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Figure: Pipe Design Concept: S S SS S

This document provides details for the design of steel pipe for the Long Phu 1 Thermal Power Plant project in Vietnam. It includes: - Project and client details, as well as the package and item being designed. - Design parameters and calculations for the minimum required pipe wall thickness based on internal pressure and handling conditions. A choice of 27mm wall thickness is made. - Calculation of equivalent stress in the steel pipe considering circumferential and longitudinal stresses from various sources. - Buckling check calculations considering dead and live loads on the pipe to ensure the allowable buckling pressure is not exceeded.

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227 views2 pages

Figure: Pipe Design Concept: S S SS S

This document provides details for the design of steel pipe for the Long Phu 1 Thermal Power Plant project in Vietnam. It includes: - Project and client details, as well as the package and item being designed. - Design parameters and calculations for the minimum required pipe wall thickness based on internal pressure and handling conditions. A choice of 27mm wall thickness is made. - Calculation of equivalent stress in the steel pipe considering circumferential and longitudinal stresses from various sources. - Buckling check calculations considering dead and live loads on the pipe to ensure the allowable buckling pressure is not exceeded.

Uploaded by

NobitaKun
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Project Name

Client
Package
Item
Prepared by
Checked by
Date

:
Long Phu 1 Thermal Power Plant
:
Vietnam oil and gas group
:
CW & ACW PIPING
:
Design the steel pipe
: Nguyen Xuan Tung
Sig.
: Le Ngoc Hiep
Sig.
:

Figure: Pipe design concept


I. Datas
Standard: AWWA M11- Steel Water Pipe: A Guide for Design and Installation
Design Internal Pressure
P
Tmax
Design Temperature
Average temperature (assume)
To
Maximum of different temperature
DT
Steel materials
ASTM
Fy
Yielding point limit
Allowable stress for design is taken as 50% of yeilding
[S]=Fy/2
point limit
Modulus of elastic for steel
E
Outside diametre of pipe
D
Unit weight of cover soil
w
Hc
Depth of cover soil
Type of soil
Relative compaction

0.5
50
26.8
23.2
A36
250

MPa
C
C
C

(5 atm)

MPa

125 MPa
206842.71 MPa
(3*107 psi)
3.754 m
20 kN/m3
5.55 m
Assume
SM-Poorly graded sands
90%

II. Calculation
II.1. Calculate the minimum required thickness of wall pipe as internal pressure and handling condition
- Internal pressure condition
Required thickness of wall pipe
t=PD/2[S]
7.508 mm
Eq. 4-1
- Handling condition
Minimum wall thickness of pipe
tmin=D/240
for motar-line and flexible coated steel pipe
15.64 mm
Eq. 4-7
t=max(t,tmin)
Choice
27 mm
II.2. Calcuate stress in steel pipe
The equivalent stress shall be calculated in accordance with Hencky- Mises theory:

Se = S x2 S x S z S z2

Eq. 7-9

In which: Sx and Sz are principles stress

DN3700

iv-1

a. Circumferential stress- Sx
Tensile sress due to internal pressure
Circumferential bending stress due to external pressure
Shape factor
Calculation deflection
Deflection lag factor, for pressure pipe, because long-term
deflection are largely prevented by the supporting action
of the internal hydrostatic pressure.
Bending constant
Pile walls stiffness
Stranverse moment of inertia per unit length of
individuaal pipe wall components-Depend on depth of
cover soil, type of soil amd relative compaction

Sx=Sr+Sb1
Sr=PD/2t
Sb1=Df*E*(Dy/D)*t/D
Df

Modulus of soil reaction


Load per unit pipe length
Live load-effect- may be highway loading or railroad
loading
Dead load on conduit
Vertical deflection of pipe
Check
b. Longitudinal stress- Sz
Stress due to poisson's effect
Poisson ratio of steel
Temperature stress
Coefficient od linear expansion
Equivalent stress
II.3. Check for buckling
Dead load of soil pressure on pipe
Height of backfill soil
Live load of highway loading and Railroad loading

E'
W=Wc+Wl

Total external load


- Calculate allowable buckling pressure by formular:

W=Wd+Wl

Dl

K
EI

0.1
339.27 kNm

I=t3/12

1640 mm3
10340 kN/m2
416.694 kN/m

Wl

Tab. 6.1

Wc=w*Hc*D
Dy=DlKWr3/(EI+0.06E'r3
Dy/D
Sz=Sv+St
Sv=u*Sr
u
ST=a*E*DT
a
Se

416.694
0.062
2%
10485.36
10427.778
0.3
57.59
0.000012
115917.14

Wd=w*H
H
Wl

qa =
Water buoyancy factor
Height of water surface above top of pipe
Height of ground surface above top of pipe
Empirical coefficient of elastic support
Design factor
Allowable buckling pressure
Check

120803.60 kPa
34759.26 kPa
86044.34 kPa
3.5

kN/m
m
OK
kPa
kPa
kN/m
mm/C
kPa

111 kN/m2
5.55 m
0 kN/m2
111 kN/m2

1
EI
32 R B ' E ' 3
FS
D

R=1-0.33(hw/h)
hw
h
B'=1/(1+4*e(-0.213H))
FS
qa
W/qa

DN3700

Eq. 6-4
Eq. 6-5

Eq. 6-7
1
0
2
0.2196
2
341.3
33%

m
m

kN/m2
OK

iv-2

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