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So you’re looking for a grease, you’ve seen many references to ‘Lithium EP2’ but you’re not sure what it means or whether it is relevant to your needs? Let’s try and cut through the jargon!
First of all, what is a grease? Over the years grease has become a staple of the engineers toolkit and has found a number of different uses. However primarily it is a form of lubricant specifically designed for parts that need infrequent lubrication or where oil would not stay in place e.g. rolling element bearings. Grease is made up of a number of constituent parts, one of which is oil which can typically make up 90% of the formulation. It is the oil in the formulation that actually does the lubricating. However oil poured into a bearing would very quickly find its way back out of the bearing! Therefore the oil needs a carrier of some kind to keep it in place and release it slowly into the parts to be lubricated. This, in essence, is the role of a grease.
There are 3 main constituent parts to a grease:-
In simple terms, the oil is the part that carries the main dynamic lubricating responsibility, the thickener determines the physical characteristics of the product while additives enhance the operating properties of the grease. Lithium is a type of thickener so we will concentrate on that area here. A thickener not only provides structure to hold the oil in place, it also acts as a ‘sponge’ releasing small amounts of oil during operation. There are several different types of thickener depending on the application. Extremes of temperature, moisture or speed may all require different types of thickeners. However for many applications that are deemed non-extreme or general purpose in nature, Lithium is a popular choice. It has good all-round properties and is relatively inexpensive to produce. The majority of greases, especially those used in general or multi-purpose applications will use Lithium as a thickener.
‘EP’ stands for ‘Extreme Pressure’ and is a term used to describe lubricant applications that are subjected to high load conditions. Additives, both physical and chemical, are used in grease formulations to give a product its high load capabilities or ‘EP’ performance. However it is worth saying at this point that the ‘EP’ part of a greases description has recently slipped into popular parlance whilst not always being relevant. That is to say that it is not always necessary (nor sometimes desirable) to use a grease with added extreme pressure performance. Furthermore if the grease has been chosen correctly in the first place dependent on specific requirements, greases without ‘EP’ performance can cope just as well with the demands placed on it than those with added EP performance.
The number at the end of a greases description relates to its hardness or consistency. The numbers range from ‘000’ which is a semi-fluid grease to ‘6’ which is a solid block. The numbering system and the classification standards were developed by the National Grease Lubricating Institute (NLGI) hence this number is often referred to as the NLGI number. The most common grade of grease in use Worldwide is an NLGI 2. Greases in this category have a consistency like toothpaste or peanut butter. They are normally firm enough to stay in place but soft enough to be penetrated and worked fairly easily (it is this physical manipulation that releases the oil from the formulation allowing dynamic oil lubrication to take place.) Whilst it is the most common grade it is not necessarily the right choice for every application – if in doubt check.
Univar Specialty Consumables has a large range of greases from different manufacturers and we would be only too pleased to advise you on the correct choice of lubricant for your application.
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