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How does an Air-operated Double Diaphragm Pump work?

Air-operated double diaphragm (AODD) pumps are powered by compressed air, nitrogen or natural gas.

  • The main directional (air) control valve (1) distributes compressed air to an air chamber, exerting uniform pressure over the inner surface of the diaphragm (2). At the same time, the exhausting air (3) from behind the opposite diaphragm is directed through the air valve assembly(s) to an exhaust port (4).
  • As inner chamber pressure (P1) exceeds liquid chamber pressure (P2), the rod (5) connected diaphragms shift together creating discharge on one side and suction on the opposite side. The discharged and primed liquid's directions are controlled by the check valves (ball or flap) (6) orientation.
  • The pump primes as a result of the suction stroke. The suction stroke lowers the chamber pressure (P3) increasing the chamber volume. This results in a pressure differential necessary for atmospheric pressure (P4) to push the fluid through the suction piping and across the suction side check valve and into the outer fluid chamber (7).
  • Suction (side) stroking also initiates the reciprocating (shifting, stroking or cycling) action of the pump. The suction diaphragm's movement is mechanically pulled through its stroke. The diaphragm's inner plate makes contact with an actuator plunger aligned to shift the pilot signaling valve. Once actuated, the pilot valve sends a pressure signal to the opposite end of the main directional air valve, redirecting the compressed air to the opposite inner chamber.
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    Title: How does an Air-operated Double Diaphragm Pump work?
    Description: Principles of operation for the Air-operated Double Diaphragm Pumps.
    Published: 6/5/2008
    Last Edited: 1/3/2023
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