Leaf Chain Lubrication
Forklift truck chain users frequently assume that they have correctly lubricated their leaf chain but friction corrosion, turned pins, metallic friction, stiff joints, noisy operation and pitting still occur. In such cases, the lubricant has remained on the exterior of the leaf chain and not penetrated into the leaf chain joints. To avoid this, forklift truck chain users must ensure that the chain is slack during the lubrication process so that the lubricant can flow between the lead chain link plates and pins.
The life of a forklift truck chain that has been adequately lubricated can be up to 60 longer than that of a dry leaf chain. Running a leaf chain dry, even on a short-term basis, can substantially shorten its life. Selecting the appropriate lubricant for forklift truck leaf chain can make a significant difference. The majority of chain lubricants have been produced for transmission or motorcycle applications. However, the loading and operations of leaf chain demand a lubricant that possesses completely different properties.
The following graph illustrates the results of a test that recreated the work a leaf chain would complete when installed on a forklift truck mast. The 3 identical leaf chains used in the experiment were loaded to almost their maximum capacity, then raised and lowered repeatedly. Each was applied with a different type of oil. After 40 000 cycles, the most suitably lubricated chain outperformed the least suitably lubricated by an impressive 3.8 times. After this the least suitably lubricated chain no longer articulated whereas the other two leaf chains were able to continue operating for another 40 000 cycles.
It is also important to remember that leaf chains must be kept lubricated at all times. Forklift truck chains that operate outdoors, in low temperatures or in environments where they must be cleaned regularly or subject to condensation, need to be lubricated with oil that will remain on the chain. In these conditions operators will need to re-apply oil on a regular basis to ensure the leaf chain’s optimum life.
We carried out a further test using the same chain and lubricants, where the chains were rinsed with water for one minute before being sprayed with a holt salt water mist at regular intervals. The aim of this salt spray test was to recreate the conditions of outdoor or cold store use and allowed us to asses the corrosion resistance of the leaf chain without having to leave it outside over a period of several months or years.
Although oil C performed well in the chain wear experiment, it did not provide sufficient protection in the corrosion test. This is due to its lower viscosity which helps the lubricant to penetrate between the pin and plates but is easily removed with water. If the forklift truck chain were operating outdoors or in cold stores, the oil would not stay on the chain long enough to protect the chain from corrosion. Oil B, however, provides a better compromise between wear and corrosion resistance.
Many forklift chains become encased in dirt and dust which prevents oil from flowing to the vital load bearing sections of leaf chain between the articulating link plates and pins. To avoid this, it is essential that leaf chains should be removed of all dirt and debris. Regardless of the type of lubrication or frequency of application, if dirt and debris is not removed, the lubricant will not flow to the critical contact areas on the leaf chain where it will be most beneficial.
Further information on cleaning forklift truck leaf chain can be found in the leaf chain maintenance section of this website.