An Introduction to Failure Modes of Sliding Bearings in High-Temperature Box Fans

An Introduction to Failure Modes of Sliding Bearings in High-Temperature Box Fans

In addition to the propeller and motor, bearings are a critical component of high-temperature box fans. These sliding bearings are classified as either self-lubricating or pressure-lubricated, and they are prone to failure over time. Here is an overview of the failure modes: 1. Corrosion in High-Temperature Box Fans 1. Corrosion-related failures are primarily caused by chemical reactions between the environmental medium and the bearing working surfaces, as well as the formation of chemical reaction byproducts such as oxide films on the bearing surfaces. 2. Premature failure of sliding bearings caused by surface corrosion in high-temperature box fans is referred to as sliding bearing corrosion failure. 2. Fatigue Failure 1. Fatigue failure of sliding bearings can result in spalling, which may appear as lumps of varying sizes, scattered spots, or pitting. These fatigue spalling defects have two characteristics. ① Fatigue spalling frequently occurs near the interface, with traces of alloy residue at the spalling site and irregular edges around the spalled area. ② Fatigue spalling exhibits no symmetrical pattern and is distributed irregularly. 2. The mechanisms of fatigue failure primarily involve the following three aspects. (1) Alternating stresses lead to damage on the bearing surface. ② Soft-phase corrosion and permeation are causes of fatigue. ③ Fatigue damage characteristics resulting from thermal effects. Third, wear and failure in high-temperature box fans, as well as wear in sliding bearings, can be categorized into two scenarios. ① Normal wear is caused by starting and stopping, small foreign particles in the lubricating oil, and rough shaft surfaces. ② Normal wear on bearings is minimal and proportional to the duration of use. If wear accumulates to a certain extent, the clearance between the shaft and the bearing increases, rendering the bearing sleeve unusable. In other words, once the service life is reached, repair or replacement is required. ③ Abnormal wear and premature damage to the bearing sleeve. Fourth, cavitation failure 1. Cavitation, known as cavitation, is essentially a cavity that appears on the bearing working surface under the action of gas. 2. The location of cavitation in the sliding bearings of high-temperature box fans is always closely related to the geometric positions of the oil grooves and oil holes in the oil circuit system. These shapes can be punctate or spot-like, or they can form bands or dendritic patterns known as symmetrical distributions. Cavitation typically begins near areas with higher centrifugal forces. 5. Fretting Corrosion and Wear Fretting corrosion and wear frequently occur on tightly fitted components subject to vibration sources. In the case of sliding bearings, fretting corrosion and wear often occur on the outer surface of the bearing steel backing and the inner surface of the bearing housing bore. Failure of the sliding bearings in high-temperature box fans results in machine damage. To prevent this phenomenon, measures can be taken to address the five key factors: wear, fatigue, corrosion, cavitation, and fretting corrosion.