On a large induced draft fan, which bearing is likely to show wear first?

In a large induced draft fan, the inboard bearing is likely to show wear first due to its role and the conditions under which it operates. The inboard bearing, being positioned closer to the motor and the drive components, supports the weight of the shaft and fan assembly as well as absorbs the forces from the fan's operational dynamics, including vibrations and thermal expansion. This location often makes it more susceptible to wear because it experiences more axial and radial loads than the outboard bearing.

Additionally, if a misalignment occurs or if there are any issues with lubrication, the inboard bearing is likely to be affected more directly because of its proximity to the source of possible mechanical problems. The thrust bearing, while essential for managing axial forces, does not generally wear down first under typical operation unless specifically impacted by operational malfunctions. Similarly, the roller bearing, depending on its design and placement, may encounter wear based on load and usage, but typically the inboard bearing faces a cumulative load that makes it more prone to wear initially.