How To Store An Electric Motor

Short-Term & Long-Term Electric Motor Storage

Often, motors are placed in storage until needed. Here are tips on storing an electric motor for both short-term (weeks or months) and long-term (years).

Short-Term Storage

• Protect the motor from the elements, vibration, and extreme heat.
• Indoor storage is preferable.
• When storing outdoors:
• Wrap the motor loosely with a rain-proof tarp but leave a space around the bottom to allow airflow. If wrapped tightly, condensation will build up inside the motor from the heat of the sun and lack of ventilation (otherwise known as solar still).
• Energize space heaters (if included) to maintain a winding temperature of 10°F to 20°F above the ambient temperature (consistent heat is best for preventing condensation buildup but extreme heat and lack of ventilation will cause it).

Long-Term Storage

• Location
• Indoors in a clean, dry, environment with minimal to no vibration, such as away from railroad tracks and major freeways.
• Consider “floating” the motor on a vibration-absorbing material or, if possible, hang it from overhead.
• Store the motor vertically if it is to be used vertically; store it horizontally if it is to be used horizontally.
• Prevent infestation of small animals such as mice or birds which can damage the winding insulation.
• Prevent insect infestation, which can block vents and drain openings by wrapping the motor loosely and covering all openings.
• Surface Preparation
• Coat the exposed surface areas to prevent rust and corrosion. Apply a rust inhibitor throughout the storage life of the motor. This will need to be cleaned and removed prior to placing the motor in service.
• Reapply the rust inhibitor often if stored in a humid or snowy environment.
• Coat the windings with a fungicide is stored in a tropical environment.
• Shaft Rotation
• Frequent shaft rotation is necessary to prevent false brinelling (damage to bearings caused by fretting ) and to redistribute lubricant.
• Rotate shafts on smaller motors a minimum of once per month.
• Rotate shafts on larger motors with capacity of 1500 HP and 1000 KW a minimum of once per week.
• Bearing Cavities
• On grease-lubed motors:
• Fill the bearing cavities completely for long-term storage.
• If moisture collects in the grease, drain and replace it.
• If the grease hardens over long-term storage, dismantle the motor, remove the grease, and repack the bearing cavities with new grease.
• On oil-lubed motors:
• Add just enough oil that contains rust and corrosion inhibitors to cover the bearings but not to so full that it overflows the stand tube or the labyrinth seal.
• Windings
• Windings must maintain a temperature of 10° F to 20° F above ambient temperatures to prevent degradation of the winding insulation. You can use either space heaters, if supplied with the motor, or a dehumidifier in the same room as the motor.
• Take a baseline insulation resistance (IR) measurement before storing the motor then a second measurement before installing the motor. Any decrease in the measurement can be addressed prior to installation, saving time and labor.
• Take a baseline polarization index of form coil windings prior to storage then again before installation. The PI should be taken once each year the motor is in storage, if applicable.
• Carbon Brushes
• To prevent a chemical reaction in DC machines, some synchronous machines, and wound rotor machines, lift the brushes away from the commutator and/or slip rings.
• To prevent weakening the springs, place them in a relaxed position, if possible.

Out of Storage and Into Service

• Before moving the motor:
• Measure the insulation resistance (IR) with a megohmmeter.
• Remove dust, dirt, and old grease.
• Drain if it is an oil-lubed motor.
• After installation:
• Record vibration levels.
• Evaluate the spectra on motors with rolling element bearings for any signs of bearing fault frequencies.
• Perform a vibration analysis during start-up.
• Document uncoupled baseline vibration levels.