Fatigue Design of the Atlantis Export SCRS

2007 ◽  
Author(s):  
Mike Vandenbossche ◽  
Will McDonald ◽  
Dingwu Xia ◽  
Craig Masson ◽  
Jie Fang ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Wave Climate ◽  
Fatigue Performance ◽  
Mardi Gras ◽  
Fatigue Design ◽  
Fatigue Damage Accumulation ◽  
Steel Catenary Risers ◽  
Sigsbee Escarpment ◽  
Girth Welds ◽  
First Time

The Atlantis semi-submersible platform is located in 7040 feet water depth in southern Green Canyon, in the Gulf of Mexico. It supports the Mardi Gras 24-inch oil and 16-inch gas export steel catenary risers (SCRs), the deepest and largest diameter SCRs in the world. Fatigue performance was one of the critical and challenging aspects of the design due to the severe wave climate coupled with the large vessel motions and strong bottom currents below the Sigsbee Escarpment. Preliminary design showed that the fatigue life at the girth welds in the touch down point (TDP) region did not satisfy the design criteria. This paper presents the fatigue design measures that were adopted to improve the fatigue performance of the Atlantis export SCRs. These include the first-time use of manually relocating the host platform to reduce fatigue damage accumulation in the TDP region, and removing the weld caps over the most critical part of the TDP region and grind flush the caps and roots of the welds in the flexible joint assembly to achieve practical defect acceptance criteria. It is demonstrated that the narrow fatigue damage peak in the TDP region can be decreased significantly by spreading it over a wider region, and all the design requirements are satisfied.

The Qualification and Continued Evolution of Reeled Steel Catenary Risers

2009 ◽  
Author(s):  
Fin Gray ◽  
Brett Howard ◽  
Alexandra Pieton ◽  
Ramon Gallart
Keyword(s):  
Full Scale ◽  
Fatigue Performance ◽  
Track Record ◽  
Mechanized Welding ◽  
Steel Catenary Risers ◽  
Weld Fatigue ◽  
Fit For Purpose ◽  
Girth Welds ◽  
The Impact ◽  
Welding Processes

Technip began qualification of reeled Steel Catenary Risers (SCR) back in 1997. Industry had raised concerns at that time over the plastic straining cycles that are intrinsic to the reel lay method and the impact these could have upon the service fatigue life of the girth welds. The qualification programme, therefore, included comparison of reeled welds against virgin welds for a suite of fatigue and mechanical testing including full scale fatigue and fatigue crack growth tests. Reeling was shown to have no discernable impact for the fatigue performance level sought when a controlled SCR fabrication process was adhered to. This provided sufficient confidence that the technology was fit for purpose and led to successful fabrication and installation of the first reeled SCR in 2001. Since then more than 25 have been installed in the Gulf of Mexico, with most projects including full scale weld fatigue test qualification following reeling simulations. This paper includes the following: (a) a summary of the philosophy adopted for qualification, fabrication and installation of a reeled SCR, (b) presentation of the reeled SCR track record and evolution of the technology to include mechanized welding processes (c) a look at ongoing developments targeting even higher fatigue performance, and (d) discussion on the development of fracture mechanics techniques that provide further confidence in the concept and can be used to derive appropriate weld acceptance criteria.

Strength and Fatigue Performance of Steel Lazy Wave Risers With Change in Configuration Parameters

2019 ◽  
Author(s):  
Mayank Lal ◽  
Feng Wang ◽  
Xiaohua Lu ◽  
Abhilash Sebastian
Keyword(s):  
Deep Water ◽  
Parametric Study ◽  
Fatigue Performance ◽  
Design Criteria ◽  
Cost Assessment ◽  
Fatigue Design ◽  
Design Variables ◽  
Steel Catenary Risers ◽  
Normative Cost ◽  
The Impact

Abstract Steel Lazy wave risers are being increasingly used for deep water applications due to better strength and fatigue performance in the touchdown zone compared to steel catenary risers. Several parameters govern the design of steel lazy wave risers including the length of the catenary from hang-off to start of buoyancy section and the length of the buoyancy section. In this paper, a parametric study is performed to investigate the trends in strength and fatigue performance of steel lazy wave risers with change in configuration parameters. A normative cost assessment is also performed to show the impact of these design variables on overall cost of the system. Dynamic analysis is performed to check the change in strength and fatigue performance of steel lazy wave risers as the configuration parameters are changed. The results from the parametric study will assist in designing steel lazy wave risers which satisfy the strength and fatigue design criteria.

Fatigue Performance of Grade R4 and R5 Mooring Chains in Seawater

2014 ◽  
Author(s):  
Jonathan Fernández ◽  
Walther Storesund ◽  
Jesús Navas
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Fatigue Tests ◽  
Design Methods ◽  
Full Scale ◽  
Fatigue Performance ◽  
Test Program ◽  
Gas Industry ◽  
Fatigue Design ◽  
Cumulative Fatigue Damage

With more than 50.000 tons in service to date, the Oil&Gas Industry has the need to understand the tension fatigue performance of grade R5 chains in straight tension, and corroborate the validity of the existing design methods. The chain fatigue design curves in API and DNV are based on fatigue tests obtained in the nineties and early two thousands. However the tests were performed on lower grades such as ORQ, R3 and R4, and small chains, 76 mm diameter being the largest studless chain tested. The industry has moved towards the use of large studless chains, especially in permanent units, where chain diameters above 150 mm are not unusual. This paper gathers information from a full scale fatigue test program on grade R4 and R5 studless chains, performed in seawater and with diameters between 70 mm and 171 mm. The chains being tested are actual production chains supplied for different drilling units and large permanently moored production floating units. The paper analyses the data and determines tension-tension fatigue curves based on API and DNV methods for computation of cumulative fatigue damage, regardless of other damaging mechanisms. Improved fatigue capacity is obtained with respect to the above recommended design methods.

Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Peter K. Fossum ◽  
Lars Frøyd ◽  
Ole G. Dahlhaug
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Turbine Blades ◽  
Fiber Material ◽  
Fatigue Performance ◽  
Wind Turbine Blades ◽  
Additional Material ◽  
Turbulent Wind ◽  
Fatigue Damage Accumulation ◽  
Utility Scale

Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades have been performed to investigate the applicability of different types of materials in a fatigue environment. The blade designs used in the study are developed according to an iterative numerical design process for realistic wind turbine blades, and the software tool FAST is used for advanced aero-servo-elastic simulations. Elementary beam theory is used to calculate strain time series from these simulations, and the material fatigue is evaluated using established methods. Following wind turbine design standards, the fatigue evaluation is based on a turbulent wind load case. Fatigue damage is estimated based on 100% availability and a site-specific annual wind distribution. Rainflow cycle counting and Miner's sum for cumulative damage prediction is used together with constant life diagrams tailored to actual material S-N data. Material properties are based on 95% survival probability, 95% confidence level, and additional material safety factors to maintain conservative results. Fatigue performance is first evaluated for a baseline blade design of the 10 MW NOWITECH reference wind turbine. Results show that blade damage is dominated by tensile stresses due to poorer tensile fatigue characteristics of the shell glass fiber material. The interaction between turbulent wind and gravitational fluctuations is demonstrated to greatly influence the damage. The need for relevant S-N data to reliably predict fatigue damage accumulation and to avoid nonconservative conclusions is demonstrated. State-of-art wind turbine blade trends are discussed and different design varieties of the baseline blade are analyzed in a parametric study focusing on fatigue performance and material costs. It is observed that higher performance material is more favorable in the spar-cap construction of large blades which are designed for lower wind speeds.

Fatigue Design and Analysis of Offshore Pipelines and Risers Subjected to Waves and Currents

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Coupling Effect ◽  
Limit State ◽  
Ultimate Limit State ◽  
Offshore Pipelines ◽  
Fatigue Design ◽  
Fatigue Damage Accumulation ◽  
Waves And Currents ◽  
Wave Induced

The industry consensus would appear that the effect of currents on wave-induced fatigue damage accumulation is assumed as insignificant and can be ignored. Only when dealing with stability, ultimate limit state design, and vortex-induced vibration (VIV), is the recommended industry practice to consider both currents and waves simultaneously, except for fatigue design. This paper presents a study on how environmental loads should be considered in terms of currents and waves for the fatigue life design of offshore pipelines and risers. The study is intended as a spur to redress the misapprehension by focusing on the coupling effect of direct waves and currents in the context of fatigue damage assessment. It is demonstrated unequivocally that waves and currents cannot be decoupled for fatigue design assessments. Wave-induced fatigue with the inclusion of currents is manifested twofold, not only the increased mean stress correction effect but also higher total damage accumulation due to elevated stress ranges. The practice of using wave histograms while ignoring currents is shown to result in an unacceptable nonconservative fatigue design. Both effects should be accounted for in the engineering assessment. A first-order correction factor involving the ratio of current and wave velocities is introduced to evaluating the environmental load coupling effect. It is recognized that fatigue associated specifically with VIV phenomena is well understood and documented elsewhere, its discussion is thus out with the aims of this paper.

An Investigation of the Fatigue Performance of Riser Girth Welds

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Stephen J. Maddox ◽  
Julian B. Speck ◽  
G. Reza Razmjoo
Keyword(s):  
Oil And Gas ◽  
Welding Process ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Steel Catenary Riser ◽  
Gas Recovery ◽  
Fatigue Design ◽  
Pipeline Welding ◽  
Girth Welds

Increasing deep-water oil and gas recovery has highlighted the need for high integrity, high fatigue performance girth welds in steel catenary riser systems. Such systems include girth welds made from one side. However, the widely used fatigue design classification, UK Class F2, for such welds is not well founded, but probably overconservative for pipeline welds. In an attempt to justify upgrading current fatigue design classifications and providing a better basis for design, fatigue tests were performed on a range of girth-welded pipes produced by pipeline welding contractors. This paper presents the results of those tests and their evaluation in terms of the factors that influence the fatigue performance of girth welds, including welding process, welding position, backing system, joint alignment, weld quality, specimen type, and fatigue loading conditions. Conclusions are drawn regarding the scope for adopting higher design classifications and the conditions that must be met to justify them.

High-Cycle and Low-Cycle Fatigue Resistance of Girth Welds in Sour Service

2008 ◽  
Author(s):  
Jaime Buitrago ◽  
Stephen Hudak ◽  
David Baxter
Keyword(s):  
Low Cycle Fatigue ◽  
Water Injection ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Production Lines ◽  
Hydrocarbon Production ◽  
Steel Catenary Riser ◽  
Fatigue Design ◽  
Girth Welds ◽  
Constant Slope

The fatigue performance of fracture-critical production lines, such as risers and flowlines, has been shown to significantly degrade in the presence of sour hydrocarbon production caused by water injection of reservoirs. To ensure the reliability of the fatigue design under such conditions, experimental verification of the degradation effect on fatigue life due the presence of H2S is required. To that end and over the past several years, ExxonMobil has developed new testing methodologies to evaluate the riser fatigue performance for both in-air and sour conditions. This paper reviews the general elements of the fatigue qualification process and presents new sour fatigue data aimed at assessing performance at the high-cycle fatigue (HCF) and low-cycle fatigue (LCF) regimes. These new data are relevant to that seen in steel catenary riser (SCR) and flowline thermal responses, respectively. Testing methodologies for each regime are discussed and results presented. The new data are interpreted within the context of previous data in the intermediate-cycle fatigue (ICF) to provide a more robust basis for riser design. The main finding is that the new data support a constant slope S-N curve for the practical domain of fatigue lives to which offshore lines are typically designed under sour conditions.

An Investigation of the Fatigue Performance of Riser Girth Welds

2006 ◽  
Author(s):  
Stephen J. Maddox ◽  
Julian B. Speck ◽  
G. Reza Razmjoo
Keyword(s):  
Oil And Gas ◽  
Welding Process ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Steel Catenary Riser ◽  
Gas Recovery ◽  
Fatigue Design ◽  
Pipeline Welding ◽  
Girth Welds

Increasing deep-water oil and gas recovery has highlighted the need for high integrity, high fatigue performance girth welds in steel catenary riser systems. Such systems include girth welds made from one side. However, the widely used fatigue design classification, UK Class F2, for such welds is not well founded, but probably over-conservative for pipeline welds. In an attempt to justify upgrading current fatigue design classifications and providing a better basis for design, fatigue tests were performed on a range of girth-welded pipes produced by pipeline welding contractors. This paper presents the results of those tests and their evaluation in terms of the factors that influence the fatigue performance of girth welds, including welding process, welding position, backing system, joint alignment, weld quality, specimen type and fatigue loading conditions. Conclusions are drawn regarding the scope for adopting higher design classifications and the conditions that must be met to justify them.

Fatigue Performance of Thick Section Titanium Grade 29 Girth Welds

2020 ◽  
Author(s):  
Gabriel Rombado ◽  
David A. Baker ◽  
Lars M. Haldorsen ◽  
Kenneth Macdonald ◽  
Heath Walker ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Fatigue Testing ◽  
Fatigue Performance ◽  
Fluid Temperature ◽  
Design Curve ◽  
Fatigue Design ◽  
Dog Bone ◽  
Titanium Grade ◽  
Girth Welds ◽  
Welding Procedure

Abstract Design of Steel Catenary Risers (SCRs) requires the use of specialized connection hardware to mitigate the high dynamic bending moments at the hang-off location induced by host floater motion. Reliability of this connection hardware is imperative, especially in those applications involving high tension loads, high pressure and elevated fluid temperature. One option for connection hardware is a monolithic, metallic tapered stress joint. Because of its inherent density, strength, and stiffness properties, steel is not well suited for these applications due to excessive stress joint length and weight requirements. Titanium Grade 29 has been identified as an attractive material candidate for demanding service applications due to its unique mechanical properties including increased flexibility, excellent fatigue performance and corrosion resistance to sour fluids. This technology is well established in the offshore industry and utilized in over 60 SCR installations with operating lives exceeding 20 years of continuous subsea operation. Large titanium stress joints (TSJs) for deep-water applications are typically not fabricated as a single piece due to titanium ingot volume limitations thus making one or more intermediate girth weld(s) necessary to satisfy the overall length requirements. Fatigue testing of 38 mm (1.5-in) wall thickness girth welds, utilizing an optimized GTAW welding procedure to limit defect sizes to sub-millimeter, has previously been performed in seawater (OD exposure) under cathodic protection potentials and sour service (ID exposure) under galvanic potentials. Fatigue testing results fully verified the vendor S-N fatigue design curve, in addition, no appreciable differences in fatigue performance in environments were observed allowing project-specific testing to be limited to in-air testing. This paper presents in-air fatigue testing results of 51 mm (2.0-in) wall thickness Grade 29 girth welds, using the same optimized welding procedure, to assess thickness size effect on the vendor S-N fatigue design curve. Verification of the vendor fatigue design curve was demonstrated by testing curved dog-bone specimens, extracted longitudinally across the girth weld, with production level surface finishes on inner and outer surfaces in-air up to a predefined S-N fatigue target curve with 95% confidence level.

Fatigue Design and Analysis of Offshore Pipelines and Risers Subjected to Waves and Currents

2016 ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Coupling Effect ◽  
Limit State ◽  
Ultimate Limit State ◽  
Offshore Pipelines ◽  
Fatigue Design ◽  
Fatigue Damage Accumulation ◽  
Waves And Currents ◽  
Wave Induced

The industry consensus would appear that the effect of currents on wave induced fatigue damage accumulation is assumed as insignificant and can be ignored. Only when dealing with stability, ultimate limit state design and vortex induced vibration, the recommended industry practice is to consider both currents and waves simultaneously, but except for fatigue design. This paper presents a study on how environmental loads should be considered in terms of currents and waves for the fatigue life design of offshore pipelines and risers. The study is intended as a spur to redress the misapprehension by focusing on the coupling effect of direct waves and currents in the context of fatigue damage assessment. It is demonstrated unequivocally that waves and currents cannot be decoupled for fatigue design assessments. Wave induced fatigue with the inclusion of currents is manifested twofold, not only the increased mean stress correction effect but also higher total damage accumulation due to elevated stress ranges. The practice of using wave histograms while ignoring currents is shown to result in an unacceptable non-conservative fatigue design. Both effects should be accounted for in the engineering assessment. A first order correction factor involving the ratio of current and wave velocities is introduced to evaluating the environmental load coupling effect. It is recognized that fatigue associated specifically with VIV phenomena is well understood and documented elsewhere, its discussion is thus outwith the aims of this paper.

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