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3.3
Operation Safeguards
Quiet Submersible Vertical (QVS) Series pumps are equipped with NEMA standard
flow-cooled motors, which are cooled by the process fluid. In general, flow-cooled
motors have three requirements for long operational life. They are:
1.
A suitable operating environment.
2.
An adequate electrical supply.
3.
An adequate flow of cooling water over the motor.
Quiet Submersible Vertical (QSV) Series pumps have been engineered to provide a
suitable mechanical operating environment and to provide an adequate flow of cool-
ing water over the motor, provided the pump is operated between the maximum and
minimum flow rates specified for each pump series.
WARNING:
Safeguards include low-pressure switches, low-flow shutdown, switches, tempera-
ture limit switches, quick-trip circuit breakers and properly-sized motor starter
heaters. The three-phase electrical power must exhibit amperage readings in each
leg within ± 5% of the average for all three legs (Section 3.6.3, Three-Phase Power
Imbalance). Consult the motor operation manual for additional information.
3.4
Inlet and Discharge - IMPORTANT!
3.4.1
Inlet Piping
•
Positive feed pressure is required at all flow points.
•
Avoid "high points" and other areas where air may accumulate ahead of
the pump.
•
The inlet piping should be at least as large as the inlet port; pipe size
changes should be tapered.
•
Sizing pipe to induce 3 psi (0.21 bar) pressure drop or less per 100 feet
(30.5 m) is recommended.
•
NEVER throttle the pump on the inlet side.
•
The pump inlet line should be filled and tested with 20 - 100 psi
(1.4 - 1.6 bar) pressure to detect any leaks prior to start-up.
CERTAIN SAFEGUARDS MUST BE IN PLACE TO PREVENT THE
FOLLOWING OPERATING CONDITIONS:
•
Flow rate below minimum specified flow rate
•
Close discharge valve (deadheaded condition)
•
Dry running
•
Fluid temperature greater than 90°F (32°C)
•
Low voltage
•
Imbalanced three-phase power
6
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