Specialised lubricants need to be carefully chosen to optimise equipment performance, lifespan, and profitability.

Today?s earthmovers are big beasts: a typical item of underground mining equipment can generate 650 HP and boast a lifting capacity of 90,000 pounds (41 tonnes). The powershift transmissions of such machines require specialised lubricants to minimise repairs and maintenance, and to maximise performance and equipment life.

Yet barely 20 years ago, specialised lubricants for powershift transmissions were a novelty. The regular engine oils often used were a severe limit on capacity and efficiency; problems included poor friction performance and marginal anti-wear protection, as well as issues with oxidation, seals, and sludge control. These shortcomings contributed to equipment failure and higher maintenance costs resulting in lower profitability.

In the late 80s and early 90s, equipment manufacturers, oil companies and lubricant engineers came together to develop specific oils to meet the demands of the new machinery.

Some of the benefits of this dedicated fluid technology have included:

? Improved overall lubrication to protect against wear, micropitting, fatigue, and eventual equipment failure resulting from metal-to-metal contact;
? Improved frictional stability to enhance clutch life and promote efficiency when moving heavy loads on inclines;
? Complete compatibility of lubricant and machinery, to combat negative effects on elastomers in rings and seals, preventing fluid leaks;
? Oxidation and thermal stability, to ensure that fluid performance is maintained at temperature extremes of hot and cold;
? Sludge control and cleanliness, reducing the blockages that prevent fluids reaching where they are needed;
? Prevention of foaming and consequent metal-to-metal contact damage, including the dangers of fluid overflow;
? Hydraulic pump protection against high pressures;
? Improved friction plate performance and reduced brake chatter resulting in better wet brake control;
? Sustained film thickness to provide anti-wear and extreme pressure protection for gears;
? Shear stability control to maintain viscosity, thus providing start-up wear protection

Today, owners of mining equipment can choose between two basic types of specialised fluids:

? Single grade, which requires a seasonal fluid change ? SAE 30 or 50 for spring and summer, and SAE 10 when the temperature drops below 20?F/-7?C. A cold start with the wrong fluid can result in blown transmission seals.
? Multigrade, which operates correctly in all weather conditions and offers more efficient operation than single grade over an expanded temperature range. Multigrades also allow for lower friction losses, meaning improved fuel efficiency, and have outstanding shear stability.

Viscosity is a critical parameter in ensuring the proper operation of today?s powershift transmissions. Those with advanced electronic controls require the low-temperature performance of SAE 10W, while final drive gears need the film thickness of an SAE 30. Film thickness is critical to maximising gear and bearing life, while low-temperature fluidity is vital for pump performance and for optimal shift quality when equipment operating temperatures fall.

The future

Changing emission standards will drive the future of equipment design. The Tier IV engine emission standards, set for phased introduction in 2014, will mean changes in drivetrain design that will increase component temperatures and lead to a loss in overall efficiency of up to five percent. Smaller sump sizes will also increase fluid demands as less fluid is required to provide better protection. New specialised fluids will be needed to mitigate the impact of changing equipment design, and as a result, OEMs will need to consider the introduction of multigrades in their next generation of fluid specifications, not only with the objective of improving fuel economy but also providing greater cleanliness and balancing the need for equipment durability.

Developing countries such as China and India are now started using high-performance lubricants too; more availability will be needed to meet this demand, as well as information provision for owners and fleet operators on how the right lubricant can improve the performance and life expectancy of their mining equipment.

No single lubricant solution is available to suit all mining equipment applications and, unlike engine oils, there are no industry-wide standards. For powershift transmissions, fluid specifications, including maintenance and filter replacement intervals and viscosity grade, come from manufacturer recommendations. With this in mind, and the ever-increasing costs of buying and maintaining equipment, lubricants need to be carefully chosen to optimise equipment performance, lifespan, and profitability. After all, with increased power, and a longer lifespan, earthmoving equipment can, quite simply, move more earth.

It?s clear that designing vehicles for the off-highway industry is becoming more challenging with global emission standards changing and end-user needs expanding. Doing more work under more stringent duty cycles with less impact on the environment requires a dedicated commitment to innovation at the OEM and tier supplier level.

To help you stay ahead in this changing industry, Lubrizol is partnering with SAE to offer a free online event at the 2012 Global
Virtual Summit. By utilising experts from key off-highway companies, this webcast will address global emission standards, future hardware designs based on performance, and the implications at the component level for these design innovations. Webcast attendees will be able to interact with the experts during the programme?s live Q&A segment.

(http://vshow.on24.com/vshow/drivetrain/registration/3293)