Goulds Pumps 3393 - IOM - Manual (Page 33)

Installation
Suction-piping checklist
Performance curve reference
CAUTION:
Vary the capacity with the regulating valve in the discharge line. Never throttle the flow from the suction
side. This action can result in decreased performance, unexpected heat generation, and equipment
damage.
Net positive suction head available (NPSH
A
) must always exceed NPSH required (NPSH
R
) as
shown on the published performance curve of the pump.
NOTICE:For optimum life a suction strainer must be permanently installed in the suction piping
to prevent debris from entering the pump and causing it to seize. See below.
Suction-piping checks
Check Explanation/comment Checked
Check that piping is free of dirt Dirt or debris can damage the
and foreign objects. pump on startup.
Check that elbows in general do This minimizes the risk of cavita-
not have sharp bends. tion in the suction inlet of the
pump due to turbulence.
Check that the suction piping is The suction piping must never
one or two sizes larger than the have a smaller diameter than the
suction inlet of the pump. suction inlet of the pump.
Install an eccentric reducer be-
tween the pump inlet and the
suction piping.
Check that the eccentric reducer
—
at the suction flange of the pump
has the following properties:
• Sloping side down
• Horizontal side at the top
When suction strainers or suction Suction strainers help to prevent
bells are used, check that they are clogging.
at least three times the area of the The strainer should be no coarser
suction piping. than 40 mesh – 60 mesh or higher
is preferred. Strainers must have
a minimum free open area of
300% of nominal pipe diameter.
Velocities should be limited to 6-7
ft/s to keep the pressure drop
across the strainer to a minimum.
The pressure drop across the
strainer should be monitored and
the strainer cleaned if the pres-
sure drop exceeds 5 psi (0.34 bar)
or NPSHR is not adequate.
If more than one pump operates This recommendation helps you to
from the same liquid source, achieve a higher pump perfor-
check that separate suction-piping mance.
lines are used for each pump.
If necessary, make sure that the
—
suction piping includes a drain
valve and that it is correctly in-
stalled.
Liquid source below the pump
Check Explanation/comment Checked
Make sure that the suction piping This helps to prevent the occur-
is free from air pockets. rence of air and cavitation in the
pump inlet.
Model 3393 Installation, Operation, and Maintenance Manual 31