What Do You Need To Know When Selecting Gear Oils?

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How do you know which lubricant is the right fit for a particular application? Usually, it could be as simple as searching through a maintenance manual and selecting a product from the QPL (qualified product list). The bad thing with this is that this may not always provide you with optimum lubrication for a particular gear set or prove to be of maximum efficiency in managing your lubricant inventory. Some gear oil OEMs (original equipment manufacturers) provide you with generic specifications that consider important parameters. In other cases, you may get only a general specification that would not even take into account the operating temperatures.

This is why if you are the one responsible for buying gear oil you need to have a basic understanding of how to choose lubricants for gearing. You have to be able to interpret and understand the specifications of various equipment manufacturers. Apart from that you have to understand why these specifications are what they are – you also have to be able to make changes as and when may be necessary. So, when you are selecting industrial gearing lubricants there are several factors that you must consider rather than only choosing a product from the QPL of the maintenance manual.

Getting the viscosity right

There are different grades of viscosity of gear oil and getting the appropriate one in this case remains the key. First of all, you need to find out the manufacturer’s requirements that have been mentioned on the website of the same or in the operating manual. A lot in this case also depends on the operating conditions. You may think that with the operating manual, it should not be so hard for you to choose the right grade of viscosity. However, it is not really that simple as either the operating manual is not there, or the machine is operating outside conditions for which the OEM made its recommendations.

This is why it is so important to understand the methods used in selecting viscosity and the factors that affect such a requirement. The thing with highly viscous gear oil is that it would generate heat owing to internal fluid friction. There is also a good chance that it would eat up more power to turn the gears. If the oil is less viscous it would flow through the filtration system with greater ease. It would also prove to be a lot more effective in removing contaminants.

This would reduce the possibility of the gear getting damaged and also increase the lifespan of the equipment in question.

Getting the additives right

You do have quite a lot of variations in these cases, but gear oil can be normally categorized into three categories – R&O (rust and oxidation), compounded, and antiscuff. Now, the operating conditions determine the additives you choose for your gear oils. In the case of R&O anti-corrosion properties of the oils are assessed individually for corrosion protection in the case of copper and steel. If you have water owing to condensation or leakage it can combine with ambient oxygen and this can lead to rust on steel surfaces that are not protected adequately.

Gear oil additives containing polar rust inhibitors would form a protective and compact layer that repels water. R&O gear oils normally perform well in terms of chemical stability, foam suppression, and prevention of corrosion. Antiscuff gear oils are normally referred to as EP (extreme pressure) lubricants and they do have some performance capabilities that R&O oils do not have. They have special additives to improve their ability to carry loads and film strength. Compounded lubricants are combined with synthetic fatty acids to increase their film strength and lubricity.

Ability to remain thermally stable

The gear oil needs to possess the ability to remain thermally stable and not oxidize when the temperatures are high. This will make sure that varnish or sludge is not created. If you can stop the oil from oxidizing, you would be able to lengthen the intervals of replacement and drain. A general rule of thumb, in this case, is that for every 18 degrees F (Fahrenheit) or 10 degrees C (Celsius) increase in the temperature of the fluid over 140 degrees F or 60 degrees C, oxidation would lower the service life of a lubricant by 50%.

Choosing the base oil

This is an important part of choosing the right gear oil. In these cases, it is always better to go for mineral base oils that are at least of high quality as they are well suited for most industrial applications. These oils normally have greater pressure-viscosity coefficients compared to the common synthetics. This makes sure that you get greater thickness in the film for the operating viscosities. However, there are also certain situations where synthetic base oils are a preferable option.

A lot of synthetic base materials are better than gear oil because they possess higher inherent resistance to the likes of thermal degradation and oxidation. This is the reason why they are preferred when it comes to operating in high-temperature applications. In some cases, they allow for longer service intervals. Along with that, synthetics perform better in machines that are exposed to lower ambient temperatures because of low pour points and high viscosity index. This high viscosity index makes synthetic products suitable for a diverse array of ambient temperatures. This makes sure that you do not have to change gear oils each season.

Choosing between closed and open gears

The gear oil you choose would differ depending on the kind of gear you are working with – open and closed. This particular factor would also change the options that you have in this regard. Open gears are installed in open environments without being enclosed. In some cases, they may still be enclosed but they are not sealed. Closed gears are normally enclosed in sealed gear cases. So, in the case of open gears, you would need thicker and tackier gear oils while in case of the closed gears, you would need lightweight products.