Pneumatic diaphragm pump is a pneumatic positive displacement self-priming pump, pump the right to explain the diagram shows the pump is not self-priming flow mode before the first pump. Figure 1: Air is compressed into the back of diaphragm A via a gas valve and is squeezed by the diaphragm. This air-driven approach eliminates the mechanical stress of typical piston drives, significantly extending the life of the diaphragm. When the compressed air pushes the diaphragm A away from the center body, the diaphragm B at the other end is simultaneously pulled toward the central body by the connected central shaft. At this time, the air on the back of the diaphragm B is discharged to the outside of the pump body through the outlet. This causes chamber B to be evacuated so that the fluid can be forced by the inlet manifold to push the valve ball away from the valve seat to allow fluid to freely enter chamber B until it fills up due to the outside atmospheric pressure. Figure 2: When the air-squeezed diaphragm A reaches its limit of displacement, the air valve guides the air to the back of the diaphragm B, which also presses to push it away from the center body and the attached diaphragm A pulled back to the center body, at this time the diaphragm B driven hydraulic pressure generated by the inlet valve ball back to the valve seat, while the outlet valve ball from the valve seat so that the fluid can be squeezed out of the pump body from the outlet. Diaphragm A is pulled back to the central body. This action makes chamber A in a vacuum state, so that by atmospheric pressure, the fluid can be pumped from the inlet manifold to the A-chamber until it fills up. Figure 3: When the motion of the diaphragm is completed, the air valve again directs the air to the back of diaphragm A while diaphragm B acts as an air vent. When the pump is returned to its original start-up condition, both diaphragms within the pump each perform an air or fluid discharge. This constitutes a circulation pumping process. Depending on the condition of use, the pump reaches its self-priming status by several full cycles of pumping action.