May 2019

Chains are often given little attention as components in machines or logistics systems. For the overall system, however, they are of great importance: without a drive chain the machine will not run, and without conveyor chains the logistics will not work. Chain manufacturer, Renold, offers tips on how to make chains last longer with the help of the correct lubrication. T he correct lubrication is an operative and economic factor that can hardly be overestimated: in most applications a properly lubricated chain should last for at least 15,000 operating hours before it should need changing due to wear. In many cases, however, chains do not last nearly as in various applications. In around 60% of cases, poor or insufficient lubrication is the cause of chain failure and is therefore the single biggest risk factor. The consequence: higher costs due to longer downtimes, increased material and maintenance costs and reduced overall system performance. Downtimes in particular can be a significant financial cost factor. Manufacturing industries calculate that the downtime costs of a production machine can be up to Euro 50,000 per hour – costs which can be saved with carefully thought-out and responsibly safeguarded lubrication. Tests have shown that chains that are properly maintained can last up to 60 times longer than chains that are incorrectly lubricated or not lubricated at all. Frequent lubrication errors Correct lubrication starts before the installation stage is even reached. Well-lubricated chains are already provided with optimum basic lubrication at the factory and, depending on the application, this is normally through hot grease immersion. Immediate relubrication in the system will often lead to a deterioration in the initial lubrication, especially if a thin oil containing a solvent is used which immediately washes the initial lubrication out of the chain. During operation, the large number of failures which are due to lubrication errors show that correct chain lubrication continues to be a process in which many errors are made. The wrong lubrication methods and the use of the wrong lubricants are some of the most common sources of trouble. Above all, the right choice of lubricant is critical for achieving optimum efficiency. Heavy oils and greases, for example, are too stiff to penetrate deep enough into the chain to reach the actual working surfaces of the chain. Applying grease to the grease on the plates and rollers. With the accumulation of dust as well, the chain becomes increasingly thickened and encrusted, which in turn prevents the lubricant from reaching the small spaces in the chain joints. From the outside the greased chain might appear fine, but the important components on the inside of a chain will be running with a high level of friction or, in the worst case scenario, dry. Care also needs to be taken with the use of lubricant sprays as an alternative. These often use thinners which are generally volatile, in other words they quickly evaporate after application. What they leave is a viscous film of lubricant which is not capable of flowing and which, in a similar way to encrustations, prevents a smooth process and therefore contributes to wear. When it comes to correct lubrication, therefore, it is always important to examine the chain pins of the connecting link. Ideally the entire surface of the chain pins should be completely covered with a film of lubricant. In addition, the surface should be uniform and as smooth as glass on the load side when the lubrication product has been removed. Oil is Process, Controls & Plant Focus on: Seals, Bearings & Lubrication outside of a chain will only act more as a sealant, impeding the work process as a consequence and resulting in higher wear. This ultimately leads to the premature failure of the chain. In more precise terms, what this means is that the desired film of lubricant is often only formed on first-time use. The lubricant can pass between the spaces between the plates and form an even film as a result. Further relubrication thereafter, by contrast, will result in the development of increasingly thick layers of Properly lubricated chains last longer 24 | Plant & Works Engineering www.pwemag.co.uk May 2019