Engineering Critical Assessment for the Flaws in the Pipeline Steel Girth Weld

2016 ◽  
Vol 850 ◽  
pp. 881-888
Author(s):  
Jiang Qiao Wu ◽  
Deng Zun Yao ◽  
Xin Ran Yuan ◽  
Tian Qi Wang ◽  
Long Zhang
Keyword(s):  
Pipeline Steel ◽  
Critical Assessment ◽  
Assessment Methods ◽  
Key Factors ◽  
Weld Repair ◽  
Defect Assessment ◽  
Welding Defects ◽  
Welding Defect ◽  
Girth Welds ◽  
Level 2

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructure. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes are used in this field, there are many differences among them. In this paper, the welding defect assessment methods, such as API 1104 and BS7910, were studied. The results show the key factors that affect the result of these assessment methods. The application of these methods was also discussed. The results indicate that API 1104 level1 has the highest conservatism, while API 1104 level 2 is next.

Application of State of the Art Assessment for Pipeline Girth Weld

2017 ◽  
Vol 898 ◽  
pp. 1063-1068
Author(s):  
Deng Zun Yao ◽  
Zhi Wen Li ◽  
Jian Wu Liu ◽  
Lin Chen
Keyword(s):  
State Of The Art ◽  
Axial Stress ◽  
Construction Cost ◽  
Assessment Methods ◽  
Weld Repair ◽  
Defect Assessment ◽  
Weld Defect ◽  
Key Points ◽  
Welding Defects ◽  
Girth Welds

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructural heterogeneities. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes have been applied in this field, there are many differences among them. In this paper, the application of weld defect assessment methods was extensively studied. The key points of ECA applications, such as the pipeline axial stress and toughness, have been introduced. Furthermore, some suggestions were given on the application of girth weld ECA assessment.

Preventing Girth Weld Failure in Pipelines: Measurement of Loads and Application of Assessment Methods

2020 ◽  
Author(s):  
Andy Young ◽  
Robert M. Andrews
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Large Diameter ◽  
Ground Movement ◽  
External Loading ◽  
Key Factors ◽  
Axial Loads ◽  
Contributing Factors ◽  
Increased Risk ◽  
Girth Welds

Abstract Pipeline failures from circumferential cracking at girth welds continues to affect large diameter oil and gas transmission lines, even for modern lines constructed this century. The key factors that contribute to the failure at girth welds are the dimensions of defects present, the material properties of the pipe and weldments, and the presence of loading that drives crack growth. The mechanisms of failure are well understood, but identifying and measuring the contributing factors can be a challenge. Locating girth welds that are subject to elevated loads will enable operators to focus on sections with an increased threat of failure. In this paper, we consider each of the key factors, how these are identified and defined, and the uncertainties in the measurement process. Specific attention is applied to the presence and quantification of loads and how these influence the potential for failure. This includes sources of active external loading due to ground movement, for example, or loads generated in the pipeline from the construction process. Loads can also be quantified by measuring bending strain from inline inspection inertial measurement units. A more complete picture of pipeline loading can be established by integrating a structural analysis that accounts for the direction of pipeline movement and the presence of axial loads. The relationship between assessing pipeline integrity from ground movement — typically with strainbased methods — and establishing whether the defect can survive the load is explored. The relative contribution of bending and axial loads in the failure of defects is considered. The outcome of the study will assist pipeline operators in prioritising actions that enable the quantification of the all the key parameters. The resultant analysis will provide guidance on the girth welds that have an increased risk of failure and this will enable protective actions to be defined and scheduled accordingly.

A Modified Engineering Critical Assessment Approach for Offshore Pipelines

2018 ◽  
Author(s):  
Colum Holtam ◽  
Rajil Saraswat ◽  
Ramgopal Thodla ◽  
Feng Gui
Keyword(s):  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Loading ◽  
Critical Assessment ◽  
Offshore Pipelines ◽  
Static Crack ◽  
Production Environments ◽  
Assessment Approach ◽  
Girth Welds ◽  
Crack Growth Rates

Environmentally assisted sub-critical static crack growth can occur in offshore pipelines exposed to aggressive production environments. Recent advances in fracture mechanics testing methods have shown that slow static crack growth rates can be reliably measured in sweet and sour environments under constant stress intensity factor (K) conditions. This has potential implications for the engineering critical assessment (ECA) of pipe girth welds subject to low cycle fatigue loading with long periods of operation under constant static load between cycles, e.g. lateral buckling. This paper demonstrates the influence of including static (i.e. time dependent) crack growth as well as fatigue crack growth in a modified pipeline ECA approach.

Study on Methodology and Application of Seismic-Induced Flood Level 2 PSA for PWR in China

2020 ◽  
Author(s):  
Liu Yu ◽  
Li Wenjing ◽  
Yu Yun
Keyword(s):  
Severe Accident ◽  
Key Factors ◽  
Fukushima Accident ◽  
Core Damage ◽  
Design Basis ◽  
Flood Level ◽  
Crucial Problem ◽  
External Events ◽  
Flood Characteristics ◽  
Level 2

Abstract Level 2 (L2) PSA is focused on the severe accident phenomenon, progression and source terms release to generally evaluate the containment response after core damage takes place. Fukushima accident was caused by seismic and tsunami which are beyond design basis. It indicates that evaluating the risk for extremely external hazards is vitally important. Therefore, how to perform the study on L2 PSA for external events (especially seismic and flood) has become a crucial problem needed to be considered deeply for both regulators and operators. In this paper, the methodology of flood and seismic-induced flood L2 PSA was developed and applied for a Gen III NPP in China. The key factors include: (1) Focusing on crucial elements of L2 PSA in view of seismic and flood characteristics, including PSA interfaces, design features, severe accident phenomenon and progression, containment performance analysis, etc. (2) Building integrated internal flood and seismic L2 PSA models. (3) Developing an analytical method to evaluate seismic-induced flood L2 PSA.

Pressure Correction Factor for Strain Capacity Predictions Based on Curved Wide Plate Testing

2012 ◽  
Author(s):  
Matthias Verstraete ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Stijn Hertelé
Keyword(s):  
Correction Factor ◽  
Large Scale ◽  
Strain Capacity ◽  
Defect Assessment ◽  
Ductile Crack Growth ◽  
Large Scale Testing ◽  
Weld Defect ◽  
Girth Welds ◽  
Assessment Procedures ◽  
Tensile Strain Capacity

Strain-based girth weld defect assessment procedures are essentially based on large scale testing. Ever since the 1980’s curved wide plate testing has been widely applied to determine the tensile strain capacity of flawed girth welds. However, the effect of internal pressure is not captured in curved wide plate testing. Accordingly, unconservative predictions of strain capacity occur when straightforwardly transferred to pressurized pipes. To address this anomaly, this paper presents results of finite element simulations incorporating ductile crack growth. Simulations on homogeneous and girth welded specimens indicate that a correction factor of 0.5 allows to conservatively predict the strain capacity of a pressurized pipe through wide plate testing under the considered conditions.

scholarly journals The Effect of Microstructural Change on Fracture Behavior in Heat-Affected Zone of API 5L X65 Pipeline Steel

2000 ◽  
Author(s):  
Jang-Bog Ju ◽  
Jae-il Jang ◽  
Woo-sik Kim ◽  
Dongil Kwon
Keyword(s):  
Fracture Behavior ◽  
Impact Test ◽  
Pipeline Steel ◽  
Microstructural Change ◽  
Fracture Characteristics ◽  
Welded Structures ◽  
The World ◽  
Natural Gas Transmission ◽  
Macroscopic Fracture ◽  
Girth Welds

Reliability evaluation of welded structures by mechanical testing of weld heat-affected zones (HAZs) has become general practice throughout the world. HAZs of steel welded joints show a gradient of microstructure from the fusion line to the unaffected base metal. This study is concerned with a correlation between the microstructural change and the fracture characteristics in HAZs of both seam and girth welds of API 5L X65 pipeline steel, which is generally used for natural gas transmission pipelines in Korea. The focus in present study was the investigation of macroscopic fracture behavior of the various regions within HAZ. Changes in microstructure and impact toughness were observed using synthetic HAZ specimens as well as actual HAZ specimens. To evaluate the macroscopic toughness of actual HAZ, Charpy V-notch impact test was performed.

The Weldability of Primer-Coated Steel for Shipbuilding by CO2 Laser

2006 ◽  
Vol 321-323 ◽  
pp. 1745-1749 ◽  
Author(s):  
Jong Do Kim ◽  
Jin Seok Oh ◽  
Hyun Joon Park
Keyword(s):  
Welding Parameters ◽  
Coated Steel ◽  
Zinc Vapor ◽  
Welding Technology ◽  
Weld Material ◽  
Welding Defects ◽  
Lap Welding ◽  
Welding Defect ◽  
Alternative Idea

The application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer-coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6 t primer coated steels by a CO2 CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position were lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controlling the factors.

scholarly journals Estimation of the Time of Flight of an Electric Unmanned Helicopter Based on the Minimum Set of Parameters

2019 ◽  
pp. 67-72
Author(s):  
S.Z. Sverdlov
Keyword(s):  
Specific Energy ◽  
Specific Capacity ◽  
Time Of Flight ◽  
Assessment Methods ◽  
Theoretical Studies ◽  
Unmanned Helicopter ◽  
Key Factors ◽  
Factors Influencing

This article deals with the problem of forecasting the time of flight of an electric unmanned helicopter utilizing the minimum set of known parameters: the diameter and number of rotors and the flight mass. By solving this problem, it is possible to estimate the capabilities of an unmanned helicopter (multicopter), without having its full technical characteristics, which are often unavailable. In addition, when starting to design an aircraft, it is important to assess its key parameters necessary to achieve a given duration of flight, while preferably utilizing the minimum set of such parameters. Assessment methods are developed based on the statistics of the specific capacity of the batteries used for the construction of the aircraft class in question, and the analysis of the specific energy per weight, which is based both on theoretical studies and the consideration of known analogues. The obtained formulas clearly express the dependence of the time of flight on the key factors influencing it. Estimation of the time of flight using the proposed methods, may be the first step in designing a multicopter.

Atlantis Oil Export SCR: Treatment of Girth Welds for Enhanced Fatigue Performance

2007 ◽  
Author(s):  
Jim Brooks ◽  
Craig Masson ◽  
David Reeves
Keyword(s):  
Water Depth ◽  
Critical Assessment ◽  
Successful Implementation ◽  
Acceptance Criteria ◽  
Mardi Gras ◽  
Steel Catenary Riser ◽  
Severe Fatigue ◽  
Oil Export ◽  
Girth Welds ◽  
Critical Portion

Suspended from the Atlantis Production Quarters Semi-submersible in over 7000 ft water depth, the 24-inch diameter Mardi Gras Oil Export Steel Catenary Riser (SCR) presented many challenges for design and installation. In particular the touchdown region of the riser was subject to severe fatigue and extreme loadings. The Engineering Critical Assessment (ECA) at the weld OD generated defect acceptance criteria that would be impractical to apply with the available inspection technology. To mitigate this, the decision was made to remove the weld caps in the most critical portion of the SCR. This paper describes the design drivers that led to this decision and the steps taken to ensure successful implementation.

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