In demanding applications like mining, motors often operate in harsh conditions where heat is a major factor. Bearing performance under these conditions can make or break equipment uptime, reliability, and operating costs. That’s where bearing steel selection becomes critical – and why understanding S1 is still relevant today.
What is S1 Bearing Steel?
S1 is a special heat-resistant bearing steel designed for high-temperature applications. They were once the go-to choice for motors and equipment running at elevated temperatures – like those used in mining and aggregate operations – because they offered improved hardness retention and dimensional stability when temperatures climb.
S1 steel: Known for excellent performance at temperatures up to around 392°F. It was commonly used in electric motors where excess heat was a concern.
Why S1 is Less Common Today?
While S1 bearings are still available and many motors still use them, they are not as widely specified as they once were. Advances in standard bearing steel quality, heat treatment methods, and lubrication technology have closed the gap – allowing many modern bearings to perform well at temperatures that previously required specialty steel.
There are still motors that will have S1 on the bearing name plate. Depending on the bearing size, that bearing could no longer be available in S1, but you may be able to replace it with today’s high-quality standard bearings with improved manufacturing and lubrication for the same service life.
Key Considerations for High-Temperature Bearings
Regardless of whether you use S1 or standard bearing steel, a few best practices can help you get the most life from your bearings in high-heat applications.
- Check Internal Clearance: High temperatures cause bearing expansion. Choosing the correct internal clearance (often C3 or greater) prevents preloading and premature failure.
- Use High Temperature Grease: Standard greases may break down quickly in heat. A premium, high-temperature grease is a must for mining motors.
- Follow Proper Fitting Practices: Excessive interference fits generate more heat and reduce clearance – a common cause of early bearing failure.
- Monitor Operating Conditions: Bearing temperature trends are a good early warning sign. A steady increase may indicate lubrication breakdown or excessive load.
The Bottom Line
With today’s improvements to bearing steel and lubrication, S1 is no longer the automatic choice for high-temperature applications, but it still has a place in legacy mining equipment and other applications. Understanding the difference between S1 and modern steel allows you to make informed decisions that maximise reliability and uptime.
Source: Bartlett Bearing Company, Inc.
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