Page 202 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Pumping of Liquids 173

P = Pressure of Liquid in 801 all mechanical seals) and must not attack the material of
p': Averogt Prtnure Across
Stol Focn the 0-ring shaft packing. Many other designs are avail-
able, and the manufacturers should be consulted for
advice on specific sealing problems.

Centrifugal Pump Selection

The centrifugal pump is a versatile unit in the process
Closing Force = P � (Areo " � :- � rea"c") + Spring Loading
Oeening Force : P I Area B plant, since its ease of control, non-pulsing flow, pressure
'l\ ,"e" and "c" ore Vorloblt
limiting operation fits many small and large flow systems.
Figure 3-21. Area relationship for balanced seal construction. (By
permission, T. J. Sniffen, Power and Fluids, Winter 1958, Worthing-
ton Corp.)

pressures. Actually the maximum operating process pres-
sures are a function of the shaft speed and diameter for a
given seal design fluid and fluid temperature.
Figure 3-22 is an outside balanced seal designed for
vacuum to 150 psig and -40°F to +400°F. (See Table 3-4)
The process fluid must be free of solids (as for practically

Table 3-4
Requirements for Mechanical Seal Installations

Fig.
Feature Description Remarks No.
Cooling Water Jacketed Liquid must dead end 3-23 Figure 3-22. Outside balanced seal (single). (Courtesy Durametallic
Stuffing Box in stuffing box Corp.)
Cooling Gland Plate Efficient to cool 3-24
contact faces
Lubrication Dead-End Good under vacuum, 3-25 0
....
11>
mild abrasives metal- -
:::,
metal, dry seals >000
...
....
Lubrication Circulating Good cooling of 3-26 400 e
contact faces 3 GPM Cooling Wafer_ Cb
Flushing Inside Seal Good for volatile 3-27 3001-
liquids, sol'ns tending 5 GPM Cooling Wafer >C
0
to crystallize, steam 200CD
DI
c:
-
,
Flushing Outside Seal Heating to prevent 3-28 I II II , 100=
solidification �
Quenching Outside Seals For oxidizing and 3-29 0 100 • 2 300 400 soo 600 700 • oo en
(only) corrosive liquids, seal
liquid washes process
fluid, for high temp.
Vent and Inside Seal Safety feature, for 3-30
Drain venting to flare,
draining
Flushing Double Requires circulation 3-31A
system
Flushing Tandem Requires circulation 3-31B
system
Two Rotary Double For improved sealing 3-31C
Four Rotary Double For special sealing 3-310
Tandem problem Figure 3-23. Water jacketed stuffing box. (By permission, H. P. Hum-
mer and W. J. Ramsey, Bulletin SD, 752, O&T, Durametallic Corp.)