Different types of Bearings used in Mechanical Applications

Published by-

1) AAYUSH SURAWAR.

2) SAMARTH TAKBHATE.

3) DEVASHISH TAMBADE.

4) UMESH WANARE.

5) CHINTAN VORA.         

              A bearing is a common machinery component that’s used to regulate the motion and reduce the friction of a moving part. It restricts relative movement to reduce the load placed on the part and the machine. In fact, the word “bearing” is a combination of the words “to bear,” reflecting the component’s ability to bear loads. But there are different types of bearings, including roller bearings , ball bearings , plain bearings , fluid bearings , Magnetic bearings.

 

What Is the Purpose of Bearings?

         The main purpose of bearings is to prevent direct metal to metal contact between two elements that are in relative motion. This prevents friction, heat generation and ultimately, the wear and tear of parts. It also reduces energy consumption as sliding motion is replaced with low friction rolling.

They also transmit the load of the rotating element to the housing. This load may be radial, axial, or a combination of both. A bearing also restricts freedom of movement of moving parts to predefined directions.

Roller Bearings :

Roller bearings - also known as rolling-element bearings.

Roller bearings can handle higher loads than conventional ball bearings, their applications are generally limited to low-speed operations. Many types of roller bearings are self-aligning, and are easily able to overcome misalignment and mounting issues - cutting down on maintenance, repair, and labor needs

However, rolling bearings transmit loads using cylinder rolling elements to maintain the separation between moving parts of the bearing.

These versatile bearings can contain single or multiple rows of rolling elements; multiple rows can significantly improve radial load capacity. Also, the use of different roller shapes can further reduce friction and support both radial and axial loads.

Rolling bearings support and guide rotating or oscillating machine elements – such as shafts, axles or wheels – and transfer loads between machine components. They provide high precision and low friction and therefore enable high rotational speeds while reducing noise, heat, energy consumption and wear. Rolling bearings are cost-effective and exchangeable machine elements that typically follow national or international dimension standards.

Advantages of roller bearings :

1. the friction resistance and the power consumption are small, the mechanical efficiency is high, and is easy to start.

2. size standardization, interchangeability , easy to install and disassemble,easy to repair.

3. The structure is compact, the weight is light, and the axial size is narrower.
4. High precision, large load and long service life

Disadvantages of roller bearings :

1. The noise is great.
2. The structure of the bearing seat is complex.
3. The cost is high.
4. Even the bearings are lubricated well, installed correctly, well sealed , and the operation is normal, they will eventually fail because of the fatigue of the rolling contact surface

 

 

Following are some type of roller bearings:

1)   Cylindrical Roller Bearings :

These are the simplest of the roller bearings family. These bearings can face the challenges of heavy radial loading and high speed. They also offer excellent stiffness, axial load transmission, low friction, and a long service duration

In bearings of this type, the cylindrical rollers are in linear contact with the raceways. They have a high radial load capacity and are suitable for high speeds.

Some cylindrical roller bearings have no ribs on either the inner or outer ring, so the rings can move axially relative to each other. These can be used as free-end bearings. Cylindrical roller bearings, in which either the inner or outer rings has two ribs and the other ring has one, are capable of taking some axial load in one direction Double-row cylindrical roller bearings have high radial rigidity and are used primarily for precision machine tools.

2)    Spherical Roller Bearings :

Spherical Roller Bearings are designed to work in applications where severe misalignment exists whether from mounting or shaft deflection and with relatively heavy radial loads and some axial loads in either direction. They are also extremely resistant to shock loads and their self-aligning feature allows full capacity loading despite shaft deflection.

They are very similar in purpose to Self-Aligning Double Row Ball Bearings, except the Spherical Roller Bearings are designed to be more robust by carry heavier loads but at lower maximum speeds. These bearings have barrel-shaped rollers between the inner ring, which has two raceways, and the outer ring which has one spherical raceway.

 They are self-aligning because the center of curvature of the outer ring raceway surface coincides with the bearing axis.

3)   Tapered Roller Bearings:

The tapered roller bearing contains sections of a cone as a load-carrying element. These rollers fit between the two races that are also sections of a hollow cone. If the races and the axes of rollers were extended, they would all meet at a common point.

Tapered roller bearings are designed to handle higher axial loads besides radial loads. The larger the half-angle of this common cone, the more axial load it can sustain. Thus they work as thrust bearings as well as radial load bearings.

4)   Needle Roller Bearings:

Needle roller bearing is a special type of roller bearings that has cylindrical rollers that resemble needles because of their small diameter.

Normally, the length of rollers in roller bearings is only slightly more than its diameter. When it comes to needle bearing, the length of rollers exceeds their diameter by at least four times.

As needle bearings have a smaller diameter, more rollers can be fit in the same space which increases the surface area in contact with the races. Thus, they are capable of handling high loads. The small size can also prove helpful in applications where space is limited as they require smaller clearances between the axle and the housing.

Needle bearings are used in automobile components such as transmission and rocker arm pivots. They are also used in compressors and pumps.

When to Use Roller Bearings?

Roller bearings are the most common alternative to ball bearings. So let’s determine what kind of working conditions are best suited for this type of bearing.

1.     Heavy loads. Roller bearings provide a considerably larger area of contact, distributing the load more evenly. Thus, they are less prone to failure and can withstand high forces.

2.     Lower speeds. This, again, comes down to the contact area. There is more friction which can result in higher temperature generation and quicker wear.

 

Ball Bearings :

 

Ball bearings are one of the most common types of bearing classes used. It consists of a row of balls as rolling elements. 

A ball bearing is a type of rolling element bearing that uses balls to maintain the separation between the bearing races.

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.

Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.

 

Advantages of ball bearings:

1) Good wear resistance.

2) Do not need much lubrication.

3) Provide low friction, thus little energy loss.

4) Long service life.

5) Easy to replace.

6) Small general dimensions.

7) Comparatively cheap.

8) Can handle thrust loads.

Disadvantages of ball bearings:

1) May break due to shocks.

2) Can be quite loud.

3) Cannot handle large weights.

       Followings are some types of ball bearings :

     1) Deep Groove Ball Bearings:

        This is the most widely used ball bearing type. Trapped between the two races is a ring of balls that transmit the load and allows rotational motion between the two races. The balls are held in place by a retainer.

·         They have very low rolling friction and are optimized for low noise and low vibration. This makes them ideal for high-speed applications.

·         They are comparatively easy to install and require minimal maintenance. Care must be taken during installation to prevent denting of the races as they have to be pushfit onto shafts.

 2) Angular Contact Ball Bearings :

Angular contact ball bearings have inner and outer ring raceways that are displaced relative to each other in the direction of the bearing axis. This means that these bearings are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.

Due to the shift in the inner and outer races, the axial load can be transferred through the bearing to the housing. This bearing is suitable for applications where rigid axial guidance is required.

Angular contact bearings are widely used in agricultural equipment, automobiles, gearboxes, pumps, and other high-speed applications

3) Thrust Ball Bearings:

Thrust ball bearings are a special type of ball bearings designed specifically for axial loads. They cannot sustain radial loads at all.

Thrust ball bearings exhibit low noise, smooth operation and are capable of high-speed applications.

They are available as single direction or double direction bearings and the selection relies on whether the load is unidirectional or bidirectional.

When to Use Ball Bearings?

So let’s outline some of the working conditions that may require a ball bearing.

1.   Thrust loads are present. Ball bearings’ design makes them capable of withstanding axial loads.

2.   No heavy loads. Due to having ball-shaped rolling elements, the bearings concentrate all the force onto a few points of contact. This can result in early failure with high loads.

3.   High speeds. The ball bearing’s small point of contact also means less friction. So there is less resistance to overcome and thus it is easier to achieve high speeds with these types of bearings.

Plain Bearings:

                The most basic type, plain bearings consist of a flat surface without any balls or rollers. Furniture drawers, for example, often have plain bearings on which the individual drawers glide out and back in. Plain bearings like flat wheels, and like other bearings, are placed between two surfaces to reduce friction.

Fluid Bearings:

                Fluid bearings are designed to take the load off a moving part while also reducing friction, but unlike the other bearings previously mentioned, they don’t contain moving balls or rolling elements. Instead, they contain liquid between The fluid creates a thin layer to which the moving part is exposed, allowing it to bear the load. Most fluid bearings contain water or oil, both of which are effective at reducing friction.

Fluid bearings are classified into two types: hydrostatic and hydrodynamic bearings

1) Hydrostatic Bearings:

In this type, an externally pressurised fluid is forced between two elements that are in relative motion. The pressurised fluid forms a wedge between the moving parts and keeps them apart. The fluid layer may be very thin but as long as there is no direct contact, there will not be any wear.

The fluid is circulated by means of a pump. The exit orifice diameter may be adjustable to ensure the fluid is always under pressure at all shaft speeds and loads. Thus, precise gap control is possible.

 

2) Hydrodynamic Bearings:

This type of bearing utilises the motion of the journal to force the fluid between the shaft and the housing. The journal motion sucks the lubricating fluid between the moving parts creating a constant wedge.

This, however means that during start-stop as well as at low loads and speeds, the wedge formation may not be good enough to prevent wear. Only at designed speeds will the system work exactly as needed

 

 

Magnetic Bearings :

 

                  In addition to fluid bearings, magnetic bearings are another unique alternative to traditional rolling-style bearings. Featuring powerful magnets, they use magnetism to lift and bear loads without creating direct contact. Magnetic bearings literally levitate moving parts into the air, allowing for little or no friction. Of course, they only work when used in conjunction with ferromagnetic metals.