A diaphragm 泵 (also referred to as a Membrane pump) is a positive displacement pump that uses a combination of the reciprocating actions of a rubber, thermoplastic or teflon diaphragm and suitable valves on either part of the diaphragm
A dual diaphragm is a positive displacement pump which utilises two flexible diaphragms that reciprocate back and forth, creating a temporary chamber, which both allures and expels liquid through the pump. … The two diaphragms that are linked by a shaft through 
the center section where the air valve is situated.
Though it depends upon the pump and application, a positive displacement pump, is generally a Air Diaphragm Pump self-priming pump. … For instance, air operated diaphragm pumps self-prime by creating a pressure differential in the diaphragm chamber. This draws in air flow and pulls the fluid in to the suction port.
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