bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenges in Circumferential Magnetisation II: A FEA Point of View
Authors: Ireland R. C. , Torres C. R.
Published: October 2008

In order to design a Magnetic Flux Leakage (MFL) tool, knowledge of the magnetic field profile both within the pipe wall and around the sensor locations is required. The former is important since the magnitude of a defect signature will be maximised when the pipe wall is magnetically saturated. The latter is important for the reason that the background magnetic field profile will determine the sensor bias level for a given defect. Previous research using the Finite Element (FE) technique has investigated the magnetic field profile within the pipe wall for a generic circumferential MFL tool and showed how it varied depending upon the pipe wall thickness and tool speed. It was found that as the pipe wall thickness and tool speed increased, a plume of magnetic flux formed behind the tool. Furthermore, it was observed that as the pipe wall thickness increased, outer regions of the pipe wall exhibited substantially reduced levels of magnetic flux. A reduction of magnetic flux in these outer regions of the pipe wall suggests defects located here may be harder to detect and resolve compared to defects located closer to the inner pipe wall. This paper briefly reviews the previous research and extends the numerical analysis by considering the magnitude of the magnetic field profile for locations within the inner and outer pipe wall and possible sensor positions. It is shown how these profiles change with pipe wall thickness and tool speed and demonstrates the complex and non-linear nature of the magnetic field. The information obtained can be combined with previous research and will be useful for determining the optimal sensor location and yield predictions for background magnetic field magnitudes. The full complexity of magnetic materials is not incorporated into the modelling, however, the results obtained give a theoretical indication of operational limitations of the circumferential MFL technique.
Challenges in Pipe Defect Detection Using a Generic Axial MFL Tool: A FEA Point of View
Authors: Ireland R. C. , Rahman A. Y. A. , Torres C. R.
Published: October 2008

As a Magnetic Flux Leakage (MFL) tool traverses along a section of pipe, the pipe wall is locally magnetically saturated. At locations where a defect exists, magnetic flux intensity changes. This change is detected by a set of sensors as the tool passes down the pipeline and is recorded on a data logger. This paper describes Finite Element (FE) modelling of a spherical defect located within the outside of the pipe wall. Two meshes are created: a mesh of an axial MFL tool and a mesh of the pipe (containing the defect). To perform a dynamic, time-transient analysis, the meshes are joined together using a Lagrangian interface, set in motion relative to each other and the magnetic field calculated for several time steps. The corresponding magnetic signature of the defect can be calculated. Two pipe wall sizes are considered (a thick 0.625 inch pipe wall and a thin 0.375 inch pipe wall) for a 30 inches pipe Outer Diameter (OD), with defects positioned directly above the line travelled by a set of the MFL tool’s magnetic poles and offset between the magnetic poles. Corresponding signal-to-background field analysis (the magnetic bias ratio), for a tool moving at a speed of 1mph, reveals the thicker pipe gives the largest ratio, with a central defect location giving a better ratio than an offset defect. The analysis can be used to predict the best sensor positions, the magnetic bias ratio and the optimal circumferential sensor spacing. The method can be used to investigate a variety of defects and to gauge the performance and limitations of the axial MFL technique. It should be noted that FE methods do not presently incorporate the full complexity of the magnetic material properties and that realistic, complicated defect geometries will be computationally expensive. However, the results presented give a theoretical indication of typical magnetic signatures that may be obtained for spherical defects using the axial MFL technique.
Reliability Based Design and Assessment for Location-Specific Failure Threats With Application to Natural Gas Pipelines
Authors: Nessim Maher , Zhou Wenxing , Zhou Joe , Rothwell Brian
Published: October 2008

The acceptance criteria used in Reliability Based Design and Assessment (RBDA) are defined as a set of reliability targets (where reliability is defined as 1.0 minus the probability of failure). Because of the linear nature of pipeline systems, reliability targets are defined on a per km-year basis. Such targets are directly applicable to failure causes (or limit states) that are equally likely to occur anywhere along a segment of the pipeline (e.g. equipment impact or yielding/rupture of defect-free pipe under internal pressure). They are, however, not directly applicable for design and assessment situations involving limit states that apply at known specific locations. Examples include design for geotechnical loads on a particular unstable slope or integrity assessment of specific corrosion defects based on in-line inspection data. In previous work, reliability targets for natural gas pipelines have been developed on the basis of appropriate societal and individual risk criteria. This paper describes an approach to adapt these targets, and demonstrate compliance with them, for location-specific limit states. The approach is based on using separate checks to ensure that the individual and societal risk criteria underlying the targets are met. An example is included to demonstrate application of the approach to design a pipeline on an unstable slope.
A Departmental Open Source Pipeline GIS
Authors: Kneller Geoffrey R.
Published: October 2008

Geographic Information System (GIS) software has evolved to the point where it is extremely valuable to the planning, construction and operation of pipelines across a range of industries. Recently, GIS software of high quality has become freely available for use and modification under open source licensing schemes. This paper evaluates the utility of a geographic information system prepared using open source software for shared departmental use. Analysis includes areas such as functionality of the software, setup time, and total cost of ownership. The departmental focus is at a level concerned with pipeline planning and cost estimating. The full GIS package used for the analysis consists of a database, spatial data management software, and a web server providing web-based access to geomatic data suitable for a pipeline construction department. The utility of application programming interfaces provided through the GIS with open source software development tools is analysed in the form of a what-if economic comparison tool for pipeline route selection. The ability of the GIS to integrate data from other departmental systems is also examined. Final conclusions serve to aid pipeline GIS teams in determining if open source solutions are ready for widespread use.
Buoyancy Control on the 56” Cross Island Gas Pipeline Project, Trinidad and Tobago
Authors: Hernandez Luis A.
Published: October 2008

The Cross Island Pipeline (CIP) consists of approximately 76.5 kilometers of 56-inch natural gas pipeline from Beachfield to Point Fortin and originally designed with a total of 2.8 kilometers of continuous concrete weight coat for buoyancy control. Alternate design and construction techniques were used to improve the efficiency of the pipeline construction methods used for the concrete coated sections. In areas where temporary work space was limited due to the crossing of foreign pipelines; or where induction bends were installed; or where the 56” pipeline closely paralleled existing pipelines, an alternate method of weighting had to be considered. Bechtel proposed alternative methods for buoyancy control such as installation of Concrete Strap-On Weights and the use of Geotextile Buoyancy Control Saddle Weights.
Safety and Loss Management System for Pipelines
Authors: Abes Jake
Published: October 2008

Management systems have long had widespread acceptance in many industries for various applications: notably quality, safety and environment. In recent years, the onshore pipeline industry has started adopting management system principles for the management of pipeline integrity. This paper discusses the rationale for adopting a systems approach to safety and presents a safety and loss management system template that may be used for the full life cycle of a pipeline, from concept to abandonment.
Applicability of Existing Models for Predicting Ductile Fracture Arrest in High Pressure Pipelines
Authors: Wolodko John , Stephens Mark
Published: October 2008

The ductile fracture arrest capability of gas pipelines is seen as one of the most important factors in the future acceptance of new high strength pipeline steels for high pressure applications. It has been acknowledged for some time that the current methods for characterizing and predicting the arrest toughness for ductile fracture propagation in high strength steels are un-conservative. This observation is based on the inability of existing models to predict the required arrest toughness in full-scale ductile fracture propagation tests. While considerable effort is currently being applied to develop more accurate methods for predicting ductile facture arrest, the resulting models are still in a preliminary stage of development and are not immediately amenable for use by the general engineering community. As an interim solution, a number of authors have advocated the empirical adjustment or reformulation of the existing models for use with the newer, high strength pipe grades. While this approach does not address the fundamental issues surrounding the fracture arrest problem, it does provide methods that can be used in the near term for analysis and preliminary design. The desire to use these existing methods, however, is tempered by the uncertainty associated with their applicability in situations involving high pressures and/or high toughness materials. In an attempt to address some of these concerns, a statistical analysis was conducted to assess the accuracy of a number of available fracture arrest models by comparing predictions to actual values determined from full-scale fracture propagation experiments. From the results, correction factors were developed for determining the required toughness levels in high pressure applications that account for the uncertainty in the theoretical prediction methods.
Pump and Motor Replacement Techniques for Pipeline Capacity Expansion
Authors: Dickau Ralph
Published: October 2008

In liquids pipelines, the capacity of the pipeline may be limited by the pipe or by the pumping equipment. Assuming other external constraints such as tankage volumes, injection and delivery rate restrictions are not present, the capacity of an existing pipeline may be increased by several different methods: Pipe-based: • looping, • replacing with larger pipe, • requalifying to higher operating pressures, • adding drag reducing agent, • reducing the fluid viscosity, or • adding intermediate pump stations. In each of these pipeline capacity increase examples, the capacity of the existing pumps may be exceeded in two ways: 1. In flow rate, - the pumps are pumping well beyond their best efficiency point, or 2. In horsepower, - the power required to pump at the higher flow rates is greater than the capability of the existing motor. Therefore, to increase the capacity of a pipeline where the pumps are the source of the restriction, the following methods may be used: Pump-based: • adding more pumps, • trimming the pump impeller in the case of motor overloads, • modifying the pump to a higher capacity, • replacing an existing pump with a larger pump, • replacing the motor with higher horsepower motor, • increasing the speed of the pumps. A pump addition has the advantage of minimizing disruption to the existing facility and has the least impact on throughput, but at a higher cost than pump replacement. A pump impeller trim reduces the capacity of the pump, however, it can allow the pump to run at higher flow rates if the source of the flow limit is due to the motor rating. If the pump and/or motor need to be replaced, the new equipment will likely be larger and will not fit in the old location. The existing wiring, piping, foundations, baseplates, power and controls will therefore be affected by the pump and motor replacements. Careful design and planning will minimize the impact and cost of these replacements and reduce disruption to the ongoing operation of the station facilities. This paper discusses these options for pipeline capacity expansion, taking a practical approach with an emphasis on constructability and avoiding potential problems.
Influence of Forming and Flattening on the Measured Tensile Properties of Linepipe
Authors: Thibaux Philippe , Van Hoecke Dennis , De Vos Gert
Published: October 2008

Steelmakers are producing plates or coils, which are subsequently formed into pipes. The mechanical properties are checked after steel and pipe production, and it is commonly observed that the tensile properties of pipes differ from the properties of plate or coil. The difference in tensile properties is attributed to the forming of the pipe and the subsequent flattening of a pipe section to make a flat tensile test sample. The reverse deformation during pipe forming and flattening is expected to cause a Bauschinger effect leading to a decrease of the yield stress of the pipe compared to the yield stress of the base material. First, a kinematics description of the pipe forming is presented. This kinematics description is important to know the deformation path followed by the material during pipe forming, flattening and tensile test. Once the deformation path is known, the stress state can be computed using constitutive laws. Three constitutive laws are presented here and their ability to describe the mechanical behaviour is further discussed. To determine the mechanical behaviour in reverse deformation paths, a specific experimental set-up has been developed to make reverse tests in tension and compression. Using this experimental facility, an X60 grade on coil has been characterized. Models parameters are fitted on the experimental data. Using these model parameters, a tensile test after forming and flattening is modelled. The simulation shows that a very accurate description of material behaviour is required to predict the final tensile properties.
Properties and Transportation of the Produced Fluid in KD18 Viscous Oil Block, Shengli Oilfield
Authors: Jing Jiaqiang , Guan Zhongyuan , Meng Jiang , Xu Yuan
Published: October 2008

The alumina adsorption, acidity, rheology, image analysis and other related methods are used to characterize the produced fluid in KD18 viscous oil block in Shengli Oilfield. The fluid generally contains 68–75% water cut and about 50–60% bound water. The apparent viscosities of the water-in-oil (W/O) emulsions, varying from 7000mPa.s to 12000mPa.s at 50 °C and the shear rate of 51s−1, are 4–6 times higher than those of the corresponding dehydrated oil. The fluid is transported by a 259-mm-ID, 23.8-km-length pipeline with 2 intermediate heat-pump stations because of its high viscosity, which is followed by high energy and associated gas consumptions. A viscosity reduction method of the W/O emulsion to be inverted into oil-in-water or other composite emulsions by directly adding a sort of viscosity reducer VRKD18 is given in this paper. Composed of two types of nonionic surfactants, VRKD18 is developed by a series of preparations. VRKD18 reduces the apparent viscosity of the W/O emulsion to less than 100 mPa.s at 50 °C and 51 s−1, being more than 98% of apparent viscosity reduction. The reason for this significant viscosity reduction is that VRKD18 changes the outer and inner phase structures of the W/O emulsion, the modes of inner friction, and the drop-drop interaction. A field test for the fluid treated with VRKD18 is performed through the production pipeline. VRKD18 solution is only injected into the fluid by a metering pump at the head heat and pump station, while the other fluids along the pipeline which they are pumped into is not treated. In this article, the inlet temperature of the pipeline is about 50–57°C. The inlet and outlet flow rates are approximately 1200m3/d and 2600m3/d respectively. When the concentration of VRKD18 in the fluid is 300mg/kg, the friction loss along the whole pipeline will be reduced from 1.397MPa to 0.566MPa, i.e. 59.5% of drag reduction. Based on our observation and numerical simulation, such drag reduction is due to the apparent viscosity reduction of the transporting fluid, the wettability improvement on the pipeline inner wall and partial isolation of the viscous oil by the gathered gas at the pipeline top.
Collapse Performance of HTS (Helical Seam Two Step) Welded Line Pipe
Authors: Knoop Franz Martin , Groß-Weege Johannes , Marewski Ulrich
Published: October 2008

Line pipe intended for offshore applications has to be designed predominantly with regard to external pressure in order to avoid collapse. High resistance to external pressure is vitally important for the use of pipes in such applications. A test program has been carried out in order to verify the resistance of HTS (helical seam two step) welded line pipe against collapse. It was demonstrated that the two step pipe manufacturing process has a beneficial effect on collapse resistance. HTS pipes therefore shows a good collapse performance compared to the design equations given in relevant offshore standards. One aim of the work carried out was to quantify the influence of relevant parameters on the result of full-scale collapse test by finite element analysis. The actual collapse pressures and those predicted using currently available design equations are compared and verified for various boundary conditions. The paper concludes with a discussion of the major findings and with a brief outlook to future research issues.
Experimental Investigation of Rheological Behaviors and Flow Improving by Chemical for Waxy Crude Oils
Authors: Jing Jiaqiang , Guan Zhongyuan , Xiong Xiaoqin , Tian Hua , Tan Liwen
Published: October 2008

It has been proved that the flow improver makes the transportation of waxy crude oils in pipeline much more economic and safe, but so far an universal flow improver for various waxy crude oils has not been found because of inadequately understanding the action mechanism of the flow improvers. Therefore it is necessary for the mechanism to be studied further. A series of synthetic waxy oils (SWOs) with or without flow improver GY1, a long chain alkyl acrylate polymer based chemical, are prepared from 25# transformer oil, 50#, 60# (macrocrystalline) and 80# (microcrystalline) wax, single or mixed, and in some cases 60# road asphalt by mixing the ingredients at 100°C for 1 hour. Characteristic temperatures, viscosity-temperature properties and rheological behaviors are studied by using rheological techniques, and microstructures of wax crystals grown from SWOs at 20 °C are analyzed by using a polarization microscopy. Some abnormal viscosity-temperature properties of SWOs are found, which mainly results from wax crystallization and network structure formed by wax crystals. The mechanisms involved in the structure formation and fluidity improved by chemical for SWOs are discussed here. Studies show that the structure formation is followed by the formation of crystal nuclei, growth and interconnection or bridging of the wax crystal particles, which is closely relevant to wax molecular dimension and content, crystalline particle size, shape, concentration and surface characteristics. GY1 added into the SWOs lowers their cloud points by 0–2.0 °C and enhances the amounts of wax precipitated at 30 °C by 10–35wt%, which might not be involved in the mechanisms of the fluidity improving under this study. The extent of pour point depression by GY1 increases with increasing the wax molecular size and decreasing the wax content in the SWOs. As long as the SWO treated by GY1 has a greater yield stress reduction at the temperature closed to its pour point, its viscosity and pour point reduction will be more obvious. The common shortcut of pour point depression and viscosity reduction is to inhibit or desintegrate the formation of paraffin crystal network. The mechanisms involved in fluidity improvement of waxy crude oils by chemicals include modifying surface properties of waxy crystals and promoting crystal particle growth with higher symmetry.
Managing the Business (and Engineering) of Environmental Remediation Projects
Authors: Ferries Mark R. , Tyrrell Ken
Published: October 2008

El Paso Corporation (El Paso) has experienced substantial growth and management change over the last decade. Most of that growth has been by acquisition, which has significantly increased the environmental liabilities under management. Meanwhile, the Sarbanes-Oxley legislation was emerging from Congress requiring publicly held companies to increase the sophistication and effectiveness of management controls. This article looks at the significant improvements made to the system of management controls and operating philosophy in El Paso’s corporate remediation department during this important time of growth and development.
Experimental and Numerical Modelling of Pipeline Denting
Authors: Hertz-Cle´mens Ste´phane
Published: October 2008

The main cause of failure for the most transmission pipelines is mechanical damage due to third party activities [1]. Usually, the damage takes form of a dent with an associated gouge. When this type of defect is detected, repair procedures of pipelines operators necessarily implies the removal of the gouge by grinding. This type of defect is considered as critical for the pipeline integrity; however, the importance of the various characteristics of the dent (depth, length, width) regarding pipeline integrity is not well known. To achieve a better understanding of this kind of mechanical damage, Gaz de France has been working on the numerical modelling of realistic defects for several years. This study presents the comparison between the results of experimental and realistic dent creation tests, and the predictions of the associated numerical model. Tests were carried out using different pipelines. All the parameters of the study were chosen in the range of gas transmission pipelines. Dents with gouges were created with Gaz de France Research and Development Division full-scale external damage testing facility: the pipe aggression rig. The tests were simulated with the general-purpose finite element (FE) package Abaqus/Standard 6.4. A good correlation was found between the FE calculation results and experimental data, in term of residual dent depth, load and strain levels measured during the creation of the dent. This study shows that a better knowledge of the mechanical damage induced by third party activity can be achieved with the development of numerical models.
Determination of the Corrosion Rate of a MIC Influenced Pipeline Using Four Consecutive Pig Runs
Authors: Achterbosch Giorgio G. J. , Grzelak Lech A.
Published: October 2008

In-line inspections have been part of the verification of pipeline integrity since the late seventies in N.V. Nederlandse Gasunie. The discovery of external microbial corrosion (MIC) in 1999 in one of the high pressure pipelines changed the inspection policy from inspection of a randomly selected pipeline once every 5 year to an inspection program for the whole high pressure grid (approximately 5.600 km) to be completed in 10–12 years. One of the MIC influenced lines is used to qualify MFL-pig from different suppliers. In the time period 1999–2004 4 different MFL qualification runs have taken place, resulting in 18 excavations. Rather simple calculation of corrosion rates after every pig run indicated values of 0.2–0.3 mm/yr as an average value for the MIC corrosion. After the fourth pig run (5 years after the first) Gasunie decided to determine the corrosion rate also in a more sophisticated way. In coorperation with the mathematical department of the Technical University of Delft statistical analyses were performed. The paper describes how the data from pig runs and excavations was used to extract a suitable subset of corrosiondefects for which the corrosion rate was determined. It was decided to use only these defects that were indicated by all suppliers as external corrosion thereby leaving out defects that were indicated as “mill defect but possibly corrosion”. A second criterion was that a defect has to be reported by at least three of the four suppliers. These criteria resulted in a subset of 52 defects to be analyzed. All of the reported defect depths were corrected for the bias that was determined from the excavation results. The corrected values were then used to calculate the corrosion rate using three approaches: calculation of the corrosion rate for every defect in two ways and calculation of the corrosion rate for the pool of defects assuming a corrosion growth that is linear in time. The average corrosion rate for the defects was in the range of 0.12 to 0.24 mm/yr. Dividing the data set into deep and shallow defects showed that the average corrosion rates for both subsets, 0.23 mm/yr and 0.25 mm/yr, are not significantly different. This underpins one of the assumptions that the corrosion rate is constant. Further discussion within Gasunie is envisaged to determine how these values can be used in the calculation of re-inspection intervals for this line. And at the same time another discussion will focus on whether these values can be used on other lines.
Controlling Surge Due to Shut-Off Fast Closing Valve at the End of an Oil Pipeline
Authors: Wang Wei , Gong Jing
Published: October 2008

Surge will be induced in oil transfer pipeline, due to the changes of transportation materials, operating parameters or pump station equipments. However, the surge induced by Shut-off fast closing valve could be more destructive, for the duration of valve closure time is short, and then the maximum pressure of the surge is much higher, so it’s necessary to control the surge. Based on the characteristic method, this paper establishes a numerical calculation of the accidental Shut-off the terminal fast closing valve at an product pipeline, and simulates the corresponding transient process of pipeline pressure. Upon the upper result, a further research, which combines the boundary condition of surge relief system, is carried out, in order to get the optimal surge control measures through the relief system.
A GIS-Based Spatial and Statistical Analysis on Water Mains Failure—Case Study: Sanandaj – Iran
Authors: Asnaashari Ahmad , Shahrour Isam
Published: October 2008

This paper addresses a new procedure for spatial and statistical analysis of water mains failure. We use this methodology to analyze and predict the spatial behavior of failure on the water mains network. The analysis is based on data from Sanandaj city in Iran over a 10 year period. It includes 395 mains failure which they were geocoded as discrete points. Prediction maps are constructed using different spatial interpolation methods, namely; the Thiessen polygons, the Density estimation, and the Triangulated Irregular Network model (TIN). Thiessen polygons are used for proximity and area allocation analysis of failure points. Density of failure points is calculated for each cell by summing the number of failures in the cell. TIN model generates a surface form interpolation of failure density. The study indicates that the construction of continuous surface from point dataset offers an interesting tool for the prediction of water main failures. It also provides comprehensive spatial information system that can be easily used by utility managers as a decision-support tool to set up and compare strategies for the renewal of water mains.
Assessment of Pipeline Fatigue Crack-Growth Life
Authors: Jaske Carl E.
Published: October 2008

This paper describes an accepted approach for predicting fatigue crack-growth life in pipelines. Fatigue life is computed as the number of cycles for a crack-like flaw to grow from an initial size to a final critical size. This computation is performed by integrating a fracture-mechanics model for fatigue crack growth. The initial flaw size is estimated either from inspection results or by using fracture mechanics to predict the largest flaw that would have survived a hydrostatic pressure test. The final flaw size is estimated using fracture mechanics. Fracture-mechanics models for computing fatigue crack growth and predicting flaw size are reviewed. The anticipated cyclic loading must be characterized to perform the crack-growth calculations. Typically, cyclic loading histories, such as pressure cycle data, are analyzed and used to estimate future loadings. To utilize the crack-growth models, the cycles in the loading history must be counted. The rainflow cycle counting procedure is used to characterize the loading history and develop a histogram of load range versus number of cycles. This histogram is then used in the fatigue crack-growth analysis. Results of example calculations are discussed to illustrate the procedure and show the effects of periodic hydrostatic testing, threshold stress intensity factor range, and pressure ratio on predicted fatigue crack-growth life.
Modeling the Effects of Pipeline Fires and the Response of People in Large Buildings
Authors: Cleaver R. P. , Acton M. R. , Halford A. R.
Published: October 2008

Failures of natural gas transmission pipelines have occasionally occurred around the world. Ignited releases from ruptured high-pressure transmission pipelines produce a highly transient thermal radiation field in the initial stages, as described in papers presented at IPC previously. In the context of risk assessment, modeling the effects of fires on buildings is as important as modeling the thermal radiation field. A simplistic approach may not be appropriate, particularly when there is a significant difference in thermal radiation levels between the nearest and the furthest points of the building from the fire. It is necessary to consider the timescales involved, such as the timescale for fire spread through the building, for the evacuation of people and for the external thermal radiation field to decline. All of these factors need a modeling approach that is commensurate with other uncertainties in the risk analysis. The purpose of this paper is to describe a general modeling approach to assess the effects of transient fire loading on such large buildings. Illustrative examples are given for a large two-storey building and an apartment block. The effects of parameter variations, such as changes in the rate of flow of people through a doorway and the rate of progress of people from one floor to the next, are demonstrated. The results help to establish a method for evaluating the risk to occupants of large buildings. This can be used to support informed decisions on pipeline safety issues and in prioritizing integrity management programs on a risk basis.
Method for Establishing Hydrostatic Re-Test Intervals for Pipelines With Stress-Corrosion Cracking
Authors: Fessler Raymond R. , Rapp Steve
Published: October 2008

Hydrostatic testing is one way to demonstrate the integrity of a pipeline that may contain stress-corrosion cracks. In order to establish appropriate intervals for such tests, it is necessary to make a reasonable assumption about the probable maximum growth rate of cracks that might exist in the pipeline. Although growth rates have been measured in laboratory experiments, those rates are not meaningful for a buried pipeline, because the growth rate depends upon many unknown factors, such as the condition of the coating, the composition of any liquid in contact with the pipe, the susceptibility of the steel, and the temperature. However, it is possible to infer what a probable maximum growth rate is, from the hydrostatic-test history of a portion of a pipeline. This paper describes a method for establishing hydrostatic-test intervals based upon the assumption that cracks that already led to a service failure or hydrostatic-test failure had a higher growth rate than surviving cracks. That assumption is reasonable, because the cracking conditions at the failed cracks must have been more severe than the conditions around any surviving or future crack. The method does not require any knowledge about the nature of the chemical environment at the surface of the pipe, the susceptibility of the steel, or whether the cracks are high-pH stress-corrosion cracks or near-neutral-pH stress-corrosion cracks. The only data that are required are probable maximum values for the actual yield strength and the actual ultimate tensile strength, which usually can be determined from mill records. Using this method, it can be shown that the interval lengths are strongly affected by the test pressure. It also can be shown that uniform test intervals are less effective than graduated intervals. In fact, subsequent intervals may be longer than previous ones, even if hydrotest failures occurred in the previous tests. The validity of this method was demonstrated by applying it, in principle, to actual historical data from over a dozen valve sections that have been subjected to multiple hydrostatic tests and showing that, if this method had been used, more failures would have been prevented with fewer tests.
Field Testing of OSBRA 964 km Pipeline Leak Detection System
Authors: de Almeida Ma´rcio Manha˜es G. , Neto Andre P. Kotchetkoff , Mendonc¸a Adilson S. , Alvarez Ricardo R. , Castro Marcello P.
Published: October 2008

OSBRA is the 964 Km pipeline which supplies over 6.000.000 m3/year of gasoline, diesel oil and LPG to Brazil Mid-West region. Products on OSBRA pipeline are pumped on 24 hours a day and 365 days a year scheduled basis from Planalto Paulista Refinary – REPLAN to 5 midsize cities through 6 remote operated pumping stations located along the pipeline. OSBRA pipeline operation including pumping, valve operation and tank farm monitoring are done remotely from PETROBRAS Transporte S/A – TRANSPETRO Pipeline Control Center - CCO. A real time leak detection system (LDS) was supplied and installed at this Pipeline Control Center. The LDS is based on measurements of flow, pressure and density as well as pump and valve status along the pipeline. A SCADA was implemented and field instrumentation measurements were observed in order to provide good quality data for the pipeline operation and its LDS. Assembling of some field instruments were improved in order to correct measurement fails. On-desk simulations were done in order to verify theoretical system performance and operation team was trained to use the leak detection tool. A field controlled leak simulation test was done in order to validate and verify the System performance. This apparently simple task demanded around 1 year for planning and implementation before test was done. The approach of this report is mainly operational and shows how the OSBRA LDS test was planned, programmed, commissioned and performed. Coordination and integration of Operation, Maintenance, Pipeline, Engineering, Safety, Telecommunication and Logistic teams are demonstrated in order to get good results. Field activities like designing and assembling of spools and instrumentations necessary to execute a controlled pipeline liquid hydrocarbon take off are showed. Safety and environmental precautions to avoid equipment damage, uncontrolled operation or product leak to environment are demonstrated.
High Toughness, Submerged Arc Girth Weld for Northern Pipeline Applications
Authors: Hamad Fathi , Chen Xiande , Collins Laurie
Published: October 2008

Strain-based design, to be used in Northern Pipeline applications, will likely call for the strength of the girth welds to over-match the longitudinal strength of the pipes. As well, a minimum level of weld metal fracture toughness, as measured by Charpy V-Notch (CVN), Crack-Tip Opening Displacement (CTOD) as well as Wide-Plate tests, will be required. The development work done to date, on Submerged Arc Welds (SAW) used to double joint pipes, has resulted in the production of girth welds for large diameter X80 pipes with minimum yield strength above 100,000 psi (690 MPa), Charpy-V-Notch absorbed energy more than 74 ft-lb (100 Joules) at −4 F (−20 C), CTOD greater than 0.006” (0.15 mm) at −4 F (−20 C) and Wide Plate remote strain greater than 4%, at −4 F (−20 C). This presentation will describe the metallurgical approach adopted for promoting high toughness and achieving over-matching yield strength, for strain-based design application.
Prediction of the Location and Duration of Water Condensation in Nominally Dry Gas Transmission Pipelines
Authors: King Fraser , Mason Roger , Worthingham Robert G.
Published: October 2008

Gas transmission companies limit the extent of internal corrosion on their systems by imposing strict gas quality specifications for water and other potential contaminants. However, upsets do occur and water can be introduced from a number of sources. One such source is water vapour in the gas at levels that may be above or below the specification. Water vapour may condense as a thin liquid film on the inner surfaces of the pipe, leading to the possibility of internal corrosion. A model (MHICE Model for Humidity and Internal Corrosion Estimation) has been developed to predict the location and duration of water film formation as a function of various operating parameters. The code predicts the time-of-wetness (TOW) of the pipe wall, which could then be used to predict the extent of internal corrosion using separate corrosion models. MHICE simulates a straight, level pipe with a number of inlets at which moist natural gas can be introduced. Any number of upset conditions can be specified at the main inlet, each described by a background and upset water concentration. Single upsets at up to ten downstream producers can also be simulated. The model accounts for the pressure and temperature drop along the pipe, both of which affect the saturated water vapour concentration or dew point. Water condensation and evaporation is simulated using a mass-transfer coefficient, with the rate dependent on the degree of over- or under-saturation, respectively. The code predicts the spatial and temporal distribution of liquid and vapour-phase water, integration of which gives the TOW along the length of the pipe. A single upset is predicted to move down the pipe as a slug of moist gas with little mixing with the drier gas ahead of and behind the slug. Water condenses at locations where the vapour concentration exceeds the saturation value. The rates of condensation and evaporation are fast compared with the gas velocity, so the wetted region of the pipe wall is predicted to move down the pipe with the slug of water vapour until such point that the gas is no longer super-saturated with water vapour. There is some broadening of the slug due to dispersion and, at the trailing edge of the wetted film, possibly because the rate of evaporation is not instantaneous. Downstream inputs can reinforce or dilute the main upset, depending upon their location, timing, and the level of the upsets.
Interpretation of External Cracking on Underground Pipelines
Authors: Maier Clifford J. , Beavers John A. , Shie Taylor M. , Vieth Patrick H.
Published: October 2008

When external cracks are discovered on underground pipelines, it is sometimes difficult to identify the cracking mechanism. This is especially true when the cracking coincides with local stress discontinuities such as dents, where significant stress fluctuations can occur. Additionally, cracking may initiate by one mechanism and another mechanism may subsequently dominate. For purposes of developing integrity programs for the affected pipeline segment, proper interpretation of the mechanism for crack formation is important. This paper describes the characteristics of, and methods to distinguish between, the common types of time-dependent cracking found on underground pipelines. It also discusses the relationships between the mechanisms for the environmentally assisted cracking phenomena.
Fatigue Crack Driving Force for Axial Surface Cracks in Pipes
Authors: Shen G. , Adeeb S. M. , Coote R. I. , Horsley D. J. , Tyson W. R. , Gianetto J. A. , Bouchard R.
Published: October 2008

Fatigue life assessment procedures require knowledge of the fatigue crack driving force, such as stress intensity factor range (ΔK) and cyclic J-integral (ΔJ), for the flaw geometry detected during inspection. Because three-dimensional closed-form crack driving force solutions are not available for typical flaws in pipelines, it is common practice to obtain these solutions from finite element analysis (FEA) or to adopt a closed-form crack driving force solution for the equivalent flawed plate and include a correction factor to take account of the pipe bulging effect. In the present study, pipes and plates with an axial rectangular crack with filleted corners under fatigue loading are simulated by FEA. The initial results show that the stress intensity factor range (ΔK) for a thin-walled pipe with a shallow crack (a/t < 0.5) is given reasonably well by the bulging factors given in BS 7910 combined with the stress intensity factor equation given by Newman and Raju for a plate with a semi-elliptical crack. However, the stress intensity factor is significantly over-estimated for a long and deep crack using this procedure. Different parameters for elastic-plastic fatigue are calculated and are proposed to be correlated with the rate of crack growth for thin-walled pipes with an axial rectangular crack with filleted corners. It is intended to use the results presented here in combination with full scale experimental fatigue data to obtain pipeline fatigue crack growth formulations, to accurately predict the rate of crack growth within a pipeline due to fluctuating internal pressure.
A New Generation of Pipeline Risk Algorithms
Authors: Muhlbauer W. Kent , Johnson Derek , Hendren Elaine , Gosse Steve
Published: October 2008

While the previous generation of scoring-type algorithms have served us (the industry) well, the associated technical compromises can be troublesome in today’s environment of increasing regulatory and public oversight. Risk analyses often become the centerpiece of any legal, regulatory, or public proceedings. This prompts the need for analysis techniques that can produce risk estimates anchored in absolute terms, such as “consequences per mile year”. Accordingly, a new generation of algorithms has been developed to meet today’s needs without costly re-vamping of previously collected data or increasing the costs of risk analysis. A simple re-grouping of variables into categories of “exposure”, “mitigation”, and ‘resistance’, along with a few changes in the mathematics of combining variables, transitions older scoring models into the new approach. The advantages of the new algorithms are significant since they: • are more intuitive and predictive, • better model reality, • lead to better risk management decisions by distinguishing between unmitigated exposure to a threat, mitigation effectiveness, and system resistance, • eliminate the need for unrealistic and troublesome reweighting or balancing of variables for changes such as new technologies, • offer flexibility to present results in either absolute (probabilistic) terms or relative terms, depending on the user’s needs. The challenge is to accomplish these without losing the advantages of earlier approaches. One of the intent of the new algorithms is to avoid overly-analytic techniques that often accompany more absolute quantifications of risk. This paper will showcase this new generation of algorithms to better suit the changing needs of risk analysis within the pipeline industry.
Analysis of Crack-Like Flaws and Relative Ranking of Pipeline Segments for Prioritizing Mitigation Efforts
Authors: Beavers J. A. , Maier C. J. , Jaske C. E. , Bubenik T. A.
Published: October 2008

In integrity management programs, crack-like indications am sometimes detected on pipelines by means of hydrostatic testing, direct examination, or in-line inspection. Many of these are non-injurious mill defects while some might undergo time dependent growth. Mechanism for growth include fatigue, corrosion fatigue, and stress corrosion cracking. The cyclic pressure fluctuations typically present on operating pipelines affect all three mechanisms of crack growth. This paper describes several methods for assessing the remaining life of pipeline segments containing growing defects.
Implications of Integrity Management Regulations on a Provincially Regulated Pipeline Operator
Authors: Smith Brad
Published: October 2008

Recent changes in Alberta pipeline regulations have created a need for provincially regulated companies to embrace broader quality management principals when considering the management of asset integrity. While larger federally regulated transmission pipeline operators have long been regulated towards this quality management approach, smaller provincially regulated operators, (including Exploration & Production companies with pipeline assets) will now be required to move their integrity management programs in a similar direction. Given the diversity in focus, resources, and business objectives of these provincially regulated energy companies, a simple, focused means to execute this transformation is required. This paper reviews the general processes and specific steps undertaken by Pembina Pipeline Corporation in making this transition towards compliance with the revised EUB pipeline regulations. While the approach and initiatives discussed in this paper relate specifically to Alberta pipeline regulations, the general principals are broadly applicable to pipeline operators seeking to develop compliance with goal-oriented regulation.
Application of ECA Procedures in Integrity Assessments of Ductile Pipes With Axial Flaws
Authors: Ferraboli Roberto , Ruggieri Claudio
Published: October 2008

ECA procedures of crack-like defects based upon the FAD philosophy have undergone extensive developments in the past decade to form the basis for industrial codes and guidelines for structural integrity assessments. However, the application (and validation) of these procedures in defect assessments of structural components made of ductile materials under low constraint conditions remains a potential open issue. A central objective of this work is to assess the capability of the failure assessment diagram methodology to predict the failure pressure of ductile pipes with planar defects having different geometries. Specifically, the present work compares the burst pressure predictions for austenitic steel pipes with axial flaws derived from two widely used FAD procedures: BS7910 and API579. Such an application serves as a prototype for a wide class of integrity assessment problems involving the effects of strain hardening properties and ductility while, at the same time, assessing the robustness of FAD procedures in failure predictions. The direct application of BS 7910 procedure indicate rather large margins between the predicted and the actual (measured) failure pressures. In contrast, the API 579 procedure appears to provide better agreement with experimental data. Overall, the results validate the use of FAD-based methodologies for defect assessments of ductile pipes with axial crack-like flaws.