ECA of Pipeline With Girth Weld Strength Mis-Matching Subjected to Large Strain

2009 ◽  
Author(s):  
Zhengmao Yang ◽  
Shashi Kumar ◽  
Jens P. Tronskar
Keyword(s):  
Base Metal ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Weld Strength ◽  
Assessment Procedure ◽  
Long Distance ◽  
Acceptance Criteria ◽  
Gas Field

In recent years, the strain based design for pipeline has been widely accepted by the industry, but the definition of a rational flaw acceptance criteria for girth welds subjected to axial strain within the context of the existing codified fracture mechanics based assessment procedures is problematic since these are essentially stress based. To extend the FAD method to the large strain conditions, several challenges i.e. weld strength mismatching, fracture toughness, and welding residual stresses have to be understood. With appropriate modifications as per DNV-RP-F108 [1], the assessments procedure detailed in BS7910 document for stress based situations have been used successfully for several projects to develop acceptance criteria for pipeline installation involving plastic straining. But only weld metal strength over-match comparing with base metal is considered in DNV-RP-F108 [1]. High strength line pipes are required to reduce the transmission cost of natural gas in long distance and internal clad with corrosion resistant alloy (CRA) is used for transportation of sour gas. Steel manufactures have developed such line pipes to develop new oil and gas field. The inconel filler metal was selected as weld consumable for the production girth weld in the lay budge. From the all weld tensile tests, it was found that the yield strength of the weld is under-match comparing the base metal, and the pipeline maybe subjected to a strain level up to 1.0% due to the lateral buckling. In this research the effect of weld strength mismatching on the structural integrity of the pipeline subjected to large strain was studied. The Engineering Critical Assessment (ECA) was performed to derive the critical flaw acceptance criteria for the AUT system. The segment tests and numerical analysis were performed to validate the assessment procedure, and the finite element analyses of the pipeline girth weld with surface crack in the weld centre were carried out to investigate the effect of bi-axial loading on the ECA results.

Fracture Toughness Testing and Validation of Pipeline Girth Weld Flaw Acceptance Criteria for Sour Service Under Large Strain

2011 ◽  
Author(s):  
You You Wu ◽  
Wen Guo Yuan ◽  
Tse Ven Steven Chong ◽  
Jens P. Tronskar
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Laboratory Data ◽  
Local Buckling ◽  
Acceptance Criteria ◽  
Service Environment ◽  
Girth Welds ◽  
Sour Service

Fracture toughness is one of the most important input parameters for assessment of pipeline girth weld failure capacity. For many new subsea pipeline projects there is a need to develop flaw acceptance criteria for pipeline installation considering the operation phase which may involve the transport of sour oil and gas and where the pipeline is exposed to large axial strain due to local buckling. Engineering Critical Assessment (ECA) performed using laboratory data based on conservative KISSC testing gives small acceptable flaw sizes which may be below the workmanship criteria for pipeline laying. DNV has conducted extensive research based on the requirements of DNV-OS-F101 and DNV-RP-F108, aiming to establish a method to develop J-R curves applicable for ECA of pipeline girth welds in sour service environment and a methodology to validate the ECA by segment testing in a laboratory-simulated sour service environment as per DNV-RP-F108.

Early Engagement of ECA in Offshore Deepwater Pipeline Design

2021 ◽  
Author(s):  
Daowu Zhou ◽  
Lingjun Cao ◽  
T. Sriskandarajah ◽  
Mark Lewis ◽  
Daniel Manso
Keyword(s):  
Oil And Gas ◽  
Fluid Composition ◽  
Acceptance Criteria ◽  
Gas Field ◽  
Detailed Design ◽  
Damage And Fracture ◽  
Weld Material ◽  
Challenging Environment ◽  
Oil And Gas Field ◽  
Pipeline Design

Abstract Welding acceptance criteria derived through ECA is typically performed after the detailed design. The design loads, together with pipeline and girth weld material testing data, are inputs to ECA and used to evaluate the pipeline girth weld integrity for determining the criticality of potential weld flaws. With ever increasing challenging environment (deepwater, HP/HT, aggressive fluid composition etc) in the oil and gas field, the fatigue damage and fracture failure may become a serious concern, consequently limiting the productivity of the pipeline fabrication. It is therefore essential to integrate ECA into the design loop to remove the uncertainty and risk to achieve a practically workable fabrication solution. In this paper, a strategy to integrate early ECA into pipeline detailed design phase is presented. A case study in a deepwater subsea channel crossing demonstrates that an early ECA engagement effectively mitigates the significant fatigue and fracture risk and obtains workable welding acceptance criteria for fabrication.

Assessment of Offshore Platforms Under Subsidence—Part I: Approach

2000 ◽  
Vol 122 (4) ◽  
pp. 260-266 ◽  
Author(s):  
Joseph M. Gebara ◽  
Dan Dolan ◽  
Stuart Pawsey ◽  
Philippe Jeanjean ◽  
Knut Dahl-Stamnes
Keyword(s):  
Structural Integrity ◽  
Soil Mechanics ◽  
Strength Analysis ◽  
Assessment Procedure ◽  
Offshore Platforms ◽  
Acceptance Criteria ◽  
Reliability Modeling ◽  
Systematic Assessment ◽  
International Conference ◽  
Increased Risk

This is the first of four companion papers that present a comprehensive assessment of the effect of sea floor subsidence on the Valhall complex of platforms. The study has included an estimate of the increase in platform failure probability as a function of increased subsidence. Subsidence raises the effective mean still water level and increases the potential for inundation of the deck for extreme storm conditions. Deck wave slam forces generate significantly greater platform loading and lead to: (a) higher levels of structural inelastic response and increased risk of structural failure as well as (b) water reaching the cellar deck, and hence affecting operators as well as equipment. The paper focuses on addressing the first of these two issues. A structural assessment study was performed to address the significance of present and future levels of subsidence on the safety of three North Sea platforms. The study included a systematic assessment procedure that addressed each of the factors that impacted structural integrity issues and reliability concerns. Such factors included: ultimate strength analysis methodologies, tubular joint formulations, group pile effects, and soil-structure interaction, which are described in this paper, as well as deck impact force formulations (Pawsey et al., 1998, “Characterization of Environmental Loads on Subsiding Offshore Platforms,” 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July) component and system reliability modeling (Jha et al., 2000, “Assessment of Offshore Platforms Under Subsidence—Part II: Analysis and Results,” ASME J. Offshore Mech. Arct. Eng., 122, pp. 267–273), and acceptance criteria (Stahl et al., 1998, “Acceptance Criteria for Offshore Platforms,” 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July). This paper presents the assessment procedure, as well as the modeling approach. The paper also discusses the consequence classification of the three platforms and state-of-the-art soil mechanics techniques that lead to a significant increase in the tensile capacity of the foundation. [S0892-7219(00)00204-1]

An Analytical Approach for Strain Analysis of Buried Steel Pipeline in Mining Subsidence Areas

2017 ◽  
Author(s):  
Mengying Xia ◽  
Hong Zhang
Keyword(s):  
Oil And Gas ◽  
Axial Strain ◽  
Compressive Strain ◽  
Reduction Factor ◽  
Mining Subsidence ◽  
Operating Pressure ◽  
Long Distance ◽  
Complex Load ◽  
Steel Pipeline ◽  
Subsidence Area

Mining subsidence is one of the typical geological hazard threats for long distance oil and gas pipeline. Pipelines in subsidence areas will encounter complex load conditions, which probably will lead to rupture or local buckling failure. An analytical strain calculation model for steel pipeline in mining subsidence areas was proposed. Accuracy of the model was validated by comparing with the finite element results. Based on the proposed model, parametric study was conducted to investigate the influences of main effect factors on the pipe strain. Results show that, the maximum compressive strain occurs in the middle of the subsidence area, and the maximum tensile strain occurs on the edge of the subsidence area. Axial strain of the pipeline in the subsidence area increases with the increase of overlying strata stiffness, strike length and mining depth. But the mining thickness has a negligible effect on the axial strain. The increase of operating pressure, buried depth and pipe-soil interaction reduction factor will increase the axial strain, while a larger pipe wall thickness will induce a smaller axial strain.

Fracture Assessment of the High Strength Super-Martensitic Stainless Steel Welds by SINTAP Defect Assessment Procedure

2003 ◽  
Author(s):  
A. K. Motarjemi ◽  
M. Koc¸ak ◽  
R. Segar ◽  
S. Riekehr
Keyword(s):  
Stainless Steel ◽  
Carrying Capacity ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Welding Process ◽  
Assessment Procedure ◽  
Load Carrying Capacity ◽  
Deformation And Failure ◽  
Integrity Assessment ◽  
Load Carrying

13% Cr supermartensitic stainless steel is an adequate substitute material for the conventional carbon and duplex stainless steel pipes for mild corrosive environments in the oil and gas industries. By development of these new steel and respective welding technologies, structural integrity analysis of the welded pipes, is essential and a challenging task. Depending on the welding process, filler wire used, the deformation and failure behaviours of the welded pipes could be different. In this study, fitness for service analysis verified with Submerged Arc welded Middle Tension, M(T), plates as well as for the reeling deformation during the pipe-laying process. This was done by applying analysis Levels 0, I, II and III of a recently developed European Structural Integrity Assessment Procedure (SINTAP). The goal was first of all to verify SINTAP’s load-carrying capacity predictions for welded M(T) specimens (wide plates) by comparing them with corresponding experimental data. SINTAP was also used for estimating the maximum tolerable crack size within the base or weld regions under about 2.7% applied strain, which is the strain equal to the reeling process. The estimated load-carrying capacity of the plates were found on the safe side with acceptable conservatism for all the SINTAP analysis Levels.

Integrity Assessment, Repair and Verification of Fitness for Service of a Damaged Offshore Platform Radio Tower

2011 ◽  
Author(s):  
Abe Nezamian ◽  
Robert J. Nicolson
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Integrated Approach ◽  
Offshore Structures ◽  
Thickness Measurement ◽  
Initial Assessment ◽  
Structural Members ◽  
Minimum Thickness ◽  
Acceptance Criteria ◽  
Integrity Assessment

The maintenance of structural integrity is a significant consideration in the safety management of offshore installations. This paper presents an integrated approach for fitness-for-service evaluation of a deteriorating offshore radio tower structure. The approach is intended to assist engineers in assessing the overall fitness and survivability of aged offshore structures. A 43 m tall radio tower on an oil and gas platform located offshore Australia was reported with areas of heavy and medium corrosion of structural members. Severe corrosion in one leg of the radio tower had caused an obvious hole (extensive damage) through the leg at approximately 36m above the main deck and raised structural integrity concerns with the tower. The platform had been shut down due to concerns of a possible collapse of the tower. An assessment/repair program was developed to assure the short term integrity of the tower with minimal repair works. The integrity of the critically damaged leg had been temporarily restored using a clamped sleeve repair to allow progress with the inspection / thickness measurement of the corroded areas of the tower. As part of the fitness-for-service assessment, the minimum thickness acceptance criteria for the suspected corroded structural members were developed to enable initial assessment of the measured remaining wall thicknesses of the corroded member. Fitness for service integrity assessment requirements were developed to assess the locations that did not meet the minimum thickness criteria. The integrity requirements were adopted based on the average measured wall thickness, sensitivity structural analyses for reduced wind speeds for shorter life spans, and stability/survival assessment of the tower. An inspection program was carried out for the suspected locations and any additional locations identified during the inspection process. The inspection measurements were assessed against the fitness-for-service criteria. Where the measurements indicated that members did not meet the acceptance criteria temporary repairs were specified. Consequently, the tower fitness-for-service was found sustainable for up to 12 months until a more permanent repair or replacement of the tower could be completed, thus enabling the platform to resume normal operations.

Pipeline Girth Weld Inspection and Flaw Acceptance Criteria for Sour Service Applications

2017 ◽  
Author(s):  
Shashi Bhushan Kumar ◽  
Kapil Mohan ◽  
Shaodong Zhang ◽  
Jens P. Tronskar
Keyword(s):  
Best Practice ◽  
Oil And Gas ◽  
Probability Of Detection ◽  
Resistance Testing ◽  
Acceptance Criteria ◽  
Gas Field ◽  
Radiographic Inspection ◽  
Weld Inspection ◽  
Girth Welds ◽  
Sour Service

To establish flaw acceptance criteria for carbon steel pipeline girth welds that are intended to transport sour crude, wet sour gas and condensate it is important to assess the effect of operating environment and strain levels by performing the fracture toughness/ resistance testing as per DNV-OS-F101: 2013 in a representative simulated service environment or under more severe test conditions. None the less many oil and gas field operators still believe that using workmanship criteria and radiographic inspection will be adequate to ensure a safe future operation of the pipeline meeting the design life requirements under sour or severely sour operating environments. Unfortunately, experience shows that this is a dangerous practice as radiography tends to miss out in detecting the most severe planar defects such a lack of fusion, hydrogen induced cracking and weld root centerline cracks, this is specifically so for narrow J-bevel welds. Hence, DNV GL based on experience from many projects advocates inspection of all sour service pipelines using inspection methods such as AUT with a high probability of detection for planar flaws. Further, the AUT acceptance criteria shall be chosen appropriately with due considerations as workmanship type of acceptance criteria without proper verification may result in non-conservatism in the pipeline girth weld inspection and weld sentencing. This present paper presents some recent project experiences from typical sour service subsea pipeline projects and provide advices representing what is considered current best practice for testing and qualification of AUT systems for sour service projects.

The Effect of Oil and Gas Production and Construction on Soil Erosion and its Prevention Measures

2013 ◽  
Vol 869-870 ◽  
pp. 644-647 ◽  
Author(s):  
Jia Shan Wang ◽  
Ting Wang ◽  
Rui Hua Wang
Keyword(s):  
Soil Erosion ◽  
Surface Engineering ◽  
Oil And Gas ◽  
Good Control ◽  
Gas Production ◽  
Prevention Measures ◽  
Control Effect ◽  
Oil And Gas Development ◽  
Long Distance ◽  
Gas Field

Through researching the oil and gas in many companies, such as the Daqing Oilfield, Changqing Oilfield and the West-East Gas Pipeline Company and so on, we found that the production and construction of oil and gas at different stages influence the soil erosion vary greatly, including the exploration in oil and gas has a little effect on soil erosion, but oil and gas field surface engineering and pipeline construction impact on soil erosion greatly, and limited impact on soil erosion in oil and gas development, and long-distance pipeline operators had no effect on soil erosion.Oil and gas companies have taken appropriate preventive measures in the soil erosion and have achieved good control effect.

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