In all industries, but particularly in the food industry, it is valuable to understand the makeup of the lubricant that is applied to equipment operating at elevated temperatures.
In addition to other areas, the various base oils used in lubricants are affected by extreme temperatures in the levels of evaporation loss and in the formation of residues—factors that influence chain life.
Each type of base oil has a different temperature limit—and even going slightly past this limit can have a dramatic effect. For instance, at temperatures above 500-600°F (260-315°C), even synthetic esters, which are excellent performers in many bread ovens, can evaporate. As a result, frequent relubrication is needed to keep the chain lubricated and protected. However, even with constant relubrication, the continuous break down of certain types of base oils can thin the lubrication barrier, which reduces component protection. Also, residue levels become higher, which impairs fresh lubricant from reaching the intended surface(s).
A common method used to lubricate chains operating at extreme temperatures is to use a solid lubricant. The solid lubricant is in suspension within a fluid carrier when the lubricant is applied. As the fluid carries the complete formulation into the components and begins to evaporate, the solid stays behind inside the friction points as a type of emergency protectant to decrease wear of the surfaces.
Understanding the importance of the types of carrier fluid and solid being used is critical. As with any formulation, they should be selected based on the complete tribological environment. Other important factors include how the lubricant will be stored, the method in which it will be applied to the chain and when it will be applied.
A lubricating formulation using solids held in suspension is likely to require mixing either when being stored or prior to application. Stirring can be done with various methods, such as using an agitator pump inside the lube reservoir. Agitation maintains the proper ratio of the fluid carrier and the solid lubricant(s) during application, which can then be done using an automatic lubrication system.
Because the carrier will eventually evaporate, the application should be performed at a temperature allowing the carrier to first deliver the additives into the friction points. Otherwise, if applied while the oven is at full or too high a temperature, heavy smoking and flashing off of the oil will occur when it contacts the chain. It is best to apply the lubricant at a lower temperature within the operating range of the carrier to allow penetration of the solid additives.