Page 229 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Pumping of Liquids 199

Example 3-13: System Head Using Two Different Pipe
Sizes in Same Line 50 I I I
45 Condition
The system of Figure 3-53 consists of the pump taking 40 , Impeller Operating Head Curve ,,,, .. Friction + 22' Static Head _
suction from an atmospheric tank and 15 feet of 6-inch 35 lL .._ - / t .r 1__, __ 1 .1_
Friction + 15' Static Head
pipe plus valves and fittings; on the discharge there is 20 J 30 - � ,::;.- _..-.::::: Operating Points for System
20 -
feel of 4-inch pipe in series with 75 feet of 3-inch pipe plus .5 �..,..,... t- ... t <, . I
a control valve, block valves, fittings, etc. The pressure of i 25 :...- -- .,....,.. ...
:r
the discharge vessel (bubble cap distillation tower) is 15 15 - � vi"
i.--
psig. Using water as the liquid at 40°F
Suction: 6-inch pipe (using Cameron Tables-Table 2- 110 ......- t> I'" System Friction (See Figure 3-51)
22). To simplify calculations for greater accuracy, use 5 � .,....,.. I I I I I I I i
�
detailed procedure of Chapter 2. 0 - !
0 10 20 30 40 50 60 70 80 90 100 110 120 130 uo 150 160
System Flow, Gpm.
Pipe or Figure 3-52. System head curves for variable static head.
Fitting Loss 200 GPM 300 GPM
Loss, ft/100 ft 0.584 1.24 15 psi;
For 15 ft 15.0 fl
Two, 900 ell, eq. 22.8 A tmos!)heric Bubble Cop
Gate valve, open __1,L Vent Distillation
Total 41.0 ft 0.24 ft. 0.51 ft Tower

The total suction head = h, = +7 - 0.24 = +6.76 at
200 gpm

h, = +7 ·- 0.51 = +6.49 at 300 GPM 150 Discrepancy due lo ....,
Variation in Friction, .,.,-'
Discharge: Lou Doto.,�
/
.... " ,it'
1:,
�<t°',"' ,_,...,\
�.... 'ti:,
100 x C:,'\ � ':-_ .,._\ � °''t\CIC)j
4 inch pipe 3 inch pipe :: -<,o.'°'
200 GPM 300 GPM 200 GPM 300 GPM ....
c:
..
Loss, ft/ l OC ft 4.29 9.09 16.1 34.1 "O 3"
0
For 20 ft 20.0 20.0 :I: 50
For 75 fl 75.0 75.0
Two, 3", 90° ells, eq. 8 8
One, 4", 90° ell, eq. 4.6 4.6
\Oischorgel .;"
friclion
One Gate Valve open L. 7 fl 1.7 ft o���==::::::::::::===�
Total, equivalent ft 24.6 24.6 84.7 84.7
Friction loss, ft fluid 1.06 2.23 i3.6 28.8 0 100 200 300
Control valve al 60% Gallons per Minute
of total, ft fl 1.59 3.34 20.4 43.2 Figure 3-53. System head using two different pipe sizes in same line.
Total discharge friction
loss, ft 2.65 5.57 34.0 72.0
Total head on pump at 300 GPM =
Total static head= 45 - 7 + 15(2.31) = 72.6 ft, SpGr = 1.0 H = 45 + 15(2.31) + 5.57 + 72.0 - 7 + 0.51 = 150.68 ft

Composite head curve
at 200 GPM: head = 72.6 + 0.24 + 2.65 + 34.0 = 109.49 ft The head at 200 GPM (or any other) is developed in the
at 300 GPM: head = 72.6 + 0.51 + 5.57 + 72.0 = 150.68 ft same manner.