Two issues related to self-priming pumps with automatic control
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Question 1: What are the differences between a self-priming pump and a regular centrifugal pump? Explain the differences in their working principles and structures compared to regular centrifugal pumps, and how does a self-priming pump achieve its self-priming capability? Question 2: Is it okay not to install any valves at the inlet or outlet of a self-priming pump? Our factory doesn’t install any valves of that kind! My opinion is that at least a check valve should be installed at the outlet to protect the pump. I welcome fellow enthusiasts to actively discuss this topic and provide answers!
For ordinary centrifugal pumps, if the liquid level at the inlet is below the impeller, it is necessary to fill them with water beforehand before starting, which is very inconvenient. To retain water in the pump, a foot valve needs to be installed at the inlet of the suction pipe; when the pump is operating, this foot valve causes significant hydraulic losses. A self-priming pump is one that does not require priming before starting (although priming is still needed for the first start-up after installation); after operating for a short period of time, it can draw water in on its own thanks to the pump’s mechanism and then begin to function normally. Self-priming pumps can be classified into the following categories based on their working principle: 1. Gas-liquid mixing type (including internal mixing and external mixing types) ； 2. Water ring type ； 3. Jet type (including liquid jets and gas jets). Working process of the gas-liquid mixed automatic control self-priming pump: Due to the special structure of the pump body, a certain amount of water remains inside the pump after it stops operating. When the pump starts again, the rotation of the impeller causes the air and water in the suction pipeline to mix thoroughly, and this mixture is sent to the gas-water separation chamber. The gas at the top of the chamber escapes, while the water at the bottom returns to the impeller, where it mixes again with any remaining air in the suction pipeline. This process continues until all the gas in the pump and suction pipeline has been removed, allowing the pump to achieve self-priming and start pumping water normally. The water ring wheel type self-controlled self-priming pump combines a water ring wheel with a pump impeller within a single housing; the water ring wheel is used to expel gas, thereby enabling self-priming. Once the pump is operating properly, the passage between the water ring wheel and the pump impeller can be blocked using a valve, allowing the liquid inside the water ring wheel to be drained. The jet-type self-controlled self-priming pump is composed of a centrifugal pump and a jet pump (or ejector); it relies on a jetting device to create a vacuum at the nozzle in order to achieve suction.