Integrity Assessment and Repair Techniques of Flexible Risers

2006 ◽  
Author(s):  
Mauro G. Marinho ◽  
Joilson M. dos Santos ◽  
Ricardo de O. Carneval
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Production Systems ◽  
Injection Pressure ◽  
Gas Transfer ◽  
Flow Measurements ◽  
Integrity Assessment ◽  
Flexible Pipes ◽  
Periodic Inspections ◽  
Repair Techniques

Deep water oil and gas exploitation in Brazil remarkably increased the utilization of flexible pipes in conjunction with floating production systems. In Campos Basin nowadays oil and gas transfer, water and gas injection and well control and monitoring are carried out almost entirely by flexible pipes, including risers, flowlines and umbilicals. Periodic inspections have detected a considerable incidence of damage in the top section of risers, which may affect their structural integrity and eventually induce different failure mechanisms. These include mostly external sheath damage, corrosion and/or fatigue-induced damage to the tensile armours and torsional instability. These damages are generally originated during installation or, more frequently, during operation due to contact with another riser or the platform structure. In order to mitigate the progression of these damages, besides periodic inspections, repair techniques were developed for both emerged and submerged riser sections. Apart from the inspection program, surface monitoring procedures, such as nitrogen injection, pressure monitoring and flow measurements in the annular space are being implemented, for a continuous flexible riser integrity assessment. This paper describes and evaluates these techniques, as well as reports the results obtained from field experience.

Investigation of Strain-Based Failure Assessment Based on Reference Strain Method for Welded Pipes

2019 ◽  
Author(s):  
Jae Sung Lee ◽  
Myung Hyun Kim
Keyword(s):  
Reference Strain ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Effective Means ◽  
Equivalent Stress ◽  
Strain Curve ◽  
Evaluation Procedure ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Strain Method

Abstract Pipelines are effective means to transport oil and gas. It is essential to maintain the safety of pipelines with the increasing demand for oil and gas resource. Welded pipelines may suffer damage such as cracks during installation and operation, and the consequence evaluation for such damage is very important. Engineering critical assessment (ECA) is the evaluation procedure for structures with flaws and has been widely applied for assessing the pipeline integrity. Although main standards of structural integrity assessment including BS 7910 are stress-based ECA, it is known to produce overly conservative results. In this regard, strain-based ECA has been recently developed. One of the methods for improving the accuracy of strain-based ECA is the reference strain method. However, only few researches with reference strain method applied to welded pipes are available. Therefore, in this study, a numerical analysis based on the strain-based ECA is performed for strength mismatched girth welded joints with a circumferentially oriented internal surface crack. Equivalent stress-strain curve in BS7910 is employed to reflect the strength mismatch effects in the reference strain. This paper compares the results from the reference strain method and finite element analysis: J-integral and reference strain. Strain capacity of the reference strain method with strength mismatch is also discussed against stress-based ECA.

Development and Experimental Calibration of Numerical Model Based on Beam Theory to Estimate the Collapse Pressure of Flexible Pipes

2015 ◽  
Author(s):  
Jefferson Lacerda ◽  
Marcelo I. Lourenço ◽  
Theodoro A. Netto
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Numerical Models ◽  
Beam Theory ◽  
Gas Production ◽  
Operating Conditions ◽  
Flexible Pipe ◽  
Experimental Calibration ◽  
Collapse Pressure ◽  
Flexible Pipes

The constant advance of offshore oil and gas production in deeper waters worldwide led to increasing operational loads on flexible pipes, making mechanical failures more susceptible. Therefore, it is important to develop more reliable numerical tools used in the design phase or during the lifetime to ensure the structural integrity of flexible pipes under specific operating conditions. This paper presents a methodology to develop simple finite element models capable of reproducing the behavior of structural layers of flexible pipes under external hydrostatic pressure up to collapse. These models use beam elements and, in multi-layer analyses, include nonlinear contact between layers. Because of the material anisotropy induced by the manufacturing process, an alternative method was carried out to estimate the average stress-strain curves of the metallic layers used in the numerical simulations. The simulations are performed for two different configurations: one where the flexible pipe is composed only of the interlocked armor, and another considering interlocked armor and pressure armor. The adequacy of the numerical models is finally evaluated in light of experimental tests on flexible pipes with nominal internal diameters of 4 and 6 in.

Structural Strength Assessment of Dented Steel Tubular Members

2021 ◽  
Author(s):  
S. Saad-Eldeen ◽  
Mahmoud Helal ◽  
Elsayed Fathallah
Keyword(s):  
Residual Strength ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Strength Assessment ◽  
Operational Conditions ◽  
Integrity Assessment ◽  
Modes Of Failure ◽  
Ultimate Load Carrying Capacity

Abstract Tubular members are widely used in oil and gas offshore production and drilling structures either fixed or mobile units. Due to complex operational conditions, the tubular members are subjected to both age and mechanical related damage, which in turn affect the ability of the structure to withstand the applied loads. This motivates the importance of investigating the behavior of tubular members considering the presence of dentation resulting from collision or falling objects and consequently assessing the residual strength of the damaged members accurately. A series of finite element analysis are performed to study the pre- and post-ultimate strength behavior of intact and locally dented un-stiffened steel tubular members subjected to four-point bending. The effects of dent geometrical parameters; length, width, depth, orientation, and location on the ultimate load carrying capacity are analyzed. The ratio between the diameters to the shell thickness is varied, where combined local and global initial imperfections are considered. Buckling and post collapse analysis as well as modes of failure are studied. Parametric diagrams for the ultimate residual strength as a function of dent geometry and the location of damage are also presented. Several concluding remarks are stated which benefit the structural integrity assessment of tubular steel members.

Repair Techniques for Flexible Pipe External Sheath

2008 ◽  
Author(s):  
T. A. Netto ◽  
J. M. Touc¸a ◽  
M. Ferreira ◽  
V. Gonc¸alez ◽  
R. Marnet
Keyword(s):  
Sea Level ◽  
Structural Integrity ◽  
Annular Region ◽  
Annular Space ◽  
Flexible Pipe ◽  
Flexible Pipes ◽  
Cutting Out ◽  
Inspection Techniques ◽  
Repair Techniques

During installation or service, the external sheath of flexible pipes can suffer damages that may result in loss of sealing and exposure of the annular region to the external environment. Additionally, visual inspection of the armor layers is sometimes necessary to assess their structural integrity. Such procedure requires cutting out a small segment (window) of the external sheath. One of the most effective inspection techniques to detect problems in the topside relief valves, damages on the external sheath, or pressure barrier failure is the surface monitoring of the pressure in the annular region. Therefore, in the event of sheath damage or inspection windows, in situ repair techniques that guarantee the recovery of its sealing properties are important, particularly in the regions above sea level and water depths usually up to 30 meters. When the pipes are below this level, repairs are in general done on board of an installation vessel. Due to the inherent complexities of each region, specific repair techniques have been developed by PETROBRAS to date. Nevertheless, these techniques do not guarantee the annular space sealing, therefore hampering pressure monitoring. The objective of this work was to develop an external sheath repair technique using light, resistant, and easy-to-install materials for the areas above sea level and small depths (up to 30 m) capable to provide the necessary sealing for annular space monitoring.

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.

scholarly journals Integrity of Subsea Control Umbilical

2014 ◽  
Author(s):  
Ramin Yasseri ◽  
Sirous Yasseri ◽  
Bin Wang
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Production Systems ◽  
Global Analysis ◽  
Gas Production ◽  
Fibre Optics ◽  
Oil And Gas Production ◽  
Internal Forces ◽  
3D Finite Element Method ◽  
Constituent Elements

Controlling subsea oil and gas production systems requires fibre optics, power cables and tubes for the transportation of chemical for injection and fluid for hydraulic controls. These are arranged in helical bundles in successive layers. Shaped thermoplastic fillers are used to separate components and to fill out voids in the cross section. If necessary, armour is added to provide strength for the dynamic loads. This paper describes the application of 3D finite element method to assess the structural Integrity of subsea umbilicals, including the interaction between the constituent elements. It is suggested to uses a global analysis to determine the internal forces and local analyses (sub-modelling) for detailed stress evaluation. Abaqus is used for this purpose, due to its capability with large size problems under severe discontinuities due contact conditions. This paper also discusses the umbilicals interaction with seabed. The focus of this paper is on the fatigue life calculation.

scholarly journals Guest Editorial: Recent Advances in Design and Structural Integrity of Pressure Vessels, Piping and Components

2021 ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Naoya Tada
Keyword(s):  
Guest Editorial ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Pressure Vessels ◽  
Special Issue ◽  
New Techniques ◽  
Research Results ◽  
Integrity Assessment ◽  
Recent Advances

Abstract The design and structural integrity evaluation of pressure retaining equipment are crucial elements in the nuclear, oil and gas industries. Accordingly, many research has been done to improve the accuracy of design and structural integrity assessment methodologies and to develop new techniques and procedures. In this special issue, it is intended to introduce the latest research results on these subjects. The papers in this issue were collected from two groups.

Accuracy of the Double-Clip on Gauge Method for Evaluating CTOD of SE(T) Specimens

2014 ◽  
Author(s):  
Zijian Yan ◽  
Yifan Huang ◽  
Wenxing Zhou
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Specimen Thickness ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Crack Tip Opening ◽  
Edge Tension

The crack tip opening displacement (CTOD)-based fracture toughness has been widely used for structural integrity assessment and strain-based design of oil and gas pipelines. The double-clip on gauge method has been used to experimentally determine CTOD. In this study, three-dimensional (3D) finite element analyses of clamped single-edge tension (SE(T)) specimens are carried out to investigate the accuracy of the CTOD evaluation equation associated with the double-clip on gauge method. The analysis considers SE(T) specimens with ranges of crack lengths (0.3 ≤ a/W ≤ 0.7) and specimen thickness (B/W = 0.5, 1 and 2). Based on the analysis results, a modified CTOD evaluation equation based on the double-clip on gauge method is developed to improve the accuracy of the CTOD evaluation. This study will facilitate the application of the fracture toughness determined from the SE(T) specimen in the strain-based design of pipelines.

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.

Structural Integrity Assessment of Maritime Transport Equipment

2018 ◽  
Author(s):  
Xiaoli Jiang
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
New Technology ◽  
Maritime Industry ◽  
Transport Equipment ◽  
Integrity Assessment ◽  
Damage Prognosis ◽  
Potential Development ◽  
Future Challenges ◽  
New Material

Structural integrity assessment is the study of the safe design and assessment of components and structures under loads, and has become increasingly important in engineering design. The technology and applications of structural integrity widely range from transportation, oil and gas, power generation to petrochemical, nuclear sectors, etc. In this paper, the character of structural integrity assessment in the maritime field is discussed, the latest approach and techniques are classified in three sub-topics, damage diagnosis, damage prognosis & maintenance strategy and then illustrated using a few practical studies. Finally, the future challenges introduced by new material, new exploitation field and new technology, i.e., IOT, big data, etc., are discussed and the potential development of structural integrity assessment in maritime industry is explored.

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