Maintaining Your Industrial Motor in the Winter

During the winter months, cold temperatures and icy weather can wreak havoc on electric motor applications if not adequately prepared for the conditions. Just a few degrees can make all the difference. With the right equipment selection, adequate preparation, and a suitable maintenance schedule, these problems can be dealt with and maintained throughout the winter season.

Electric motors and parts are typically rated for temperatures between 40°C (104°F) down to as low as -20°C (-4°F). Factors including lubrication, condensation, brittle materials, demagnetization, ventilation, and others play a factor when selecting or maintaining a motor for a cold environment. Even in temperatures inside the lower end of this range, many of these tips will improve the motor operation and ensure that it runs at peak performance.

In Canada, it’s common to see temperatures below -30°C, especially at night. Consider the below factors for your motor applications to increase the lifetime of your motor.

Lubrication

Insufficient lubrication and maintenance of bearings account for the majority of electric motor failures. With the added challenge of cold temperatures, it's even more critical to ensure that bearings are adequately maintained.

As the temperature drops, the bearing lubricant becomes increasingly tacky and viscous, making it difficult to achieve an even distribution throughout the bearing, and creating areas of increased friction and stress.

When storing motors in a cold environment, ensure to rotate the shaft periodically to distribute the lubrication and prevent it from collecting in one spot inside the bearings. To ensure your motors are ready to go when required, consider testing stored motors as part of a regular maintenance schedule.

For grease-lubricated bearings, typically found on small to medium-sized motors, operating the motor in temperatures below the typical range will usually require a special low-temperature lubricant. Oil-lubricated bearings, commonly found on larger motors, may need a temperature-controlled sump to keep the oil at a sufficiently high temperature.

Consulting with a supplier is a great way to ensure you're using the bearings within the rated specifications. Your trusted supplier should also recommend options for products that may be better suited to colder climates.

Here is a step-by-step guide to lubricate your motor.

Condensation

Moisture inside a motor can cause deterioration and short-circuiting of the motor windings and corrosion of metal components, leading to potential downtime and part replacement costs. Unless the motor is periodically disassembled and inspected, much of the damage is unseen until the motor performance is significantly impacted.

What causes condensation inside a motor? When a warm motor is turned off in a cold environment, the body cools faster than the air inside the motor. This creates water droplets on the inside of the motor body. Gravity and vibration can quickly spread water droplets over critical components.

If using a TEFC (Totally Enclosed Fan Cooled) motor, fit the motor with a drain plug, opening it periodically to release accumulated moisture. TEFC motors are sealed but are not always airtight. Heating and cooling cycles (especially over a wide temperature range) will create pressure that draws small amounts of air and moisture inside. Especially in Canada, nighttime and daytime temperatures can vary greatly, causing moisture accumulation in motors exposed to the cold.

To prevent condensation, install a space heater inside the motor. The space heater maintains the air temperature inside the motor above the point where condensation will form.

Brittle Materials

Plastic and rubber materials are especially susceptible to cold temperatures and can become brittle and prone to fracture when exposed to the cold.

As part of a preventative maintenance schedule, inspect seals, fans, and brackets for cracks or deterioration signs. These are the parts of the motor that experience the most significant forces and vibration. If a part fails, consult with your supplier about possible alternatives made from more resilient materials, such as steel or bronze.

Demagnetization

The magnetization levels of permanent magnets in DC motors may be significantly reduced in icy environments, impacting the motor's performance. Both the motor torque and speed are directly related to the magnetization level. The effect is most significant when operating the motor at low voltage and high current (low speed, high torque operation). The motor may struggle to provide the performance required from it.

If you cannot operate your DC motor in a climate-controlled environment, it may be necessary to fit the motor with insulation to protect the magnets inside from the cold. Ensure that the insulation allows free passage of air through the cooling vents. Consult with your motor supplier for expert technical support.

Ventilation

As improbable as it sounds, overheating is a common problem in electric motors exposed to cold winter weather. Ice and snow can build up over the motor body, blocking the cooling air passage that carries the heat away from the motor windings. Ensure that the motor's ventilation ports are always clear from debris, ice, and snow, with uninhibited access to cooling air.

Excessive Duty Cycle

Some motor applications are meant to run primarily in colder weather, such as a heating system motor. Ensure the motor is being run within its specified duty cycle to prolong the motor's life.

What is duty cycle? The duty cycle is the ratio between the period it's switched on to the period it must be switched off to prevent excessive wear and tear. For example, if the motor's duty cycle is 4:1, the motor may run for 24 hours but must be turned off for 6 hours.

When selecting a motor that will run in the winter months, ensure it can run during the required duty cycle.

Explosion-Proof Motors

An explosion that occurs within a cold motor creates a significantly higher pressure inside the motor than in warmer conditions. This pressure creates stress on enclosures, seals, and flame paths, which compromises the safety of surrounding people, equipment, and infrastructure. It's imperative to purchase an explosion-proof motor that's adequately rated for the application temperature. When in doubt, consult with your supplier for expert support.

Summary

Cold winter climates create a range of electric motor issues, especially those directly exposed to the outside environment. With a clear understanding of these issues and how they arise and the right preparation and maintenance, risks can be minimized or avoided altogether to maintain productivity throughout the cold season.