Page 125 - Fluid mechanics, heat transfer, and mass transfer

PUMPS 103

FIGURE 5.3 Classification of positive displacement pumps. (Source: Hydraulic Institute.)

& Only moving parts are shaft and impeller. the impeller is directly mounted onto the motor shaft
& No close clearances. and supported by the bearings of the motor.
& No valves/reciprocating parts as integral parts of the . What are the features of pumps with impellers mounted
pump. between bearings?
& Ease of maintenance. & In this group of centrifugal pumps, the impeller or
the impellers are mounted onto the shaft with the
& Less noise.
bearings on both ends. The impellers are mounted
& Low first cost.
between the bearings.
& Small floor space requirement.
& These types of pumps are further divided into single-
. What are overhung impeller-type pumps?
stage (one impeller) or multistage pumps (multiple
& The impeller or impellers are mounted on the ex-
impellers).
treme end of the shaft in a cantilevered condition . What are the parameters required in specifying a
hanging from the support bearings.
centrifugal pump?
& This type of pumps is also subdivided into a class
& Required flow rate, which is determined by material
knownasmotorpumpsorclose-coupledpumpswhere
and energy balances.