bluuebunny/crossref_metadata_2025_split huggingface dataset:
Under Pressure Welding and Preheat Temperature Decay Times on Carbon Dioxide Pipelines
Authors: Slater Simon , Andrews Robert , Boothby Peter , Barnett Julian , Armstrong Keith 
Published: December 2014

Whilst there is extensive industry experience of under pressure welding onto live natural gas and liquid pipelines, there is limited experience for Carbon Dioxide (CO2) pipelines, either in the gaseous or dense phases. National Grid has performed a detailed research programme to investigate if existing natural gas industry under pressure welding procedures are applicable to CO2 pipelines, or if new specific guidance is required. This paper reports the results from one part of a comprehensive trial programme, with the aim of determining the preheat decay times, defined by the cooling time from 250 °C to 150 °C (T250–150), in CO2 pipelines and comparing them to the decay times in natural gas pipelines. Although new build CO2 pipelines are likely to operate in the dense phase, if an existing natural gas pipeline is converted to transport CO2 it may operate in the gaseous phase and so both cases were considered. The aims of the work presented were to:
• Determine the correlations between the operating parameters of the pipeline, i.e. flow velocity, pressure etc. and the cooling rate after removal of the preheat, characterised by the (T250–150) cooling time.
• Compare the experimentally determined T250–150 cooling times with the values determined using a simple one dimensional heat transfer model.
• Define the implications of heat decay for practical under pressure welding on CO2 pipelines.
Small-scale trials were performed on a 150 mm (6″) diameter pressurised flow loop at Spadeadam in the UK. The trial matrix was determined using a one dimensional heat transfer model. Welding was performed on a carbon manganese (C-Mn) pipe that was machined to give three sections of 9.9 mm, 19.0 mm and 26.9 mm wall thickness. Trials were performed using natural gas, gaseous phase CO2 and dense phase CO2; across a range of flow velocities from 0.3 m/s to 1.4 m/s.
There was relatively good agreement between the T250–150 cooling times predicted by the thermal model and the measured T250–150 times.
For the same pipe wall thickness, flow velocity and pressure level, the preheat decay cooling times are longest for gaseous phase CO2, with the fastest cooling rate recorded for dense phase CO2.
Due to the fast cooling rate observed on dense phase CO2, the T250–150 times drop below the 40 second minimum requirement in the National Grid specification for under pressure welding, even at relatively low flow velocities. The practical limitation for under pressure welding of pipelines containing dense phase CO2 will be maintaining sufficient preheating during welding.
The results from this stage of the technical programme were used to develop the welding trials and qualification of a full encirclement split sleeve assembly discussed in an accompanying paper (1).
Bending Deformation Capacity of Large-Diameter Spiral-Welded Tubes
Authors: Vasilikis Daniel , Karamanos Spyros A. , van Es Sjors H. J. , Gresnigt Arnold M. 
Published: December 2014

Numerical simulations are conducted to define the bending deformation capacity of large-diameter spiral-welded tubes, towards efficient strain-based design. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall. Bending moment, curvature and ovalization are monitored through the numerical analysis, and comparison is conducted with available test data on two 42-inch-diameter tubes, with D/t ratio of 67 and 119, described in detail elsewhere.
The analysis accounts for the actual material properties. Initial geometric imperfections (profile, thickness, ovalization) are obtained from the tested specimens. Furthermore, residual stresses are also considered in the analysis, as computed by a numerical simulation of the cold bending process. A parametric analysis is also conducted on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes. Finally, a comparison with design equations for tube bending deformation capacity is conducted.
A Structured Approach for Managing Engineering Assessments
Authors: Reed Mike , Sahney Reena , Skibinsky Darren 
Published: December 2014

Alliance Pipeline, (Alliance), an integrated Canadian and U.S. high-pressure rich natural gas transmission pipeline system, conducts Engineering Assessments for a variety of reasons related to integrity activities such as investigative digs, right-of-way crossings, encroachments and program review; however, the need for a consistent and systematic approach to perform work of this nature was identified. As such, the company launched an initiative to develop a structured approach for undertaking, reviewing and approving Engineering Assessments.
The specific challenge in developing a framework for conducting Engineering Assessments is twofold: the framework must be scalable, to address a broad range of situations, while remaining practical to use and understand. In light of these requirements, Alliance chose to adopt a “Tiered” approach to identifying requirements associated with each engineering assessment. The Tier of the Engineering Assessment is defined based on two primary factors: the complexity of the analysis (i.e., whether the methodology of the analysis is well established or not) and the nature of the underlying assumptions (i.e., whether the assumptions associated with the analysis are within established parameters). Once the appropriate Tier has been selected, the framework then provides guidance regarding the specific requirements in the areas of: responsibilities and qualifications of individuals for preparation, review and approval of the assessment as well as documentation.
The implementation and use of the structured approach was intended to ensure the Engineering Assessments undertaken within pipeline integrity were technically sound, while recognizing that a broad range of technical complexity, skill level and decision making are associated with Engineering Assessment. Overall, this approach will allow Alliance to achieve a degree of uniformity of its Engineering Assessments in order to manage risks effectively, while addressing the needs of a broad range of scenarios that rely on the methodology.
Practical Application of Low Constraint SENT Fracture Toughness Testing for Pipeline Girth Welds
Authors: Kirk Peter B. Schamuhn , Chum Victoria 
Published: December 2014

Fracture mechanics methods for engineering assessment of acceptable flaw sizes in pipeline girth welds have been widely and successfully embraced by the pipeline industry. Advancements driven by strain-based design have identified elevated conservatism in assessment of material toughness by standardized high constraint fracture toughness test methods. Methods of reducing conservatism include the use of constraint adjustment factors or constraint-matched test specimens. Variants of the single edge-notched tensile (SENT) specimen have been widely reported as appropriate constraint-matched laboratory-scale specimens. This paper presents the results of SENT and SENB toughness testing of pipeline girth welds in both ductile and brittle/transitional temperature regimes.
Testing of 19.2mm weldments was conducted at room temperature (RT) and −5°C, with the intent of assessing the practicality of the single-specimen SENT methodology for low constraint fracture toughness assessment of typical high toughness production welds. Typical SENT specimens exhibited up to 50% higher upper shelf toughness results compared to SENB specimens. The majority of specimens failed E1820 crack straightness validity criteria, while the majority of specimens met E2818 (ISO 15653) criteria.
Testing of 10.4mm weldments was conducted on pipe known to exhibit low HAZ toughness (brittle pop-ins) at −5°C in the SENB configuration. SENT testing was conducted over temperatures spanning typical operating, design, and winter construction lowering-in temperatures (i.e. RT to −35°C), with the intent of investigating material sensitivity to brittle response under constraint-matched conditions. Brittle responses were observed in SENT specimens at both −20°C and −35°C, and ductile (upper shelf) behavior at −5°C and warmer; SENB specimens exhibited consistently brittle behavior at RT and −5°C, suggesting a HAZ transition temperature shift of at least −30°C for the constraint-matched test geometry.
Microstructure and Toughness of Simulated Grain Coarsened Heat Affected Zones in X80 Pipe Steels
Authors: Gianetto J. A. , Fazeli F. , Chen Y. , Shalchi-Amirkhiz B. , Smith T. 
Published: December 2014

The objective of this research was to gain a better understanding of the influence of essential welding variables on microstructure and properties of the grain-coarsened heat-affected zone (GCHAZ) regions formed in pipeline girth welds. In this study, thermal simulation techniques were used to provide a detailed evaluation of the GCHAZ microstructure evolution and intrinsic toughness for two different pipe steels subjected to known welding thermal cycles.
The continuous cooling transformation (CCT) diagrams for the GCHAZ were determined by means of dilatometric techniques with a peak temperature (Tp) = 1350°C and a range of cooling times (Δt800–500 = ∼1 to 100 s). The transformation start and finish temperatures were used to create GCHAZ CCT diagrams for two X80 pipe steels. To further assist with the interpretation of CCT results both light optical microscopy (LOM) and microhardness surveys were used. The results revealed that transformation to predominantly low carbon lath martensite or fine bainite occurred for short cooling times, while bainite formed at intermediate cooling times and upper or granular bainite was obtained for longer cooling times. Some of the detailed features of these simulated GCHAZ microstructures were characterized by scanning electron and transmission electron microscopy (SEM and TEM) in order to better quantify the phases in selected samples. This analysis clearly indicates that despite similar carbon equivalents (CEs), the response of each steel to given GCHAZ thermal was quite different.
The GCHAZ Charpy-V-notch (CVN) impact energy transition curves for the series of single thermal cycles with cooling times, Δt800–500 = 6, 15 and 30 s and were compared against those obtained for the respective pipe steels. The results showed that there were upward shifts in transition temperature for the simulated GCHAZs relative to the respective pipe steels. This overall reduction of notch toughness was attributed to variations in microstructural features for the respective GCHAZs.
Research of Gas Losses During Transportation in Gas Transmission Trunk Line
Authors: Chen Rui , Xing Xiaokai , Jiang Liansheng , Pang Shubao , Tian Xiaocui 
Published: December 2014

Gas loss during transportation is an important technical and economic indicator in assessing the level of production costs and economic benefits of natural gas enterprises. As the gas pipeline transmission trade continues to expand in China, the problems of gas losses have become increasingly prominent. Take one joint-stock gas pipeline of CNPC for example; the total output is about 24.2 billion cubic meters in 2012, while the amount of gas losses has reached about 60 million cubic meters, which brings significant economic losses to the enterprise, so it is necessary to carry out study on gas losses during transportation in gas transmission trunk line. For a trunk line system, gas losses generally refer to the flow quantities reduction during the process of gas purchase, transportation and sale, considering the variation of gas pipeline inventory, the amount of self-consumed gas and venting amount. Gas loss during transportation is mainly caused by measurement error of metering devices, but it is also related to the calculation deviation of gas pipeline inventory and venting amount.
In this paper, according to the flowmeter configuration in each station, the model of trunk line metering system is established, and the calculation method of flow measurement uncertainty of overall trunk line system is introduced. The early warning indicators of gas loss in different calculation cycle are obtained, by which the gas loss problems can be foud timely. A real case is introduced to evaluate its application of early warning indicators of gas loss. In the study of ultrasonic flowmeter, the influence of noise, gas component and dirty sediment on measurement error is analyzed. A transient simulation model of the trunk line has been built, based on the gas pipeline network simulation software TGNET, to analyze the influence of non-steady state on the calculation of gas pipeline inventory. Finally, some suggestions are made to lower gas losses during transportation from aspects of technical operations and management.
The Essential Welding Variable Methodology and its Application in Welding Procedure Development for Mechanized Girth Welds of X100 Line Pipes
Authors: Funderburk Scott , Spielbauer Paul , Chen Yaoshan , Quintana Marie 
Published: December 2014

The mechanical properties of X100 pipeline girth welds are quite sensitive to welding parameters and the design range for a viable welding procedure is narrower compared to pipeline steels of lower grades. The use of a high-productivity welding process, such as dual-torch gas metal arc welding (GMAW), further compounds the dependency of weld properties on welding parameters. Consequently, for X100 pipe welding procedure development, the path to achieve the required weld performance can be a time-consuming and costly process.
Developed in a recently completed project, the essential welding variable methodology provides an effective approach to optimize the development process for X100 pipe welding, with the benefits of reducing development time and saving cost. The present paper presents a practical case study of the methodology for girth welds.
The present paper focuses on the information needed and the analyses performed in the application of the methodology to the process of welding procedure development for a dual-torch pulsed GMAW (GMAW-P) procedure.
Using an analysis tool that can predict the thermal cycles from welding parameters and the available knowledge of microstructure and mechanical responses of both pipe materials and weld metals to welding thermal cycles (cooling rate), several candidates of dual-torch pulsed GMAW procedures were evaluated first for cooling times to help the determination of the final welding procedures. The finalized welding procedures used for the production of the qualification welds were evaluated to estimate the mechanical properties of the girth welds. The estimated weld properties will be compared to those from the test results when they become available.
Detection and Sizing of Subcritical Cracks Using Ultrasonic In-Line Inspection Methods
Authors: Bauer Stefan , Brueske Henning 
Published: December 2014

The high pressure liquid and gas pipeline network is aging in all regions around the globe and becomes more and more vulnerable to integrity threats. Besides general corrosion, stress corrosion cracking becomes an increasingly important topic. Pipeline operators are facing the challenge to address these threats. Most (31%) of the pipelines worldwide are pipelines with diameters ≤10″ [1]. Providing a better inline inspection service starting with small diameter pipelines will therefore address the threats arising from stress corrosion cracking most effectively. This way the typical diameters of pipelines posing risks served first.
Ultrasound inline inspection for pipelines is known for years and provide several advantages over hydrostatic tests. Its most important advantage for pipeline operators is that sub-critical flaws can be detected, which results in a comprehensive picture of the integrity status of the pipeline.
Despite the advantages and the experience with ultrasound inline inspection, the sizing precision and the sizing confidence are two factors limiting the success of the ultrasound inline inspection technology.
This paper presents several measures to address these two issues and thus to provide a more valuable service for pipeline operators.
There are two ways to increase the sizing precision and the sizing confidence: either to develop new procedures to evaluate existing data or to gather more or better data during inline inspection. The focus in this paper will be on the second option.
Three measures are described in this paper: first, using a new design to improve the guidance of the sensor carrier leading to better data quality, especially at welds. Second, using more sensors for the inline inspection tools. This will not only provide a more precise circumferential position of the flaws but also more data for every flaw. Finally, recording more echoes at each point of the pipeline which is the basis to extract more information from every measurement.
Enhancing Pipeline Research Project Management With Post-Assessment
Authors: Wang Yuqin , Zeng Libo , Zhao Choumin , Kang Liping , Qian Chengwen 
Published: December 2014

Post-assessment of pipeline research project assesses the project implementation process and the subsequent effect of the project application. The former assesses the realization of the research goals, the quality of the project implementation, the conformity to the research plan, and the ability of the project manager, while the latter attaches more importance on the long-term application and achievement of the technology developed by the research project after it has been accepted by the administrative department for one year or more. Post-assessment of pipeline research project provides a reference for scientific and technological administrative department in decision-making to improve project quality and investment efficiency of research activities, upgrade the management level.
PetroChina Pipeline Company (PPC) used two years to set up the index system, choose the weight factors and build the assessment modeling of the post-assessment method. After that, a large number of research projects had been assessed by project managers and management staff to test the post-assessment method in order to modify the assessment software.
This paper will:
• Demonstrate the characteristics of the post-assessment of pipeline research project
• Describe the scope and content of the post-assessment
• Illustrate the process of the post-assessment
• Identify required index system and calculation modeling
• Discuss advantages of post-assessment in enhancing pipeline research project management
The Effects of Corrosion Measurement Error on a Safety Risk Assessment: A TransGas Case Study
Authors: Bandstra Daryl , Gorrill Corey 
Published: December 2014

The risk of pipeline failure is a measure of the state of knowledge of the pipeline; improved knowledge of the pipeline reduces the uncertainty and therefore can reduce the associated risk. Specifically for corrosion defects, the knowledge of the number and size of defects is often obtained using in-line inspection tools which have uncertainty associated with their measurement capabilities. Quantitative Risk Assessment (QRA) is a methodology that objectively assesses a range of pipeline integrity threats including the threat of corrosion failure. QRA can incorporate the impact of significant sources of analysis uncertainty, such as feature sizing in risk estimates. This paper discusses an application of QRA used to evaluate the operating risk of high pressure transmission pipeline segments in the TransGas system. Specific examples are described in which the inspection tool sizing uncertainty was shown to exert a significant influence on the calculated risk levels.
In carrying out the analysis, the failure probability models selected were dependent on the nature of the integrity threat and the type of information available for each pipeline. For the assessment of corrosion integrity, the results of in-line inspections were used directly in determining failure likelihood. For the other threats including equipment impact, geotechnical hazards, manufacturing cracks and stress corrosion cracking, the probability of failure was estimated from historical failure rates with adjustments to reflect line-specific conditions. Failure consequences were estimated using models that quantify the safety implications of loss of containment events. Using these models, safety risk measures were calculated along the length of each pipeline. The results of the analysis show the benefit of the use of inspection technologies with improved sizing accuracy, in terms of reduction in expected operating risk.
Managing a New Pressure Cycling Reality in Liquid Pipelines
Authors: Haider Syed J. , Textor Steven , Sutton Aaron , Hubert Yvan 
Published: December 2014

Pressure cycling is one of the many operational factors a liquids pipeline company has to contend with in their pipeline integrity cracking program. The management of pressure cycling is important because of the potential development and growth of cracks in the pipe wall by fatigue mechanism where pressure cycling acts as the driving force. The operational source of these cycles can be complex but often include planned start/stops, batch pigs passing pump stations, mid-point injections or deliveries, viscosity changes due to commodity transitions, flow rate changes, and unplanned line outages. The first step to understanding pressure cycling is the development of a methodology which defines pressure cycling targets and monitors cycling on the line. Enbridge Pipelines Inc. (Enbridge) has developed two processes to manage pressure cycling on existing and future assets. These procedures help define the path to limiting pressure cycling but also steer the cultural change required to mitigate this risk within an established operating environment.
All operational lines within Enbridge Pipelines Inc. are monitored monthly for pressure cycling risks. Understanding the impact of pressure cycling on these lines can be very complex. To determine the risks associated with an operating pipeline the line’s susceptibility to cracking and its pressure cycling severity must be understood. Once the risks are identified, a pressure cycling mitigation plan, to ensure continued safe operation of the asset can be developed. In order to complete a mitigation plan a detailed operational review needs to be conducted and a company-wide team engaged. The team will determine how the existing operational philosophy can change or what physical modifications are required to improve the current operation and limit or reduce pressure cycling.
All new projects within Enbridge have to meet the “Fatigue Design Standard for New Pipelines” to ensure the new line has been designed to handle the estimated cycling. To estimate the cycling of a new line the operational philosophy needs to be well understood; this includes: injection/delivery points, planned maintenance outages, estimated unplanned outages, commodity transitions, transient mitigation, and pressure profiles for each known event.
This paper will focus on the processes Enbridge uses to manage pressure cycling on new and existing lines. A separate paper from Enbridge titled “IPC2014-33566: Allowable Pressure Cycling Limits for Pipelines” focuses on the fatigue science and how the pressure cycling targets are determined for the pipelines.