Goulds Pumps 3408 - IOM - Manual (Page 21)

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3408 IOM 03/99
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Discharge Piping
If the discharge piping is short, the pipe diameter can
be the same as the discharge opening. If the piping is
long, the pipe diameter should be one or two sizes
larger than the discharge opening. On long horizontal
runs, it is desirable to maintain as even a grade as
possible. Avoid high spots, such as loops, which will
collect air and throttle the system or lead to erratic
pumping.
A check valve and an isolating gate valve should be
installed in the discharge line. The check valve,
placed between pump and gate valve, protects the
pump from excessive back pressure, and prevents
liquid from running back through the pump in case of
power failure. The gate valve is used in priming and
starting, and when shutting the pump down.
Pressure Gauges
Properly sized pressure gauges should be installed in
both the suction and discharge nozzles in the gauge
taps provided. The gauges will enable the operator to
easily observe the operation of the pump, and also
determine if the pump is operating in conformance
with the performance curve. If cavitation, vapor
binding, or other unstable operation should occur,
widely fluctuating discharge pressure will be noted.
Fig. 13