Lubrication Limitations and Equipment Requirements for Cylindrical Roller Bearings

Information Summary:

Lubrication Limitations:

In greased applications, the starting torque of rolling bearings typically increases significantly at lower temperatures. The starting torque is not primarily dependent on the grease's consistency but is usually determined by its rheological properties, which dictate how the grease flows and shears under initial force before rotation begins. The high-temperature limit of a grease is generally defined by the base oil's thermal stability, oxidation stability, and the effectiveness of antioxidants. At elevated temperatures, grease can oxidize, harden, and form deposits that impede lubrication and lead to bearing failure. Please refer to the "Lubrication" section on page 39 for detailed information on lubrication limitations.

Equipment Requirements:

Equipment designers must evaluate the impact of temperature on equipment performance. For instance, precision machine tool spindle bearings can be highly sensitive to thermal expansion, which can cause preload changes and compromise machining accuracy. For certain spindles, special attention is required when the operating temperature exceeds the ambient temperature by 20°C to 35°C.

Most industrial equipment can operate at reasonably high temperatures. For example, transmission gears can withstand temperatures up to 93°C. Equipment such as gas turbines can operate continuously at temperatures above 100°C. However, during prolonged operation at high temperatures, fits may be affected if the shaft and housing are not properly machined and heat-treated, potentially leading to loosening and catastrophic failure.

Although bearings can operate normally at temperatures up to 120°C, a maximum temperature range of 80°C to 95°C is often more practical. Higher operating temperatures increase the risk of temporary thermal peaks, raising the possibility of damage to TIMKEN bearings. These thermal spikes can degrade lubricants and anneal bearing components, reducing their hardness and load-carrying capacity. Prototype testing based on the specific application is recommended to determine the suitable operating temperature range. Equipment designers should weigh all relevant factors, including ambient conditions, duty cycle, and cooling methods, to finalize the required operating temperature.