Lubricants and coolants are two of the most common contaminants requiring removal in industrial cleaning. Understanding their basic nature and how they work may help lead to the solution of many cleaning problems
Lubricants help prevent friction between two surfaces moving relative to one another by, in effect, providing a barrier between the two surfaces so that they don’t really touch. There are many different types of lubricants – basically anything that will prevent contact between two surfaces moving relative to one another will work. The earliest lubricants were natural oils and greases. Lard, fat rendered by heating animal tissue once the edible parts are removed, is an example of a natural lubricant. Oils are present in a number of plants including olives and corn. Graphite is an early example of a solid lubricant. Today’s lubricants, although much more sophisticated, work in basically the same way as the earliest lubricants.
By reducing friction, lubricants make it possible to cut metal with less effort. Lubricants also reduce the amount of heat generated by surfaces moving relative to one another. For these reasons, lubricants are an essential element in manufacturing operations in which metal and other materials are cut, shaped or formed. In reality, lubricants need only be applied at the point of contact between the two moving surfaces. In practice, precise placement of lubricants is nearly impossible. This results in the use of much more lubricant than is actually required in most applications which, in turn, leads to the need to remove large amounts of lubricant by cleaning once the operation is complete.
Although lubricants reduce the amount of heat generated as two surfaces move against one another, when there is also metal deformation (as in a metal cutting process) the friction generated as the metal is cut or deformed still generates a considerable amount of heat. To remove this heat, lubricants are often mixed with water (or another good heat conductor) to make what is called a “coolant.” These formulations also include constituents which allow the cooling part of the formulation and the lubricant part of the formulation to mix together to form an emulsion. Emulsions, as described in an earlier blog (search “emulsion”) can be either stable or temporary. The components of a stable emulsion will not separate due to gravity over time due to the fact that one component is heavier than the other. Temporary emulsions, if not constantly mixed, will separate into their component parts over time with the heavier component at the bottom and the lighter component on the top. The time required for separation to occur may range from several minutes to several hours.
The main purpose of a cleaning process it is to remove a contaminant (such as a lubricant or coolant) from the parts being cleaned. An integral part of an efficient cleaning process, however, is also containing the contaminant and moving it to a final disposition such as disposal or re-cycling. It is important, then, to know as much as possible about the lubricants or coolants being used in a process to be able to design an effective cleaning process. In some cases, in fact, the available cleaning process leads to the selection of lubricants or coolants the will be efficiently removed and handled by that process.
Lubricants or coolants and cleaning processes go hand in hand and must be appropriately matched. One common mistake is the initiation of a change in either that upsets their compatibility. Before any changes are made, tests should be conducted to verify that the new combination will produce the desired result. Upcoming blogs will discuss how different lubricants and coolants affect the design of cleaning systems used to remove them.
– FJF –