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.)
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