2.
Gate and check valves may be used on the discharge side, but it is not necessary in low dis-
charge head applications.
3.
It is recommended to use a throttling valve and check valve in the discharge line to protect the
pump from excessive shock or water hammer and reversed rotation when pump is stopped.
4.1.7 Discharge Piping
1.
To minimize piping friction losses:
•
Keep discharge line as straight as possible.
•
Use the minimum number possible of elbows and other pipe fittings.
•
Use long radius elbows and/or eccentric reducers.
2.
Do not terminate the discharge line at a level lower than that of the liquid being pumped, unless a
siphon breaker is used in the discharge line. Siphoning action may cause damage to the pump.
3.
If there is a high discharge head, slow re-priming may be encountered requiring the use of an air
venting device. If a discharge check valve is used an air release line must be incorporated between
the discharge check valve and pump to insure priming.
4.
If the system has a long discharge line it is recommended to install a siphon breaker to avoid si-
phoning out the liquid from pump casing.
4.1.8 Piping checklists
4.1.8.1 Suction-piping checklist
Suction-piping checks
Check
Explanation/comment
Checked
This minimizes the risk of cavitation in the suction in-
let of the pump due to turbulence.
Check that elbows in general do not have
sharp bends.
—
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 diame-
ter than the suction inlet of the pump.
Check that the eccentric reducer at the
suction flange of the pump has the follow-
ing properties:
•
Sloping side down
•
Horizontal side at the top
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 and prevent vapor locking espe-
cially with specific gravity of liquid less than 0.60.
If necessary, make sure that the suction
piping includes a drain valve and that it is
correctly installed.
—
Assure adequate insulation is applied for
liquids with specific gravity less than 0.60.
To assure sufficient NPSHa.
4.1 Pre-installation
28
Model Trash Hog II Installation, Operation, and Maintenance Manual
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