Handbook of Civil Engineering Calculations

SPECIFIC SPEED CONSIDERATIONS

IN CENTRIFUGAL PUMP SELECTION

What is the upper limit of specific speed and capacity of a 1750-r/min single-stage dou-

ble-suction centrifugal pump having a shaft that passes through the impeller eye if it

handles clear water at 850 F (29.4^0 C) at sea level at a total head of 280 ft (85.3 m) with

a iO-ft (3-m) suction lift? What is the efficiency of the pump and its approximate im-

peller shape?

H:totol heod,m

FIGURE 1. Upper limits of specific speeds of single-stage, single- and double-suction cen-

trifugal pumps handling clear water at 850 F (29.4^0 C) at sea level. (Hydraulic Institute.)

H: total head, ft

_ ..

.^

r/minv/gaTTrnirT

Specific

speed,

/%=

-^j^

for

single-suetion

pumps with

shaft

through

eye of

impeller

_,.

r/min\/ga77m7n

Specific

speed,

^

= 5

-^

for

double-suet

ion

pumps