What Is The Suction Performance Of A Centrifugal Pump

Jun 11, 2025

The suction performance of a centrifugal pump includes the allowable suction vacuum height and cavitation margin. The boiling point of water at atmospheric pressure is 100 degrees Celsius. When water is heated to its boiling point, it requires a lot of bubbles and vaporization. In high-altitude areas, the air is thin, the pressure is low, and the water is boiling below 100 degrees Celsius. Therefore, the evaporation of water is not only related to temperature, but also to atmospheric pressure on the sea surface. When atmospheric pressure drops to a certain level, water can also vaporize at room temperature.
From the operating principle of centrifugal pumps, it can be seen that the reason why centrifugal pumps can suck liquid at the lower part is because centrifugal force is generated by the rotation of the impeller, and the inlet of the pump creates a relative vacuum, resulting in atmospheric pressure on the water surface of the suction tank. Draw the liquid into the center of the impeller along the suction pipe. Under normal circumstances, the atmospheric pressure is about 10.3 meters. (The wave height is zero). If the center of the impeller is an absolute vacuum, excluding the head loss of the suction pipe, then the external atmospheric pressure can only increase by 10.3 meters of water. It can be seen that the height of the pump is limited.
Within the suction height range of the centrifugal pump, the higher the position of the pump device from the water surface, the higher the vacuum degree at the pump inlet, that is, the lower the suction pressure at the impeller inlet. When the inlet pressure of the centrifugal pump drops to a certain value, the liquid will enter the boiling and vaporization under the evaporation pressure at that temperature, and then form bubbles in the liquid activity, filling with steam and gas separated from the liquid. These bubbles enter the impeller together with the liquid. Due to the effect of centrifugal force, the pressure of the liquid gradually increases, causing the vapor in the bubbles to suddenly condense at higher pressures and the bubbles to disappear.
Due to the rapid rupture of the bubble, the surrounding liquid rushes towards the original space occupied by the bubble at a high speed, forming a fierce hydraulic shock, known as water hammer. At this point, the instantaneous pressure of the water hammer can reach 10.3 MPa. If bubbles approach the surface of the impeller, over time, under the impact of water hammer pressure, they will move to the surface of the impeller and cause serious damage. Practice has shown that under the effect of water hammer, honeycomb damage will occur on the opposite side of the blade inlet. Therefore, centrifugal pumps are not allowed to operate under cavitation.