bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Investigation and Assessment of Low-Frequency ERW Seam Imperfections by EMAT and CMFL ILI
Authors: Kania Richard , Weber Ralf , Klein Stefan
Published: December 2014

The occurrence of low-frequency Electric Resistance Welded (LF-ERW) or Electric Flash Welded (EFW) line pipe imperfections has been the root cause of many integrity management initiatives to minimize and mitigate the risk of pipeline failure across the oil & gas pipeline industry. Since their first appearance in the 1920s, defects in or near the LF-ERW and EFW seam repeatedly lead to either hydrostatic test or in-service failures. Where in the past In-Line Inspection (ILI) technologies might have experienced limitations in addressing vintage ERW line pipe defects, modern smart ILI technologies show enhanced capabilities. High resolution Electro-Magnetic Acoustic Transducer (EMAT) and Circumferential Magnetic Flux Leakage (CMFL) ILI technologies have advanced in the recent years enabling more challenging inspections. This paper summarizes the inspection results of 22″ ERW line pipe defects detected and reported by EMAT and CMFL. Correlation of ILI and manual NDE data enables evaluation of current ILI capabilities and improvement of current defect assessment methods.
A Case Study of Stress Analysis of Pipeline in River Crossing Tunnel
Authors: Wang Xiaolin , Qi Xianzhi , Fang Jianhua , Di Yan
Published: December 2014

Tunnel by digging is accepted as one of the most effective methods for river-crossing in pipeline constructions, especially for large river-crossing. Pipeline is often installed on a series of low supports in the tunnel underneath river. Generally, pipeline in tunnel experiences various loadings during service period due to operational and environmental conditions, such as operation pressure fluctuation, external temperature variation or support damage. Under these loadings, high stress and huge longitudinal force may be accumulated in pipe that may eventually result in pipeline elongation or bending. These kinds of deformation have been found in pipelines in some river crossing tunnels. To investigate the mechanical behavior of pipeline in tunnel crossing, finite element models (FEM) are produced to simulate pipeline operation condition and the maximum design operation condition. With FEM, stress distribution and deformation of pipeline are analyzed. The result shows that 1) axial elongation of pipeline from finite element analysis is in accordance with that of on-site measurement, 2) pipeline is analyzed to be safe under operation condition or the maximum design operation condition, 3) supports should be designed and constructed with enough strength to resist the force from pipeline deformation, and 4) some treatments are proposed to solve the problems of pipeline in tunnel crossing. Finally, a new type of support with vertical constrained damping is designed for stress and deformation relief of pipeline in tunnel crossing.
Pipelines Risk and Integrity Management in Shared Right of Way: Case Study
Authors: Gonzalez Jose Luis Martinez , Betancourt Enrique Rodriguez , Ramirez Roberto , Gomez Lorenzo Martinez , Simon Arturo Godoy
Published: December 2014

Some pipeline operators evaluate risk on an individual pipeline basis even if the right of way (ROW) is shared with other pipelines. Determining a ROW strip risk condition may be complex or quite simple, according to the model adopted by the analyst. If the pipelines allocated in a shared ROW belong to different operators it is very likely that they apply different methods to evaluate a risk condition. The relative risk contribution cannot be added to estimate the risk of a ROW strip. In Mexico insurance companies request studies of collective risk in pipelines to decide whether to increase a prime or reduce coverage. This request does not have technical support or engineering guidelines to perform the analysis. In Pemex there are few documented events where a pipeline failure affects parallel pipelines, known as collateral damage. There are some methods to estimate a potential collateral damage as a function of soil damping and separation between pipelines (Ref.2). This scheme applies for gas pipelines and has to be complemented with an ignition scenario probabilistic analysis. In the case of hazardous liquids scenarios of leak and rupture have to be considered, including potential shed routes, product concentration sites and operator response capability. Since risk is assessed with particular and specific attributes of a pipeline the probability of failure cannot be directly added to adjacent pipelines. There are some failure mechanisms common for pipelines sharing the ROW, such as external corrosion and stress corrosion cracking (SCC), with different intensity when considering coating and corrosion protection (CP) efficiency. Internal corrosion depends on other factors such as product features so it does not necessarily repeat with the same magnitude in all pipelines. Pipeline threats can be expected to be the same in this case — with different intensity. For instance, third party activity and weather can threaten all pipelines allocated in the same ROW. These pipelines may present similar symptoms with different magnitude. Cover depth, additional protection and wall thickness play an important role in reducing third party (TP) and weather and outside forces (WOF) threats. The paper provides risk results of a ROW strip based on probability of failure values. Pipelines with biggest risk contribution were identified and integrity management alignment diagrams were obtained to correlate with risk values. A simple algorithm was developed to process risk results in terms on shared ROW buffer dimensions. The study is complemented with the results of a consequence simulation analysis for a gas pipeline
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.
Behaviour of Releases of Carbon Dioxide From Pipelines and Vents
Authors: Allason Dan , Armstrong Keith , Barnett Julian , Cleaver Phil , Halford Ann
Published: December 2014

A large Research and Development programme has been executed by National Grid to determine the feasibility of transporting carbon dioxide (CO2) by pipeline. Such pipelines would be required to form a transportation system to take the CO2 from its place of capture at an emitter’s site to a place of safe storage within a Carbon Capture and Storage (CCS) scheme. This programme received financial support from the European Union. As part of this programme, National Grid commissioned a series of experimental studies to investigate the behaviour of releases of CO2 mixtures in the gaseous and the liquid (or dense) phase. This has included simulating accidental releases in the form of punctures or ruptures of a buried pipeline and deliberate releases through different venting arrangements. This work is required, as CO2 has the potential to cause some harm to people if they are exposed to it for long enough at high concentrations. This paper gives an overview of the findings from this work and shows how the data has been used to help develop a number of the more pragmatic, predictive models for outflow and dispersion. This work complements the more theoretical studies carried out using state of the art advanced computational fluid dynamic models, employed by other UK based participants (University College London, University of Leeds, Kingston University and the University of Warwick) in the research programme.
Synergy in Leak Detection: Combining Leak Detection Technologies That Use Different Physical Principles
Authors: Han Peter Y. , Kim Mark S.
Published: December 2014

Different leak detection technologies offer different benefits and limitations. Popular options include real-time transient models, statistical volume balance analysis and negative pressure wave systems. Atmos offers a combination of different systems to improve the leak detection performance on a pipeline. This paper outlines the very successful integration of a Statistical Volume Balance System and a Negative Pressure Wave System on a crude oil pipeline. The live product withdrawal tests demonstrated that the combined system maximized the reliability, detection speed, location accuracy and sensitivity of the overall leak detection system. This paper will examine the benefits and technical challenges of combining these two leak detection technologies. The integrated solution delivers the reliability and robustness of the Statistical Volume Balance System together with the rapid response time and location accuracy of the Negative Pressure Wave System. The field application of the two systems integrated on a 170 kilometer crude oil pipeline will be explained in detail, along with the results of some actual controlled product withdrawal tests on the pipeline.
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.
Numerical Modeling for Steady-State Two Phase Flow in Gas-Condensate Pipeline
Authors: Wang Zhi , Gong Jing , Yin Tienan
Published: December 2014

Based on two-fluid approach, a numerical model coupled with phase behavior model and hydro-thermodynamic model, is presented for simulating steady-state two phase flow in gas-condensate pipeline. In this model, two-fluid model is adopted for hydraulic computation and a simplified mixture energy equation is developed to couple hydraulic and thermodynamic calculation. SIMPLE algorithm is improved for application in one-dimensional steady-state simulation of two phase flow. Hydraulic and thermal is coupled as one-way coupling. The model was validated through comparison to field data from five operational gas-condensate pipelines. It turns out that the numerical simulation in this paper has good stability and convergence and is capable of simulating the steady-state flow in gas-condensate pipelines.
Bulging Factor for Axial Surface Cracks in Pipes
Authors: Shim Do-Jun , Wilkowski Gery
Published: December 2014

The bulging factor for an external constant-depth axial surface crack in a pipe was calculated by 3D FE simulations. This was done in a manner consistent with Folias’s original work for the axial through-wall-cracked pipe bulging factor (MT), but was evaluated in the elastic to full-plastic conditions. The results demonstrated that the actual surface-cracked pipe bulging factor is considerably lower than the bulging factor empirically derived by Maxey/Kiefner (Mp) back in the 1970s. Based on the results of the present study, it is suggested that Mp function in the Ln-Secant equation is not truly a bulging factor for axial surface crack. Rather it is an empirically developed equation with many correction factors embedded in it to apply the Dugdale model for prediction of maximum pressure of axial surface-cracked pipes. However, due to this empiricism, this method becomes invalid (or overly conservative) when it is applied in predicting the crack-driving force using the J-based Ln-Secant equation.
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.
Inverse Fracture: What is it All About?
Authors: Hasenhütl Andre , Erdelen-Peppler Marion , Kalwa Christoph
Published: December 2014

The transition temperature behavior of pipes subjected to propagating fracture is assessed by means of Battelle Drop Weight Tear (BDWT) tests. These consist of notched specimens which are subjected to impact loading under a three point bend test configuration. The fracture surface is assessed to derive shear or brittle portions that are macroscopically visible. These have been shown to correspond well to the fracture surface of a pipe subjected to a propagating fracture. Historically, it is required for the test to either exhibit entirely ductile fracture or a combination of brittle and ductile provided that the test initiates in a brittle fashion with propagation in a ductile manner. Conversely, tests exhibiting ductile initiation with brittle or mixed brittle and ductile propagation are not acceptable to some standards/specifications. In recent times, this requirement has been softened in certain standards/specifications but it remains to be explained what these two diverging opinions are based upon and which one of the two is the correct one. This nominally unacceptable fracture mode has been termed inverse or abnormal fracture and is frequently observed with modern pipeline steels. Other than inverse fracture character, these specimens show every sign of highly ductile material being tested. The unanswered question is: does the brittle area reflect material properties or is it caused by the specific test conditions meaning that it is simply a testing issue? Furthermore, the reason to retain the requirement is not obvious and a procedure is missing on how to assess this type of specimen. The only possibility outlined in testing standards to avoid inverse fracture is the use of an alternative notch, the so-called Chevron notch that is supposed to facilitate brittle crack initiation. Mostly, the problem remains unsolved and further guidance is not given. Current research aims at avoiding invalid results by choosing different notches that could potentially be successful but also on checking the correspondence of results of testing inverse material to pipe behavior in West Jefferson tests. Alternatives discussed to avoid inverse fracture are, apart from the above named one, static pre-cracked notches and fatigue notches. Within this paper, test results of specimens notched with all of these notches are presented. None of these were successful in eliminating inverse fracture. Literature studies were conducted to understand the background of the requirement. Investigations of material behavior after having been subject to heavy pre-strain were carried out. The question is, on basis of the available evidence, which conclusions can be drawn and if these are sound enough to derive general guidance.
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.
Pressure Surge Relief Options in Terminal Design
Authors: Zhou Alan X. L. , Cabrejo Victor , Yu David
Published: December 2014

Terminals are an integral part of a pipeline system. Typically, petroleum products are transported from an initiating terminal to various delivery terminals along the pipeline. Operation safety is paramount in transporting petroleum products in the pipeline industry. Safety can affect the performance and economics of a pipeline system. While effective operation safety requires well-trained operators, operational procedures, and compliance with regulatory requirements, the best way to ensure operation safety is to implement safety systems during the design stage of the pipeline system. A pressure relief system is an important component of an engineered safety system. This system is intended to prevent catastrophic failure of the transport system due to overpressure conditions that can occur under abnormal operating conditions.

This paper discusses pressure surge relief as it applies to the design of pipeline terminals. Different pressure surge relief devices such as pressure relief valves and pressure surge vessels are considered and their advantages and disadvantages are discussed. The effects of transport rates, piping configurations, and other equipment operation, such as pumps and valves, on pressure surge relief system, are evaluated.

One of the primary objectives of this paper is to discuss pressure surge events, device simulations, and key parameters to consider when selecting a pressure surge relief system for a terminal design to ensure that the piping system and hydraulic components remain safe during abnormal operating conditions. Although the analyses presented in this paper are applicable across a broad range of operating conditions and equipment and devices in terminal system designs, it is not possible to cover all situations. As such, sound engineering principles and engineering judgment should always be applied in an engineering design.
Leak Detection Using Distributed Temperature Sensing: An Improved Calculation Method
Authors: Skoczylas Paul , Dessein Thomas , Rizwan Tania , Medynski Scott
Published: December 2014

This paper presents an efficient calculation to determine the transient heat transfer in ground surrounding a liquid pipeline. This improved calculation method was applied to support a feasibility assessment regarding implementation of Distributed Temperature Sensing (DTS) fibre optic systems for detection of leaks on an oil pipeline spanning long distances and varied geological conditions. With DTS, a leak or rupture could be detected if a portion of the sensor that is soaked is heated or cooled by leaked fluid. In many scenarios the temperature difference of a small leak may approach the sensing limits of the technology; calculating this limit requires an accurate understanding of the expected thermal characteristics of the fluid and soil surrounding the pipeline to identify where the technology is suitable and to calibrate accordingly. The method discussed in this paper was developed for use in heavy oil pipelines, for which changes in temperature have a large effect on the fluid viscosity, and therefore on frictional pressure losses. The model predicts the temperature profile in the soil surrounding a pipeline, including a number of transient effects. The model and results obtained are useful to identify optimal placement of a DTS cable, given a target size of detectable leak, time of year, and a number of parameters specific to the pipeline design. Importantly, this approach addresses changing geological conditions along the length of a pipeline, allowing an assessment of coverage and performance year round for the line under the most conservative case.
Excavation Assistance System Design Based on Human Factors: Functional and Technical Analysis
Authors: Perinet Romuald , Lecchi Maxime , Marmeys Thierry , Pognonec Gaël , Herchin Nicolas
Published: December 2014

External interference is the first cause of incidents on gas transmission pipelines in Europe in terms of frequency. The large majority of pipe breaks are indeed due to excavation works. Prevention barriers exist: slabs, warning tapes, surveillance patrols, public awareness campaigns, … but third party activities are gradually increasing and additional barriers are needed. Furthermore, incidents also occur on works contracted by gas companies themselves and specific barriers are missing for these particular situations. In this context, embedded systems for excavators can be interesting solutions to prevent the driver from hitting pipelines. However, studies conducted in the past have shown the limitations of such systems available on the market.

Thus, the CRIGEN (GDF SUEZ research center dedicated to gas and new energies) has worked on the specification of an embedded system, using an approach combining human factors and a functional analysis. This global method has been built to ensure that the potential solution will meet the need and that it will not have detrimental effects on the actual human organization which represents in itself a barrier.

This paper presents the main results of the work including the different methodologies and tools that have been used, but also the way they have been combined. The strong contribution of the human factors oriented analysis is detailed through: the identification of the hazardous situations to address, the identification of bias involved in incidents and the resulting safety functionalities for the system. Technical aspects of the method are also shown in the document, which includes a functional analysis and a benchmark of technologies of interest for the system. This allows a rather objective evaluation of several systems’ options combining different architectures and technologies. As a conclusion, a generic system architecture is proposed. This architecture mainly relies on existing tools and on a supervision unit. It is thought not to disturb the driver’s work but to help him digging in safer conditions by warning him in case of drift.
Response of Buried District Heating Pipelines Under Relative Axial Movements
Authors: Huber Michael , Wijewickreme Dharma
Published: December 2014

District heating (DH) systems are commonly used in urban areas to distribute thermal energy from central heat sources. Buried pipes, with a composite cross-sectional construction, are used transport a heated medium, usually water. These pipes expand and contract radially and axially due to changing water temperatures, invoking soil-pipe interaction situations during operation, and potentially leading to significant pipeline material strains. A series of full-scale tests were undertaken to specifically investigate the influence of thermal expansion on axial pullout resistance using DH pipes buried in sand in a full-scale soil-pipe interaction test chamber. During testing, the pipe is filled with water that is subjected to temperature changes to simulate field conditions. Axial pipe pull-out tests were conducted after applying a given “heating history” with axial pullout force and displacements recorded. The work leads to better understanding of soil-pipe interaction mechanisms generating currently scarce data needed for robust and cost-effective designs of DH pipe systems.
Tandem Flux-Cored Arc Welding for High Strength Line Pipe
Authors: Penniston Christopher J. , Huntley Robert M.
Published: December 2014

The benefits of mechanized welding for pipeline construction are well known, as reflected by the high industrial acceptance and usage of its variations. However, the engineering and qualification costs associated with the preparation of alternative acceptance criteria for typical pulsed and short-circuit MIG (GMAW-P and GMAW-S) girth welds can make the implementation of mechanization too costly and/or time consuming for small projects.

A multi-wire welding technology, employing a high-deposition consumable that possesses excellent positional capability, along with paired digitally controlled asynchronous inverter power sources, is presented.

Trials were performed on CSA Z245.1 914 mm (NPS 36) OD × 20.4 mm WT Grade 483 heavy wall high strength line pipe. One variant used an 8-head internal welding machine for the root pass, and a conventional single torch short-circuit GMAW hot pass in a compound narrow-groove configuration. A second variant utilized an externally applied controlled short-circuit GMAW-S process for the root pass in a factory-style pipe bevel configuration. Both variants employed fill and cap passes using tandem pulsed gas-shielded flux-cored arc welding (T-FCAW-G/P), using rutile consumables, with the “bug and band” MOW II mechanized welding system.

Basic mechanical testing was performed on the first weld variant, along with single-edge notched bend (SENB) crack tip opening displacement (CTOD) tests, and results are presented.

A productivity comparison is then shown, using weld data from the second weld variant against alternative processes, showing considerably lower fill and cap pass arc time using the T-FCAW-G/P process.

Given the process’s low tendency for the formation of planar discontinuities, the process is appealing for the use of “workmanship” acceptance criteria.

With further procedure development and fine-tuning of the process, tandem flux-cored arc welding may prove viable, particularly for “short” pipelines, where the costs of comprehensive engineering critical assessment/fitness-for-purpose weld procedure qualification and associated engineering work aren’t justified; as a higher productivity alternative to single wire flux-cored arc welding for mechanized tie-in welding; as a much higher productivity alternative to SMAW for tie-ins; or with a narrow groove design, mainline applications for longer-distance projects.
Field Testing of Negative-Wave Leak Detection Systems
Authors: Siebenaler Shane , Tervo Eric , Vinh Paul , Lewis Chris
Published: December 2014

The pipeline industry is improving its ability to detect and locate leaks through emerging technologies. There has been a variety of research in recent years aimed at further development of sensor-based technologies for leak detection. A key obstacle to retrofitting existing pipelines with leak detection technologies is the cost and risk of installing hardware, particularly those sensors that require excavation near the pipe. There are many advantages to employing leak detection systems that can leverage existing instrumentation access locations. One such technology may be negative-wave leak detection systems. Negative-wave technologies work by measuring dynamic pressure changes in the pipe. It should be noted that some negative-wave systems require line modifications to accommodate multiple transmitters. While such systems have been on the market for many years, there is insufficient data available about their performance under various pipeline operating conditions for widespread adoption.

In an effort to close many information gaps on the performance envelope of negative-wave technologies, a PRCI-funded field test was performed on a 41-kilometer segment of a 30-inch diameter heavy crude oil pipeline. Products from three suppliers were installed at either end of the test segment. Actual commodity withdrawals were conducted at a remote valve site approximately 21 kilometers into the segment during various operations to test the systems’ abilities to detect the withdrawals without direct user interaction. These test points included withdrawals during steady-state flowing, pump startup, and shutdown conditions.

Data were collected from each system to determine their abilities to detect leaks under various conditions, abilities to locate the leak, false alarm rates, and response times. This test provided significant insight into the performance of such systems over the range of conditions tested. The key focus of this paper is the approach for conducting such multi-vendor commodity withdrawals. This project required some unique considerations for its execution. Such considerations are also documented to provide input to others who are considering such a test.
Shallow Dents: Updates to the UKOPA Dent Management Strategy
Authors: Lockey Aaron , Palmer-Jones Roland , Jackson Neil , Ellis Roger
Published: December 2014

Pipelines can be dented, but shallow dents with depths less than 2% of the pipe diameter have only recently begun to be reported reliably by high resolution in-line geometry inspections. Most thin-walled onshore pipelines around the world are found to contain these shallow dents, many on welds of unknown toughness, or subject to severe pressure cycling.

Much of the existing guidance for dent management was published before such shallow dents were being reported, and did not necessarily consider them. Furthermore, recent failures in Canada have demonstrated that the existing guidance can be non-conservative when a shallow dent is combined with fatigue loading or other undetected damage.

The United Kingdom Onshore Pipeline Operators Association (UKOPA) is developing a strategy for the management of dents to provide guidance to operators based on published best practice. The aim of the work is to ensure that dents now identified but not sized by MFL inspection tools are appropriately inspected, investigated, assessed and repaired.

UKOPA’s methodology allows shallow dents to be screened and assessed without the requirement for numerous feature investigations. This management strategy is:

Stage 1: Use previously published UKOPA guidance on the prioritization of dents. This involves following a series of flow charts, leading the operator from dent discovery, through decisions affecting assessment and possible repair.

Stage 2: This Stage provides a series of criteria to indicate whether a weld is likely to be of sufficient toughness to withstand shallow denting, then gives a method to carry out an engineering assessment of a dent based on finite element analysis.

This paper presents the background and justification of ‘Stage 2’, and updates ‘Stage 1’. It includes a review of recent published work covering dents on welds, including analytical studies, finite element analyses, testing and failures. The results of this work by UKOPA will form an input to the planned updates to the Pipeline Defect Assessment Manual (PDAM).

The paper then applies the updated guidance to operational dent assessment problems provided by UKOPA members. Finally, an example of a dent assessment under the previous and updated guidance, including a finite element analysis, is given to illustrate how a shallow dent on a weld of unknown toughness may be re-categorized as not requiring repair.