Page 119 - HVAC Pump Handbook

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Physical Description of HVAC Pumps

116 HVAC Pumps and Their Performance

Figure 5.7 Double-suction axially split, volute pump. (Courtesy Patterson
Pump Company, A subsidiary of The Gorman-Rupp Company.)

provide semiopen impellers. These impeller configurations are shown
in Fig. 5.8a and b.
Turbine-type pumps with enclosed impellers and bowl rings usually
offer the highest sustained pump efficiency due to the ability to con-
trol more closely the amount of bypassing that occurs between the
impeller and the bowl. Semiopen impellers must be checked periodi-
cally for the right clearance between the impeller and the bowl. The
correct clearance between the impeller and the bowl is called the lat-
eral setting. This setting can be accomplished by adjusting the top
drive coupling of a vertical, hollow-shaft motor or by a special spacer
coupling below a vertical, solid-shaft motor.
2. Mixed flow. Mixed-flow pumps are used on high-capacity,
moderate-head applications; they are found in the HVAC industry on

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