3
WILDEN PUMP & ENGINEERING, LLC
WIL-10260-E-02
SECTION 3
THE WILDEN PUMP — HOW IT WORKS
The Wilden diaphragm pump is an air-operated, positive displacement, self-priming pump. These drawings show the 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 pres-
surized air to the back side of diaphragm
A. The compressed air is applied directly
to the liquid column separated by elas-
tomeric diaphragms. The diaphragm
acts as a separation membrane between
the compressed air and liquid, balanc-
ing the load and removing mechani-
cal stress from the diaphragm. The
compressed air moves the diaphragm
away from the center block of the pump.
The opposite diaphragm is pulled in by
the shaft connected to the pressur-
ized diaphragm. Diaphragm B is on its
suction stroke; air behind the diaphragm
has been forced out to the atmosphere
through the exhaust port of the pump.
The movement of diaphragm B toward
the center block of the pump creates a
vacuum within chamber B. Atmospheric
pressure forces fluid into the inlet mani-
fold 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 block while pulling diaphragm A
to the center block. 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 move-
ment of diaphragm A toward the center
block of the pump creates a vacuum
within liquid chamber A. Atmospheric
pressure forces fluid into the inlet mani-
fold 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 exhaust stroke. As
the pump reaches its original starting
point, each diaphragm has gone through
one exhaust and one discharge stroke.
This constitutes one complete pump-
ing cycle. The pump may take several
cycles to completely prime depending
on the conditions of the application.
RIGHT STROKE
MID STROKE
LEFT STROKE
