This document provides an example of calculating flow velocity and pressure drops in a natural gas pipeline with multiple segments. It includes the dimensions, temperatures, pressures, elevations and flow rates for each segment. It also poses three questions: 1) calculating flow velocity given pipe dimensions and inlet/outlet pressures, 2) determining suitable pipe diameters for branching based on desired pressure drops, and 3) calculating pressure drops in each segment given dimensions, flow rates and inlet pressures. The document demonstrates using an hydraulic module called RPA to calculate thermo-physical properties and solve these pipeline hydraulic problems.

1. Pipe Line Hydraulic Calculation
By:
M. Khosravy

2. An Example !
• A pipeline has 4 segments as follow:
Segment
No. Length (Km) Elevation (+m) Temp (ºC)
1 15 20 50
2 20 40 30
3 50 10 40
4 15 0 20

3. Question #1
• If the pipe diameter and inlet/outlet pressure are
known, what is the flow velocity of natural gas in
it?
Outside diameter Do 52 Inches
Wall thickness t 0.25 Inches
Inside diameter Di 51.5 inches
Inlet pressure P1 1152 Psi
Inlet temperature T1 50 ºC
Outlet pressure P2 883 Psi
Outlet temperature T2 20 ºC

4. The Solution is :
Q(SCF/D) 2,415,957,168 = 68.41 MMSCM/Day
velocity 27.34 ft/s
• If the pipe efficiency consider 92% and effective
roughness of 0.0018”.
• The average erosion velocity is 59.2 ft/s so
calculated velocity is OK.

5. Question #2
• If we want to branch and use gas along pipeline
as follow, what is the suit pipe diameter
according to desire pressure drop?
Seg. Distance Flow Rate Inside Diameter Elevation Inlet Press. Outlet Press. Pav
No. (Km) (MMSCM/D) (inches) ΔH (+m) (Psi) (Psi) Psi
1 15 68.41 47.9556502 20 1152 1100 1126.2
2 20 68.41 44.3131359 40 1100 1000 1050.8
3 50 40 44.5039698 10 1000 900 950.88
4 15 30 44.1098344 0 900 883 891.53

6. Question #3
• If the flow rate and inlet pressure with pipe
diameter are known for each segments, how we
can calculate pressure drop in each segments?
Inside Inlet Outlet Ave.
Seg. Distance Flow Rate Elevation Pav
Diameter Press Press. Temp.
No. (Km) (MMSCM/D) ΔH (+m) Psi
(inches) . (Psi) (Psi) (ºC)
1123.34
1 15 68.41 47 20 1152 1094.201 8 50
1063.40
2 20 68.41 47 40 1100 1025.954 7 30
963.284
3 50 40 47 10 1000 925.6103 1 40
893.891
4 15 30 47 0 900 887.7554 7 20

7. RPA Hydraulic Module Calculate All
Of Them !!!
It can be also help you to find thermo
physical properties of natural gas.

8. You can use any friction factor
correlation in RPA!
0.9 16 16
7 k 37530
A2 2.457. ln 0.27. A3
Re D Re
1 k=Roughness in feet
12
12
8 1
f 8. D=inside diameter in feet
Re 3
2
A2 A3 Re= Reynolds number
1.1098
k
0.8981
D 7.149
A4
2.8257 Re
2
1 .4
f k=Roughness in feet
k
D 5.0452 . D=inside diameter in feet
4. log log A 4
3.7065 Re
Re= Reynolds number

12. Thank You for
Your Attention