Page 205 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

178 Applied Process Design for Chemical and Petrochemical Plants

Table 3-5
Pump Selection Guide

Vertical
Feature
Horizontal
t Space Requirements Less head rmm Less floor area, more
0 head room.
a.
0) NPSH Requires more Requires less
fn
L
0 Priming Required* Usually not required
I Flexibility (Relative to
al
r future changes) Less More
e Maintenance More accessible Major work project
15.0 m Corrosion and Abrasion No great Can be considerable
problem
problem
10.0 Less More (requires more
5.0 cost alloy to handle
corrosive Fluid)
5
Capacity -G.P.M. *For some conditions
Figure 3-33. Performance of turbine type centrifugal pump. (Cour-
tesy Roy E. Roth Co.) 300
Enclosed Impeller Characteristics 240

z 180
LI
0,
.E 150
U
Capacity , GPM - I“ 120
0

Enclosed or Open Impeller Chorocteristics 60

0 50 100 150 200
Capacity , Gpm.
I Pump in Series: Q = Constant
H (Total) = HI + H2 + ”‘
More Wrap of Vanes
20 = S-R denotes Series-Rating
Less Vanes (Some Point, Total
Wrop as B above) Pumps in Parallel: H = Constant
Copocity , GPM - Q (Total) = Q, + Q2 + ”‘ (at H for each
Single Pump Curve)
0 = P-R denotes Parallel-Rating
Figure 3-34. Impeller performance guide. Wrap refers to curvature of Point
vanes on impeller. (Adapted by permission, Pic-a-Pump, Allis- 10 = Single pump rating
Chalmers Mfg. Co.)
Figure 3-35. Operation curves of two duplicate centrifugal pumps in
series and parallel.
and the pumps would “hunt” back and forth with no
means to become stabilized. teristics of the pump’s design, impeller entrance opening
and diameter, and the hydraulic operating efficiency of
Figures 3-36A, 3-36B, and 3-36C represent typical and the pump at the fixed designated speed of the perfor-
actual performance curves showing discharge total head mance curves are shown on the chart. All of this perfor-
(head pressure at pump outlet connection for any fluid), mance is for one specific impeller diameter of the fixed
required minimum water horsepower (for pumping rotating speed (rpm), and the fixed impeller design pat-
water), and capacity or pumping volume of the pump (for tern proprietary to the manufacturer (number, shape and
any fluid) for several impeller diameters that would fit the spacing of vanes, and wrap or curvature of vanes).
same case (housing). In addition the important NPSH, Note that Figure 3-36B plots the NPSHR curve for this
(net positive suction head required by the pump) charac- “family” of impellers (different diameters, but exact same