Bearing sealing in high-dust environments

The bearings of your equipment aren’t exposed, are they? The bearings of ordinary equipment are usually located inside the equipment housing and within the bearing housings ； There is no such thing as a sealing issue as you mentioned! ! This post was last edited by lxzzl on 2008-8-18 16:45]

There are two types of such seals: one is a mechanical seal, which is the same as an ordinary mechanical seal； Another option is to use compressed air for sealing. Create a chamber separated from the bearing, and feed compressed air into it. This post was last edited by lxzzl on 2008-8-18 16:44]

If it is for design purposes, it is recommended to add a felt ring seal on the outside of the bearing holder to prevent dust from entering.

Sealing of bearings in high-dust environments Author: Hua Yikang Available for online search

Since my level is not high enough to upload files, I converted the PDF documents into Word format and pasted them for upload. The transformation might not be ideal; sorry! Sealing of bearings in high-dust environments by Hua Yikang, Huaxin Cement Co., Ltd., Huangshi, Hubei Province (435002) ◇ Technical Improvement Exchange ◇ Due to the limitations of the process flow (see Figure 1), the primary fan of Kiln No. 3 in our company’s firing workshop draws its air supply from the recycled air from the coal grinder. Therefore, the wind temperature is 10–20 °C higher than that of the primary air in Kilns No. 1 and No. 2; the maximum temperature in summer reaches 60 °C. The wind contains a large amount of coal dust with a fine particle size (the residue on a 01080 mm square-hole sieve is ≤12%). Meanwhile, positive pressure occurs in areas where negative pressure should be generated by this fan (such as the air inlet, and at the packing around the shaft and fan casing). The service life of the bearings of the primary fans in Kilns No. 1 and No. 2 is 4 to 5 years (under 24 hours of continuous operation), while that of the bearings of the primary fan in Kiln No. 3 is at most 8 months; generally, it is 3 to 4 months, and in cases where the installation is poor, the bearings may only last for 1 month. Over the past year, the operating time of this fan has become increasingly shorter, and bearing failures have occurred more frequently than in previous years. Figure 1: The primary air supply process for Kiln No. 3. Based on the damage observed in the bearings of these fans, in most cases it is the retainer that wears out, and after the rollers and raceways are worn, the rollers come loose from the raceways. Among the bearings used, copper solid cages have a longer service life than stamped cages; however, the main forms of damage observed recently are seizure, burning out, and discoloration of the rolling elements. Based on the operating conditions and environment of the primary fan in Kiln No. 3, we conducted a thorough inspection and analysis of the lubrication of the fan bearings, the load applied to them, as well as the bearing assembly and its fit. It was determined that the main factors affecting the service life of the bearings in Kiln No. 3’s primary fan are, in order: ① Lubrication and sealing conditions; ② Radial clearance; ③ Operating temperature. Structurally, the bearings of this fan were originally sealed with felt. Due to poor sealing at the fan’s packing area, the positive pressure inside the fan caused coal dust to leak outward. As can be seen from Figure 2, the leaking coal dust targeted the bearing end caps of the fan, making it easy for the bearings to become contaminated by coal dust. Due to operation at high temperatures for extended periods, along with coal powder entering the bearings and causing the lubricant to harden, bearing lubrication fails and the bearings get damaged. From the perspective of assembly, by checking the fit dimensions between the bearing housing and the outer ring of the bearing, as well as the clearance of the bearing after assembly, we found that the clearance after assembly is only 0102–0105 mm. Given the actual operating conditions of this fan, along with the fact that high rotational precision is not required, it is likely that the clearance will be essentially zero in actual operation (when the temperature rises). Figure 2: Bearing sealing structure before and after improvement. Based on the above analysis, we first addressed the sealing issue by improving the lubrication conditions, and finally adopted the sealing scheme shown in Figure 2, thereby completely resolving the problem of bearing contamination. Secondly, during assembly, we select bearings with a larger radial clearance, use a looser outer ring fit (radial clearance of 0105 mm), and apply Loctite 660 between the outer ring of the bearing and the bearing housing. This ensures that the cold-state operating clearance of the bearing after assembly is between 0115 and 0118 mm, thereby meeting the requirements for higher operating temperatures. Thanks to these improvements, the service life of the fan bearings has been significantly extended. Since October 1994, more than three years after the bearings were replaced, no failures related to bearing damage have been observed, which ensures a higher operational rate for the cement kilns. (Edited by Wang Yanli)

If you want the information, you have to look for it online by yourself! In fact, taking the time to visit a device manufacturing plant and learning about it firsthand is far more valuable than any information available elsewhere

One type is a mechanical seal, similar to ordinary mechanical seals; the other type can be sealed using compressed air. Create a chamber separated from the bearing, and feed compressed air into it.

Well, you can refer to the sealing methods used in jet milling equipment, such as gas sealing and labyrinth sealing, etc

A labyrinth seal can be used, fed with compressed air or nitrogen

I would like to inquire about AESSEAL’s MAGTACT and LABTACT products, which are designed specifically for bearing sealing purposes. They have been patented in both Europe and the Americas. However, their price is quite high; those with a shaft diameter of 50 cost around 2000 yuan