% and 5% each time it is rewound. Considering the associated expense and sheer volume of energy these motors use, this is naturally concerning. However, more recent research has countered these findings.
EASA and AEMT, alongside Nottingham University, tested 22 new motors from 50 to 300 hp. Overall, the results found that when electric motors were rewound using good practice, there was no significant change in the efficiency of the motors. However, in some instances, efficiency actually increased. This clearly dispels the belief that a rewind is actually detrimental to a motor's performance.
As the above results suggest, you may not need to purchase an expensive new electric motor. Of course, in cases of catastrophic failure, this may be your only option. However, it's very important to fully evaluate your options to make sure you make the right choice in terms of operation, cost and efficiency. This can be done by asking a number of key questions, as explained by Houghton International.
How suitable for purpose is your electric motor?
As your operational needs shift, you may find that your existing electric motor is now unsuitable. Review the scale of the damage alongside the requirements for the motor's processes and duty cycles. If the motor is no longer suitable or too damaged, your option is to replace the motor.
Have you checked the condition of the stator core and rotor?
Where suitability isn't a concern, next check the stator core and rotor. If significant damage is present, it may be more beneficial to purchase a new motor, as depending on the extent of the damage, repairs can be costly.
Fully consider your options when buying a new motor. For example, if the lead times for the motor you need are long, you may to decide to repair rather than replace to minimise downtime.
Is there any other damage to mechanical parts?
In the event of motor failure, you may find that the shaft, frame, bearing housing and other mechanical parts are damaged. Examine the extent of the damage; you may be able to replace the affected parts at a lower cost than replacing the entire motor.
Do you have an EPAct or Nema Premium motor?
Many use motor failure as the excuse they need to upgrade to a more efficient model. If you are considering making the investment, make sure you fully understand the return you'll receive from doing so. Consider the energy savings you'll make alongside the expected life of the motor and its hours of operation. Always consider your overall budget too, to make sure the replacement aligns with your current financial position.
If you are happy with your existing motor efficiency, getting your electric motor repaired at a qualified service centre will not see a dramatic drop in this efficiency.
Before you can make the right choice between electric motor repairs, rewinds and replacements, you must first consider your operational needs, budget and timescale.
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