Page 121 - HVAC Pump Handbook

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Physical Description of HVAC Pumps

118 HVAC Pumps and Their Performance

Axial-flow pumps also can be classified by the method of lubricating
the pump bearings. The pumps can be of open- or enclosed-line shaft-
ing, as shown in Fig. 5.8a and b.
Most HVAC axial-flow pumps are of the open-line shafting, where
the water cools and lubricates the bearings. There should be no corro-
sive or erosive elements in HVAC water that require enclosed-line
shafting. Enclosed-line shafting separates the water from the bear-
ings by an internal tube. This tube is filled with oil, grease, or clear
water that lubricates the bearings. Enclosed-line shafting requires an
oil lubricator, grease cup, or source of clear water for lubrication.
Axial-flow pumps can be furnished in open construction, as shown
in Fig. 5.8a and b, for installation in a tank or sump; they also can be
supplied in a metal pipe with support, which is called a can. This con-
struction is illustrated in Fig. 5.9.
The preceding description of axial-flow pumps is for the larger pumps
used in cooling tower service with capacities in excess of 500 gal/min.
Small multistage turbine pumps are being applied in the HVAC field
on low-flow, high-head applications such as feeding high-pressure
boilers, as shown in Fig. 5.10. The four preceding subassemblies for

Figure 5.9 Axial-flow pump
can type.

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