Hurricanes Helene and Milton hit the southeastern U.S. last fall with a fury, leaving thousands of people displaced from homes and jobs due to damage from flooding and high winds. Following the storms, plant managers faced the daunting task of assessing the safety of both their facilities and their equipment. This included electric motors.
Motors are ubiquitous in plants and are especially critical to the operation of water and wastewater treatment facilities. Several of these plants were compromised from Helene and Milton and had to shut down operations for a time. Because this posed a great hardship for the communities in which they were located, minimizing downtime was a key driver. Manufacturing and processing plants were also under pressure to restore operations as soon as possible.
That pressure can become an issue when facility or plant managers are not aware of the steps to assess motors for damage, causing them to unwittingly start up motors without having them inspected by motor specialists. Unfortunately, the results can be disastrous and damaging and may even ruin the motors beyond repair.
To prevent these types of situations, this article provides guidance on managing motors in the aftermath of a storm, as well as the importance of having plans in place in advance to minimize damage from future storms.
Understanding the Problem
The harm done to motors by flooding and severe storms extends beyond rusted shafts and contaminated bearings and lubricants. Even brief moisture intrusion can compromise the insulation system, making the windings vulnerable to ground failures.
This is why all electrical motors should be inspected and evaluated by qualified Electrical Apparatus Service Association (EASA) motor repair service providers, either on-site (if that service is available) or by transporting them to a shop. This includes both open and enclosed motors, neither of which are watertight. Driving rain will not likely get into them, but flood waters will.
In addition to damage caused from water ingress, power surges or transformer failures can also damage the motor or reduce its life. Phase reversal can occur, causing the motor to run backward briefly, and this can result in either complete failure or a degradation in winding insulation. Shaft keys can be damaged by phase reversal or intermittent power spikes. Power changes can also break a motor shaft or pump shaft. This could be very obvious or it could be hidden, such as a crack in the shaft.
The following signs may indicate the motor is damaged:
- Rusted shafts
- Contaminated bearings
- Contaminated lubricants
- Compromised insulation systems
- Ground failures in the windings and rotor
Motors contaminated by salt water require specialized procedures for cleaning prior to being returned to service. The salt water must be thoroughly flushed from the equipment before it dries, or the residual salt can cause problems, such as:
- Rusting of the steel laminations in the stator and rotor cores
- Corrosion of the copper windings and aluminum or copper rotor cages
These conditions will result in motor failures, either immediately or in the near future.
Post-Storm Inspection
In the aftermath of major flooding to coastal and inland plant facilities, the impact of salt water, mud and moisture can be devastating to the many different types and sizes of electric motors used in a plant.
When this happens, quick decisions must be made to get the remediation project underway and to minimize costly plant downtime.
Below are the three critical “first steps” to take. Note: Never energize motors prior to a thorough inspection.
1. Assess water damage to all plant motors
- First, determine the highest flood water level that was reached by finding the water line along the interior walls as well as the insides of cabinets and outdoor storage lockers.
- Inventory all impacted motors. Note the location, motor name and all nameplate data for each motor. Also make note of the lubrication system used on these motors, if applicable.
2. Make quick repair and replacement decisions
Deciding as quickly as possible which motors to repair vs. replace provides the best chance of getting to the front of the line with the service shop as well as gaining access to new inventory from the motor distributor. Here is what to know:
- All T-frame motors subjected to salt water intrusion should be replaced. The repair cost and downtime make motor replacement the most efficient path to resume plant production.
- Motors with special features, such as U-frames or P-bases, and motors with shaft extensions (where replacement would be difficult or time-consuming) should undergo desalinization procedures.
- For older, less energy-efficient motors, replacement with energy-efficient U.S. Energy Policy and Conservation Act (EPAct) or National Electrical Manufacturers Association (NEMA) premium units meeting Department of Energy (DOE) efficiency requirements can save substantial energy costs.
- NEMA motors can often undergo desalinization procedures on-site in the plant facility.
- Prioritize motors by size and availability. The size priority in horsepower (hp) will vary from plant to plant, depending on the application, annual usage, energy costs and other factors. A reasonable place to draw the repair-replace line is between 100 and 200 hp (75 and 150 kilowatts [kW]).
- By replacing smaller motors with readily available energy-efficient models, plant operators free up capacity for their service repair center to concentrate on the larger, more costly motors that it makes more sense to save.
3. Implement remediation procedures
With the assistance of EASA-certified motor technicians, the following steps are recommended:
- Carefully inspect and test internal assemblies of larger motors to determine whether or not these components have been damaged by wind or rain (moisture ingress).
- Flush salt water from all internal and external motor components. Water damage to motors and generators is often greater than the obvious signs of rusted output shafts, fouled bearings and contaminated lubricants, so it is imperative to flush salt water before it dries.
- Perform any necessary special desalination and cleaning procedures required for salt water motor contamination. Some of these can be performed on-site, and others should be performed by an experienced electric motor repair facility.
Once the initial damage assessment is made, decisions on which motors to remediate on-site vs. which motors to send to the facility must be made.
Planning Ahead
Having a risk mitigation plan in place for motor care is key to reducing downtime and cost if motors have been damaged due to storms.
Long-term storage of motors requires regular maintenance, such as rotating the shaft and inspecting oil and grease monthly for moisture or oxidation. Storage and maintenance requirements are usually provided in operation and maintenance manuals from the motor manufacturer and should be consulted. This type of ongoing maintenance is necessary to protect the motor from failure and to maintain the warranty.
While it is impossible to protect all equipment from the effects of a severe storm or hurricane, it is possible to mitigate the impact through advanced planning and quick action in the days following the event.
The procedures outlined here can help speed the recovery for the plants in affected areas, as well as for the local populations that depend upon them for drinking water, employment and products. Planning in advance can also facilitate plant-service center partnerships and minimize downtime.
