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.
W
ARNING: 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
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 -
IMP
ORTANT!
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.
• NE
VER 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.
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