Gorman-Rupp Pumps 81 1/2D3-X1 1P 326949 and up - Manual (Page 11)

OM−00789 80 SERIES
PAGE B − 4 INSTALLATION
by installing a standard pipe increaser fitting at the
end of the suction line. The larger opening size will
reduce the inlet velocity. Calculate the required submergence using the following formula based
on the increased opening size (area or diameter).
Figure 2. Recommended Minimum Suction Line Submergence vs. Velocity
DISCHARGE LINES
Siphoning
Do not terminate the discharge line at a level lower
than that of the liquid being pumped unless a si-
phon breaker is used in the line. Otherwise, a si-
phoning action causing damage to the pump
could result.
Valves
If a throttling valve is desired in the discharge line,
use a valve as large as the largest pipe to minimize
friction losses. Never install a throttling valve in a
suction line.
A check valve in the discharge line is normally rec-
ommended, but it is not necessary in low dis-
charge head applications.
With high discharge heads, it is recommended that
a throttling valve and a system check valve be in-
stalled in the discharge line to protect the pump
from excessive shock pressure and reverse rota-
tion when it is stopped.
If the application involves a high discharge
head, gradually close the discharge
throttling valve before stopping the pump.
Bypass Lines
If it is necessary to permit the escape of air to atmo-
sphere on initial priming or during the repriming
cycle, install an air bypass line - sized so that it will
not affect the pump discharge capacity - between
the pump and the discharge check valve. Since
this pump does not use a suction check valve, the
discharge end of the bypass line must be sub-
merged in the liquid being pumped in order to
maintain suction.