bluuebunny/crossref_metadata_2025 huggingface dataset:
Convective Boiling of R-22 in a Flat Extruded Aluminum Multi-Port Tube
Authors: Kim Nae-Hyun , Sim Young-Sup , Min Chang-Keun
Published: December 2008

Convective boiling heat transfer coefficients of R-22 were obtained in a flat extruded aluminum tube with Dh = 1.41 mm. The test range covered mass flux from 200 to 600 kg/m2 s, heat flux from 5 to 15 kW/m2 and saturation temperature from 5°C to 15°C. The heat transfer coefficient curve shows a decreasing trend after a certain quality (critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique ‘cross-over’ of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kandlikar correlations underpredict the low mass flux and overpredict the high mass flux data.
Flow Boiling Heat Transfer and Flow Pattern in Rectangular Channel of Mini-Gap
Authors: Yang Yang , Fujita Yasunobu
Published: December 2008

Flow boiling in micro- and mini-channels has attracted much attention in recent years. But the phenomena is such confined channels have not been fully understood and explained. Some conclusions reached by different authors are even contradictory. The present research is trying to study some aspects of flow boiling in mini- and micro-channels. In the present paper boiling heat transfer and two-phase flow patterns in rectangular narrow channels were studied. The gap size of the channel was varied as 2, 1, 0.5 and 0.2 mm with the channel width and length being kept at 20 mm and 100 mm, respectively. In the present mini- and micro-channels, four flow patterns were identified; bubbly, intermittent, wavy and annular flow. They can be also divided into several sub-flow patterns. Flow patterns showed strong channel gap size dependence. Smaller gap size deleted bubbly flow, thus induced simpler flow patterns to shift the annular flow at lower vapor quality. The channels can be divided into two groups depending on the gap size; the larger gap group of 2 and 1 mm, and the smaller gap group of 0.5 and 0.2 mm. The larger gap group showed similar heat transfer behavior as conventional size of tubes. The smaller gap group indicated some peculiar phenomena. Heat transfer coefficient in the smaller gap group was relatively high in the low quality region. Then heat transfer coefficient decreased monotonously with increasing vapor quality. This behavior was considered attributable to the micro-bubble generation in the channel corners and an early partial dryout of thin liquid film. Thus the relationship between heat transfer coefficient and flow pattern should be carefully pursued in micro- and mini-channels to develop heat transfer correlations based on flow patterns.
Experimental Study of Heat Transfer, Pressure Drop, and Dryout for Flow Boiling of Water in an Oil Heated Minichannel
Authors: Campbell Levi A. , Kandlikar Satish
Published: December 2008

Heat transfer and pressure drop, are experimentally recorded for flow boiling water in a single 706 μm circular copper channel 158.75 mm long. Heat is supplied by heat transfer oil at specified temperatures to a helical channel in the test section. In contrast to other current experimental techniques for flow boiling in small diameter tubes, a uniform temperature boundary condition is employed rather than a constant heat flux condition. The principal results of these experiments are two-phase flow boiling heat transfer rates and an analysis of the time-dependent pressure drop signature during two-phase flow in a minichannel. The range of experiments includes mass fluxes of 43.8–3070 kg/m2s and wall temperatures of 100°C–171.2°C. In all cases the test section water inlet is subcooled to between 72.9°C and 99.6°C. The inlet pressures used are 1.1–230.5 kPa (gage).
An Optimized Design of the Refrigerating Systems Using a Small Channel Heat Exchanger
Authors: Farsi H. , Azzouz K. , Leducq D. , Macchi H. , Guilpart J.
Published: December 2008

A global model simulating the behavior in steady-state of a refrigerating system using a small channel condenser, is presented in this paper. Its objective is to optimize the design of this system in term of improving its efficiency and minimizing the refrigerant charge, in order to reduce the greenhouse effect. We were interested mainly on the small channel condenser model in which heat exchange and pressure drop were calculated with laws adapted, when it is necessary, to the small channel configuration. The refrigerant charge contained in the condenser was determined from correlations giving the local void fraction. The numerical results were compared with the experimental ones obtained with a device conceived for this objective. This comparison has shown a good agreement. Then, the model was used as a design tool for an optimal refrigerating system with a minimum TEWI. The optimization mainly concerned the small channel condenser geometry. The results have shown an absence of limit to the channel diameter reduction, in term of TEWI: an increase in the total tube number makes it possible to limit the system pressure drop. Moreover, the global model permits to determine the optimum tube distribution for a configuration of a condenser with two passes: this optimum is about 80% in the first pass and 20% in the second one.
Condensation Heat Transfer Inside Multi-Port Minichannels
Authors: Cavallini A. , Del Col D. , Doretti L. , Matkovic M. , Rossetto L. , Zilio C.
Published: December 2008

In this paper the experimental heat transfer coefficients measured during condensation of R134a and R410A inside multiport minichannels are presented. The need for experimental research on condensation inside multiport minichannels comes from the wide use of those channels in automotive air-conditioners. The perspective for the adoption of similar channels in the residential air conditioning applications also calls for experimental research on new high pressure refrigerants, such as R410A. Heat transfer data are compared against models to show the accuracy of the models in the prediction of heat transfer coefficients inside minichannels.
An Experimental Study of Flow Condensation Heat Transfer Inside Circular and Rectangular Mini-Channels
Authors: Shin J. S. , Kim M. H.
Published: December 2008

By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels (Dh = 0.493, 0.691, and 1.067 mm) and rectangular channels (Dh = 0.494, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 kg/m2s, a heat flux of 5 to 20 kW/m2, and a saturation temperature of 40°C. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation were investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.
Condensation Pressure Drops in Circular Microchannels
Authors: Garimella Srinivas , Agarwal Akhil , Killion Jesse D.
Published: December 2008

This paper presents a multiple flow-regime model for pressure drop during condensation of refrigerant R134a in horizontal microchannels. Two-phase pressure drops were measured in five circular channels ranging in hydraulic diameter from 0.5 mm to 4.91 mm. For each tube under consideration, pressure drop measurements were first taken over the entire range of qualities from 100% vapor to 100% liquid for five different refrigerant mass fluxes between 150 kg/m2-s and 750 kg/m2-s. Results from previous work by the author on condensation flow mechanisms in microchannel geometries were used to assign the applicable flow regime to the data points. Pressure drop models for intermittent (Garimella et al. 2002) and annular (Garimella et al. 2003a) flow reported earlier by the authors were modified and combined to develop a comprehensive model that addresses the entire progression of the condensation process from the vapor phase to the liquid phase. This combined model accurately predicts condensation pressure drops in the annular, disperse wave, mist, discrete wave, and intermittent flow regimes. Overlap and transition regions between the respective regimes are also addressed using an appropriate interpolation technique that results in relatively smooth transitions between the predicted pressure drops. The resulting model predicts 82% of the data within ±20%.
Design of Micro Heat Spreaders for Electronic Cooling
Authors: Chiarot P. , Sullivan P. , Ben Mrad R.
Published: December 2008

This work presents an active Micro Heat Spreader (MHS) for use in electronic cooling. The device includes four reservoir chambers and is actuated using membrane deflection. An investigation is performed using Finite Element Analysis to determine the performance characteristics of the MHS. Two operating conditions for the actuation order of the membranes are considered. Dimensional similitude is used to obtain a single maximum temperature versus Reynolds number curve for the device at the given operating condition and Prandtl number. Fabrication of the MHS is proposed using the Silicon-on-Insulator (SOI) technique and actuation of the membranes can be achieved using thin film PZT.
Micro-Fluidic Flow Induced by High-Frequency AC Micro-Bubble Jets
Authors: Lastochkin Dmitri , Wang Ping , Chang Hsueh-Chia
Published: December 2008

A new mechanism for generating a micron-sized bubble jet in an electrolyte within a micro-fluidic device is reported. A three-dimensional electrode tip is placed at the center of a micro-channel. All but the electrode tip is insulated with a dielectric film. A counter insulated electrode sits across the tip electrode and a large high-frequency (> 100 kHz) and high intensity (>1000 V) AC field is applied across the electrodes. The large voltage generates micron-sized bubbles at the tip which snaps off intermittently or continuously to produce a micro-bubble jet by a unique tip streaming mechanism. The ejected bubbles continue to be driven by an electrostatic force in the tip direction and move at a velocity in excess of 10 cm/sec. They drag a large surrounding liquid column around them to move at the same velocity and hence generate a pumping action stronger than all reported electro-kinetic micro-pumps.
Study on the Mixing Performance Inside a Micromixer by Using Rapid-Prototyping Technology and Micro-LIF System
Authors: Heo Hyeung Seok , Suh Yong Kweon
Published: December 2008

In this study a newly fabricated micromixer is proposed. This design comprises periodically arranged simple blocks. In this configuration, the stirring is greatly enhanced at a certain parameter set. This device is fabricated by rapid prototyping technology, stereolithography method, so that we can reduce the R&D time and cost. To characterize the flow field and the stirring effect both the numerical and experimental methods were employed. To obtain the material deformation, three-dimensional numerical computation to the Navier Stokes equations are performed by using a commercial code, FLUENT 6.0. Numerical results show that materials are deformed by the counter clockwise spiral motion of the secondary flows. In the experiment, flow visualization for the stirring effect is performed by using pure water in one reservoir and water mixed with a fluorescent dye in the other, so that we can see the flow motion inside the microchannel. The numerical and experiment results show that the stirring is significantly enhanced at larger block-height. We assert that we can apply the rapid-prototyping technology in the micro fabrication.
Heterogeneous Surface Charge Enhanced Micro-Mixer for Electrokinetic Flows
Authors: Biddiss Elaine , Erickson David , Li Dongqing
Published: December 2008

Enhancing species mixing in microfluidic applications is key to reducing analysis time and increasing device portability. Mixing in electroosmotic flows is usually diffusion-dominated requiring extended channel lengths and retention times. Recent numerical studies have indicated that the introduction of electrically charged surface heterogeneities may augment mixing efficiencies by creating localized regions of flow circulation. In this study, we experimentally visualize the effects of surface charge patterning and develop an optimized electrokinetic micromixer applicable to the low Reynolds number regime. Using the optimized micro-mixer, mixing efficiencies were improved between 22% and 68% for applied potentials ranging from 70–555 V/cm when compared with the homogeneous case. For 95% mixture, this equates to a potential decrease in required mixing channel length of up to 88% for flows with Pe´clet numbers between 190 and 1500.
An Electrokinetically Controlled DNA Hybridization Chip
Authors: Erickson David , Liu Xuezhu , Krull Ulrich , Li Dongqing
Published: December 2008

Biosensors and more specifically biochips exploit the interactions between a target analyte and an immobilized biological recognition element to produce a measurable signal. Systems based on surface phase nucleic acid hybridization, such as modern microarrays, are particularly attractive due to the high degree of selectivity in the binding interactions. One drawback of this reaction is the relatively long time required for complete hybridization to occur, as a result of the diffusion limited reaction kinetics. In this work an electrokinetically controlled DNA hybridization microfluidic chip will be introduced. The electrokinetic delivery technique provides the ability to dispense controlled sample sizes to the hybridization array while serving to increase the mass transfer rate and therefore the reaction speed. The focus of this paper will be on the design and microfabrication of the chip, the unique H-type channel structure and electrokinetic sample delivery and washing technique, and development of the on-line hybridization scanning. Initial hybridization results presented here demonstrate that less than 5 minutes and 4.9nL of 0.5μM ssDNA sample was required (35s dispensing period followed by a 4 minute wash) for complete hybridization.
Finite Element Bounds to the Mass Flow Rate for Electro-Osmotic Flows in Two Space Dimensions
Authors: Choi Hae-Won , Paraschivoiu Marius
Published: December 2008

The micro pumping technology is one of the major and growing research fields in microfluidics. The use an electric voltage to induce electro-kinetic fluid flow is an efficient and reliable mechanism for micro pumping systems. The prediction of quantities such as the mass flow rate or the mean species concentration for this type of flow, termed the Electro-Osmotic flow, plays a crucial role in the design and control process of the entire microfluidic system. To this end, numerical techniques are efficient to evaluate these quantities but accuracy depends on the mesh utilizes. The a posteriori finite element output bound method is used to calculate these quantities while offering information regarding accuracy. The bound method applied here-in is based on the flux-free approach and provides relevant, inexpensive, and asymptotic lower and upper bounds to the mass flow rate of an Electro-Osmotic flow in a cross-intersection of a two-dimensional microchannel. To obtain shaper bounds, the flux-free approach is further enhanced by an adaptive mesh refinement strategy. This work focuses on the development of the numerical procedure for Electro-Osmotic flows and reports performance of the method in terms of numerical accuracy and computational cost.
Simulation of Electroosmotic Flows in Micro- and Nanochannels Using a Lattice Boltzmann Model
Authors: Tian Fuzhi , Li Baoming , Kwok Daniel Y.
Published: December 2008

A Lattice Boltzman Model (LBM) with the Poisson-Boltzmann equation for charge distribution is presented for the simulation of electroosmotic transport in straight rectangular micro and nanochannels. Our results from the LBM are in excellent agreement with the corresponding analytical solution. We have shown that the Lattice Boltzmann Model in the presence of an external force may be used an effective computational tool to simulate the electroosmotic transport phenomena in micro- and nanochannels.
Comparison of Numerical Simulation and Experimental Results for Crossflow and Counterflow Microchannel Heat Exchangers
Authors: Halbritter A. , Schygulla U. , Wenka A. , Schubert K.
Published: December 2008

At the Institute for Micro Process Engineering of the Forschungszentrum Karlsruhe, micro heat exchangers are manufactured out of single foils of base metal alloys. The characterisation of the thermohydraulic properties of microchannel heat exchangers is done using water as heat transfer medium on both passages at temperatures of 10°C and 95°C. The present publication will give an overview of the numerical simulation as well as experimental results for crossflow and counterflow microchannel heat exchangers. A comparison of three crossflow heat exchangers with different microchannel structures, and two different types of counterflow microchannel heat exchangers is shown. For comparison, the heat transfer rate, the overall heat transfer coefficients and efficiencies as well as pressure drop obtained from experiment and theory is shown. For numerical simulation, two models have been used. An easily accessibly method is to use classical engineering codes based on the Nusselt theory (VDI Wa¨rmeatlas, 1994). A more detailed model is to use computational fluid dynamics (CFD) with the commercially available tool FLUENT ®, where best estimation codes have been applied for numerical simulation. Both numerical calculations are a helpful complement to predict thermal and hydrodynamic behaviour of the microchannel heat exchangers.
Valve Automation for Oil Pipeline Safety
Authors: Mohitpour Mo. , Trefanenko Bill , Tolmasquim Sueli Tiomno , Kossatz Helmut
Published: December 2008

Most pipeline codes, do not stipulate any requirement for block valve spacing nor for remote pipeline valve operations along transmission pipelines carrying low vapor pressure petroleum products. This requirement is generally industry driven for their desire to proactively control hazards and mitigation of environmental impacts in the event of pipeline ruptures or failures causing hydrocarbon spills. This paper will highlight a summary of pipeline codes for valve spacing requirements and spill limitation in high consequence areas along with a criteria for an acceptable spill volume that could be caused by pipeline leak/full rupture. A technique for deciding economically and technically effective pipeline block valve automation for remote operation to reduce oil spill and thus control of hazards is also provided. The criteria for maximum permissible oil spill volume, is based on industry’s best practice. The application of the technique for deciding valve automation as applied to three initially selected pipelines (ORSUB, OSPAR and ORBEL) is discussed. These pipeline represent about 14% of the total (6,800 kilometers, varying between 6” to 42”) liquid petroleum transmission lines operated by Petobras Transporte S.A. (Transpetro) in Brazil. Results of the application of the technique is provided for two of the pipelines: OSPAR (117 Km, 30” line) and ORBEL II (358 Km 24” line), both carrying large volumes of crude oil.
Reliability Analysis of Land Pipelines for Hydrocarbons Transportation in Mexico
Authors: De Leon David , Cortes Carlos
Published: December 2008

Pipelines are the most economical way to transport hydrocarbons. In Mexico, PEMEX manages more than 60,000 Km of oil and gas land and marine pipelines. Therefore, their structural integrity must be carefully assessed. Pipeline managers require reliable and realistic codes in order to back up their decisions about design, maintenance and operation. In particular, for safety prediction, the failure modes and uncertainties involved in each loading condition need to be incorporated in the analysis in order to specify the pipelines use thresholds that keep them over acceptable safety levels within their operating lifetimes [1, 2]. For these reasons, a structural reliability formulation appears to be the appropriate framework to perform the evaluation. In this paper, the land pipeline reliability is estimated for the internal pressure, bending and tension failure mode conditions. These loading conditions are applied individually and tension and bending in a combined fashion, and random variability on the internal pressure, steel mechanical properties as well as the degradation effect of internal corrosion due to the transported fluid is included. So far, seamless pipeline is considered as used in Mexico. A set of internal pressures and mechanical properties are randomly generated through Monte Carlo simulation and the pipeline response under each simulated condition is obtained by making use of commercial software. The response analysis resorts on the nonlinear finite element method and it involves the calculation of maximum stresses and stress concentration factors under no corroded and corroded conditions. The following limit states are assessed: 1) the margin between maximum stresses due to internal pressure, tension and bending and the material capacity and 2) the margin between stress concentration factor and fracture initiation toughness. The above described limit states are calculated for no corroded condition and, once the critical failure modes are identified, corrosion effect is included on them. The failure probability is estimated from the response statistics for the considered limit state. The Cornell reliability index and the respective safety factor are also estimated. These results may be further extended and used for risk assessments and code calibration for design, inspection and maintenance of pipelines in Mexico.
Magnetic Properties of Pipeline Steels are Variable
Authors: Atherton David L. , Clapham Lynann
Published: December 2008

Magnetic or electromagnetic nondestructive inspection techniques for steel are ultimately limited by the fact that the magnetic properties of high strength steels used in pipelines vary considerably. Different samples of steels with similar mechanical specifications and properties can, and do, have very different magnetic properties. Furthermore large variations often occur over distances of as small as a few millimeters within a single sample depending on position, direction and conditions, particularly applied and residual stresses. Unfortunately these variations are typically most pronounced in high strength steels since these often have high residual stresses as a result of their having been heavily cold worked to enhance yield strength. Here we present examples illustrating the effects of some of these variations.
A 3-Dimensional Eulerian Finite Element Model for Ice Scour
Authors: Konuk Ibrahim , Gracie Robert
Published: December 2008

The main objective of this paper is to present a Finite Element (FE) numerical model of the ice scour process. The FE model is developed to study the soil deformation and transport process around the scouring ice and to investigate the effects of the ice scour on a pipeline buried or laid in a trench cut on the seabed. The focus of this paper is on the scours caused by ice ridges commonly observed in the Beaufort Sea. The developed FE model is a new application of the Arbitrary-Lagrangian-Eulerian (ALE) method to a soil mechanics problem involving very large deformations. Soil material, originally positioned in front of the ice ridge, is transported forward and sideways through the FE mesh and deposited in the berms formed on both sides of the scour. The soil material below the scour depth similarly moves across the mesh simulating the subscour effect. An inviscid CAP plasticity constitutive model is used to model the soil material. This paper focuses on the interaction between the ice ridge and the seabed. It describes soil transport process involved during the interaction. The soil deformation field obtained from the model is compared with the empirical deformation functions commonly used in current design methods. Future papers will report on the interaction between the ice ridge, the infill in the pipeline trench, and the pipeline; the influence of the soil properties of the trench and the seabed will also be studied.
An Experimental and Numerical Study of the Effect of Pre-Strain on the Fracture Toughness of Line Pipe Steel
Authors: Cosham Andrew , Hopkins Phil , Palmer Andrew
Published: December 2008

Oil and gas pipelines may be subject to high plastic strains, either intentionally as a result of the method of installation, or the requirements of the design and operation, or accidentally (due to mechanical damage), before they enter service (transportation, construction/installation, etc.) and during operation. Pre-strain is introduced by denting, cold bending, land slides, subsidence, frost heave, ice gouging, earthquake induced ground movement, reeling, installation in deep water, and wrinkling or buckling. Material subjected to pre-strain will have different material properties to that of the virgin material. Previous experimental studies have indicated that pre-strain 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. To investigate the effect of pre-strain on the fracture toughness of line pipe steel a programme of tests and numerical analyses has been undertaken. The results of tensile, notched tensile, fracture toughness (J-integral and CTOD) and Charpy V-notch impact tests of virgin (not pre-strained) material, prestrained material and artificially strain aged material are reported. It is shown that the effect of pre-strain can be simulated numerically using a finite element model incorporating the influence of material damage through a Gurson-Tvergaard constitutive model. The properties of the virgin material that influence the effect of pre-strain on toughness are discussed. The role of material damage (void nucleation and growth, etc.) during the introduction of pre-strain is shown to be less significant than the changes to the tensile properties and ductility caused by pre-strain. The effect of tensile pre-strain on 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, and several parameters that relate to the conditions for ductile fracture (or cleavage fracture). A simple, engineering approximation to the effect of pre-strain on fracture toughness for application to pipeline design and fitness-for-purpose assessment is proposed in terms of the true strain at the tensile strength of the virgin material.
Status of U.S. In-Line Inspection Standards
Authors: Brown Bryce , Culbertson David , Melan Bryan , Rau Jerry , Selig Bernie , Thetford Scott
Published: December 2008

The U.S. gas and liquid pipeline industry and its regulators have been working to improve pipeline safety and integrity through a pipeline integrity management effort since 1999. The Office of Pipeline Safety of the U.S. Department of Transportation issued integrity management regulations for liquid pipelines in 2001 and issued similar regulations for gas pipelines at the end of 2003. The Office of Pipeline Safety (OPS), also issued regulations for Operator Qualification in 1999 requiring personnel that perform certain tasks to be qualified to perform those tasks. The Integrity Management Programs require extensive inspections of pipelines and the primary method for these inspections is of course In-Line Inspection (ILI). These inspections are critical to the safety and integrity of pipelines and the requriements are reflected in ASME B31.8S Integrity Management for Gas Pipelines. However, neither the inspection systems nor the personnel operating the systems and analyzing and reducing the data have to be qualified under existing standards or regulations. Industry and the Regulators agreed to embark on the development of consensus standards that would address the qualifications of both the ILI Systems and the ILI Personnel that run the systems and evaluate the inspection data. This paper describes the 3 standards that have been developed to obtain “qualified” In-Line Inspection results: API 1163: In-Line Inspection Systems Qualification; ASNT ILI-PQ-2003: In-Line Inspection Personnel Qualification; NACE RP0102-2002: Standard Recommended Practice, In-Line Inspection of Pipelines. The interrelationship of the 3 standards and how to utilize them will be discussed. (See figure 1). The latest changes to the standards and their acceptance by industry will also be described.
Field Inspection Module for Hydrotechnical Hazards
Authors: Leir Mark , Reed Michael , Yaremko Eugene
Published: December 2008

Terasen Pipelines (Terasen) owns and operates an 1146 km low vapour pressure petroleum products pipeline between Edmonton, Alberta and Burnaby, British Columbia. Its right-of-way passes through some of the most geotechnically, hydrotechnically, and environmentally challenging terrain in Western Canada. This paper describes the latest advancement of a natural hazards and risk management database application that has supported a 6-year hazard management program to quantitatively assess and prioritize the geotechnical and hydrotechnical risk along the pipeline. This database was first reported at IPC 2002 in a paper entitled “Natural hazard database application — A tool for pipeline decision makers” [1]. This second paper describes the advancements since then, including the addition of the Hydrotechnical Field Inspection Module (FIM), an add-on tool that allows field inspection observations to adjust hazard and vulnerability. This paper discusses the challenges in building a methodology that is practical enough for field maintenance personnel to use yet sufficiently comprehensive to accurately describe improving or worsening hydrotechnical hazard conditions. Functionality to enter hazard inspection data, review inspection results in the office, and authorize changes to the hydrotechnical hazard probabilities are described in the paper and demonstrated in the conference presentation. The relationship between revised hazard, vulnerability, risk, and response thresholds (such as inspection frequency, monitoring, site surveys, or mitigation) are demonstrated using a river crossing with a dynamic hazard history. As in previous years, this paper is targeted to pipeline managers who are seeking a systematic hazard and risk management approach for their natural hazards.
Offshore Arctic Pipeline Oil Spill Risk Assessment
Authors: Comfort G. , Dinovitzer A. , Lazor R. , Hinnah D.
Published: December 2008

Renewed interest in offshore arctic oil and gas has led to the need for pipeline designs able to minimize environmental risk. A risk evaluation was conducted to assess the relative merits of pipeline concept designs for the Liberty Pipeline, which is intended to carry oil from BP/Amoco’s Liberty site to onshore Alaska. The Liberty site is inshore of the Barrier Islands in the Alaskan Beaufort Sea, in 22 feet of water. The offshore portion of the pipeline is 6.12 miles long. Risk was defined as the oil volume expected to be spilled over the 20-year life of the Liberty Pipeline. Risks due to ice gouging, strudel scour, permafrost thaw subsidence, thermal loads leading to upheaval buckling, corrosion, third party activities, and operational failures were evaluated. Failure probabilities were assessed based on analyses of the pipeline’s response and failure criteria that were established. A consequence model was set up to quantify the oil volume released during a pipeline failure, considering the mode and location of failure as well as leak detection systems. The risk was evaluated by summing the product of event probability and consequence for each hazard. The relative risk is discussed for each pipeline design.
Fuel-Efficient Operation of Compressor Stations Using Simulation-Based Optimization
Authors: Krishnaswami Prakash , Chapman Kirby S. , Abbaspour Mohammad
Published: December 2008

One of the primary concerns in the operation of a compressor station is minimization of fuel consumption while maintaining the desired throughput of natural gas. In practice, the station operator tries to achieve this by shutting down units or controlling individual unit speeds based on experience. This is generally a trial-and-error process without any guarantee of optimality. In this paper we present a robust structured solution process for tackling this problem using simulation-based optimization. The first step to develop this solution process is to devise an analysis scheme that provides the simulation support required by the optimization. This was achieved by developing a fully implicit finite difference formulation of the continuity, momentum and energy equations for flow under non-isothermal conditions. The performance of each compressor unit was modeled by fitting polynomials to the compressor map. These polynomial equations were appended to the flow equations to obtain a complete set of system governing equations. The nonlinear algebraic equations resulting from this formulation were then solved using a Newton-Raphson iteration to obtain system performance. The problem of optimizing the operation of a compressor station was then formulated as a nonlinear programming problem (NLP) in which the design variables are the compressor unit speeds and the objective function to be minimized is the fuel consumption. A constraint was also placed on the minimum mass flow rate through the station to ensure that adequate flow is maintained while minimizing fuel consumption. This NLP was then solved using a sequential unconstrained minimization technique (SUMT) with a derivative-free grid search for handling the unconstrained minimizations. The simulation algorithm mentioned earlier is invoked whenever the optimization needs to evaluate the system response at a candidate operating point. The results obtained show that the simulation works very well in terms of predicting system response, and the proposed simulation-based optimization approach is highly effective in minimizing fuel consumption in a systematic way. The approach is successfully applied to single stations as well as to a sequence of stations along a pipeline, thereby establishing its applicability to station-level and network-level optimization.
In Service Weld Xray Method for Thick Fittings on Large Diameter Licquid Filled Pipelines
Authors: Kolbuck Vince
Published: December 2008

Background: Enbridge Pipelines (Lakehead) was interested in a method to analyze longitudinal butt and fillet welds on pipeline repair sleeves and stopple tee fittings with the goal of finding weld defects such as inadequate root penetration, weld porosity, slag inclusions and other structural defects. Problem: Traditional pipeline x-ray techniques to not generate enough energy to overcome steel thicknesses up to 3.6 inches (91.4 mm) and the density of crude oil in a 34 inch (863.6 mm) diameter pipe. Attempts using cobalt 60 with up to 60 minute exposures did not produce x-rays with distinguishable features. Technology Comparison: Two methods were considered. One utilized an automated array of ultrasonic probes each specifically targeting regions within the longitudinal butt weld. This method was successfully developed for butt welds, however Enbridge chose to pursue using a high power XRay source called a Linear Accelerator (Linac) to look at butt and fillet welds. Linear Accelerator Technical Description: Derived from work done by the Electrical Power Research Institute (EPRI), the Linac unit has demonstrated that it can produce code quality in service inspections for power plant boilers, nuclear plant piping, pre-stressed concrete bridge sections and other applications. Its design has been adapted from the Los Alamos Science Research Center’s work with the atomic bomb program. This is the highest power portable x-ray source in the world with a total power of 6 million volts as compared with the 200,000 equivalent volts produced by a Cobalt 60 radiation source. Field Trial and Results: The test specimen was a 34 inch (863.6 mm) diameter stopple tee which had been removed from the pipeline system and filled with water. Hole type penetrameters were placed directly next to the long seam welds on the stopple tee to verify the image quality, X-Ray images were exposed in 13–15 seconds and consistently produced sensitivities of 2T on 25 & 30, which was well within code requirements for the material. This technology displayed weld defects including lack of root penetration, porosity and slag inclusion that could be interpreted to code standards. Summary: This field trial proved that the Linac could be used in actual conditions. The Linac unit would requires some minor modifications for pipeline application including special mounting brackets and other small adjustments. Public safety is also a concern with this high power source as public evacuation is required within a 250 foot (76.2 m) radius of the source. Enbridge did not undertake a larger program with this technology but demonstrated that it could be used successfully if required.
Experimental Studies of Pipeline Uplift Resistance in Frozen Ground
Authors: Liu Bill , Crooks Jack , Nixon J. F. (Derick) , Zhou Joe
Published: December 2008

A buried pipeline is subject to a variety of internal and external loads, one of which is the load induced by relative movements between the pipeline and the surrounding soils. Frost heave is one of the potential mechanisms that induce the relative movement for buried pipelines of chilled gas. The magnitude of the loads due to frost heave depends upon the amount of heaving and the load-displacement characteristics of the surrounding frozen soils, i.e., the uplift resistance of the frozen soils. Under the sponsorship of Pipeline Research Council International (PRCI), laboratory uplift tests have been carried out to study the load-displacement characteristics of a frozen soil and to assess the impact of loading rate, ice content and freezing direction. In addition to the measurements of the load and displacement of the pipe, deformations of the soil surface were also monitored at various locations. Parallel to the uplift tests, a series of laboratory geo-mechanical tests were conducted to define stiffness, tensile strain limits and time-dependent behavior of the frozen soil. Examples of the uplift test results are presented in the paper, together with detailed descriptions of soil material and test conditions. It is noted that quantitative data on uplift resistance are considered proprietary and will not be presented in this paper; however, detailed data may be obtained from technical publications of PRCI. Observations during the test with respect to the development of cracks in the frozen soil will be discussed. The load-displacement relationships measured in the uplift tests, together with the geo-mechanical properties of the frozen soil, will be used to the development and calibration of a numerical model, which will be presented in a separate technical paper to IPC2004.
Enhanced Lifetime for Internal Pressure Fatigue of DSAW Pipes
Authors: Reepmeyer Oskar , Liessem Andreas , Erdelen-Peppler Marion , Knauf Gerhard
Published: December 2008

Pipes are used as construction elements, to transport liquids and gas in pipelines and as storage containment’s for gas and liquids. A very cost efficient method to fabricate larger diameter pipes with heavier wall thickness is the DSAW process. In many applications in the above listed fields the pipes are exposed to fatigue loads. Several design codes and standards exist which consider SAW pipes for the different applications. Depending on the loading conditions the stress concentration resulting from the weld of the DSAW pipe but also from the connecting welds in the structure leads to a significant reduction in lifetime. This reduction is accounted in the different design codes. To utilize the cost efficient DSAW pipe also for applications which so far could economically only be served by seamless pipes a method was developed to reduce the stress concentration in the area of the long seam. This method provides pipes with a lifetime similar to a seamless pipe by still maintaining the competitiveness of the DSAW manufacturing process. A test program to qualify this method for Cargo Tank Cylinders for Compressed Natural Gas Transportation on vessels was accomplished in order to proof that the measures taken are effective.
The Benefits of Consensus Standards: A Pipeline Case Study
Authors: Boss Terry , Drake Andy , Leewis Keith , Selig Bernie , Zurcher John
Published: December 2008

The pipeline industry has implemented a process for acquiring data and information necessary to support technically-based standards and regulations through techical studies and research and development (R&D). This process enabled the development of ASME B31.8S based on the technical facts gathered, drawing upon all stakeholders including Federal and State regulators, pipeline operators, manufacturers and suppliers and members of the public. This paper describes the process being used by the gas pipeline industry to develop standards such as B31.8S and provides examples of the benefits derived from standards. It examines in detail the benefits that the pipeline industry and regulators derived from the timely development of ASME B31.8S - Integrity Management of Gas Pipelines and the process used to support the standards’ development. The Office of Pipeline Safety developed a cost/benefit analysis to support the final rule on Integrity Management in High Consequence Areas. The OPS analysis indicates that the net cost for the gas pipeline industry to implement this program is now $4.7 B over the next 20 years as compared with the proposed rule based on the Pipeline Safety Improvement Act of 2002 which they estimated to cost $10.9B over the same period. OPS has incorporated B31.8S into its regulations, which has significantly simplified them, yet through prescriptive requirements, has provided an equal or better level of safety as envisioned by Congress. While the timely development played a major role in the distillation of the regulations, B31.8S cannot take credit for the full $6.2B savings to the industry. The estimated savings provided by B31.8S to the industry will be described. Industry management and the regulators are encouraged to fully support the continuing development of standards for the pipeline industry utilizing the model developed by the gas pipeline industry.
Post-Installation Geotechnical Issues Associated With Large-Scale HDD Crossings
Authors: Baumgard Alex , Savigny K. Wayne , Cocciolo Peter
Published: December 2008

Horizontal Directional Drilling (HDD) is increasingly being used as a technique to install pipeline through challenging conditions. With this increased use, several post-installation geotechnical issues have, quite literally, surfaced, often many months or years following the original installation. These issues include sinkhole development around the entry/exit points for the HDD operations and settlement of the surface above the HDD bore path. Both can be attributed to two major factors, those involving unfavourable ground conditions and those involving problematic installation procedures. Several examples of each of these factors are described along with mitigation measures designed to prevent both sinkhole and settlement from occurring following HDD installation. Case histories from two large HDD crossings are subsequently presented which illustrate the potential magnitude of these issues and the steps that are often required for repair; the first from a crossing of the Fraser River outside of Vancouver, Canada, and the second from a crossing of a major river in north-central Argentina. In both of these cases, large sinkholes formed behind the HDD exit points, resulting in property damage and possibly threatening neighboring utilities. Site investigation and design techniques implemented to minimise the potential for sinkhole development and settlement are discussed, and several remediation options used in the cases histories are presented.
Study of the Sensitivity of the Guanabara Bay PE-3 Pipeline to Geometric Imperfections
Authors: Benjamin Adilson Carvalho , Correia Guerreiro Joa˜o Nisan , Silva Rita de Ca´ssia Carvalho , Dourado Loula Abimael Fernando
Published: December 2008

This paper describes the study performed to investigate the sensitivity of the Guanabara Bay PE-3 pipeline to geometric imperfections. The main results of several FE analyses are presented. It is concluded that the PE-3 zigzag pipeline is geometrically stable when submitted to the maximum pressure loading and maximum temperature loading established in the design. Also it is shown that the von Mises stresses calculated in the analyses were below the yield strength of the pipe material.
Quantifying the Severity of Mechanical Damage
Authors: Torres C. R. , Dean A. P.
Published: December 2008

Current industry standards used for incorporating in-line inspection (ILI) data in the quantification of mechanical damage defects are relatively narrow in scope. The primary reason for this is the industry standards evolved around ILI tool limitations that existed several years ago. In recent years, there have been new technological developments in areas such as ILI tool capacity, new applications of mathematical principles, and increases in the types of mechanical damage characteristics identified with ILI tools. It is the opinion of this paper’s authors that these new developments have created opportunities for better integrity decisions based on sound engineering principles, eventually leading to much broader industry standards as well as economic benefits for the pipeline industry. The primary purpose of this paper is to describe the results of a research and development project recently completed by Tuboscope Pipeline Services and the Battelle Institute, the objective of which was to develop an algorithm to quantify the severity of mechanical damage defects.