Improving standards and technology towards achieving ... 2013/Temadag om... · pigging, FAT •...
Transcript of Improving standards and technology towards achieving ... 2013/Temadag om... · pigging, FAT •...
Improving standards and
technology towards achieving
robust design and safe
operation of flexible risers
Krassy Doynov, EMDC. PSA Flexible Risers Seminar - Stavanger - November 26, 2013
K. Doynov. PSA Flexible Risers Seminar - Stavanger - November 26, 2013. 2
Outline
1. Safe design practices accepted by Industry for incorporation into API 17J & B (2014 editions)
2. Key API 17J & B improvement areas from lessons learned by Industry over the last 15 years
3. Technology developments priorities
ExxonMobil Experience with Flexibles
K. Doynov. PSA Flexible Risers Seminar - Stavanger - November 26, 2013. 3
• 20 years design and operational experience
• Approximately 400km of installed risers, flowlines and jumpers
◦ Dynamic Subsea Offloading System, Risers to FPSO
◦ Dynamic Fluid Transfer Lines –TLP to FPSO, and Jumpers–
SHR to FPSO
◦ Quasi Static Surface Jumpers – Top Tensioned Riser
◦ Static Flowlines and Subsea Jumpers – Infield lines
• Geographical Spread – UK, Norway, West Africa, Canada, USA
• Water depth range: ~ 100-to-1800m
Outer sheath damage, Flooded annulus
K. Doynov. PSA Flexible Risers Seminar - Stavanger - November 26, 2013. 4
High Probability of Occurrence
• ~ 25% of all damages reported to Sureflex JIP 2009, OTC 21524-2011
• Similar numbers & causes in some of EM fields: installation, abrasion, blocked vent
ports, dragged moorings
Repair options
Water cannot be displaced from annulus. Clamp outer sheath damage to stop O2 inflow.
Key Failure Mechanisms
Corrosion, corrosion fatigue and accelerated aging of polymer layers causing “chain-reactions”
leading to tensile, burst, and fatigue failures.
Key Uncertainties
Remnant life and time to replacement. Wire corrosion fatigue and polymer aging capacity.
Key Technology Gaps
Difficult to inspect / monitor reliably:
• annulus conditions, wire stress, and number of broken wires in inner layers
• determine corrosion & aging status from annulus composition data
Lack of Industry:
• consensus on selecting testing frequency for establishing corrosion SN curves
• design & test methodology for synergistic effects (e.g., corrosion/aging + fatigue)
Design for Flooded Annulus
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EM Design and Qualification Testing Standard
• Inspection and monitoring should not be used to compensate for a lack of robust
design, even if they were both available and reliable
• Changed in 2005 to require:
◦ Design for flooded annulus conditions for the entire service life (installation
damage and repair)
◦ Design SN curve ensuring 97.5% probability of survival
2014 - 4th edition of API 17J and 5th edition of API 17B
• 2009 editions – design for dry annulus condition. Fatigue life for flooded annulus
provided for information only
• 2014 editions - design for flooded annulus condition:
◦ Condensed fluids in the annulus predicted assuming intact outer sheath
◦ Annulus flooded with de-aerated seawater (from installation damage and
repair)
◦ Annulus flooded with aerated seawater – as accidental case
◦ Impact on material selection and performance, and layer design for
associated degradation mechanisms (e.g., API17J, 5.3.2.7.4 “Antibuckling
tape structural capacity shall be defined as the minimum strength during the
pipe service life derived after accounting for aging and wear”)
Inner sheath damage – Smooth Bore
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Key Failure Mode - Repetitive collapse - rupture at end fitting entry
EM Design and Qualification Testing Standard
2005: use only rough bore pipes since repetitive collapse cannot be designed for
2014 - 4th edition of API 17J and 5th edition of API 17B
• 2009 editions – no design requirements; recommendations for collapse calcs, erosion,
pigging, FAT
• 2014 editions - Design requirements: 1) per manufacturer’s acceptance criterion, 2)
anticollapse sheath and its end fitting sealing, FAT testing, annulus pressure testing
Corrosion Reservoir Souring
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55-degree Flowline – loss of containment
• 90s design failed to predict souring of the reservoir
• Sweet wires fractured due to hydrogen sulfide
• Unsupported pressure sheath cracked
EM Design and Qualification Testing
• SSC/HIC test at 100% of actual yield / upper limit
of wire max local stress determined from FEA
• SSC/HIC test wire specimen with plastic strain and
residual stress levels representative of wires
retrieved from as manufactured pipes
Inner & outer armor wires
Inner pressure sheath
2014 - 4th edition of API 17J and 5th edition of API 17B
• 2009 editions SSC/HIC tests – test load = 90% of actual yield
• 2014 editions SSC/HIC tests
◦ To loads equal or exceeding calculated max local stress
◦ Test wire specimen with plastic strain and residual stress levels
representative of wires retrieved from as manufactured pipes
API 17 J&B Improvements
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Maximum Operating Pressure
Incidental Pressure
Design Pressure
In
creasin
g P
ressu
re
Operating Pressure
Test Pressure
Burst Pressure
Minimum Pressure
Temperature Definition
Operating Temperature
The internal (1) temperature profile experienced by the pipe over its service life during permanent normal operation
Maximum / Minimum Operating Temperature
The maximum and minimum internal temperature to which the pipe is subjected during permanent normal operation
Design Temperature
The maximum and minimum internal
temperature to which the pipe is subjected during permanent operation
Incidental(2) Temperature
The maximum and minimum internal temperature that is unlikely to be exceeded during the life of the pipe
Lessons Learned from 15 years
• All flexibles JIPs prior to FPT JIP
• FPT JIP (2005-2012) 19 companies
• ~800 comments (2012-2013) from rest of
Industry
• All areas - manufacturing, testing, design,
analysis - improved significantly
Test pressure
Factory acceptance test (FAT)
The internal pressure applied to the pipe or pipe section during testing after manufacture to test for latent defects. Unless otherwise specified by the purchaser, the FAT pressure is 1.5 times the design pressure for flexible risers and topside jumpers and 1.3 times the design pressure for flexible flowlines and subsea jumpers. If applicable, the maximum differential pressure can be used instead of design pressure.
Offshore leak test (OLT)
The internal pressure applied to the pipe or pipe section during testing after installation to test for leak tightness. Unless otherwise specified by the purchaser, the OLT pressure is 1.1 times either (a) the design pressure of the pipe or (b) system design pressure, whichever is lower.
SIT (on-board integrity test) (3)
The internal pressure applied to the pipe or pipe section during testing on-board the installation vessel to test the structural integrity of the pipe. Unless otherwise specified by the purchaser the structural integrity test (SIT) pressure shall be as per the FAT pressure.
SIT (offshore integrity test) (4)
The internal pressure applied to the pipe or pipe section during testing in situ after installation to test the structural integrity of the pipe.Unless otherwise specified by the purchaser the SIT pressure shall be 1.25 times either (a) the design pressure of the pipe or (b) system design pressure, whichever is lower.
API 17J Design Acceptance Criteria
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Layer Primary Pipe Failure Mode
Design Criteria
Operating Conditions Nonoperating Conditions
Survival Permanent
Abnormal
Temporary
Normal Extreme Normal
Extreme Installation Test
Internal carcass Collapse (1) (2) Load 0.85
Inner liner smooth bore Collapse (1) Load
For each polymer material for both static and dynamic applications, the allowable utilization for collapse shall be as specified by the manufacturer, who shall document that the material meets the design requirements at that load.
Internal pressure sheath
Rupture
Thinning (3) The maximum allowable reduction in wall thickness over the service life below the minimum design value, due to deformation into gaps in the supporting structural layer, shall be 30 % under all load combinations.
Strain
For each polymer material for both static and dynamic applications, the allowable bending strain shall be as specified by the manufacturer, who shall document that the material meets the design requirements at that strain.
The maximum allowable bending strain at nominal dimensions shall be 7.7 % for polyethylene (PE) and polyamide (PA), 7.0 % for polyvinylidene fluoride (PVDF) in static applications and for storage in dynamic applications, and 3.5 % for PVDF for operation in dynamic applications (4).
Pressure armors
Loss of interlock breakage
Stress 0.67 0.85 0.85 0.67 0.91 (9) 0.85 0.97 (5)
Collapse (1) (2) Load 0.85
Tensile armors
Breakage Stress 0.67 0.85 0.85 0.67 0.91 (9) 0.85 0.97 (5)
Buckling Load 0.85
Wire disorganization
Displacement The cumulative radial gap between each tensile armor and its adjacent layers shall not exceed half the wire thickness
Anticollapse sheath (6)
Rupture
Strain
For each polymer material for both static and dynamic applications, the allowable bending strain shall be as specified by the manufacturer, who shall document that the material meets the design requirements at that strain.
Antibuckling tape Birdcaging (7)
Stress or strain (8)
0.67 0.67 0.85 0.85 0.85 0.85 0.91
Outer sheath Rupture Strain
For each polymer material for both static and dynamic applications, the allowable bending strain shall be as specified by the manufacturer, who shall document that the material meets the design requirements at that strain.
The maximum allowable bending strain shall be 7.7 % for PE and PA.
Table 8—Flexible Pipe Layer Design Criteria
17J Pressure Armor Design Acceptance Criterion
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• Pressure armor allowable
utilization – 0.67 instead of
0.55 for normal conditions
• FPT JIP Burst Limit State
reliability study - FORM and
1,000,000 Monte Carlo
simulations
• 3 pipes designed, and
material properties provided,
by NKT, WIL, FF
• Accounting for the residual stresses in wires due to manufacturing and FAT
• Maximum local stress is below yield
• Successful HIC/SSC tests at max local stress determined from FEA
• Strain based design when stress exceeds yield, plus full scale fatigue test
17B Local Stress of Individual Wire
API 17 J & B Testing
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• Prototype, qualification, verification, validation test definitions added
• Property, testing and quality control requirements added for anti-buckling tapes
• Clarifications to FAT pressure test holding period and acceptance criteria
added to address interpretation requests received over the last 10 years
• Purpose-procedure-acceptance-criteria structure added to all FAT and
prototype tests
• Guidance on scaling/similarity assessment for qualification testing added
• 5 test levels and acceptance criteria for different test objectives added
Levels Strength Test Fatigue Test
1 FAILURE of pipe or end fitting Failure of pipe or end fitting
2 UTS of critical component Target SN curve of critical component
3 SMYS of critical component Damage Ratio=1.0 per design SN curve of critical component
4 AUF of critical component DAC (Damage Ratio=0.1) per design SN curve of critical component
5 MAX LOAD Maximum damage accumulated in the fatigue critical component in a service life
API 17 J & B Testing
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Fatigue Test Objective Destructive Non-Destructive
Qualify a flexible pipe for dynamic service Validation of
failure
predictions
Validation of design
methodology and
tools with measured
component response
Verify manufacturer stated fatigue performance
Validate service life design methodology and tools
Pipe Body Calculated Failure
Tension
End-fitting Calculated Failure
Tension
Design Acceptance
Failure tension is above
Failure tension is above
Accept both pipe body and end fitting
Failure tension is above
Failure tension is below
Accept pipe body. Change the EF design or de-rate the tension capacity. End-fitting design methodology is invalidated
Failure tension is below
Failure tension is above
Accept end fitting. Change the pipe design or de-rate the tension capacity. Pipe design methodology is invalidated
EM Corrosion Fatigue
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frequency
P(t)
Environment
f*
da/dN
air
environment
Industry practice Concern
Corrosion SN curves
virgin wires
Flooded annuli tend to create pits within <1year. Fatigue capacity of a pitted wire is different from the fatigue capacity of a virgin wire (>19years). This synergistic effect is not understood !
Test frequency
>0.5Hz
Faster frequencies tend to negate potential deleterious effect of environment. Loading frequency should allow for the proper interaction between material and environment to take place.
Technology Developments Priorities
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Predictive Technologies
• Improve analysis methodologies for riser response predictions – fatigue,
compression, lateral buckling
• Develop testing methodologies that capture “chain-reaction” synergistic effects to
establish component capacity:
◦ Steel wire corrosion and fatigue
◦ High strength tape wear, aging and fatigue
◦ Polymers aging to different exposures – not standardized yet. Join 17TR2 JIP.
• Develop methodologies that correlate annulus sampling history to wire corrosion
and polymer aging
New Design – Expansion of Application Envelope
• Increase water depth per IDxP - weight reduction, 2014 17B Annex H composites
• Material and layer-design improvements for corrosive environments (souring
reservoirs, Black Sea)
Remnant Life Assessments
• Improve inspection technologies on layer and component level
• Develop the Predictive Technologies mentioned above