SAMCO CP7, Instructions Manual

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3. Where two or more pumps are connected to the same suction line, install gate valves so that any
pump can be isolated from the line. Gate valves should be installed on the suction side of all pumps
with a positive pressure for maintenance purposes. Install gate valves with stems horizontal to
avoid air pockets. Globe valves should not be used, particularly where NPSH is critical.
4. The pump must never be throttled by the use of a valve on the suction side of the pump. Suction
valves should be used only to isolate the pump for maintenance purposes, and should always be
installed in positions to avoid air pockets.
Inlet bells, pipe size, and wet well (sump) dimensions should conform to the recommendations of the
Hy-
draulic Institute Standards latest edition.
Discharge piping:
If the discharge piping is short, the pipe diameter can be the same as the discharge opening. If the piping
is long, 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 gate valve should be installed in the discharge. The check valve, placed between pump
and gate valve, protects the pump from excessive backpressure, and prevents liquid from running back
through the pump in case of power failure. The gate valve is used in priming and when shutting the pump
down.