If a tree falls in the forest, does it make a sound? If an electric motor fails, what does it say?
As it turns out, a failed electric motor says quite a bit. UE Systems identifies 50 failure modes, if correctly interpreted and acted upon, can extend the life of an electric motor.
Electric motors are essential to numerous plants operations, no matter the industry, which is why understanding their 50 failure modes can help you develop a better maintenance program in your plant.
Electric motors are essential for making sure that plants are running smoothly and effectively. If one fails, it can mean costly downtime for the plant and create a variety of safety hazards. There are a number of different failure modes out there, so by understanding them, the lifespan of a motor can extend from two to 15 years.
The key is moving from the reactive category of the PF curve to the predictive phase. By using ultrasound technology, such as the Ultraprobe 15,000, you can detect problems before they start to create serious damage in the motor. Because there are so many different components within a motor, a failure mode can emerge in a variety of places. There are between 8 and 10 components within a motor, each with its own failure modes, bringing the total to around 50, so by properly addressing them, you can greatly extend the life of your motor.
UE systems begins with motor housings, stators, rotors, and bearings:
Motor housing: Failures in motor housing can crop up from improper installation, physical damage, corrosion and material buildup. While motor housing may not seem like a true performance component, these shortcomings can ultimately affect the way others perform.
For instance, a soft foot could lead to bearing failures, shaft bending and broken or cracked feet. This emerges if a motor, when placed in a flat surface, does not have all its feet flat on the surface. Material buildup can heat up the operating temperature of the motor, ultimately leading to damage on other parts of the motor, such as bearings.
Motor stator: Motor stator failure modes emerge from physical damage, contamination, corrosion, high temperature, voltage imbalance, broken supports and rewind burnout procedures. A lot of times, these can emerge from motor repair shops.
Stator failures occur due to the rewind burnout of the windings. This often happens before the motor can be rewound requiring emergency repairs. But because the plant will need the motor returned as soon as possible, hasty repairs can end up damaging the stators by improperly heating the housing and the stator. This can also lead to motor inefficiencies.
Motor rotors: Rotors are composed of numerous layers of laminated steel and the rotor windings are composed of bars of copper or aluminum alloy that is shorted on both sides with shorting rings. These components can then fail through thermal stress, physical damage, imbalance, broken rotor bar, contamination and improper installation.
Physical damage on rotors can develop after certain emergency maintenance tasks including bearing replacement, motor rebuilds and during a disassembly and reassembly process. Generally speaking, motor bearings should not be changed at plant locations and especially on critical equipment.
Imbalanced motor rotors are common, but this can put a lot of strain on bearings. This will ultimately lead to a rotor making contact with a stator and creating another point of failure. Again, improper rebuilding tactics, such as overheating, can damage rotor components as well.
By establishing precision balance standards, you can be sure you are preventing these kinds of imbalance failures.
Motor bearings: Motor bearings within an electric motor can emerge from improper handling and storage, improper installation, misalignment, improper lubrication, start/stop processes, contamination, overhung loads and motor fan imbalance.
Contamination is one of the biggest reasons for bearing failure modes. This occurs when foreign contaminants or moisture enter the bearings, usually during the lubrication process. You can take steps to prevent contamination during the regreasing process to ensure that they are kept out.
It is also important that your motor is properly outfitted for the task for which it was selected. This means using the right bearings for its application. Motors that are using sheaves or sprockets that are mounted on the shaft will need roller bearings in the motor, which are common among most standard motors.
Lubrication can always be a major cause of failure because there are so many different places where one can improperly apply lubrication. Too much or too little lubrication, along with the improper form of lubrication, can lead to premature wear and tear. All motor greases should be polyurea-based, and not all-purpose greases. One should always take the plug out of the bottom so that old grease can be drained properly. Also, release valves can help prevent over greasing.
In what is an incredibly well researched article, UE goes on to work through the rest of the error codes. Please read through the whole article.
Ensuring proper application, engineering, installation, and performing regular predictive maintenance programs are excellent ways to operate your electric motor, but as you know, there’s no guarantee any or all of these will prevent failure. However, knowing what caused a failure is half the battle to fix it.