Pneumatic diaphragm pump is a pneumatic positive displacement self-priming pump, the right to explain the pump 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, squeezing the fluid chamber from the diaphragm. This air-driven approach frees up 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 manifolds away from the valve seat by the action of atmospheric pressure outside to allow fluid to freely enter chamber B until it is filled. 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 against it to push it off the center body and at the same time connects the attached diaphragm A pulled back to the center body, at this time the diaphragm hydraulic pressure generated by the drive B will push the valve ball back to the valve seat, while the outlet valve ball from the valve seat so that the fluid can be squeezed from the outlet of the pump body. 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 movement of the diaphragm is completed, the air valve again directs the air to the back of the diaphragm A while the 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.