bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptability of X80 Steel and its SAW Welding Wire to the Welding Procedure
Authors: Huang Zhijun , Deng Renhua , Kai Miao , Liu Jibin , Kong Junhua , Wang Yutao
Published: October 2008

Taking into account cost and safety for pipelines transporting oil and natural gas, the strength of the steel used is getting higher and the plate wall thicker. After a good use of X70 steel in China’s East-to-West Gas Transmission Project, X80 steel is drawing more and more attention in the future pipelines, resulting in its successful production in Wuhan Iron and Steel (Group) Company, and also bringing some concerns about welding. With increasing the wall thickness of the pipeline, the welding heat input is expected to increase for an increased deposited rate and a quality weld configuration. However, it is likely for the thermo-mechanically controlled rolled fine-grained steel that the properties of the heat affected zone will get deteriorated after it is subjected to large weld heat inputs, so the influence of the weld linear energy on the weld configuration and the properties of the welded joint have been studied. It is evident that an increased weld heat input can significantly reduce the number of the welding runs, thereby increasing the production proficiency and favoring the welding quality control as well. Furthermore, for Ti, Nb micro alloyed X80 steel, almost no property deterioration was found in this experiment, indicating that X80 steel is adaptable to various welding heat inputs, which gives much possibility of selecting a desirable large heat input. X80 steel is characteristic of low carbon and low sulphur contents with the addition of Mn, Mo alloying elements, and correspondingly, its weld metal should have the similar features that need to be obtained with the welding materials. However, the welding wires for X80 steel aren’t currently and commercially available in domestic market, so developing new welding wires is an urgent task for the mass application of X80 steel. Two submerged arc welding wires, one used for X70 steel and the other one branded as WGX2 with a higher strength were used in this welding experiment on X80 steel. The former produced excellent average impact energy up to 172J at −20°C close to that of the base metal but practically under-matched strengths and unqualified bend properties. The welded joint produced with WGX2 wire practically has a little over-matched strengths, qualified bend properties and satisfactory impact energy as well.
Prediction of Transient Behaviors of Gas-Condensate Two-Phase Flow in Pipelines With Low Liquid Loading
Authors: Deng Daoming , Gong Jing
Published: October 2008

Transporting natural gas and gas condensate in a long distance pipeline occurs frequently during the development of offshore or desert gas condensate and/or oil fields. However, the thermohydraulic calculation of gas-condensate pipeline, especially transient flow simulation, is hitherto a challenging issue in the pipeline industry on account of a maze of complexities of pipeline undulation, changeable properties of fluid, and transfer of momentum, mass and heat. This study is intended to predict the transient flow behavior in gas-condensate pipelines. In the paper, a hydraulic and thermodynamic (such as phase behavior and properties) model for the analysis of transient gas-condensate two-phase flow in pipelines with low liquid loading is outlined. The hydraulic model is based on simplified “No Pressure Wave” model where the constitutive relation results from the Ottens et al (2001) correlation. An implicit method, the convergence and stability of which have been verified by example calculations, is utilized to solve the transient flow model equations of gas-condensate pipelines. In the end, the transient performances of low-liquid-loading gas-condensate two-phase non-isothermal flow in undulating pipelines, which are subjected to boundary conditions of increasing or decreasing inlet flow rate and specified outlet pressure with time, are numerically investigated. The results, such as pressure and liquid holdup profiles vs. time, and time evolutions of outlet condensate flow rate and accumulated liquid content etc., show that the presented model and numerical method for analyzing gas-condensate transient flow behaviors in pipelines looks reasonable.
Facility Integrity: A Management Perspective
Authors: McNeill Dave B. , Morrison Tom
Published: October 2008

According to the API-PPTS Advisory 2005-3 “Overview of Incidents Occurring on Facilities Piping and Equipment,” over half of all reported releases occur within pipeline facilities. Facility integrity is a complex issue due to the large number of potential leak sources and the relatively small size and impact of releases. Operators struggle to determine whether additional resources should be allocated to this issue and, if so, how to make a meaningful impact. In this paper we will address the questions of why the pipeline industry should address facility releases, why Operators struggle with facility integrity, and what is required to overcome barriers. We will present information to assist Operators to understand the cause of facility leaks, methods to assess the impact of releases, methods to prioritize resources, and how to develop metrics to measure success.
Numerical Simulation of Hydrogen Transport at a Crack Tip in a Pipeline Steel
Authors: Dadfarnia Mohsen , Sofronis Petros , Robertson Ian , Somerday Brian P. , Muralidharan Govindarajan , Stalheim Douglas
Published: October 2008

The technology of large scale hydrogen transmission from central production facilities to refueling stations and stationary power sites is at present undeveloped. Among the problems which confront the implementation of this technology is the deleterious effect of hydrogen on structural material properties, in particular at gas pressure of 1000 psi which is the desirable transmission pressure suggested by economic studies for efficient transport. In this paper, a hydrogen transport methodology for the calculation of hydrogen accumulation ahead of a crack tip in a pipeline steel is outlined. The approach accounts for stress-driven transient diffusion of hydrogen and trapping at microstructural defects whose density may evolve dynamically with deformation. The results are used to discuss a lifetime prediction methodology for failure of materials used for pipelines and welds exposed to high-pressure hydrogen. Development of such predictive capability and strategies is of paramount importance to the rapid assessment of using the natural-gas pipeline distribution system for hydrogen transport and of the susceptibility of new alloys tailored for use in the new hydrogen economy.
Geohazard Risk Management for the Nor Andino Gas Pipeline
Authors: Porter Michael , Reale Rodolfo , Marcuz Gabriel , Savigny K. Wayne
Published: October 2008

A 1,050 km long 20” pipeline was constructed to transport natural gas from northern Argentina to the coast of Chile. On the Argentine side, significant portions of the route traverse rugged mountainous terrain subject to landslides, debris flows, flash floods, and earthquakes. On the Chilean side (situated up to 5,000 m above sea level), the pipeline crosses active faults and terminates at locations historically subject to tsunami. The pipeline began operation in 1999. An outburst flood in a steep mountain stream caused the pipeline to rupture in 2001. Reactivation of a large rock slide in 2002 caused a second rupture. It appeared that the original design had underestimated the route’s exposure to geohazards, and efforts were required to improve pipeline safety and reliability. A geohazard risk management program was initiated in April 2002. Geohazards were identified and characterized through airphoto interpretation and field inspection. Sites were initially ranked using semi-quantitative risk estimates. Risk cost-benefit analyses were used to select optimal risk control measures at high ranking geohazard sites. These included monitoring programs, reconstruction of stream crossings, reroutes, and in one instance, landslide avoidance using a horizontal directional drill. Risk control measures were implemented between 2002 and 2006, and additional efforts are ongoing. An updated assessment of geohazard exposure was completed in 2005 with the objective of quantifying the level of risk reduction that had been achieved and prioritizing further risk reduction efforts. This paper describes implementation of the geohazard risk management program using a case history format. It highlights the techniques used to control the range of hazard that were identified in 2002 and to quantify the improvements achieved by 2006. The paper concludes with an overview of additional risk reduction initiatives that are in progress or under consideration.
Pipeline Leak Localization Using Pattern Recognition and a Bayes Detector
Authors: Di Blasi Marti´n , Baptista Renan Martins , Muravchik Carlos
Published: October 2008

A novel leak localization method for multi section pipelines is presented. Based on normal operation flowing thermodynamic pressure drop patterns along the pipeline, the system continuously compares with the measured pressure drops, and makes a decision based on the best fit finding the section where the leak occurs. A statistical approach is used accounting for noisy measured signals. The method uses steady state fluid equations, a recursive parameter estimation algorithm, and statistical decision and pattern recognition techniques. A modification is introduced to consider the cost of making a wrong leaky section choice in terms of the excess volume spilled due to gravitational flow after pipeline shut down. This leads to a Bayesian decision scheme minimizing a risk functional. The costs are the spill volumes, obtained from dynamical simulation of the pipeline, under the various possible decision scenarios. Finally, details are given of the successful implementation of the system on a 500km long oil pipeline, and real data from a simulated leak experiment are shown.
Design of Contingency Plans for Pipeline Leakage Using Hydraulic Simulation
Authors: Di Blasi Marti´n , Felici Gustavo , Ramponi Walter , Czarnowski Juan
Published: October 2008

The use of leak detection and location systems has became a common practice in the control rooms of pipeline operations, whereby operators are automatically alerted of a leak, and informed of its approximate location. Considerable attention has primarily been paid to leak sensitivity and leak detection time. However, this paper shows that in long pipelines the volume lost after a pipeline shutdown can be substantially more than what was lost prior to the detection. In very irregular altimetry, the drainage from the pipeline segment can represent a greater volume of spillage as compared to the spillage from the start of the leak until its detection. These volumes can be reduced by taking the appropriate actions. This work will illustrate the importance of having a leak contingency plan that orients the operators to take suitable actions that will diminish the volume spilled. A leak contingency plan is a detailed plan of recommended actions, for example valve closure and pumping shutdown, and the specific time sequence in which they have to be executed. The design of these plans was based on the use of hydraulic transient simulations of an actual 3000-km network in Argentina.
Full Scale Experimental Analysis of Stress State in Welding Repairs of Drilled Pipelines
Authors: Shuai Jian , Bu Wenping
Published: October 2008

Recently, drilling holes in petroleum transmission pipelines is becoming of major concern for pipeline companies. These drilled pipelines must be repaired through welding ways. There are two ways to repair these pipelines in fields. One is welding a short tube with a cap. Another is welding a patch. In this paper, full scale experiments were conducted to assess the stresses state and the loading capability of the repaired pipelines. The φ711×10 pipelines repaired by welding a tube cap or a patch were pressured to burst failure. Strain gages have been used extensively to monitor stress state in full scale pipeline tests. It was showed that welding a tube cap or a patch resulted in the non-uniform stresses distribution and the stress concentration in the extent. These two kinds of the repaired pipeline has almost the similar yield limit pressure which are approximately equal to 85% of that of pipelines that were not damaged. Patching repair has more restriction to the deformation around a hole than tube capping repair, therefore it may have a little better loading capacity than tube capping repair. The burst pressures in these tests are close to that of pipeline which has not been damaged, whereas the location of burst failure is far from where a short tube or a patch is welded. The burst is a ductile fracture by maximum shear stress.
Critical Hardness for HSC in Deposit Welding on Steel Line Pipes Under Cathodic Protection
Authors: Oguchi Noritake , Sakai Junichi , Inoue Hiroyuki , Komukai Shigeru
Published: October 2008

Repairing corrosion-damaged areas of operational steel line pipes by deposit welding performed without stopping the gas flowing inside is a common practice. However, this repair method tends to considerably increase the hardness of the weld metal and the HAZ, and it poses the risk of HSC under cathodic protection. In this study, the HSC susceptibility of the welding area was examined using welded full-scale C-ring specimens. The specimens were prepared from X42, X60, and X65 steel line pipes, whose outer diameter and longitudinal length were 610mm and 100 to 110mm, respectively, and whose nominal thickness was 10.3 to 15.1mm Deposit welding was applied to the middle of each specimen’s outer surface, and then a bolt through the specimen was tightened until the welded part was subjected to yield stress. The welded surface of the welding and its surrounding area were exposed to a test solution whose pH was adjusted to 7, and a cathodic current of 20mA/cm2 or 4mA/cm2 was applied for 500hours. Cracks appeared in the weld metals on the C-ring specimens to which a cathodic current of 20mA/cm2 had been applied. However, the propagation of the cracks ceased at the boundaries between the weld metal and the HAZ, and no cracks initiated in the HAZ. The maximum hardness of the HAZ was about 300 to 400Hv. These levels of hardness are far greater than 260Hv, which is the value obtained from experiments carried out using slow strain rate testing and is widely used in Japan as a criterion of hardness for avoiding HSC in the HAZ.
Determination of Safe Pumping Temperature for Waxy Crude Pipelines
Authors: Zhang Jinjun , Ding Jianlin , Xu Kang , Fan Huajun
Published: October 2008

Flow risk of a hot waxy crude pipeline mainly comes from restart failure, i.e. oil gelation resulted from prolonged pipeline shutdown, and unstable operation at low flow rate. Once the unstable operation happens, the friction loss of the pipeline increases with decreasing flow rate and finally flow may cease if treated improperly. To avoid these flow risks, the pumping temperature of the crude is generally required to be kept above a minimum allowable temperature, and conventionally the pour point temperature is taken. This practice is effective but quite rough. Obviously, to control the inlet temperature of a heating station at the pour point temperature implies different safety margin for winter and summer operation. For large throughput hot oil pipelines, reduction of the heating temperature even by a little bit may save a great amount of fuel. Therefore, how to save fuel while ensuring safe operation has been a valuable topic for long time. On the other hand, many factors impacting the flow safety are stochastic and with uncertainty, so analysis without considering this feature can hardly yield convincible results, though this has been the common case for many years. In this paper, by taking the stochastic feature into account, a Stable Operation Index (SOI) and a Pipeline Restartability Index (PRI) were proposed to assess the flow safety of a pipeline concerning the low-flowrate stable operation and restartability after shutdown. Combining these two indexes, a Pipeline Flow Safety Index (PFSI) was adopted to assess the flow risks of hot waxy crude pipelines. On this basis a new approach to quantitatively determining the safe pumping temperature was developed and illustrated by a case study. Encouraging results show that this new approach has the potential to replace the simple rule of pour point as a guide to determining the safe pumping temperature of waxy crude pipelines.
Toughness Evaluation on Seam Weld HAZ of High Strength UOE Linepipe
Authors: Ishikawa Nobuyuki , Shinmiya Toyohisa , Igi Satoshi , Kondo Joe
Published: October 2008

Heat affected zone (HAZ) along with the weld seam of LSAW has discrete microstructure and usually shows lower toughness than base material. Grain coarsening and formation of M-A constituents governs the HAZ toughness, and a lot of efforts have been made to improve HAZ toughness. However, it is impossible to completely reduce the effect of microstructural change by seam welding. Especially, higher strength or heavy wall linepipes which have richer chemistry tend to have lower HAZ toughness. Therefore, it is important to understand the relationship between microstructural characteristics and toughness of HAZ and fracture behavior of HAZ region in order to ensure the structural reliability of seam welded region. In this paper, fracture behavior of X70 grade heavy wall UOE linepipe was investigated. Wide plate tensile test was conducted with the surface notch introduced on to the coarse grain HAZ, as well as the small scale testing such as Charpy and CTOD test. Fracture mechanics analysis was also carried out to understand the critical condition for brittle fracture of HAZ, and compared with the experimental results.
Effects of Microstructure and Texture on DWTT Properties for High Strength Line Pipe Steels
Authors: Hara Takuya , Shinohara Yasuhiro , Asahi Hitoshi , Terada Yoshio
Published: October 2008

The crack arrestability for high strength line pipe steels with tensile strength of 650 to 850 MPa was evaluated using precrack DWTT (pc-DWTT). Moreover, the effects of microstructure and texture on pc-DWTT energy were investigated. The pc-DWTT energy was remarkably affected by tensile strength. The pc-DWTT energy of ferrite and bainite/martensite dual phase steels was much higher than that of bainite single phase steels in comparison with the same tensile strength. The {100} plane is a cleavage plane in iron, so the brittle crack mainly propagates along the {100} plane. Bainte single phase steels indicated a high intensity of the {100} on the plane rotated 40° from the rolling plane with the axis of the rolling direction. On the other hand, ferrite and bainite/martensite dual phase steels indicated not only a high intensity of the {100} plane rotated 40° from the rolling plane, but also a high intensity of the {100} plane parallel to the rolling plane. Slant fracture could be easily formed by the high intensity of the {100} on the plane rotated 40° from the rolling plane if local brittle areas such as martensite and austenite constituent (M-A constituent), which became the initiation point of brittle fracture, existed. In contrast, separation tended to be formed by the high intensity of the {100} plane parallel to the rolling plane that was caused by the formation of ferrite and bainte/martensite dual phase microstructure. Thus, pc-DWTT energy and shear area were remarkably affected by microstructure and texture. Therefore, to control microstructure and texture is vay important for the improvement of pc-DWTT properties.
Strengthening Low Carbon Steels for Oil and Gas Spiral Welded Pipes
Authors: Pyshmintsev I. Yu. , Pumpyanskyi D. A. , Kamenskih Yu. O. , Poznyakovsky I. N. , Permyakov I. L.
Published: October 2008

Strengthening mechanisms applied for modern line pipe steel design were studied. Low carbon steels alloyed with Mn, Mo, V, Nb processed by the way of controlled rolling were developed for spiral welded X65-X80 line pipes up to 1420 mm diameter. Formation of the microstructure during steel processing was studied. The effects of typical microstructure for the steels on mechanical properties, strain hardening behavior and Bauschinger effect were studied. Main metallurgical factors affecting on strength measured in plates and pipes were revealed using physical and computer simulations.
Hydraulic Characteristics of Pipelines Transporting Hot Waxy Crudes
Authors: Chen Jun , Zhang Jinjun , Li Hongying
Published: October 2008

Waxy crudes are generally pipelined by means of heating. In general, the friction loss of a pipeline decreases with decreasing flow rate. This is the case of isothermal pipeline. However, a hot oil pipeline operated at low flow rate might show a contrary case, i.e. friction-loss increases with decreasing flow rate. This is an unstable operation state and may result in disastrous consequence of flow ceasing if tackled improperly. For a waxy crude pipeline, this may also be exaggerated by the non-Newtonian flow characteristics at temperatures near the pour point. That is to say, there may exist a critical flow rate for pipelines transporting heated waxy crude, and in order to ensure safe operation, the flow rate of a pipeline transporting hot oil should be no less than this critical flow rate. Based on theoretical analysis and can study, the hydraulic characteristics of pipelines transporting hot waxy crudes was investigated, and an empirical model was developed correlating the critical flow rate QC and the pipelining parameters, such as the average overall heat transfer coefficient, the ground temperature, the heating temperature, etc. Another relationship was found between TZC, the outlet temperature of the pipeline corresponding to the critical flow rate, and the critical flow rate. This TZC is also the lowest pipeline outlet temperature that ensures the normal pipelining operation state. Case study on a 720mm O.D. pipeline transporting heated Daqing waxy crude with a pour point of 36 °C showed that the TZC was in a range of 31∼34.2°C.
Predicting Corrosion Rates for Onshore Oil and Gas Pipelines
Authors: Race J. M. , Dawson S. J. , Stanley L. , Kariyawasam S.
Published: October 2008

One of the requirements of a comprehensive pipeline Integrity Management Plan (IMP) is the establishment of safe and cost effective re-assessment intervals for the chosen assessment method, either Direct Assessment (DA), In-Line Inspection (ILI) or hydrotesting. For pipelines where the major threat is external or internal corrosion, the determination of an appropriate re-inspection interval requires the estimation of realistic corrosion growth rates. The Office of Pipeline Safety (OPS 2005) estimate that the ability to accurately estimate corrosion rates may save pipeline companies more than $100M/year through reduced maintenance and accident avoidance costs. Unlike internal corrosion, which occurs in a closed system, the rate of the external corrosion reaction is influenced by a number of factors including the water content of the soil, the soluble salts present, the pH of the corrosion environment and the degree of oxygenation. Therefore the prediction of external rates is complex and there is currently no method for estimating corrosion rates using either empirical or mechanistic equations. This paper describes a scoring model that has been developed to estimate external corrosion growth rates for pipelines where rates cannot be estimated using more conventional methods i.e., from repeat in-line inspection data. The model considers the effect of the different variables that contribute to external corrosion and ranks them according to their effect on corrosion growth rate to produce a corrosion rate score. The resulting score is then linked to a corrosion rate database to obtain an estimated corrosion rate. The methodology has been validated by linking the calculated corrosion rate scores to known corrosion rate distributions that have been measured by comparison of the results from multiple in-line inspection runs. The paper goes on to illustrate how the estimated corrosion rates can be used for the establishment of reassessment intervals for DA, ILI and hydrotesting, comparing the benefits of this approach with current industry recommended practice and guidance.
Study on Method of Recognizing Characteristics of Pipeline Leakage Acoustic Signals
Authors: Wang Likun , Tan Dongjie , Cai Yongjun , Fu SongGuang , Li Jian , Jin Shijiu
Published: October 2008

Wavelet package and neural network are used to recognize the characteristics of pipeline leakage acoustic signals. Acoustic signals produced by pressure variation of pipelines can be detected by the acoustic sensors installed on the pipelines. The detecting accuracy can be increased with recognizing the acoustic signals correctly. The method to detect acoustic signals by combining the wavelet package and neural network is introduced in this paper. The signal is decomposed with wavelet package firstly, then the decomposed coefficients in each frequency band are obtained through reconstruction. As a result, the parameters of the new sequences reconstructed on every decomposed node are acquired, and then these parameters are input to BP neural network to recognize the fault reason intelligently. At the end of the paper, field experiment data and their analyzed results are studied. The experimental results are provided to show that the proposed method can increase the accuracy efficiently.
Failure Behavior of Colonies of Corrosion Defects Composed of Symmetrically Arranged Defects
Authors: Benjamin Adilson C. , de Andrade Edmundo Q. , Jacob Breno P. , Pereira Leonardo C. , Machado Paulo R. S.
Published: October 2008

This paper presents a case study on the failure behavior of four colonies of corrosion defects using solid Finite Element models. These analyses accounted for large strains and displacements, stress-stiffening and material nonlinearity. Colonies 1 and 2 are each composed of two longitudinally aligned defects. Colonies 3 and 4 are each composed of four defects (two longitudinally aligned defects and two circumferentially aligned defects) arranged in a rhombus shape. For each of the four colonies a parametric study is performed in which the longitudinal spacing sL between the two defects longitudinally aligned is varied from a small value (sL)min to a large value (sL)max. Based on the results obtained the failure behavior of each colony is described and illustrated by contour plots of stresses. The failure pressures predicted by the Finite Element analyses are compared with those predicted by six assessments methods, namely: the ASME B31G method, the RSTRENG 085dL method, the DNV RP-F101 method for single defects (Part B), the RPA method, the RSTRENG Effective Area method and the DNV RP-F101 method for interacting defects (Part B).
Recent Development of High Strength Steels for Transmission Trunk Lines and Coiled Tubing
Authors: Liebeherr Martin , De Wispelaere Nico , Luneteau Frank , Ehlers Sabine , Issartel Christophe , Hivert Eric , Pensa Didier
Published: October 2008

Modern high strength steels need accurate control of microstructure in order to meet the steadily increasing requirements on mechanical properties, toughness or corrosion resistance. An appropriate steel making with inclusion control and a sophisticated thermo-mechanical controlled processing are the key factors, but we have to recognize that the process parameters have to be refined continuously to meet the targets. The present paper is going to demonstrate this progress using the examples of two recent development activities at Arcelor. At the same time it is shown that the development is often accompanied by the installation of new testing equipment for a more accurate and target-oriented material characterization. The first example deals with the development of an X70 for a 36” OD spiral welded pipe with 20.6mm wall thickness, a challenge for a hot strip mill when a good toughness is required at this thickness. We will briefly describe the sheet and pipe production and compare the mechanical properties on sheet and on pipe. The toughness performance of the new steel has been characterized in different orientations with respect to the rolling direction. In an attempt to quantify the crack growth propagation during the Batelle test, we equipped the existing testing device with a load cell so that we are now capable to document the energy absorption during crack propagation. The second example concerns the development of a coiled tubing grade 90 with HIC resistance for downhole application in corrosive environment. The challenging combination of high strength level, excellent low cycle fatigue (LCF) performance and corrosion resistance gave rise to the launch of a metallurgical study with the aim to develop a new steel grade. For a more complete material characterization we took advantage of this opportunity to install new CO2 corrosion test facilities (atmospheric pressure and high pressure). The LCF performance of the steel sheets has been characterized under constant strain amplitude conditions.
The Results of Reduction in Corrosion Rates Using Cleaning Pig
Authors: Fernandes Anibal Augusto , Dantas Francisco Ricardo , de Souza Lima Aline
Published: October 2008

This work is designed to present the results achieved by the implementation of a cleaning pig pass program in Petrobras pipelines at the Southeast region of Brazil. Inner pipeline corrosion generally can be found more intensively at the lower generatrix of liquid pipelines. It happens, due to the accumulation of water and residues at lower sectors of pipelines, in particular due to low flow rates or intermittent operation. The use of cleaning pig allows free water and residues to be removed from the pipeline. The effect of reduction corrosion rates may be verified both by the quantity of water and residues collected at the pig receivers and also by the corrosion rates measured using weight-loss coupons. The results achieved indicated a considerable reduction in corrosion rates with the use of cleaning pigging, especially in pipelines that transport oil or products containing water (free, emulsion or dissolved).
Development of a Combined Crack and Metal Loss Detection Tool
Authors: Atif Samia , Franz Josef , Bosch Ju¨rgen , Hugger Achim
Published: October 2008

Pipeline operators face many threats to the integrity of a pipeline. Over the years, sophisticated equipment and methodologies have been developed to counter these threats. However, until today, operators have been using individual inspection tools to detect and measure specific defects such as corrosion or cracks. This has caused operators around the world to invest significant efforts to perform multiple inspection runs and later correlate independent sets of inspection data.
A Semi-Quantitative Pipeline Risk Assessment Tool for Piggable and Un-Piggable Pipelines
Authors: Weigold Gunnar , Argent Colin , Healy John , Diggory Ian
Published: October 2008

ROSEN have developed together with MACAW Engineering Ltd. a Risk Assessment Tool that can be applied to both piggable and un-piggable pipelines. The Risk Model is structured to answer three basic questions relating to pipeline integrity: • What threats are active on the pipeline? • Will the active threats result in a leak or a rupture? • What is the company liability (cost) in the event of a failure? The risk assessment criteria on which the model is based are taken from codes and technical papers that have become accepted as industry norms. The Risk Model itself is semi-quantitative and is based on input data that operators should have for all pipelines. The results of the risk assessment provide an objective identification of active threats to pipeline integrity and a first level benchmarking of the operators procedures with regards to industry best practice. The paper will present the fast and robust Risk Assessment Approach and illustrate it’s application by different examples as it was used to identify and prioritize active threats mechanism to optimize maintenance expenditures for effective preservation of pipeline integrity.
Strategies for Managing Risk on Pipeline Projects
Authors: Wallace Peter , Cohen Mark , Lembach Guy , Murch Matthew , Sahney Reena
Published: October 2008

The risk factors pressuring pipeline projects are very similar to those that influence any capital construction project, except that the scale and complexity are magnified as are the consequences of even minor disruptions to the progress of the work. Essential to the successful planning, design, and construction of large capital projects is risk management. Project issues such as regulatory compliance, resource constraints, aggressive competition, and the access to and requirements of capital markets require aggressive and thorough risk management and control. Moreover, the ability to influence and mitigate cost and schedule risk decreases as the project progresses through the construction life cycle. This paper will discuss the major components of proper risk management including scoping, identification, analysis and evaluation, timely response, mitigation, control, and risk allocation using proven techniques. The significant risk areas in each phase of the project life cycle including, feasibility, planning and design, construction, and start up & turnover will also be discussed. This paper will also focus on tools and strategies in dealing with the common and costly areas of risk, particularly the use of CPM scheduling in the identification, control and quantification of risk management issues using statistical models, such as Monte Carlo simulations, and the use of CPM scheduling in the avoidance of claims will be highlighted.
Optimum Pipeline Inventory
Authors: No̸rstebo̸ Vibeke Stærkebye , Bakken Lars Erik , Dahl Hans Jo̸rgen
Published: October 2008

The gas transport system on the Norwegian continental shelf (NCS) consists of more than 6 600 km of pipelines and is the largest offshore gas transport system in the world. In 2004, dry gas exports from the NCS totalled 77.7 billion scm. The network is operated at very high pipeline pressure, up to 210 bar, and there are few booster stations along the way. Combined with the low ambient temperature, the high pressure provides the opportunity to store much gas in these long pipelines. A major challenge is to operate the pipelines at optimum inventory. This implies a delicate balance between high pressure and appurtenant high compressor energy consumption and environmental emissions versus lower pressure and the risk of loss in gas sales. A minimum quantity of gas is required in a pipeline for the initial pressurization of the system. The quantity is defined with an assumed pressure for each pipeline, and is known as linefill. Linepack is a quantity of gas in excess of linefill, which is necessary in order to make deliveries as requested and to provide operating tolerances, not least to cope with shutdowns upstream of the pipelines. A high linepack means higher pressure into the pipeline, but it also provides high flexibility and safety. In order to find the optimum inventory level, i.e. the total amount of gas in the pipeline, simulation in a pipeline simulation software and statistical analysis are used. For a given pipeline, the minimum inventory curve as a function of the steady state flow in the pipeline is found by the means of simulation. Historical flow rate values from the past two years are analyzed, and expected changes in the flow into and out of the pipeline are found by means of statistical analysis. On this basis, a recommended inventory curve is found for both the original and the increased capacity in the pipeline. The scope of the work is to increase energy efficiency and reduce environmental emissions by developing a recommended inventory level as a function of the flow in the pipeline. This paper reports on the analysis of one of the pipelines on the NCS. It describes the method used to analyze the flow/inventory level in the pipeline and the resulting recommended inventory curve. Furthermore the paper reports on experience from operation of the pipeline after implementation of the recommended curve.
Pipeline Operation in the North Sea Area: Statoil’s Experience and Challenges
Authors: Samdal Ove R. , Kvinnesland Anders , Apeland Kjell Edvard , Lind Arthur , Vartdal Kjartan
Published: October 2008

Statoil has since 1985 installed, commissioned and operated approximately 8000 km of pipelines in the North Sea area. Among these pipelines are several of the world’s largest offshore gas trunk lines with the onshore parts relatively short in length but often with complex landfalls, fjord and land crossings. Since 2002 Gassco has been the Operator for transporting Norwegian gas to continental Europe and the UK. Gassco is a fully state owned company. Statoil is now TSP (Technical Service Provider) for most of the trunk lines. Operating these pipelines represents several challenges, and the accumulated experience gained through successful operations of these pipelines has brought Statoil to the forefront within the pipeline industry. Through comprehensive research and development Statoil has improved pipeline technology within areas as inspection, maintenance and repair. Together with the development of risk based condition (integrity) assessment, inspection and monitoring planning tools and work processes, these technology achievements have significantly improved Statoil’s knowledge and understanding of the pipeline condition and associated risk levels. A significant reduction in operating cost has also been experienced. Together with its collaborating partners Statoil has among others improved internal inspection technology by improving the MFL technology to a level of extra high resolution (XHR-technology) making metal loss measurements more reliable and accurate. Multi diameter inspection tools (28”–42”) (MDPT) and optical laser tool (Optopig) have also been developed and put into operation. Sub sea pipeline survey by use of ROV has been significantly improved with regard to instrumentation and survey speed. A unique remote pipeline repair contingency system (PRS) with well defined response times (10–21 days), has also been developed. To get the full benefit of these developments a risk based pipeline condition (integrity) management system (PCMS/PIMS) has been developed with the development of DnV’s Orbit Pipeline as a key element. ORBIT Pipeline consists principally of data storage and administration and various risk based integrity assessment modules. This paper will discuss several topics related to these technology developments and development of risk based condition (integrity) assessment.
Holistic Approach to Acquisition and Statistical Analysis of ILI Results
Authors: Polouian Ludmila V. , Timashev Sviatoslav A.
Published: October 2008

In this paper a holistic approach to defect assessment is developed. The main emphasis is put on issues of defect detection and characterization — discrimination, interpretation and sizing by comprehensive evaluation of data acquired from In-line inspection (ILI) tools. The role of human factor in the use of ILI technology is discussed. General characteristic of ILI as a measurement system is given, and basics of the holistic analysis of ILI are presented. Results of analysis of real ILI data and of Monte-Carlo simulation are addressed, including a new approach to planning and analyzing results of verification digs, and an assessment of the true values of defect parameters.
Pipeline Integrity Management at Kuwait Oil Company
Authors: Porter Todd R. , Al-Nasser Emad
Published: October 2008

Kuwait Oil Company (KOC) operates large pipelines system in the State of Kuwait. This pipeline system is comprised of a complex network of high pressure gas, low pressure gas, fuel gas, condensate, crude subsystems as well as water pipelines. A Total Pipeline Integrity Management System (TPIMS) project was initiated in early 2005 to provide KOC with a complete system baseline, integrity management plan and system, and assessments. Periodic re-assessments will be conducted throughout the project life cycle to manage priorities and optimize integrity, repair and maintenance operations. The primary integrity threat of the pipeline system is Internal and External Corrosion, with secondary threats of mechanical damage and Stress Corrosion Cracking (SCC) to be considered as well. This case study will present the design, implementation and execution of a comprehensive approach to pipeline integrity management. Aspects of data management / analysis, integrity (ILI, DA) and risk analysis will be discussed. Kuwait has undergone significant reconstruction since the liberation from Iraqi invasion in 1991 and with mandates to increase production and throughput, system reliability and up-time is essential. KOC is well advanced in the implementation of a TPIMS, a model for the region and worldwide.
Geometric and Material Nonlinear Analyses of a Heated Zigzag Pipeline: Case Study to Look for High Stress Situations
Authors: Benjamin Adilson Carvalho , Silva Rita de Ca´ssia Carvalho , Guerreiro Joa˜o Nisan Correia , Loula Abimael Fernando Dourado
Published: October 2008

This paper describes the case study performed to look for high stress situations that may occur along the life span of a heated zigzag pipeline. The main results of several finite element (FE) analyses are presented. These analyses were performed using the general purpose FE program ABAQUS considering geometric and material nonlinearities. A rate-independent plasticity model using the von Mises yield criterion and isotropic hardening rule were adopted.
Constraint Based Fracture Assessment of Seam-Welded Pipes Containing Axial Flaws
Authors: Tkach Yuri , Horn Anthony , Bannister Adam , Bolton Edmund
Published: October 2008

An Engineering Critical Assessment (ECA) of a pipeline containing an axial defect is usually conservative if standard fracture test pieces are used for the fracture toughness testing. Conventional fracture toughness testing standards employ specimens containing deep cracks in order to guarantee conditions leading to high stress triaxiality and crack-tip constraint. In the current work, single edge notch bend (SENB) and single edge notch tension (SENT) test specimens of two different a/W (crack depth/specimen width) ratios (0.15 and 0.6) were used to obtain HAZ fracture toughness of a seam weld. The influence of specimen geometry and a/W ratio on fracture toughness was investigated. The Master Curve methodology was employed to characterise HAZ fracture toughness of the seam weld in the ductile-to-brittle transition region. The reference temperature T0 was estimated using the test results obtained on specimens of different geometries and constraint levels. A series of ECAs of the pipe containing a surface axial flaw was performed and the benefits of a constraint based fracture mechanics analysis were demonstrated.
Utilizing In-Line Inspection Data and Structural Reliability Analysis to Set a Defendable Corrosion Re-Assessment Interval
Authors: Sporns Ryan , Bott Steven , Playdon David
Published: October 2008

A quantitative pipeline integrity analysis based on structural-reliability methods has been used to establish corrosion re-assessment intervals from in-line inspection data. This process, as implemented in a simulation-based software package, incorporates in line inspection (ILI) data, physical and operation characteristics of the pipeline, corrosion growth rate projections, and the uncertainties inherent in this information, to estimate the probability of failure (POF) as a function of time. Using this approach, the POF value is calculated on a joint-by-joint basis and the calculated values are then compared with an acceptable POF level to verify the integrity of each joint in any given year. Based on this information a re-assessment interval is established and selected joints are targeted for excavation and repair to ensure that the acceptable POF level is not exceeded.
A First Step Towards the Development of a Pipeline Wrinkle Material Ultimate Limit State
Authors: Dinovitzer Aaron , Tiku Sanjay , Semiga Vlado , Fredj Abdelfettah , Zhou Joe , Yoshizaki Koji
Published: October 2008

While the formation of a wrinkle in an onshore pipeline is an undesirable event, in many instances this event does not have immediate pipeline integrity implications. The magnitude or severity of a wrinkle formed due to displacement controlled loading processes (e.g. slope movement, fault displacement, frost heave and thaw settlement) may increase with time, eventually causing serviceability concerns (e.g. fluid flow or inspection restrictions). Pipe wall damage leading to cracking and eventually a loss of containment involves contributions from the wrinkle formation and growth processes, as well as, wrinkle deformations promoted by in-service line pressure, temperature and seasonal soil displacements. The objective of this paper is to provide an overview of the ongoing research efforts, sponsored by TransCanada PipeLines Ltd. and Tokyo Gas Co. Ltd., towards the development of a mechanics based wrinkle ultimate limits state that may be used in future to evaluate the long term integrity of wrinkled pipeline segments. The research efforts include non-linear finite element modeling to demonstrate the ability of experimentally derived material properties to predict the formation of through wall cracking induced by high and low frequency load effects. This paper outlines the material testing program used to support the development of failure criteria capable of considering the contributions of monotonic deformation, as well as, high and low cycle cyclic loading.
Fatigue Crack Growth Rates in Six Pipeline Steels
Authors: Bussiba A. , Darcis Ph. P. , McColskey J. D. , McCowan C. N. , Kohn G. , Smith R. , Merritt J.
Published: October 2008

This study presents fatigue data for six different pipeline steels, with strengths ranging from Grade B to X100. A fatigue crack growth test for full thickness pipeline samples was developed using a Middle Tension (MT) type specimen. The six steels showed similar fatigue crack growth rate (da/dN) behavior. There were only minor differences among the steels for the threshold values and most of the stable crack growth regime. Larger differences were observed in the final stages of crack growth and fatigue failure. The effect of compressive residual stresses at the outer surface of the pipeline was also examined. A Failure Assessment Diagram technique was used to evaluate the potential failures modes of the six pipeline steels, containing, as an example, an internal surface, semi-elliptic, axially oriented flaw. Mixed-mode failure was predicted for all of the steels.
Impact of Yield to Ultimate Ratio on the Reliability of Burst Limit States
Authors: Maes Marc A. , Salama Mamdouh M.
Published: October 2008

In order to reduce arctic construction and transportation costs, high strength steels (> X80) have been advocated for use in high pressure gas pipelines. These steels differ from conventional steels by exhibiting lower work hardening capacity, lower strain to failure and possible softening of their HAZ. These differences can impact burst limit state and tensile limit state, in addition to crack arrest. In this paper, the impact of the variations in mechanical properties on the reliability of several pipe limit states involving burst is examined. The paper presents the results of burst limit state analysis using state-of-the-art plastic burst models of strain hardening pipe and considering all the uncertainties that impact the margin of safety of pipes subject to internal pressure. Intact pipes, corroded pipes and externally damaged pipes are considered. The analysis focuses on different design check equations (DCE) which “control” the safe usage of the pipe. In addition, the paper looks at how external or internal damage or corrosion affects the burst capacity differently for medium versus high-strength pipelines steels.