bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure Mechanisms of Pipelines Subjected to Loss of Support Under Deep Burial Conditions
Authors: Costa Yuri D. , Zornberg Jorge G. , Bueno Benedito S. , Costa Carina L.
Published: December 2008

This paper investigates the failure mechanisms of pipelines subjected to a localized loss of support. An experimental program was conducted, which consisted of a series of four centrifuge model tests containing an aluminum tube embedded in a pure dry sand backfill that was placed over an underlying rectangular rigid base moving downwards during the test. All models were built taking advantage of the longitudinal symmetry of the problem. The prototype pipe had a diameter (D) of 1.1 m and a soil cover height of about 5 D, characterizing deep burial conditions. Failure patterns were observed within a vertical section comprising the central axis of the pipe and also in four distinct vertical transverse sections along the length of the pipe in the region of ground loss. The influence of pipe stiffness and backfill density on the behavior of the system was assessed. The transverse sections showed fully developed slip surfaces starting in the vicinity of the edge of the void towards the adjacent soil mass. The mode of failure of the flexible pipes took the form of a severe deformation at the region of the shoulder and a reversal of curvature at the invert due to over-deflection. This situation was more critical in the central section. The damage experienced by the flexible pipes was noticeably more pronounced when using the looser backfill, whereas only negligible deflections were observed when using the denser backfill. The experimental results were compared with analytical predictions, which showed to be highly unconservative for the case loose backfill.
Analysis of US Liquid and Gas Incident Data
Authors: Kolovich Carolyn E. , Haines Harvey
Published: December 2008

This document presents an analysis of “Reportable Incidents” on gas transmission and gathering pipelines in the U.S. during the 16-year period from 1985 through 2000 and on liquid pipelines in the U.S. from 1986 through 2000. The reporting format changed after 1985 for the liquid incidents. The purposes of this analysis are to improve the pipeline industry’s understanding of the causes of incidents and their consequences, to monitor trends that may indicate the need for action, and to diagnose potential problems in the database that might be general in nature and to identify areas for potential improvement in the data collection process that can help pipelines address the issue of risk management. After third party, accounting for 27.6 percent of all gas incidents, the next four leading causes of reportable incidents are: internal corrosion 12.8 percent, external corrosion 9.9 percent, incorrect operation 7.0 percent, and miscellaneous 6.8 percent. For the liquid incidents, third party incidents are also the leading cause at 20.5 percent. External corrosion was responsible for 18.5 percent, followed by miscellaneous incidents at 9.9 percent, incorrect operations at 8.6 percent and internal corrosion at 6.2 percent. For natural gas pipelines, it appears the number of third party and external corrosion incidents are decreasing while the number of internal corrosion incidents is increasing slightly. For liquid pipelines, the numbers of incidents attributable to third party damage and internal corrosion have remained relatively constant, while there has been a slight decrease in incidents caused by external corrosion. The consequences of incidents are of great importance in terms of assessing their impact on public safety. The consequences of pipeline failures are expressed in the incident reports in terms of fatalities, injuries, and property damage.
A Petroleum Pipelines Leakage Monitoring System
Authors: Li Zhuang , Jin Shijiu , Wang Likun , Zhou Yan
Published: December 2008

The petroleum leakage has been a serious problem these years in China. The leakage, mostly caused by human destruction, lasting a short time with a large amount of loss, is not only an economic loss for the petroleum company, but environmental pollution, a public issue. Thus a monitoring system, which can identify the leakage and locate the leak point in real time, is required. One of the challenges is the sensitivity of the system. The system is expected to respond quickly to locate the point so that the security personnel can find and mend the orifice in time. Another challenge is the accuracy of the locating result. Because of the features of Chinese petroleum: high viscosity, high wax content and high freezing point, the sound wave speed in the oil is not a constant along the pipeline and the leak point calculated by the traditional negative pressure wave method are invalid. In this paper, a modified negative pressure wave method was put forward according to the variation of the wave speed. A wavelet-based algorithm applied to calculate the leak point gives fairly satisfied results. The data acquisition, signal processing and the structure of the pipeline leakage monitoring system (PLMS) were analyzed. The system has played a big role on the pipeline network in Shengli Oil Field and long pipelines of East China Oil Bureau.
Fault Rupture Assessments for High-Pressure Pipelines in the Southern San Francisco Bay Area, California
Authors: Kelson Keith I. , Hitchcock Christopher S. , Baldwin John N. , Hart James D. , Gamble James C. , Lee Chih-Hung , Dauby Frank
Published: December 2008

The San Andreas, Hayward, and Calaveras faults are major active faults that traverse the San Francisco Bay area in northern California, and may produce surface rupture during large earthquakes. We assessed the entire Pacific Gas & Electric Company natural gas transmission system in northern California, and identified several locations where primary pipelines cross these faults. The goal of this effort was to develop reasonable measures for mitigating fault-rupture hazards during the occurrence of various earthquake scenarios. Because fault creep (e.g., slow, progressive movement in the absence of large earthquakes) occurs at the pipeline fault crossings, we developed an innovative approach that accounts for the reduction in expected surface displacement, as a result of fault creep, during a large earthquake. In addition, we used recently developed data on the distribution of displacement across fault zones to provide likely scenarios of the seismic demand on each pipeline. Our overall approach involves (1) identifying primary, high-hazard fault crossings throughout the pipeline system, (2) delineating the location, width, and orientation of the active fault zone at specific fault-crossing sites, (3) characterizing the likely amount, direction, and distribution of expected surface fault displacement at these sites, (4) evaluating geotechnical soil conditions at the fault crossings, (5) modeling pipeline response, and (6) developing mitigation measures. At specific fault crossings, we documented fault locations, widths, and orientations on the basis of detailed field mapping and exploratory trenching. We estimated fault displacements based on expected earthquake magnitude, and then adjusted these values to account for the effects of fault creep at the ground surface. Fault creep decreases the amount of expected surface fault rupture, such that sites having high creep rates are expected to experience proportionally less surface displacement during a large earthquake. Lastly, we modeled the expected amount of surface offset to reflect the distribution of offset across the fault zone, based on data from historical surface ruptures throughout the world. Where specific fault crossings contain a single primary fault strand, we estimated that 85% of the total surface offset occurs on the main fault and the remainder occurs as secondary deformation. At sites where the pipeline crosses multiple active fault strands in a broad zone, we consider complex rupture distributions. Using this approach yields realistic, appropriately conservative estimates of surface displacement for assessing seismic demands on the pipelines.
The Evaluation of Failure Pressure for Corrosion Defects Within Girth or Seam Weld in Transmission Pipelines
Authors: Kim Young-pyo , Kim Woo-sik , Lee Young-kwang , Oh Kyu-hwan
Published: December 2008

The failure assessment for corroded pipeline has been considered with the burst test and the finite element analysis. The burst tests were conducted on 762mm diameter, 17.5mm wall thickness and API 5L X65 pipe that contained specially manufactured rectangular corrosion defect. The failure pressures for corroded pipeline have been measured by burst testing and classified with respect to corrosion sizes and corroded regions — the body, the girth weld and the seam weld of pipe. Finite element analysis was carried out to derive failure criteria of corrosion defect within the body, the girth weld and the seam weld of the pipe. A series of finite element analyses were performed to obtain a limit load solution for corrosion defects on the basis of burst test. As a result, the criteria for failure assessment of corrosion defect within the body, the girth weld and the seam weld of API 5L X65 gas pipeline were proposed.
In-Line Stress Measurement by the Continuous Barkhausen Method
Authors: Crouch Alfred E. , Beuker Thomas
Published: December 2008

This paper describes a novel concept for measuring pipe wall stress. Southwest Research Institute® (SwRI®) pioneered the use of the Barkhausen effect for stress measurement in the 1960s, and the method is still in use today. University researchers in Canada are using the technique for determining stress magnitude and direction by making measurements at quite high resolution. Their technique, which follows from the early SwRI work, requires an alternating magnetic excitation field and an inductive sensor that responds to the Barkhausen magnetic transitions. In contrast, the Continuous Barkhausen concept does not require an alternating excitation field, relying instead on the field transition already present as a magnetic flux leakage (MFL) pig moves through a pipeline. All MFL pigs in use today create Barkhausen noise as they move through the pipeline. The only requirement for using those signals to reveal information about the pipe is to provide suitable sensors and amplifiers to develop a data interpretation procedure. This paper reports on work sponsored by the U.S. Department of Transportation in which SwRI and their commercializing partner, H. ROSEN Engineering, performed laboratory and pull-test experiments to validate the technique using MFL pig hardware in a test line having artificially induced stress anomalies. Details of the technique, laboratory experimental results, and pull-test results are presented, along with recommendations for the application of the method to operating pipelines.
Estimating the Influence of Natural Hazards on Pipeline Risk and System Reliability
Authors: Porter Michael , Logue Clint , Savigny K. Wayne , Esford Fiona , Bruce Iain
Published: December 2008

Natural hazards (also known as ground movement or geohazards) can cause pipeline failures, with consequences ranging from injury/death, environmental impact, and property damage, to lengthy service disruption and a failure to achieve delivery targets. In North America and western Europe, pipeline failure resulting from natural hazards are typically rare (but costly) events. However, where difficult ground conditions have not been properly accounted for in pipeline design, construction, and operation, natural hazards may have an overriding influence on pipeline risk and reliability. These issues are discussed, and a framework for estimating the influence of natural hazards on pipeline risk and system reliability is introduced.
Decision Making Under Uncertainty in Pipeline Projects Using Monte Carlo Simulation
Authors: de Brito Garcia Claudio , Machado Leandro Bastos
Published: December 2008

Uncertainty about a situation can often indicate risk, which is the possibility of loss, damage, or any other undesirable event. Most people and organization desire low or minimized risk, which would translate to stand to a scenario of high probability of success, profit, or some form of gain. This work shows the importance of risk analysis when it comes to compare two capital investment projects in the natural gas transmission business. A transmission company needs to choose between two alternatives for capacity expansion of a pipeline, with a maximum value for the transmission tariff previously agreed to the shipper. At first, the transmission tariff is calculated by the conventional method that comprises iterative calculation from an arbitrary value, until the project Net Present Value (NPV) reaches zero. Once calculated, the lower of the transmission tariffs associated to the two expansion projects indicates the best choice. That’s the way the majority of companies perform their economical analysis of the proposed problem. Monte Carlo Simulation risk analysis technique is a powerful tool to asses the risk associated to a capital investment project, which can be summarized as the probability of undesired results. The risk calculation is based on the uncertainties associated to the input data used to build the project free cash flow, and the simulation produces a frequency distribution, or histogram, for, the NPV of a project. As will be seen in the work, the investment with the largest expected NPV may not always be the best investment alternative.
Selection of External Coatings for Northern Pipelines: Laboratory Methodologies for Evaluation and Qualification of Coatings
Authors: Papavinasam Sankara , Revie R. Winston , Attard Michael
Published: December 2008

In the near future, the construction of northern pipelines for transmission of natural gas will begin in North America. Construction in the harsh northern climate, with temperatures as low as −45°C, and remote location will impose unique challenges with respect to protective coatings. It is critical that the design of coatings be adequate to protect the pipelines under long-term, severe environmental conditions, including the extreme climatic conditions that will apply in the North before the pipe is installed and operation begins. There are many quality coatings from which to choose for application on new pipelines. The main issue is in understanding how to select and use coatings on pipelines in new regimes (e.g. Northern pipelines), which may operate in a different environment than do existing pipelines. Uniform, standardized tests that would simulate the conditions during construction and operation of Northern pipelines will allow external pipeline coatings to be selected with confidence regarding anticipated long-term performance under operational conditions. Selection of mainline coatings is important, but there is also a need to focus on field-applied coatings for both repairs and joints. Methodologies and standards that are available to evaluate coatings are reviewed in this paper.
Pipeline Integrity: Establishing Data Management Value
Authors: Dupuis Bruce , Humber Jason
Published: December 2008

For the majority of pipeline operators struggling to establish the business case for data management, records management, or geographic information systems, a step past the traditional information technology approach of return on investment (ROI) must be made. Traditional information technology value propositions are founded on information efficiencies that, for the most part, are extremely difficult to quantify since the processes are either not presently performed or the effort associated with the existing process has not been measured. Without a baseline of the existing process, a comparative analysis using improved efficiencies cannot be quantified to substantiate a return on investment. Justification of a data management system and its associated benefits in terms of its cost relative to the cost of the data it manages (e.g. ILI, excavation, CIS etc.) is compelling since it is only on the order of 2–10%, but typically even this metric is too general an argument for most pipeline integrity managers to feel comfortable defending. This paper will explore the process required to unearth the value of data management to support pipeline integrity. Many examples and cases will be discussed to back-up the approach to establishing value of data management for pipeline integrity.
Challenges in Developing a Comprehensive, Automated and Flexible Oil Accounting System
Authors: Nordell Lane F. , Ruda Hanif
Published: December 2008

This paper will present the context, objectives, challenges and innovative software development and project management techniques that enabled the building of a comprehensive oil accounting (OA) system. A major stage in the continuing development of OA components, completed in 2002, replaced an aging legacy system and added considerable functionality. Components are added to the OA system on a continuous basis The target result is an automated crude oil balancing and revenue accounting system that interfaces with other pipeline-management software systems. The challenge was to custom build and implement an OA system that: • Significantly reduces dependence on IS resource’s specialized skills. • Automates data validation between pipeline operations and management software systems. • Reduces turn-around time of the monthly invoice cycle. • Dramatically increases customer’s information availability and enhances information dissemination to customers. • Accommodates new business rules with minimal reconfiguration effort. The project management approach was to compress system development and delivery into predictable and controllable segments. These segments deliver complete components into the production environment at established milestones rather than as a whole system at a single “big-bang” event. The segmented delivery approach is known as SCRUM in the IT industry. It enabled the team to react effectively to changing business requirements throughout development. Additional techniques known as XP (Extreme Programming) were also utilized to greatly enhance the quality and predictability of system delivery. XP stresses very strong and committed client project involvement. This paper will outline the oil accounting system components and the SCRUM and XP techniques the project delivery team believes have significantly enhanced the success of the project. Due to the proven success of these techniques they are currently being used in several other IS projects including additions to the OA system. In summary, the project management and software system development approach, and stakeholder involvement secured the success of the OA system delivery. These approaches embody the philosophy of continuous improvement and superior quality in information system delivery.
Avoidance of Slack Flow in Liquid Pipelines
Authors: Ma Te , Youzwishen Oliver O. , Hylton Michael
Published: December 2008

There are many existing liquid transmission pipelines that have significant changes in elevation along their route, making them susceptible to operating at “slack flow” conditions. Slack flow occurs in a pipeline when the pipeline pressure falls below the vapor pressure of that liquid (i.e. the pressure head decreases below the elevation at a certain point and causes the gauge pressure at that point to drop below zero atmosphere). Separation of the fluid column occurs, which can result in leak detection system inaccuracy and poor pressure/flow control during pigging operations. The designs of older pipelines typically did not address the slack flow issue. In order to eliminate the occurrence of slack flow, some method of pressure control is necessary, such as the installation of a pressure regulator station (PRS). In this paper a case study is used to demonstrate how a detailed hydraulic analysis was utilized in the design of an effective PRS, to eliminate slack flow. The subject pipeline system was approximately 800 km in length; with six pump stations and one terminal tank farm. One section of the pipeline contained an elevation difference of more than 1000 m (between mountain top and river valley bottom), creating slack flow operating conditions. A decision was made by the pipeline operator to prevent (potential) over pressurization at the lowest point on the pipeline. A secondary goal was to upgrade the leak detection system by eradicating the slack flow operation. Designing and installing a PRS and an over-pressure safety valve station achieved both of these goals. The PRS design, operation philosophy and safety philosophy development utilized information derived from a transient hydraulic simulation of the pipeline, using a hydraulic pipeline simulator (HPS). By using transient hydraulic analysis, an optimized solution to slack flow and over-pressuring on a liquids pipeline with large elevation differences, was achieved. By installing a PRS in an optimized location the pipeline operator has increased the reliability of leak detection and reduced the risks of over-pressuring, in a safe, cost effective manner.
Pipeline Coating Comparison Methods for Northern Pipelines
Authors: Singh Peter , Purves G. A. (Andy)
Published: December 2008

During the construction of a pipeline project, and especially a pipeline project in a Northern environment, it is essential that the pipe coating selection is suitable for the conditions that will be encountered in the field. The pipe coating system must also provide the requisite performance during the operating phase, to ensure that a high calibre pipe protection is achieved and the anticipated design life is produced. The remedial expense of repair is exceptionally high and repair logistics are compounded by the environmental conditions and remote location. Coating selection must take account of the expected local conditions to achieve the optimum life-cycle costs for the system. The effects of cold temperature and soil types on the installation and operation processes are some of the major factors affecting the suitability and ultimate integrity of the pipe protection coating.
An Underground, In-Line Heater for Gas Gathering Pipeline Systems
Authors: Storrow David
Published: December 2008

As central processing of multi-phase well effluent is becoming more common than field processing, sour gas gathering systems must be maintained at temperatures that do not allow the formation of hydrates. For short systems, heating the gas at the well site (to maintain a temperature that will prevent hydrate formation) or adding methanol to the fluid (to suppress the hydrate temperature) may be acceptable. For large gathering systems, a method of reheating the gas in transit is necessary. The conventional method for reheating sour gas gathering systems is to bring the multi-phase effluent above ground and send it through a heat exchanger. This method requires significant piping, valves, fittings, etc., and results in increased friction pressure losses and brings with it the difficulty of opening the mainline valve (either manually or remotely) when the pipeline requires pigging — all of which will increase capital and operating costs. Reheating above ground also requires toxic/corrosive fluids to be brought to the surface, in closer proximity to operations personnel, causing additional safety and environmental concerns. An underground in-line heating system has been developed to reduce the economic and operational impact of reheating the multi-phase hydrocarbons. The inline heating system eliminates the need to divert the multi-phase effluent from the pipeline by using a single-pass heat exchanger that operates below ground as part of the pipeline. Recirculated glycol is used as the heating medium for this system. The compact, below-ground facility requires only valving on the glycol circuit piping and will keep sour process fluids isolated and away from enclosed buildings where operating staff are present and out of more complex piping with greater potential to leak. As the underground heater is part of the pipeline, pigging operations can continue unhindered. Seven underground in-line heaters have been designed and installed by CIMARRON Engineering Ltd. since 1995. The installed heating systems have been proven to be reliable and easy to use. The underground inline heaters have been found to cost significantly less than the conventional above ground heating system. Other potential uses for the buried heater are: heating of viscous fluids, such as heavy oil (to eliminate need for diluent) and using the heat exchanger for cooling of gas following compression.
High Temperature Pipeline Design
Authors: Greenslade John G. , Nixon J. F. (Derick) , Dyck D. W. (Wes)
Published: December 2008

High temperature operation is an alternative to the use of a diluent to reduce the viscosity of heavy oil or bitumen for pipeline transportation. This paper deals primarily with two fundamental design issues for a hot bitumen (hotbit) pipeline, modeling the restart problem and establishing the maximum practical operating temperature. The concept of flow capacity is introduced to model the transient behavior during restart of a high temperature pipeline filled with a high viscosity fluid that has cooled during a shutdown. The heat lost from a buried high temperature pipeline causes environmental disturbance by elevating the ground temperature near the pipeline. This can alter growing conditions above even an insulated, deeply buried pipeline. Results are presented for a hypothetical case modeled using a thermal simulator developed by one of the authors. Axial thermal loads increasingly constrain the design and operation of a buried pipeline as higher operating temperatures are considered. Strain based design affords the opportunity to design for higher operating temperature than allowable stress based design techniques. With either design method, there is a temperature at which expansion loops are required to partially relieve the thermal stress. As the design temperature increases, there is a point at which an above grade pipeline becomes an attractive option.
Analysis of Ruptures and Trends on Major Canadian Pipeline Systems
Authors: Jeglic Franci
Published: December 2008

The number of ruptures per year is one of the National Energy Board’s (the Board) measures of safety performance of the federally regulated oil and gas pipelines. This measure was examined and analyzed over twenty, ten, and five years with respect to the rupture causes, ignitions, fatalities, injuries, pipeline age, in-line inspections, and the Board’s safety interventions. There were forty-six ruptures over the twenty-year period, twenty-three over the ten-year period, and seven over the five-year period (Ref. 1 and 2) on the 43,000 km of the regulated pipelines. The average time from the pipeline installation to the time of rupture for the time-dependent rupture mechanisms is twenty-eight years. There were three fatalities and fourteen injuries caused by the ruptures of the federally regulated pipelines over the past twenty years. Ruptures associated with fires of the gas and high vapour pressure pipelines caused most of the fatalities and injuries. The dominant rupture causes are external corrosion, stress corrosion cracking, and third-party damage in this order of magnitude. The pipelines that ruptured during the last five years were internally inspected. The in-line inspection tools could not properly detect the defects that caused the ruptures. Regulatory interventions, such as public inquires, Board Orders, and regulatory requirements, have reduced the number of ruptures due to the targeted cause. The number of ruptures and safety consequences associated with them have decreased over the last ten years.
Laboratory Evaluation of Soil Stress Corrosion Cracking and Hydrogen Embrittlement of API Grade Steels
Authors: Bueno A. H. S. , Castro B. B. , Ponciano J. A. C.
Published: December 2008

Stress corrosion cracking is one among several corrosion processes than can occur on buried pipelines. Efforts must be made in order to prevent this form of corrosion as long as pipeline collapse can cause accidents with high economic costs associated and environmental damage. In the present work, Stress Corrosion Cracking (SCC) and Hydrogen embrittlement (HE) of pipeline steels in contact with soil was investigated. Samples of different soils were obtained and prepared in order to determine its physical, chemical and bacteriological characteristics. Slow strain rate testing were carried out by using electrolytes obtained from soil samples extracted from different points located close to buried pipelines. Stress vs. strain curves of API X46, X60 and X80 steels were obtained at different electrode potentials (Ecorr, 100mV below Ecorr and 300mV below Ecorr). The results obtained demonstrated the conjoint incidence of SCC and HE, depending on the potential imposed. These results revealed the SCC susceptibility of the steels. It was also observed that the hydrogen embrittlement — HE — has an important contribution to cracking initiation and propagation. Cracking morphology was similar to the SCC reported on field condition where transgranular cracking were detected in a pipeline collapsed by land creeping. It was important to point out that even under cathodic potentials the material showed the incidence of secondary cracking and a significant decreasing of ductility. The mechanism was similar to the one described by Parkins and coworkers to explain the incidence of stress corrosion cracking of carbon steel in near neutral soil.
An Approach to Coating and Cathodic Protection Design on Long Distance Gas Pipeline
Authors: Bacchi Luca , Brugnetti Fabio , Castano Michele , Zanardo Fabio
Published: December 2008

Eni group is working on a gas transportation project aimed to develop and verify the technology for a “LD-HC-HP-HG” (Long Distance–High Capacity–High Pressure–High Grade) gas pipeline named TAP (Trasporto Alta Pressione). Interest in high pressure and high grade pipe steels is due to the increasing necessity of economic gas transportation on long distances between upstream and downstream in an international context. In the past Eni group has already studied long distance pipeline materials from the economic and pre-feasibility point of view. Now, with TAP project, Eni is going to do an “in field experience” with high pressure and high grade steels to concur and to promote the “gas to market” with the “pipeline” option. Snam Rete Gas competences in the project are related to: • partial contribution to the technical characterization of field welding joints; • analysis of solutions for coating and cathodic protection especially dedicated for long distance pipelines. The building of a pilot pipeline in X100 grade steel is an opportunity to test new technologies and new instrumentations to economically prevent corrosion with coating and cathodic protection in long distance pipelines where there could be logistic problems for the systems inspection and maintenance due also to the extreme environmental conditions. Design of the system solutions according to a “life cycle costing” approach and analysis of the experimental results of the pilot pipeline in X100 grade steel will be both included in the project. Aim of this paper is to suggest an experimental approach to coating and cathodic protection design on long distance gas pipeline in order to minimize inspection and maintenance costs, very relevant for such a type of application.
Investigating the Effectiveness of Techniques Used in Assessing the Integrity of Non-Piggable Pipelines
Authors: Achterbosch Giorgio G. J. , Stallenberg Gerard A. J.
Published: December 2008

A substantial part of the high pressure gastransport network of Gastransport Services as part of N.V. Nederlandse Gasunie in the Netherlands is not piggable. It is therefore foreseen that an ECDA approach including coating survey techniques, CP measurements and bell hole excavations, will be implemented to establish the integrity of these non-piggable lines. In order to get a better understanding of the performance of some techniques for our specific situation, a test program was carried out on a pipeline of 33 kilometres with a diameter of 8” and bitumenous coating, constructed in the sixties. DCVG, Pearson and a combination of CIPS and Pearson (CIPP) were tested in combination with 3 MFL intelligent pigruns, current attenuation measurements by the Stray Current Mapper (SCM) and bell hole excavations. Initial results for the three coating survey techniques showed that the detection probabilities for a coating defect ranged from 18% to 68% under the assumption that no false calls were generated. Using results from repeat measurements and taking into account the possibility of false calls, the detection probabilities increased to potential maximum values of 48% to 94%. Better estimations of the values could be obtained after verification of some indications from CIPP, leading to maximum values in the range of 70% to 84% for the best two techniques. Additional measurements at pre-selected locations by means of pipe-to-soil-potentials and pin-current measurements did not indicate active corrosion. Verification excavations at 14 locations indicated that in all situations a coating defect existed and that mild general corrosion was present in eight situations due to the very aggressive soil (soil resistances of several Ωm’s were measured). Current attenuation measurements by the SCM suggested a uniform distribution of coating quality. The results from the three intelligent pigruns were of relatively little use because of the detection threshold of 15% wall thickness and the fact that the suppliers often did not agree on the interpretation of metal loss. Therefore the results could not be considered to be an absolute true reference for relating the coating defects to. Although the results of the program gave very valuable insight into the characteristics of the different techniques it is recognized that not all results can be translated to other circumstances/pipelines. Therefore additional tests and surveys will be carried out in the coming year(s) to further work out the ECDA procedure for the specific situation of the non-piggable pipelines of Gastransport Services.
The Interaction of Free Span and Lateral Buckling Problems
Authors: Galgoul Nelson Szilard , Paulino de Barros Julia Carla , Ferreira Rony Peterson
Published: December 2008

The traditional design approach for most engineering problems, of which pipelines are no exception, is to segment the project and to present design solutions for each of these design items. When setting up a pipeline schedule, therefore, one will find an item called free span analyses and another called global buckling, which covers both lateral and upheaval buckling problems. This has been justifiable so far, because freespan vibrations have traditionally been treated totally dissociated from the axial force on the pipe, while lateral buckling is a problem to which, only recently, the industry has turned its attention. DNV has a tradition of being the regulatory agency, which has a lead on vortex shedding problems. This tradition has recently been confirmed, when they issued a new freespan vibration guideline [1], in which they are now considering the interaction of axial forces in the calculation of the pipeline vibration frequency. Shortly after this code was issued, the authors undertook three large pipeline projects, in which the use of the aforementioned code was a contractual requirement. If on one hand, however, the owner insisted upon the use of the new DNV code, on the other he was not willing to accept the very short free span limits, which were resulting from the calculations. Because of this, the authors were forced to look at the problem in further depth, thus resulting interesting conclusions, which will be presented in this paper. These point out some conservative aspects of the code, and make suggestions as to how this conservatism can be overcome, in order to use the DNV safety approach and still produce larger spans, by properly focusing on the freespan buckling problem. In addition to this, the authors have concluded that the freespan buckling problem cannot be dissociated from global buckling, because, in general, it was found that the pipe not seldom moves from a local span buckling mode to a global lateral buckling mode, thus giving the free span problem a completely different emphasis. The experience gained during these projects will be shared in this paper.
Development of LaserPro System for External Corrosion Mapping With Integrated Assessment
Authors: Holloway Paul , Inman Vaughn , Cronin Duane
Published: December 2008

This paper presents the design and application of a new semi-automatic tool for mapping external pipeline corrosion. The device hardware is complemented by the implementation of current corrosion assessment techniques via online software. The development of this device is based on over 10 years of experience in external corrosion mapping and automated scanner development, in support of an experimental research program at the University of Waterloo. The mapping device hardware consists of a novel position measurement system which is coupled to a laser-based depth measurement device to generate a surface map of corrosion defects. Direct comparison with manual (pit gauge) and fully automated measurements has shown that a given defect can be quickly and accurately mapped using the new system. Automated data capture and evaluation has demonstrated significant improvements over fully manual pit gauge-based methods. In addition, the manual position of the measurement head allows the user to map only those areas which are pertinent to the assessment. This is in contrast to fully automated methods which require continuous measurements over predefined areas of a pipe. Online feedback compliments this system and allows the operator to determine if the data set is complete by providing information on the convergence of the predicted failure pressure. Using this new mapping device, measured surface maps of natural complex corrosion defects are shown to compare favorably with other mapping devices and manually measured defect dimensions.
Structure and Properties of X80 and X100 Pipeline Girth Welds
Authors: Gianetto J. A. , Bowker J. T. , Dorling D. V. , Horsley D.
Published: December 2008

This study aims to provide an understanding of the factors that control weld metal strength and toughness of mechanized field girth welds produced in X80 and X100 line pipe steels using a range of pipeline gas metal arc welding procedures. In the investigation of X80 welds, a series of experimental single and dual torch gas metal arc welds were prepared with three C-Mn-Si wires, which contained additions of Ti, Ni-Ti and Ni-Mo-Ti. The weld metal microstructures, tensile properties, notch toughness, and fracture resistance were evaluated. The results indicate that high weld metal yield strength and good toughness can be achieved. The X80 single torch welds exhibited higher yield strength but lower toughness compared to the corresponding dual torch welds. For the development and evaluation of welding procedures for mainline girth welding of X100 pipe, two narrow gap mechanized gas metal arc welding procedures were evaluated with emphasis placed on measurement of the tensile properties. The results show that dramatically different properties (strength and toughness) can be found as a result of differences in energy input, interpass temperature and weld width or offset distance. Additionally, the preliminary tensile testing, which utilized both standard round bar and modified strip tensile specimens, illustrates the potential variation that can occur when assessing all-weld-metal tensile properties of narrow gap pipeline girth welds.
Compressor Station Fuel Gas Superheating Using Lube Oil Waste Heat
Authors: Sell Katie T. , Langston Paul R. , Mitchell Rene´ H.
Published: December 2008

Compressor station gas turbine engines require protection from fuel gas liquid drop-out caused by the Joule-Thomson effect when natural gas is let down from transportation line pressure to the burner supply pressure. Indeed, gas turbine manufacturers specify a minimum gas superheat, which requires fuel gas heating at pipeline temperatures experienced in Northern Europe. Conventionally, fuel gas superheating is achieved through the use of either electric or gas fired water bath heaters, which require maintenance, and an external heat source. Meanwhile, waste heat from the turbo-compressor lube oil system is released to atmosphere, typically by air-cooled heat exchangers. Hence, there is an obvious opportunity to protect the gas turbine engine, whilst reducing the amount of heat rejected to the environment. Mechanical integrity is a key operational requirement when combining fuel gas superheating with lube oil cooling in a single heat exchanger. Fuel gas at high pressure must not enter the low pressure lube oil system. High integrity Printed Circuit Heat Exchangers (PCHEs) are ideally suited to this application, as they are diffusion bonded and fully welded heat exchangers. Used extensively in offshore high pressure gas compression trains in the North Sea, PCHEs have demonstrated that they are low maintenance items that are ideal for use in remote unmanned applications, such as those required by gas compression stations. PCHEs are highly compact, reducing space and structural requirements. This allows the exchanger to be installed underneath the compressor, minimizing the visual impact of the heat exchanger. In addition, safety and pressure relief requirements are significantly reduced, a PCHEs do not have a failure mode analogous to tube rupture in shell and tube heat exchangers. National Grid Transco have realized the opportunities of PCHEs and operated them successfully over many years in many of their compression stations throughout the United Kingdom.
Target Reliability Levels for Design and Assessment of Onshore Natural Gas Pipelines
Authors: Nessim Maher , Zhou Wenxing , Zhou Joe , Rothwell Brian , McLamb Martin
Published: December 2008

This paper proposes a set of reliability targets that can be used in the design and assessment of onshore natural gas pipelines. The targets were developed as part of a PRCI-sponsored project that aims to establish reliability-based methods as a viable alternative for pipeline design and assessment. The proposed targets are calibrated to meet risk levels that are considered widely acceptable. The proposed criteria are based on a detailed consideration of both societal and individual risk criteria. Two societal risk criteria were considered; the first based on a fixed expectation of the number of fatalities and the second based on a risk aversion function as characterized by an F/N relationship. Societal risk criteria were calibrated to match or exceed the average safety levels implied by current codes. Individual risk criteria were based on published tolerable levels. The target reliability levels corresponding to the three criteria are presented and a recommended set of targets is presented.
Integrity Management and Operating Experience of Gas Pipelines in Delhi
Authors: Prasad Neetu
Published: December 2008

The operation of gas pipelines in utility corridor of a metropolitan city in a developing country has unique challenges. Through this paper, I would like to discuss the threats and mitigation measures in city area pipelines so as to ensure Pipeline Integrity. Excavations keep occurring because of various developmental activities. Construction of Flyovers, roads and subways disturb the pipeline route constantly necessitating Shifting / lowering of operating pipelines. Fault rectification by other agencies sharing the corridor, and proximity of High Voltage lines have also led to incidents resulting in gas leakage. Pipeline Integrity Surveys have been carried out in Delhi area and based on their recommendations, as well as a result of analysis of various incidents that have occurred in the past, a mitigation plan was developed. All the points were complied to ensure the safety and Integrity of pipelines. As can be seen from the various case studies of the past, often risky situations arise due to absence of proper layout design of underground facilities. Liaising with utility corridor agencies and appointing a central regulator for utility corridor, mapping and allocating work permits in the corridor with the help of Geographical Information System (GIS) and other advanced mapping and remote sensors, could become an effective solution. GAIL has developed a GIS for Delhi area pipelines which is proving very useful. To ensure the integrity and safety of the pipeline, a proactive approach is required. Integrity management of Pipelines is a continuous process. Evaluation has to be done constantly and newer steps should be taken each time if required.
Lateral Buckling: Trying to be Less Conservative
Authors: Galgoul Nelson Szilard , Lupinacci Massa Andre´ Luiz , Claro Cla´udia Albergaria
Published: December 2008

Over the last few years, lateral buckling has gone from a secondary issue to one of the major concerns in pipeline design. Not many years ago pipelines were thought of as flexible elements, which could absorb virtually any kind of displacement, but due to the trend to increase fluid temperatures and after a few major environmental accidents, it seems that lateral buckling became the major design issue. Burial was then assumed to be the only safe solution. This is the normal reaction to every traumatic experience, but now that there is alertness and that accidents are being prevented, it is once again time to re-evaluate and see where caution has become excessive and what cheaper alternatives can be used. Several papers have been written over the last 3 or 4 years addressing this issue, [10–13] for instance, and, in general, one could say that there is a consensus regarding the need to know more about how pipelines move, when they buckle laterally, and to what extent they should be allowed to do so. Still another issue, which has been discussed along with this one, is related to how cyclic motions (due to cycles of heating and cooling) can aggravate the problem. Attention is drawn to the fact that the buckling analyses are usually performed based on models conceived to simplify the design, while, on the other hand, construction and installation pay a penalty, because of unnecessary conservatism, which could be avoided if a bit more effort was put into the design. Just to illustrate what is being said, let us consider a typical lateral buckling problem and how the practice has decided it should normally be treated: 1. Determine the pipeline embedment length (that for which the pipeline will build up sufficient axial friction to anchor the axial force due to the temperature variation). 2. Build a model twice that size, embedded at both ends; using a program, which can model axial and lateral friction (this is a nonlinear analysis). 3. Build a prop type lateral installation deviation at the center of the model. 4. Analyze the pipeline assuming that the expansion from both sides will build into that deviation, thus causing the pipeline to buckle at that section. In spite of having become a traditional design approach, it is associated with a conservative model. The bottom is assumed flat, the soil model is a simple elasto-plastic spring and, also, that there is only one lateral imperfection, which will concentrate all the axial expansion. The object of this paper is to show that it can be very advantageous to spend more time and money, on the design, using more detailed analysis models, in order to save much more on the construction and installation. This will be done by sharing the experience gained based on the use of such models, during several recent pipeline projects, handling over 300km of pipes, with diameters varying between 6 and 34 inches in water depths ranging from 0 to 2000m.