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Dover, Delaware

© 2016 by Square One Electric Motors

Equipment Storage

It's the middle of your shift and a motor goes up.


No problem, you have a spare.


But when you pull it from the shelf, install and start it up, this motor starts squealing worse than the one you replaced. What went wrong?


Very likely, you are a victim of poor motor storage maintenance.

  • Are you running out of space for your electric motors and equipment?

  • Do you have machinery sitting outside in the elements?

  • Did you know that there's a better way?

Square One Electric Motor's Equipment Storage Program is a low cost and highly beneficial system for managing your assets. 

What's included:

  • **Equipment pick up and delivery

  • Shaft protection

  • Blue layout 

  • Caps on threaded ends

  • Palletized

  • Cover for dust protection

  • Desiccant packets for moisture absorption

  • Tagged for monthly shaft rotation

  • Computer log

**Large equipment requiring a dedicated truck may incur additional fee for shipping. Standard delivery is included - emergency deliveries will incur additional fee.

Click here for our Motor Storage Flyer.

Even when an electric motor is not being used, it can obtain damage:

  • Bearing grease may harden after sitting for years

  • Rust can collect on the shaft and keyway

  • Condensation can damage the windings

  • Rodents can chew the leads or nest inside the stator (we see this with pumps a lot!)

  • Long term vibration can create wear

Motor Storage Basics


Appropriate storage procedures can protect a motor from environmental damage. Determine which steps to take based on where and how long the motor will be stored.


  • Less than one month: Protect the motor from the weather and keep the winding temperature 5-10°C (10-20°F) above the ambient.

  • More than one month: Follow the recommendations “Preparation for storage” and “Periodic maintenance” (below).

These storage and maintenance intervals aren't absolute; specific environmental conditions may require different schedules. It's not always practical to treat smaller motors with the same care as larger or more critical machines.


Preparation for Storage


  • Indoor storage: If possible, store motors in a clean, dry, heated area.

  • Outdoor storage: If this is necessary, loosely cover the motor with a tarpaulin that reaches the ground but allows enough air circulation to minimize condensation. Protect the motor from flooding and harmful chemical vapors. 

  • Ambient vibration: Choose a storage area away from ambient vibration sources like heavy construction equipment, production floors, busy roads, and rail lines. When a motor isn't rotating, prolonged exposure to even low-magnitude vibration can damage bearings (ie - false brinelling). Lock the shaft to prevent any movement if a motor must be stored in an area with high ambient vibration.

  • Position: Store horizontal motors horizontally and vertical motors in stable vertical positions.

  • Keep motor windings clean and dry: The best way to preserve the insulating properties of the windings is to prevent condensation and accumulation of moisture. Unless the storage area is climate controlled, keep the winding temperature 5-10°C (10-20°F) above the ambient by energizing the space heaters or by "trickle heating" one phase of the winding with low voltage. Another option is to keep the winding warm with an auxiliary heat source by convection or by blowing warm air into the motor. 

  • Insulation resistance (IR) of the windings: Measure and record the IR and correct it to a standard temperature before storing the motor, and again just before putting it in service. Address any drop in IR before installing the motor. 


  • Pests: Take precautions to keep animals and insects from entering the motor. Rodents, snakes, birds, or other small animals can damage the winding insulation, and mud dauber wasps and similar insects can block ventilation or drain openings.


  • Motor surfaces: Coat all external machined surfaces (especially shaft extensions) with a rust preventative; also coat the bearing journals and other interior surfaces in damp environments. Apply a fungicide to protect the windings in tropical areas. Disassembly may be required to remove the protective coatings before the motor is put in service.  

  • Grease-lubricated bearings: To prevent corrosion and contamination during long-term storage, clean the grease fitting and remove the drain plug before inserting compatible grease. Following relubrication, purge the excess or old grease from the grease chamber by running the motor at least 30 minutes with the drain pug removed. 


If the motor has been stored for several years, the grease probably will have hardened, and the drainpipe may be plugged with dried grease. In that case, the motor must be disassembled to remove the old grease and then relubricated before being placed in service.


* Don't relubricate bearings with the drain closed or while the motor is running. 


  • Oil-lubricated bearings: Always drain the oil before moving the motor. After situating the motor in the storage area, fill the reservoir with the correct oil and appropriate rust and corrosion inhibitors. Ideally, the oil should cover the bearings completely without overflowing the stand tube or labyrinth seal. Drain and replace the oil before putting the motor in service.


*Always drain the oil before moving a motor. Otherwise, oil may slosh out of the reservoir and contaminate the windings, or even initiate capillary action that can suction oil from the reservoir.


Periodic Maintenance

  • Monthly: Inspect oil for evidence of moisture, oxidation, or contaminants. Replace the oil whenever contaminants are noted, or every 12 months.


  • Every 1 to 3 months: Rotate the shaft several times to maintain a film of lubricant on bearing races and journals. This also helps protect rolling bearings from damage that can occur over time due to even low-magnitude vibration.

  • Every 2 to 3 months: Measure the insulation resistance (IR) and compare the temperature-corrected results with baseline readings taken before the motor was stored. Address any drop in the insulation resistance before installing the motor. 


  • Every 3 months: Inspect grease-lubricated bearings for moisture, oxidation, or contaminants by drawing a sample from the drain. If moisture is present, the bearings have probably sustained rust damage and need to be replaced.


  • Every 5 years: Consider replacing the grease and rolling bearings. By this time, the oil and base ingredients of the grease have probably separated, and low-level vibration may have caused false brinelling of the bearing races. Corrosion staining or rust damage may also have occurred if moisture has collected between the balls and races. 


For more information contact Square One Electric Motors today.

Content credit: Electrical Apparatus Service Association; "Getting the most from your electric motors"