Some industrial machines have bearings that rotate faster than the usual processing speed of an average machine part. These fast-moving bearings are usually involved in high-speed applications like fans, blowers, and pillow-block bearings. However, these components require special lubrication, and if lubricated incorrectly, can cause the whole system to shut down over time.
Moreover, if they are grease-lubricated components, their lubrication becomes even more complex as grease does not dissipate heat that well. Greased components tend to run hotter and lead to increased heat, drag, and premature machine failure.
In this article, we discuss three important factors of high-speed greases that can help you control excess heat and increase your grease’s life. By selecting the right grease that can handle these high-speed applications, you can reduce the chances of machine damage caused by a mismatched lubricant.
Base Oil Viscosity
Viscosity is the most important factor when choosing the right grease for a high-speed bearing. The base oil component of the grease is what keeps the two parts of the machine from coming in contact with each other, and only with the right viscosity can this base oil keep the parts separated.
One way to determine the right viscosity is to determine the bearings speed factor, which can be calculated by the formula: Bearing speed ( revolutions per minute) x Pitch diameter of the bearing. If the bearing's speed increases, the speed factor will also increase, which means the lubricant's viscosity for the specific application will need to decrease.
At the 600,000 (NDM) speed factor, a base viscosity of less than 70 centistokes at 40 degrees C is ideal. But it is important to keep in mind that since the temperature is also very high in high-speed applications there will be shorter grease life, the overall grease properties must be designed according to these conditions. As the temperature increases, the viscosity of the lubricant significantly begins to decrease.
One property of grease that can determine how well it will perform at high-speed applications is channeling. Channeling is the flow of grease and its ability to fill a void left on the surface. So, if the grease can fill the void, it is called non-channeling, and if it cannot fill the void or channel within 10 seconds of its creation, it is called channeling grease.
Channeling greases are easily pushed out of the component's way as it rotates, leading to less churning and less temperature gain. Whereas non-channeling greases flow back into the void created while bearing rotation, leading to excess heat. In simple words, the grease type should channel, so the excess heat isn’t generated from churning.
The dropping point is the temperature at which grease changes from a semi-solid state to a liquid state. This is the highest temperature at which grease will retain its structure; however, it is not the temperature at which it should be used or operated. That number can vary from dropping point.
To select the right grease for high-speed applications, make sure the grease's dropping point exceeds the operating temperature of the bearing by a wide margin so excessive bleed and possible bearing failure can be avoided.
These are three factors that can help you determine the right grease for your high-speed application. Other factors that can determine your grease choice are its thickener type, the greases’ NLGI Grade, and the additive load.
Each part of the machine requires a specially designed lubricant to work efficiently. One wrong use of these greases or applying low-grade oil to these parts can halt the entire plant process. For this reason, it is essential to buy your lubricant only from experts in the industry.
Micro-lube is an industrial-grade machine lubrication company based in Canada. Our high-quality lubricants, oil analysis, and oil filtration products are the best in the market and are specially designed to meet all your lubrication needs. To learn more about our lubrication products or to get a free quote, click here.