Industry relies on electric motors to keep assembly, production, and packaging lines moving. While motors vary by shape, size, and output, they all have two universal needs to operate: bearings and lubrication. As part of our commitment to keep you up and running, today’s discussion covers the different types of bearings, their specific application, and lubrication needs.
Electric Motor Bearing List
This list includes the most common bearing types used in industrial electric motors up to 200 HP. Always double-check the manufacturer’s data to ensure you use the correct bearings style for warranty requirements and maximum performance and longevity.
Basic Ball Bearings
These (nearly) perfect round bearings are typically used in direct-coupled, non-belted applications with 150 HP or less. Their round shape allows them to handle axial and radial loads efficiently.
Standard Roller Bearings
These bearings are used in belted applications with 150 HP or higher motors. They are designed only for radial loads and should not be used for axial loading.
Cylindrical Roller Bearings
Available in a wide variety of sizes and configurations, these bearings are typically used with gear or belt-driven motors. Their unique design makes them ideal for medium—and high-speed applications with a high axial load.
Deep Groove Ball Bearings
Feature a simple design that works well for high-speed operation with moderate axial and radial loads. Their bearing options include pre-lubrication, seals, and shields for use in contaminant-rich environments and locations.
Angular Contact Ball Bearings
These bearings are designed for within electric motors operating at high speeds with high axial load ratings. Ideal for most cage designs, they can be arranged in single or double rows for increased performance and durability.
Shielded Bearings
Utilize a shield to protect the bearings from contamination during normal operation. These bearings can be relubricated with packing grease after relieving any internal pressure buildup that could force the shield against rolling elements or the motor cage.
Sealed Bearings
This design is typically used for smaller electric motors to minimize contamination issues. Unfortunately, sealed bearings cannot be repacked after installation, meaning they have a predetermined lifecycle. Sealed bearings should be routinely checked so they can be replaced before the bearing ultimately fails.
Electric Motor Bearing Lubrication
While every electric motor or rotating equipment requires lubrication for maximum operating efficiency and longevity, not all lubricants and lubrication systems are equal.
For some bearings and electric motors, simple grease lubrication may suffice, while other situations require complex circulating oil systems and specific oil blends. Always defer to the manufacturer’s recommendations to ascertain the proper lubrication products for your electric motor.
Grease Lubrication
Unlike oil, grease is a semi-solid lubricant designed to remain in place to protect bearings and motor shafts against friction, corrosion, and excessive wear. However, grease does not protect against heat build-up in rotating equipment like oil.
NLGI 2-grade grease is usually used for electric motors with horizontal shaft configurations, while NLGI 3-grade grease is the industry standard for vertical shaft arrangements.
Grease is available in a variety of formulas, including.
- Lithium
- Moly
- Silicone
- Dielectric
- Marine
- Polyurea
Always check the manufacturer’s recommendation for your electric motors’ correct grease formula, including any required additives.
Electric Motor Lubrication Options
Protecting the electric motor’s internal components typically utilizes oil and one of the four following lubrication systems options.
Splash Oil Feed Systems
This system delivers oil much like an internal combustion (gasoline) engine. As the motor turns, oil “splashes” onto the moving parts near the top of the motor. As gravity returns the oil to the pan or storage reservoir, the oil can lubricate the internal bearings and bushings. This system is not recommended for high-speed motors, as the oil can churn and reduce the oil’s cooling ability.
Drip Oil Feed Systems
With this system, oil is delivered at a constant rate through a supply tube or manifold from the reservoir. Needle valves at each lubrication point allow the operator to adjust the oil flow based on motor speed and load.
Systems where one reservoir supplies oil to one bearing or bushing are known as single-point systems. When one reservoir supplies oil to several lubrication points, it’s called a multi-point system.
Most drip oil feed systems can be pressurized to supply oil to a bearing or bushing operating under pressure to reduce wear while extending the component’s lifecycle.
Forced Oil Feed System
This option is ideal for high-speed systems, including turbine generators, compressors, gearboxes, and boiler feed pumps. As the operating speed increases, more oil is needed to dissipate heat and reduce friction.
In this system, oil is forced from the gearbox to the reservoir, where the oil pump pressurizes the oil before sending it to each component. From there, the oil passes through an oil cooler before returning to the gearbox.
Automated Lubrication Systems
These systems deliver oil at short and frequent intervals while the electric motor is running, helping to reduce wear and operating costs simultaneously.
Single Line Parallel Systems use one line and automated valves to carry the oil to and from the reservoir or pan.
Double Line Parallel Systems use two lines to move the oil. One is to supply the oil, and the second is to return the oil to the pan or reservoir.
Multipoint Direct Systems utilize an auxiliary motor to open and close the cams, delivering a precise amount of oil to the lubrication points.
And that wraps up our overview of electric motor bearings and applications. Follow this link for more tips about eliminating electric motor failure caused by improper lubrication. If you still have questions about the correct lubrication or lubrication systems for electric motors, call us at 800-713-0103, or you can send us an email with your questions.