There are many different types of bearings available today with very little information on the differences between them. Maybe you’ve asked yourself “which bearing will be best for your application?” Or “how do I choose a bearing?” This bearing selection guide will help you answer those questions.
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First off, you need to know that most bearings with a rolling element fall into two broad groups:
Within these groups, there are sub-categories of bearings that have unique features or optimized designs to enhance performance.
In this bearing selection guide, we’ll cover the four things you need to know about your application in order to choose the right type of bearing.
Bearing loads are generally defined as the reaction force a component places on a bearing when in use.
When choosing the right bearing for your application, first you should find the bearing’s load capacity. The load capacity is the amount of load a bearing can handle and is one of the most important factors when choosing a bearing.
Bearing loads can either be axial (thrust), radial or a combination.
An axial (or thrust) bearing load is when force is parallel to the axis of the shaft.
A radial bearing load is when force is perpendicular to the shaft. Then a combination bearing load is when parallel and perpendicular forces produce an angular force relative to the shaft.
To learn more about axial and radial ball bearings, contact our team of engineers!
Ball bearings are designed with spherical balls and can distribute loads over a medium-sized surface area. They tend to work better for small-to-medium-sized loads, spreading loads via a single point of contact.
Below is a quick reference for the type of bearing load and the best ball bearing for the job:
Roller bearings are designed with cylindrical rollers that can distribute loads over a larger surface area than ball bearings. They tend to work better for heavy load applications.
Below is a quick reference for the type of bearing load and the best roller bearing for the job:
Bearing runout is the amount a shaft orbits from its geometric center as it rotates. Some applications, like cutting tool spindles, will only allow a small deviation to occur on its rotating components.
If you are engineering an application like this, then choose a high precision bearing because it will produce smaller system runouts due to the tight tolerances the bearing was manufactured to.
Bearing rigidity is the resistance to the force that causes the shaft to deviate from its axis and plays a key role in minimizing shaft runout. Bearing rigidity comes from the interaction of the rolling element with the raceway. The more the rolling element is pressed into the raceway, causing elastic deformation, the higher the rigidity.
Bearing rigidity is usually categorized by:
The higher the bearing rigidity, the more force needed to move the shaft when in use.
Let’s look at how this works with precision angular contact bearings. These bearings typically come with a manufactured offset between the inner and outer raceway. When the angular contact bearings are installed, the offset is removed which causes the balls to press into the raceway without any outside application force. This is called preloading and the process increases bearing rigidity even before the bearing sees any application forces.
Knowing your bearing lubrication needs is important for choosing the right bearings and needs to be considered early in an application design. Improper lubrication is one of the most common causes for bearing failure.
Lubrication creates a film of oil between the rolling element and the bearing raceway that helps prevent friction and overheating.
The most common type of lubrication is grease, which consists of an oil with a thickening agent. The thickening agent keeps the oil in place, so it won’t leave the bearing. As the ball (ball bearing) or roller (roller bearing) rolls over the grease, the thickening agent separates leaving just the film of oil between the rolling element and the bearing raceway. After the rolling element passes by, the oil and thickening agent join back together.
For high-speed applications, knowing the speed at which the oil and thickener can separate and rejoin is important. This is called the application or bearing n*dm value.
Before you select a grease, you need to find your applications ndm value. To do this multiply your applications RPMs by the diameter of the center of the balls in the bearing (dm). Compare your ndm value to the grease’s max speed value, located on the datasheet.
If your n*dm value is higher than the grease max speed value on the datasheet, then the grease won’t be able to provide sufficient lubrication and premature failure will occur.
Another lubrication option for high-speed applications are oil mist systems which mix oil with compressed air and then inject it into the bearing raceway at metered intervals. This option is more costly than grease lubrication because it requires an external mixing and metering system and filtered compressed air. However, oil mist systems allow bearings to operate at higher speeds while generating a lower amount of heat than greased bearings.
For lower speed applications an oil bath is common. An oil bath is when a portion of the bearing is submerged in oil. For bearings that will operate in extreme environments, a dry lubricant can be used instead of a petroleum-based lubricant, but the lifespan of the bearing is typically shortened due to the nature of the lubricant’s film breaking down over time.
There are a couple of other factors that need to be considered when selecting a lubricant for your application, see our in-depth article “How to Choose the Correct Ball Bearing Lubricant".
Spherical roller bearings have a higher load-bearing capacity and efficiency to handle heavy-duty applications. This blog from ZNL Bearings discusses a number of topics to aid in your understanding of spherical roller bearings.
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You might already be aware of what are bearings?, If not checkout here – What are bearings?
A rolling element bearing with spherical rollers that functions on the concept of rolling contact without sliding or fretting is referred to as a “spherical roller bearing.” Numerous applications where radial loading is necessary can use the bearing. Depending on whether there are one or two rows of rollers between the inner and outer rings, it can be categorised as either a single row or a double row. These bearings have found extensive use across a number of sectors, including the mining industry, Paper industry, steel rolling mill, construction equipment, off-road machineries, maritime, industrial transmission, and agricultural industries.
A spherical bearing is a type of bearing that allows angular rotation to occur about a central point in two directions that are perpendicular to one another (usually within a specified angular limit based on the bearing geometry). In most cases, these bearings are responsible for providing support to a rotating shaft within the [bore] of the inner ring. This shaft must not only rotate, but also move at an angle.
Both a hydrostatic and a mechanical structure are possible for spherical bearings. Spherical bearings, by themselves, are made up of an outer ring, an inner ring, and a locking device that only allows the inner ring to be held captive within the outer ring in the axial direction. They slide against each other, either with a lubricant, a maintenance-free, or they incorporate a rolling element such as a race of bearings, which allows for lower friction. The outer surface of the inner ring and the inner surface of the outer ring are both spherical, and both are considered to be part of the raceway. Spherical bearings find usage in a wide variety of applications, particularly those in which it is necessary to permit a rotational motion to cause a change in the alignment of the rotation axis.
The main function of bearings is to reduce friction between the loads, but under certain circumstances, the bearing may need to tolerate misalignment because of the design and requirements of a machine’s operation. It may involve rotating on a bent shaft where the shaft may flex as a result of an increased potential load or activity. In these situations, the spherical roller bearing serves as a lifesaver to overcome the many difficulties posed by manufacturing tolerances. The ZNL spherical roller bearing can function pretty well when the ball bearings could not function as well due to its distinct design and efficiency.
There are two different types of spherical roller bearings.
They have an asymmetrical barrel-shaped roller, which allows them to adjust well to a higher load and speed. This bearing’s primary function is to ensure continuous alignment and a higher thrust capacity. These bearings also produce a smaller fraction in terms of production and design.
These bearings may respond well to significant radial loads. Since they are barrel-shaped in terms of design, they can withstand any angular errors and misalignments that may occur in the case of heavy-duty machinery because of higher load. Regarding the actual application, they can withstand the circumstances of shaft and housing misalignment, enabling parallelism without the risk of mistakes and breakdown.
Standard spherical roller bearings are used in a significant amount of papermaking equipment (Paper Industry & Bearings) because of their capacity to support the locating side of various rolls and cylinders of paper machines with significant radial and axial stresses.The bearings, which are made to allow shaft and housing misalignment, are perfect for machines with bearings located in different housings that are far apart. They can frequently be applied to the non-locating side of paper mills.
Since its production we have worked to refine its design and provide knowledgeable advice on bearing selection, mounting, and lubrication.
The most recent spherical roller bearing generation by ZNL offers an exceptional balance of hardness and toughness for a longer service life thanks to high-quality steel and an upgraded heat treatment procedure.
Specific variations can be employed for several peculiar or difficult operation conditions:
When compared to its rivals, such as Ball Bearings, whose applications and operational efficiency are constrained, ZNL Spherical Bearings do offer larger advantages. Spherical roller bearings are frequently employed in high-performance and heavy-duty applications because of their exceptional build quality, resistance, and design. Below given are few key points to ponder:
Spherical roller bearings have a self-aligning feature that allows them to do so while they are in use. It is possible to centre the inner race exactly on the outside race by adjusting it. No specialised equipment is needed for this technique, and the bearing is made to keep its state.
Low Bearing Diameter: Compared to other types of ball bearings, spherical rollers require a lower bearing diameter. For instance, you only need 40 mm between your inner and outer races when using an 80 mm bearing.
High Load Capacity: Compared to other bearings, spherical roller bearings are made to withstand higher load capacities. Additionally, they operate better under challenging environments like vibration or temperature changes.
Continuous Alignment: Throughout the duration of the bearing’s life, spherical roller bearings keep their alignment. Spherical roller bearings can continue to function without any maintenance, in contrast to tapered roller bearings that need to be adjusted after each usage.
Extremely Smooth Operation: Because of their distinctive design, spherical roller bearings offer exceptionally smooth operation. They are made to operate smoothly in any type of machine or equipment by delivering the maximum amount of efficiency.
Simple Maintenance: In comparison to other bearing types, spherical roller bearings require very little maintenance.
Application In Heavy Duty Operations: Spherical roller bearings are frequently utilized in situations where heavy-duty operation is required because they are ideal for heavy-duty applications. These include tools for moving soil, tools for mining, tools for industry, tools for construction, ships, windmills, and so forth.
When the load you need to handle surpasses the load rating of other types of bearings, such as ball bearings, you can utilise spherical roller bearings. Two rows of rolling elements in the outer ring are spaced apart by a radial gap. Both ends of these rolling components make contact with the inner racing surface. The rolling elements can move freely within the radial gap because there isn’t a separate cage or retainer. They will always be aligned on their axis of rotation when the spherical roller rotates, therefore no further alignment technique is needed.
Every bearing is under pressure to operate at faster speeds and with heavier loads than ever before because of the competitive, cost-cutting character of the global business environment. This is especially clear in the demanding surroundings and work schedules of mining and quarrying. Our bearings use highly durable machined brass cages to provide the internal damping and robustness that these applications demand. Users can have faith in the ZNL product and service thanks to good availability and a stellar field reputation. To satisfy particular needs, large spherical roller bearings for crushers and mills can be offered in alternate materials. Here, the expertise of specialised ZNL engineers can offer suitable technologies that lead to affordable solutions.
For some of the most challenging applications encountered in paper mills, ZNL offers market-leading technology. ZNL spherical roller bearings with lubricant are used at the wet end of paper machines to improve reliability without the need for constant grease purging of the bearings to remove the water. The physical barrier offers a very affordable, dependable bearing solution when combined with the long lubricant life. Typically, condition monitoring allows for tracking the development of fatigue spalling and planning a machine stoppage. Ring fractures, on the other hand, provide a sudden and unforeseen problem that results in severe output loss and unanticipated downtime. ZNL bearings offer outstanding dependability and safety from unforeseen costs by essentially eliminating this issue.