Page 241 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition
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Pumping of Liquids 21 3
required submergence. If the water is at 100°F at sea level, used for metering. For specific performance characteris-
approximately 17 inches must be added to the 70°F sub- tics of any type consult the appropriate manufacturer.
mergence value [14].
These pumps are low in cost, require small space, and
are self priming.
Rotary Pumps
Some can be rotated in either direction, have close
clearances, require over-pressure relief protection on dis-
There are many different types of positive displace- charge due to positive displacement action, and have low
ment rotary pumps [29] as illustrated in Figure 3-64 and volumetric efficiency [ 81.
Figures 3-65A, B, 6.
Performance Characteristics of Rotary Pumps:
The majority of this type are capable of handling only
a clean solution essentially free of solids. The designs
using rubber or plastic parts for the pressure device can 1. Flow proportional to speed and almost independent
handle some suspended particles. In general, these of pressure differential.
pumps handle materials of a wide range of viscosity (up to (a) Internal slip reduces efficiency, and increases
500,000 SSU) and can develop quite high pressures (over with pressure and decreasing viscosity.
~
1000 psi). In addition, the units can handle some vapor or
dissoIved gases mixed with the liquid being pumped. The (b) Entrained gases reduce liquid capacity and cause
capacity is generally low per unit, and at times, they are pulsations.
S
Four-Lobe Pump Sliding Vane Pump
uanp ~~~~~~~1 Gear Pump Three -Lobe Pump Discharge
I IDiaehlorae Driwina Gear
Swinging Vane Pump
Suctiala Flexible
Rubber Tube
Discharae r.l”*
n
Discharge Squeeze Ring
Shuttle Block Pump Squeegee Pump
Figure 3-64. Rotary pumps. (By permission, Dolman, R. E., Chemical Engineering, Mar. 1952, p. 159.)