Page 172 - Chemical Process Equipment - Selection and Design

144 FLUID TRANSPORT EQUIPMENT

TABLE 7.1. Characteristics of Various Kinds of Pumps
Pump Type Construction Style Construction Characteristics Notes
Centrifugal single-stage overhung, process type impeller cantilevered beyond bearings capacity varies with head
(horizontal) two-stage overhung two impellers cantilevered beyond used for heads above single-stage
bearings capability
single-stage impeller between impeller between bearings; casing used for high flows to 1083ft (330 m) head
bearings radially or axially split
chemical casting patterns designed with thin have low pressure and temperature
sections for high-cost alloys ratings
slurry designed with large flow passages low speed and adjustable axial clearance;
has erosion control features
canned no stuffing box; pump and motor low head capacity limits when used in
enclosed in a pressure shell chemical services
multistage, horizontally split casing nozzles located in bottom half of casing have moderate temperature-pressure
ranges
multistage, barrel type outer casing contains inner stack of used for high temperature-pressure
diaphragms ratings
Centrifugal single-stage, process type vertical orientation used to exploit low net positive section
(vertical) head (NPSH) requirements
multistage many stages with low head per stage low-cost installation
inline inline installation, similar to a valve low-cost installation
high speed speeds to 380 rps, heads to 5800 ft high head/low flow; moderate costs
(1770 m)
slump casing immersed in sump for easy low cost
priming and installation
multistage, deep well long shafts used for water well service
Axial propeller propeller-shaped impeller vertical orientation
Turbine regenerative fluted impeller. Flow path resembles capacity independent of head; low
screw around periphery flow/high head performance
Reciprocating piston, plunger slow speeds driven by steam engine cylinders or
motors through crankcases
metering consists of small units with precision diaphragm and packed plunger types
flow control system
diaphragm no stuffing box used for chemical slurries; can be
pneumatically or hydraulically actuated
Rotary screw 1, 2, or 3 screw rotors for high-viscosity, high-flow high-pressure
services
gear intermeshing gear wheels for high-viscosity, moderate-
Dressurehnoderate-flow services
(Cheremisinoff, 1981).
TABLE 7.2. Typical Performances of Various Kinds of Pumpsa

Max Max
Capacity Head P NPSH Max T Efficiency
Type Style (gpm) (ft) (psi) (ft) ("F) (%I
Centrifugal single-stage overhung 15-5,000 492 600 6.56-19.7 851 20-80
(horizontal) two-stage overhung 15-1,200 1394 600 6.56-22.0 851 20-75
single-stage impeller between
bearings 15-40,000 1099 980 6.56-24.9 401-851 30-90
chemical 1000 239 200 3.94-19.7 401 20-75
slurry 1000 394 600 4.92-24.9 851 20-80
canned I-20,000 492 1 10,000 6.56-19.7 1004 20-70
multistage horizontal split 20-1 1,000 5495 3000 6.56-19.7 40 1-500 65-90
multistage, barrel type 20-9,000 5495 6000 6.56-19.7 851 40-75
Centrifugal single stage 20-10,000 804 600 0.98-19.7 653 20-85
(vertical) multistage 20-80,000 6004 700 0.98-19.7 500 25-90
inline 20-12,000 705 500 6.56-19.7 500 20-80
high speed 5-400 5807 2000 7.87-39.4 500 10-50
sump 10-700 197 200 0.98-22.0 45-75
multistage deep well 5-400 6004 2000 0.98-19.7 40 1 30-75
Axial propeller 20-100,000 39 150 6.56 149 65-85
Turbine regenerative 1-2000 2493 1500 6.56-8.20 248 55-85
Reciprocating piston, plunger 10-1 0,000 1.13 X IO6 >50,000 12.1 554 65-85
metering 0-10 1.70~ io5 50,000 15.1 572 20
diaphragm 4-100 1.13~ lo5 3500 12.1 500 20
Rotary screw 1-2000 6.79 x lo4 3000 9.84 500 50-80
mar 1-5000 11,155 500 9.84 653 50-80
~
a 1 m3/min = 264 gpm, 1 m = 3.28 ft, 1 bar = 14.5 psi, "C = ("F - 32)/1.8.