What happens when a centrifugal pump operates at low flow rates, and why?
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As the title suggests, I’m seeking a detailed explanation from experts
During operation at low flow rates, the radial force is high, resulting in significant pump vibration. If the flow rate falls below the minimum value required for thermal control, the medium will vaporize due to the increase in temperature, causing the pump to become unusable.
When the flow rate of a centrifugal pump is too low, there isn’t enough cold fluid to carry away the heat generated by the friction between the impeller and the fluid being pumped. As a result, the pump heats up, its temperature continues to rise, and eventually the pump becomes vacuumed. Vacuum conditions can lead to increased pump vibration, which in turn raises the temperature of the lubricating oil in the bearing housing and can cause the shaft to seize, as well as damage to the seals. When the temperature of the lubricating oil rises, its lubricating properties decrease; if the temperature gets high enough, ignition can occur. If it is an oil pump, leakage caused by damaged seals can also lead to a fire.
During operation at low flow rates, the radial force is high, resulting in significant pump vibration.
1. The pump is overheating or suffering from cavitation. The reason is the increase in liquid temperature caused by power losses inside the pump ； 2. The pump generates vibration and noise. The reason is the formation of vortices within the rotor flow channel and secondary recirculation at the rotor outlet ； Liquid drainage from the rotor flow channel ； Fluctuations in pressure occur within the pump and pipes ； Pumps with hump characteristics can also experience surge, leading to vibration and noise ； 3. Bearings and bearing housings are prone to damage. Operation at low flow rates generates radial forces (especially in single-screw pumps), while the axial forces also increase.