Failure analysis of multi-stage pump with permanent magnet speed regulation
Thread Content
Dear friends, our company has a multi-stage centrifugal pump using permanent magnet speed regulation that failed. When it was found on site, it was vibrating extremely and the anchor bolts were twisted. After disassembly and inspection, it was found that 1. The pump shaft from the pump coupling at the driving end of the pump shaft to the bearing end was worn and bent by 4.5mm. ； 2. The balance plate and balance sleeve are slightly worn, but not locked. ； 3. The driving end bearing gland of the pump is damaged. ； 4. The first-stage impeller and the guide vane wear-resistant ring are worn and adhered, but there is no discoloration due to high temperature. ； 5. The permanent magnet speed regulating bearing seat is damaged, and the overall height is 2mm lower than the pump coupling. ； 6. The tie rod for adjusting the air gap of the permanent magnet speed regulator is broken. ； 7. There is shaft holding at both the front and rear ends of the motor, the front end is slight and the rear end is serious. The rear end bearing chamber was cracked, and the bearing platform and inner cover platform were severely damaged. 8. The DCS trend only has 1 minute of outage time. Please help us analyze the main reasons.
This is all caused by failure to detect and deal with bearing damage in time. First it was the lubricating oil problem, then it was wear and tear, then it was various discomforts,,,, and finally it led to this. Just replace all the damaged items. But the daily inspection work in the future must be done properly, otherwise, similar things will happen again.
Judging from the current situation, can you tell whether the permanent magnet speed regulating bearing or the multi-stage pump failed first? I personally tend to think that the permanent magnet speed-regulating bearing failed first, causing wear and tear on the tie rod that adjusts the air gap. The tie rod drives the air gap to change, and at the same time, a large deviation occurs between the center of the permanent magnet and the center of the pump shaft, causing vibration of the pump and shaft channeling, causing wear of the first-stage impeller of the pump. On the other hand, damage to the permanent magnetic bearing causes excessive load on the motor, causing damage to the motor.
In fact, none of this is important. What is important is how to formulate and implement the on-site equipment management system in the future.
If the maintenance is not timely, the bearing will break first.
Is it normal lubrication, or is the bearing itself defective?
The usual daily inspections were not in place and minor equipment problems were not discovered in time, resulting in a series of chain reactions. It is recommended that regular spot inspections should be strengthened to prevent minor problems from causing major accidents.