The Importance of Chain Lubrication
A chain is a series of travelling journal bearings connected to the teeth of a sprocket, which allows transmitting force and motion to a mechanism. They are used in many industries for power transmission and transport.
To ensure optimum efficiency, it is important that chains are well lubricated; allowing chains to obtain their maximum service life. Chain lubrication is needed to slow down the appearance of wear between the pins and bushings in the chain joints, as well as to flush out all the foreign materials and debris. Lubrication can also protect against rust and corrosion, dissipate heat, and cushion impact forces.
If a chain is not well lubricated, it can fail in a number of ways:
Tensile fail – The chain is overloaded in tension until it reaches the point of plastic deformation and does not work properly.
Fatigue failure – The chain is repeatedly loaded in tension below the yield strength of the metal. After repeated load exposure, a series of microscopic cracks can develop in the link plates or sidebars which could break the chain apart.
Wear failure – Material is removed by sliding, corrosion or abrasion until the chain does not function correctly.
Most chains fail due to wear between the pin and the bushings as this causes the chain to extend to the point where it no longer fits the sprockets. Wear between the roller and the bushing or between the link plates and the guides can also cause the same issue.
Selecting the Right Lubricant
Selecting the right lubricant requires a complete understanding of the operational and environmental conditions a chain is subjected to. While some applications may require a lubricant with a low enough viscosity to penetrate into critical internal surfaces, it is important that a high enough viscosity is maintained to ensure an effective film thickness. In terms of environmental conditions, the presence of dust or other non-desirable pollutants can lead to waxy or tackier lubricants to be the preferred choice for the application.
The wrong lubrication methods and the use of an incorrect lubricant are some of the most common sources of chain failure.
For example, heavy oils and greases are too stiff to penetrate deep enough into some chain to reach the actual working surfaces. Applying grease to the outside chain will act as more of a sealant, impeding the work process and ultimately resulting in higher wear.
Further relubrication can also have a negative impact as this will result in the development of increasingly thick layers of grease on the plates and rollers. With the addition of dust particles, the chain becomes increasingly thickened and encrusted, which in turn prevents the lubricant from reaching the small spaces in the joints.
What to Consider?
The wrong lubrication methods and the use of an incorrect lubricant are some of the most common sources of chain failure. Most importantly, the correct choice of a lubricant is capital in order to achieve optimum efficiency.
For example, heavy oils and greases are too stiff to penetrate deep enough into the chain to reach the actual working surfaces of the chain. Applying grease to the outside chain will only act more as a sealant, thus impeding the work process, and ultimately resulting in higher wear. This entails a premature failure of the chain.
Further relubrication, on the other hand, can also have a negative impact. Indeed, this will result in the development of increasingly thick layers of grease on the plates and rollers. With the addition of dust particles, the chain becomes increasingly thickened and encrusted, which in turn prevents the lubricant from reaching the small spaces in the joints.