【Haichuan Illustrated Chemical Equipment】 Series Posts -- What are the considerations regarding the installation height of centrifugal pumps?

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Get to know the equipment, understand it, and make good use of it. [Haichuan’s Illustrated Guide to Chemical Equipment] series posts: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5719196. Everyone is welcome to participate in the discussions. ----------------------------------------------------------- The installation height (Geometric Suction Head) of a centrifugal pump is one of the most critical parameters in the design of fluid transfer systems, and it tests an engineer’s skills to the fullest. If the installation height is set incorrectly, this pump may not be able to draw in even a single drop of water, or its impeller could be completely destroyed after just a few hours of operation. At the heart of all these considerations lies a fluid dynamics phenomenon: cavitation. 1. Why can’t a pump lift water to an infinitely high level? In everyday thinking, we often assume that a pump sucks water upward. But from thermodynamic and fluid dynamics perspectives, a pump has absolutely no ability to \"suck\"; water is forced into the pump by the external atmospheric pressure (or the positive pressure in the tank). As the centrifugal pump rotates, the center of the impeller (the impeller eye) throws the fluid inside outward, thereby creating a low-pressure area. At this point, the atmospheric pressure on the liquid surface, being higher than the pressure at the center of the impeller, forces the liquid into the pump along the suction pipe. At standard atmospheric pressure (about 101.325 kPa), the theoretical maximum height to which water can be lifted is approximately 10.33 m. But in reality, the actual installation height is far from reaching this theoretical value; it is usually strictly limited to between 4 m and 6 m. The reason is that we must account for two fatal \"losses\": pipeline friction loss (hf): the energy consumed by the fluid as it rubs against the pipe walls, passes through valves and elbows in the suction pipeline. Vapor pressure of the liquid (Pv): This is the most critical variable. All liquids have the tendency to boil and vaporize at specific temperatures. The higher the temperature, the easier it is to vaporize. If the absolute pressure at the center of the pump impeller drops below the saturated vapor pressure of the liquid at that temperature, the liquid will instantly \"boil\" at room temperature.