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Bearings fulfill a number of important functions, starting with their ability to reduce friction. Other primary functions include supporting a load, promoting the efficient transmission of power and ensuring alignment is maintained. These characteristics enable machinery to run for a longer operating period at a more efficient rate. Net result is that bearings enable machinery to consume less energy.

Kaustubh V Phadtare, Managing Director, Kavitsu Group of Industries elaborates, 'Construction equipment use a variety of bearings, right from three-row roller bearings to smaller single-row ball bearings. These are chosen based on the load ratings of the vehicles and whether they are dynamic or stationary. These bearings can be externally geared or internally geared, with a driving pinion shaft.'

According to Sanjay Koul, Chairman & Managing Director, Timken India Ltd, among the construction equipment, there is a huge demand for backhoe loaders owing to the flexibility and compactness of the machine. 'Anti-friction bearings like tapered roller bearings are used for carrying heavy axial and radial load in wheel-ends or tracks. Spherical roller bearings and cylindrical roller bearings are largely seen in transmission, main shaft and other drive applications. Friction bearings (also referred as bush or plain bearings) are used in mostly in articulated joints, linkages and vehicle suspensions.'

Pulkit Khemka, Vice President, Pensol Industries Ltd says, 'Bearings are useful in facilitating the efficient operation of machinery. They can range in size from a large diameter wind turbine blade pitch bearing to a series of thin bearings. Two of the main types are journal bearings and rolling element bearings.'

Supporting equipment life
According to Phadtare, bearings are an essential part of construction equipment as they help to reduce friction while rotating the surfaces. He adds, 'Choosing the right bearing depending on the load rating and working cycle is very important, as wrong selection can be catastrophic. Also, proper and timely maintenance ensures that the bearing lasts for a longer period. Manufacturers must also follow strict quality checks so that there is no premature failure in the bearings.'

Says Koul, 'Bearings are critical part of the equipment as it keeps the relative parts in motion while transferring the load. Hence the design, quality and manufacturing of bearing will determine impact/heavy loads are transmitted with less friction. A right bearing selection, correct installation and regular maintenance ultimately results into prolonged service of equipment.'

Market trends
Says Koul, 'In India, anti-friction bearing market is estimated at around Rs 9,500 crore which is growing at an average of 7-8 per cent CAGR over last three years and is expected to grow at similar pace. Apart from business cyclicality, government policies like change in emission norms, replacement of ageing fleet may impact the growth rates.

Product innovations
Phadtare explains, 'Kavitsu provides solutions for every range of the product comprised in the construction equipment portfolio. The major products include bearings for excavators, crawlers, tower cranes, telescopic cranes, truck-mounted cranes, bridge repair cranes and so on. Also, smaller bearings are supplied for bull dozers and road rollers.

Koul elaborates on Timken's product range, ' Timken has developed new range of High performance spherical roller bearings which has an innovative cage design for better lubrication flow, keeping the bearing run cooler and longer life over competition. Further, the arrangement gives an extra space to accommodate larger roller size hence higher load carrying capacity within the same envelope dimensions. Timken has wide range of anti-friction bearing products and further expanded into mechanical power transmission products portfolio. In 2014, Timken acquired centralised lubrication company, Interlube, and recently acquired PTTech which manufactures engineered clutches and brakes, and Torsion Control Products, manufacturer of engineered torsional couplings for mining and similar applications. Timken is committed to provide customer solution and service under the same brand promise.'

Koul further explains on the rich history of his company in bearings, 'Timken invented tapered roller bearings in 1899 and with 115 years of experience, we have got expertise on friction management. Working closely with OEMs on application development, Timken has further built on: 1) special profiles on the bearings 2) engineered surfaces, and 3) controlled heat treatment to name few approaches. These specially designed bearings meet harsh operating conditions involving debris, water, sludge, slurry at the same time, can withstand intermittent and impact loads. As this is a demanding segment, the technology is valued. For Timken, as the application gets more demanding, our solutions augments the equipment. Timken is all about reliability and fit and forget where others dare not venture.'

Role of lubrication
Lubrication is essential to proper operation of ball and roller bearings. A proper lubricant will reduce friction between the internal sliding surfaces of the bearings components and reduce or prevent metal-to-metal contact of the rolling elements with their raceways. Proper lubrication reduces wear and prevents corrosion, ensuring long service lives for bearings. Lubrication, especially circulating oil, will also remove heat from the bearing.

There are two basic types of bearing lubricants readily available:
Oil and grease. Oil is fairly simple to understand being a free-flowing liquid, while grease is a little more complex. In order to be a lubricant, all greases have oil that is entrained in a thickened base. It is this base that gives the impression that grease is a more viscous type of oil; however, it is the oil in the grease that does the actual lubricating. Each type of lubricant has its own advantages and disadvantages and is selected by the nature of the application.

Says Khemka, 'Lubrication is an important factor in ensuring that bearings operate in an effective manner. Besides reducing friction, lubricant is needed to provide elastohydrodynamic lubrication for all true rolling contacts and to lubricate sliding contacts (such as cages, flanges, etc) within a bearing.

J Ramesh, Executive Director, Tide Water Oil Company (India) Ltd, explains, 'Lubrication in bearings is primarily to lubricate the sliding contacts between the retainer, rings, rolling elements and other components, and also to lubricate the rolling contacts between the raceways and rolling elements elastohydrodynamically. While the secondary functions are to protect the highly finished surfaces from corrosion and help seal against foreign matter.'

He further adds on lubrication in construction, mining and material handling equipment, 'The working conditions in construction and mining is different from material handling and such applications. Severe shock loads are encountered in construction/mining applications. Therefore, a grease with high EP property is required.'

Tide Water Oil Company (India) offers various grease ranges for bearings which include Veedol Alithex 20, Veedol Alithex EPW, Veedol Alicom 20, and Calcium sulphonate grease. Khemka says, 'Grease used in mining and construction equipment must meet the challenging performance requirements of massive equipment used in extremely harsh conditions. Operators simply cannot afford maintenance issues that sideline expensive machinery and mobile units. Pensol high-performance grease provides the critical equipment protection operators and application need.'

He elaborates on the range of grease for construction and mining applications. Pensol Lithonex EPL greases and Pensol Arcom 3M are recommended by Pensol Lubricants for use in construction and mining sector applications. Lithonex EPL is recommended by Pensol for use in highly loaded plain and anti-friction bearings and other applications.

Arcom 3M grease, which has 3 per cent molybdenum disulphide and high-temperature thickener system, will provide extraordinary performance.

Pensol Lithonex EPL Series products are a family of extra high performance extreme-pressure greases. These products are manufactured with a proprietary high-temperature, lithium thickener system. They exhibit excellent resistance to softening under severe working conditions, provide good adhesion and cohesion. An extreme-pressure additive provides exceptional protection against wear and shock loads, while additional additives enhance resistance to high-temperature oxidation and protection against rust.

The concept of lubrication in bearings is changing gradually. Ramesh comments, 'Earlier, any grease was used for most of the bearing applications. But now selecting a bearing lubricant is more specific depending on the application and working conditions.' He adds, 'Some of the latest trends are, grease for long drain intervals, use of nano additives in grease, life time grease fill in some bearing applications, use of bio-degradable greases, etc.'

Says Khemka, 'Bearings and lubricants continue to become more advanced, allowing for longer bearing life and increased customisation for specific applications. The right lubricant is critical to achieving optimal efficiency.'

According to Khemka, lubricating grease specifications merely stipulate the basic characteristics, such as type of thickener, viscosity of the liquid phase, minimum drop-point, penetration value or consistency. He elaborates, 'Grease selection depends on the type of bearing to be lubricated (ball, roller, taper roller or needle bearing), the working conditions (temperature, rpm) and the method of lubrication.

There are some characteristics common to all greases for anti-friction bearings. The grease must be mechanically stable. Grease that breaks, becomes very soft, after 60 double strokes in a grease worker, is not suitable for anti-friction bearings. Good greases show very little change even after 100,000 double strokes in a grease worker.' On the selection procedure, Khemka says, 'Greases with a smooth, buttery structure are always preferable. Another basic requirement is colloidal stability over a very wide temperature range. Greases can only be used in slideways, where the sliding components move sporadically. The distance traversed is minute, intervals among lubrication long and contamination of the surfaces and their surrounding does not cause problems. This restricts the field of application mainly to slide shoes for construction machines, railway transport, forges, press shops, and similar sites. Normal calcium greases with graphite at consistencies 2-4 can be used. High-quality greases with long service lives, such as lithium grease made from low pour-point oil and containing a small amount of a solid lubricant such as MoS2, with a consistency of 4, are preferred for one-shot lubrication of the sliding surfaces in devices such as cameras and optical instruments.'

Opportunities and challenges
According to Koul, construction equipment largely depends on the infrastructure development and housing demand. The present government has allocated higher expenditure and ambitious programmes to build roads and bridges, and sops to low budget housing sector provide growth opportunities.

On challenges, Koul says, 'Uptime of any construction equipment is essential due to high capital costs involved and expected performance.

As supposed to work under harsh environment and impact loads, a lot depends on operation and maintenance practice. Equipment downtime due to bearings can be largely attributed to improper installation, inadequate lubrication, sealing and in-correct bearing selection for the application. Timken service and engineering team solves such problem on the field with custom-designed solution and support.

Oulook
Emerging markets with infrastructure needs continue to accelerate the growth of construction equipment manufacturing, which in-turn drives the bearing market in construction segment.

Koul is positive on the future of bearings industry. He says, 'As per the estimates of Off-Highway Research, the CE industry in India is expected to grow from 54,970 units to 72,000 units by 2019 which is CAGR of 9 per cent. Along with infrastructure growth and government's Make in India initiative, we are seeing an increase in local engineering support for upgrades and manufacturing. We are partnering with key OEMs for their local and export demand on a continual basis. Timken has further invested in new cylindrical roller bearing line at Chennai facility in this direction.'

With the construction and mining equipment market is forward looking on account of the increased construction activity, bearings will see better movement in the years to come.

BEARING LUBRICATION: KEY CONCEPTS

• Advancements in materials have extended the operating life of bearings, even under severe operating conditions.
• New additives enable bearing lubricants to be designed and developed for specific applications.
• Future bearing materials will boost performance and improve efficiency.
• Choosing the right bearing depending on the load rating and working cycle is very important.'

- Sudheer Vathiyath