Seemingly simple and purely mechanical in nature, bearings may not evoke much interest in a machine with numerous operating parts of complex shapes and sizes. However, it is these simple looking components of a machine that amounts to good numbers. The term bearing is derived from the verb to bear. To be precise, it is a machine element that allows one part to bear (to support) another. Though purely mechanical in form, bearings are highly engineered and precision-made components that enable an equipment to move at good speeds and carry remarkable loads with ease and efficiency. Used to enable rotational or linear movement, while reducing friction and handling stress.

Bearings are one of the most critical components of a machine or equipment. Bearings are found in a forklift, tractor, backhoe loader or an excavator, where one part is set in motion in relation to the other. For example, a camshaft and crankshaft in an engine, various shafts in a transmission, or axles shafts. Supporting two types of motion-linear or rotary-bearings could be divided into two principal varieties: contact and non-contact. Bearings are either of the ball bearing types, roller bearing types, ball thrust bearing types, tapered roller bearing types, or specialised bearing types, which includes magnetic bearings and giant roller bearings. For a tractor or a construction equipment, which operates in harsh environment with risks like bearing contamination from dust, mud and huge loads, certain degree of ruggedness is called for. This makes bearings used in off-highway equipment different from those that find use in passenger vehicles. Bearings in off-highway equipment are engineered to deliver high performance by employing leading edge materials, high capacity cylindrical roller bearings with higher number of rollers and a one piece cage. Bearings made from innovative material and heat treatment technology, sealed deep groove ball bearing capable of carrying radial and axial loads in either direction, and needle roller bearings with M-type and uncontrolled contour rollers. As Vinod Goel, Director - Marketing, ARB Bearings, says, "The use of taper roller bearings in the agricultural and construction equipment are dictated by their intended application and use." He further adds, "The type of bearings that find use in the off-highway equipment include ball bearings, taper roller bearings and cylindrical roller bearings."

Reliability in harsh operating conditions

In case of agricultural machinery like tractors and harvestors, bearings should offer a long service life while operating in harsh environments of mud, water, and heavy loads, while ensuring sufficient resistance against contamination from foreign debris. According to Rohit Saboo, CEO and President, National Engineering Industries (NEI), "The challenge is to protect the bearing from friction wear and adverse environmental conditions such as moisture, soil dust, sand and marshy land."

A bearing for agriculture equipment application from NSK, for example, is constructed with a special seal-lip that allows the inflow of lubricating oil while preventing the entry of foreign matter. Finding use in transmissions, the single direction and double direction thrust ball bearings can accommodate initial misalignment in an assembly. They often employ high quality ultra clean steel and seating rings.

With bearing manufacturers like Timken, SKF, NEI, NRB, ABC, ARB, GGB and Igus operating and catering to a variety of industries, bearings are set to play a crucial role in the way an equipment is designed and manufactured. As off-highway equipment designers and manufacturers strive to come up with compact, lighter and more efficient machines, bearing manufacturers are increasingly playing the role of a technology partner. Rather than simply supplying bearings, bearing specialists like SKF have come to offer solutions that grow around a bearing to arrive at a sub-assembly that enhances efficiency.

Long life bearings for off-highway applications

SKF has launched a new range of Extended Life spherical plain bearings and rod ends. Aimed primarily at applications in the farm, forestry and construction sectors, these are virtually maintenance-free, which means that they do not need to be relubricated. A part of the SKF BeyondZero portfolio, the Extended Life spherical plain bearings help reduce the cost of ownership and reduce environmental impact because they last longer and do not require relubrication. According to Juergen Scholer, Product Manager, SKF Plain Bearings, "The tribological system, which includes special surface treatments, grease and seals, combined with the internal geometry of the bearing is what makes these bearings so robust and energy efficient.

Furthermore, SKF Extended Life plain bearings are phosphated and undergo treatment to practically eliminate corrosion and reduce wear. Then the bearings are greased and sealed." SKFs maintenance-free solution for backhoe loader kingpin applications (steering linkage) features a spherical plain bearing with a specially developed seal. The bearing requires no lubricant and is fully interchangeable with steel-on-steel plain bearings.

Two planet-bearing solutions from SKF-a cylindrical roller bearing and a CARB toroidal roller bearing-can be be integrated into a planet pinion with a compact design. Both types offer a high carrying capacity that facilitates more efficient planetary gearbox functionality and an overall cost-effective solution. The easy mounting of the cylindrical roller bearing minimises the risk of incorrect mounting, resulting in increased productivity and overall reliability. The CARB toroidal roller bearing provides a strong influence on the gearboxs performance. Its insensitivity to misalignment helps reduce sun gear pitting failure, thus optimising performance and lifetime of the full planetary system. Insulated bearings, as part of hybrid bearings with ceramic rolling elements, support electrically motorised wheel drives, performing under high temperatures, shocks and vibrations and stray electric currents. Vibration resistant bearings (Explorer spherical roller bearings, VA 405; Explorer spherical roller bearings with PTFE-coated bore, VA 406; and Explorer cylindrical roller bearings) in road rollers that use vibrating drums to boost compaction efficiency help ensure drum performance and reliability.

Sanjay Koul, Managing Director and Director of Manufacturing, Timken India, is of the opinion that technology develops everyday, and provides us with new and different products, one better than the other. "Friction management products increase operational efficiency to fuel and energy saving." He elaborates, "Timken recently expanded its tapered roller bearing manufacturing capacity in India by approximately 2.4 million races of up to 8-inch tapered roller bearings per annum in view of the growing demand in construction, off-highway vehicles, heavy trucks and other commercial transportation systems, both in India and globally." Coming in various shapes or sizes, even various types, bearings are an intrinsic part of a machine. Their use does not end with them packaged into a machine. The life of a bearing is clearly dependent on many factors apart from its construction and the ability to keep out foreign matter, may it be dust, chemicals or other elements. However good the ability of the bearings and its sealing elements may be, bearings have a life period. When the time arrives to replace a worn out bearing, the aftermarket and associated services come into the picture. With heavy equipment like excavators and tractors, manufacturers like SKF are known to offer annual maintenance contracts as well as preventive maintenance services.

Importance of maintenance services

"A good quality bearing from a reputed manufacturer does not come cheap. In fact bearings in heavy equipment and tractors can burn a hole in the customers pocket, especially in case of units where bearings are a part of a sub-assembly," opines an industry expert. For example, often, it is the complete hub unit that may be needed to replace, escalating the cost further. Some critical bearings like the ones that find use in the engines or the drivelines, including the transmission and transfer case could be quite costly to replace too. Their cause of failure is often attributed to the lack of proper and irregular service, and failure of associated parts and seals. A front hub bearing (big) of a backhoe loader could cost between Rs 250 to Rs 600 depending on the brand and quality.

A spare part stockist who spoke to EQUIPMENT INDIA, informed that a Rajkot-made hub bearing (big) will cost Rs 450. The quality of this bearing, he stressed, would be equivalent to that offered by the branded bearings. Touching upon the availability to pirated bearings, he advised that it would be best to seek branded bearings from the distributors of those companies. A planetary gear bearing could cost between Rs 450 and Rs 800. A crankcase bearing could cost as much as Rs 2,500.

High growth potential

If an industry expert is to be believed, the organised bearing market in India accounts for a little over 60 per cent. The rest of the market is made up by the unorganised sector, which also includes imported bearings offered by various stockists of equipment spares and retailers. The distributors of brands like SKF and Timken, as well as those who deal in imported and less-branded bearings agree upon the fact that bearings find steady demand and make one of the high growth potential spares among their inventory. In fact, the slowdown in the equipment sector over the last two years has lead to a spike in the demand for bearings in the aftermarket as operators look at keeping their machine operational for a longer period of time. The current market for bearings in India is estimated to be over Rs 85 billion. The market is supported by manufacturers that produce small and medium bearings mainly in five categories ? ball bearings, cylindrical roller bearings, taper roller bearings, spherical roller bearings and needle roller bearings. There are producers of specialised bearings too, however small in terms of market size and capitalisation. Combine specialised bearing applications with the standard types, and the types and sizes of bearings in demand would amount to over 40,000 different types. May it be a forklift or the mighty dump truck from Caterpillar, a bearing, though not as interesting or inspiring as the tiny transistor in an electronic circuit, is definitely as important. The way the transistor amplifies current, and regulates its travel across the gates to ensure smooth function of an appliance, a bearing ensures reliable and smooth transfer of torque and motion across two surfaces. Often under arduous conditions that call for high levels of endurance.

"It is essential to follow the standards." - Vinod Goel, Director ? Marketing, ARB Bearings

What is the difference between bearings used in agriculture and construction equipment over automobiles?
There is not much difference between the bearings that find use in agriculture or construction equipment when compared to those used in automobiles. Difference is rather limited to their categorisation, which is dictated by their intended application. The nature of application of the bearings also dictates their size and load carrying capacity. For example, the use of taper roller bearings in agriculture and construction equipment is dictated by their use, the load carrying capacity, etc.

What type of bearings are used in off-highway and agri equipment?
Bearings that used in off-highway equipment include ball bearings, taper roller bearings, cylindrical roller bearings etc.

What is the performance of these bearings?
As mentioned earlier, the design of the bearings is dictated by the application they are intended to serve. In case of off-highway and agri equipment applications, the bearings are designed to withstand heavy load; are often bigger is size than automotive bearings to withstand the higher loads. In terms of design they may not be very different. They are designed to help perform under arduous conditions and last long. Tractor bearings for example are made to enjoy a long life. There are bearings that are grease filled to ensure long life.

What is application of bearings in the agri and off-highway equipment?
The nature of application bearings find in agriculture and off-highway equipment are in areas like engine, transmission, axles, etc.

What is the technology involved in the manufacture of such bearings?
Technology in the manufacture of these bearings is not drastically different from those used to make automotive bearings or industrial bearings. It is necessary to understand that the manufacture of bearings is dictated by standards. It is essential to follow the standards. Without deviating from the prescribed standards, technology is facilitating the manufacture OD bearings with close tolerance. Technology is facilitating the ability to seek lower tolerance. Manufacture bearings with a tolerance of between 0 to 10 micron even though the industry accepts a tolerance levels of between 0 to 20 micron.

The range of bearings ARB Bearings offers to the agri and construction equipment sector?
As mentioned above, we offer ball bearings, taper roller bearings, cylindrical roller bearings, etc., depending on the requirement of the manufacturers.

Are new age materials and non-traditional manufacturing techniques leading a change? The manner in which bearings are made has not changed, it is much the same. Also the use of materials has not changed much.

Which are your major clients in agriculture and off-highway equipment space?
We cater to the requirements of small and large manufacturers. In agri equipment , we cater to many companies in the Punjab belt. We cater to Beri Udyog, Dahmesh, Kartar, etc. We cater to tractor manufacturers like HMT and New Holland. We cater to the requirements of JCB through their vendor Hi-Tech.

"Bearings must withstand all types of land and weather conditions." - Rohit Saboo, CEO and President, National Engineering Industries NEI

How different are bearings used in agricultural and construction equipment over automobiles?
All agricultural equipment come under the off-highway segment, and are used for tillage, sowing, harvesting and bailing. In the off-highway segment, the challenge is to protect the bearing from friction wear and adverse environmental conditions such as moisture, soil dust, sand and marshy land. In the automobile sector, the bearings have better road conditions to support their operation. In off-highway and agricultural equipment, depending on the housing, the bearings are grease-filled or oil-lubricated.

What type of bearings find use in off-highway and agricultural equipment?
A wide range of applications in the off-highway segment include the use of roller bearings. The bearing types that typically find application in the off-highway segment include spherical roller bearing, angular contact bearing, taper roller bearing, plummer block bearing and housing units.

Which are the preferred ones among them in performance?
Bearings must withstand all types of land and weather conditions. They should be able to sustain misalignment, shock and vibrations, and adverse conditions of dust and moisture during their operations. Bearings should also be able to meet customer requirement in terms of life, warranty and durability.

What are the applications of bearings in agriculture and off-highway equipment?
Bearings are used in off-highway trucks, tractors, excavators, backhoe loaders, cranes, mowers, cultivators, seeders, harvesters, sprayers, plows, tillers, planters, etc. The bearings find application in components and sub-assemblies such as engine, transmission, wheels, differential, linkages and hinges, plow disc, sprocket, pulley, motor, rotavator, etc.

What is the technology involved in the manufacture of bearings?
The bearings for application in the off-highway segment are specially designed to carry heavy load, minimise friction, and withstand shock and vibration. The technology for manufacturing such bearings is governed by the selection of material, the grinding and special heat treatment process, sealing technology, and lubrication and coating processes.

- Bhushan Mhapralkar