Dover PSG Wilden PX220 Engineering, Operation & Maintenance Download Page 5

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The Wilden diaphragm pump is an air-operated, positive displacement, self-priming pump. These drawings show flow pattern
through the pump upon its initial stroke. It is assumed the pump has no fluid in it prior to its initial stroke.

FIGURE 1 The air valve directs pressurized
air to the back side of diaphragm A. The
compressed air is applied directly to the
liquid column separated by elastomeric
diaphragms. The diaphragm acts as
a separation membrane between the
compressed air and liquid; a balanced
load removes mechanical stress from the
diaphragm. The compressed air moves
the diaphragm away from the center
of the pump. The opposite diaphragm
is pulled in by the shaft connected to
the pressurized diaphragm. Diaphragm
B is on its suction stroke; air behind
the diaphragm has been forced out to
atmosphere through the exhaust port of
the pump. The movement of diaphragm
B toward the center of the pump creates
a vacuum within chamber B. Atmospheric
pressure forces fluid into the inlet
manifold forcing the inlet valve ball off its
seat. Liquid is free to move past the inlet
valve ball and fill the liquid chamber (see
shaded area).

FIGURE 2 When the pressurized diaphragm,
diaphragm A, reaches the limit of its discharge
stroke, the air valve redirects pressurized
air to the back side of diaphragm B. The
pressurized air forces diaphragm B away
from the center while pulling diaphragm A
to the center. Diaphragm B is now on its
discharge stroke. Diaphragm B forces the
inlet valve ball onto its seat due to the
hydraulic forces developed in the liquid
chamber and manifold of the pump. These
same hydraulic forces lift the discharge
valve ball off its seat, while the opposite
discharge valve ball is forced onto its seat,
forcing fluid to flow through the pump

discharge. The movement of diaphragm A
toward the center of the pump creates a
vacuum within liquid chamber A. Atmos
pheric pressure forces fluid into the inlet
manifold of the pump. The inlet valve ball
is forced off its seat allowing the fluid being
pumped to fill the liquid chamber.

FIGURE 3 At completion of the stroke,
the air valve again redirects air to the
back side of diaphragm A, which starts
diaphragm B on its suction stroke. As
the pump reaches its original starting
point, each diaphragm has gone through
one suction and one discharge stroke.
This constitutes one complete pumping
cycle. The pump may take several cycles
to completely prime depending on the
conditions of the application.

The ProFlo

patented air distribution system incorporates two

moving parts: the air valve spool and the pilot spool. The heart of
the system is the air valve spool and air valve. This valve design
incorporates an unbalanced spool. The smaller end of the spool
is pressurized continuously, while the large end is alternately
pressurized then exhausted to move the spool. The spool directs
pressurized air to one air chamber while exhausting the other.
The air causes the main shaft/diaphragm assembly to shift to
one side — discharging liquid on that side and pulling liquid in
on the other side. When the shaft reaches the end of its stroke,
the inner piston actuates the pilot spool, which pressurizes and
exhausts the large end of the air valve spool. The repositioning
of the air valve spool routes the air to the other air chamber.

MUFFLER

MAIN SHAFT

AIR INLET

AIR VALVE

PILOT SPOOL

AIR VALVE SPOOL

MUFFLER PLATE

END CAP

S e c t i o n 3

H O W I T W O R K S — P U M P

OUTLET

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