Cutting the cost of lubrication
2012 June 01, 09:00 GMT
How advances in centralised lubrication systems such as CAN-bus technology are enabling both efficiency gains and major cost savings for operators.
While the need to provide lubrication that ensures the efficient operation of mining 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.
One way to avoid the machine wear or failure that can occur when manual lubrication is infrequent or inappropriate is to fit centralised automatic lubrication systems. These 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 lubricant, exactly where and when it is needed. By applying a precisely metered volume of lubricant to the machine parts that require lubrication at controlled intervals, centralised lubrication systems, which can be incorporated as external or internal parts of the machine, can improve lubrication efficiency, cut costs and extend part life.
In heavy industries such as mining, where corrosion and dirt pose a major challenge to the effective function of mechanical components, centralised lubrication systems offer a powerful alternative to conventional methods. A choice of systems is available and specification depends upon the type of machinery concerned, the ambient temperature of the application and the operating conditions. There are many options available for customising these systems and users of today’s advanced systems can rely on sturdy constructions that offer high operational reliability.
Centralised lubrication systems incorporate piston pump units with an integrated control unit distribute lubricant to progressive feeders, which consecutively supply the quantity of grease required to the individual lubrication points. Pump units are available to meet the demands of heavy machinery, with capacity for high lubricant consumption, sturdy construction and the ability to handle highly viscous lubricants.
While the pump is running, each point receives an optimum level of lubrication, while a display showing the fill level of the reservoir enables a top-up during work breaks and scheduled machine downtime. The display can also offer feedback on the level of lubricant consumption; this means that if there are any unexpected deviations from the normal pattern, the situation can be investigated.
SKF offers the IG502 base unit, a universal, easy-to-use, standard control device for progressive centralised lubrication systems, while further operational features are offered by the LC502 control unit, which, for example, can offer both time-dependent control in minutes or be controlled based on pump speed. The latter option provides the benefit of preventing pump speed variations that are not considered when using solely time-dependent control. The advantage of precisely distributing lubricant is especially important for lubrication points with low grease requirement because, as we have discussed, too much lubrication can be as harmful as too little.
A key development in the latest systems is the use of CAN-bus technology, which provides even greater operator control, integration with other on-board equipment and the facility to increase the level of diagnostic information, thus improving the long term operation of machinery still further.
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.
Using a centralised lubrication system not only increases efficiency and cut costs, it can benefit the environment, too. SKF recently helped a customer in Germany to adopt centralised systems in 50 machines ranging from 3 to 87 tonnes. By modelling the impact of the systems on a small wheel loader and a 45-tonne crawler excavator, we were able to accurately estimate lubricant savings. If maintained daily and according to instructions, the use of automatic centralised lubrication systems enables a calculated annual lubricant savings of approximately 28% or 668 kg for the entire fleet. While this is clearly a major saving in itself, the actual savings will be even greater because in practice operators tend to press one additional stroke of grease into the grease nipple rather than use too little, which could amount to a further 20% saving.
Specification will depend on the size of a machine, type of required lubricant and number of lubrication points but engineers who are investigating the use of centralised systems may wish to consider some of the following more commonly specified systems. For small- to medium-sized machines, single-line lubrication systems for semi-fluid grease dispense lubricant volumes from 0.01cc to 2.5cc to individual lubrication points on each lube pulse. For medium-sized and larger machines, dual-line lubrication systems for semi-fluid grease and hard grease provide solutions with many lubrication points, long lines, and operating in harsh conditions, such as those experienced within the mining industry. Progressive lubrication systems for semi-fluid grease and hard grease are ideally suited to machinery such as hydraulic excavators and when additionally equipped with CAN-bus technology they can control, deliver, and monitor lubricant in real time. This allows lubrication points to be continuously supplied with metered lubricant while the machinery is in operation and all the bearings are moving. More advanced systems will incorporate a malfunction diagnosis memory, which will not only display error notifications but record how long a machine has been continually operated and log the date, time, and type of any error.
It is important to note that centralised lubrication systems can benefit not only new but also existing machines; heavy machinery can be conveniently retrofitted with centralised lubrication systems as long as your supplier provides complete kits with all necessary components, plus the plans and instructions for assembly.
It is crucial to the efficient operation of mining machinery that effective lubrication is provided and the failure of manual lubrication to deliver the correct lubrication to the correct degree can lead to excessive waste, increased cost, machine wear and failure.
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 mining machinery.
Technical article above was published in the June 2012 edition of Mining World.