Gorman-Rupp Pumps 16A22-B 1068713 and up - Manual (Page 11)

10 SERIES OM−00711−04
PAGE B − 5 INSTALLATION
tween the pump discharge and the check valve. A
self-priming centrifugal pump will not prime if
there is sufficient static liquid head to hold the dis-
charge check valve closed.
NOTE
The bypass line should be sized so that it does not
affect pump discharge capacity; however, the by-
pass line should be at least 1 inch (25,4 mm) in di-
ameter to minimize the chance of plugging.
In low discharge head applications (less than 30
feet (9,1 m)), it is recommended that the bypass
line be run back to the wet well, and located 6
inches below the water level or cut-off point of the
low level pump. In some installations, this bypass
outline may be terminated with a six-to-eight foot
(1,8 to 2,4 m) length of 1-1/4 inch (31,8 mm) I.D.
smooth-bore hose; air and liquid vented during
the priming process will then agitate the hose and
break up any solids, grease, or other substances
likely to cause clogging.
A bypass line that is returned to a wet well
must be secured against being drawn into
the pump suction inlet.
It is also recommended that pipe unions be in-
stalled at each 90
_ elbow in a bypass line to ease
disassembly and maintenance.
In high discharge head applications (more than
30 feet (9,1 m), an excessive amount of liquid may
be bypassed and forced back to the wet well under
the full working pressure of the pump; this will re-
duce overall pumping efficiency. Therefore, it is
recommended that a Gorman-Rupp Automatic
Air Release Valve be installed in the bypass line.
Gorman-Rupp Automatic Air Release Valves are
reliable, and require minimum maintenance. See
Automatic Air Release Valves in this section for
installation and theory of operation of the Auto-
matic Air Release Valve. Consult your Gorman-
Rupp distributor, or contact the Gorman-Rupp
Company for selection of an Automatic Air Release
Valve to fit your application.
Except in certain specific applications (to
prevent flooding during service of an auto-
matic air release valve in a below-ground
lift station), if a manual shut-off valve is in-
stalled anywhere in a bypass line, it must
be a full-opening, ball-type valve to pre-
vent plugging by solids.
A manual shut-off valve should not be
installed in any bypass line. A manual
shut-off valve may inadvertently be left
closed during operation. A pump which
has lost prime may continue to operate
without reaching prime, causing dan-
gerous overheating and possible explo-
sive rupture of the pump casing. Per-
sonnel could be severely injured.
Allow an over-heated pump to cool be-
fore servicing. Do not remove plates,
covers, gauges, or fittings from an over-
heated pump. Liquid within the pump
can reach boiling temperatures, and va-
por pressure within the pump can cause
parts being disengaged to be ejected
with great force. After the pump cools,
drain the liquid from the pump by re-
moving the casing drain plug. Use cau-
tion when removing the plug to prevent
injury to personnel from hot liquid.
AUTOMATIC AIR RELEASE VALVE
When properly installed and correctly adjusted to
the specific hydraulic operating conditions of the
application, the Gorman-Rupp Automatic Air Re-
lease Valve will permit air to escape through the by-
pass line, and then close automatically when the
pump is fully primed and pumping at full capacity.