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Check
Explanation/comment
Checked
Check that a check valve is installed in the
discharge line, between the isolation valve
and the pump discharge outlet.
The location between the isolation valve and the pump
allows inspection of the check valve.
The check valve prevents damage to the pump and seal
due to the back flow through the pump, when the drive
unit is shut off. It is also used to restrain the liquid flow.
See Example: Discharge piping equipment for illustra-
tions.
If increasers are used, check that they are
installed between the pump and the check
valve.
See Example: Discharge piping equipment for illustra-
tions.
If quick-closing valves are installed in the
system, check that cushioning devices are
used.
This protects the pump from surges and water hammer.
Example: Discharge piping equipment
Correct
Incorrect
1
2
3
4
1.
Bypass line
2.
Shut-off valve
3.
Check valve
4.
Discharge isolation valve
2
1
1.
Check valve (incorrect position)
2.
The isolation valve should not be positioned be-
tween the check valve and the pump.
4.7.4 Bypass-piping considerations
When to use a bypass line
Provide a bypass line for systems that require operation at reduced flows for prolonged periods. Connect
a bypass line from the discharge side (before any valves) to the source of suction.
When to install a minimum-flow orifice
You can size and install a minimum-flow orifice in a bypass line in order to prevent bypassing excessive
flows. Consult your ITT representative for assistance in sizing a minimum-flow orifice.
4.7 Piping checklists
44
XHD Installation, Operation, and Maintenance Manual
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