The temperature of the rear bearing of the multi-stage centrifugal pump is excessively high
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The facility has a multi-stage centrifugal pump for transporting liquid propane. When installing the equipment, a 1-backup-1 configuration was used, and the B pump worked without any problems. However, after pump A was started, the temperature of the rear bearing remained extremely high, reaching 70°C after about 40 minutes. The manufacturer came to perform repairs in July 2016; at that time, the gap between the balance disk and the balance plate was adjusted to 0.04 mm, and the gap of the rear bearing was set to 1.5 mm, but this did not help at all. At the end of February this year, we switched to another manufacturer; the clearance of the balance disk was adjusted to 0.06 mm, an increase of 0.02 mm, while the clearance of the rear bearing was set to 0.55 mm in accordance with the manufacturing standards. I’m a bit confused; it’s understandable that the gap in the balance disc increases. The pressure difference between the pressure behind the impeller and the pressure in the balance chamber decreases, which reduces the thrust exerted toward the back. As a result, the bearings at the rear end experience less stress and generate less heat. But logically, if the temperature is high, shouldn’t the bearing clearance be increased? Why did the temperature stabilize around 65°C after this manufacturer made the adjustment in a smaller magnitude? Seeking answers and discussions from fellow sea lovers! ! !
The reason for adjusting the balance disc gap larger can be understood based on its structure, but what is the reason for the bearing gap? The manufacturer also didn’t answer me; they just said it would be fine once the conditions on site improved. Let’s discuss it later
The gap you see becoming smaller is actually due to the bearing’s clearance having been adjusted to the optimal level. Don’t focus only on the gap, but also on the relative position.
An increased clearance between the balance disk and the drum indicates that the pump’s hydraulic balance is not good at the moment； The bearing clearance can be adjusted according to the standards; as long as the clearance of the balance disk is properly set, hydraulic balance will be maintained and the bearings will not get damaged. Adjusting it to 1.5 for the first repair was an inappropriate approach.
This post was last edited by Meng Cheng from Longgang Pump Industry on 2017-3-14 at 11:47. A bearing clearance of 1.5 mm is indeed too large! I’ve never seen one this big! 0.55 is acceptable! I think my understanding of the balance disc is not quite correct; you can take a look at a post on the forum about balance drums – it explains everything very clearly!
The smaller the gap in the balance disk, the higher its balancing efficiency; if the gap is too large, it fails to provide any balancing effect, or its effect is minimal. Additionally, the horizontal installation of the entire equipment is also an item that needs to be checked, as it can also lead to bearing problems.
Which bearing clearance is the author referring to?
Are your bearings double-row? Are there bearings that can withstand axial forces? What do you mean by this 1.5mm gap? Is it the gap with the end cover? There’s no such large gap; what’s the use of bearings then?
Some pump designs are general in nature; it also depends on the medium
Come and learn*, study hard* and make progress every day
I understand that with this pump, adjusting the gap between the balance disc and the balance seat is mainly to avoid conflicting with the thrust bearing. If there are no thrust bearings, the balance disk will automatically find its balanced position (with a clearance of around 0.05–0.15). As for the thrust bearing clearance, it is mainly used for positioning and to prevent seizure due to expansion