![]() Some grease thickeners have long fibers, while others have short fibers. The structure of the fibers in the thickener can affect certain grease properties, such as channeling, bleed, dropping point and overall consistency. The thickener in a grease is commonly referred to as the “sponge that holds the oil”. In this test, grease is applied to a container, and the surface is leveled off.Īside from the base oil viscosity, another grease property that impacts its channeling characteristics is the thickener type. Method 3456.2 of Federal Test Method Standard 791C offers one way to test the channeling characteristics of a lubricant. This term is used to define how well grease can flow and fill a void left in its surface. One property of a lubricating grease that can determine how it will lubricate at high speeds is called channeling. However, it is worth noting that not all greases are created equal, and not all can perform well at varying speed levels. Some greases on the market are touted to work up to speed factors of 2 million. This is when specially formulated high-speed greases are employed. With grease, it is common to be able to lubricate bearings easily until they reach speed factors greater than 500,000. The energy consumption can also add up over time, resulting in money lost due to nothing more than the increased drag from excess viscosity. This can cause increased grease run-out and require more frequent applications of fresh lubricant grease. The hotter the bearing runs, the lower the viscosity of the grease becomes. Both of these are detrimental to the health of the bearing and the lubricant. While these type of greases may work fine for moderate speeds and loads, when the bearing speed increases, the viscosity must be reduced accordingly.Įxcessive viscosity can lead to excess heat generation and increased energy consumption. Most general-purpose greases have a base oil viscosity of around 100 to 220 centistokes. This must be matched to the needs of the bearing. Viscosity is what determines how thick or thin the lubricating film will be based upon the load, speed and surfaces in contact. The most important physical property of a lubricant is the viscosity. Among these properties would be the viscosity of the oil and the National Lubricating Grease Institute (NLGI) grade of the grease for the application. The speed factor can help you determine a variety of lubricant properties, which you can then utilize to select the proper lubricant. This uses the bearing’s median size, also known as the pitch diameter, and the rotation speed to calculate the speed factor. ![]() The second method is known as the NDm value. The first is known as the DN value, which uses the bearing inner diameter multiplied by the speed at which it rotates. ![]() There are two main ways to calculate this factor. The speed factor is a term that helps define the relationship of the speed at which a bearing rotates with the size of the bearing. To understand what the bearing requires in terms of lubrication, you must first learn how to determine the speed factor of a bearing. These components may suffer if a multi-purpose grease is simply applied without much regard to the needs of the bearing. ![]() The same holds true for certain mixers, agitators and blowers. For instance, some pumps that are directly coupled to a motor and have grease-lubricated bearings may spin in excess of 2,000 rpm. While this example paints a picture of a type of machine in most plants (fans), it is common to find high-speed applications in other components as well. Frecuently these bearings are greased with a product that is much too thick for them, leading to the generation of excess heat and shortening the bearing life.īy matching the grease properties more closely to the bearing needs, you can help prolong the life of the bearing. If there are no reduction or increase in pulley size, it is safe to assume the speed of the bearings is quite similar. This fans are frecuently belt-driven at a 1-to-1 ratio from a large electric motor with an average speed of the motor of 1,750 revolutions per minute (rpm). Inevitably, the bearings that seem to be running the hottest are the ones that rotate the fastest.Ī clear example are overhanging fans. During the frequent plant visits of our technicians, they often are asked about the temperature at which bearings should operate.
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