Upheval Bukling Calculation

Cairn Energy India Limited UPHEAVAL BUCKLING CALCULATIONS JP Kenny

Rev 1

CLIENT

Cairn Energy India Limited

SUBJECT

24" Crude Oil Pipeline

DOC NO.

05 2893 - 03 - P - 2 005

PRPD BY PDoc 24/04/2007 11.1mm wall PDoc 17/05/2007

CHKD BY CHKD BY

JOB NO.

52893.03

.

REV NO.

1

.

GMurdoch 27/04/07 APP'D BY Jt Chohan21/05/07 APP'D BY

P Doc 05/05/07 P Doc 21/05/07

2

1.0 INTRODUCTION The aim of this calculation is to determine the downforce required on the pipeline to prevent upheaval buckling as a result of axial compression. 2.0 METHOD The required downforce is calculated using an equation developed by Ellinas and Palmer (Ref 1). The required downforce is dependant on the axial force which is calculated in the the Thermal Expansion Calc Sheet. An imperfection height of 0.2m is introduced to allow for changes of gradient in the trench. 3.0 INPUT DATA The input data for this calculation has come from: Reference 1: ASME B 31.4 and OISD - STD - 141 Reference 2: Refer to Wall thickness Report 052893-03-P-3-020 and Calcs 002 to 010 Reference 3: API 5L X65 Line Pipe

4.0 CALCULATIONS 4.1 Input Data Max. Operating Pressure

P

=

9.0

Nom. Outside Diameter

D

=

0.6096

Pipe Material Specified Min. Yield Strength

MPa

=

90

barg

m

=

24

in

=

11.1

API 5L X65 SMYS =

448

MPa mm

Wall Thickness

wt

=

0.011

Depth of Cover

h

=

1

Modulus of Elasticity

E

= 2.06E+11 Pa

Density of Steel

ρs

=

76,420

3

N/m

=

7790

kg/m3

Density of Soil

ρg

=

14,862

N/m3

=

1515

kg/m3

Density of Contents

ρi

=

890

kg/m3

Uplift Co-efficient

Uc

=

0.2

Imperfection Height

Hi

=

0.2

Total Axial Force

Fa

= 4,639,987 N

03-P-2-005 Rev 01 - 24 inch Crude Oil Buckling.xls 21/05/2007

Page 1 of 3

mm

m =

206,000 MPa

(Ref 1) m (from Longitudinal Stress Calc) from 052893-03-P-2-010

Self Check........................... Date...........................

Cairn Energy India Limited UPHEAVAL BUCKLING CALCULATIONS JP Kenny 4.2 Longitudinal Stress - Restrained Pipeline Axs = pi()/4*(D^2-(D-2*wt)^2) Cross-sectional Area of Steel = Cross-sectional Area of Internals

Axi

m2

0.021

pi()*(D-2*wt)^2

=

4

Weight of Soil above pipe

Weight of Steel

Weight of Contents

Pipeline Weight

Moment of inertia

Step 1

Wg

Ws

Wi

Wc

I

za

=

0.271

=

ρg*h*D

=

9,060

=

ρs*Axs

=

1,595

=

ρo*Axi

=

241

=

W s+W i

=

1,836

m2

N/m

N/m

N/m

N/m

= pi()*wt*(D/2)^3 =

9.87E-04 m4

=

4.76*(E*I*W c/Hi)^0.5 Fa

= Step 2

zb

= (Hi*W/(E*I))^0.5 =

Required downforce

Lr

Total Download

Ur

Ld

0.001

= (1.16-za)*Fa*zb =

Soil Uplift Resistance

1.402

-1,508

N/m

= ρg*h*D*(1+(Uc*h/D)) =

12,032

=

Ur+W c

=

13,869

N/m

N/m

5.0 SUMMARY OF RESULTS The following table summarises the calculation results: Variable

Unit

Calculated

Download Required

N/m

-1,508

13,869 Total Download (soil + pipe) N/m As the Total download is greater than the Required download, upheaval buckling will not occur. Note we have not included the insulation in this calculation as it would only improve the situation making the area of ground at the buckle greater thus increasing the downward load by having a greater area thus larger soil loads

03-P-2-005 Rev 01 - 24 inch Crude Oil Buckling.xls 21/05/2007

Page 2 of 3

Self Check........................... Date...........................