bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Capillary Structures for High Performance Heat Pipes
Authors: Stephan P. , Brandt C.
Published: March 2009

High performance heat pipes are widely used for thermal control of electronic devices. Concerning heat transport limitations typical wick or capillary structures show advantages in some aspects and disadvantages in others. An advanced capillary structure was developed with high thermal effectiveness, low axial pressure drop, high capillary pressure, and a high boiling limit. It combines open minichannels with open microchannels that are manufactured perpendicular on top of the minichannels. The heat transfer coefficient in the evaporator zone which is a characteristic value for the thermal effectiveness was up to 3.3 times higher compared to a similar structure without microchannels. A model that combines micro- and macroscopic phenomena was developed. It predicts the heat transfer coefficient with quite good accuracy as long as the microchannels are not smaller than about 300μm.
Experimental Investigation of Single-Phase Flow Pressure Drop Through Rectangular Microchannels
Authors: Tu Xiao , Hrnjak Pega
Published: March 2009

The current work focused on determining the friction factors in five rectangular channels with hydraulic diameters varying from 69.5 to 304.7 μm and with aspect ratios changing from 0.09 to 0.24. The single-channel test sections were carefully designed such that the friction factors could be determined accurately from the experimental data. R134a liquid and vapor were used as the testing fluids. During the experiments, the Reynolds numbers were varied between 112 and 9180. The measured friction factors were compared with the conventional correlations. The results support such a general agreement in the literature that the flow friction in microchannels may be different from the conventional results. However, a more important finding is that when the channel surface roughness was low, even for the smallest channel tested, both the laminar friction factor and the critical Reynolds number approach the conventional values. In the turbulent region, the surface roughness has great effect on the flow friction even for the smoothest channel tested (Ra/Dh = 0.14%).
Two-Phase Pressure Drop of CO2 in Mini Tubes and Microchannels
Authors: Yun R. , Kim Y.
Published: March 2009

Two-phase pressure drops of CO2 are investigated in mini tubes with inner diameters of 2.0 and 0.98 mm and in microchannels with hydraulic diameters from 1.08 to 1.54 mm. For the mini tubes, the tests were conducted with a variation of mass flux from 500 to 3570 kg/m2s, heat flux from 7 to 48 kW/m2, while maintaining saturation temperatures at 0°C, 5°C and 10°C. For the microchannels, mass flux was varied from 100 to 400 kg/m2s, and heat flux was altered from 5 to 20 kW/m2. A direct heating method was used to provide heat into the refrigerants. The pressure drop of CO2 in mini tubes shows very similar trends with that in large diameter tubes. Although the microchannel has a small hydraulic diameter, two-phase effects on frictional pressure drop are significant. The Chisholm parameter of the Lockhart and Martinelli correlation is modified by considering diameter effects on the two-phase frictional multiplier.
Marangoni Convection in Capillary Tubes Filled With Volatile Liquids
Authors: Buffone C. , Sefiane K.
Published: March 2009

The work is an experimental investigation of the evaporation process from a liquid meniscus formed in capillary tubes of various sizes (ranging from 200 to 900 μm). The results have been compared with those of a previous analytical work and show how the strong convection in the liquid phase is responsible for the discrepancy found. In the analytical prediction the evaporation process is sustained only by diffusion and in this model the meniscus position vs. time is a linear function of the tube size; instead, our experimental results show how this parameter is inversely correlated with the pore size. The surface roughness of the tubes was characterized and particular care has been devoted to the capillaries’ cleaning procedure from which wetting properties are strongly dependent. Marangoni convection prevails at tube sizes less than one millimeter in diameter as in the present case, while at larger sizes a coupling between Marangoni and Rayleigh convection is expected. The Marangoni roll of thoroidal shape in the liquid phase has been visualized and characterized using seeding particles. As pointed out clearly in the present study, Marangoni convection enhances the heat-mass transfer from a pore.
Industrial Microchannel Devices: Where Are We Today?
Authors: Pua Lee M. , Rumbold S. O.
Published: March 2009

Heatric has been involved in the commercial design and manufacturing of “micro/milli” scale heat exchanger core matrices called Printed Circuit Heat Exchangers (PCHEs) since 1985. These core matrices are formed by diffusion bonding together plates into which fluid flow microchannels have (usually) been formed by photo-chemical machining. Complex fluid circuitry is readily implemented with this technique. Diffusion bonding is a ‘solid-state joining’ process creating a bond of parent metal strength and ductility. The complete microchannel heat exchangers are highly compact, typically comprising about one-fifth the size and weight of conventional heat exchangers for the same thermal duty and pressure drops. PCHEs can be constructed out of a range of materials, including austenitic stainless steels suitable for design temperatures up to 800°C, and nickel alloys such as Incoloy 800HT suitable for design temperatures more than 900°C. Single units ranging from a few grams up to 100 tonnes have been manufactured. Currently there are thousands of tons of such microchannel matrix in hundreds of services — many of them arduous duties on offshore oil and gas platforms where the size and weight advantages of microchannel heat exchangers are of obvious benefit. Whilst these matrices are predominantly involved in thermally simple two-fluid heat exchange, albeit at pressures up to 500 bar, PCHEs have also been used for many multi-stream counter-flow heat exchangers. However the field of applications is very varied, including specialised chemicals processing, and PCHEs are even to be found orbiting the Earth in the International Space Station! Due to the inherent flexibility of the etching process, the basic construction may readily be applied to both a wider range, and more complex integration of process unit operations. Chemical reaction, rectification, stripping, mixing, and absorption, as well as boiling and condensation, can be incorporated into compact integrated process modules. Crucially, the resulting degree of compactness has led printed circuit technology to be the enabling technology in certain duties. Techniques for chemical coating onto the surfaces of channels continue to evolve, with applicability both to protective coatings and catalytically active coatings. We will describe a selection of innovative printed circuit technology examples. Alongside the more esoteric, Heatric is actively extending printed circuit technology to adapt to new market opportunities such as nuclear power generation plant and fuel cell systems. These applications perhaps represent two extremes of the both size and process integration, and thus aptly serve to demonstrate the range of industrial use of microchannel devices.
Effect of Particle Sticking on the Micro-PIV Measurement in a Micro-Bypass Channel Flow
Authors: Kim Kyung Chun , Yoon Sang Youl , Ji Ho Seung
Published: March 2009

Micro-resolution Particle Image Velocimetry (Micro-PIV) was used to measure the flow in a micro-branch (Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel (200μm width×80μm height) and two branches which has 100μm width×80μm height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction (enterance, middle and exit of branch) and five planes along vertical direction (0,± 10,±20μm) for the range of Re = 0.24, 1.2, 2.4. Numerical simulation was done to compare with the measurements and understand the effects of particle lump at the tip of branch.
Temperature Measurements and Surface Visualization in Microchannel Flows Using Infrared Thermography
Authors: Narayanan Vinod
Published: March 2009

Significant developments in detailed quantitative microscale fluid flow visualization have been made in recent years. However, spatially resolved surface temperature measurements in microchannels have received far less attention. This paper introduces quantitative and qualitative surface temperature measurement in microscale flows using infrared (IR) thermography. This technique is applicable for channel dimensions of up to 10 μm. In order to determine temperatures accurately, careful attention toward proper choice of windows, elimination of specular reflections from channel walls, and estimation of local emissivity changes is warranted. These concerns are addressed in the paper, and preliminary results of detailed temperature distribution in a single-phase mini-channel flow are presented.
Three Distinct Types of Morphological Responses of Cultured Vascular Endothelial Cells to Physiological Levels of Fluid Shear Stress
Authors: Masuda Michiaka , Fujiwara Keigi
Published: March 2009

Vascular endothelial cells are known to respond to fluid shear stress. To gain insights into the mechanism of flow response by these cells, various types of in vitro devices in which endothelial cells can be cultured under flowing culture medium have been designed. Using such a device, one can apply known levels of (usually laminar) fluid shear stress to cultured endothelial cells. We have made two types of devices: a viscometer-based cone-and-plate flow apparatus and a parallel plate chamber. The cone-and-plate apparatus is used to do biochemical analyses of flow effects on cells while the parallel plate chamber is used to observe dynamic behavior of endothelial cells under flow. We were able to maintain confluent endothelial cell cultures under flow for over a week in the parallel plate flow apparatus. Using this chamber and high resolution time-lapse video microscopy, we studied morphological changes of endothelial cells exposed to different levels of fluid shear stress. We found that endothelial cells in a confluent monolayer exhibited three types of fluid shear stress level-dependent morphological and motile responses within a narrow fluid shear stress range between 0.1–10 dyn/cm2. Endothelial cells cultured under no flow exhibited variable shapes and no preferred orientation of their long cell axes and showed a jiggling motion. When exposed to fluid shear stress levels of below 0.5 dyn/cm2, endothelial cell morphology and motility were not affected. However, when fluid shear stress levels were increased to 2–4 dyn/cm2, they became polygonal and showed increased random-walk activity. Fluid shear stress over 6 dyn/cm2 caused endothelial cells to initially become polygonal and increase their random-walk activity, but they soon became elongated and aligned in the direction of flow. As the cells elongated and aligned, they migrated in the direction of flow. The average velocity of this directed cell migration was less than that of cells moving randomly under the same flow condition at earlier times. These observations indicate that endothelial cells are able to detect and respond to a surprisingly small change in fluid shear stress. It is possible that endothelial cell physiology in vivo is also regulated by small changes in fluid shear stress and that a fluid shear stress change of a few dynes per cm2 within a certain region of an artery could trigger atherogenesis in that particular location.
Improving Natural Draft Cooling Tower Performance With Heat Injection
Authors: Grindle Eugene , Cooper John , Lawson Roger
Published: March 2009

This paper presents an assessment of heat injection as a means of improving natural draft cooling tower performance. The concept involves injecting heat into the cooling tower exit air/vapor stream immediately above the drift eliminators in order to increase the difference between the density of the exit air/vapor stream and the ambient air. The density difference between the air/vapor in the cooling tower stack and the ambient air is the engine that drives airflow through the cooling tower. The enhancement of the airflow through the cooling tower (the natural draft) results in more evaporation and thus lowers the circulating water temperature. Because the heat is injected above the drift eliminators, it does not heat the circulating water. To evaluate the cooling tower performance improvement as a function of heat injection rate, a thermal/aerodynamic computer model of Entergy’s White Bluff 1 & 2 and Independence 1 & 2 (approximately 840 MW each) natural draft cooling towers was developed. The computer model demonstrated that very substantial reductions in cold water temperature (up to 7°F) are obtainable by the injection of heat. This paper also discusses a number of possible heat sources. Sources of heat covered include extraction steam, auxiliary steam, boiler blow-down, and waste heat from a combustion turbine. The latter source of heat would create a combined cycle unit with the combination taking place in the condensing part of the cycle (bottom of the cycle) instead of the steam portion of the cycle (top of the cycle).
Kinetic Study of Waste Wood and Its Carbonization
Authors: Mozammel Hoque Md. , Ota Masahiro
Published: March 2009

This study deals with the conversion of waste wood into solid fuel charcoal. Thermogravimetric and differential thermal analyses techniques are used to investigate the kinetics of thermochemical conversion of waste wood. The thermal degradation characteristics and the kinetic parameters (order of reaction, activation energy and pre-exponential factor) are determined at different heating rates using TG/DTA curves. The decomposition of the components could be modeled by an Arrhenius kinetic expression. The kinetic parameters are determined from the thermogravimetric data by a least square technique. The order of reaction and activation of energy vary from 0.41 to 0.52 and 10.86 to 15.10 kJ/mole respectively. Finally attempts are taken to produce charcoal from the waste wood and the charcoals are characterized in respect of yield, electrical conductivity, ESCA (electron spectroscopy for chemical analysis), XRD (x-ray diffraction) and ignition characteristics.
A Numerical Investigation of Turbulent Non-Premixed Nozzle-Mixed Industrial Burner
Authors: Stralin Per , Mukhopadhyay Achintya , Puri Ishwar K.
Published: March 2009

Nozzle-mix burners are widely used in heat treatment and non-ferrous melting furnaces, and other applications, where temperature uniformity is required. These burners are stable over a wide range of air-fuel ratios from very lean to rich (up to 50% of excess fuel), high turndown ratio and low NOX emissions at all air-fuel ratios. Here, the fuel is generally transported by a central jet and air through an annular jet. The separation between the fuel jet and the air annulus and confining wall are crucial for flame stabilization. The objective of the present work is to investigate the flow and flame characteristics of a nonpremixed nozzle-mix burner through a detailed parametric study. The inferences from this study will provide useful information for designers, regarding choice of parameters. The burner is modeled as an axisymmetric arrangement of fuel duct at the center, surrounded by a coaxial annular duct of air. The ducts discharge into a confined environment, formed by a chimney, placed coaxially with the ducts. The results of the numerical simulation show that for a given air-fuel ratio, as the fuel flow rate increased, the location of the flame base shifted from near the fuel nozzle towards the oxidizer nozzle. Similar shift in flame position was also observed for higher air velocities for a given fuel velocity. High fuel and air flow rates and small separation between fuel and air jets tend to destabilize the flame. For a given air-fuel ratio, flame height increased with increase in fuel flow rates, but the change became insignificant at higher flow rates. For a given fuel velocity, flame height decreased with increase in air flow rate for both buoyancy-controlled and momentum-controlled regimes. The air-to-fuel velocity ratio was found to be the most significant parameter in determining the flame height.
Achieving Uniform Combustion Using Burner Line Orifices to Balance Coal Flow Distribution
Authors: Haumesser F. P. , Thompson R. E. , Davey T. A. , Kuipers J. N.
Published: March 2009

The combination of more stringent NOx regulations and utility heat rate improvement programs has led to an increased interest in balancing coal flow distribution to burners to improve combustion. Uniform low O2 combustion is essential to minimizing NOx emissions without adversely impacting combustible losses (CO and LOI). Many retrofit low-NOx burner installations require balanced coal flows from each pulverizer to the burner pipes to within ± 10% of the mean in order to meet these goals. Numerous questions have arisen concerning the best methods to measure, achieve, and maintain a balanced coal flow distribution from the pulverizer to the burners. These questions concern: 1) the validity of clean air vs. “dirty” air primary air velocity measurements, 2) ASME vs. ISO “RotorProbe™” pulverized coal sampling methods, 3) fixed vs. adjustable burner line orifices, and 4) the performance of continuous on-line coal flow instrumentation. Some have questioned the need for or effectiveness of using orifices to balance coal flow distribution, while others have argued that deviations between burner line coal flows should not exceed as little as ±5% of the mean (pipe-to-pipe) within a pulverizer. This paper addresses many of the questions concerning the effectiveness of balancing coal flows with orifices. Extensive test data are presented documenting the improvement in coal flow balance using orifices on over 25 boilers. This experience covers units ranging in size from 110 to 750 MWe, equipped with roller, ball tube and exhauster type pulverizers, and for both wall-fired and T-fired burner configurations. The improvement in combustion uniformity achieved by balancing burner line coal flow distribution is illustrated by a comparison of economizer exit duct emission profiles before and after orifice application. This paper also addresses questions concerning: 1) maintaining a coal flow balance over time, 2) variations in coal flow balance with pulverizer load, and 3) recent developments in burner line continuous coal flow monitoring. Test data are included which compare coal flow measurements made with a RotorProbe™ and a microwave real-time coal flow measurement system.
Leveraging Physical and Computational Flow Modeling Techniques in the Optimization of Commercial Selective Catalytic Reduction System Designs
Authors: Anderson David K. , Kozlak Martin J.
Published: March 2009

To ensure optimal SCR system performance, physical and computational flow models of proposed SCR installations are used to guide the development of system components, such as the ammonia injection grid and various flow and thermal conditioning devices. Proper attention to these details is particularly important in retrofit applications where the ducts leading to the SCR reactor often cannot be designed for optimal fluid flow characteristics. This paper discusses the process of SCR modeling including the techniques employed to accurately model gas flow, NOx, ammonia, and thermal distributions and mixing. Additionally, the development of economizer bypass systems for SCR temperature control during low-load operation is discussed.
A Note About the Sensitivity Curve of Compensated Volume Balance Leak Detection Systems
Authors: de Freitas Rachid Felipe Bastos , Carneiro de Araujo Jose´ Henrique , Baptista Renan Martins
Published: March 2009

This work presents a simple theoretical development which aims to derive the sensitivity curve of compensated volume balance leak detection systems. The analysis carried out is not limited to steady state and also automatically provides the bounds with which the sensitivity curve is predicted, as a function of the system uncertainties. It is demonstrated that the performance of leak detection systems of this nature depends upon the operation of the pipeline at the time instants of the leak onset and of leak detection. As a result, it is also shown that there are an upper and a lower bounds of the minimum response time and that the minimum detectable leak is independent of the pipeline operational regime, being equal to the overall flow rate measurement uncertainty.
Pipeline Installation in a Confined Location Under the Bow River by Horizontal Directional Drilling
Authors: Zhou Joe , Glover Alan , Rudge Paul
Published: March 2009

In the summer of 2000, TransCanada PipeLines Ltd. (TransCanada) upgraded portions of the Western Alberta System (WAS) NPS 36 gas pipeline through the town of Cochrane Alberta. The pipeline upgrade required the installation of new sections of pipe to meet the higher Class Location designation due to population density increase. Environmental concerns, expressed by federal and provincial regulators and the Cochrane community for the in-stream disturbance associated with a conventional “open cutting” installation, prompted TransCanada to design a directionally drilled crossing. A unique challenge to this project was the Bow River crossing within a congested and restricted right of way. The project team developed and implemented a series of innovative solutions which led to the successful conclusion of the project in September 2000. This paper summarizes the unique design and construction implemented in this project.
Fracture Toughness Estimation for Pipeline Girth Welds
Authors: Pisarski Henryk G. , Wignall Colin M.
Published: March 2009

The relationship between fracture toughness estimated using standard single edge notch bend (SENB), single edge notch tension (SENT) test specimens and fracture toughness associated with a circumferential flaw in a pipe girth weld is explored in terms of constraint using the Q parameter. It is shown that in the elastic-plastic regime, use of standard deeply notched SENB specimens provides a conservative assessment of fracture toughness, for both weld metal and HAZ, because of the high constraint associated with this specimen geometry. Use of specimen geometries and loading modes associated with lower constraint (e.g. SENT and shallowed notched SENB specimens), allow for improved estimates of fracture toughness to be made that are appropriate for the assessment of circumferential flaws in pipe girth welds. Recommendations are given on the specimen designs and notch orientations to be employed when evaluating weld metal and HAZ fracture toughness.
Field Assessment of FBE-Coated Pipelines and the Implications for Stress Corrosion Cracking
Authors: King Fraser , Cheng Yufeng , Gray Linda , Drader Brent , Sutherby Robert
Published: March 2009

One proposed method for preventing the initiation of SCC on pipelines is through the use of high-performance coatings in conjunction with effective cathodic protection. High-performance coatings include fusion bonded epoxy (FBE), urethanes, liquid epoxies, extruded polyethylene, and multi-layer coatings. This paper reports the results of a CEPA-sponsored project to determine the long-term performance of FBE coatings on underground pipelines using in situ field measurements. The barrier properties of FBE coatings were measured after several years field service using Electrochemical Impedance Spectroscopy (EIS). Measurements were made on four FBE-coated pipelines that had been exposed for periods of between 5 and 20 years. The coatings studied included three different formulations from two different manufacturers. A variety of site, soil and CP conditions were also examined. The combination of EIS measurements and analyses of trapped water samples demonstrated that the FBE coatings continued to perform well after having been exposed for up to 20 years. Although some blistering and disbondment was observed in some cases as a result of poor application and storage procedures, in all cases the pipe surface was still protected either by the coating itself or by the joint action of the CP system and the CP-compatible FBE coating. The results of this study provide strong evidence that FBE-coated pipelines should not be susceptible to the initiation of SCC, due to (i) the barrier properties of the coating, (ii) the CP-compatible nature of the coating, and (iii) good surface preparation techniques that involve the removal of millscale and the introduction of compressive surface residual stresses.
Groundwater Quality in the Vicinity of CP Groundbeds
Authors: Ikeda-Cameron Katherine , Stehmeier Les , Jack Tom , Worthingham Robert
Published: March 2009

Impressed current cathodic protection systems are widely used to provide corrosion protection for buried steel structures. Application of these systems includes installation of metallic anodes underground that gradually dissolve over the service life of a groundbed. This presentation will discuss field monitoring of groundwater quality in the vicinity of a shallow anode bed for possible soluble metal contamination arising from the dissolution of the anodes or other processes. To date soluble metal ion concentrations and hydrogeological modeling support the view that metals such as chromium, nickel, boron, copper and vanadium released in soluble form by dissolution of the anode do not pose a threat to groundwater quality.
Determination of the Region of Steady-State Crack Growth From Impact Tests
Authors: Wilkowski Gery M. , Rudland David L. , Wang Yong-Yi , Horsley David , Glover Alan , Rothwell Brian
Published: March 2009

Large-diameter gas pipelines typically have a design requirement to ensure that the toughness is sufficient to avoid brittle or ductile fractures from occurring. New pipeline design requirements with richer gases, higher-grade steels, higher operating pressures, and in some cases lower operating temperatures require considerable extrapolation of the current ductile fracture design equations. To obtain a better understanding of ductile fracture arrest toughness, TCPL has funded efforts to assess the steady-state fracture toughness from specimens that can be used in mill applications. This paper reviews past efforts to assess the regions of steady-state ductile crack growth in test specimens, as well as current test results from numerous highly instrumented impact specimens. The new test results were for X52, X70, and X80 linepipe steels, whereas the past efforts were from linepipe steels, aerospace materials, as well as ferritic and austenitic nuclear piping steels. All of these results show that there is a limited region over which the steady-state fracture resistance can be determined. The fracture energy associated with steady-state fracture is the total energy minus; (1) the energy associated with initiation of the crack (including indentation energy and global yielding of the specimen), (2) the transient crack growth from initiation to reaching steady-state fracture, and (3) a non-steady-state fracture region at the end of the test record. Instrumented load versus load-line displacement data were linked to high-speed digital video data of the crack growth, crack-tip-opening angle (within 2 mm of the crack tip), and crack-mouth-opening displacement. These data allowed for comparison of J-R curves and crack-tip-opening angle values during crack growth to help determine the regions of steady-state crack growth. The results from these efforts are an important consideration in the development of a single test specimen method that can be used for determining the ductile fracture resistance of high-strength and high-toughness linepipe steels.
Concepts and Production Results of Heavy Wall Linepipe in Grades up to X 70 for Sour Service
Authors: Liessem Andreas , Schwinn Volker , Jansen Jean-Pierre , Poepperling Rolf K.
Published: March 2009

This paper summarizes the main mechanism and influencing factors for Hydrogen Induced Cracking. The evolution of HIC test requirements over nearly 30 years for linepipe intended for sour service are reviewed. Some typical examples of the requirements for sour service pipe production at Europipe (formerly Mannesmann) developed over the past 20 years and the details of trial production of sour service pipes in grade X 70 with 30 mm wall thickness are presented. However, with the steadily increasing demands it becomes progressively more difficult to fulfill the before mentioned standard test conditions. In those cases where the overall profile of requirements (strength, toughness) can not be consistently achieved, fit-for-purpose testing methods are currently emerging. As an example the results of a pipe order, where the fit-for-purpose approach has been used to qualify the pipe for a special project, will be described.
Conformable Eddy Current Array for Mapping External Pipeline Corrosion
Authors: Crouch Alfred E. , Burkhardt Gary L. , Porter Patrick C.
Published: March 2009

In a new project sponsored by the U.S. Department of Energy’s National Energy Technology Laboratory, feasibility is being determined for a convenient, affordable method to map corrosion on the outside surface of pipelines. The goal of the project is a system that can produce a contour map of a corroded area and be easily deployed in the field by pipeline maintenance personnel. The collected data will support assessment algorithms such as B31G and RSTRENG (Remaining Strength), which rely on three-dimensional corrosion sizing. The array will be made up of multiple eddy current sensors, scanned electronically to collect data that represent local wall-loss measurements. The work is being performed at Southwest Research Institute and is building upon the results of an earlier project concerned with graphitic corrosion in cast iron pipe. Technical assistance is being provided by Clock Spring Company, who is cofunding the project and planning to commercialize the system if it proves feasible. This paper presents the basic measuring technology, results of laboratory testing of breadboard coils and a description of the proposed field operating procedure.
The Influence of Pipeline Diameter Variation on the Mixing Volume in Batch Transfers
Authors: de Freitas Rachid Felipe Bastos , Carneiro de Araujo Jose´ Henrique , Baptista Renan Martins
Published: March 2009

Presented in this paper is a new model for estimating mixing volumes arising in batch transfers in multiproduct pipelines, when variations of the line diameter as well as injection and/or withdrawal of products are present. Besides these novel features, the model incorporates the flow rate variation with time and the use of a more precise effective dispersion coefficient, which is considered to depend on the concentration. The governing equations of the model form a non-linear initial-value problem that is solved by using a predictor-corrector finite difference method. A comparison among several cases studied reveals that the pipeline diameter variation can effectively reduce the amount of mixing volume when compared to a similar transfer carried out in a constant diameter line.
Material Property Effects on Critical Buckling Strains in Energy Pipelines
Authors: Dorey Alfred B. , Murray David W. , Cheng J. J. Roger
Published: March 2009

Investigations in the development of a predictive critical buckling strain equation have shown that the grade of the material is one of five fundamental non-dimensional parameters in determining the critical local buckling strain for line pipe under combined loads. Further to this, the shape of the material curve also plays a significant role in the resulting critical buckling strain. Over 50 full-scale test specimens have been tested at the University of Alberta and effective numerical finite element analytical models have been developed. A parametric study consisting of 170 analyses was performed using the numerical models and critical buckling strain equations were derived. One of the essential variables in the new equations is a function of the specimen’s material properties. The results indicate that the higher the grade of the material the lower the value of the critical buckling strain. Furthermore, the level of agreement between the new equations and the experimental data was found to be dependent on the shape of the material curve for the specimen. Experimentally, two basic material curve shapes were observed, namely: specimens with a “rounded” material curve through the yield strength and specimens with a material property that exhibited a distinct “yield plateau” or yield point. Comparison of the experimental and numeric data showed that the specimens that were fabricated from material with a distinct yield plateau had different critical buckling strains when compared to specimens tested with rounded material curves. A subsequent parametric study was undertaken to examine the effect that the different shaped material curves had on the local and global behaviour. The results of this subsidiary parametric study showed that the global moment capacity was essentially independent of the shape of the material curve (the ratio of the peak moment from the yield plateau material to the peak moment for the rounded material was 1.018). However, the local critical buckling strain was significantly lower for the specimens analyzed with the material that had the yield plateau (the ratio of the critical strains for the two different material curves was 0.710).
Near-Neutral pH SCC Initiation and Early Propagation of X70 Pipeline Steel
Authors: Lu Baotong , Luo Jingli , McCrady Brian
Published: March 2009

The near-neutral pH SCC initiation and propagation behavior of X70 pipeline steel was investigated using dog-bone specimens with two different surface conditions, the original external pipe surface and a ground surface. The tests were conducted in NS4 solution de-aerated with N2/5%CO2, under low frequency cyclic load (v = 0.1Hz, R = σmin/σmax = 0.5). The fractography shows that the transgranular crack morphology of near-neutral pH SCC is reproduced under the current test condition. In line with the crack initiation mechanisms, the cracks observed are divided into two types, pit cracks and non-pit cracks. Non-pit crack initiation is found to be the dominative mechanism for the original external pipe surface but the contribution of pit cracks depends on the test duration. The test results indicate that the crack initiation rate increases and the crack initiation life decreases with increasing applied stress level. The crack propagation rate is essentially independent of the applied stress level. Finally, the effects of surface condition and non-metallic inclusions on the SCC mechanism of pipeline steels are discussed.
Room Temperature Creep Behaviour of Pipeline Steels and Its Influence on Stress Corrosion Cracking
Authors: Chen Weixing , Wang Sheng-Hui
Published: March 2009

Room temperature creep is often of significant importance in structural materials. Its occurrence, for example, may be an important factor contributing to crack growth during stress corrosion cracking. For pipeline steels used in gas transmission, room temperature creep deformation near the crack tip may result in a time dependent crack growth. In this research, room temperature creep of two pipeline steels with different grades was studied under various loading conditions including pure static, pure cyclic and a combination of static and cyclic loading. The creep deformation under a stress higher than the yield strength may represent the deformation behaviour at the crack tip. Due to cyclic hardening, all the steels crept at a stress higher than the yield strength exhibit cyclic creep retardation, which is less pronounced at lower stress-ratio (minimum stress/maximum stress). Pre-cyclic loading has significant effect on subsequent static creep. In general, pre-cyclic loading causes a burst of creep deformation under subsequent static loading, which may result in significantly larger cumulative creep strain than that of pure static creep depending on the initial loading strain and the number of cycles in pre-cyclic loading. The burst in creep deformation requires an incubation period that increases with number of prior load cycles. The burst strain is dependent on the number of cycles of prior cyclic loading in a more complicated manner. The implication of the creep behaviour observed in these tests is also discussed in terms of stress corrosion cracking in the pipeline steels.
Technology Approaches for Northern Pipeline Developments
Authors: Glover Alan , Zhou Joe , Blair Brian
Published: March 2009

Traditional pipeline technology will be severely challenged as developments continue in arctic regions. Cost-effective solutions to these challenges can be found through innovative technology and its implementation. TransCanada PipeLines has been involved in a series of technology programs that have been implemented in challenging climates including permafrost. In addition TransCanada is also involved in ongoing programs whose aim is to reduce the cost of Northern pipelines whilst at the same time provide structural assurance and reliability. This paper will describe the overall approach to developing cost-effective solutions and how these programs are interconnected. The topics to be covered will include the approach to strain-based design and how TransCanada has been taking advantage of the approach in its implementation of higher strength steels. The work also includes the approach taken in terms of the design for the effect of mismatch between the pipe and weld metal properties. The strain-based approach is also being extended to a structural reliability methodology and the work conducted to date will be briefly discussed. A significant portion of the design of a Northern pipeline relies on the development of a frost heave-thaw settlement methodology and the current philosophy and its validation will be discussed. A prime consideration of the regulatory bodies is the assurance of structural integrity and fracture control plans. The work currently ongoing at TransCanada on fracture safe behaviour will be discussed. Additional discussion on construction related topics will be covered including welding, buoyancy control, directional drilling and trenching.
A Model to Predict the Effect of Pre-Strain on the Fracture Toughness of Line Pipe Steel
Authors: Cosham Andrew , Hagiwara Naoto , Fukuda Naoki , Masuda Tomoki
Published: March 2009

New and existing pipelines can be subjected to high plastic strains. Denting a pipeline causes permanent plastic deformation. Onshore pipelines subject to subsidence, frost heave or earthquake loading can experience significant plastic strain during service. Offshore pipelines that are reeled prior to laying, or are laid in deep water, or are operating at high temperatures and high pressures, can experience significant plastic strain both prior to, and during, service. Experimental studies have indicated that pre-strain (permanent plastic deformation) has a detrimental effect on the fracture toughness of steel; it reduces the resistance to crack initiation, reduces the resistance to crack growth, and increases the transition temperature. Consequently, there is a need for a thorough understanding of the effect of pre-strain on the fracture toughness of line pipe. Accordingly, a theoretical model for predicting the effect of tensile pre-strain on the ductile fracture toughness has been developed using the local approach. The effect of pre-strain is expressed in terms of an equation for the ratio of the fracture toughness of the pre-strained material to that of the virgin (not pre-strained) material. The model indicates that the effect of tensile pre-strain on the material’s fracture toughness can be characterised in terms of the effect of pre-strain on the stress-strain characteristics of the material, the critical fracture strain for a stress state corresponding to that during pre-strain, and several parameters that relate to the conditions for ductile fracture (or cleavage fracture). The implications of the model are that it may be possible to estimate the reduction in toughness caused by pre-strain simply from a full stress-strain curve of the virgin material. The model has been validated against the results of crack tip opening displacement (CTOD) tests conducted by Tokyo Gas on two line pipe steels subject to uniaxial tensile pre-strain. It is shown that the predictions and trends of the theoretical model are in broad agreement with the test results.
Prevention, Preparedness, Response and the Bottom Line
Authors: Rathwell Terry G.
Published: March 2009

This paper discusses the relationship between the management of health, safety and the environment (prevention, preparedness and response) at various phases of pipeline development and operation and the costs and cost benefits associated with this essential management function. HSE management systems are an integral component of all phases of pipeline activity, including concept and design, construction, commissioning, operation and maintenance. Effective HSE management systems are not free and they do involve immediate expenditures of time, resources and money. Future gains are very real but are often difficult to measure in dollars. Future gains may include reduced WCB costs, reduced equipment damage and downtime, reduced property damage claims, reduced production interruptions, improved production quality, improved employee morale, improved customer satisfaction and market share. Management decides the level of expenditure for incident prevention, preparation and response. One approach is to spend little or nothing in advance of a potential incident and react only after an event to correct the conditions that caused the loss. This is unwise. Another approach is to spend the sums needed to cover every conceivable contingency. This is imprudent. We must learn to balance risk and control in an effort to seek an optimum expenditure for all phases of pipeline design, construction, commissioning, operation and maintenance. This paper will discuss the ways and means to accurately assess the costs of actual and potential incidents to learn what the costs are, when and how these costs are incurred and how costs can be minimized. Only when costs are established and understood can we develop appropriate plans to negate these costs. We must learn the difference between the control of costs and the causes of costs relating to health, safety and the environment.
Sandwich Pipes for Ultra-Deep Waters
Authors: Netto T. A. , Santos J. M. C. , Estefen S. F.
Published: March 2009

Pipeline systems for deepwater applications must be designed to withstand operational loads and to give adequate thermal insulation to the hydrocarbon being transported. Sandwich pipelines composed by inner and outer steel pipes and either cement or polypropylene as core material are proposed here as viable alternatives to currently used pipe-in-pipe systems. The main advantage of these sandwich structures is that the core material and geometry can be selected so to provide both thermal insulation and good structural performance in conjunction with inner and outer pipes. In this paper, the structural behavior of such sandwich pipes under external pressure is studied through a series of small scale experiments and nonlinear numerical analyses based on the finite-element method.
Thermal Benefits With Subsea Heat Bank
Authors: Falk Kristin , Killie Rune , Ha˚heim Svein , Damsleth Per
Published: March 2009

Subsea production of oil and gas involves structures on the seabed such as manifolds and X-mas trees that require thermal insulation of piping and valves to avoid gas hydrate formation. The insulation is expensive and time consuming to apply yet may still leave areas with inadequate protection. These “cold spots” accelerate the cooling during a production shutdown. A Heat-Bank concept is developed as an alternative to conventional insulation. The entire subsea structure is covered with an insulated shell. During shutdowns the heated fluid inside the cover keeps the production equipment warm over a prolonged period before hydrates start to form. Computational Fluid Dynamics (CFD) simulations are used to quantify the heat loss effects of natural convection and leakage through openings in the cover. The CFD analyses demonstrate the relative performance of the concept compared to the traditional method of insulating individual piping components. Application of the Heat-Bank concept opens new possibilities for environmentally friendly and cost-effective field development, especially for deep water.
Collision Risk Analysis of FPSO-Tanker Offloading Operation
Authors: Chen Haibo , Moan Torgeir
Published: March 2009

Collision between FPSO and shuttle tanker in tandem offloading operation has caused a growing concern in the North Sea. Several recent contact incidents between FPSO/FSU and shuttle tanker have clearly demonstrated a high likelihood of contact between vessels in tandem offloading. The large masses involved, i.e. high potential impact energy, make the collision risk large. Traditional ship/platform collision risk model may not be effective for tandem offloading operation. Further more in a broader sense, offshore quantitative risk analyses generally focus more on technical aspects, little on human aspects. This leads to a hardware-centered risk control approach, which may not be effective in the face of risks in complex marine operations. A collision risk modeling approach for FPSO and tanker offloading operation is presented in this paper. The collision frequency is modeled in the initiating stage and the recovery stage. In the initiating stage, this paper is focused on tanker powered forward movement (PFM) scenarios. The initiation of tanker PFM involves a complex man machine interaction. The risk model is set up which integrates technical events, human actions and their interaction in the initiating stage. This model guides us further to identify the two failure prone situations where man machine interaction happened and resulted in most collision incidents. The study to quantitatively analyze these failure prone situations and minimize their occurrence is presented in a companion paper OMAE 28101. In the recovery stage, this paper is focused on the tanker initiated recovery. Based on the proposed probabilistic model for the recovery stage, possible recovery actions are identified and the event development is modeled from initiation of tanker PFM to the final outcome, i.e. collision or near miss. The success of recovery is analyzed from the human action timing perspective. Based on qualitative and preliminary quantitative analyses, recommendations are made to reduce the failure of recovery in design and operation.