Page 100 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

84 Applied Process Design for Chemical and Petrochemical Plants

30 psig
---- N2pad

s psig 70°F 1
J Normal operating level

...._...-l)()---..L---"-6-90° ells
in system,
,� Gate valve
Sharp exit
welded

15 ft
Storage tank Centrifugal pump Reactor
Figure 2-19. Pipe sizing using resistance coefficients, K. Illustration for Example 2-1.

From Figure 2-3 (friction factor), ft = 0.0205 Pump Discharge Line Sizing ( onl)')
The pump discharge can flow at a higher velocity than
I'Lv 2 the suction line, due in part to NPSH conditions on the
(2- 2) suction side of any pump (which are not considered
D (2g)
directly in these pipe sizing calculations).
0.0205 (15) (1.91)2 From Table 2-4, select 6 ft/sec as design velocity for
( 2.067 in J estimating pipe size.
12 2(32.2) For 20 gpm, cross-section area for flow required:

hr== 0.101 ft of kerosene fluid, pipe friction, for 15 ft A = ����-------�--
20
7.48 gal/cu ft (60 sec/min) (6 ft/sec)
Loss through pump suction fittings:
= 0. 00742 sq ft
= (0.007427)(144) = 1.009 sq in.
a. Square edged inlet (tank to pipe), K = 0.5, Figure 2-
12A From Appendix A-16, Standard Schedule 40 pipe
b. Gate valve flanged, open, in suction line, from Table For 1-in. pipe, A = 0.8640 sq in. (too small)
2-2, with � = 1, K = 8 fr IX-in. pipe, A= 1.495 sq in. (too large)
Try IX-in. pipe, ID = 1.38 in.
K = 8 (0.0205) = 0.164
(Note: Usually do not select this size. Could go to IM-
hr= Kv2/2g = (0.5 + 0.164) (l.91)2/2 (32.2) = 0.0853 ft in. Velocity would be even slower.)
fluid
Actual velocity would be: (IX-in. pipe)
Total suction pipe side friction loss:
v = 20 (144)/((60) (7.48) (1.495)] = 4.29 ft/sec
I:hr = 0.101 + 0.0853 = 0.1863 ft kerosene
This is acceptable. Practical usage range is 3 ft/sec to
9 ft/sec, although IX-in. pipe is not the best size for
Note: when used for pump system balance, this Lhr some plants.
must be used as a negative number (-0.1863) because it is
a pressure loss associated with the fluid flowing. For pipe Reynolds number, R = 50.6Qp/ dµ (2-49)
0
line sizing, the pressure head on the tank of 5 psig and any = 50.6 (20)(0.81 X 62.3)/1.38 (1.125)
elevation difference between tank outlet nozzle and pump = 32,894 (turbulent)
suction centerline do not enter into the calculations. For IX" E/D = 0.0014, Figure 2-11. (2-49A)