Pillow block bearings are widely used in various kinds of industries and machines. They are used to support rotating shafts and transmit rotation between components, provide options for quick installation, simplify maintenance, etc. But the effectiveness and lifetime of these products rely heavily on good design, installation and care. A properly selected and installed pillow block bearing may last for several years without any problems, whereas even the smallest of installation mistakes can lead to premature wear, vibration and/or failure of a bearing.
What is the design of a pillow block bearing?
Pillow block bearings are two-piece, consisting of a housing and a bearing insert. The casing forms the shell of the pump and serves as support to allow the pump to be installed on its mounting. It is typically constructed from cast iron, ductile iron, or stainless steel. The insert carries balls or rollers to smooth shaft rotation.
Self-aligning A big feature of pillow block bearings is that they are self-aligning, so a little bit of shaft misalignment will not affect the performance. This makes them perfect for conveyors, agricultural equipment, fans, pumps and industrial drives.
Design should be selected where the load-carrying capacity is sufficient for application. For example, cast iron housings are commonly used in general industrial applications where resistance to environmental factors is not a factor and stainless steel or thermoplastic housings are more common in food processing or chemical industries due to the environment being relatively harsh. These can be used as modular designs for various belts.
How to Select a Pillow Block Bearing Design?
When selecting the right pillow block bearings design to best suit your needs, it is important to take into consideration two primary factors: mechanical aspects of the bearing mount and the environmental conditions in which it will operate. The most important parameters include:
- Direction and type of load —indicating whether the load would be radial, axial or a combination of both.
- Temperature to be used – Excessive heat or cold can alter lubrication and the properties of the materials.
- Dirt and Water — where dirt, water and other contaminants act as lapping compounds on the bearing raceways causing dents and bruises in the rolling elements, leading to rapid wear which can lead to early failure.
In the design of such a system, it is essential to mount the bearing on a flat rigid surface to properly distribute all loads. Imperfect surface mounting can cause misalignment which leads to uneven stress and excessive wear of the bearing.
Shaft and Fitment Considerations
Shaft condition directly affects the bearing performance. The shaft needs to be smooth, the same size, and free of burrs or rust. If the shaft surface is rough or out-of-spec, the bearing could be loose on the shaft and vibrate or may not fit at all resulting in early failure.
Be sure to measure the shaft size with precision instruments before use. Do also trial fit the shaft into the bearing bore because when testing, it become my biggest issue if any. Pressing the bearing in with force or striking it with a hammer can cause indentations on raceways and rolling elements, ultimately affecting their operation.
Correct Lubrication for Pillow Block Bearings
One of the most crucial elements when it comes to pillow block bearing maintenance is lubrication. It minimizes friction and metal to metal contact; suppresses rust formation, it is an extreme pressure lubricant.
The majority of pillow block bearings are grease-lubricated designs, as it is easier to retain the lubricant and maintain protection. In some high-speed or high-temperature applications, however, lubrication must be oil for improved heat dissipation.
Such bearings often have a grease fitting on the housing to allow reapplication of lubricant. Maintain the lubrication schedule specified by the manufacturer and use grease or oil as appropriate. Too much lubrication can result in seal failure and too little, overheating and surface damage.
A simple rule of thumb is lubricate bearings often, according to operating hours and the environment. It is also important to keep it clean while lubricating (don’t bring dirt, etc into the bearing).
Pillow Block Bearing Installation Guide
The quality of bearings installation is a great factor to the bearing lifetime and performance. The following information maintain the correct installation of pillow block bearings:
- Shaft and bearing housing must be well cleaned before installation to eliminate dirt, oil or other metals. Pitting and other uneven wearing can be caused by even the tiniest impurities. The mandrel is inserted on the shaft smooth side out and pressing the bearing insert onto it gently.
- With the bearing correctly located, verify that the shaft is in exact alignment with the mounting base. When misaligned, noise and vibration as well as uneven loading of the raceways can occur. When the shaft is installed properly, it can rotate in well condition and has a long working life.
- Tighten the mounting bolts to the specified torque setting and tighten housing further. Too tight can cause the housing or bearing insert to distort, too loose and the load will be able to move during operation. Use locking washers or thread-locking compounds to prevent bolts from vibrating loose.
- Once the unit is in place, rotate the shaft by hand to check for smooth rotation without any binding. If there is binding, noise, or uneven movement, inspect alignment and mounting torque.
Bearing Alignment and Load Distribution
Bearing straightness is one of the most ignored, but crucial installation elements. Misalignment increases load experienced by the rolling elements and result in excessive noise, vibration and heat generation.
When the bearing is subjected to combined radial and axial load, proper alignment can guarantee even load distribution on its raceway. For high-speed applications, a small amount of misalignment can cause dynamic unbalance and shorten the life of the bearing.
Self-Aligning bearings tend to move moreover can provide additional latitude for small misalignment and installation tolerances bringing you a more comfortable experience.
Environmental Protection and Maintenance Tips
Environmental concern is full consideration in the aspects of pillow block bearing design and maintenance. Bearings need to be protected from exposure to dust and dampness or any other environment which would corrode the surfaces of the moving parts. The service life of the bearing can be prolonged by installing protective cover or guard.
Routine maintenance is equally important. Operators should also watch for symptoms of noise, vibration or overheating that could be symptomatic of misalignment, overloading or insufficient lubrication. The detection of developing issues can avert catastrophic equipment failure.
While scheduled maintenance is undertaken, check the seals and if necessary re-lubricate and verify that no cracks or deformation are present in the housing. Running such equipment based on manufacturer scheduled maintenance intervals results in reliability and maximum uptime.
Conclusion
The performance and the reliability of pillow block bearing are essentially of considerable importance, which can be attributed to proper selection, design considerations and careful installation. There are many factors that come into play from selecting the right bearing type and getting it properly aligned, to keeping proper lubrication going on the bearings.
They work quietly because of the micro interference fit and are well suited for industrial use where large loads and high temperatures cause metal expansion. By taking these design and installation considerations into account, engineers and maintenance personnel can ensure bearing efficiency is maximized, with downtime minimized and performance optimized in their equipment.
