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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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130 <strong>Centrifugal</strong> <strong>Pumps</strong>: <strong>Design</strong> <strong>and</strong> <strong>Application</strong><br />

Figure 9-13. Bowl assembly with double suction first stage.<br />

Small Boiler Fe<strong>ed</strong> <strong>Pumps</strong><br />

In design, these pumps are quite similar to heater drain pumps, although<br />

the NPSH margin is usually sufficient not to require injection to<br />

the suction case bearing. The mechanical seal should be locat<strong>ed</strong> in a<br />

stuffing box, mount<strong>ed</strong> externally on the discharge head. The minimum<br />

recommend<strong>ed</strong> material selection is cast iron bowls, martensitic steel impellers,<br />

<strong>and</strong> carbon/graphite bearings.<br />

Cryogenic <strong>Pumps</strong><br />

Vertical barrel pumps are particularly well suit<strong>ed</strong> for cryogenic applications.<br />

Being vertically suspend<strong>ed</strong>, thermal contraction <strong>and</strong> expansion will<br />

not cause pump misalignment as long as reasonable precaution is taken in<br />

dealing with nozzle forces at the suction <strong>and</strong> discharge flanges. Because the<br />

motor is support<strong>ed</strong> on top of the discharge head, it is automatically align<strong>ed</strong><br />

to the pump. The external pump configuration is simple <strong>and</strong> easy to ther-

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