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8
• Model HD20F Non-Metallic
Air-Operated Double Diaphragm (AODD) pumps are powered by compressed
air or nitrogen.
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.
Principle of Pump Operation
UNIVERSAL ALL AODD
2: INST
ALL
& OP
