A diaphragm pump (also called a Membrane pump) is a positive displacement pump that uses a mixture of the reciprocating actions of a rubber, thermoplastic or teflon 
diaphragm and suitable valves on either aspect 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 draws in and expels liquid through the pump. … Both diaphragms that are linked by a shaft through the centre section where in fact the air valve is Air Diaphragm Pump situated.
Though this will depend upon the pump and application, a positive displacement pump, is generally a self-priming pump. … For example, air managed diaphragm pumps self-primary by creating a pressure differential in the diaphragm chamber. This draws in surroundings and pulls the fluid into the suction port.