bluuebunny/crossref_metadata_2025 huggingface dataset:
Full Scale Gas Leak Test at a Large Diameter X-80 DSAW Pipe
Authors: Reepmeyer Oskar , Lothe Per , Valsgard Sverre , Erdelen-Peppler Marion , Knauf Gerhard
Published: October 2008

Compressed Natural Gas (CNG) is an emerging marine transportation technology for natural gas. Knutsen OAS Shipping’s Pressurized Natural Gas (PNG®) System is one of several concepts. PNG® provides sufficient pipeline gas storage volume by pressurizing at ambient temperature without any additional gas treatment. One ship classification society published rules and two other developed guidelines for the approval and classification of this new technology. The idea is already more than some decades old, but today in applying state of the art pipeline technology instead of traditional pressure vessel codes, this technology has become economically viable. The main difference to a pipeline is that the cylinder’s main design criterion is not burst but fatigue due to the frequent charging and discharging process in the transportation chain. For PNG, EUROPIPE supplies assembled cargo tank cylinders. Several successful hydraulic full scale fatigue tests have been carried out in the accordance with the requirements in Det Norske Veritas rules for CNG Carriers. The result was always that a fatigue crack penetrated the cylinder wall creating a leak without break in excess of the required lifetime limits. This local failure mode enables gas detection and safe pressure relief of an effected cargo tank cylinder in operation on a ship. The integrity of a cargo tank cylinder under gas pressure in presence of a gas leak was not investigated during these tests. Due to the leak, gas escapes from the cylinder and the pressure decay leads to a temperature drop due to the Joule-Thomson Effect. It should be determined that a fatigue crack of certain maximum size does not become unstable due to the temperature drop and deterioration of the toughness properties of the material which would lead to rupture of the cylinder. The leak before failure diagrams available to evaluate a critical crack length for a given load were verified in a real environment with decreasing temperature of the escaping gas and the cylinder material. The temperature measurements were used to verify models to determine the temperature profile of the gas and the cylinder material resulting from the Joule-Thomson Effect during blow down. Also the impact of the escaping gas on a cylinder placed adjacent to the leaking cylinder at the same distance as in a ship was measured. This test is not only of interest for CNG cylinders onboard ships, but the results are also of high interest for pipelines transporting natural gas under higher pressure.
Large Pipeline Network Optimization: Summary and Conclusions of TransCanada Research Effort
Authors: Botros K. K. , Sennhauser D. , Stoffregen J. , Jungowski K. J. , Golshan H.
Published: October 2008

Operation of large gas pipeline networks calls for fulfilling variation in contractual volume obligations, and maintaining a certain range of linepack with minimum fuel consumptions to drive compressor units. This is often achieved with either operational experience or by utilization of optimization tools, which results in reduced hydraulic analysis time as well as improved pipeline operation as a whole. The main objective is to accurately identify the optimum set points for all compressor stations, control and block valves in the network, subject to several system and operational constraints. This implies multi-objective optimization of a highly constrained network with a large number of decision variables. Over the past three years, TransCanada has devoted a research effort in developing/integrating an optimization tool based on stochastic methods. It was found that it offers greater stability and is more suited for multi-objective optimizations of large networks with inherently large number of decision variables, than any gradient-based method. This paper describes the nature of the pipeline system under optimization, and discusses the basis for a Genetic-Algorithm-based tool employed. It summarizes the results of the past three years of research efforts outlining the selection criteria for the optimization parameters, integration with a robust steady-state thermal hydraulic simulator of the pipeline network and the notion that dynamic penalty parameters can affect convergence. The methodology is applied to a large gas pipeline network containing 22 compressor stations resulting in 54 decision variables and an optimization space of 1.85×1078 cases. Comparison of genetic algorithm optimization with traditional and manual optimization is demonstrated. Extensive effort has been devoted to reduce the computation time, which includes techniques to utilize various hybrid surrogate methods such as Kriging, Neural Networks, Response Surface, as well as exploitation of parallel processing.
Pipelines or LNG: What is the Future Transport of Choice?
Authors: Grigoryev Y. , Hashim H. F.
Published: October 2008

As worldwide demand for natural gas continues to grow at an increasing rate and certain countries’ indigenous production is either in decline or simply unable to fill the shortfall, more attention is being given to importing gas from the few remaining major exporters. The UK has recently become a net importer of gas, and the US is expected to import as much as 5 trillion cubic feet of gas by 2020, the question that arises is what will be the primary method of delivery in the future? Can LNG alone fill any shortfalls and make interregional pipelines obsolete or will pipelines provide enough volume to stall LNG production? Issues of safety and high capital costs are principle reasons why some projects avoid LNG technology. This paper looks at when LNG may be preferable, and when pipelines are the better method of transport in the context of economics and policy.
Nonlinear Harmonic Monitoring of Gouged Dents in Pipeline Specimens Under Cyclic Loading
Authors: Crouch Alfred E. , Chell G. Graham
Published: October 2008

The only in-line inspection technology commercially available for quantitative evaluation of gouged dents is the geometry pig which cannot discriminate between gouged and smooth dents and has no sensitivity to re-rounded dents. Southwest Research Institute® (SwRI®), has been funded by the US Pipeline and Hazardous Materials Safety Administration (PHMSA) and the Gas Research Institute (GRI) through the Pipeline Research Council International (PRCI), to determine the capability of the nonlinear harmonic (NLH) method to characterize the severity of gouged dents, including those that have been re-rounded by internal pressure. This paper describes the NLH method and presents a summary of results from previous work involving burst tests of gouged dents in 24” pipe as a precursor to the current work that involves experiments with four pressure chambers made from 12-inch line pipe under cyclic pressure changes. In each case, internal scanner hardware, driven from outside the pipe, deployed NLH probes against the pipe inner surface, the gouges being on the outer surface. Analysis of the mapped NLH signals on the inner pipe surface revealed residual strain patterns in the pipe and the strain anomalies produced by gouging. The strain anomalies clearly indicated the presence of the gouges on the outside surface, even when they had re-rounded. The signal maps also indicated the length and width of the gouges whereas the signal strength indicated the residual depth. Data are presented showing that the NLH method is capable of ranking the severity of pipeline gouged dents and their propensity for failure under cyclic loading.
RealSens™: An Advanced Passive Airborne Natural Gas Leak Detection Technology
Authors: Banica Adrian , Sheard Chris K. , Tolton Boyd T.
Published: October 2008

Detecting natural gas leaks from the worlds nearly 5 million kilometers of underground pipelines is a difficult and costly challenge. Existing technologies are limited to ground deployment and have a number of limitations such as slow response, false leak readings and high costs. Various remote sensing solutions have been proposed in the past and a few are currently being developed. This paper starts by describing the remote sensing concept and then will focus on a new technology developed by Synodon scientists. This airborne instrument is a passive Gas Filter Correlation Radiometer (GFCR) that is tuned to measure ethane in the 3.3 microns near-infrared band. With its target natural gas column sensitivity of 50 μm, the instrument is capable of detecting very small leaks in the range of 5–10 cuft/hr in winds that exceed 6 miles/hr. The paper concludes with a description of the service which Synodon will be offering to the transmission and distribution pipeline operators using the new technology.
Using Ultrasound to Gauge Pipeline Internal Corrosion With Coating for ICDA
Authors: Feng Qingshan , Yang Zupei
Published: October 2008

Internal corrosion direct assessment (ICDA) for pipeline enhances the abilities to assess internal corrosion in pipeline and is based on the principle that corrosion is most likely where water first accumulates. ICDA employs the same four-step process as all other direct assessment methods. The important step is direct examinations: the pipeline is excavated and examined at locations prioritized to have the highest likelihood of corrosion. A variety of inservice non-destructive examination processes are available to pipeline operators to inspect for internal corrosion. Manual assessment of internal corrosion is considered more challenging than normal external corrosion assessments since the corrosion feature is not visible and must be interpreted by the ultrasonic response, but in the past ultrasonic test need always remove the coating and then measure on the surface of bare pipe, which brings the measurement point of the pipe body more risk because of weaker quality of patch coating. Recently, advances in the design of ultrasonic corrosion thickness gauges utilizing dual element transducers have made it possible to take accurate metal thickness measurements while coatings need not to be removed. This feature is often referred to as echo-to-echo thickness measurements. Using the ultrasound thickness gauge to measure pipeline internal corrosion while external coatings need not to be removed can keep the integrity of coating, make pipeline operating and monitoring more economical and improve inspection activities to estimate corrosion in pipelines for ICDA. Gauge equipment requirement, Measurement procedures and Accuracy were validated in laboratory. How to arrange the gauge locations, interval test time and data treatment and analysis also are the key steps of ICDA for integrity management.
The New Progress of Drag Reducing Agents in World Research
Authors: Guan Zhongyuan , Shui Biyuan
Published: October 2008

Frictional pressure drop (or drag) restricts the flow of liquid in a pipeline, limiting throughput and requiring greater amounts of energy for pumping. Flow improvers used for reducing drag are commonly referred to in the industry as drag reduction agents (DRA). This article presents the latest achievements in research related to DRA’s mechanism and production. A higher molecular weight of polyalpha-olefin will be obtained by bulk polymerization. There are breakthroughs either in research of solution polymerization of alpha-olefin. The DRA’s post-treating processes become better and approach perfection day and day. Recently non-aqueous drag reducing suspensions have been developed, providing significant advantages over previous water-based suspensions and gel-like solution DRAs. Microencapsulated drag reducing agents should be developed in the future because of its advantages in production, transportation, application and post-treating process. In addition, Reynolds number is the first indication to determine whether drag reducer could work or not in fluid flow in a pipeline system. And dependable injection equipment is an important element in the success of DRA application.
Application of the Combinatorial Inspection Method on the Buried Steel Pipelines in China
Authors: Liu Bing , He Renyang , Zhang Hong , Shuai Jian
Published: October 2008

In general, the pipeline external corrosion direct assessment should be synchronously done by two or more inspection tools. Hence, it is very important to know how to develop the high-efficient and accurate combinatorial inspection techniques for engineering application. In this paper, the advantages, disadvantages and adaptabilities of the existing techniques and instruments are reviewed. Considering the technical difficulties in Chinese engineering practices, five different combinatorial inspection techniques were then brought forward. The proper selection of the combinational inspection technique can be determined by the inspection aim, servicing environment and type of the pipeline, soil, and so on. However, it should be noted that each combinatorial inspection technique can be used most of the time with some demerits. Engineering application showed that the proposed techniques can be directly and efficiently used to assess the pipeline external corrosion.
Testing to Determine Whether a PetroSleeve Can be Used for an Electrical Connection to a Pipe for AC Mitigation
Authors: Smyth Robert J. , Cermak L. E.
Published: October 2008

The use of a mechanical electrical connection to a pipeline is tested to determine its’ viability. Historically, the installation of a cadweld on pipelines has been the method generally accepted for attaching an electrical connection to pipe. Cadwelds are usually serviceable. In the case of accommodating up to 800 amperes of current, up to 3 CAD welds have been used. In addition, there is a general feeling in the pipeline industry to avoid cadwelds, if possible, because they can create a heat affected zone and the possibility of cracking. Where pipelines traverse or parallel high voltage transmission lines, there exists the possibility of voltage and current induction when phase imbalance occurs. These current flows can approach 800 amps. If a cadweld is the main conduct at the pipe surface, burns, high heat, or connection malfunction can occur. This paper describes the testing undertaken to determine if a PetroSleeve installation could be used as a mechanical electrical connection suitable for conducting up to 800 amperes of current. Following the initial testing, three sleeves were installed on operating pipelines for AC Mitigation.
Processing and Properties of an Alternative Alloying Concept for an Export Subsea Pipeline in Grade X70
Authors: Meuser H. , Grimpe F. , Meimeth S. , Liessem A.
Published: October 2008

The Thermomechanically Controlled Rolling Process (TMCP) is used to produce heavy plates for a wide field of applications due to the excellent combination of mechanical properties, strength and toughness properties as well as excellent weldability. In order to achieve these properties lean alloying concepts with microalloying of Nb, Ti and/or V in combination with temperature controlled rolling are used. The basic metallurgical properties are controlled recrystallisation, α/γ grain refinement, phase transformation and precipitation hardening. This paper deals with the evaluation of an alternative alloying concept for a major plate order for the construction of an export subsea gas pipeline in grade X70. The challenge of this project was focussed on the evaluation of an alloying concept which was able to meet the demands of an offshore grade X70 and in addition to fulfil severe requirements regarding weldability and toughness properties. In addition to the aforementioned requirements the alloying concept had of course to be within the restrictions of the customer specification. Before start of production a suitable process design had to be developed in a laboratory scale as well as large scale trials. Special focus was laid on the influence of rolling parameters on the obtained mechanical properties. Therefore different alloying concepts and the achieved mechanical properties as well as temperature ranges for the rolling process will be reviewed and presented. The finally chosen product and process design lead to excellent results which stayed in a very narrow scatter band throughout the mass production of more than 300,000 tons.
Study on the Distributed Optical Fiber Pipeline Leakage Prewarning System and the Method of Signal Analysis
Authors: Qu Zhigang , Jin Shijiu , Zhou Yan , Li Jian , Tan Dongjie , Wang Likun
Published: October 2008

A new distributed optical fiber pipeline leakage pre-warning system based on the principle of Mach-Zehnder optical fiber interferometer and the method of its signal analysis are proposed in this paper. In this pre-warning system, an optical cable is laid in parallel with the pipeline in the same ditch and three single mode optical fibers in the optical cable build up the distributed micro-vibrant measuring sensor. Leakage and other abnormal events can be detected by the sensor in real-time and can be identified by using an “energy-pattern” method based on the wavelet packet analysis. The position of the leak point can be obtained by calculating the value of time delay of the two measuring signals through a correlation algorithm. This system detects various oil and gas pipeline leakages, and is especially suited for micro-leakage. At the end of this paper, experimental data obtained on oil field and the result of the signal analysis are presented. The data and the result of the signal analysis show that the measuring sensitivity and location precision of detecting leakage are improved when this technology is adopted, and abnormal events can be efficiently identified.
Understanding Magnetic Flux Leakage Signals From Dents
Authors: Clapham Lynann , Babbar Vijay , Rubinshteyn Alex
Published: October 2008

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall stresses, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, the combined influence of stress and geometry make MFL signal interpretation difficult for a number of reasons: 1) the MFL signal from mechanical damage is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. Accurate magnetic models that can incorporate both stress and geometry effects are essential in order to understand MFL signals from dents. This paper reports on work where FEA magnetic modeling is combined with experimental studies to better understand dents from MFL signals. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying aspect ratios (1:1, 2:1, 4:1), orientations (axial, circumferential) and depths (3–8 mm) in plate samples. MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress ‘peaks’ tend in most cases to overlap — however stress features are most prominent in the dent rim region and geometry peaks over central region. In general the geometry signal scales directly with depth. The stress scales less significantly with depth. As a result deep dents will display a ‘geometry’ signature while in shallow dents the stress signature will dominate. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.
Full-Scale Laboratory Testing to Assess Methods for Reduction of Soil Loads on Buried Pipes Subject to Transverse Ground Movement
Authors: Karimian Hamid , Wijewickreme Dharma , Honegger Doug
Published: October 2008

A series of full-scale tests were undertaken to examine the effectiveness of the use of geosynthetic materials to reduce lateral soil loads on buried pipelines subjected to transverse ground movements. The testing program consisted of measuring lateral soil loads on steel pipes buried in trenches simulating different native soil and backfill material configurations. The effectiveness of lining the inclined surface of the trench (i.e. “trench slope”) with two layers of geotextile as a method of soil load reduction depends on the formation of good slippage at the geotextile interface. Pipes buried in relatively soft native soil can penetrate into the native soil during lateral displacement, thus causing the geotextile-lining to be ineffective as a reducer of lateral soil loads. Although there is more opportunity for slippage at the geotextile interface when the trench is in relatively stiff soil, the soil loads on the pipe seem to still increase when the pipe moves in close proximity to the trench slope; this effect is likely due to the increased normal pressures on the pipe arising as a result of the presence of the stiff trench in the vicinity of the pipe.
Risk Analysis of Sweet Natural Gas Pipelines: Benchmarking Simple Consequence Models
Authors: Rothwell Brian , Stephens Mark
Published: October 2008

Over the past decades, risk assessment of industrial facilities perceived to present significant potential hazards has become widespread, and in some jurisdictions it has become a regulatory requirement or a societal norm. The application of risk concepts to transportation pipelines has become commonplace, and while qualitative techniques may be sufficient for such purposes as the establishment of maintenance priorities and preliminary route selection, increasing need has been seen for fully quantitative approaches. A considerable range of quantitative methods and models has been developed, but many of them have a high degree of complexity and most are proprietary. There is a need for simple and transparent methods that still yield results that are sufficiently accurate at least for generic assessment; it is recognized that the more complex approaches will usually be required for detailed, site-specific analysis. One source of complexity, for gas transmission pipelines, is the need for a suite of relatively sophisticated, numerical models to estimate accurately the consequences of major gas release incidents, which are transient in nature. To overcome this difficulty, relatively simple, closed-form consequence estimation schemes, based on steady-state approximations, have been proposed and applied. The current study benchmarks the results of one such method against those obtained using PIPESAFE, a proprietary software tool containing a suite of interlinked models developed and validated specifically for gas transmission pipelines. Within certain limits, the simple approach was found to give reasonable, and generally slightly conservative, estimates of safety consequences, expressed in both individual and societal terms.
SCC Inspection and Mitigation Program on Suncor OSPL Pipeline: Field Data Trends and Observations
Authors: Leeson Robert , Spitzmacher Derek K.
Published: October 2008

This paper reviews a recent extensive Stress Corrosion Cracking (SCC) inspection and mitigation program on Suncor Energy’s NPS 16 Oilsands Pipeline (OSPL). The primary focus of the paper will be on the findings, trends, and observations obtained from the actual “as found” field data. Suncor’s SCC management philosophy will also be discussed, including in-line inspection, engineering analysis, data collection and defect mitigation. Suncor Energy owns and operates the 426 km NPS 16” (406.4 mm) OSPL system from the Suncor Oilsands site north of Fort McMurray to Edmonton, Alberta, Canada. The pipeline operates as a batched system and transports a range of products from heavy viscous crude oil, light synthetic crude, naptha and diesel to natural gas liquids (NGL). This pipeline experienced a rupture in August of 2004. The cause of failure was determined to be near-neutral pH Stress Corrosion Cracking (SCC). An extensive excavation and inspection program was undertaken following a comprehensive in-line inspection (ILI) program to detect any crack, metal loss and geometry features. A total of 282 crack field and crack-like features as well as 57 notch-like and non-decidable features were excavated and inspected. A number of trends and observations were identified during the inspection and assessment program. Most of the SCC occurred in an area immediately downstream of a newly commissioned pump station. Also, all SCC was detected in thin wall pipe sections and no SCC was identified in heavy wall pipe sections. Most of the SCC occurred in locations with moderate well to rapidly drained glaciofluvial sands and loamy sands. Field observations and findings along with post rupture metallurgical analysis agreed with recent published developments in the mechanism of near-neutral pH SCC. Suncor completed an extensive integrity program in a relatively short period of time (less than a year). All crack-field and crack-like defects as identified by the UltraScan CD tool were mitigated. Suncor plans to continue their integrity program to ensure the continued safety and integrity of their pipeline facilities.
Offtaking Scheduling Software for Multi-Product Pipeline
Authors: Liang Yongtu , Gong Jing
Published: October 2008

The main objective of this work is to exhibit the functions of a software program that prepares offtaking schedules for multi-product pipelines. The software program is currently being used on two multi-product pipelines in China. In the paper, the pipeline system modeled in the software involves several offtaking stations, pump stations, and one multi-product pipeline connected to several depots that distribute large amounts of oil products to customer markets. The background for developing this software is presented and the mathematical model utilized in the software will be given. The software can track the interface positions on the basis that the liquid is incompressible and transported adiabatically in the pipeline — the density doesn’t vary with pressure and temperature. In the model, the author adopts the advantages of variable paces to speed the calculation in the Master-Clock Method and adds interfaces’ reaching stations to the set of control points, while honoring handling contamination only at terminal station and keeping turbulence flow all time. Finally, a real-world application on the Lan-Cheng-Yu Multi-product Pipeline (LCYPP) is introduced. This is the first real test on a multi-product pipeline in China. Through the application, the characteristics and functions of the software is reported. The software provides users with a diagram for batch movement, the interface timetable, the scheduling table, the interface size, and so on. The application shows that the software is successful.
Leak and Break Models of Ductile Fracture of Pressurized Pipe With Axial Defects
Authors: Orynyak I. V.
Published: October 2008

The significance of the analytical modeling for limit load calculation of the defected pipe is outlined. The distinction between the notions of the “local” and “global” limit load is discussed. The number of simplified models for the surface axial crack, 3-D rectangular defect, through axial crack are developed which are based on the construction of the statically admissible solution. Based on them the boundary between the leak and break behavior of the pressurized pipe with the surface crack is obtained. The results of calculation are compared with experimental full-scale testing of the defected pipes.
Simulation of the Process of Drawing a Pipe Through the Pipeline With a Larger Diameter
Authors: Orynyak Igor V. , Bogdan Andriy V. , Vasylyuk Volodymyr M.
Published: October 2008

A numerical model to calculate drawing forces and determine the contact forces of interaction of the inner pipeline with the pipe of a larger diameter has been developed. The module takes into account the complicated geometric profile of the outside pipe, the possibility of loss of contact by support rings, the mass of the inner pipeline and the action of buoyancy force, longitudinal and transversal (due to sag) force from the pulling rope, the compliance of the pipe-ring system, etc. The results of calculation were used in determining the interval of the rings disposition and the choice of their dimensions (height). Described is the effect of a tensed string when the increased coefficient of friction entails a nonlinear growing increase of drawing force.
Experimental Study of Charpy Impact Characteristics of High-Strength Spiral Welded Gas Pipeline
Authors: Hashemi Sayyed H. , Jalali Mohammad R.
Published: October 2008

Charpy upper shelf energy is widely used as a fracture controlling parameter to estimate the crack arrest/propagation performance of gas transportation pipeline steels. The measurement of this fracture criterion particularly for modern steels and its apportion into different components (i.e. fracture and non-related fracture energy) are of great importance for pipeline engineers in order to transfer laboratory data from Charpy experiment to real structure. As the conventional Charpy impact test has only one output (i.e. the overall fracture energy) the instrumented test has been used to achieve full failure information from impact test samples. In this paper the results of instrumented Charpy impact experiments on high-strength spiral welded pipeline steel of grade API X70 are presented. First, the instrumentation technique including the design and implementation of a strain gauge load-cell and the details of the data-recording scheme are reviewed. Next, the experimental data obtained from the Charpy impact machine so instrumented are given. These include test data obtained at room temperature from different sets of standard full size Charpy V-notched specimens taken from the pipe material, seam weld and heat affected zone (HAZ). The instrumented Charpy machine was able to capture the load history in full during the fracture process of the test specimens resulting in a smooth load-time response. This eliminated the need for filtering used in similar test techniques. From the recorded test data the hammer displacement, impact velocity and fracture energy were numerically calculated. The numerical results showed good agreement between the instrumentation data and those read from dial indicator. From fracture energy plots it was found that the maximum and minimum fracture energy were associated with the pipe material and seam weld (in average), respectively. In all test samples a significant amount of energy was consumed in non-related fracture processes including crack initiation, bending and gross deformation of test specimen, and indentation at the support anvils and at the impact point. This non-related fracture energy should be accounted for if the current failure models are going to be used for toughness assessment of high-strength low-alloy gas pipeline steels.
Effects of Geometric Imperfection on Bending Capacity of X80 Linepipe
Authors: Suzuki Nobuhisa , Kondo Joe , Endo Shigeru , Ishikawa Nobuyuki , Okatsu Mitsuhiro , Shimamura Junji
Published: October 2008

Validation of finite element modeling to predict bending capacity of linepipes and effects of geometric imperfection on the bending capacity are presented. A bending test of an X80 linepipe was conducted to discuss the validation and investigate the effects. The geometric imperfection of the linepipe about the outside diameter, the wall thickness and the longitudinal blister of the linepipe was measured in the round. Consequently, the results obtained by FEA taking into account the geometric imperfection present good agreement with the experimental data. And the moment capacity is virtually independent of the geometric imperfection however the strain capacity of the linepipe is quite susceptible to the geometric imperfection.
A Quantified Risk-Based Design Assessment of a Localized ‘Pinch-Point’ on the Proposed Route of a High-Pressure Natural Gas Pipeline
Authors: Francis Andrew , Jandu Chas , McCallum Marcus
Published: October 2008

Our Client was commissioned to construct an onshore high pressure gas pipeline. The pipeline was to be about 50km in length, 1066mm diameter, 15.88mm nominal wall thickness and constructed from X65 material. During the route selection phase it was discovered that it would be very difficult to avoid passing the pipeline through a locally highly populated area. In view of this it was naturally decided that the pipeline should be constructed from heavy wall sectioned pipe to mitigate the threat of failure due to causes including mechanical damage and corrosion. However, there was still a concern that the residual risk, even when the above mitigating measure had been taken, would still be unacceptably high. In view of this Andrew Francis & Associates Ltd (AFAA) were commissioned to assess the remaining risk levels using a quantified risk assessment technique in accordance with the UK pipeline design code, IGE/TD/1 Edition 4, which provides for the use of such techniques. The technique used by AFAA involved detailed Structural Reliability Analysis (SRA) combined with an assessment of the consequences of failure. AFAA began the study by identifying the possible failure modes and these included mechanical damage, external corrosion, fatigue crack growth and AC induced corrosion. However, discussions were held between AFAA and the Client and after giving due consideration to the benefits of modern construction standards, and the use of Fusion Bonded Epoxy (FBE) coating, it was agreed that the only significant threat to integrity was mechanical damage. AFAA used SRA to determine the likelihood of failure due to mechanical damage based on a state-of-art-limit state function taking account of key areas of uncertainty including variations in defect dimensions and material properties. A consequence model was used to determine the possible effects on the local population if a rupture of the pipeline was to occur. The consequence model was used to determine the amount of thermal dose that personnel, in the vicinity of the release, might receive, taking account of the transient nature of the gas flow. The mitigating effects of nearby buildings that would afford shelter from the effects of the thermal radiation levels were naturally taken into account. The results were expressed in terms of an F/N curve and assessed against the risk criteria contained in IGE//TD/1. It was concluded from the analysis that the proposed design did not pose an unacceptable level of risk and moreover that part of the proposed heavy wall section was unnecessary. However, in the interests of conservatism our customer proceeded with the original design. This paper describes the modelling technique used by AFAA and clearly presents the results and conclusions of the analysis.
A New Probabilistic Model for High-pH Stress Corrosion Cracking
Authors: Francis Andrew , Jandu Chas
Published: October 2008

Stress corrosion cracking (SCC) poses a threat to integrity of buried pipelines in many parts of the world. In North America there is now a requirement that integrity management plans should address SCC and a direct assessment methodology, SCCDA, for managing the threat due to SCC, is now becoming established. Like general corrosion or fatigue, SCC is a time dependent deterioration process that leads to progressive weakness of the pipe wall eventually causing failure as a leak or rupture, if not managed. There are indeed two known forms of SCC; High-pH and near neutral-pH SCC. The focus of this paper is on High-pH SCC. High-pH SCC involves a number of phases including incubation, initiation, anodic growth, coalescence, mechanical growth and final failure. Factors affecting these processes include temperature, static and cyclic stress, soil conditions, type of coating and level of Cathodic Protection. Some of these factors may vary seasonally. The temporal development of SCC damage is thus both complex and subject to significant uncertainty. The purpose of this paper is to describe a detailed probabilistic model that addresses the various phases of High-pH SCC taking account of uncertainty in the relevant influencing factors. The model determines the likely times to coalescence and to grow to a critical size thus providing a time dependent probability of failure. The model gives a clear indication of which parameters should be managed in order to reduce the likelihood of failure to an acceptable level. The model provides the basis of a powerful decision making tool for the purpose of managing High pH SCC. Consequently, the model can be used in conjunction with relevant in-line inspection data and/or above ground survey data to provide an effective SCC integrity management tool. The model is illustrated through a numerical example and the use of the model as an integrity management tool is clearly demonstrated.
Stress, Strain and Plastic Instability of Internally Pressurized Pipes With Axis-Symmetric and Narrow Volumetric Flaws: Analysis and Experiments
Authors: Cunha Se´rgio B. , Netto Theodoro A. , Neto Francisco Q. , Pinto Olivier S. X.
Published: October 2008

The mechanical behavior of internally pressurized pipes with volumetric flaws is analyzed. The two possible straining modes are identified and each is studied by means of an idealized flaw: the bending strain is associated with axis-symmetric flaws and the membrane strain to narrow axially oriented flaws. Linear elastic shell solutions for stress and strain are proposed. The plastic behavior is studied and equations for predicting the pressure at which the pipe fails by plastic instability are developed. The analytical solutions were validated by comparison with finite element simulations and burst tests on 3” diameter pipes. Two materials with very dissimilar plastic behavior, low carbon steel and austenitic stainless steel, were used on the experiments. Twenty-nine burst testes were carried out with pipe sections with axis-symmetric flaws and twelve were performed on pipe sections with narrow flaws. The analytical models for stress and strain agreed well with the numerical model, and both the analytical and the numerical predictions showed good correlation with the experimentally observed burst pressures.
Assessment of Success Biostabilization Techniques on Selected Watercrossings in Alberta
Authors: Lees Albert , Jalbert Andrea , Traverso M.
Published: October 2008

Since the early 1980’s TransCanada PipeLines Ltd. (TransCanada) has employed a number of stream bank stabilization measures in an effort to minimize the loss of fish habitat and to reduce the risk of long term erosion and sedimentation. Traditional stream crossing stabilization involved the re-contouring of streambanks to a stable slope (generally 2:1) and then lining the banks with rock armour and seeding. TransCanada began using alternate techniques, primarily log-walls in 1981. Since 1981 TransCanada has evolved the use stream bank stabilization techniques to include bio-stabilization techniques such as live log-walls, fascines, live staking, and brush layering in combination with more traditional structures. In 2004, TransCanada initiated a two year project to assess the success of biostabilization techniques used on a number of watercrossing throughout the its’ Alberta System. A total of 22 stream crossings were assessed in 2004 and 24 in 2005. Sites assessed were located the foothills and boreal forest areas of Alberta. In the majority of cases the biostabilization methods utilized were still intact and functioning as planned by providing stable streambanks and fish habitat. Several factors appeared to be influencing the value of the measures employed. Cattle grazing on sites where fencing did not exclude cattle from the crossing site resulted in destruction or reduced value of the measures employed. Uncontrolled All Terrain Vehicle activity resulted in a reduced value of the measure employed. Implementation of biostabilization techniques in the winter months (frozen ground conditions) created challenges in implementation of biostabilization measures resulting in less favorable results compared to other sites constructed in early and late fall. Seeding to control surface erosion also appeared to affect overall success of woody vegetation used as part of the biostabilization techniques. Biostabilization techniques employed by TransCanad have been effective in stabilizing watercrossings and providing fish habitat. In designing biostabilization systems for watercrossings consideration should be given to overall stabilization objectives, stream flow information, fish and fish habitat values, and likelihood of success given the geographic region, timing of construction, and surrounding land-use pressures.
The Effects of Soil Properties on the Fracture Speeds of Propagating Axial Cracks in Line Pipe Steels
Authors: Rudland D. , Wilkowski G. , Rothwell B.
Published: October 2008

The ductile fracture resistance of newer line pipe steels is of concern for higher grade/strength steels and higher-pressure pipeline designs. Although there have been several attempts to make improved ductile fracture arrest models, the model that is still used most frequently is the Battelle Two-Curve Ductile Fracture Arrest Model, which incorporates the gas-decompression behavior with the fracture toughness of the pipe material to predict the minimum Charpy energy required for crack arrest. For this model, the effect of backfill on the propagating crack fracture speeds is lumped into one empirically based “backfill coefficient,” which does not distinguish different soil types or strengths. Some modifications to this backfill coefficient have been proposed for frozen soil as a function of moisture content, and for water backfill for offshore applications, but no attempt has been made to quantify the effects of soil type, total density or strength on the fracture speeds of propagating cracks in line pipe steels. This paper presents the results from a series of small diameter pipe burst tests that were conducted with different soil backfills. The soils’ moisture content, density, and strength were fully characterized in situ and in the laboratory. In addition, fracture speed data in both unbackfilled and backfilled conditions were recorded. The comparison of the change in fracture speed as a function of soil type, moisture and strength gives valuable insight into the effects of soil on the arrest of running ductile fractures in line pipe materials.
X120 UOE Linepipe With Improved Properties and Varied Sizes
Authors: Asahi Hitoshi , Hara Takuya , Tsuru Eiji , Morimoto Hiroshi , Terada Yoshio , Sugiyama Masaaki , Murata Masahiko , Doi Naoki , Ayukawa Naoshi , Akasaki Hiroo
Published: October 2008

Nippon Steel has developed X120 UOE linepipe as a part of joint development program with ExxonMobil. After establishment of the basic production technology of X120, the mechanical properties have been improved, especially to increase the suitability to strain based design application and the size range has been expanded. The combination of heavily deformed austenite grains and a mild accelerated cooling to lower cooling stop temperatures (MAC) achieves the aim to lower the yield strength (YS) and the yield to tensile (Y/T) ratio for the B-containing chemistry that was decided to meet the CG-HAZ toughness target. The properties of MAC pipes met the targets and the pipes with OD from 28” to 48” and WT from 13mm to 20mm were made for test purpose.
Pipeline Risk Assessment by Bayesian Belief Network
Authors: Ogutcu Gokcen
Published: October 2008

This study focuses on identification of risk factors in pipeline system and also, concentrates on identification of relationship between parameters. In order to achieve this purpose, Bayesian Belief Network with historical data was used to provide a framework for assessing risk relative to the company’s petroleum pipeline system. Each of the variables in the Bayesian Belief Network is described by nodes and each node has a state. Relationships between parameters are presented by arrows. Probability of any node being in state was shown in conditional probability tables. Historical data were helpful to build conditional probability tables. Variables were defined as corrosion, third party damage, mechanical and operational failure.
The Role of Niobium in High Strength Oil and Gas Transmission Linepipe Steels
Authors: Stalheim Douglas G. , Jansto Steven G.
Published: October 2008

Niobium’s role in the production of oil and gas transmission pipelines steels has gained significant importance in recent years. The economical movement of gas and oil to the marketplace from remote and rugged locations requires transmission pipelines to be designed to operate at higher pressures with improved toughness over a variety of temperature ranges. With the increased demand for energy resources continuing to grow, traditional plate mills, hot strip mills along with Steckel mills around the world are processing skelp for API pipe. The capabilities of these mills can be quite varied. Consequently, a variety of operational considerations and practices have put additional focus on Nb for its ability to retard recrystallization at elevated temperatures. This ability has added a new form of processing skelp for API pipe called High Temperature Processing or HTP. This new use of Nb in higher strength API oil and gas transmission pipeline steels allows a producer to create a ferrite/acicular ferrite microstructure without the traditional molybdenum alloy based design. The HTP Nb microalloy approach has benefits including reduced operating cost per ton, ease of rolling and welding, excellent low temperature toughness properties and high strength. This processing technique for API X70 and X80 is gaining acceptance as major pipeline projects are now applying this technology. In addition, X100 properties have been achieved with a combination of the traditional X80 alloy design and the newer employed HTP alloy design. This paper will discuss Nb’s role in meeting the increased strength requirements related to operating at higher pressures, improved low temperature toughness (TCVN > 200 J@−40 °C), microstructural demands and processing capability improvements for traditional plate, strip, and Steckel mill technology. The use of the new HTP concept in high strength API production will also be introduced.