G-R
OM−05850
OPERATION
PAGE C − 1
OPERATION − SECTION C
THEORY OF OPERATION
Review all SAFETY information in Section A.
A self-priming centrifugal pump
will not prime
if
there is sufficient static liquid head to hold the dis-
charge check valve closed. Self-priming pumps
are not air compressors. During the priming cycle,
air from the suction line must be vented to atmos-
phere on the discharge side. It is therefore neces-
sary to open the discharge side of the pump to at-
mospheric pressure and allow the air to bleed off
during ther priming cycle. If the bleed line is not
closed after the pump is primed, liquid would be
forced back to the wet well under the full working
pressure of the pump. This wasteful recirculation of
liquid is controlled by the Automatic Air Release
Valve.
When properly installed, the Automatic Air Release
Valve will permit air to escape and will close auto-
matically when the pump is fully primed and pump-
ing at full capacity.
Figures C−1 and C−2 show a cross-sectional view
of the valve, and a corresponding description of
operation.
Air from the pump casing passes through the valve
to the wet well during the priming cycle (Figure
C−1).
Figure C−1. Valve in Open Position
When the pump is fully primed, pressure resulting
from flow through the valve compresses the inlet
chamber diaphragm. The barrier liquid on top of
the inlet diaphragm is forced through the orifice in
the upper valve body (at a controlled rate to pre-
vent slamming of the plunger and/or valve chatter)
and onto the top of the plunger chamber dia-
phragm, compressing the plunger rod spring,
closing the valve (Figure C−2). The valve will re-
main closed, reducing the bypass of liquid to 1 to 5
gallons (3,8 to 19 liters) per minute, until the pump
loses its prime or stops.
Some leakage (1 to 5 gallons [3,8 to 19
liters] per minute) will occur when the
valve is fully closed. Be sure the bypass
line is directed back to the wet well or
tank to prevent hazardous spills.
Figure C−2. Valve in Closed Position
Once the pump stops, the spring under the plung-
er forces the barrier liquid on top of the plunger
chamber diaphragm back through the orifice to the
inlet chamber. Any solids that may have accumu-
lated in the inlet chamber settle to the bottom and
are flushed out during the next priming cycle.
ADJUSTMENT
When adjusting the Air Release Valve,
do not remove the adjusting restrictor in
the lower valve body while the pump is
running. Removing the restrictor will
cause spillage of the liquid being
