Keeping motors running

MOTORS may have been engineered to have high durability and long life, but it does not negate their need for regular maintenance.

Long-term or extensive use of motors can cause a number of problems if motors are not maintained properly, including overheating and bearing failure.

 According to Frank Cerra, engineering manager with SEW-Eurodrive Engineering, motors in general are very reliable pieces of equipment.

"Motors are typically designed to have long life and require little maintenance, especially when sized correctly for the application and built to modern specifications," Cerra told Manufacturers’ Monthly.

"What manufacturers need to worry about with the use and maintenance of motors is to ensure that temperature rise over time does not exceed the motors’ insulation rating and making sure they are adequately protected from the overload," he said.

To keep motors in check, Baldor Australia managing director, Daniel Vera, advises maintenance on motors should be performed on a regular, quarterly basis.

"We advise inspecting the motor at regular intervals, approximately every 500 hours of operation or every three months, whichever occurs first. However, certain applications may require more frequent inspections due to harsh operating environments as well as age, size and load of the motor," Vera said.

Performing regular inspections can prevent common failures, such as overheating, bearing and insulation failures, bad connections and irregular noise and vibration. In the case of bearing failure, Vera says the key is ensuring the bearing is lubricated. This, he explains, is because grease will lose its lubricating ability over time, leading to eventual motor failure if unmaintained.

"The lubricating ability of the grease over time depends primarily on the type of grease, the size of the bearing, the speed at which the bearing operates and the severity of the operating conditions," Vera said.

"Failure to lubricate bearings will lead to additional motor loading, bearing heating and ultimately, failure."
But for many manufacturers working with motors, the big question remains: How to diagnose problems before they arise? According to Vera, general and specific inspections can assist manufacturers to monitor the functionality of the motors and locate potential motor problems before they arise. General inspections ensure motors are kept clean from dirt, oil, grease and any fluids that could prevent proper motor function.

Checking the interiors and exteriors of the motors, as well as all electrical connectors to ensure that they are tight, and the cables and insulation are intact will help to prevent the accumulation of such particles which can block motor vitalisation, says Vera.

Completing specific tests will help to narrow the scope of potential motor failures, including current/power and voltage test which can be used to measure the current drawn by the motor under peak load conditions.

Equally as important, Vera says, is to immediately investigate any significant drop in insulation resistance which can be completed through insulation testing.

For the larger part, motor maintenance is about keep energy consumption and thus energy costs down. SEW-Eurodrive’s Cerra notes that the key to reducing energy is to use an efficient motor and to take a closer look what the motor is driving.

To reduce the energy used by a motor, you need to look at the whole drive system and optimise it. That is the motor, the gear box and the end process that is being driven, be it a pump, fan, compressor or conveyor, because that’s what is actually consuming the energy," he said.

"Sometimes replacing inefficient motors can also be a better option than getting motors re-wound or having older design motors refurbished.

By putting in a modern, high efficiency motor that will use less energy, the cost saving as a result can see manufacturers recover the cost of the motor within a reasonable payback period."

And with electricity charges going up and greater industry focus on reducing emissions, Cerra argues that having an efficient motor and an efficient drive process does reduce power consumption and energy costs.

"What we encourage people to do is to look at the process and optimise it. This means using a higher efficiency motor, getting a efficient gear box and looking at what it is driving," he said.

"Getting the most efficient designs for all components that drive the system will help to lower the overall energy consumption and reduce energy costs. Manufacturers can use also use variable speed drives to optimise the process speed to achieve further energy savings. With the motor speed and output power optimised to the demands of the process instead of running a full speed, manufacturers can reduce their energy consumption and save on electricity costs."

SEW-Eurodrive, 61 8 8161 4000, www.sew-eurodrive.com.au
Baldor Australia, 1300 225 367, www.baldor.com.au