Status of the outlet valve before starting the submersible pump
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The water pumps used for irrigating fields in rural areas are submersible pumps, but they lack an outlet valve; water starts flowing as soon as power is applied, without the need to fill the pump first, which means the pump starts operating under load. However, for the submersible pumps in chemical plants, it is necessary to fill the pump before starting it, and the outlet valve must also be closed; the outlet valve should only be opened after the motor has started running, otherwise no flow will occur! May I ask why?
Submersible pumps and self-priming pumps are generally used. 1. When there is air inside the suction pipe of the water pump, the negative pressure (vacuum) generated during the pump’s operation is utilized, along with atmospheric pressure, to lift the water from a level lower than that of the suction port, which is then discharged through the pump’s discharge end. No “guiding water” is needed before this process. A pump with this capability is called a “self-priming pump”.
A submersible pump is one in which the impeller is submerged below the liquid surface, and it does not require priming. As for the outlet valve, it is best to start the pump with it closed; if the motor has sufficient capacity, it is also possible to start the pump with the valve open