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Model ST1½/ST40 •
4
st15dl4sm-rev0316
Principle of Pump Operation
Air Line
Discharged
Fluid
Discharge
Stroke
Suction
Stroke
Primed
Fluid
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.
This Containment Duty SANDPlPER unit differs from other SANDPIPER units only in that it utilizes four
(4) diaphragms instead of two (2). Two rod-connected diaphragms are the driver diaphragms. The other
two (outermost) diaphragms are the actual pumping diaphragms. Each driver diaphragm (of neoprene
or other elastomer), and the pumping diaphragm (of PTFE), are separated by a chamber filled with liquid
which transmits the reciprocating motion of the driver diaphragm to the pumping diaphragm. The PTFE
pumping diaphragms, in turn, create the alternating suction and discharge action in the outer diaphragm
chambers, and are the only diaphragms in contact with liquid being pumped.
SAFE AIR
EXHAUST
DISPOSAL
AREA
PUMP INSTALLATION AREA
1" DIAMETER AIR
EXHAUST PIPING
1" DIAMETER AIR
EXHAUST PIPING
1" DIAMETER AIR
EXHAUST PIPING
MUFFLER
LIQUID
LEVEL
SUCTION
LINE
LIQUID
LEVEL
SUCTION
LINE
MUFFLER
MUFFLER
SUBMERGED ILLUSTRATION
Pump can be submerged if the pump materials of construction
are compatible with the liquid being pumped. The air exhaust
must be piped above the liquid level. When the pumped product
source is at a higher level than the pump (flooded suction
condition), pipe the exhaust higher than the product source to
prevent siphoning spills.
MODEL SPECIFIC
2: INST
AL
& OP
