MSD
TM
Series
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8
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Theory and Operation Continued
MSD
Pump Internal Components
The internal components of an MSD pump can
vary depending on pump configuration and
number of stages. Each stage uses a cen
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trifugal impeller with a spacer and wear ring to
reduce internal leakage.
The WATER BEARING™ assembly is located
at the discharge end of the pump. A balance
disc rotates in the bearing carrier and serves
as a thrust bearing for the pump. This unique
design uses patented WATER BEARING™
technology which allows feed water to cool and
lubricate the balance disc.
As the motor rotates the pump, pressure differ
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ences acting on the rotating impellers generate
an axial thrust acting toward the motor. The
WATER BEARING™ employs the balance disc
to create a counter-pressure which exactly can-
cels the impeller thrust load. The bearing drain
line is used to produce the counter-pressure on
the balance disc. This thrust and counter-thrust
allows the disc to “self-balance” based on oper
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ating conditions.
INLET
PRESSURE
SINGLE
STAGE
WATER BEARING™
ASSEMBLY
DISCHARGE
PRESSURE
Figure 4 - MSD Pump Internal Flow