Correct fluid and adherence to proper lubrication regimes is important not only to achieve higher productivity but also to reduce cost of repairs and downtime.

India's 12th Five Year Plan (2012-2017) aims at an eight per cent economic growth and articulates an investment of $1 trillion, part of which is to support major infrastructure development in the country. Many construction projects are under way. With declining availability of manual labour and increasing challenge of meeting project timelines, there are greater demands on construction machinery than ever before. Reliability is therefore of paramount importance.

Correct fluid and adherence to proper lubrication regimes is important not only to achieve higher productivity but also to reduce cost of repairs and downtime. This has high significance as all modern construction machinery means big investment and though the cost of repair is high, the cost of downtime is potentially even higher. For operators, contractual agreements increasingly involve punitive measures or fines for late delivery of projects, so maximum efficiency is vital to them.

The wide variety of construction projects under way across the country involves different types of equipment, from backhoe loaders to graders and compactors to excavators. Some of the larger machines may also drive ancillary equipment such as power tools, so their reliability has become even more important.

During the last 25 years or so, the performance and sophistication of con?struction machinery has increased dramatically. Typically, there have been increases in power, power density and torque with each successive model. This increase in power density generates more heat, raising oil sump temperatures throughout the drivetrain. Transmissions, differentials and final drives are subjected to increasingly higher loads as machines become capable of shifting larger quantities of material and much faster. The surface finish of components, their design and metallurgy have steadily improved but they still require the highest level of lubrication to deliver maximum performance and remain durable.

A key development in the field of off-highway equipment in the last 25 years has been the powershift transmission. For some equipment, such as backhoe loaders, power shifting makes it possible to shift gear even during the process of pushing tons of earth, something that in the days of manual transmissions would have been impossible. Powershift transmissions enable automated shifting of ratios while a vehicle is under load, with no interruption of torque. They are complex, with a wide range of ratios and contain a variety of hardware technology including epicyclic gear sets, wet clutches and brakes, and in the case of infinitely variable transmissions (IVT), a combination of epicyclic gears and hydrostatic drives. They may also incorporate hydraulic actuators which are sensitive to the viscosity and the type of lubricant used.

The first powershift transmissions had to make do with engine oil for function and lubrication as dedicated fluids didn't exist. For convenience, engine oils were used throughout the drivetrain but their performance in that role was severely limited and there were many shortcomings. In powershift transmissions, they provide poor friction, marginal anti-wear, problems with oxidation and oil seals and also poor sludge control. Maintenance costs were unnecessarily high in those days and equipment failure rife, both having an adverse affect on profitability for the equipment owner.

In the late 1980s and early 1990s, major equipment manufacturers, oil companies and additive manufacturers began working together to develop dedicated transmission fluids to meet the demands of the new technology. This took time to evolve and early fluids suffered similar shortcomings as engine oils but these soon began to improve.

Today things have changed considerably. There is no need to use engine oils in powershift transmissions as they will not provide adequate wear protection and satisfactory frictional performance. As engine oils upgrade in specifications, they become even less satisfactory for protecting powershift transmissions and driveline components. The formulation of modern engine oils is driven by the needs of advanced engine designs and the performance in drivelines is not a consideration. The new Tier 4 emissions regulations governing off-highway vehicles, in effect from the beginning of 2011 reinforces the fact that the focus of engine oils has switched more and more to the challenge of engine emissions reduction. Powershift transmissions in modern equipment would not meet the required performance levels if engine oils were used in place of specialised fluids. The result could be slipping wet clutches, higher temperatures causing pump wear, compromised shift response and an increased need for maintenance. Engine oil may actually attack some non-metallic components causing elastomers to become brittle and causing leaks in seals which could lead to increased gear wear and damage. The development of dedicated driveline fluids has brought huge benefits in terms of increased performance and massively increased protection. Here are some of the functions in which a modern, specialised driveline fluid excels in promoting longer equipment life and reducing downtime:

.Frictional stability ensures operating efficiency when moving heavy loads on inclines, supporting metallic and non-metallic materials properly by delivering appropriate frictional properties. This includes the needs of clutches and wet disc brakes, resulting in longer clutch life and elimination of wet brake noise.

.Anti-wear properties protect planetary and helical gears as well as heavily loaded final drive gears against macro-pitting and fatigue.

.Compatibility with elastomers used in rings and seals avoids leaks and doesn't corrode copper alloys.

.Low-temperature Fluidity inhibits wear in cold weather starting and allows easier cold weather operation.

.Oxidation Stability ensures the fluid won't degrade at high temperatures resulting in longer fluid life, particularly in extreme operating conditions.

.Sludge Control prevents lubricant passages from being blocked, resulting in longer equipment life.

.Rust and Corrosion Protection extends equipment life and promotes trouble-free operation.

.Foam Protection prevents fluid loss due to foaming, reducing wear from metal-to-metal contact and protecting the operator from the fire and safety hazards associated with fluid overflow.

.Thermal Stability provides consistent performance under a variety of temperatures.

.Hydraulic Pump Performance pro?tects high-pressure hydraulic systems.

.Lubrication of clutches, wet brakes, vane pumps, planetary gear sets, final drive gears and bearings (metal-to-metal).

.Sustained Film Thickness promotes protection of highly loaded gears and long-term anti-wear protection.

.Shear Stability maintains the viscosity grade over the life of the lubricant and provides wear protection, resulting in no loss of applied pressure that could result in slippage and equipment failure.

It is still a common practice in many areas to use cheap or completely unsui?table lubricant fluid in the driveline of expensive equipment either due to avai?lability issues, perceived higher cost (which in comparison to equipment cost is very nominal) or due to lack of understanding. The average cost of an inappropriate generic fluid amounts to approximately two percent of the average cost of a typical construction machine such as a backhoe loader. In comparison, using the correct specialized fluid undoubtedly can cost more, but that cost is still insignificant when compared to the cost of the equipment, repairs and lost revenue in downtime. Research shows that the majority of equipment outside warranty move to local workshops which tend to use non-specialised or general fluids like TASA fluids (Type A Suffix A) for transmissions, or the outdated API GL-4 fluids for axles, both of which are inadequate for modern off-highway machinery.

Low-price generic fluids are not robust enough, nor do they have the correct specifications to protect gear and transmissions components in high performance and heavy machinery operating in hostile conditions. Typical failures linked to the use of inappropriate fluids are overheated wet clutch plates, bearing failure and gear tooth damage (caused by oil oxidation and thickening), axle noise and so on. Given the use of the correct lubricant, maintaining fluid integrity is still an important consideration. Machines are usually working in dusty conditions so filter condition must be maintained properly to achieve extended equipment life. Although a high quality lubricant can tolerate small quantities of water, excessive amounts reduce its capability to prevent wear and corrosion.

Fluids are available in different viscosity grades and choosing a viscosity grade appropriate to the prevailing ambient temperatures is essential, especially when opting for a single grade fluid. Viscosity is critical for both powershift transmissions and final drive units. Low temperature fluidity is critical to allow smooth pumping and effective operation of hydraulic transmission actuators while final drive gears need an appropriate film thickness for prolonged gear and bearing life.

Monograde fluids normally require a change to suit the season. For example, SAE 30 or SAE 50 is used in summer but in winter, if the temperature drops below -6?C, the fluid should be changed to SAE10W. Using an incorrect grade can have serious consequences. Cold starts in equipment using SAE 30 can result in damage to the transmission seals, lead to higher maintenance costs and lower overall productivity, compared to using the correct grade of fluid.

Multigrade fluids are designed to provide an optimal viscosity across a wider range of climatic conditions. A single fluid can span the equipment's entire operation range, avoiding the need to stock two different grades of fluids or to change the fluid with seasonal changes in ambient temperature. They offer better efficiency than monogrades over an expanded temperature range. Hydraulics benefit as well from multigrades, from cold starts to high-temperature operations because multigrades impose lower parasitic (fluid friction) losses in the transmission, enabling higher efficiency and reduced fuel consumption, thus lowering the cost of operation.

Viscosity specifications for off-highway applications are regulated by the standard SAE J300 whereas viscosity for on-highway equipment is specified under SAE J306. OEMs have also produced application specific fluid specifications which are publicly available, examples being Allison C4 and Caterpillar TO-4. Owners using equipment from either manufacturer should use the fluids specified in their application documents.

Today, no single lubricant is able to cover all the equipment applications, how?ever there is plenty of information avai?lable as to which is the correct fluid for a particular equipment. Operators and owners who ignore this information face a higher level of risk for their equipment. Conversely, by following recommended lubrication regimes, they would minimise failures and equipment down-time, and ultimately boost productivity and profits.