The Importance of Lubrication for Chains

Chains are often an overlooked component in machines or logistics systems, but they are incredibly vital. Without the drive chain, machines would not operate, and logistics systems would come to a halt.

Roller chains have proven to be an effective method of power transmission. Essentially, a roller chain consists of a series of precision bearings made up of inner and outer link plates, bearing pins, bushings, and rollers. However, in addition to these well-known components, there is another critical part of the roller chain — the lubricant.

Proper lubrication of a chain is a highly cost-effective operation. A well-lubricated chain should run for at least 15,000 hours before showing excessive wear and requiring replacement. However, in real-world applications, many chains fail to reach this lifespan. Around 60% of failures are due to inadequate or improper lubrication.

This lack of lubrication leads to longer downtimes, increased material and maintenance costs, and overall reduced system performance, resulting in higher operational costs. Extended downtime, in particular, can cause significant losses. The cost of machine downtime in manufacturing can reach up to 50 euros per hour. Proper lubrication can significantly lower these costs.

Lubrication Before Installation

Proper lubrication should begin before installation. A chain that is well-lubricated at the factory has already received optimal basic lubrication, often through a hot oil immersion process. However, subsequent re-lubrication in the system can cause the initial lubrication to degrade, especially if a diluted oil containing solvents is used, as this will wash away the original lubrication. Numerous failures during operation due to lubrication errors demonstrate that proper chain lubrication remains a process with many potential mistakes.

Common Lubrication Issues

Incorrect lubrication methods and the use of unsuitable lubricants are common sources of trouble. Most importantly, selecting the correct lubricant is crucial for achieving optimal efficiency. For example, heavy oils and greases are often too thick to penetrate into the chain and reach the actual working surfaces. Applying grease to the exterior of the chain merely acts as a sealant, obstructing the work process and leading to higher wear, ultimately causing premature failure. This means that the required lubricating film usually forms only during initial use.

Lubricants can pass through the gaps between the plates, resulting in an even thin film. However, subsequent re-lubrication leads to thicker layers of grease on the plates and rollers. As dust accumulates, the chain becomes increasingly thick and caked, which prevents the lubricant from reaching the small spaces inside the link. From the outside, the chain may appear to be properly lubricated, but inside, crucial components will run with high friction or, in the worst case, become dry.

It is also important to note the use of lubricant sprays as an alternative. These sprays often contain volatile diluents, meaning they evaporate quickly after application. What remains is a sticky lubricant film that cannot flow and blocks the smoothing process, contributing to wear.

Correct Chain Lubrication

When lubricating chains, it is always important to check the chain pins. Ideally, the entire surface of the pins should be completely covered by a layer of lubricant. Furthermore, when the lubricant is removed, the surface should be uniform and as smooth as glass on the load side. Oil is the standard re-lubricant for chains, as, except for some applications, removing the chain and re-immersing it in hot oil is too complicated for most chains. It is generally recommended to use oil with a viscosity between 150 and 450 cSt. In many cases, lower viscosity oils provide insufficient lubrication when there is high surface pressure in the joints, while higher viscosity oils may fail to reach the link pin and bushing areas.

Choosing the Right Lubricant for Chains

Given the design of chains, lubricants need to pass through narrow gaps between the plates. The best lubricants for this purpose are liquid products that do not contain diluents, allowing enough lubricant to enter the link. However, this process is prone to errors. One of the most common lubrication mistakes involves the treatment of the surface and chain rollers. These components usually require minimal lubrication because they don’t experience as much friction or movement. However, when troubleshooting, it is often shown that lubricants are overly applied in these areas.

The choice of chain lubricant depends on a variety of factors, including environmental conditions. For example, in areas with a lot of dust, such as lime, talcum powder, or flour, wax-based greases should be used for initial lubrication. However, these lubricants have the disadvantage that they often do not reach the links during re-lubrication. Therefore, wax-based lubricants should be used specifically when re-lubrication is difficult or impossible, and where the environment poses a risk of dust drawing the lubricant out of the joints.

Working Temperature

Working temperature also plays an important role in the selection of lubricants. The best viscosity for each temperature range is outlined in the table. Mineral oils are suitable for most applications. However, if grease lubrication is required, it is particularly important to heat the grease to a liquid state before immersing the chain in it until no bubbles are visible. Chains lubricated using this method will require regular cleaning and re-lubrication. Due to the limitations of lubricants, chain temperatures should generally not exceed 100°C.

In special cases, chains can operate at temperatures up to 250°C for certain applications while still performing well. In these cases, special oils are required for high-temperature applications. One effective way to improve lubrication and cooling is to use forced feed lubrication, with a high oil supply (up to 4.5 liters per chain per minute) and an external cooling oil system. For very high temperatures (such as in oven chains), graphite or molybdenum disulfide can be used in a mixed form with oil or spray. In these cases, dry lubricants are often used, as re-lubrication is difficult and may negatively impact the products in the oven.