Help, why is the pressure after the pump continuously dropping?
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The flowchart is as follows. As soon as the pump starts, the pressure reading is normal at the moment of startup, but it then continues to drop, reaching 0.02–0.03 MPa after about 10 minutes. 1. There is a Y-type filter in front of the pump; the filter is very clean. The filter screen in front of the pump was also removed and it was clean as well. 2. The pump was emptied both before and after pumping, confirming the absence of air. 3. By tapping, it was found that the pipe section before the spiral plate heat exchanger produced a deep sound, while the pipe section after the spiral plate heat exchanger and up to the tee joint emitted a clear sound; water flowed out after removing a blind flange in that pipe section.
What’s the status of the equipment at the pump inlet? It is possible that the vent valve on the inlet side equipment is not open; the tank is sealed. As the pump draws in liquid, the liquid level drops, and the pressure in the gas space decreases, which in turn causes the pressure at the pump outlet to drop.
The exhaust valve in the pump inlet tank is open, and the liquid level is around 60. Do you have any further comments? There’s one more thing I forgot to mention: the pumps started working normally at first, but after about ten minutes the liquid level dropped to almost zero; this happened with both pumps
It is recommended that, in the case of a centrifugal pump, use the pump’s outlet valve to maintain the pressure before the valve at the pump’s rated pressure (head). Use the pump outlet valve as a boundary, and then determine whether it is a problem on the rear side or a problem with the pump. It’s worth a try.
As the pump operates, the liquid level drops, which in turn causes the inlet pressure to decrease; as a result, the outlet pressure also decreases. It is estimated that the tank is below the pump, and the exhaust valve is relatively small; it is recommended to raise the liquid level in the tank and keep the exhaust valve fully open. Also, check again whether there is any blockage in the exhaust valve; in northern regions, where temperatures are below zero at night, water vapor can freeze around the exhaust valve.
Okay, I’ll go and take a look tomorrow. Thank you
Also, there is the liquid level before the pump; a higher level results in a greater flow rate
The pressure after the pump has dropped; is the pressure before the pump normal? If no water can be drawn in ahead of the pump, there is definitely no pressure behind it.