Percent of BEP pump capacity
FIGURE 10. Performance of a pump at constant speed in pump duty and
turbine duty. (Chemical Engineering.)
48.6 gal/min (177.1 L/min). Find the contmuous-recirculation flow at shutoff head H ft
(m) of 540 ft (164.6 m) from Q 5 = QB(HsIHopf\ where Hop = operating head, ft (m). Or
Q 3 = 48.6(540/450) = 53.2 gal/min (201.4 L/min).
- Find the minimum safe flow for this pump
The minimum safe flow, Ib/h, is given by wmin = 2545bhp/[CpTp + (1.285 x 10~^3 )//J,
where Cp = specific head of the water; other symbols as before. Substituting we find
H>min = 2545(60)/[1.0(6.1) + (1.285 x 10-^3 )(540)] = 22,476 Ib/h (2.83 kg/s). Converting to
gal/min yields Q^n = wmin/[(ft^3 /h)(gal/min)(lb/ft^3 )] for the water flowing through the
pump. Or, gmin = 22,476/[(8.021)(59.6)] = 47.1 gal/min (178.3 L/min).
- Compare the shutoff recirculation flow with the safe
recirculation flow
Since the shutoff recirculation flow Qs = 53.2 gal/min (201.4 L/min) is greater than
2min = 47.1 gal/min (178.3 L/min), the 11.5-in (29.2-cm) impeller is adequate to provide
safe continuous recirculation. An 11.25-in (28.6-cm) impeller would not be adequate be-
cause Qmin = 45 gal/min (170.3 L/min) and Q 5 = 25.6 gal/min (96.9 L/min).
Pump BHP
Turbine E
Turbine BHP
Pump H Pump BEP
Turbine H
Pump E
Turbine BEP
Percent
of BEP
pump head,
efficiency
and BHP
