Regarding the issue of high temperatures in the graphite bearings of high-temperature heat transfer oil pumps
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Our company has a KSB high-temperature heat transfer oil pump, model SYT125-200. The temperature of the heat transfer oil is 270 degrees, and the pump has been in use for 6 years. It has received regular maintenance up to now. Recently, it was repaired due to leakage from the mechanical seal. After the pump was reassembled, preheated, and aligned, it was started up, but the following issues arose: 1. The temperature of the graphite sliding bearing at the impeller end of the bearing housing was as high as 220 degrees, whereas the normal value is around 150 degrees. 2. The temperature of the rolling bearing at the motor drive end was as high as 140 degrees, while it should be below 100 degrees under normal conditions. 3. The impeller shows no signs of wear, and the ring seals are in good condition; all the replacement parts used were original manufacturer parts. The pump rotates smoothly both when cold and when hot. I wonder if anyone with experience has dealt with this issue – could you please offer some advice? Question 1: I suspect that the high temperature is caused by either an excessively large or small clearance between the graphite sliding bearing and the pump shaft, which leads to a large amount of hot heat transfer oil entering the bearing housing area. The technical specifications for this pump indicate that the appropriate clearance should be between 0.08 and 0.13. I measured the actual clearance when the pump was cold, and it was around 0.1. I think that a too small clearance may be causing insufficient lubrication for the pump. However, since the pump was disassembled before, the graphite bearings showed no signs of wear. Would increasing the clearance between the graphite bearing and the shaft by another 0.1 improve the pump’s performance? ? ? 、
Hello, there are two reasons of my own that I’d like to share with you: 1. After equipment maintenance, during the initial period of operation, there is an ample supply of grease and lubricant, and at the same time the components are still in the process of adapting through wear and tear; therefore, it is possible for issues to arise more frequently during this initial stage. Increase monitoring and inspections over 2 days to see if there is a downward trend. 2 It is important to check whether the lubricants and greases meet the equipment requirements. At the same time, check whether there is any color change (carbonization) in the lubricating oil and greases, and consider whether the bearing is subject to excessive axial force, resulting in abrasive wear. causing the temperature to rise.
It would be best to show a diagram – how can a bearing housing have both sliding bearings and rolling bearings?