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‘Investigation into the Limit State Design of XHPHT PIP Flowlines using
Local and Global Finite Element Analysis Methods’
May 2008
OTC 19372, Houston.
Paul Jukes, Jason Sun, Ayman EltaherJ P Kenny, Inc., Houston, USA.
Overview of Presentation• Introduction :
– Design Challenges
• Limit State Based Design
• SIMULATOR
• Global and Local FEA Models
• Conclusions
Introduction : Design Challenges
• 10,000ft (3000m) WD• Hydrostatic Collapse• Installation Issues
• Pressure 700bar (10,000psi)• Temperatures 177°C (350°F)• High Thermal Performance
Deepwater
HP / HT
• Span Length > 200m (660ft)• Multimode Vibration• Limitations of Design Codes
Super Spans
Introduction : Why Use Advanced FEA?
• Highly Non-linear Problems• Not Possible with Stress Based Design• ‘Added-Value’• Deepwater & HT Solution• Optimize Design Solution• Significant Financial Savings!!
Limit State Based Design
Advanced Analysis Tools
Limit State Based Design
Overview:• Limit States:
– Local Buckling– Hoop Ratcheting– Strain Capacity– Low cycle Fatigue
• Codes/Guidance:– HOTPIPE, DNV OS-F101, – DNV-RP-F110, SAFEBUCK,– API-1111
• Advanced Finite Element Analysis Tools
‘Simulator’ FEA
190
192
194
196
198
200
202
1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100
Distance Along Pipeline [m]
Lat
eral
Pos
ition
[m]
Embedded Boulders
Advanced Analysis Tools
‘Simulator’ Suite
• Tailored Software• ABAQUS FE Engine• Calibrated• Highly non-linear• Single Pipe/PIP
Steel Flowline
Thermal Insulation
Outer Steel Sleeve
Protective Coating
Corrosion Coating
‘Simulator’ Suite Gold Standard
• ‘Gold Standard’ Finite Element Models– Reeling Analysis – Lateral Buckling Analysis – Upheaval Buckling Analysis– Spanning and VIV Analysis – Trawlboard Pullover 180
185
190
195
200
205
1800 1850 1900 1950 2000 2050 2100 2150 2200
Distance Along Pipeline [m]
Lat
eral
Pos
ition
[m]
190
192
194
196
198
200
202
1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100
Distance Along Pipeline [m]
Lat
eral
Pos
ition
[m]
Embedded Boulders
‘Simulator’ Suites
Soil Friction Model – User Subroutine
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 1 2 3 4 5 6 7 8 9 10Lateral Movement, in
Fric
tion
Fact
or
Upper Bound
Mean Value
Lower Bound
Examples : Spans and VIV Analysis
Phase 7 Trunkline Free Span Exceeding Fatigue Limits within 25 Year Design Life74
74.5
75
75.5
76
76.5
77
77.5
7828.9 28.9 28.9 28.9 28.9 29.0 29.0 29.0 29.0 29.0 29.1
KP (km)
Wat
er D
epth
(m)
Seabed
Bottom of Pipe (operation condition)
• Detailed Span and VIV Analysis• Modal Analysis• ‘Added Value’
– Reduced Intervention
Examples : Lateral Buckling Simulation
-20
0
20
40
60
80
100
120
350 450 550 650 750 850 950
Pipe Distance, ft
Late
ral D
ispl
acem
ent,
in
36F49F69F80F95F110F120F134F146F165F180F
• Post Buckle Formation• Limit State Based Design• ‘Added Value’• Thermal Buckle Management
Examples : Pipeline Walking Analysis
0
20
40
60
80
100
120
140
160
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Pipe Distance, ft
Tem
pera
ture
, F
0.0844494 [h] 0.250011 [h] 0.416798 [h] 0.583757 [h]0.750233 [h] 0.916866 [h] 1.00023 [h] 1.16706 [h]1.33336 [h] 1.50014 [h] 1.66668 [h] 2.00018 [h]3.00019 [h] 7.00009 [h] 48.0001 [h]
-20
-10
0
10
20
30
40
50
60
0 1 2 3 4 5 6 7 8 9 10
Operating Temperature Cycle
Axi
al D
ispl
acem
ent (
in)
D6D7
+ : From D6 to D7- : From D7 to D6
Examples : Reeling & Lateral Buckling
Overview• Long model
– 250m reeling– 500m lateral
• PIP• Ultimate Limit States.
Pipe
Ramp Aligner
Tensioner
Straightener
Reel
Global and Local FEA Study
Advanced Analysis Tools
180
185
190
195
200
205
1800 1850 1900 1950 2000 2050 2100 2150 2200
Distance Along Pipeline [m]
Lat
eral
Pos
ition
[m]
‘Global’ PIP FE Model
Loadshare
1,500m (4,921ft)
Spacer, 2m (6ft)Inner Pipe
Outer PipeSleeper
Seabed Friction
Friction Coefficient 0.2
Element Selected
• PIPE31H, 3D Pipe Element– Inner Pipe– Outer Pipe
• ITT31, 3D Tube-to-Tube Contact Element– Spacer
• CONN32, Connector Element– Loadshare– Sleeper– Boundary
‘Local’ Full Size PIP FE Model
Composition of 3D PIP FE Model
• 4-node 3D shell element, S4R– Inner Pipe– Outer Pipe
• 8-node 3D stress element, C3D8R– Spacer– Bulkhead
• Constraint– Spacer to Inner Pipe– Pipeline to Bulkhead
• Interaction/Contact– Spacer to Outer Pipe
Pipeline Data To Build FE Model
0.591 (15.0)0.787 (20.0)Wall Thickness inch (mm)
12.750 (0.324)8.625 (0.219)Diameter inch (m)
490 (7850)490 (7850)Density lb/ft3 (kg/m3)
X70X70Pipeline Material
Outer PipeInner Pipe
Pipe Material & GeometryParameter
• Pipe and Geometry
Pipeline Data To Build FE Model
1.31 x 10-5
(13.1 x 10-6)6.5 x 10-6
(11.7 x 10-6)Coeff. Thermal Expansion
°F-1(°C-1)
72.4 (499)82.7 (570)SMTS ksi (MPa)
61.2 (422)70 (482.6)SMYS ksi (MPa)
0.30.3Poisson Ratio
29.9 x 106 (206)30.0 x 106 (207)Material Modulus psi (GPa)
Temp 350°F(177°C)Temp 68°F(20°C)
Pipe PropertiesParameter• Material and Operating Condition
350 (177)Design Temperature °F (°C)
6,500 psi (44.8 MPa)Inner Pressure MAOP psi (MPa)
40 (4.4)Seabed Temperature °F (°C)
4,500 (1,371.6)Water Depth WD ft (M)
Pipe Operating ConditionParameter
Results
Global and Local FEA Study
Study Case #1: Straight Pipeline vs. Lateral Buckled Pipeline
Pipeline Buckles with Initial Imperfection
Lateral Buckle Releases Inner Pipe Compression
Inner Pipe Axial Force
-750
-700
-650
-600
-550
-500
-450
-400
-350
-300
2 822 1642 2462 3282 4103
Pipeline Distance (ft)
Axi
al F
orce
(kip
s)
Buckled Axial Force, Inner Pipe Not Buckled Axial Force, Inner Pipe
Local FEA Response
•Pipeline
3D Helix of Inner Pipe Under XHT @350°F (Scale x80)
Inner Pipe Displacement Relative to Outer Pipe(Lateral Direction)
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
0.30
0.40
356 534 712 890 1069
Distance (ft)
Dis
plac
emen
t (in
)
Local Stress and Strain Response
• Inner Pipe lateral Displacement
3D Helix Observed in Buckled Global PIP Model (Scale x400)
•Data off Buckle Region
3D Helix of Inner Pipe Under XHT (Scale x100)
Local Stress and Strain Response
•Inner Pipe
Local Stress and Strain Response
•Outer Pipe
Local Stress and Strain Response
•Spacer
Full Size PIP FE vs. Global PIP Model
-19.2-21.5-9.3-7.317.919.1Outer Pipe
34.229.1-33.6-36.658.457.0Inner Pipe
3D FEGlobal FE3D FEGlobal FE3D FEGlobal FE
Hoop StressAxial StressVon Mises Stress
Peak Stresses (ksi)Parts
• Good Match between Local (3D) and Global FE Results
Limit State Results : Local Buckling
0.196N/AAPI
0.7440.060DNV, DC
0.9830.922DNV, LC
1,000m (3,050ft)
0.281N/AAPI
0.8030.070DNV, DC
1.0470.964DNV, LC
1,500m (4,920ft)
0.382N/AAPI
0.8670.080DNV, DC
1.1591.008DNV, LC
No Sleeper
Outer PipeInner Pipe
Limit State Unity CheckDesign CodeSleeper Intervals
Limit State Results : Hoop Stress Ratcheting
0.8850.9871,000m (3,050ft)
0.9951.0731,500m (4,920ft)
1.0301.125No Sleeper
Outer PipeInner Pipe
Limit State Unity Check
Sleeper Intervals
Limit State Results : Strain Capacity
0.1800.1781,000m (3,050ft)
0.3060.2731,500m (4,920ft)
0.2930.279No Sleeper
Outer PipeInner Pipe
Limit State Unity Check
Sleeper Intervals
Limit State Results : Low Cycle Fatigue Check
2984341,4892,170Outer
1,9508899,7494,444Inner1,000m (3,050ft)
2103061,0481,528Outer
1,5176927,5863,458Inner1,500m (4,920ft)
1992759441,376Outer
1,3145996,5712,996InnerNo Sleeper
Class FClass DClass FClass D
DNV Factored No. of Cycles
Allowable No. Cycles
PipeSleeper Intervals
Conclusions
Global and Local FEA Study
Conclusions
• A Global & Local PIP FE model presented
• Local full size PIP FE model,– Pipeline response at component
level• Global and Local FE models present
comparable results• Limit State Based Design• Allows Deepwater XHTHP PIP Designs• Advanced FEA is the way forward!
Global and Local FEA Study
Thank you!Any Questions?
‘Investigation into the Limit State Design of XHPHT PIP Flowlines using
Local and Global Finite Element Analysis Methods’
May 2008
OTC 19372, Houston.
Paul Jukes, Jason Sun, Ayman EltaherJ P Kenny, Inc., Houston, USA.