What type of check valve should be installed before self-priming pump

WFB non-sealed automatic self-priming pump is mainly composed of pump body, impeller, pump cover, guide vane, auxiliary impeller, pump shaft, connecting frame, electric air control valve and other parts. · The pump body is composed of suction chamber, liquid storage chamber, gas-liquid separation chamber and other parts. After pump in the normal starting, impeller suction chamber in the liquid and inlet line of air suction, liquid mixed gas under the action of the centrifugal force of high-speed rotating impeller by the guide vane tossed into the gas-liquid separation chamber and reduced due to the velocity of a sudden, the proportion of gas and liquid is different, lighter gas is separated from the mixture and discharge pump, The degassed liquid re-enters the working chamber and the air inhaled from the suction pipe inside the impeller is mixed again. Under the action of the rotation of the impeller, the pump body entrance forms a certain vacuum degree quickly, so as to achieve the purpose of self-priming. Because the pump has a unique exhaust function, so the pump can transport liquid containing gas without the installation of the bottom valve. The pump is equipped with "electric air control valve" when running, the control valve is closed to achieve sealing; The control valve is opened after shutdown, destroying the vacuum in the suction pipeline, preventing the liquid in the pump chamber from flowing out of the suction pipeline due to cylinder suction, so that enough liquid is saved in the pump chamber to continue to complete the self-priming process, so as to achieve the "first drainage, permanent self-priming".