2009w_engi_8673_a02_solution.pdf

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ENGI 8673 Subsea Pipeline Engineering

Faculty of Engineering and Applied Science

Shawn Kenny, Ph.D., P.Eng. Winter 2009

Assignment #2 Page 1 of 1

ASSIGNMENT #2(DUE: MARCH 2,2009)

Instructions: To demonstrate comprehension of the subject matter and to prepare for the finalexamination, include a handwritten sample calculation for each unique calculation required in each

problem. For repetitive calculations, the use of electronic calculation packages (e.g. Excel, Matlab) are

allowed. Sufficient information, which may include text, tables or figures, must be included to demonstrate

the problem set requirements have been satisfied.Problem 2-1 An arctic offshore gravity base platform has an oil riser traversing within the in-air working

space and is supported by an anchor block. The pipeline has a 273.1mm nominal outside diameter with

9.525 mm wall thickness. The material properties include an elastic modulus of 205 GPa, Poissons ratio

of 0.3 and coefficient of thermal expansion of 1.1510-5

m/m/C. The installation tie-in temperature is

-25 C and the operating temperature is 75C. The design pressure is 12 MPa. As the distance from the

design pressure reference height to the pipeline elevation is typically small, the effects of a static fluidcolumn on internal pressure can be ignored. Calculate the longitudinal stress, equivalent stress and

deflection for the pipeline within the anchor block. If the linepipe is DNV SMLS 360, does the pipeline fail

the von Mises stress check? [50]

Problem 2-2 For the pipeline in Problem 1-1, calculate the virtual anchor length, axial end displacement

and axial stress at the anchor point for a buried pipeline. For these calculation assume the pipeline has

no concrete coating or anti-corrosion coating. Assume a undrained cohesive soil strength of 25kPa and

0.25 adhesion factor. Does the pipeline fail the von Mises stress check? [50]


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EN 8673 Subsea Pipeline Engineering Assignment 2Problem 2-02

Winter 2009

DEFINED UNITS

MPa 106Pa kPa 10

3Pa GPa 10

9Pa C K kN 10

3N

PIPELINE SYSTEM PARAMETERS

Nominal Outside Diameter Do 273.1mm

Initial Selection Nominal Wall Thickness (Sec.5 C203 Table 5-3) tnom 9.525mm

External Corrosion Protection Coating Thickness tcpc 0mm

Fabrication Process (Sec.7 B300 Table 7-1) [SMLS, HFW, SAW] FAB "SMLS"

Corrosion Allowance (Sec.6 D203) tcorr 3mm

Elastic Modulus E 205GPa

Specified Minimum Yield Stress (Sec.7 B300 Table 7-5) SMYS 450MPa

Speciifed Minimum Tensile Stress (Sec.7 B300 Table 7-5) SMTS 535MPa

Coefficient of Thermal Expansion T 1.15 10

5

C1

Poisson's Ratio 0.3

Pipeline Route Length Lp 2.5km

Linepipe Density s 7850kg m3

Concrete Coating Thickness tc 0mm

Concrete Coating Density c 3050kg m3

OPERATATIONAL PARAMETERS

API Gravity API 38

Product Contents Density

cont 1000 kg m3

141.5

131.5 API cont 835m

3kg

Design Pressure (Gauge) Pd 12MPa

Design Pressure Reference Level href 0m

Operational Temperature To 75 C

Tie-in Temperature Tti 25 C

Maximum Water Depth hl 0m

Seawater Density w 1025kg m3

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Winter 2009

GEOTECHNICAL PARAMETERS

Undrained Shear Strength Cu 25kPa

Adhesion Factor soil 0.25

SOIL RESISTANCE PARAMETERS

Soil Axial Restraint per Unit Length (Eqn B-1 ALA 2001)

f Do Cu soil f 5.36 kN m1

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Winter 2009

DNV OS-F101 PARTIAL FACTORS AND DESIGN PARAMETERS

Material Strength Factor - Operations (Sec.5 C306 Table 5-6) U_o 0.96

Wall Thickness Fabrication Tolerance(Sec.7 G307 Table 7-18)

tfab 0.5mm FAB "SMLS"=

tnom 4mmif0.125 tnom FAB "SMLS"= tnom 4mmif

0.125 tnom FAB "SMLS"= tnom 10mmif

0.100 tnom FAB "SMLS"= tnom 25mmif

3mm FAB "SMLS"= tnom 30mmif

0.4mm FAB "HFW"= tnom 6mmif



0.5mm FAB "SAW"= tnom

6mmif

0.7mm FAB "SAW"= tnom 6mmif



tfab 1.2 mm

Material Derating (Sec.5 C300 Figure 2)

SMYS_o 0MPa To 50Cif

To 50 C 30MPa

50 C

50 C To 100Cif

30MPa To 100 C 40MPa100 C

otherwise

SMYS_o 15.00 MPa

SMTS_o 0MPa To 50Cif

To 50 C 30MPa

50 C

50 C To 100Cif

30MPa To 100 C 40MPa

100 C

otherwise

SMYS_o 15.00 MPa

fy_o SMYS SMYS_o( ) U_o fy_o 418 MPa

fu_o SMTS SMTS_o( ) U_o fu_o 499 MPa

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Winter 2009

ENGINEERING ANALYSIS

PIPELINE GEOMETRIC PROPERTIES

Inside Pipeline Diameter (Operations Case)

Di_o Do 2 tnom tcorr tfab Di_o 262.4 mm

Inside Pipeline Radius (Operations Case)

Ri_o 0.5 Di_o Ri_o 131.2 mm

Mean Pipeline Radius

Rm 0.5 Do tnom Rm 131.8 mm

External Hydrostatic Pressure

Pe w g hl Pe 0.00 MPa

HOOP STRESS (THIN WALL THEORY)

hPd cont g href hl Di_o Pe Do

2 tnom tcorr tfab h 295.2 MPa

DISTANCE TO VIRTUAL ANCHOR POINT

- Equation 9 of Palmer and Ling (1981) OTC4067

- Eqn (12.17) L12 Guidance Note

z Pd Rm

2

f1 2

2 tnom

Pd RmE T To Tti

z 396m

Virtual Anchor Length Check

zchk "VIRTUAL ANCHOR OK" z 0.5 Lpif

"RECALCULATE" otherwise

zchk "VIRTUAL ANCHOR OK"

AXIAL END DISPLACEMENT

Eqn (12.19) L12 Guidance Note

endPd Rm

2 E tnom1 2( ) T To Tti

z

f z2

4 E Rm tnom end 260 mm

Axial End Displacement [Equation 12 - Palmer and Ling (1981) OTC 4067]

Palmer

Rm E tnom T To Tti 2

f1

Pd Rm1

2

E tnom T To Tti

2

Palmer 260 mm

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Winter 2009

LONGITUDINAL STRESS

- Eqn (12.16) L12 Guidance Note

Axial Stress (For X =Z)

l

Pd Rm

tnom

E T

To Tti

l 185.9

MPa

EQUIVALENT STRESS CHECK

eq h2

h l l2

eq 420.2 MPa

eqchk "EQUIVALENT STRESS OK" eq 0.9 fy_oif

"INCREASE WALL THICKNESS" otherwise

eqchk "INCREASE WALL THICKNESS"

26/02/2009 Page 5 of 5

2009w_engi_8673_a02_solution.pdf

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