Part 1 of a 2-part series
Part 1 – Motors in High Moisture Environments – How to specify the proper motor features to prevent reoccurring problems
Overview:
High moisture environments can lead to several contributing factors that lead to premature motor failure including:
Premature failure of motor winding caused by loss of insulation integrity.
- Motor winding insulation readily absorbs water from the surrounding environment.
- This can result in shorting from phase to phase and/or phase to ground.
Premature failure of motor bearings due to:
- Excess moisture in bearing grease resulting in degradation of lubricant.
- Excess corrosion of bearing components such as inner / outer race or rolling elements
- Corrosion of other critical components such as rotor, output shaft etc can also contribute to premature failure.
This article will address several commonly occurring conditions that lead to high moisture conditions that lead to premature motor failure with corrective solutions.
Condensation
When a motor is operated its temperature rises resulting in expansion of the air contained in the enclosure. When shut down the motor cools and outside air, as well as moisture, is pulled in. This commonly results in excess moisture inside the motor.
This is best addressed by the following:
- Adding space heaters to the motor winding: these are wired to operate when the motor is shut down. This ensures the temperature inside the motor remains above the surrounding air thus preventing condensation.
- Adding drains to the bottom of end housing: This allows condensed water to escape the motor housing. Drain hole position on motor dependent on motor mounting must be located at lowest points when motor is in its final orientation.
- Tropicalization of motor windings: Winding is treated with product having a high hygroscopic property that protect the motor from the penetration of moisture in insulation.
Wet ambient conditions
When a motor is operated in a high moisture environment steps must be taken to prevent ingress of moisture into the interior of the motor.
This issue can be addressed by the following steps:
- Upgrade motor enclosure to TEFC or TENV
- Adding shaft seals to prevent moisture entering from around the output shaft.
- Upgrade to a washdown duty motor: These motors were designed for food equipment and pharmaceutical industry where periodic wash down with high pressure water with cleaning agents is a requirement. These can also be used in other wet environment applications.
- Washdown motors typically include the following features: Enclosure in stainless steel or epoxy coated. Sealed bearings. Sealed construction includes lip seals, neoprene gaskets and other features to prevent water ingress
Stainless Steel and Epoxy Coated Washdown Motors – Courtesy ABB/Baldor
- An alternative is to upgrade to an IEEE841 chemical processing motor which, similar to a washdown motor has numerous features which to withstand harsh and wet environments
