3
2
1
1.
No air pockets
2.
Eccentric reducer
3.
Gradual rise
Figure 21: Gradual rise to the pump – correct
1
1.
Distance plus eccentric reducer straightens the flow
Figure 22: Suction pipe above the pump – correct
1
1.
Path of the water
Figure 23: Suction pipe above the pump – incorrect
4.5.3 Suction-piping valve considerations
Suction valves
CAUTION:
Never throttle the flow from the suction side. Only use suction valves to isolate the pump for
maintenance, and install such valves in positions to avoid air pockets.
Before you install suction valves in the suction piping, review these considerations:
•
Make sure that the suction piping valves are placed right before the run of recommended straight
pipe.
•
Never throttle the pump with the use of a valve on the suction side of the pump.
•
Only use suction valves to isolate the pump for maintenance purposes.
•
Always install the valve in a position that avoids the formation of air pockets.
Foot valves
If the pump operates under static suction lift conditions, you can install a foot valve in the suction line in
order to avoid the necessity of priming each time you start the pump.
Before you install foot valves in the suction piping, review these considerations:
•
Make sure this valve is of the flapper type, rather than the multiple spring type, and that it is sized to
avoid excessive friction in the suction line.
•
Size the foot valve and pipe in order to maximize NPSH
A
to the pump by minimizing suction line
losses.
4.5 Piping checklists
30
Model 3409 Installation, Operation, and Maintenance Manual
