bluuebunny/crossref_metadata_2025 huggingface dataset:
Buckling Resistance of Large Diameter Spiral Welded Linepipe
Authors: Zimmerman Tom , Timms Chris , Xie Jueren , Asante James
Published: December 2008

This paper contains the results of an experimental and analytical research program to determine the compressive buckling resistance of large-diameter, spiral-welded linepipe. Buckling resistance is important for pipe intended for service in Arctic, oil and gas pipeline systems, where pipes may be subjected to high bending strains caused by various ground movement events. The experimental work consisted of four full-scale tests of 30-inch (762 mm) diameter pipe subjected to various combinations of internal pressure, axial force and bending. The pipe specimens were fabricated using two material grades (X70 and X80) and two D/t ratios (82 and 48). Finite element analyses of the four tests were conducted to develop a better understanding of specimen behavior. The results suggest that spiral welded linepipe is as good as longitudinally welded line pipe in terms of buckling capacity. The spiral weld seam was in no way detrimental to the pipe performance.
Effectiveness of Web Based Pipeline Operator Training and Qualification Systems
Authors: Horon Barry , Hansen Peter
Published: December 2008

Managers of today’s pipeline companies are looking for effective training programs for pipeline operations and maintenance (O&M). One of the more significant reasons for the renewed interest in training has been the measures implemented by U.S. government regulators in response to recent pipeline accidents. These measures have included publication of enhanced pipeline safety standards, imposition of large fines for infractions, and even imprisonment for pipeline employees. In the meantime we’ve witnessed a proliferation of web-based learning management systems (LMS), some of which specifically target training for pipeline operations and maintenance. These “all in one” training systems promise much: 24/7 access from any Internet-enabled computer, more consistent and less expensive training, a self-paced learning environment, centralized training material, the potential for a multimedia learning experience, and easier management of qualification records. This paper explores reasons why pipeline managers should be cautious when considering web-based learning management systems as a complete training solution for their operations.
Modeling of Ethylene in Pipeline Leak Detection System
Authors: Bu¨chert Jakob
Published: December 2008

This paper describes experiences with an improved equation of state (EOS) for ethylene for an existing real time pipeline model. The main scope of the model is leak detection, batch, contaminant and pig tracking. Altogether the pipeline model includes transportation of batched liquid ethylene, ethane, propane, butane and natural gas liquids (NGL). The pipeline is approximately 1900 miles miles long and includes laterals, 33 pump stations, 9 injection/delivery stations and 5 propane terminals. Originally the model used a BWRS EOS for all the above products. At that time a number of false leak alarms were experienced related to pipeline sections containing ethylene. A case study was carried out, specifically for ethylene, to investigate the effect of replacing the BWRS EOS with a modified Helmholtz EOS. The study showed that replacing the EOS on average would improve determination of the ethylene densities by 1.6%–5.6% with an expected reduction in the alarm rate for ethylene cases by approximately 50%. As a result the modified Helmholtz EOS was implemented in the real time model. Results are presented to show the practical experience with the new EOS gained over the last years.
Remote Operations in Bolivia-Brazil Gas Pipeline - GASBOL
Authors: Borgli Felipe Schlemm , Longa Junior Mario Veiga , Nunes Ildemar Pinto
Published: December 2008

This technical paper has an objective to describe the remote operations of the Bolivia-Brazil gas pipeline and present how it is done in the Supervision and Control Center including new technologies normally used to operate remotely. The Bolivia-Brazil gas pipeline is the biggest pipeline in Latin America; the whole pipeline has 3,159 km length, where the most part of that is in the Brazilian ground of 2,593 km. TBG is a company that has the Brazilian trunk property and is responsible for its operations, which starts just at the Bolivian border. The pipeline started its operational activities in 1999 and was designed to operate with high technology and with the minimum field personal as possible. The pipeline has the maximum transport capacity of 30 million cubic meters per day. To reach this level is necessary to operate at the same time twelve compression stations along the pipeline and deliver gas for the customers in more than thirty-six-city-gates spread in five Brazilian states. From its Head Office in Rio de Janeiro, TBG controls remotely all of the pipeline’s operations along its entire length. It surveys the full extension of the pipeline 24 hours a day with two engineers, by satellite, using SCADA system (Supervisory Control and Data Acquisition software) and a plenty of online and offline simulation softwares including leak detection systems, pig monitoring, gas inventory management, look-ahead, predictive and trainer modules, thereby increasing operational reliability and improving decision-making process. Almost every operation is possible to be done by control engineers as like as starting-up turbines, increasing and decreasing compression rotations or even open or close valves. The technology VSAT (Very Small Aperture Terminal) and IP tunnels through the corporate WAN are both used to exchange data. The whole system now has more than 50,000 tags in real time database. Other important issue is that TBG doesn’t need any measurement staff in the field proceeding all the data acquisition. The whole measurement process is completely done at Supervision Control Room and at the same instant when data were collected the customer has the final certified volume in its hands.
Dent Management Program
Authors: McCoy Jackie , Ironside Scott
Published: December 2008

Enbridge Pipelines Inc. owns and operates the world’s longest hydrocarbon transmission system, which traverses across the varying geophysical landforms of Canada and the United States. These pipelines range in diameter from 12” to 48” and were constructed between 1950 and 2003. The wide range of pipe sizes, practices used for construction, and landforms traversed result in a very challenging Dent Management Program. Standards such as CSA Z662-99, ASME B31.4, and B31.8 provide a criterion for the selection of dents that require repair. Experience has shown that these standards do not identify all dents that have a possibility of failure due to leak or rupture. Enbridge initiated a project to study dents with BMT Fleet Technology of Kanata Ontario, this study determined that the dent geometry in addition to the depth to pipe diameter ratio affects the propensity that a dent will fail. Recent research and development by a group sponsored project lead by BMT Fleet technology on dent characterization has combined the pipeline’s cyclic pressure history with the shape of the dent to predict a time to failure. Enbridge combines these tools along with new insights from field excavations into its Dent Management Program. The Dent Management Program includes a series of prioritization’s to determine which sections of pipelines require detailed dent analysis. Typical prioritization criteria are rocky terrain, larger occurrence of third party damage, and history of numerous dents or failures. The detailed analysis utilizes the BMT Fleet “Dent Characterization Criteria” which was developed using their Finite Element Dent Assessment Model. This model considers the geometry of the dent, pipe material properties and historical pressure data to predict a time to failure for each dent. This time to failure prediction requires some additional engineering analysis depending on how close the parameters of the actual pipe are to what was validated with the model. This engineering analysis will determine which dents are selected for excavation and examination. This model has provided Enbridge with a tool to better manage its dent program, and this will be proposed as an option to improve the existing standards.
A Historical Case in the Bolivia-Brazil Natural Gas Pipeline: Slope on the Curriola River
Authors: Vasconcellos C. R. A. , Oliveira H. R. , Freitas J. C.
Published: December 2008

The Bolivia-Brazil Natural Gas Pipeline has 2.600 kilometers since Rio Grande City in Bolivia until Canoas City, in south Brazil. The pipeline crosses a lot of types of geological field and difficult topography. The south spread of the pipeline is the most interesting because of its hard topography combined with the variety of geological materials, such as, colluvium deposits and debris flow areas. Curriola River is located at kilometer 408, north part of Parana State. In this area, the pipeline crosses slopes of 40 degrees of inclination. The mounting was only possible making high cuts to assure the appropriated bendings to the pipe. The high cuts generated high volumes of soil that had no place to be deposited. The construction staff decided to put all the material above the right-of-way, in down part of the slope, near Curriola River. The construction created an artificial colluvium. As well as the most colluvium mass around the world, the Curriola material is a non-resistance material, composed with clay and little rock blocks, with a high porosity. Every year, during the raining seasons, the mass movements generate tension cracks. A superficial drainage system was built in order to prevent these movements but it’s not sufficient because the embankment is more than 5 meters high. Studies have been carried out since the start of the pipeline operation. The most difficult part of the work is the access to the area that makes the whole activity a battle. The first field investigation was conclude in January 2003, composed by SPT tests, piezometer installation and investigation wells. The second part of the story will be composed by inclinometer and strain gauges installation and monitoring, together with laboratory tests with samples of the field. The aim of this paper is to present the site characterization of the Curriola River Slope, together with all the investigation made, including state of stress field, and residual stresses assessment, in order to supply the studies with condensed information for the slope stabilization and gas pipeline integrity.
Determination of Critical Hydrogen Curves From Slow Bend Tests
Authors: Pusseogda L. N. , Dinovitzer A. , Horsley D.
Published: December 2008

Recent trends in the pipeline industry are towards the use of high strength steels. As steel strength increases, the delayed hydrogen cracking propensity in the welds also increases. As welding is often completed during winter months, the cold temperatures must be considered in determining joining procedures that will avoid delayed hydrogen cracking. The Graville/BMT Fleet Technology Limited hydrogen diffusion and cracking models have been used successfully in the past to predict delayed cracking and to demonstrate how changes implemented in the welding procedure can minimize the risk of cracking. The two capabilities, hydrogen diffusion and cracking assessment, can be applied to the case of X100 pipe as well, provided the hydrogen diffusivity and the hydrogen cracking susceptibility curves are established for the materials of interest. These two parameters, the hydrogen diffusivity and the hydrogen cracking susceptibility curves are developed to examine the hydrogen cracking susceptibility of SMAW and GMAW welds in X100 pipe, and are the focus of the paper.
Experimental Tests and Numerical Simulation in a Reduced Model in a Pipeline With ZIG-ZAG Geometry: A Parametric Study
Authors: Poiate Junior Edgard , Seixas da Rocha Renato , Maia da Costa A´lvaro , Barbosa Guimara˜es Giuseppe , Amaral Cla´udio dos Santos , de Souza Pablo Furtado
Published: December 2008

In January 2000, PETROBRAS faced a leakage of heavy heated MF380 oil from a 0.406m pipeline in the Guanabara Bay. When interacting with the soil, the thermal structural buckling of the pipeline induced the rupture of the pipeline wall causing the oil to leak. In order to overcome this undesired phenomenon, PETROBRAS studied several new pipeline alternatives. As a result of these studies, a “ZIG-ZAG” geometry pipeline named PE-3 was adopted. Given that the oil industry applications of this kind of concept have been very few and in soil conditions different from the ones in the Guanabara Bay, a very sophisticated procedure was developed including the simulation the thermal mechanical interactions between the soil and the pipeline structure. Computer modeling was carried out using the finite element method considering the soil, the pipeline non-linear material behavior and the finite displacements. In order to validate the numerical modeling, an experimental test was carried out in a reduced model with physics similar to a ZIG-ZAG geometry pipeline (PE-3). The numerical and experimental results match and have a fine conformity. After validation of the models, numerical and experimental parametric studies were completed with various angles and wavelengths of ZIG-ZAG to evaluate the conception of the PE-3 pipeline.
An Integrated Approach to Pipeline Buoyancy Control and Implementation
Authors: Thomas Lance N. , Henderson James
Published: December 2008

A case study approach clearly demonstrates how to integrate various investigative methods with design, procurement, contracting and construction strategies to significantly reduce life cycle costs for a recently constructed operating pipeline. Emergent strategies based on lessons learned throughout the process are presented based on an after construction review.
Validity of the LAPA Method for Assessment of Defects Reported by In-Line Inspection Tools
Authors: Fletcher Richard , Fenyvesi Louis
Published: December 2008

Over recent years, RSTRENG has gained acceptance as a reliable method of assessing the effect of pipeline corrosion defects, while reducing the conservatism inherent in some of the alternative assessment models. The Length Adaptive Pressure Assessment (LAPA) algorithm has been developed to apply an adaptation of the RSTRENG methodology directly to the results of a magnetic in-line inspection. Adoption of the LAPA technique offers substantial accuracy and efficiency benefits over the more conventional processes, but the industry requires confirmation of the method’s validity before it can take advantage of these. The paper will describe the LAPA validation work performed by PII, and independent validation undertaken by TransCanada Pipelines and other pipeline operators. The independent validation took the form of a comparison of LAPA-based burst pressure calculations with RSTRENG calculations based on direct infield measurements of the defect profile. TransCanada also performed a series of burst tests to quantify the accuracy of the LAPA calculations.
12 Steps to Effective in the Ditch NDE
Authors: Filiatrault Andre , Skinner Ian
Published: December 2008

New pipeline integrity regulations for onshore pipelines in North America are now in place from the DOT (Department of Transportation). This has resulted in time critical obligations for operators to ensure compliance. The requirement for operators to “effect discovery” of critical defects has placed greater emphasis on the ability to conduct in-field integrity assessments while the ditch is still open. This paper describes the in the ditch pipeline integrity services philosophy and techniques suggested necessary to comply with regulations. These techniques, in conjunction with In-line Inspection (ILI) findings and integrity evaluation assessments allow optimization of in the ditch defect assessment and repair decisions.
Quantitative Pipeline Risk Assessment and Maintenance Optimization
Authors: Wickenhauser Patrick L. , Playdon David K.
Published: December 2008

The quantitative risk assessment tool was used to calculate the failure rates, failure consequences and risk levels along the pipeline. Safety risk was characterized by the individual risk ratio, which was defined as the maximum individual risk associated with a given segment divided by the tolerable individual risk. Tolerable individual risk values were defined as a function of population density following the approach developed by MIACC and the UK HSE. Financial risk was expressed in dollars per km-year and included a dollar equivalent for public perception. The recommended maintenance plan was defined as the minimum cost option that achieved a tolerable safety risk. The first step in developing the plan was to identify all segments that do not meet tolerable risk criteria (i.e., segments with an individual risk ratio greater than 1). For each of these segments a number of potential maintenance scenarios that address the dominant failure threats were selected. A cost optimization analysis was then carried out in which the total expected cost associated with each maintenance option was calculated as the sum of implementing the option plus the corresponding financial risk component, amortized over the inspection interval. This analysis was used to identify the minimum cost alternative that meets the individual risk constraint. Outcomes of the analysis included the best maintenance option (e.g., inline inspection, hydrostatic test) and the optimal time interval for segment re-evaluation.
Parameter Optimization in the Design of Fuel Transmission System
Authors: Mei Anhua , Aung Ken
Published: December 2008

This paper presents a methodology to construct an optimum model based on the Present Worth of Uniform Series of Amount (PWUSA) method. This paper uses the design of a gas pipeline for a power plant that recovers work at the destination as a case study. The relationship of system parameters has been developed by thermodynamics principles. The objective function is construct by combining cost of each component in the system. The main goal of the paper is to minimize the total cost of the system by optimizing the design parameters. The paper gives the detail procedure involved in minimizing the total cost of the system using MathCAD software package. The results show that MathCAD software provides a fast and easy way to conduct optimization of practical engineering design problems.
Development and Application of Large Three-Way Hot Tapping Fittings
Authors: Jarvis William Alfons
Published: December 2008

Background on the development and application of high pressure “large branch ratio” three way tee style hot tapping and plugging fittings on large diameter (16”–54”) pipelines and pressure piping systems in Canada. Examines the limitations and problems in current design codes, for large ratio branch connections, and the good engineering practiced applied based on simple shell finite element analysis.
Local Strain Accumulation in Pipeline Girth Welds
Authors: Mohr William , Gordon Robin , Smith Robert
Published: December 2008

The majority of existing pipeline design codes are stress based and provide limited guidance on the design and assessment of pipelines that may experience high local strains in service. High strains can occur in service due to ground movement, bending over an unsupported span and seismic loading. In such cases pipelines should be designed based on strain capacity. The rigors of strain-based analyses pose a number of challenges, particularly related to pipeline girth welds and general material behavior. This paper presents a summary of an ongoing multi-year project co-funded by the US Minerals Management Service (MMS) and US Dept of Transportation (DOT) to develop design and assessment guidelines for pipelines that may experience high strains in service. Specific topics to be addressed by the project include: • Parent Pipe specifications (Y/T limits, stress-strain behavior, material toughness, etc.); • Welding specifications (joint design, joint geometry, weld strength mismatch, etc.); • Engineering Critical Assessment (ECA) Methods for strain based loading; • Validation test methods to verify pipeline performance (criteria for full-scale testing).
The Role of Soil Data in Pipeline Integrity
Authors: Marr James E. , Bates Neil , Portelance David , Farthing Scott
Published: December 2008

Since the early 20th century, researchers and engineers have been using soils information to address corrosion issues on buried metallic materials. While this area of research was quite active from the 1920’s to the 1950’s, soils related corrosion pipeline research was declining until the mid eighties. For the non-soil scientist this area is complex and disruptive since there is usually no easy equation or consistent answer from buried point to buried point. Historically, the pipeline industry has developed coating systems that effectively place a barrier between the soil environment and the pipe surface. Over time, these coatings can deteriorate to such a level that the environment can either migrate through the coating or come in direct contact with the pipe surface. The second level of protection used in the defense of the pipe from the environment is the cathodic protection (CP) system. These systems can also deteriorate, but they can be monitored through measurement techniques at a given interval. The CP system can provide an adequate level of protection, thus minimizing potential pipeline integrity threats such as external corrosion and stress corrosion cracking. This paper will present a historical overview of the use of soils and soil survey information and will provide an overview our experiences related to the use of data effecting external corrosion and stress corrosion cracking of line pipe steels.
Data Management for Integrity Decision Support
Authors: Wiegele Ed , Nemeth David , Kariyawasam Shahani , Clouston Stuart
Published: December 2008

Within most pipeline organizations, maintenance and other facility departments use a range of separate data sources and applications to manage the integrity, maintenance and safety of their pipelines. These databases represent a significant investment over many years and are an integral part of day-to-day operations. It is evident that integration of data into a single, coherent data management system can provide significant benefits. However, the cost of implementing entirely new systems — with intensive data capture programs — is difficult to justify given the earlier investments. As a result, dedicated risk management software using static and separately maintained data is often used as a quick, low cost alternative to meet regulatory compliance commitments. Experience has shown that, with the right technology and an understanding of the specific needs of an organisation, a phased approach to integrated data management can be achieved at minimum initial cost by exploiting legacy data. This provides a low cost yet scalable solution that can grow with the changing needs of the business. In addition to the benefits of legacy data integration, this paper presents an insight into the additional benefits of technologies for distributed data access to provide simple, process-focussed reporting tools. The key role of data management in risk assessment and consequent integrity decision support process is discussed.
Continuous Improvement Based on Learning Capacity of Petroleum Industry
Authors: Filho Cid Alledi , Cozendey Silva Eliana Napolea˜o , Rodriguez Martius Vicente R. , Quelhas Osvaldo L. Gonc¸alves
Published: December 2008

Oil industry, as well as all organizations, is facing challenges of a new paradigm: the incessant endeavors of continuous improvement. It is calling attention of all organizations that seek business sustainability. Improvement programs proliferate and aim to qualify the organization to gain new victories. However, how to implement continuous improvement in oil industry? Where should it begin? How to proceed? How to guarantee that the accomplished efforts will lead to positive results for the organization? Knowledge Management has been one of the main issues in several publications, and many authors affirm that knowledge is the key for organizations’ success. According to Garvin, organizations see their improvement plans fail because most of them have not learnt the basic lesson: to improve continuously, organizations need first to know how to learn. There is no improvement without learning. And a company that learns is not quickly built. It is necessary planning, perseverance, commitment and processes which accumulate results. Occidental managers, according to Nonaka, have difficulty to understand the symbolism of Japanese slogans as tools to create a learning atmosphere. The authors of this paper have developed a visual methodology, based on symbolism and key words, which is intended to make easier the assimilation of the concepts of knowledge management, more specifically, the concepts of Garvin, Nonaka and Takeuchi, for use and improvement of the capacity of an organization “learn how to learn”, seeking the construction of the necessary learning atmosphere.
Smart Pig Defect Tolerances: Quantifying the Benefits of Standard and High Resolution Pigs
Authors: Westwood Stephen , Hopkins Phil
Published: December 2008

Smart pigs are used as part of an integrity management plan for oil and gas pipelines to detect metal loss defects. The pigs do not measure the defects: they collect signals from on board equipment and these signals are later analysed. Signal analysis is complex; consequently, defect sizing tolerances and confidence levels can be difficult to determine and apply in practice. They have a major effect when assessing the significance of the defect, and when calculating corrosion growth rates from the results of multiple inspections over time. This paper describes how defect sizing tolerances and confidence levels are obtained by pigging companies, and compares standard and high resolution pigs. Probability theory is used by the authors to estimate the likelihood that a defect is smaller or deeper than the reported (by the pig) value for both standard and high resolution tools. The paper also shows how these tolerances can be included in defect failure assessment and the results of multiple pig runs.
Weldability of High Strength and Enhanced Hardenability Steels
Authors: Wang Yong-Yi , Rapp Steve
Published: December 2008

Since the 1970s, the development of high-strength pipeline steels has followed the route of progressively reduced hardenability through lower carbon and alloying element contents. Microalloying, controlled rolling (CR), and thermo-mechanical controlled processing (TMCP) have been used extensively to achieve the high-strength and other material property requirements despite the trend towards lower carbon content. The primary driving force behind the evolution of these alloying and processing strategies stems from the concerns over the weldability, particularly the hydrogen assisted cracking (HAC), at ever-increasing strength levels. In doing so, the adverse effects of this steel making philosophy on the structural integrity and steel manufacturing cost have become more pronounced. The steels made using those processes can exhibit high yield to tensile ratio (low strain hardening), low uniform elongation, HAZ softening, and splitting; all of which tend to have detrimental effects on pipeline integrity. The objective of the work described here was to evaluate alternate steels with enhanced hardenability and identifying those that would have a potential to (1) meet the high strength/high toughness requirement but without the adverse effects of the early trial heats of microalloyed TMCP X80 and X100 linepipe steels, and (2) exhibit sufficient resistance to HAC. Three enhanced hardenability steels were evaluated through a full range of mechanical tests, metallurgical examination, and weldability tests. Although none of the three alternative steels met the full requirements of X100 linepipe material, one of them showed good promise in meeting the X100 linepipe material requirements.
Probabilistic Design Methodology to Mitigate Ice Gouge Hazards for Offshore Pipelines
Authors: Kenny Shawn , Bruce Jim , King Tony , McKenna Richard , Nobahar Arash , Phillips Ryan
Published: December 2008

For offshore pipelines located in ice environments, the mitigation of ice gouge hazards presents a significant technical challenge. A traditional strategy is to establish minimum burial depth requirements that meet technical and economic criteria. A probabilistic based approach to optimize burial depth requirements based on equivalent stress and compressive strain limit state criteria is presented. The basic methodology is to define ice gouge hazards on a statistical basis, to develop numerical algorithms that model ice gouge mechanisms and pipeline/soil interaction events, to define failure criteria, limit states and target reliability levels and to conduct a probabilistic assessment of pipeline burial depth requirements. Application of the probabilistic design methodology for a generic pipeline design scenario subject to ice gouge hazards is presented. Implications on pipeline design and future applied research initiatives are discussed.
Regulation of the Integrity of Gas Transmission Pipelines by the Office of Pipeline Safety
Authors: Barrett Zach , Israni Mike , Wiese Jeff , Wood Paul
Published: December 2008

In December of 2003 the US Department of Transportation’s Office of Pipeline Safety (OPS) published a final rule for integrity management of gas transmission pipelines. As in the earlier rule for integrity management of hazardous liquid pipeline, OPS had four fundamental objectives: 1) to increase the level of integrity assessments (i.e., in-line inspection, pressure testing or direct assessment) for pipelines that can affect high consequence areas; 2) to improve operator integrity management systems; 3) to improve government oversight of operator integrity management programs; and 4) to improve public assurance in pipeline safety. This paper describes the process leading to the rule, the primary features of the rule, and the current thinking regarding OPS expectations for inspecting against provisions of the rule. While the basic structure of the IM rule for gas transmission pipelines is very similar to that of the hazardous liquid rule, the gas rule has several distinctions that are discussed in this paper.
A Robust Approach to Pipeline Integrity Management Using Direct Assessment Based on Structural Reliability Analysis
Authors: McCallum Marcus , Francis Andrew , Illson Tim , McQueen Mark , Scott Mike , Clarke Steve
Published: December 2008

Approximately 1450 km (900 miles) of a 4020-km (2500 mile) natural gas pipeline system operated by Crosstex Energy Service L.P in Texas are subject to the Texas Railroad Commission’s (TRRC) integrity management rules. Consequently, in preparation for the construction of an extensive and robust integrity management program, Crosstex commissioned Advantica to assist in the development and application of a pilot study on a 13.4 km (8.3 mile) section of a 14” pipeline. The purpose of the study, which is based on Structural Reliability Analysis (SRA), was to compare the level of integrity that could be inferred from the use of Direct Assessment (DA) techniques with the level that could be inferred from ILI results. Based on a preliminary assessment of available data, the study identified both external and internal corrosion as potential threats to integrity. SRA was used in conjunction with ‘Bayesian Updating’ to determine the probability of pipe failure due to external corrosion, taking account of results from above-ground measurements and a number of bell-hole excavations. The above-ground survey techniques utilized included Close Interval Survey (CIS) and Direct Current Voltage Gradient (DCVG). A similar approach was adopted to address the threat due to internal corrosion, but hydraulic modelling was substituted for the above-ground measurements. A third study based on SRA was used to determine the combined probability of failure due to both internal and external corrosion taking account of ILI results. The outcome of the analyses demonstrated that the level of integrity that could be inferred from the use of Crosstex’ DA methodology was similar to that which could be inferred from the use of ILI. The results were presented to the TRRC for review and approval. This paper gives a detailed description of the SRA based methodology that was employed by Crosstex and presents the results that clearly demonstrate the comparability of ILI and DA for the purpose of integrity management.
Two Phase Flow: Accounting for the Presence of Liquids in Gas Pipeline Design
Authors: Asante Ben
Published: December 2008

Multiphase flow of gas and low loads of liquids occurs frequently in natural gas gathering and transmission pipelines for both onshore and offshore operations. Literature and experimental investigations indicate that dispersed droplet and stratified flow patterns are obtained when gas and small quantities of liquids flow concurrently in a pipe. Very few correlations exist for the prediction of holdup and pressure drop for these systems and fewer still give satisfactory results. Experimental studies for air-oil and airwater systems flowing through small diameter plastic and steel horizontal pipes ranging in size from 1-inch to 3-inches were performed. The experiments were carried out at the multiphase flow laboratories of Imperial College in London and the University of Calgary in Canada. Data from actual operating gas pipeline systems transporting small amounts of hydrocarbon liquids were also evaluated. Based on the experimental results and the operating data, two approaches for modeling these systems are proposed: 1) A homogeneous approach for very low liquid loads (holdups up to 0.005), typical in gas transmission systems. A friction factor correlation based on the holdup has been developed for this flow regime. 2) A mechanistic stratified two-phase approach for higher liquid loads (holdups greater than 0.005) usually found in gas gathering systems with consideration given to: a) The reduction in the available flow area and extent of wetting of the pipe perimeter by the liquid film. The gas/liquid interface was observed to be either flat or curved. b) The interfacial friction factor between the liquid film and the gas. A new correlation based on the liquid and gas Reynolds numbers as well as the film thickens and hold up has been developed. This correlation has been successfully tested against both experimental and actual pipeline operating data.
A Practical Implementation of Pressure Transient Analysis in Leak Localization in Pipelines
Authors: Warda H. A. , Adam I. G. , Rashad A. B.
Published: December 2008

In the present study, a more realistic approach for using pressure transient analysis in leak detection and localization is proposed. In a previous publication [1] by the authors, the feasibility of using pressure transients, generated by full closure of a downstream solenoid control ball valve, in leak detection and localization is investigated. The main shortcoming of using the full closure of a downstream valve is the very high pressure rise that may reach 14 times the operating pressure. Also, full valve closure yields to discontinue the whole pipeline flow. In the present paper, a controlled partial downstream or upstream valve closure is used as a mean of generating pressure transients to overcome the above drawbacks. The percentage of the valve closure is controlled to reduce the pipeline flow rate by 20–80%. Pressure transients generated by a partial valve closure are investigated experimentally and numerically. The experimental setup consists of a 60 m long and 25.4 mm internal diameter PVC pipelines connecting two tanks. Leaks are simulated at different locations along the pipeline to investigate the effect of leak positions. The pressure time history is recorded using piezoelectric pressure transducers located at five equidistance points along the pipeline connected to a Data Acquisition System. Experiments are carried out for different leak quantities ranging from 2% to 20% of the pipe flow rate. The numerical model accounts for complex pipe characteristics, such as unsteady friction and viscoelastic behavior of pipe walls. The leak is treated as a flow through an orifice of prescribed size. The numerical model is experimentally verified to insure the capability of the model in accounting for unsteady and viscoelastic complex phenomena and efficiently simulating pressure transients in the presence of a leak.
New Approaches to the Automated Analysis of Ultrasonic In-Line Inspection Data
Authors: Willems H. , Reber K. , Zo¨llner M. , Ziegenmeyer M.
Published: December 2008

Inline inspection of pipelines by means of intelligent pigs usually results in large amounts of data that are analyzed offline by human experts. In order to increase the reliability of the data analysis process as well as to speed up analysis times methods of artificial intelligence such as neural networks have been used in the past with more or less success. The basic requirement for any technique to be used in practice is that no relevant features should be overlooked while keeping the false call rate as low as possible. For the task of automated analysis of in-line inspection data obtained from ultrasonic metal loss inspections, we have developed a two-stage approach. In a first step (called boxing), any defect candidates exceeding the specified size limits are recognized and described by a surrounding box. In the second step, all boxes from step 1 are analyzed yielding basically a relevant/non relevant decision. Each feature considered to be relevant is then classified according to a given set of feature classes. In order to efficiently perform step 2, we have adapted the SVM (support vector machines) algorithm which offers some important advantages compared to, for example, neural networks. We describe the approach applied, and examples as obtained from in-line inspection data are presented.
Weld Microstructure and Hardness Prediction for In-Service Hot-Tap Welds
Authors: Cheng Wentao , Wang Yong-Yi , Amend William , Swatzel Jim
Published: December 2008

Welding onto an in-service pipeline is frequently required to repair damaged areas and for system modifications. There are often significant economic and environmental incentives to perform in-service welding, including the ability to maintain operations during welding and to avoid venting the contents to the atmosphere. Welds made onto in-service pipelines tend to cool at an accelerated rate. These welds are likely to have high heat-affected zone (HAZ) hardness which increases their susceptibility to hydrogen cracking. Accurate prediction of HAZ hardness is critical in developing successful welding procedures for in-service hot-tap welds. The present PRCI thermal analysis software for hot-tap welding uses an empirical-formula-based HAZ hardness prediction procedure. This paper describes an effort funded by PRCI to produce a significantly improved HAZ hardness prediction procedure over the procedure in the current PRCI thermal analysis software. A markedly improved hardness prediction procedure was developed and systematically validated using extensive experimental data of actual welds. The underlying hardness calculation algorithms were based on the proven state-of-the-art phase transformation models. Although on the average the procedure under-predicts the measured hardness by a small amount, the new hardness prediction procedure is a significant improvement in overall accuracy over the procedure in the current PRCI thermal analysis software. The procedure developed here lays the foundation for a much more accurate hardness prediction module in the future version of the PRCI thermal analysis software.
The Respective Merit of Gas Turbine vs Electric Drive for Pipeline Turbocompressors
Authors: Jordan Klaus , Walter Peter , Emde Axel , Comberg Christoph
Published: December 2008

The paper briefly reviews the technology, gas turbine versus high speed electric drive, which represents two very different solutions for natural gas pipeline or storage compressor drive applications. The technical and economic merits of the competing drive systems have to be considered for each individual project. Traditionally, gas turbines have been the prime drivers for compressor trains, especially in Europe whereas in North America gas engine driven reciprocating compressors are also very common. With the liberalization of the electric power market and tighter environmental restrictions regarding local emissions, high frequency electric motor drivers became a competitive alternative profiting by decreased costs for the electricity infrastructure and the power supply, thus lowering the investment and operational costs. Gas turbines in compliance with the latest emission regulations will maintain their predominant role in natural gas pipeline and storage applications, especially in non-residential and remote areas.
Methods for Assessing Risks at Above Ground Installations
Authors: Acton M. R. , Baldwin P. J. , Cleaver R. P. , McCollum D. J.
Published: December 2008

This paper describes a package of computer models that has been developed to assess the risks from gas releases at above ground installations associated with natural gas transmission pipelines. The package can be applied to compressor stations (containing compressor enclosures and associated gas treatment equipment) and pressure reduction stations, through to single block valve installations. It has been designed for used by safety engineers in performing quantified risk and hazard analysis, as required to meet regulatory requirements, such as the COMAH Regulations or the DSEAR Regulations in the UK. It can also be used in the design stage of projects to support decisions related to site layout for example. The package contains a range of mathematical models to assess the consequences of accidental releases of gas (including outflow, dispersion, gas accumulation, fire, explosion and thermal and overpressure response), validated by data from large and full scale experiments. The individual models are linked in a logical manner constructed around a series of “knowledge bases” that provide a defined structure to allow a wide range of different scenarios to be assessed. The predictions of the consequences arising from various scenarios can be combined with estimates of the frequency of initiating events (based on industry statistics where available, or using predictive models), in risk calculation routines which sum the outcomes for the different scenarios to calculate individual and/or societal risk. To illustrate the use of the techniques, examples of their application are given. In particular, it is shown how the risks arising from releases from high pressure vessels or in confined volumes, such as compressor enclosures, can be evaluated.
AC Corrosion: Mechanism and Proposed Model
Authors: Yunovich Mark , Thompson Neil G.
Published: December 2008

Corrosion caused by the discharge of 60 Hz AC current from a pipeline in a high voltage AC (HVAC) corridor has been discussed and studied over the past 20 or more years. More recent studies in Europe have specifically addressed these corrosion issues following several failures attributed to the presence of AC discharge from the pipeline. Very few corrosion failures in North America have been specifically attributed to what is termed AC-enhanced corrosion (ACEC). One missing area of research is well-controlled laboratory experiments in soil environments. This study proposed a mechanism of ACEC that is based on conventional electrochemistry using the same equivalent analog circuits used to discuss other corrosion processes. It was shown that only a small amount of the 60 Hz AC current discharge passes through the resistive component of the equivalent circuit, which results in corrosion (metal loss) reactions. The AC current passing through this resistive component produces both anodic and cathodic polarization shift (sine wave dependent) resulting in a net increase in the average corrosion rate as compared to the free-corrosion rate. The proposed model for ACEC does not invoke any new electrochemical concepts and is based on the conventional (DC) treatment of the corrosion processes; the model excludes treatment of cases with imposed cathodic protection current. The amount of ACEC is dependent on the magnitude of AC current that passes through the resistive component of the parallel resistive-capacitive electrochemical interface. ACEC is characterized by the rapid formation of a diffusion controlled (Warburg) process for corrosion in soils. Although diffusion controlled, the overall impedance decreases as the total AC current increases. The model suggests that AC currents (60Hz) cause anodic (positive) polarization shifts during the positive portion of the imposed AC sinewave along with cathodic polarization shifts in the negative portion of the AC sinewave; the net result is an increase in the average oxidation (metal loss) current as compared to the free-corrosion condition. The proposed model for the ACEC mechanism showed excellent correlation with the experimental results. The research work was made possible by the funding from PRCInternational.
Inspection of Hollow Sucker Rod by Using Guided Wave
Authors: Li Longtao , He Cunfu , Wu Bin , Zheng Jingyu , Li Ying
Published: December 2008

Based on cylindrical guided wave technology, a new designed piezoelectric ring was presented here and it was put on the cross section of the hollow sucker rod’s end to excite or receive guided waves in the hollow sucker rod. By selecting and exciting specific guided mode at a given frequency, two artificial cracks (20 mm × 1 mm × 0.5 mm and 20 mm × 1mm × 1mm), which located on the hollow sucker rod, can be found in time domain. Tie-ins in the hollow sucker rod increase the complexity of analyzing the received signals. An alternative method presented here is that a fast guide mode was selected and excited at a specific frequency. Then, the echo from cracks will appear the front of the echo from tie-ins of the hollow sucker rod in the received signals. Some conclusions proved that the new designed piezoelectric ring was more effective than previous piezoelectric transducers and it is feasible to utilize cylindrical guided wave to achieve nondestructive inspection on hollow sucker rod.
The Prediction and Enhancement of UOE-DSAW Collapse Resistance for Deepwater Linepipe
Authors: Fryer Mark , Tait Peter , Kyriakides Stelios , Timms Chris , DeGeer Duane
Published: December 2008

With the increasing development of oil and gas reserves in water depths greater than 1500 m, linepipe used for deepwater and ultra-deepwater applications will require enhanced resistance to hydrostatic collapse. To support this need, Corus Tubes has been investigating methods by which increases in UOE linepipe collapse strength can be achieved. In particular, it has been theorised that modifications to the UOE manufacturing process can provide the necessary collapse strength enhancements. Pipe production trials were conducted focusing on the effect of processing parameters during UOE linepipe production, and in addition low temperature heat treatment was used to assess its effect. Full-scale collapse tests were then performed on the resulting linepipe specimens to validate the increase in collapse strength. The results of this work have demonstrated the beneficial effect of a modified UOE manufacturing approach on linepipe collapse resistance. This paper summarizes the work performed, quantifies the increase in collapse strength, and compares the test results to collapse equations found in offshore pipeline standards. It is also demonstrated that the UOE fabrication factor of 0.85 in the DNV offshore pipeline code (DNV OS-F101) may be considered to be over conservative, when linepipe is manufactured using the modified approach summarized herein.