**High Temperature Adaptability of NTN Bearings**
NTN bearings are known for their reliability and performance in a wide range of applications. One of the key factors that determine their suitability for specific environments is their ability to withstand high temperatures. The heat treatment process used for NTN bearings with an outer diameter smaller than 240mm ensures stability at temperatures below 150°C. However, for operating conditions above 150°C, special heat treatment is required.
These high-temperature-resistant NTN bearings are typically marked with suffixes S1 through S4, following the DIN 623 standard. Here's a breakdown of the temperature ranges:
- **S1**: Maximum operating temperature of 200°C
- **S2**: Maximum operating temperature of 250°C
- **S3**: Maximum operating temperature of 300°C
- **S4**: Maximum operating temperature of 350°C
For NTN bearings with an outer diameter greater than 240mm, they generally maintain good performance at temperatures below 200°C.
In addition to metal bearings, NTN also offers bearings made from glass fiber-reinforced nylon 66. These are ideal for applications where the operating temperature does not exceed 120°C. They are usually lubricated with oil, and if the oil contains additives, it can reduce the lifespan of the cage. Moreover, when the temperature exceeds 120°C, the aging of the lubricating oil can also shorten the life of the bearing components. Therefore, regular inspection and timely replacement of the lubricant are essential.
Sealed NTN bearings rely on the grease filled inside them for lubrication and sealing. The maximum allowable temperature depends on the type of grease and the sealing mechanism. The sealed bearings are typically filled with high-quality lithium-based grease, which can tolerate short-term exposure up to 120°C. However, once the operating temperature reaches 70°C or higher, the grease’s service life begins to decrease significantly.
If the bearing is expected to operate frequently at high temperatures, it is recommended to use specialized high-temperature grease and heat-resistant sealing materials. Standard contact seals are limited to a maximum operating temperature of 110°C. If high-temperature sealants are used, such as fluorinated materials, it's important to note that these can emit harmful gases and smoke when exposed to temperatures above 300°C. In such cases, it is advisable to use a welding torch for disassembly to avoid damage.
Proper maintenance and selection of appropriate materials are crucial for ensuring the longevity and performance of NTN bearings under extreme conditions. Always refer to the manufacturer's guidelines and consult technical support when dealing with high-temperature applications.
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This article was originally published on China Bearing Network. For more information, visit [http://www.chinabearing.net](http://www.chinabearing.net).
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