Tagged: grease

Grease compatibility

We recently touched on greases being available in a wide variety based on application but the real question is, “Are all greases compatible?” The short answer is, “No”.

All greases contain a thickener (which helps with its physical state). Thickeners vary depending on application (such as temperature, water resistance etc). As such, to verify whether two greases are compatible or not, Machinery Lubrication developed a Compatibility Chart based on thickener type.

You can determine the thickener type by looking at your Data Sheet or talking to your OEM. Not all greases are compatible, so be careful when mixing greases!

Grease Thickener Types

We keep speaking about each grease being different based on their thickener type. However, what are the properties that these thickeners give to the grease? For instance, if I wanted to use a grease for a roller bearing in a very high temperature environment which should I choose? Can a multipurpose grease work for that application?

Each area of application may be different and while multipurpose greases are widely used there are some areas where it doesn’t add much value. For example, if a heavy equipment operator uses a backhoe to dig into a river, the multipurpose grease can be easily washed off.

When the grease washes off quickly, the pins holding the bucket can become damaged. (The costs to repair or replace one of these pins are ridiculously high!) However, if he used a Calcium based grease, then there wouldn’t be an issue of water washout and the pins could have a longer life.

Above is a table indicating the various uses of greases based on the thickener types. Know your applications and their environments when choosing the right grease!

Base oil viscosity of greases

While we’ve focused on the variances in greases due to thickener types, we haven’t touched much on the differences in base oil viscosity.

With gear oils, we need the correct viscosity to allow the gears to turn at the required rate while still being lubricated. If the oil is too thick and the gears are high speed, then the gears will not be lubricated quickly enough and they can become damaged. Similarly, greases are made up of base oil with different viscosities.

Most greases use a viscosity of 220cSt (these are the multipurpose greases). However, greases for electric motors use a base oil viscosity of 100cSt. What’s the difference?

Well, if a multipurpose grease was used for an electric motor the energy used for that motor can be 100W however, if a grease with a base oil viscosity of 100cSt was used, the energy used could be reduced to 70W. Is this significant? Definitely YES!!!

On any manufacturing plant, there are at least 5 – 10 electric motors, in some cases there are 70 or more! If at least 25W were saved per motor per month then the company can a significantly reduced power bill at the end of the year!

Understand your applications before applying “any” grease!

Grease Thickener Temperatures

The grease thickener has a crucial role in deciding the environment in which a grease should be applied. One of the major environmental conditions revolves around the operating temperatures that greases have to endure. If the grease goes past its dropping point then it can turn into a liquid, leak out of its designated area and cause the element to be starved for lubrication. Not to mention the mess on the outside of the component after it has leaked out.

Each thickener has a range of operating temperatures. However, some consideration should be applied when designating areas for the application of the grease. As indicated above, a good rule of thumb is to ensure that the application range of the grease does not exceed the Dropping point – 50C. For example, a good operating range for a simple Lithium grease can be 175-50C = 125C. This still falls within the maximum service temperature for a grease with this thickener.

Pay careful attention to your operating temperatures when selecting your grease!

Understanding NLGI

Does the NLGI grade matter? Of course it does! That’s why it was invented and classed into different categories for various applications! NLGI stands for National Lubricating Grease Institute, they are composed of companies that manufacture and market all types of lubricating grease.

An NLGI grade can start at 000 (very fluid) to 6 (block like). However, there are different grades for different applications.

For instance, most trucks have a centralized lubrication system. As such, the grease needs to be almost fluid like to get to all the areas. In these cases, a “00” or even “000” grease may be used. However, the most common grade is a “2” grade which is seen frequently in cartridges, pails etc.  Some electric motors require a “3” grade grease instead of a “2”.

Here is a table that describes each of the grades, their applications and consistency.

Always check with your OEM to ensure that the correct NLGI grade is being used! Here is another graphic that likens these grades to more easily identifiable consistencies.

Grease colours

I’ve almost always heard my customers refer to the grease that they are using by its colour. They would say, “I’m using the blue grease.” However, greases are not defined by their colour. Colour is often added to grease to allow it to be easily identifiable within the field. For instance, if a grease is coloured blue, it is easy to identify if it’s leaking or not (one way not to confuse the leak with an oil leak).

Some greases are coloured to ensure that the applicant uses it in the correct application. For example, if a blue grease is a multipurpose grease then this ideally shouldn’t be used in the very high temperature area. Most of the times, red greases are used for high temperature applications. Thus making it easy to identify if the correct grease is used in the right application. However, one should note the colours of the greases being used in their facility and their applications before comparing them to that of another facility (which may be using a different grease manufacturer.)

Don’t define greases by their colours, define them by their applications!