bluuebunny/crossref_metadata_2025 huggingface dataset:
Availability and Risk Analysis Effects on Gas Pipeline Tariff Making
Authors: dos Santos Sidney Pereira
Published: July 2009

On a competitive market gas transportation rates must be as low as possible while recovering capital expenses — Capex and operating and maintenance expenses — Opex at a return rate expected by the project sponsors to recover their investment. To guarantee project feasibility, designers must be concerned not only with technical and direct economic aspects but should also incorporate availability and economic risk analysis to make sure that under operating conditions along the economic life of a project the cash flow will be kept inside predicted values and therefore will not expose project sponsors to undesirable negative Net Present Values — NPV. This paper will present a methodology to address these important aspects with focus on pipeline economics. Pipeline availability study associated with compressor stations failure analysis will be evaluated under Monte Carlo simulation and consequently their impacts on gas pipeline capacity will be economically evaluated. Quantitative economic risk analysis using Monte Carlo simulation is part of the methodology. The adoption of this methodology allows committing more pipeline transmission capacity to a level close to maximum without exposing the Transporter to losses of revenue and contractual penalties. Also prevents designing an oversized and less competitive system with unused spare capacity and consequently higher transportation rates.
Performance Analysis of Turbine Meter and Ultrasonic Meter
Authors: Da Roz Fa´bio , Vini´cius B. Nunes Marcus , Ce´sar de M. Palhares Ju´lio , Flora Alves Pinto Nancy
Published: July 2009

The performance analysis of Turbine - Type and Ultrasonic natural gas flowmeters installed in series in the same stream. The instruments were connected to flow computers for a period of 18 months. During this time all measured differences between the Ultrasonic flowmeter and the Turbine flowmeter were recorded. The performance between instruments is presented in graphs. Throughout this time all system maintenance events were recorded.
A Framework for Managing the Threat of SCC and Other Forms of Cracking in Pipelines Using In-Line Inspection Tools
Authors: Limon-Tapia Sergio , Katz David , Beuker Thomas , Do¨scher Claus , Brown Bryce
Published: July 2009

The phenomenon of Stress Corrosion Cracking (SCC) as a major integrity threat has been investigated intensively and discussed since the 1970’s. Based on the far-reaching understanding of this threat today, integrity management programs have been developed further in recent past. A framework approach is proposed of dividing the integrity management into a process-based structure. Within this structure the different processes from the inspection program to the control of the immediate and future integrity are arranged in a closed loop. The framework has been applied to a Williams 26-inch gas pipeline. The pipeline has been inspected with a high resolution in-line inspection tool, using electromagnetic acoustic technology (EMATs), with a sensitivity to coating disbondment and SCC, proven by detailed results obtained from pipe samples containing SCC. In preparation of an extensive in-field evaluation program, an engineering critical assessment and a risk based analysis of limit conditions are conducted. The results from the in-field program are used to support the subsequent process of tool performance validation and integrity control.
Projective Noise Reduction Algorithm for Negative Pressure Wave Signal Processing
Authors: Yu Dongliang , Zhang Laibin , Wei Liang , Wang Zhaohui
Published: July 2009

The appearance of a rupture, leak or damage in the long-distance oil & gas pipeline, which could cause a leak, usually generates a non-linear & chaotic negative pressure wave signal. By properly interpreting the negative pressure wave signature, it is possible to detect a leak along the pipeline. Most traditional noise reduction methods are established based on the linear system, which are not in line with the actual non-linear & chaotic situation. Therefore, the weak negative pressure wave signals, generated by small leaks, are often filtered out and cause false alarm and failure alarm. In order to resolve the problem, this paper uses the non-linear projective algorithm for noise reduction. First, the weak negative pressure wave signal series would be reconstructed using delay coordinates, in the high dimensional phase space, the background signal, the negative pressure wave signal and the noise signal are separated into different sub-spaces. Through the reconstruction of sub-spaces, the weak pressure wave signal can be isolated from the background signal as well as the random noise component reduced.
Field Experience With On-Line Monitoring of Biofilm Activity
Authors: Licina George J.
Published: July 2009

Piping reliability is critical to oil production, oil sands processing, refineries, power plants, pulp and paper mills, and various other industries. Corrosion, including Microbiologically Influenced Corrosion (MIC), is a primary degradation mechanism in pipelines. MIC of pipeline materials has been shown to occur in virtually all water systems and has caused expensive unplanned outages, the need for local repairs, and, in some cases, complete system replacement. The control of biofilm on surfaces is the most effective tool for mitigating MIC. Effective monitoring for biofilms also helps to avoid the overuse of oxidizing biocides. Biocide overdosing will increase corrosion and can produce catastrophic corrosion effects. Optimized treatments require accurate, on-line monitoring of biofilm activity. Plant experience with an electrochemical biofilm sensor with integrated data acquisition and data analysis capabilities for monitoring biofilm activity on metallic surfaces and the use of that tool for optimizing biocide additions in a variety of environments is described.
Evaluation of Fracture Initiation Energy in API X65 Pipeline Steel
Authors: Hashemi Sayyed H. , Jalali Mohammad R.
Published: July 2009

In this paper, energy absorption characteristics of spiral welded gas pipeline steel are investigated under impact loading. Emphasise is given to energy consuming processes before fracture propagation in tested linepipe steel. The API X65 grade pipe was produced (by Sadid Pipe and Equipment Company) from thermo-mechanical controlled process (TMCP) coils supplied by a Korean steel mill. To measure material impact toughness, an instrumented Charpy machine was used. Experiments were conducted at room temperature on different sets of standard full size Charpy V-notched specimens taken from the pipe material, seam weld and heat affected zone. 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 was associated with the pipe material and seam weld, respectively. In all test samples, a significant amount of energy was consumed in non-fracture related processes including indentation at the support anvils and at the impact point, bending of test specimen and crack initiation. From this finding, correction factors were suggested to account for considerable energy level of non-fracture related processes. This energy had been ignored apparently in conventional pipeline failure models calibrated in the past on low toughness pipe materials in which fracture initiation energy was negligible. The paper concluded with a comparison of suggested correction factors with those obtained by full-scale burst experiments on tough pipeline steels.
Application of Dynamic Programming in Long-Range Pipeline Facility Planning and in Assessing Off-Design and Off-Flow-Forecast Trajectories
Authors: Botros K. K. , Foy C. , Chmilar B.
Published: July 2009

Dynamic programming (DP) inherently provides a methodology for evaluating a series of decisions in order to determine an optimal policy or path forward. The methodology basically enumerates and evaluates alternative states over the planning horizon in formulating the optimum strategy. In the present work, the concept of DP has been applied to pipeline long-range facility planning problems, and further extended to allow evaluation of nth optimum pipeline facility deployments based on cost and/or probabilities of constraints. The best four options were further analyzed considering uncertainties in the cost elements and the resulting economic risk associated with each optimum path. This paper presents the theory behind the extension of the DP methodology to pipeline long-range facility-planning problems over a planning horizon that considers inherent uncertainties in gas supply and demand as well as a range of available facility options. Uncertainties in the size and location of the required facilities to handle the forecast volumes, and associated variances in their respective cost to build and operate the various facilities, are all accounted for. The problem is further complicated by the possible changes in the expected flow from that forecast during design and the resulting penalties associated with the under- or over-sizing of facilities. It was demonstrated that it is important that the off-design flow forecast be evaluated to determine the impact of future variability or changes. The value that the organization can derive from being able to quantify the benefit (or penalty) of forecast uncertainty and over- or under-building long-range facilities, is significant.
Study of Fatigue Crack Growth Rate for X52 Pipeline Steel Under Overload Application
Authors: Chen Yingfeng , Liu Wenjuan , Lu Minxu
Published: July 2009

The effect of overload on fatigue crack growth rate for X52 pipeline steel was studied under different stress ratio and overload ratio. The results show that tensile overload causes a delayed retardation to fatigue crack growth. The crack propagation curve after overloading includes three processes: accelerated growth, retardation growth and recovery growth. Under a constant stress ratio, plasticity induced crack closure is more significant with the increase of overload ratio; the crack growth rate is decreased as a result. However, crack growth retardation is more significant at a lower stress ratio. SEM analysis of the fracture surface shows that the overload plastic strain suffered more erosion at a higher overload ratio and the fracture surface morphology is more different after a higher overload ratio.
Effect of Micro-Texture on Fracture Separation in X80 Line Pipe Steel
Authors: Li Yang , Han Xinli , Ji Lingkang , Feng Yaorong , Huo Chunyong
Published: July 2009

During tests on pipe and steel for the 2nd west-east gas pipeline project (WEPP) in china, fracture separation was found in X80 line pipe steel plates in tensile tests, charpy impact tests and DWTT tests. In this paper, fracture separation is investigated by using EBSD technique to analyze microstructure and compare it with microstructure transformation of the material after annealing. Results show that there are obvious texture of {111} <110> and {110} <001> in hot rolling plate, but a reduction of this two textures and a new texture of {110} <111> are found after annealing at 700°C for 2 hours. It is found in charpy impact tests that {111} <110> micro-texture as a main factor leading to fracture separation was eliminated in annealed specimens. The average grain size of specimen changes from 2.2687μm to 2.8362μm comparing with hot rolling plate because of the decomposition of Bainite. Results of Orientation Imaging display that the proportion of substructure and the distribution of misorientation of grain boundary of annealed specimens do not changed remarkably in contrast to the original ones. It is concluded that, X80 steel has well heat stability.
Safety Assurance of the Heated Waxy Oil Pipeline in Repair
Authors: Wang Xiaomei , Chen Guoqun , Shi Lei , Zhang Zheng , Zhao Zihua , Zhang Yongsheng
Published: July 2009

To ensure the safety of heated waxy crude oil pipeline with in-line rehabilitation, the allowable exposed length and the impending length of the pipe will be respectively determined by using the thermal and hydraulic calculation method for buried heated crude pipeline and Safety Assessment for In-service Pressure Vessels with Defects. In addition, with the elastic foundation beam model, safety measures of backfilling with sand compacted are proposed based on the calculation of the pipe bending stress distribution after backfilling. In this research, a software package has been developed to compute the reasonable exposed length and the impending length of the pipeline in any position and operating condition. The obtained results with comprehensive considering most of key factors are reliable and reasonable which brings the advantages of safety and economy. The technical parameters and manuals obtained have been successfully applied to guide the in-line rehabilitation of China’s Northeast pipeline system.
Integrating GIS and Data Management Within the Project Environment
Authors: Guerrero Hugo
Published: July 2009

Today, much of the focus on integrating Geospatial technology and data has been on the operations side of the business. Not much attention has been paid to the workflow within the project environment even though most of the data that is used to populate enterprise datasets is created or prepared as a requirement of a project; that said; it is early on at the project level when geospatial integration needs to be implemented and incorporated into the project workflow. On the other hand, project teams have historically focused on strictly satisfying the needs of the project. This is typically limited to the minimum work required to design, permit & build a given work scope. This approach has left many companies with the task of paying high costs for the project data to be translated, captured or in some cases recreated after the fact. Too many times, Gas Company X hires multiple consultants with different disciplines responsible for different project scope items (i.e. Environmental, Right-of-way, Engineering, etc...). Each company has established methods for preparing and organizing their respective data without ever thinking how Gas Company X intends on using the data for other enterprise needs during the project and after the project has been completed. This presentation outlines methods by which companies can require that their project consultants produce project data with geospatial integration in mind. This includes identification of required resources & workflows to specify and manage the data that is prepared and/or collected in a structured environment that is geospatially & data aware.
Bioremediation of Soil Contaminated by Crude Oil in Daqing, China
Authors: Zhang Yiling , Kong Dehong , Sun Sheng , Luo Zhiguo , Luo Peng
Published: July 2009

Bioremediation of soil contaminated by pipeline spills in the Daquin region of China is presented in this paper. The objective of the study was to determine the nutrient ratio required for the bioremediation of soil contaminated by Daqing crude oil. Several experiments were conducted using different proportions of C:N:P:K to choose the optimum ratio of nutrients to be applied for bioremediation, C is supplied from the crude oil in the contaminated soil. The moisture content, porosity, PH and temperature of the contaminated soil were adjusted for optimum conditions. The experimental bioremediation technology was conducted in a treatment unit that was 0.5 m in length, 0.7 m in width, and 1.5 m in height. The results showed that the degradation rate of Total Petroleum Hydrocarbons (TPH) increased with increased concentrations of crude oil in the soil. At the beginning of the bioremediation experiments, the degradation rate of THP is high, but it gradually slowed over the course of the experiment. The degradation rate of TPH averaged 98% over 8 months.
Improvement of Toughness of API X65 ERW Pipe Welds
Authors: Ham Yoonjin , Kim Sanghoon , Lim Jeongho , Lee Changhee
Published: July 2009

This study aims to evaluate the microstructure evolution and toughness improvement of API X65 steel ERW pipe welds through heat treatments. Heat treatment schedules of one step process (Normalizing) and two step process (QT: quenching and tempering) were tried to control the properties in the ERW welds and were simulated by Gleeble simulator. In as-welded specimen, metal flow and elongated vertical pearlite have been found at the as-welded bond line, and the microstructure consisted of bainite, Widmansta¨tten ferrite and elongated pearlite. The microstructures of the bond line were changed to polygonal ferrite and elongated pearlite after normalizing. Meanwhile, tempered martensite was found at the bond line after QT process and metal flow and elongated pearlite were disappeared. Charpy impact toughness of transverse specimens has shown that toughness of the as-welded bond line decreased with comparing to that of base metal, which is due to the microstructure degradation. While, toughness in the welds was remarkably improved by all heat treatments; in addition, it has been observed that normalizing treatment of them was the most effective to improve toughness in the API X65 steel ERW pipe welds.
Metallurgical Design and Development of High Deformable X100 Line Pipe Steels Suitable for Strain-Based Design
Authors: Hara Takuya , Terada Yoshio , Shinohara Yasuhiro , Asahi Hitoshi , Doi Naoki
Published: July 2009

The demand for natural gas using pipelines and LNG to supply the world gas markets is increasing substituting for oil and coal. The use of high strength line pipe steels provides the reduction of cost of gas transmission pipelines by enabling high-pressure transmission of large volumes of gas. In particular, high strength line pipe materials with a yield strength of X80 or higher have been developed over the last few decades around the world. Long distance gas transmission pipelines from remote areas sometimes pass through discontinuous permafrost, and are subject to ground movements by repeated thaw subsidence and frost heave. In this case, strain-based design has been applied as well as stress-based design. Therefore, high deformable line pipe is required for strain-based design in order to prevent the pipeline from fracturing. Nippon steel has also developed high deformable high strength line pipe material suitable for strain-based design. In recent years, demand for high strength line pipe steels has emerged in which the molybdenum content is reduced because of the high cost of molybdenum. Conventionally, high strength line pipe steel with Mo addition has been developed in order to control the microstructure and to obtain pipe properties such as strength and low temperature toughness. This paper describes the metallurgical design and development of high deformable high strength X100 line pipe with lower Mo content suitable for strain-based design. High deformable X100 line pipe with 16 mm wall thickness as well as good low temperature toughness and seam weld toughness has been developed.
Numerical Simulation of the ‘Floating Spiral’ Pipeline Installation Procedure: First Stage, Spiral Assembly
Authors: da Silva Danilo Machado Lawinscky , de Lima Mauro Henrique Alves , Albrecht Carl Horst , Jacob Breno Pinheiro , Torres Fernando Gomes de Silva , de Medeiros Antonio Roberto
Published: July 2009

The underlying concept for the Floating Spiral pipeline installation method is to wind the pipeline into a huge floating spiral, and then tow this assembly to the installation site, where the spiral is then unwound and lowered to the seabed in a single operation. In this method the pipes are fabricated on shore, which allows for optimal control of costs and quality in pipeline manufacturing. The first stage of the installation process by this method consists in setting the pipeline afloat and winding it elastically to form a large flat spiral, which is then ready to be towed to the installation site by standard tugboats. The objective of this work is to present results of studies for a long pipeline length at this first stage of the Floating Spiral method. The focus here is the process of moving the pipeline around a fixed structure to wind it and form the floating spiral. Problems related to modeling of contact between pipeline and its guides at the first spiral cycle, as well as contact between further pipeline cycles, are rigorously analyzed. Several numerical simulations are performed; the results are presented and discussed. Other stages of this installation method have also been studied, and are presented in a companion paper [1].
Failures of Welding Repaired Pipeline
Authors: Shuai Jian , Wang Xiaolin , Wang Xiaomin
Published: July 2009

Enormous attention has been attracted to the safety issues regarding numerous pipelines that have had to be repaired by welding. The present paper describes experimental and numerical research conducted to assess the structural condition of welding-repaired pipeline, subjected to internal pressure including cyclic load. Six full-scale pipe specimens are tested under pressure to determine their structural capacity. Their stress distributions are measured, and their stress concentrations and yield and burst limit load are analyzed. The results of the present study demonstrate that on the pipelines with a single drilled hole the burst occurred far from the welding sites, whereas on the pipelines with several holes drilled in short span the burst took place between the two adjacent tube caps, suggesting that multi-cap repair is disadvantageous to the loading capability of the pipelines. It is also found that the burst pressure may not be affected by welding either tube-cap or patch and cyclic loading, but the yield limit loads of the repaired pipelines decreased respect to undamaged pipeline, among which the lowest one decreased up to 85% of that of the undamaged pipeline. In addition, using nonlinear finite element tools, stresses state in welding repaired pipeline is calculated. It is showed that bulging occurs in long and narrow area along longitudinal direction, addressing where burst rupture occur.
Increasing the Network Capacity: Is It Always the Best Choice?
Authors: Andre´ Jean , Pillay Tony
Published: July 2009

A network is considered to be saturated when all operational constraints cannot be fulfilled. For a gas network, it can be observed when the operator cannot pipe the entire throughput or when it cannot deliver the flows at delivery points with high enough pressures. When a transportation or distribution network is overloaded, the common answer to improve flow and pressure conditions is to add new links or to increase the capacities of one or several existing links. On gas networks, this leads either to lay out new pipelines or to loop existing pipelines when we are close to the saturation. In this paper, we will first exhibit some examples of gas networks on which increasing the capacity can yield to a worse situation than before. We can also address the paradox as follows: on these specific cases, we can remove some existing pipelines to better operate these networks. This work can be related to the class of well-known paradoxes as the Braess’s paradox on road traffic networks. Then, we will explain how this paradox can happen on very simple networks to highly meshed networks. Hence, on these networks, the increase in diameter of one pipe can imply both a decrease in total power loss and a violation of the minimal pressures required at end-points. Finally, we will give some clues to detect these paradoxes on general networks.
An Automatic Flaw Identification Method for Defect Inspection of Pipeline Girth Weld
Authors: Li Jian , Zhan Xianglin , Chen Shili , Zhuge Jingchang , Jin Shijiu , Wang Likun , Chen Pengchao
Published: July 2009

Various types of defect may be formed in girth welds of long-distance pipeline in the process of welding. They are hidden dangers to pipeline transportation safety. Currently, ultrasonic phased array instrument is commonly adopted for quick automatic positioning and quantitative analysis of flaws in the girth weld after welding. But as for qualitative analysis – flaw classification, traditional manual identification method is still used. By traditional method, human-made error is easily introduced and classification result is depended on the detection experiences of the inspecting person. To overcome these deficiencies, a new method combined second generation wavelet transform (SGWT) with Radial Basis Function neural network (RBFN) is proposed in this paper, realizing automatic flaw classification and reducing human factors impaction. SGWT is ideally matched local characteristics of the flaw signal, improving both the computational speed and flaw classification efficiency. Then, based on the “energy-status” feature extraction method and the above SGWT analysis, feature eigenvectors of the flaw signals are extracted, training the following RBFN. And then when the feature of any flaw is extracted, it can be recognized by the network. The output of the network is the type of the input flaw signal, realizing automatic flaw classification. Finally, an ultrasonic phased array inspection system is described. The system is integrated with automatic flaw detection and classification. Experiments are tested on a long-distance pipeline girth weld block with artificial defects in it. The results validate that the proposed method is efficient, which is helpful to increasing inspection speed and reliability of flaw inspection for long-distance pipeline girth welds.
Near Neutral pH SCC of Grade X80 Linepipe Steels Under Cyclic Loading
Authors: Ishikawa Nobuyuki , Kimura Mitsuo , Asahi Hitoshi , Sawamura Mitsuru , Omura Tomohiko , Kishikawa Hirofumi
Published: July 2009

Susceptibility to stress corrosion cracking (SCC) of Grade X80 linepipe steels, which were produced by recent TMCP (Thermo-Mechanical Controlled Processing) technique, controlled rolling (CR) followed by accelerated cooling process (ACC), in near neutral pH conditions was investigated, and cracking behavior was compared with conventional Grade X65 linepipe. Longitudinal strip specimens with small surface notches were cyclically loaded in the NS4 solution with cathodic polarization of −1000mV vs. SCE. No significant difference in susceptibility to SCC was found between Grades X80 and X65 linepipes, both produced by TMCP process, even under higher stress condition for X80 linepipe steel. Hydrogen permeation test reviled the strong effect of hydrogen for the cracking under the SCC test condition. Transgranular cracking and quasi-cleavage fracture were observed as an evidence of the effect of both corrosion and hydrogen embrittlement on near neutral pH SCC.
Modelling of Flexible Victaulic Couplings Using Basic Finite Element Software
Authors: Motriuk Roman W.
Published: July 2009

In the past decade, Victaulic couplings have gained significant recognition as important piping elements, which are used mainly in water and slurry transportation systems. For example, grooved flexible Victaulic couplings offered significant economical and reliable piping connections when compared to other connecting elements such as flanges. Victaulic couplings are on average three times faster to install than welding piping connections. They are more reliable and cost-effective than flanges or threaded connectors. In addition, the speed and easiness of their assembly or disassembly as well as their flexibility and ability to provide thermal gaps make the couplings desirable as piping elements. Furthermore, the couplings provide stress designers with a rare opportunity to cheaply and reliably compensate for piping loads which are otherwise exerted on equipment attached to piping. For the above reasons Victaulic couplings are frequently used in current piping designs. In spite of their simple design and application they pose a significant challenge for stress designers. The stress software packages based on piping finite element theories which are commonly used in industry do not provide the means to model Victaulic couplings adequately. These packages are based on stress linear theories, and Victaulic couplings with their gaps are definitely non-linear elements. Therefore, the approach to model these elements is very approximate and is usually done by the use of nonlinear restraints built into the software. The stiffness and friction for Victaulic coupling “restraints” are rarely known and assumptions of their values have to be made in order to carry out calculations. Therefore, the prescribed values for the restraints directly influence the stress results. This work discusses assumptions based on several simple stress models. An attempt is made by the author to minimize conservatism as much as practical in the modelling of Victaulic couplings, while waiting for the manufacturers of these elements to test their products and provide meaningful statistical information, which could then be used to carry out stress predictions. The couplings’ stiffness, bending moment and axial force capabilities provided in this work must not be used for design purposes unless verified and accepted by the couplings’ manufacturers.
3rd Party Review of Geometry Pig Inertial Survey Data at the Colville River HDD
Authors: Hart James D. , Zulfiqar Nasir , Erickson Tobias H.
Published: July 2009

This paper describes a 3rd party review of geometry pig inertial surveys of the ConocoPhillips Alaska, Inc.-operated Alpine 14-inch diameter oil and 12-inch diameter water pipelines at the horizontal directionally drilled (HDD) Colville River crossing. The geometry of these pipelines is periodically surveyed to monitor for potential thaw-induced differential settlement between thaw-stable and thaw-susceptible soils along the HDD profile under the river. Preliminary reviews of the elevation profiles from multiple surveys showed significant run-to-run variations within the HDD. However, considering the long distances between the reference elevation tie points, the observed elevation differences appeared to be within the position accuracy of the inertial survey specifications. As a follow up to the initial review, a more detailed 3rd party review of the data was performed. This paper describes how the elevation, pitch and bending strain data from four different inertial surveys performed for each pipeline over a five year period was processed to look for monotonic trends and/or locations of significant pipe deformation. It was determined that the bending strains for both pipelines were small compared to the allowable strains and that the most critical locations for both pipelines occurred in the vicinity of the end of the below grade casing and the adjacent aboveground pipe support. At each end of the HDD, the pig data signatures indicate the presence of a sagbend curvature lobe at/near the end of the casing and an overbend curvature lobe at/near the adjacent pipe support which is clearly indicative of relative movement between the below grade section of the pipe and the pipe support. The response at the pipe support was confirmed by visual inspection of the pipe where minor buckling damage to the external sheet metal insulation jacket at the ends of the saddle was observed. The results from this review were used to develop a recommended forward-looking geometry monitoring schedule.
Failure Analysis of Impact Damaged Pressure Vessels and Pipelines
Authors: Telichev Igor
Published: July 2009

The present paper is devoted to analysis of burst conditions of the pipeline-in-service and vessel under high pressure subjected to the debris impact due to accidental explosion. The central concern of this study is to determine the border between simple perforation and catastrophic fracture of impact damaged pressurized structure. Under certain conditions vessel perforation from the front side can lead to unstable, rapid crack growth (“unzipping”). The pressure vessel of the relatively small size can be damaged from the rear side as well. As a consequence, two main classes of catastrophic failure of such structures are likely to occur: structure fracture from the front side and failure from the rear side. Damage patterns and mechanisms leading to unstable crack growth are discussed. The impact holes in a wall of pressurized structure are considered as a crack-like defect. By the model suggested, the cracked area around the penetrated hole is simulated by two radial cracks emanating from the rim of a hole. So the diameter of the model hole is equal to the diameter of the front impact hole; the length of the crack is bounded by a damage zone, which is a zone of spall cracks adjacent to the perforated hole. In a gas-filled cylinder shell the stresses in the circumferential direction are twice the longitudinal stresses. Thus, in the process of fracturing the cracks tend to run longitudinally, perpendicular to the hoop stress. By this reason the hypothetical radial cracks are normal to the hoop stress. Nonlinear fracture mechanics techniques were used to analyze and predict whether a wall perforation will lead to mere leakage of gas, or whether an unstable crack will run and destroy the pressurized structure. The problem was solved by numerical method of singular integral equations in Chebyshev’s polynomials. A developed model was successfully applied to the simulation of experimental results.
Liquid Pipeline Capacity Optimization Through Pressure Control
Authors: Shirt Roger W. , Otero Fernando
Published: July 2009

In 2006/2007 Enbridge Pipelines undertook a pressure control optimization program as part of an overall effort to maximize throughput on a 34″ batched heavy crude pipeline. Higher throughputs required simultaneous operation of both pump units at intermediate stations. This mode of operation had not been previously achieved on a reliable basis due to the occurrence of line instabilities. Pressure control optimization procedures developed by Enbridge and control industry partners over the past 5 years were employed. Program scope included review and optimization of pressure control systems at 24 pump stations and 3 delivery sites. A preliminary review of pressure control valves established their suitability for anticipated service conditions. No other significant equipment purchases were required to execute the project. Program results are: • Intermediate stations are now reliably operated with both pump units simultaneously engaged; • A minimum 3.5% increase in pipeline sustained capacity is attributed by Enbridge to the pressure control optimization efforts; • PCV pressure drop reductions were achieved at most mainline pump stations resulting in greater than $500,000 (US) per year in pumping energy savings; • A 32% reduction in delivered batch size over/short volumes was achieved at one delivery site; • Operators report a significant increase pipeline reliability, with historical data demonstrating a 50% reduction in one indicator of operator burden; • Program costs were recovered in less than one year of operation. Similar pressure control optimization efforts are currently being undertaken on other pipelines within Enbridge’s network.
Development of an Index-Based Risk Model for All Liquid Hydrocarbon Facilities
Authors: Harron Lorna
Published: July 2009

Enbridge Pipelines Inc. manages over 1200 liquid hydrocarbon facilities across Canada and the United States, including both mainline facilities and gathering system facilities. The range of facilities managed by Enbridge includes terminals, pump stations, valve sites, scraper trap sites, battery sites, and densitometer sites. Evaluation of risk at facilities is a requirement of 49CFR195 (2) for liquid mainline facilities located in the United States and a requirement of CSA Z662 (3) for NEB regulated mainline facilities in Canada. Enbridge has developed an index risk model that is modular in nature to evaluate risk at various liquid facilities. The index risk model provides a relative risk ranking of facility risk, so the risk values obtained are comparative numbers. Facility risk values may be compared with all facilities within the System, or between similar types of facilities, such as terminals. The modular nature of the facility risk model permits the evaluation of all applicable assets within a given facility. There are three likelihood modules and eight consequence modules within the facility risk model that combine to create a risk value using Equation 1: Risk=Likelihood×Consequence(1) The modular indexed risk model has proven to be an effective means of evaluating facility risk. The modular approach meets the requirements of 49CFR195 and the Onshore Pipeline Regulations (OPR 1999) that references CSA Z662 for the risk assessment of facilities associated with mainline pipe. The modular approach can be applied to all facilities regardless of regulatory requirements and can assist in the prioritization of risk control strategies at facilities. As this approach provides a whole risk view of facilities rather than focusing solely on leaks and spills, the risk model may identify systemic areas of opportunity within the organization. This paper provides a review of the development of a modular index facility risk model for liquid operations. Challenges and successes faced during the development and execution of the model are discussed.
Application of Extreme Value Statistics to the Prediction of Maximum Pit Depth in Non-Piggable, Buried Pipelines
Authors: Alfonso L. , Caleyo F. , Hallen J. M. , Espina-Hernandez J. H. , Escamilla-Davish J. J.
Published: July 2009

Currently, the reliability of non-piggable pipelines is mainly assessed either from historical failure data or from the results of direct assessment evaluations. When external, localized corrosion is the main threat to the pipeline integrity, the most important factor in assessing the reliability of a pipeline segment is the distribution of maximum pit depths. This distribution cannot be directly derived from historical failure data, nor from the information obtained from external corrosion direct assessment. In contrast, the statistical modeling of extreme values could be used to predict the distribution of pit depth maxima in a pipeline from a relatively small number of maximum pit depths measured at excavation sites along its length. Despite of the large number of works aimed at the application of the extreme value statistics, there is a lack of studies devoted to the applicability of the method for prediction of the maximum pit depth for the pit densities and pit spatial patterns typical of long buried pipelines. In this work, Monte Carlo simulations were conducted in order to assess the statistical errors associated with the prediction of the maximum pit depth for a wide range of the number and size of the inspection areas, pits per unit area and pit spatial patterns. As a result, the optimum area of inspection is proposed. The Monte Carlo numerical experiments were run by using synthetic and real corrosion data acquired by magnetic flux leakage and ultrasonic in-line inspection (ILI) tools, an approach that has not been reported in previous studies. The ILI data was sampled using standard methods of extreme value analysis, and the predicted maximum pit depth was compared with that reported by the in-line inspection. Monte Carlo simulations with synthetic and real corrosion data have allowed assessing the influence of the number and size of the inspected areas on the accuracy of predictions when pits distribute homogeneously and non-homogeneously in the pipeline. It is shown that, when the distribution of pits is homogeneous, the accuracy in the maximum pit depth prediction using the proposed method is similar to the measurement errors associated with magnetic flux leakage ILI tools.
CTOA Measurements of Welds in X100 Pipeline Steel
Authors: Drexler Elizabeth , Darcis Philippe , McCowan Christopher , Treinen J. Matthew , Shtechman Avigdor , Reuven Rony , Siewert Thomas , Smith Robert , Merritt James , McColskey J. David
Published: July 2009

A suite of tests characterizing X100 pipeline steels was initiated at the National Institute of Standards and Technology (NIST) in Boulder. Part of the test matrix included testing the toughness of the base metal, welds, and heat-affected zones (HAZ) by use of modified double cantilever beam specimens for crack tip opening angle (CTOA) testing. The thickness of the test section was either 3 mm or 8 mm. Girth welds perpendicular to the growing crack, and seam welds and their HAZ parallel with the crack, were tested with a crosshead displacement rate of 0.02 mm/s (with the exception of one girth weld specimen for each thickness, which were tested at 0.002 mm/s). Analysis of the data revealed some general differences among the weld specimens. The tests where the crack ran perpendicular to the girth weld demonstrated changes in CTOA and crack growth rate as the crack moved through the base metal, HAZ, and weld material. We observed the values for CTOA increasing and the crack propagation slowing as the crack moved through the weld and approached the fusion line. The stress field appeared to be strongly influenced by the thin HAZ, the fusion line, and the tougher base material. Consequently, the CTOA of the HAZ associated with the girth weld was larger than that of the seam-weld HAZ. It was not possible to obtain CTOA data for the seam weld, with the crack parallel within the weld, because the crack immediately diverted out of the stronger weld material into the weaker HAZ. CTOA values from both girth welds and seam-weld HAZ were smaller than those of the base material. The 8 mm thick specimens consistently produced larger CTOA values than their 3 mm counterparts, introducing the possibility that there may be limitations to CTOA as a material property. Further tests are needed to determine whether a threshold thickness exists below which the constraints and stress field are sufficiently changed to affect the CTOA value.
Developments in Reliability-Based Corrosion Management and the Significance of In-Line Inspection Uncertainties
Authors: Stephens Mark , van Roodselaar Albert
Published: July 2009

The pipeline industry is moving to embrace more quantitative analysis methods for assessing pipeline integrity and demonstrating the benefits of integrity maintenance programs. Analysis based on structural reliability concepts is ideally suited to this purpose. In the context of corrosion management, the essence of this approach is to combine appropriate failure prediction models, in-line inspection data, the physical and operational characteristics of the pipeline, and corrosion growth rate projections, within a probabilistic analysis framework, to estimate the likelihood of corrosion failure as a function of time. A key element in this analysis approach is explicit consideration of all significant forms of uncertainty, including the uncertainties inherent in the data obtained from in-line inspection. This paper provides an overview of an ongoing research project, sponsored by the Pipeline Research Council International (PRCI), which is developing a reliability-based process that will form the basis for an industry-accepted approach to assessing and managing pipeline integrity with respect to corrosion. It also discusses the sources of uncertainty inherent in the in-line inspection process and their significance in the context of corrosion reliability analysis.
Evaluation of Close-In Blasting Effects on Welded Steel Pipelines
Authors: Nyman Douglas J. , Dowding Charles H. , Oriard Lewis L.
Published: July 2009

Occasionally, it is necessary to perform blasting close to buried, welded steel pipelines to excavate foundations or roadway cuts, conduct mining operations, or to construct an adjacent pipeline trench. The primary hazards associated with blasting near pipelines include permanent rock mass displacement owing to delayed gas pressures and ground strains from wave propagation (compressive, shear and surface waves). Current pipeline standards do not address these limitations for blasting in proximity to buried pipelines. Existing methodology is often applied quite conservatively in the form of permissible ground particle velocity thereby limiting ground strain, which leads to increased costs for the party conducting the blasting and/or the pipeline owner who must provide pipeline protection. This paper presents methodology and guidelines for the evaluation and protection of buried pipelines subjected to the effects of blasting. The examples given in the paper represent a departure from the normal practice of specifying blasting restrictions on buried pipelines, because they are based on higher peak particle velocity limits than suggested by other researchers and currently adopted by a number of pipeline companies. General recommendations are provided for evaluating the strains induced into buried pipelines and avoiding the effects of mass movement of rock due to delayed gas pressure. The general goal for this paper is to produce methodology and guidelines that are equally applicable and realistic for both the pipeline owner and the party conducting the blasting; however, they should not be considered to be recommendations for any specific future project.
Feasibility Study Relating Guided Wave Ultrasonic Technology (GWUT) and Pressure Testing for High Pressure Steel Pipelines
Authors: Leewis K. , Ersoy D. , Matocha G.
Published: July 2009

This paper will demonstrate that Guided Wave Ultrasonic Testing (GWUT) could eventually be considered an acceptable tool for detecting indications of missing cross sectional volume that would rupture if a pressure (hydrostatic) integrity assessment test was conducted to API 1110 (or ASME B31.8 or 49CFR192 Subpart J). In addition the paper will offer one example of an industry inspection mitigation and response methodology for GWUT.
Investigations on the Local Buckling Response of High Strength Linepipe
Authors: Fatemi Ali , Kenny Shawn , Sen Millan , Zhou Joe , Taheri Farid , Paulin Michael
Published: July 2009

A numerical modeling procedure was developed, using the finite-element simulator ABAQUS/Standard, to predict the local buckling and post-buckling response of high strength pipelines subject to combined state of loading. The numerical procedures were calibrated using test data from large-scale experiments examining the local buckling of high strength linepipe. The numerical model’s response was consistent with the measured experimental response for predicting the local buckling behavior well into the post-yield range. A parametric study was conducted that examined element selection, mesh topology, second-order effects, geometric imperfections and material properties. The results from this study are presented.