The pump resonance issue from last time still hasn’t been resolved?? Need help
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It is a DL vertical multi-stage centrifugal pump with a flow rate of 260 and a head of 70. The unit operates in a one-main-pump-plus-one-backup-pump configuration. After three months of stable operation, resonance occurred in the main pump; when the main pump was running, vibrations appeared in the entire piping system of the unit as well as in the backup pump. During the first maintenance attempt, the outlet valve of the main pump was closed, and no resonance was detected while the pump was running. When the outlet valve was slowly opened again, the resonance in the main pump increased. The technicians concluded that the outlet valve was the cause of the vibrations and considered replacing it. I would appreciate it if experts could help determine whether this conclusion is reliable, as replacing the outlet valve is a rather complicated and difficult process. Thank you for your assistance. The above is a request for help posted 1 month ago; thank you to all experts for their assistance. The problem still hasn’t been solved; here is a brief description of the repairs carried out over this month. The pump bearings and motor bearings were all replaced, as well as the coupling; however, vibration persists. It is now understood that this water pump is started using an inverter; it operates at a low frequency of 30 Hz from 8 a.m. to 8 p.m., resulting in significant vibration. From 8 PM to 8 AM, it operates at 50Hz with no vibration.
“From 8 am to 8 pm, it operates at a low frequency of 30 Hz, with noticeable vibration. From 8 PM to 8 AM, it operates at 50Hz with no vibration. ”Is this sentence written backwards? ? In my analysis, after the fluid exits the pump, it impacts the elbow, and the resulting force induces resonance; I recommend strengthening the supports for the outlet pipeline as well as the bolts that connect the pump base to the foundation. .
Why do you think it’s written backwards? I think it should be that there is no vibration when operating at 30HZ, while vibration is noticeable when operating at 50HZ? At low speeds, the flow rate is low; doesn’t this instead make it easier to end up with insufficient suction at the inlet? Has the original poster tried running it at 50HZ all the time, or adjusting it through the inlet and outlet connection wires?
Flexible rotors need to avoid the first-order critical speed
This post was last edited by CHANGBAISHI on 2020-8-4 08:23. Check the quality of the basic secondary grouting, the stress on the anchor bolts, and also whether the parameters of the pump itself as well as those of the upstream and downstream systems meet the requirements for using the pump
Check whether there is stress in the outlet piping and pump body, or whether the pipe supports lack sufficient expansion capacity, resulting in resonance!
It’s not written backwards; it is indeed low-frequency resonance. A check valve – gate valve should be installed 1 meter away from the outlet.
It wasn’t written backwards; it’s a low-frequency resonance issue that only appeared after 3 months of normal use, and the backup pump works without any problems
What are the values for a rotational speed of 30Hz and the first and second critical rotational speeds of the rotor?
My first instinct was the same. ;P