While the need to provide lubrication that ensures the efficient operation of machinery is appreciated by engineers, the finer points of lubrication practice are not always so well understood. For example, the need for re-lubrication at regular intervals is vital to maximise efficiency and machine/component lifespan but this is often overlooked. Even when the need for regular lubrication is appreciated and addressed, the application of lubricant is not always appropriate and difficulties soon emerge when either too much or too little lubricant is used. Because most engineers are aware that insufficient lubricant will allow bearings to run dry and bring a mechanical system to a standstill, there is a tendency to over lubricate. However, while the elevated temperature of an inadequately lubricated piece of equipment may swiftly lead to machine failure, it is also important to remember that too much lubricant can increase friction, increase temperature and cause migration of grease into parts where it can cause damage, such as electrical motors. And there are further problems posed by using the incorrect lubricant type, which not only increases maintenance costs and downtime losses, but also reduces the performance and lifespan of the equipment, adding costs to the plant. Conversely, good lubrication practice can extend machine life, since lubrication not only assists day-to-day running of machinery but can also offer a protective coating that protects against wear and corrosion. Clearly, operators require a reliable method of applying the appropriate level and type of lubricant in order to maintain efficiency and prevent unnecessary plant expense.

Centralised automatic lubrication

A useful tool that can be employed to avoid machine wear or failure as a result of inappropriate manual lubrication is a centralised automatic lubrication system, which can be incorporated as an external or internal part of construction machinery. Centralised lubrication systems offer the potential for engineers to prescribe the most suitable lubricant for a given piece of equipment and establish a routine whereby the system delivers a precisely regulated volume of that lubricant at regular intervals. This precision control can be especially important for lubrication points with low grease requirement because, as we have discussed, too much lubrication can be as harmful as too little.

Contamination and corrosion present a major challenge to the effective function of mechanical components, especially within the construction industry, but today’s centralised lubrication systems are sturdy constructions that offer high operational reliability. A choice of systems are available and there are many options for customisation, with specification depending upon factors such as the type of machinery concerned and the ambient temperature of the application.

Inside the system

Within a centralised lubrication system a series of powerful components are configured, such as piston pump units with an integrated control unit to distribute lubricant via feeders to a series of points within the machinery. To ensure that there is enough lubricant available for this process to be carried out, a fill-level switch indicates the volume of lubricant in the pump reservoir so that the machine operator can top up at the most convenient time.

Phil Burge, country communication manager for SKF, explained that SKF offers an easy-to-use, universal control unit called the IG502 and a further unit, the LC502, which is typically used when a wider range of control options are required. For example, in addition to time-dependent control, the LC502 can also be controlled according to pump speed; this prevents the pump speed variations that can occur for a variety of reasons, such as thermal or viscous factors.

In aggressive conditions, contamination and corrosion pose an ever-present threat to the effective function of mechanical components and that is why today’s centralised lubrication systems are such exceptionally robust constructions that can be incorporated as either an internal or an external part of mining machinery. Pumps must, of course, be of an extremely robust construction when it comes to such applications and the pumps used in centralised lubrication systems are indeed able to deliver a high degree of operational reliability, even when using highly viscous lubricants. The lubricant reservoir must also be able to hold a high capacity of lubricant for applications such as mining, which is why today’s best systems can hold up to 60 kg.

In mining, for example, the slewing ring, boom, arm and bucket of a hydraulic excavator can be independently lubricated using CAN-bus technology, allowing each section to be lubricated according to its needs and specific operating conditions. CAN-bus technology also allows separate control and monitoring of each section, alerting operators to errors before major problems develop.

CAN-bus technology allows a single pump unit to serve a lubrication system for a single machine that has been divided up to four independent zones, each controlled using electronic valves. Lubrication is fully integrated via electronic control with the on-board computer and can be configured via the on-board display where operators can view precise detection of errors. Using the CAN-bus technology, the functional monitoring is performed using cycle switches, which have been engineered to detect and signal possible problems before damage is caused to components by issues such as lack of lubricant. A major advantage of a CAN-bus system is that, when fully integrated in the on-board system, machine manufacturers can reduce the installation effort required for electrical lines.

Centralised automatic lubrication systems, which deliver precisely regulated volumes of lubricant, exactly where and when they are needed, can improve machine life and reduce operating costs. The latest systems, incorporating CAN-bus technology, provide not only a greater level of operator control but also an increased level of diagnostic information, improving the long-term operation of machinery in tough applications.

For further information please visit: www.skf.com