Page 102 - Applied Process Design for Chemical and Petrochemical Plants Volume I

Fluid Flow 89

summation, these equivalent lengths for all the compo- TabIe 2-5
nents determine the total pipe length to use in the pres- Typical Design Vapor Velocities* (ft/sec)
sure loss (pressure drop) equations to be described later.
Line Sizes
Fluid - <6" g'- 12" 2 14"
rop for Non-Viscous Liquids
Saturated Vapor
The only significaiice in differentiating between water 0 to 50 psig 30-115 50-125 60-145
and liquids of different densities and viscosities is the con- Cas or Superheated Vapor 110-250
Oto 1Opsig
venience in having a separate simplified table for water. 1 1 to 100 psig 50-140 90-190 95-225
40-115
75-165
101 to 900 psig 30- 85 50-150 85-165
1. Using known flow rate in gallons per minute and a
suggested velocity from Tables 2-4 to 2-8 or Figure 2- *Values listed are guides, and final line sizes and flow velocities
must be determined by appropriate calculations to suit circum-
22, estimate first pipe size. Mean velocity of any liq- stances. Vacuum lines are not included in the table, but usually
tolerate higher velocities. High vacuum conditions require careful
uid flowing in a pipe [3] is given by Figure 2-22 and pressure drop evaluation.
Equation 2-51.
v = 0.408 Q/d2 =: 0.0509 W/(d*) (p), ft/sec (2-31)
Table 2-6
Usual Allowable Velocities for Dud and Piping Systems"

v = q/A = ws/Ap = 183.3 (q/d*), ft/sec (2-54) Service/Application elocity, ft./min.

Forced draft ducts 2,500 - 3,500
2. Estimate or otherwise determine the linear feet of Induced-draft flues and breeching 2,000 - 3,000
straight pipe in the system, L. Chimneys and stacks 2,000
Water lines (max.) 600
3. Estimate (or use actual tabulation) number of fit- 10,mo
tings, valves, etc. in system. Comvert these to equiva- High pressure steam lines 12,000 - 15,000
lent straight pipe using Figures 2-20 or 2-21, Leg, or Low pressure steam lines 25,000
Vacuum steam lines
head by Figures 2-12 through 2-16 and Table 2-2. Compressed air lines 2,000
Refrigerant vapor lines
Note preferred pipe size type For charts. High pressure 1,000 - 3,Om
Low pressure 2,000 - 5,000
4. Determine expansion or contraction losses, if any, Refrigerant liquid 200
including tank or vessel entrance or exit losses from Brine lines 400
Figures 2-12A, 2-15, or 2-16. Convert units to psi, Ventilating ducts 1,200 - 3,GoO
head loss in feet times 0.4331 = psi (for water), or Register grilles 500
adjust for Sp Gr of other liquids. *By permission, Chemical Engineer's Handbook, 3rd Ed., McGraw-Hill Book
Co., New York, N.Y., p. 1642.
5. Estimate pressure drop through orifices, control
valves, and other items in the system, but not equip-
ment. For conlrol valves, estimate AP from para-
graph to follow.
lish piping system friction pressure drop (loss),
6. 13etermine pressure drop per unit of length. liquids (Figure 2-23):
a. Calculate Reynolds number [3]

For turbulent flow: AP/100 ft = 0.0216 f pQ2/d5 (2-35)

b. From Reynolds Number-Friction Factor Chart, = 0.000335 W/(d5) (p) (2-55A)
Figure 2-3, read friction factor, f, at E/d value

taken from Figure 2-1 1 ~
For laminar flow: AP/100 ft = 0.0668 (p) v/d2 (2-56)
c. Calculate pressure drop per 100 feet of (straight
and/or equivalent) pipe [3] as psi/lOO ft. Estab- = 0.0273 (p) 9Jd4 (2-%A)