Gorman-Rupp Pumps 13C3-E5 3P All serial numbers - Manual (Page 10)

OM--04760 SELF-PRIMING CENTRIFUGAL PUMPS
PAGE B -- 4 INSTALLATION
Figure 1. 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
Self-priming pumps are not air compressors. Dur-
ing the priming cycle, air from the suction line must
be vented to atmosphere on the discharge side. If
the discharge line is open, this air will be vented
through the discharge. However, if a check valve
has been installed in the discharge line, the dis-
charge side of the pump must be opened to atmos-
pheric pressure through a bypass line installed be-
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 in diameter to