Post on 06-Mar-2018
transcript
STATE OF THE ART
PIPELAY ANALYSIS
Paper presented by:
Herman Perera
ZEE Engineering Sdn
Bhd
In association with:
Tarun Rewari
Aryatech Marine &
Offshore Services Pt Ltd
IORS 2013 CONFERENCE 20TH ANNUAL
INDIA OIL & GAS REVIEW SUMMARY & INTERNATIONAL EXHIBITION
INTRODUCTION
• Demand for Submarine Pipelines are increasing, due to
• Increase in Energy requirements for domestic use and industrialization resulting in;
* New Lines
* Rehabilitation / Replacement of existing lines
* Marginal field development
INTRODUCTION (cont.)
• Transport lines (larger diameter and longer)
– Standard DLB needs to be used
• In-field lines and marginal field development (smaller diameter, shorter)
– Non traditional methods need to be considered
* Surface tow (Rentis)
* On/Off bottom tow
* Variance of above
• For both cases Installation is a major cost driver
INTRODUCTION (cont.)
• Installation costs depend on;
– Offshore spread
– Methodology adopted
• Optimization of Installation costs
– Reduction of facilities
* Tensioner
* Wincher, davits etc.
• Enables companies to have larger contractor base for competitive bidding
• Enables contracts saving of cost by using optimum facilities such as reduction in tension.
OBJECTIVE OF PAPER
- To present a software package verified by
• Model test
• Field data
- Software package presented, OrcaFlex
- Computer Simulation depends on Methodology
• Static
• Dynamic
• Pseda- Dynamic
- OrcaFlex carries out large deflection, non-linear time domain analysis
BACKGROUND
• Over 25 years experience in submarine pipeline design
• Completed nearly 250 pipelines
• Has developed pipeline installation software
• Has used a number of industry-approved pipeline installation software packages
- Ansys - Pipeline
- Marcs - OrcaFlex
- Sesam - Offpipe
• We are not condemning or criticizing any software, merely sharing our experience.
• This presentation is based on our personal views
PIPELAY ANALYSIS
Submarine pipeline from mainland to Labuan island to supply fresh water.
EPCC Contractor
• Kencana/Lleighton Joint Venture (KLJV)
Line Description
• 26 inch diameter, approx. length 23.0km
• Wall thickness 9.5mm
• Steel API 5L x 52
• Weight Coating
– Concrete density of 2.4MT/m3
– Varying thickness of 125mm to 75mm
• Reinforcement 32nos 8mm steel rods will 8mm rings at 80mm CRS.
• Concrete cast in moulds and compacted
• Water depths 26m to 1.0m
Labuan Pipeline (Malaysia)
A Case Study
PIPELAY ANALYSIS (cont.)
Project was interesting as a number of lay methods were used
Installation Methods • Traditional “S” lay • Surface Tow (Rentis) • Shore Pull • Mid-point tie-in • Riser stack-in
- For all the methods single program OrcaFlex was used. • Single data file • QA/QC made easy.
A Case Study
PIPELAY ANALYSIS (cont.)
• The pipelay operation was attempted by a contractor and abandoned due to buckling at each joint.
• As the supply of water to Labuan (a tourist destination) was vital the project became a political issue.
- FAILURE
The second attempt by (KLJV)
• Tight Schedule
• Closely monitored by Ministry and Third Party
Consultants
• Was successfully concluded
A Case Study
- SUCCESS
- PRELIMINARY ACTION
• Pipeline was sandblasted for slippage at tensioner
• Establish pipeline stiffness
* Large diameter, thin walled line with large concrete weight
* Lessons learned from earlier failure
• Pipeline stiffness
* Consultant was of the opinion that the stiffness of the full
composite section should be considered.
* Preliminary analysis showed the full composite section stiffness was
note practical.
* ZEE proposed to use ASME paper recommendations for pipeline
stiffness.
PIPELAY ANALYSIS (cont.)
A Case Study
- The stiffness related to the pipeline are:
Source Stiffness (mm4) % of Bare Pipe
Bare Pipe 1.029E + 09 100.00
Full Composite 4.318E + 09 419.631
ASME Paper 1.520E + 09 147.716
PIPELAY ANALYSIS (cont.)
A Case Study
PRELIMINARY ACTION
- Analysis options:
* Stiffness of bare pipe + weight of concrete coating
* Stiffness of Composite Section + weight of concrete coating
* Stiffness as per ASME Paper + weight of concrete coating
- Preliminary Analysis
* Option 1: Touch down point close stresses very large
* Option 2: Touchdown point very far. Lessen Bending Moments, Large Tension
* Option 3: Acceptable results (our opinion)
- Action Adopted
* The effective stiffness was critical
* Decided to carry out model test for verification
PIPELAY ANALYSIS (cont.)
A Case Study
MODEL TEST • Theoretical
– Test model was set up as recommended in the ASME paper.
– Note that the centre of model is in bending with minimal shear (similar to actual pipeline behaviour)
- MODEL TEST
* Full scale Model Test carried out
* Two pipeline joints with 125m,
concrete coat thickness were
field- welded
* 2 equal loads were applied
simultaneously
* Strain gauge incorporated at
center of model (field joint)
* Strain measurements were
recorded at each weight
increment
* Test was carried out to collapse
PIPELAY ANALYSIS (cont.)
A Case Study
- MODEL TEST
* Physical measurements same as per actual test. * Stiffness as per ASME paper was adopted. * Finite Element model was segmented as per stiffness variations. * Load increments and steps were identical to the actual test.
PIPELAY ANALYSIS (cont.)
A Case Study
COMPUTER MODEL OF PIPELINE FOR STIFFNESS EVALUATION
- MODEL TEST
- Results (Model Test) & Computer Simulation * Strains vs Stiffness graph * Very close match * Observations
– Initial stiffness of composite section solely to self weight
– As the load increased gradual debonding of reinforced bars and cracking of concrete resulting in reduction of stiffness.
– At collapse the effective stiffness was close to that of bare pipe.
PIPELAY ANALYSIS (cont.)
A Case Study
- MODEL TEST
* Stiffness is proportional to the bend Radius.
* For absolute accuracy the pipelay computer model should be incorporated with
varying stiffness along the line.
* This will result in a very complex F.E model requiring long computer time for
simulation/results.
* It was decided to adopt a single pipeline stiffness.
* STIFFNESS AT PIPELAY
PIPELAY ANALYSIS (cont.)
A Case Study
* As per DnV (1981) the criteria
set for pipelay at sag bend is 85%
SMYS.
* It was decided to adopt stiffness
value at maximum bending range
just before the cracking of the
weight coat.
* The stiffness value is approximately
equal to 145% of bare pipe
* The stiffness is as per ASME paper
recommendation
RECOMMENDED PIPELINE STIFFNESS
- MODEL TEST
PIPELAY ANALYSIS (cont.)
A Case Study
PRELIMINARY ANALYSIS
• Two analyses were carried out to check
– Accuracy
– Simulation Time
• FE MODELS
PRELIMINARY ANALYSIS
• For both cases standard pipelay analysis was carried out the following were taken into consideration:
* Physical properties of bare pipe * Weight of concrete coating * Buoyancy * Hydrodynamic properties
• Full dynamic simulations were carried out with: * Tension of 750km * Maximum water depth * Waves and current heading 0.0 deg * Buoyancy bags not considered.
PIPELAY ANALYSIS (cont.)
A Case Study
- PRELIMINARY ANALYSIS
* Detailed simulation gave least stresses in the
pipeline system spiking at field joint locations.
This is realistic.
* Standard simulation produced higher stress
values but with a smoother curve.
* Detailed simulation took 600% of computer time
of standard simulation.
* Considering 8 stimulations for each water
depth, and actual time taken for each simulation,
it was decided to adopt the standard model for
study.
* This will give conservative results.
Analysis Max OB
Stress
(MPa)
Max SB
Stress
(MPa)
Touch down
Point (m)
Standard 695.4 453.2 238.5
Detailed 412.0 399.6 172.5
COMPARISON OF RESULTS
PIPELAY ANALYSIS (cont.)
A Case Study
- COMPUTER SIMULATION
* Coupled time domain dynamic simulation was carried out along the pipeline route considering:
– Water depth
– Weight coat thickness
* The pipeline system was over-stressed both in over and sagbend locations.
* Buoyancy system needed to be incorporated.
* 2 ½ tan buoyancy bags were used.
* 8-directional analysis were carried out for each location.
* Typical buoyancy system.
PIPELAY ANALYSIS (cont.)
A Case Study
- COMPARISON OF RESULTS
* Analysis vs Field measurements
* Field measurements only carried out for:
– Water depth
– Touchdown point
PIPELAY ANALYSIS (cont.)
A Case Study
COMPARISON OF RESULTS
KP
Water Depth Touch down Tensioner Stress
(meter) (meter) (MT) % SYMS
Analysis Field
Measurement Analysis
Field
Measurement Analysis
Field
Measurement Overbend Sagbend
46 18.64 15.6 188.7 194 60 55 61 62
45 18.64 17.7 188.7 230 60 65 67 89
44 24.14 19.2 177.5 - 207 191 80 78 77 84
43 24.14 20.2 177.5 - 207 183 80 80 77 84
42 24.14 20.6 177.5 - 207 187 80 80 77 84
41 24.14 20.4 177.5 - 207 176 80 80 77 84
40 24.14 20.2 177.5 - 207 183.7 80 80 77 84
39 24.14 18.2 177.5 - 207 187 80 80 77 84
38 24.14 18.5 177.5 - 207 176 80 75 77 84
37 24.14 17.9 177.5 - 207 181.2 80 75 77 84
36 24.14 17.3 177.5 - 207 205 80 77 77 84
PIPELAY ANALYSIS (cont.)
A Case Study
- COMPARISON OF RESULTS
• Deviations of results within +/- 10%.
• Close match except at kp 45 (possibly field measurement error)
• Deviations possibly due to
* Variance in water depths
* Variance in tensioner
* Non-consideration of waves and currents for field measurements
- OBSERVATIONS
CONCLUSIONS
• Orcaflex program results closer to – Model Test – Field Measurements
PIPELAY ANALYSIS (cont.)
A Case Study
ADVANTAGES OF USING ORCAFLEX
• Many Advantages
- Limited time to go through
• Main Advantage
- Continuous Simulation
- Speed of vessel
- Optimization of forces on jacket/ dead Anchor
ORCAFLEX SIMULATIONS
Installation Bowline Davit Lift Installation Bowline
Stress Profile
Davit Lift Stress
Profile
Laydown Laydown Stress
Profile
RAPID RESPONSE
• Shore to SPM, through Reef • Pipelay delay • Commencement of Monsoon • Waves 4-5 meter height, designed for max 2m • Pipeline buckling at each joint • Field measurement were sent to office • Within 2 days accurate models were compiled & solution given • Pipeline successfully laid.
SRI LANKA CPC MUTHURAJAWELA PROJECT
Worst Case Solution
INNOVATIVE ENGINEERING
- RENTIS LINE
Towed 65 Miles and Installed between 2 Platform
Pipeline Bundle 8” concrete coated + 4” Fabricated onshore
INNOVATIVE ENGINEERING (cont.)
- EUROSPIRAL PIPELAY
Spiral Pipelay
Stress Profile
FUN ORCAFLEX DEMO
Boy Scout
FUN ORCAFLEX DEMO
Trampoline
FUN ORCAFLEX DEMO
Surfing Dog
FUN ORCAFLEX DEMO
Tire
THANK YOU