Industrial Motor Health Tips | Modern Maintenance Solutions

Industrial motors are, quite literally, the driving force of manufacturing.

Keeping electric motors healthy and operating properly can greatly affect production. According to a report from the Department of Energy, an average motor’s life cycle might be from 30,000 to 40,000 hours. When it comes to motor health, regular monitoring and maintenance will increase its life cycle.

 

Parts and Problems

Industrial electric motors do not actually have that many parts, but each part is obviously critical. Most motors contain windings, a stator (stationary part), a rotor (rotating part), end bearings, and a shaft. Keeping motors clean and free of debris will increase their life cycle. 

By design, motors stay clean from outside sources like dust and water when selected with a sufficient housing ingress protection (IP) rating. An IP rating has two numbers. The first number indicates the housing protection rating against solid particulates, while the second number is the rating against liquid ingress. 

If motors are in a dusty, harsh, or sanitary wash-down application, knowing the motor's IP rating will be important. However, regardless of that rating, humidity, corrosion, and contamination can still occur. Regular monitoring of the motor's temperature and humidity can indicate when maintenance might be required. 

 

Cleanliness

Pneumatic air gun tools can be a great way to blast a motor with air to remove any suspected contaminants built up within the housing of a motor, if there are openings. Be careful that the air source is clean and that more debris isn't forced into the motor. Even if there are no openings, regular cleaning can expose the metal casing and return the heat-dissipation factor to its intended quality. Thick dust can insulate the motor and cause it to overheat.

 

Figure 1. Disassembled view of an electric AC motor. From left, the front end case, the rotor, the main body with the stator, and the fan at the back end. Image used courtesy of Adobe Stock

 

Bearings and Lubrication

While removing dust and dirt from the outside might help a bit, it is important to understand how humidity and temperature can affect the lubrication inside. Some motors and bearings are sealed, which means they are considered lubricated for life and should be left alone. In fact, you can accidentally cause increased wear and tear by damaging seals and over-lubricating. 

 

Tip: Know and Document the Lubrication Plan

Motors and bearings that require lubrication will not only need a maintenance plan but should have proper documentation. Technicians and managers alike should have access to maintenance information. This should include any manual or data from the OEM on operation specifications and maintenance. 

When it comes to documentation, the more information, the better. For example, include the date and hours of operation. If an OEM indicates a motor to be re-lubricated every year based on a single shift of operation, but you use the motor for fluctuations in production, having the manufacturer's information, data, and operational hours of the motor will help ensure maintenance is done on time. 

There are multiple ways to monitor lubrication. You can check filters for contamination before startup, or pressure, temperature, and flow sensors could provide information during operation. Many monitoring products offer a wide range of operations and applications so some sensors used on pumps or hydraulic applications may also work to monitor electric motors.

 

Tip: Documenting Routine Operation Data is Also Important

Common data can establish a baseline and how factors change over time. This data can help pinpoint whether something is a common or a special occurrence. 

Monitoring lubrication isn’t the only variable to ensure a healthy motor. Data such as vibration and non-lubricant temperatures can help monitor motor health. Also, having more data can provide accurate information for predicting maintenance, preventing failures, or troubleshooting motor problems. One way workers are able to monitor or troubleshoot motors or bearings is based on how they sound. 

A screech or squeal might indicate a lubrication problem. A clang or clatter might indicate that the bearing ring has deformed and needs to be replaced. Scoring on the ball or race in the bearings could produce a hissing sound. It may require years of exposure and experience to be able to pick up on these sounds.

Working environments might have ambient noise making sounds hard to detect. Also, human ears may not be able to detect a sound until it is too late and a motor must be shut down for maintenance.

 

Figure 2. This motor has a magnetically-mounted vibration sensor for condition monitoring. Image used courtesy of Fluke

 

Operating and Starting

While attentive workers are important, temperature and vibration sensors will provide higher fidelity and quality detection of motor performance. For example, variable frequency drive (VFD) motors are becoming popular in some applications. Operating at different speeds can cause vibrations to fall within the natural frequency of a system. 

Workers might not be around, notice, or know why vibrations increase seemingly at random. However, sensor packages able to log data throughout operation might show an increase in vibration is only happening at a specific speed. Having this information can reduce or eliminate the time spent operating at speeds that cause excessive vibration.   

 

Tip: Know When to Use a Soft Start Vs. VFD

If an application runs at a constant speed, a VFD might not be necessary and would incur a higher cost compared to a soft start solution. These days, VFDs might just provide more communication functionality to justify the extra cost, but still, any unnecessary function would be considered a waste of budget.

Problems concerning VFD might introduce new challenges, but most engineers understand that wear and damage on motors, bearings, and gearboxes tend to accelerate when faced with more frequent start/stop cycles. While there isn’t much maintenance or monitoring can do to reduce this, devices can be added to provide a softer or more gradual start. Both soft starters and VFDs can ramp up speeds to reduce wear and damage associated with starting a motor.

 

Healthy Motor IIoT Solutions

Tip: Most Monitoring Solutions Focus on Temp and Vibration

There are many monitoring devices available. Fluke offers a thermal imaging camera that can show the temperature of a motor. It can’t look inside, but most industrial motors will have a tag indicating a normal operating temperature that the camera is able to verify at a glance. Additionally, thermal cameras are able to detect temperatures over the entire motor or an area that can help when troubleshooting temperature concerns.

These days, thermal cameras that connect directly to smartphones are becoming cheaper, and they honestly might be a valuable addition to a technical toolbox.

 

Figure 3. A thermal imaging camera. Image used courtesy of Fluke

 

There are many types of vibration sensors. Some solutions are easier to retrofit depending on your equipment. For low-voltage motors, many companies like ABB, SICK, Balluff, Banner, and others offer sensor packages that are easy to install and connect. The package is installed on the outside of the motor (often magnetically) and can collect data on a network external to the production network. Data can be uploaded to PCs or cloud servers for processing and analysis, or displayed on a mobile device.

Wireless sensors further reduce the needed infrastructure and wires to integrate monitoring devices quickly for manufacturing and motor applications. Parker Hannifin offers battery-powered SensoNode wireless products that are able to monitor pressure, temperature, and humidity in many applications.

Wireless transmission may be enabled by Bluetooth, Wi-Fi, Sigfox, LoRA, cellular, or RF communication. Each one has strengths and weaknesses, and in some cases, the sensors really need to be hard-wired for absolute reliability. But with monitoring, there is often a bit more forgiveness for an occasional drop in connection.

 

Tip: Changes in Temp and Vibration Indicate Problems

Reading the data from the sensors is not as clear as with production data. Pressures and temperatures of a product line might immediately indicate an alarm, but with condition monitoring, the data points to trends over time. Hardware collects the data, but it requires analysis to figure out when problems might be occurring.

Some companies offer developer kits that include the software. These may include the sensor(s), downloadable software, and developer tools so companies can create their own solutions. For example, Bosch Rexroth’s XDK can be strapped to a motor and start collecting all kinds of data, including temp, humidity, vibrations, light, and more. These products can be used for experimentation and exploration, often leading to a more permanent solution, but they provide a lot of value.

 

Consistent and Predictable

Whatever you use, paper and pencil, connected sensors, etc., monitoring and documenting motor information will give you the data needed to keep motors healthy and improve life cycles. Turning to sensors and more advanced solutions with the rise of so-called IIoT technologies, many companies are adopting these advanced solutions as a way to extend asset life.

 

Featured image used courtesy of Adobe Stock

Article originally published 10/2020