Oiling the Wheels in Off-Highway Vehicles

Off-Highway Vehicles

A major concern for many maintenance engineers is off-highway equipment running low on lubricant. However, they often make a critical error when trying to solve the problem: they over-lubricate. This can be just as damaging as using too little lubricant, as it increases friction, raises temperatures inside the bearing, and can damage the seals.

Things get even worse if the wrong lubricant is applied: equipment performance and lifespan will be reduced, while both maintenance and downtime spiral out of control. It all adds unwanted costs to the balance sheet.

An increasingly popular solution is to fit a centralized automatic lubrication system. This applies a metered volume of lubricant at controlled intervals. Engineers prescribe the most suitable lubricant for the piece of equipment, and the system delivers a precise volume exactly where it is needed, when it is needed.

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This can have a dramatic effect. As well as reducing the amount of lubricant needed, it also saves huge amounts of time. Depending on the machine type, manual lubrication can take around 30 minutes every day. Automatic systems are also more accurate than manual application, delivering lubricant to moving parts more reliably and effectively. They can also be easily retro-fitted to existing systems.

Setting the level

Automatic lubrication systems have proven their worth in a wide range of both off- and on-highway equipment, from excavators and bulldozers to fleet haulage trucks and utility vehicles, amongst others. The more lubrication points a machine has, the greater the potential advantage from having a centralized system. For small and medium-sized equipment, multi-point progressive lubrication systems ensure that a correct amount of grease is delivered to every point.

For larger equipment, where bearings require a greater volume of lubricant or the distance to the pump is increased, higher pressures are needed. There are often also more lubricant points to handle, and in these cases a single-line lubrication system is a better solution.

Lubrication unit for hydraulic hammers

Hydraulic hammers used in demolition can also be lubricated, but require a different lubricant compared, for example, to an excavator. Experience shows that operators use this type of attachment independently from the machine’s main lubrication systems. The challenge is to develop a pump unit that’s autonomous and space saving, but also required little maintenance.

The answer is a hydraulically driven lubricator designed to supply specialized lubricant with a high solids content, known as chisel paste. The lubricator is mounted directly on to the tool and connected to the machine’s existing hydraulic system. Once the tool starts to operate and the hydraulic system is activated, the pump lubricates the connected lubrication points. Mounting on a hydraulic hammer places high demands on a lubrication unit. As well as the expected environmental hazards encountered during operation, the unit must also withstand hard jolts and vibrations.

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Construction advantage

One construction company cut its lubricant consumption by nearly one-third after adopting centralized lubrication on a fleet of 50 off-highway machines, ranging in size from three to eighty-seven tones. The saving was estimated by accurately modelling the impact of a centralized lubrication system on two particular vehicles – a small wheel loader and a forty-five tone crawler excavator.

When maintained daily and used according to instructions, centralized lubrication saved around 28% for the entire fleet – equivalent to 668 kg. These savings could be boosted by a further 20% because, in practice, operators tend to press an additional stroke of grease into the grease nipple rather than use too little.

An important factor here was the use of CAN-bus (Controlled Area Network-bus) technology, which enhances operator control by allowing micro-controllers and devices to communicate with each other without requiring a host computer. Its integration with other on-board equipment and superior diagnostic facilities enhanced the company’s long-term operation of machinery.

The benefits of CAN-bus can be felt more widely. In mining, for instance, it allows each section of a hydraulic excavator, such as slewing ring, boom, arm and bucket, to be lubricated independently, according to its needs and specific operating conditions. It also allows separate control and monitoring of each section, alerting operators to errors before major problems develop. For example, CAN-bus can be used to fit a wheel loader with a single pump unit to serve a zoned lubrication system, with each zone controlled by electronic valves. Lubrication is fully integrated with the on-board computer via electronic control, and can be configured through the on-board display allowing operators to view the precise location of any problems that may occur.

Functional monitoring is performed using proximity or cycle switches, and reservoir level detection, which are both designed to detect problems such as a blocked lines, low lubricant levels or failure to perform the required re-lubrication protocol. This is a major advantage on large multipoint, complex machines where downtime is very costly.

It remains to be seen whether the construction industry can improve its operating margins, but centralized lubrication systems could help many operators boost their own efficiency levels through controlled, managed, programmed re-lubrication of their key assets.

For more information go to SKF website.

Matthew Preston on 28th of June 2017

Applications/Business Engineer Lubrication Systems at SKF Group

Source: LinkedIn Publication

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