Discussion on the problem of outlet flow fluctuation of small flow and high lift centrifugal pump.

This post was last written by Andrew_Edited by PWIL on 2020-5-26 17:06 The pump is on and on standby. Both pumps have fluctuations. There are two flow meters at the pump outlet, and random fluctuations in the total flow rate at the outlet are detected. For example, the pump outlet flow rate drops from 22t/h to 18t/h and then returns to 22t/h. The reaction time is about 2 to 5s. Since the interlocking instrument involved in the device has caused the device to stop, we set the delay time of the interlocking instrument to 5s. For details, please see the attachment. Our own early analysis showed that it was suspected to be caused by the saturated vapor pressure of the medium. However, after adjusting the process and observing later, we found that the phenomenon still existed. At present, we suspect that it is because there was a problem with the original design and selection of this small-flow high-lift pump, or because there was no choice. The performance curve of the centrifugal pump selected by the designer has a hump. What do you think specifically? If there is a hump, can it be eliminated through modification? Have you had any cases? And how did you avoid the interlocking problems caused by such fluctuations?

There must be some string volume. The total string volume of the rotor is 8mm, and after installing the balance plate, it is 4mm. This is the information given by the manufacturer.

Can you take pictures of your two meter measuring points? I suspect that the pressure point settings on your side are unreasonable, especially the measuring points that are sensitive to flow!

What impact will the instrument measuring points have? We are in the south, and the lowest temperature in winter is about 5°C. When the temperature is low, the fluctuations of pipe blockage are continuous and not instantaneous. At first, it was because the heating wire was not added, the condensation point of the cracked tail oil was high, and the fluctuations were caused by pipe blockage. This problem has been solved and eliminated after we added the heating wire.

After installing the thrust bearing, measure the deflection by 0.5mm.

Sure enough, it is basically consistent with what I thought... Although your setting conforms to the specifications of the pressure point of the instrument, it is more reasonable to set it at an upward angle of less than 15° for flow measurement of media that may have gas overflow. There are many such settings in actual sites. If the angle is too large, it is easy for overflow gas to accumulate in this part. When it accumulates to a certain amount, it will fluctuate. A small release will cause small fluctuations, and a large release will cause large fluctuations. And as the flow rate, pressure, and temperature change, its release may change irregularly.

If the angle is too large, it is easy for gas to accumulate in this part. Hello, can you explain it in detail? I didn’t understand what you said :P

This post was last written by Andrew_PWIL edited on 2020-5-28 15:50 "The angle is too large, and it is easy for gas to accumulate in this part." Can you be more specific? Is this statement based on experience or does it come from a certain standard? However, there are two flowmeters before and after the outlet of our pump. After the previous flowmeter fluctuates instantaneously, the flowmeter 2 seconds later fluctuates with the same amplitude. Is it a bit far-fetched to say that gas accumulation is a bit far-fetched? We have analyzed it before and suspected that the medium contains liquid or water-in-oil vaporized aggregates under certain conditions. Later, we adjusted the process to no avail.