Girth Weld ECA From the Perspective of Code Revisions in North America

2002 ◽  
Author(s):  
Yong-Yi Wang ◽  
Jim F. Swatzel ◽  
David Horsley ◽  
Alan Glover
Keyword(s):  
North America ◽  
Fracture Criterion ◽  
Safety Margin ◽  
Cost Savings ◽  
Step Function ◽  
Weld Strength ◽  
Plastic Collapse ◽  
Defect Assessment ◽  
Girth Welds ◽  
Continuous Relation

In North America there are two primary girth weld ECA (Engineering Critical Assessment) codes: API 1104 Appendix A and CSA Z662 Appendix K. Both codes were developed in the early-to mid-1980’s and thus represent the technology of that time. Significant progress has been made since then in understanding the structural behavior of girth welds containing welding defects. This paper describes an effort funded by the PRCI (Pipeline Research Council International) to establish the technical basis for the revisions of these codes using the knowledge generated since the inception of the codes. The CSA Z662 Appendix K sets defect tolerance using separate fracture and plastic collapse criteria, while API 1104 Appendix A has only a fracture criterion. The worldwide trend in defect assessment is moving towards FAD (Failure Assessment Diagram) based approach, by which both fracture and plastic collapse can be assessed in one consistent format. An FAD-based ECA procedure specifically tailored to girth welds has been developed in a separate PRCI-funded project. This procedure incorporates refined fracture and plastic collapse solutions and the effects of weld strength mismatch. The experimental verification has shown that the procedure is accurate and can become the basis for future code revisions. As an interim step towards the eventual adoption of a fully FAD-based approach, a number of revisions may be made to the API 1104 Appendix A, including (1) adding a plastic collapse criterion; (2) lowering the minimum CTOD requirement of using Appendix A to 0.003 inch (0.076 mm) from the current minimum of 0.005 inch (0.127 mm); (3) setting the allowable defect length as a continuous function of defect depth (height for buried defects); (4) allowing the use of any valid CTOD toughness greater than a set minimum value; (5) revising the notching procedure for HAZ CTOD testing. These recommendations are interdependent. Selectively adopting any of those recommendations may result in undesirable consequences. For instance, lowering minimum CTOD requirements necessitates the revision of allowable defect height. Adding the plastic collapse criterion would almost certainly require the change of defect length allowance of the fracture criterion from the current step function to a continuous relation. It should be made absolutely clear that lowering the minimum CTOD requirements for using Appendix A does not mean inferior weld quality control. It merely allows the assessment of significance of weld defects using the fracture mechanics methodology that has been proven effective. The interim step for the CSA Z662 Appendix K is revising the plastic collapse criterion. These revisions, when implemented, should result in more consistent degree of conservatism than the current codes. In certain cases, the size of the allowable defects is less restrictive than the current codes while maintaining consistent and adequate safety margin. This should translate to cost savings in both new construction and the maintenance of existing pipelines without sacrificing the safety and integrity of the pipelines.

Development of a FAD-Based Girth Weld ECA Procedure: Part I — Theoretical Framework

2002 ◽  
Author(s):  
Yong-Yi Wang ◽  
David Rudland ◽  
David Horsley
Keyword(s):  
Limit Load ◽  
Weld Strength ◽  
Plastic Collapse ◽  
Mismatch Correction ◽  
Load Limit ◽  
Failure Assessment ◽  
Scale Test ◽  
Girth Welds ◽  
Extensive Experimental Data ◽  
Experimental Data Analysis

Beginning in the late 1970’s and early 1980’s, “alternative defect acceptance criteria” were adopted in various codes and standards in the pipeline industry. These criteria relate the tolerable defect sizes with the magnitude of loads and materials’ resistance to failure. They allow engineers to assess the suitability of the pipes containing defects for intended service conditions, or fitness-for-service. Assessments based on the fitness-for-service principles are often referred to as Engineering Critical Assessment, or ECA. Although most of these codes are based on fracture mechanics principles, the defect tolerance levels vary significantly from code to code. This paper describes a two-year effort funded by PRCI (Pipeline Research Council International) to develop an ECA procedure specifically tailored to pipeline girth welds. The newly developed procedure is in FAD (failure assessment diagram) format. The key features of this procedure are provided in this paper. Based on prior research and extensive experimental data analysis, a modified Miller plastic collapse solution was selected for its rigorous formulation and good agreement with full-scale test results. The effects of weld strength mismatch on plastic collapse load (limit load) were examined and validated through finite element (FE) analysis. Parametric formulae of mismatch correction factors to the plastic collapse solution were adopted. The stress intensity factor solutions of finite-length surface-breaking defects in girth welds were developed and validated. Failure assessment curves (FACs) for girth weld defects were generated. These curves incorporated the effects of material’s strain hardening rate and defect size. They are more accurate than some of the generic material and defect independent FACs, yet easy to use.

scholarly journals A113 COST SAVINGS OF SEROLOGIC VERSUS BIOPSY PROVEN DIAGNOSIS OF PEDIATRIC CELIAC DISEASE

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. 131-132
Author(s):  
M Wiepjes ◽  
H Q Huynh ◽  
J Wu ◽  
M Chen ◽  
L Shirton ◽  
...  
Keyword(s):  
Health Care ◽  
Celiac Disease ◽  
North America ◽  
Cost Saving ◽  
Health Care System ◽  
Cost Savings ◽  
Serologic Diagnosis ◽  
Children's Hospital ◽  
Children’S Hospital ◽  
Care System

Abstract Background Celiac disease (CD) affects approximately one percent of the population in Canada and the United States. At present, endoscopic diagnosis (ED) of CD remains the gold standard in North America, despite mounting evidence and validated European guidelines for serologic diagnosis (SD). Within publicly funded healthcare systems there is pressure to ensure optimal resource utilization and cost efficiency, including for endoscopic services. At Stollery Children’s Hospital, Edmonton, Canada, we have adopted serologic diagnosis as routine practice since 2016. Aims The aim of this study is to estimate cost savings, i.e. hard dollar savings and capacity improvements, to the health care system as well as impacts on families in regard to reduced work days lost and missing child school days for SD versus ED. Initial cost saving data is presented. Methods Micro-costing methods were used to determine health care resource use in patients undergoing ED or SD from 2017–2018. SD testing included anti-tissue glutaminase antibody (aTTG) ≥200IU/mL (on two occasions), human leukocyte antigen (HLA) DQA5/DQ2, blood sampling, transport and laboratory costs. ED diagnosis included gastroenterologist, anesthetist, OR equipment, staff, overhead and histopathology. Cost of each unit of resource was obtained from the schedule of medical benefits (Alberta) and reported average ambulatory cost for day hospital endoscopy for Stollery Children’s Hospital determined in 2016; reported in CAN$. Results Between March 2017-December 2018, 473 patients were referred for diagnosis of CD; 233 had ED and 127 SD. Estimated cost for ED was $1240 per patient; for SD was $85 per patient (6.8% of ED cost). Based on 127 patients not requiring endoscopy and a cost saving of $1155 per patient there was a total cost savings of $146,685 over 22 months. Conclusions A SD approach presents a significant cost savings to the public health care system. It also frees up valuable endoscopic resources, and limits exposure of children to the immediate and long-term risks associated with anesthesia and biopsy. SD also decreases time to diagnosis and the cost of the process to families (lost days of school/work, travel costs etc.). Our costing data can be used in combination with mounting evidence on the test performance of SD versus ED to determine cost-effectiveness of serological diagnosis for pediatric CD. Given the potential for cost saving and more efficient operating room utilization, SD for pediatric CD warrants further investigation in North America. Funding Agencies None

Integrity Management of Ground Movement Hazards

2016 ◽  
Author(s):  
Yong-Yi Wang ◽  
Don West ◽  
Douglas Dewar ◽  
Alex McKenzie-Johnson ◽  
Millan Sen
Keyword(s):  
Management Program ◽  
Ground Movement ◽  
Tensile Failure ◽  
Weld Strength ◽  
Factors Affecting ◽  
Ground Movements ◽  
Decision Points ◽  
Starting Point ◽  
Integrity Management ◽  
Girth Welds

Ground movements, such as landslides and subsidence/settlement, can pose serious threats to pipeline integrity. The consequence of these incidents can be severe. In the absence of systematic integrity management, preventing and predicting incidents related to ground movements can be difficult. A ground movement management program can reduce the potential of those incidents. Some basic concepts and terms relevant to the management of ground movement hazards are introduced first. A ground movement management program may involve a long segment of a pipeline that may have a threat of failure in unknown locations. Identifying such locations and understanding the potential magnitude of the ground movement is often the starting point of a management program. In other cases, management activities may start after an event is known to have occurred. A sample response process is shown to illustrate key considerations and decision points after the evidence of an event is discovered. Such a process can involve fitness-for-service (FFS) assessment when appropriate information is available. The framework and key elements of FFS assessment are explained, including safety factors on strain capacity. The use of FFS assessment is illustrated through the assessment of tensile failure mode. Assessment models are introduced, including key factors affecting the outcome of an assessment. The unique features of girth welds in vintage pipelines are highlighted because the management of such pipelines is a high priority in North America and perhaps in other parts of the worlds. Common practice and appropriate considerations in a pipeline replacement program in areas of potential ground movement are highlighted. It is advisable to replace pipes with pipes of similar strength and stiffness so the strains can be distributed as broadly as possible. The chemical composition of pipe steels and the mechanical properties of the pipes should be such that the possibility of HAZ softening and weld strength undermatching is minimized. In addition, the benefits and cost of using the workmanship flaw acceptance criteria of API 1104 or equivalent standards in making repair and cutout decisions of vintage pipelines should be evaluated against the possible use of FFS assessment procedures. FFS assessment provides a quantifiable performance target which is not available through the workmanship criteria. However, necessary inputs to perform FFS assessment may not be readily available. Ongoing work intended to address some of the gaps is briefly described.

Latest Drilling Techniques Applied to Coring Operations of a Complex Subsurface Geology in WCSB Led to Operational Success and Cost Savings While Setting a Record in North America

2017 ◽  
Author(s):  
Ali Hooshmandkoochi ◽  
Farid Shirkavand ◽  
Richard Prokopchuk ◽  
Nadine Osayande ◽  
Ali Yousefi Sadat ◽  
...  
Keyword(s):  
North America ◽  
Cost Savings ◽  
Subsurface Geology

Effects of Weld Strength Heterogeneity on Crack Driving Force in Stress and Strain Based Design Scenarios

2014 ◽  
Author(s):  
Stijn Hertelé ◽  
Noel O’Dowd ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Driving Force ◽  
Large Scale ◽  
Limit State ◽  
Weld Strength ◽  
Force Response ◽  
Crack Driving Force ◽  
Key Factor ◽  
Weld Properties ◽  
Girth Welds ◽  
Strain Hardening Behavior

Weld strength mismatch is a key factor with respect to the assessment of a flawed girth weld. However, it is challenging to assign a single strength mismatch value to girth welds, which are generally heterogeneous in terms of constitutive behavior. The authors have recently developed a method (‘homogenization’) to account for weld strength property variations in the estimation of crack driving force response and the corresponding tensile limit state. This paper separately validates the approach for stress based and strain based assessments. Whereas homogenization is reliably applicable for stress based assessments, the strain based crack driving force response is highly sensitive to effects of actual heterogeneous weld properties. The sensitivity increases with increased weld width and decreased strain hardening behavior. For strain based design, a more accurate methodology is desirable, and large scale testing and/or advanced numerical modeling remain essential.

Development of Defect Interaction Criteria for Pipeline Girth Welds Subjected to Plastic Collapse Conditions

2006 ◽  
Author(s):  
Wim De Waele ◽  
Rudi Denys ◽  
Antoon Lefevre
Keyword(s):  
Large Scale ◽  
Specific Interaction ◽  
Ductile Failure ◽  
Elastic Interaction ◽  
Tensile Tests ◽  
Ductile Material ◽  
Plastic Collapse ◽  
Material Behaviour ◽  
Defect Interaction ◽  
Girth Welds

Multiple defects in welds, when detected, have to be assessed for interaction. Current defect interaction rules are largely based on linear elastic fracture mechanics principles (brittle material behaviour). Pipeline welding codes, however, specify toughness requirements to ensure ductile failure by plastic collapse. Therefore, the use of current (elastic) interaction rules for ductile girth welds can lead to unnecessary and possibly harmful weld repairs or cutouts. This paper reports on an assessment of the engineering significance of existing pipeline specific interaction criteria and on the development of new criteria. Rules for the interaction of coplanar surface breaking defects and ductile material behaviour have been developed on the basis of the performance requirement of remote yielding. The results of large-scale tensile tests illustrate that current interaction rules have a high degree of conservatism for plastic collapse conditions. The test data have been used to demonstrate that the developed procedure can be safely used for ductile girth welds.

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.

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.

Limit Plastic Collapse on Remaining Ligament of Flawed Welds for ECA Application

2014 ◽  
Author(s):  
Antonio Carlucci ◽  
Kamel Mcirdi
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Mechanical Strain ◽  
Plastic Collapse ◽  
Fracture Toughness Test ◽  
Element Analysis ◽  
Critical Fracture ◽  
Failure Assessment ◽  
The One ◽  
Girth Welds

Engineering Critical Assessments (ECAs) are routinely used to provide defect acceptance criteria for pipelines girth welds. The Failure Assessment Diagram (FAD) concept is the most widely used methodology for elastic-plastic fracture mechanics analysis of structural components and adopted by standards/documents including BS7910 [1], API579-1/ASME FFS-1 [2], R6 [3]. It is defined by two criterion Kr and Lr which describe the interaction between brittle fracture and fully ductile rupture: Kr measures the proximity to brittle fracture whereas Lr reflects the closeness to plastic collapse. The BS7910 FAD level 2B is the most employed for assessment of flaws under mechanical strain lower than 0.4%, the FAD associated is material-specific and it based on single toughness value obtained from CTOD test, the latter-on gives no information about the tearing initiation. The objective of this paper is to propose an approach for determination of the critical fracture toughness (associated to zero-tearing: JΔa=0). This approach is based on the comparison between the load-CMOD curve provided from a fracture toughness test to the one obtained by Finite Element Analysis (FEA). The goals is to propose a conservative guidance on how to identify a remote strain level below which it may be considered guaranteed the integrity of the remaining ligament.

Plastic Collapse Load for Vessel With External Flaw Simultaneously Subjected to Internal Pressure and External Bending Moment: Experimental and FEA Results

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Shinji Konosu ◽  
Masato Kano ◽  
Norihiko Mukaimachi ◽  
Hiroyuki Komura ◽  
Hiroyuki Takada
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Pressure Ratio ◽  
Safety Margin ◽  
Bending Moment ◽  
Plastic Instability ◽  
Plastic Collapse ◽  
Collapse Load ◽  
The Status ◽  
Work Done

This paper is based on work done to establish the validity of a simple engineering approach to assess plastic collapse for a vessel with a local thin area (LTA). The approach is based on a recently developed p-M (internal pressure ratio and external bending moment ratio) diagram, which is an easy way to visualize the status of a vessel with a LTA simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point (Mr,pr) lies inside the p-M line, the vessel with the LTA is judged to be safe. Numerous experiments and finite element analyses for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are similar to those calculated under the proposed p-M line based on the measured yield stress. The p-M line adopted in the Ibaraki fitness for service (FFS) rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0–3.0, about 1.5–4.0 for the TES loads at LTA, and 2.5–6.5 for the plastic instability (break) loads.

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