EXAMPLE 1
What will be the smallest schedule
40 pipe that can be used if
drop per 100 feet shall not
exceed 3 psi when flow rate is
10,000 pounds per hour, and
steam pressure is 60 psig?
Solution:
1. Find factor for steam pressure
in main, in this case 60
psig. Factor from chart = 1.5.
2. Divide allowable pressure
drop by factor 3 .–
. 1.5 = 2 psi.
3. Enter pressure drop chart at
2 psi and proceed horizontally
to flow rate of 10,000
pounds per hour. Select pipe
size on or to the right of this
point. In this case a 4" main.
EXAMPLE 2
What will be the pressure drop
per 100 feet in an 8" schedule 40
steam main when flow is 20,000
pounds per hour, and steam
pressure is 15 psig?
Solution:
Enter schedule 40 chart at
20,000 pounds per hour, proceed
vertically upward to 8" pipe curve,
then horizontally to pressure drop
scale, read 0.23 psi per 100 feet.
This would be the drop if the
steam pressure were 100 psig.
Since pressure is 15 psig, a correction
factor must be used.
Correction factor for 15 psig = 3.6
0.23 x 3.6 = 0.828 psi drop per
100 feet for 15 psig
SYSTEM DESIGN
Figure 1: Steam Velocity Chart