Almost every type of industrial machine featuring rotating parts requires lubrication. The starting point for introducing a lubrication system typically involves mapping out the optimum lubrication points, after which thoughts turn to the most effective method of application. According to Jens Kammann, group marketing manager, lubrication & REP, SKF, automatic lubrication offers a number of advantages over manual application, including those relating to timing, quantity, contamination and safety.
“Failing to re-lubricate frequently enough means the grease deteriorates and cannot fulfil its functions,” he says. It should also be noted that applying the correct amount of lubricant is critical. Too little has its obvious consequences, while Kammann says that “too much can shorten lubricant life though higher mechanical stresses and increased temperatures”.
As manual lubrication typically requires the use of grease guns or pumps, the potential for contamination to enter through filling and connection activities is elevated, promoting the potential for friction and surface damage. Safety is also compromised as most machines require re-lubrication when the machine or equipment is running.
In automatic systems, lubricant is supplied to the application at pre-programmed intervals. These solutions can deliver lubricant to many points simultaneously, taking into account that some re-lubrication points require higher or lower quantities. Alternatively, automatic single-point lubricators supply grease to individual lubrication points, making them preferable where points are spaced far apart.
“Automatic systems supply lubricant in the right amount at the right time,” says Kammann. “Moreover, the system is permanently connected to the lubrication point, preventing contamination from entering, while the reservoir holds larger quantities and requires less frequent refills. Single-point lubricators use pre-filled cartridges that ensure clean grease reaches the lubrication point. Safety is also assured, particularly as automatic systems can be equipped with monitoring capabilities to ensure pumps work within nominal operating conditions, and reservoirs are filled. In addition, connected systems can be controlled remotely, allowing lubricant supply to stop when the application is not in use, for example.”
In an automatic system, a reservoir holds the lubricant, although in some cases grease can be pumped directly from the drum. From the reservoir or drum, the lubricant is pumped to distributor blocks and metering devices that control and measure the correct amount of grease for application.
QUANTITY IS CRITICAL
What is the optimum level of lubrication and how is it decided? The design of the application and important operating conditions (speed, load and temperature) have a large influence on this decision. Some suggest that savings in lubricant costs of up to 50% can be achieved due to the accurate timing and dosing of lubricants.
“Imagine an electric motor that is used to drive a heavy fan,” says Kammann. “The motor might be installed in cold climates, next to sandy deserts, close to the sea or in a dry environment. This means that the lubricant needs to cope with various operating conditions and perform differently.”
Tools like SKF LubeSelect, SKF BearingSelect or SKF DialSet (for single-point lubricators) help to find the right grease for a given application and calculate the optimal initial lubrication, as well as re-application intervals.
In terms of maintenance and repairs, common system failures include empty lubrication reservoirs (leading to air in the system), clogged lubrication points and failed/damaged lubricant lines.
The company’s gas-driven lubricators are for single use and ready-to-go out of the box, while refill sets for electro-mechanical lubricators are supplied with a lubricant cartridge and battery pack. Electronic monitors provide signals if a failure occurs.
AVOIDING PREMATURE FAILURES
Downtime is the bane of an engineer’s life. According to Sally Sillis, technology centre manager at Schaeffler UK, more than 50% of electric motor breakdowns are due to premature bearing failure.
“Common problems include using an incorrect lubricant, mixing lubricants, as well as administering the wrong amount of lubricant, or no lubrication at all,” she says. “However, the correct choice of automatic lubricator can rectify these issues.”
Sillis adds: “The traditional method of determining lubrication timing and quantity is to re-lubricate at 50% of the calculated grease life, with 50% of the original grease fill. For example, on an electric motor there will be a plate that may state ‘100g of grease every 3,000 hours’. However, this can be problematic for effective lubrication, as the machine may not run continuously. It is highly likely that the person using a grease gun will lubricate too often, not at all, or even use a different lubricant.
However automatic lubricators are said to take the judgement away; they only require cartridge replacment or replenishment.
Current automatic lubricators available from Schaeffler include the Concept 4, a four-point automatic system regulated via an external control unit. This solution exclusively targets customers with an existing PLC infrastructure. However, it will not be long before Schaeffler launches cloud-connected smart automatic lubricators.
MATTERS OF PRINCIPLE
Another expert in lubrication solutions is H-T-L Perma, the UK subsidiary of Perma-tec, which offers two different automatic lubrication systems. An electrochemical system’s driving force is via a chemical reaction that generates a gas; an electromechanical system uses a battery-powered drive. Maintenance to ensure optimum operation are slightly different for each.
“For instance, with electrochemical systems, operations engineers should note the installation date on the lubrication system or use the Perma MLP (maintenance lubrication programme) app to scan the QR code,” says Daniel Gogola, business manager - UK & Ireland. “Visual checks are also advisable during operation while, after the discharge period, engineers should replace the system with a new one and check the lubrication point. With the Perma MLP app, users receive notification when the system requires replacement.”
The same process is applicable to Perma’s electromechanical systems, although these feature sufficient intelligence to make all status information visible via LED lights, indicating whether any action is necessary.
“With Bluetooth-enabled automatic lubrication systems, operatives can use the Perma Connect app to check operating status and maintenance requirements,” says Gogola. “Data can be read and actions can be started over-the-air.”
BOX: AN INSTALLER’S PERSPECTIVE
At Bolton-based Harrison Lubrication Engineering, the approach to lubrication system design differs according to the application.
“Some small systems can be specified over the phone, or with drawings and photos, while others require a site visit,” explains technical sales engineer Lee Allen. “We look at the machine and ask relevant questions to find out what needs lubricating and how often, as well as the location, access and distances of lubrication points. We can make a questionnaire available if required. Some limitations might include excessively large distance between lubrication points, ATEX atmospheres and high temperatures.”
HLE reports it is currently working in most industries, including food, paper and aggregates. With regard to post-installation services, although the company offers different types of ongoing maintenance contracts in line with specific requirements, there are things the customer can do in terms of best-practice housekeeping.
“It is advisable to clean the lubricant refills and check the reservoir is topped up,” says Allen. “However, most of our systems self-monitor, informing users if there's a low level or blocked line.”