A really tricky on-site problem!

Thread Content

The device was supposed to be tested tomorrow, but we encountered a tricky problem today. A vortex pump with a flow rate of Q=2000 L/H and a head of 112 M is required to transport 3 DN15 pipes to 3 reactors. Each pipeline is equipped with a metal flow meter for measurement (flow rate of 200 L/H per unit) ； The reactor pressure is 4 kilograms; the pump is running, and the pressure gauge shows 8 kilograms. However, the flow rate indicated by the metal flow meter gradually decreases. When the valve is opened wider, the flow rate drops again within less than 10 minutes. After adjusting it for an hour with no success, I became frustrated and started to suspect that there was a problem with the metal flow meter. I replaced it with a rotameter, but the same issue persisted. Then I suspected that there might be a problem with the check valve downstream of the flow meter, so I removed that valve to allow the fluid to flow out through the flange, and that’s when I identified the problem: the fluid (water) contained bubbles. By opening the bypass valve wider, the bubbles disappeared, but the flow rate still didn’t decrease. The pressure, however, was only 2 kilograms, which contradicts the required pressure of at least 5 kilograms. When the bypass valve was closed or adjusted to a narrower opening, the pressure rose above 5 kilograms, but bubbles continued to form in the fluid, resulting in inaccurate readings from the flow meter ； The bypass was turned on; there are no bubbles now, and the pressure is only 2 kilograms. I’m not sure what to do. It’s possible that the flow rate chosen for the pump was too high. Without replacing the pump, it’s possible to avoid bubbles while still ensuring accurate readings from the flow meter ； The pressure is again over 5 kilograms – do anyone have any good suggestions? What phenomena occur when a centrifugal pump operates at low flow rates: 1. The temperature of the liquid inside the pump rises. 2. The pump will experience surging, vibration, and noise generation. 3. Operating the pump at a low flow rate for an extended period can also cause some of the liquid to vaporize, making it difficult to draw in liquid. 4. The efficiency of the pump decreases, resulting in increased energy consumption. Point 3 exactly matches what’s here; it’s so frustrating! This post was last edited by spc1212 on 2009-3-12 18:08.]