Figure 24: Priming with foot valve
In either of these methods (1) and (2), the pump will remain primed, provided foot valve is tight.
Any failure, however, of foot valve when pump is standing idle, will permit the pump to lose its
prime through leakage from stuffing boxes.
3.
Bypassing around discharge check valve
This method can be used only when there is liquid under some pressure in the discharge line.
The original prime must be effected from some outside source. After subsequent idle periods,
open air vent valves and open valves in bypass line around discharge check and gate valves un-
til liquid flows from vent openings. Close air vent valves and bypass valve, start pump and open
discharge gate valve.
Figure 25:
The valve in bypass can be left open, in which event, during idle periods, loss through foot valve is con-
stantly replenished from discharge line. This system is used for automatic operation where idle periods
are of short duration and there is no danger of exhausting all liquid from discharge line, due to leaky foot
valve. The foot valve must be capable of withstanding static head pressure of the system.
Priming by ejection
On suction lift installation, an ejector, operated by steam, compressed air, or under water pressure, and
connected to tapped opening in top of casing can be used to remove air from casing and suction line,
thus priming the pump. See
Close discharge gate valve, open valve "E" in steam, air or water pressure supply line. Open valve "S" in
suction pipe of ejector connected to pump casing. Air will be evacuated and liquid will be drawn up into
4.3 Priming
Model 3415 Installation, Operation, and Maintenance Manual
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