The issue of low opening degree of the outlet valve in multi-stage centrifugal pumps
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Since the process flow rate does not require that much, the opening degree of the outlet valve of the multi-stage centrifugal pump is relatively small. The rated flow rate is 25 cubic meters per hour, the designed head is 200 meters, the outlet flow rate is 8–9 cubic meters per hour, and the outlet pressure is 3 MPa. Will this have an impact on the balance disk and the mechanical seals at both ends? Are the large pressure fluctuations in the balance tube caused by this?
Yes, the flow rate in the balance tube is high and the flow velocity is fast; this can lead to overheating and localized vaporization. It’s possible to check the temperature of the balance tube – when the temperature is high, there will definitely be pressure fluctuations, which may even result in the pump being emptied of fluid. Reopening the tank for reflux perfectly solves this problem.
There is certainly an impact: when the pressure at the high-pressure end of the pump chamber exceeds the rated value, the axial force on the balance disk increases, which affects the lifespan of the bearings； The pressure in the sealing chamber is also higher than the rated value, resulting in a reduced sealing lifespan ； The pressure in the balance tube fluctuates. It is best to add an export return line and use a large loop, rather than a small loop! !
It is already near the minimum flow point. Pump stability will decline, vibration will increase, and temperature will rise. The balance disc has an impact, but it is not the main issue. It is mainly vibrations caused by hydraulic forces, etc., which affect the overall lifespan of the unit. It is recommended to increase the traffic.
There is a definite impact; it is necessary to stop the pump in a timely manner when high flow rates are not required, or to increase the outlet reflux； I have also encountered the same users; moreover, in an effort to simplify things, operators press the inlet valve to start the multi-stage pump, and the balancing device gets damaged within a few days. :L
Thank you\ud83d\ude4f
Thank you\ud83d\ude4f