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Application – Three-Phase Motors
17. Open Atmosphere Booster Pump Systems: When
an open booster is placed in a lake, tank, etc. that is
open to atmospheric pressure, the water level must
provide suffi cient head pressure to allow the pump
to operate above its NPSHR requirement at all times
and all seasons. Adequate inlet pressure must be
provided prior to booster start-up.
Four Continuous Monitoring System Requirements
for Sealed Booster Systems.
1. Water Temperature: Feed water on each
booster must be continuously monitored and
not allowed to exceed the motor nameplate
maximum ambient temperature at any time. IF
THE INLET TEMPERATURE EXCEEDS THE
MOTOR NAMEPLATE MAXIMUM AMBIENT
TEMPERATURE, THE SYSTEM MUST
SHUTDOWN IMMEDIATELY TO PREVENT
PERMANENT MOTOR DAMAGE. If feed water
temperatures are expected to be above the
allowable temperature, the motor must be derated.
See Franklin’s AIM Manual Hot Water Applications
section for derating guidelines. (The high
temperature feed water derating is in addition to the
exchange to DI water derating if the motor factory fi ll
solution was exchanged to DI water.)
2. Inlet Pressure: The inlet pressure on each booster
module must be continuously monitored. It must
always be positive and higher than the NPSHR (Net
Positive Suction Head Requirement) of the pump.
A minimum of 20 PSIG (1.38 Bar) is required at all
times, except for 10 seconds or less when the motor
is starting and the system is coming up to pressure.
Inline Booster Pump Systems (continued)
Even during these 10 seconds the pressure must
remain positive and be higher than the NPSHR (Net
Positive Suction Head Requirement) of the pump.
PSIG is the actual value displayed on a pressure
gauge in the system piping. PSIG is the pressure
above the atmospheric conditions. If at any time
these pressure requirements are not being met, the
motor must be de-energized immediately to prevent
permanent damage to the motor. Once the motor is
damaged, it is usually not immediately noticeable,
but progresses and results in a premature motor
failure weeks or months after the damage occurred.
Motors that will be exposed to pressure in excess
of 500 psi (34.47 Bar) must undergo special high
pressure testing. Consult factory for details
and availability.
3. Discharge Flow: The fl ow rate for each pump must
not be allowed to drop below the motor minimum
cooling fl ow requirement. IF THE MOTOR MINIMUM
COOLING FLOW REQUIREMENT IS NOT BEING
MET FOR MORE THAN 10 SECONDS, THE
SYSTEM MUST BE SHUT DOWN IMMEDIATELY
TO PREVENT PERMANENT MOTOR DAMAGE.
4. Discharge Pressure: The discharge pressure
must be monitored to ensure that a downthrust load
toward the motor is present within 3 seconds after
start-up and continuously during operation.
IF THE MOTOR DISCHARGE PRESSURE IS NOT
ADEQUATE TO MEET THIS REQUIREMENT, THE
SYSTEM MUST BE SHUT DOWN IMMEDIATELY
TO PREVENT PERMANENT MOTOR DAMAGE.
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