Fastening
WARNING:
• Only use fasteners of the proper size and material.
• Replace all corroded fasteners.
• Make sure that all fasteners are properly tightened and that there are no missing fasteners.
Suction-piping checklist
Performance curve reference
Net positive suction head available (NPSH
A
) must always exceed NPSH required (NPSH
R
) as shown on
the published performance curve of the pump.
Suction-piping checks
Check Explanation/comment Checked
Check that the distance between the inlet flange of
the pump and the closest elbow is at least five pipe
diameters.
This minimizes the risk of cavitation in
the suction inlet of the pump due to
turbulence.
See the Example sections for
illustrations.
Check that elbows in general do not have sharp
bends.
See the Example sections for
illustrations.
Check that the suction piping is one or two sizes
larger than the suction inlet of the pump.
Install an eccentric reducer between the pump inlet
and the suction piping.
The suction piping must never have a
smaller diameter than the suction inlet
of the pump.
See the Example sections for
illustrations.
Check that the eccentric reducer at the suction
flange of the pump has the following properties:
• Sloping side down
• Horizontal side at the top
See the example illustrations.
If suction strainers or suction bells are used, check
that they are at least three times the area of the
suction piping.
Suction strainers help to prevent
clogging.
Mesh holes with a minimum diameter
of 1/16 in. (1.6 mm) are recommended.
If more than one pump operates from the same
liquid source, check that separate suction-piping
lines are used for each pump.
This recommendation helps you to
achieve a higher pump performance.
If necessary, make sure that the suction piping
includes a drain valve and that it is correctly
installed.
—
Liquid source below the pump
Check Explanation/comment Checked
Make sure that the suction piping is free from
air pockets.
This helps to prevent the occurrence of air
and cavitation in the pump inlet.
Check that the suction piping slopes upwards
from the liquid source to the pump inlet.
—
If the pump is not self-priming, check that a
device for priming the pump is installed.
Use a foot valve with a diameter that is at
least equivalent to the diameter of the suction
piping.
Installation
36 Model 3196 i-FRAME Installation, Operation, and Maintenance Manual
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