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DURABILITY STUDY OF REJUVENATED RAP BINDERS / Undersökning av beständigheten hos föryngrat bitumenLay, An Na January 2022 (has links)
När priset på naturtillgångar ökar samt att industrier måste ställa om till en mer hållbar verksamhet innebär detta även en omställning för asfaltsindustrin. Ett sätt för att använda mer återvunnet material i asfaltsindustri är att använda bindemedlet från gammal asfaltsmassa (eng.: reclaimed asphalt pavement, RAP). Detta kan dock inte göras utan komplikationer och därför måste bindemedlet föryngras innan för att kompensera för faktorer så som hög styvhet, låg krakning och trötthetsförmåga samt dålig anti-åldring förmåga hos RAPen. I det här projektet har två olika typer av föryngringsmedel använts; ett växtoljebaserat och ett petroleumbaserat mjukbitumen. Detta för att se om det var möjligt att använda förnybart och återvunnet material i bindemedlet men fortfarande uppnå samma prestanda som konventionellt bindemedel. Två blandningar gjordes hjälp av de två olika föryngringsmedlen och RAPen och analyserades parallellt med ett referensmaterial. Analyserna delades upp i två kategorier: reologi och kemi. Analyserna som föll under reologikategorin var mjukpunkt- och penetrationsanalyser, samt analyser med en dynamisk skjuvning reometer (eng.: dynamic shear rheometer, DSR) och en böjbalksreometer (eng.: bending beam rheometer, BBR). Under kemikategorin fanns analysmetoderna tunnskiktskromatografi med flamjoniseringsdetektor (TLC-FID) och Fourier transform infraröd spektroskopi (FTIR). Resultaten påvisar att åldring påverkas mycket av vilket föryngringsmedel som används, vilket blev tydligt när den reologiska förmågan testades. De kemiska analyserna gav stort sett liknade resultat oberoende av bindemedel. Blandningen som innehöll RAP och mjukbitumen visade sig vara mer mottagligt för åldring jämfört med den andra blandningen som innehöll växtolja, trots att den blandningen innehåller längre halt av RAPen. Vidare visar resultaten att blandningar kan prestera likt referensmaterialet när det kommer till reologi. Från den kemiska aspekten, uppvisar alla bindemedelsmaterial liknande egenskaper. Därför kan slutsatsen att RAPen var återvunnen med framgång när växtolja och mjukbitumen användes. / In recent years there has been a lot of focus on reduction of carbon footprint and sustainable development. For the asphalt industries, a way of doing this is to use reclaimed asphalt pavement (RAP) binders. This cannot be done without any complications and therefore, the RAP binder is normally rejuvenated to compensate for its high stiffness, and other poor properties like susceptibility to low temperature cracking and fatigue damage. In this project, two different ways of using RAP binder are investigated: one vegetable oil-based rejuvenator and one soft bitumen. Using the rejuvenator and soft bitumen together with a RAP binder, two different blends were made and compared to a reference bitumen which is commonly used in Sweden. The blends were made in such a way that the penetration values were close to the reference sample. Aging tests were performed by RTFOT and PAV. The testing of the non-aged and aged binder materials was divided into two sections: rheology and chemistry. The rheology testing included softening point, needle penetration, analysis with dynamic shear rheometer (DSR) and bending beam rheometer (BBR) whereas the chemistry testing included thin layer chromatography with flame ionization detector (TLC-FID) and Fourier transform infrared spectroscopy (FTIR). The results indicated that the ageing resistance of the binder materials is affected by the type of rejuvenator used which especially affects the rheological performance. The chemical performance was almost the same in each blend. The blend containing RAP binder and soft bitumen was more susceptible to ageing compared to the other blend containing oil-based rejuvenator even though the blend contained less of the RAP binder. The results also shows that the blends can perform equal to the reference sample for a rheological point of view. From a chemical point of view, the binders, including the reference, have the same properties. Therefore, the RAP binder was successfully recycled using both a bio-oil rejuvenator and soft bitumen.
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Etude du potentiel d'emploi des bitumes naturels dans la production des liants bitumineux durs et des enrobés à module élevé / The potential of natural bitumens in the production of hard bituminous binder and of high modulus asphalt concretesThemeli, Andrea 03 July 2015 (has links)
Le but de ce travail est d’étudier le potentiel d’un bitume naturel (BN) extrait en Albanie pour la production des bitumes durs (BD) et des enrobés à module élevé (EME). Pour la production des BD, différentes techniques de raffinage du pétrole existent. Néanmoins, avec certains bruts pétroliers il est impossible de les fabriquer. De plus, les BD de raffinerie comportent souvent des défauts qui limitent leurs applications. Ces raisons, couplées à des questions d’approvisionnement, conduisent à chercher des méthodes de substitution. Dans ce contexte, il est intéressant d’utiliser des BN. Cette étude a montré que le BN d’Albanie donne des BD et des EME en conformité avec la Normalisation Européenne, résistants au vieillissement et performants aux basses températures. Un dosage adéquat permet de formuler des matériaux d’une dureté désirée en réponse des exigences techniques des applications routières visées tout en facilitant la gestion des stocks de bitumes dans les centrales d’enrobages. / The aim of this thesis is to study the potential of a natural bitumen (NB) mined in Albania in the production of hard bitumens (HB) and that of high modulus asphalt concrete (HMAC). Various petroleum refining techniques are available for the production of HB. Nevertheless, this is impossible with some crude oils. In addition, HB from refineries often present shortcomings which limit their applications. These reasons, coupled with practical issues related to HB supply, motivate the research of alternative methods. In this industrial context it is interesting to use NB. This study has shown that the Albanian NB provides HB and HMAC in accordance with European Standards, resistant to aging and relatively performant at low temperatures. The proper dosage of this NB allows the formulation of materials of desired properties, in response to the technical requirements of the considered road applications, facilitating in this way the use of bitumen stocks in asphalt concrete production plants.
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Formulation de bitumes aux propriétés rhéologiques modulables / Bitumen with tunable rheological propertiesMerce, Manuel 14 December 2015 (has links)
La construction des routes avec des techniques d'enrobage à chaud (T=160 °C) implique une consommation d'énergie fossile et des rejets de gaz à effet de serre importants. Une production plus écologique du bitume nécessite de diminuer les températures d'enrobage en conservant les propriétés mécaniques des enrobés ainsi obtenus. Le développement de techniques permettant de réduire les températures est donc un enjeu majeur de l'industrie routière. Dans ce travail, nous avons joué à la fois sur la composition et le procédé pour moduler les propriétés du bitume et atteindre l’objectif fixé.Nous avons décomposé le bitume en ses différentes fractions en utilisant des techniques de séparation asphaltènes/maltènes à l'aide d'un alcane (pentane et heptane). Nous avons formulé des bitumes à différentes proportions et natures d'asphaltènes en introduisant des protocoles de préparation originaux. A l’aide de techniques de caractérisation variées telles que la rhéologie, la diffusion des rayons X ou encore des techniques de microscopies et d'analyses thermiques, nous avons déterminéles rôles des différentes fractions du bitume. Nous avons ainsi montré l'impact important des asphaltènes, mais également des fractions que nous avons qualifiées « d'intermédiaires », sur les comportements rhéologiques. Enfin, nous avons élaboré des objets coeur-écorce, composés d’une écorce rigide, non collante, riche en asphaltènes et d’un coeur mou, riche en maltènes. Ces objets sont particulièrement intéressants pour le transport du bitume à température ambiante. / The classic manufacture of hot mix asphalt for road construction is associated with a high consumption of fossil fuels and a high level of emissions of greenhouse gases into the atmosphere. A cleaner production of bitumen requires lowering the manufacturing temperature of these products without impoverishing their level of mechanical performances. The development of technologies that enable temperature reduction had thus become a major objective in the field of road engineering. In this work, we are playing on both composition and process in order to control the final properties of the material and propose an interesting way to reduce temperature during transportation. We have been interested in the different fractions composing the bitumen. We have there by employed a separation technique with alkane (heptane and pentane) to segregate the maltenes and asphaltenes. We could therefore realize diverse reconstituted bitumen using original protocols. Using various characterization techniques (such as rheology, X-ray scattering, optic, electronic and atomic force microscopy, infrared spectroscopy, thermal analysis...), we get insight into the effect of asphaltenes content and nature on bitumen properties. Our results show the huge impact of asphaltenes and other fractions called "intermediate fractions" on bitumen rheological properties. Finally, we propose an innovative processing of bitumen via the elaboration of core/shell objects composed of a rigid, nonsticky and asphaltenes-rich corona and a soft maltenes-rich core. These objects are very interesting for transporting bitumen at ambient temperature.
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Mineralogía y química del bitumen en depósitos estratoligados de cobre en la franja cretácica inferior entre los 27° y los 33° latitud sur, ChileVilches López, Lesly Marion January 2018 (has links)
Geóloga / Estudios en yacimientos estratoligados de cobre en el centro-norte de Chile reconocen la ocurrencia de materia orgánica, descrita como bitumen o pirobitumen. Éste se encuentra asociado a sulfuros de mena y ganga y suele estar diseminado o en fracturas. Las relaciones texturales en la mayoría de los depósitos indican que los sulfuros son posteriores al bitumen, pero no aclaran si este es un componente esencial y activo en la formación de la mineralización de cobre, considerando su rol como secundario.
Este trabajo propone caracterizar el bitumen presente en yacimientos estratoligados de cobre para constreñir como éste se relaciona con los procesos de mineralización de cobre (y plata subordinada)minerales en este tipo de depósitos, y aportar nuevos antecedentes acerca de su génesis. Para ello se realizó un estudio comparativo en tres depósitos estratoligados de Cu (Ag), alojados en la franja cretácica, del centro-norte de Chile: El Soldado, localizado en la V Región de Valparaíso, y los depósitos de La Culebra y Mantos Cobrizos, situados en la III Región de Atacama. Para cada uno de ellos, se realizaron estudios petrográficos de detalle y análisis composicionales semicuantitativos de bitumen mediante microscopía electrónico de barrido (SEM-EDS).
En términos generales, los depósitos estudiados presentan dos etapas de mineralización. La primera, de carácter hipógeno, está relacionada espacialmente al bitumen y a la formación de sulfuros de cobre. La segunda etapa se caracteriza por mineralización supérgena desarrollada de manera limitada, y representada por covelina, escasa digenita, hematita y óxidos de cobre.
En todos los depósitos estudiados se distingue más de un evento de introducción del bitumen. En general, éstos son previos a la mineralización de cobre, pero existen casos donde se asocia a una primera generación de mineralización de cobre, representada por bornita. La mineralogía de ganga (clorita, calcita, cuarzo, zeolita, prehnita, epidota), revela que el bitumen se emplaza en un contexto de temperaturas crecientes, con diversos episodios de alteración hidrotermal, algunos de ellos difíciles de distinguir del metamorfismo de bajo grado que caracteriza las rocas de caja. Se observan dos variedades texturales de bitumen, caracterizados en este estudio como bitumen liso y bitumen poroso. El primero suele estar enriquecido en Ca, Cl y S, comparado con el segundo. Además, se observa que independientemente de su variedad textural, el bitumen asociado a la mineralización de sulfuros de cobre está enriquecido en Fe, Cu, Cl y S. Además, presenta texturas de intercrecimiento con minerales de ganga, indicando que el bitumen interactuó con fluidos acuosos y en algún punto, previo a su solidificación, incorporó elementos desde éstos.
Los resultados de este estudio indican que el rol principal del bitumen en los yacimientos estratoligados de cobre del centro-norte de Chile es actuar como agente reductor, fomentando la precipitación de sulfuros de cobre y contribuyendo así a la formación de los depósitos. Sin embargo, y de acuerdo con la composición inferida del bitumen, la cual incluye complejos hetero-aromáticos y cantidades apreciables de metales y ligantes, no se descarta el rol de éste como agente de transporte, sugiriéndose así un rol activo, aunque secundario, en la formación de estos depósitos. / Este trabajo a sido financiado por Núcleo Milenio "Trazadores de Metales en Zonas de Subducción" NC130065
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The development of improved road tar binders from indigenous coal tars and aspects of their useJamieson, Ian Laurence January 1977 (has links)
Thesis (Ph.D. (Engineering))--University of the Witwatersrand, Engineering Faculty (Civil Engineering), 1977 / The thesis deals with the development of improved road tarbinders in
South Africa and their application in surface treatments and in mixes
used for pavement wearing courses and base courses in this country.
This work is timely in view of the country's current economic problems.
Locally produced tarbinders are considerably less expensive than bitumen
binders in inland areas; tar being produced in the Witwatersrand
complex whereas locally refined bitumen is produced from imported crude
oil. The annual expenditure on bitumen by the South African road industry
is currently of the order of R26 000 0 0 0. However, previously it had
been found that tarbinders were less durable than bitumen. [Abbreviated Abstract. Open document to view full version] / WS2017
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Surface Modification and In-process Steam Cleaning of Ceramic Membranes Used In the Treatment of Wastewaters Containing Bituminous FinesAtallah, Charbel 29 October 2019 (has links)
Synthetic membranes have a high separation efficiency, small footprint, low energy consumption and ease of operation, making them an attractive alternative to traditional separation operations. For this reason, membranes have been extensively studied for the treatment and recycling of bitumen-containing wastewaters. Such wastewaters include petroleum produced water, residual pipeline cleaning solutions and contaminated water from oil spills. Ceramic membranes are preferred in these applications over polymeric membranes because they are highly resistant to solvents and can be operated at high temperatures over a wide range of pH. Fine clays and silicates, coated with bitumen, are significant foulants for membrane filtration systems. These foulants possess acidic, basic and amphoteric groups, leading to the presence of both positive and negative surface charges. Ceramic membranes in aqueous media have a pH dependent surface charge. It was hypothesized that these surface charges are responsible for the high fouling of ceramic membranes that is observed when treating wastewaters containing bituminous fines.
The overall objective of this research was to reduce fouling and increase the lifetime of ceramic membranes in treating oil sands produced water; an example of a wastewater containing bituminous fines. This goal was achieved through the surface modification of the ceramic membrane’s selective layer, as well as by the implementation of a novel in-place steam regeneration technique. All membrane filtration tests were performed with field samples of oil sands produced water that were supplied to CanmetMINING (NRCan) by three Canadian oil sands companies.
Organosilanes are silicon-based monomers that can possess a wide array of chemical functionality due to their organic moieties. They are capable of reacting with oxide surfaces, and have seen extensive use as surface modification agents for ceramic membranes in various applications. To maintain desirable hydrophilic properties without surface charges, highly hydrophilic and non-ionic polyethylene oxide (PEO) based organosilanes were identified. These PEO-silanes were then used to modify ceramic membranes of several different selective layer materials, and the thermal stability of the silane layer was studied using FTIR, SEM, zeta potential and contact angle measurements. The modification procedure with PEO-silanes was first applied to lab-scale membrane disks, and subsequently to commercial scale multilumen membrane tubes that were tested in a pilot-scale system at CanmetMINING. Results obtained from both sets of experiments were promising and demonstrate that ceramic membranes can be surface modified in a way that successfully renders them fouling resistant to the bituminous fines present in these wastewaters. Upon surface modification, foulants were more readily released from the membrane surface, resulting in an enhanced flux and separation performance.
A novel steam regeneration technique was also applied as a means of bituminous fouling alleviation. This technique was tested in the CanmetMINING pilot-scale system and consisted of periodically injecting steam into the membrane lumen feed channels during operation. Direct steam injection rapidly heated foulant cake layers, and water droplets in the saturated steam caused surface abrasions that ultimately resulted in the scouring of bitumen away from the membrane surface. Membrane fluxes when steam regeneration was active were up to 4 times higher when compared to tests where only traditional permeate backflushing was used.
The fouling remediation techniques developed in this work have broad potential applicability in ceramic membrane filtration systems aimed at treating all wastewaters containing bituminous compounds, such as process waters in general and contaminated water from oil spills.
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Assessment of hyperspectral features and damage modeling in bitumen flotation processBhushan, Vivek 06 1900 (has links)
Flotation process is mineral processing technique used for separating valuable minerals from the gangue. The research presented in this thesis deals with assessing features that can help in measuring the performance (observing) bitumen flotation process and modeling damage in flotation units.
A timely measure of oilsands and process stream contents can be used to observe and control the separation performance. To this end, flotation experiments were conducted and hyperspectral images of the ore and the process stream were taken to determine whether spectral information can predict the bitumen and fines content of ore samples and establish relationship a between these variables and the froth colour. Several features that appear to correspond to clay and quartz were present.
Flotation cells are prone to wear damage by particles entrained in the slurry. A wear damage model was developed to predict the damage accumulated over a period of time. Particle image velocimetry experiments were conducted on physical flotation model to understand the flow behavior of the solid particles near the wall of the flotation unit. A preliminary wear test was conducted for qualitative assessment of wear. Recommendations were made for validating the damage model. / Engineering Management
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Effects of a Non-Condensable Gas on the Vapex ProcessFriedrich, Karen January 2005 (has links)
It is estimated that Canada has 1. 7 trillion barrels of oil contained in oil sands located mainly in Alberta. However, the oil contained in the oil sands is a very viscous, tar-like substance that does not flow on its own and cannot be produced with conventional methods. Economical production of this vast resource requires new technology and research. Research in Canada has helped maintain leadership in heavy oil recovery technology. <br /><br /> One method of viscosity reduction is through dilution, which is controlled by two mechanisms—mass transfer and gravity drainage. In the vapour extraction (Vapex) process, vapour of a light hydrocarbon solvent is injected into the reservoir. The mass transfer of vapour into bitumen is driven by a concentration gradient; the vapour diffuses into the heavy oil, causing a reduction in viscosity. The viscosity reduced oil is referred to as "live oil" and is now able to flow by gravity to a horizontal production well. At the surface, solvent can be easily separated and recovered from the produced oil through a flash separation/distillation process. <br /><br /> Under reservoir conditions, extraction solvents such as butane and pentane would condense, increasing the amount of solvent required and decreasing the density difference between solvent and bitumen. The solvent can be maintained in a gaseous phase, by co-injecting a non-condensable gas (NCG), reducing the partial pressure of the solvent and thus preventing condensation. Two types of models were used to observe the VAPEX process while varying the concentration of air and pentane in the system. Experimental results will help to determine the effect of increasing NCG concentration on the rate of live oil production. <br /><br /> The apparatus consists of a porous media model saturated with bitumen and placed inside acrylic housing. NCG (air) exists in the housing before liquid pentane is added. Pentane vapour continuously evolves from a reservoir of liquid pentane, maintained at constant temperature. A concentration gradient was established allowing pentane to flow into the system where the partial pressure of pentane in the bitumen phase is lower than the vapour pressure of pentane. The bitumen, diluted at the bitumen-gas interface, drains under the action of gravity. The advancement of the bitumen-gas interface was monitored to determine the live oil production rate. By varying the temperature of liquid pentane, the partial pressure of pentane in the extraction vessel was varied. <br /><br /> Results from five experiments in trough models and two in micromodels show that the rate of interface advancement in the presence of a NCG is proportional to the square root of time. Similarly, cumulative volume of oil produced was proportional to the square root of time. Previous works [Ramakrishnan (2003), James (2003), Oduntan, (2001)] have shown that interface advancement and production using a pure solvent was proportional to time. In the experimental range examined (24-32°C) temperature did not effect the rate of production for a given time or interface location. <br /><br /> The average steady state effective diffusion coefficient was calculated from production data to be 0. 116 cm<sup>2</sup>/s, five times larger than estimated from the Hirschfelder Equation. <br /><br /> Live oil properties were found to be consistent throughout each experiment and between experiments. On average, live oil contained 46-48 wt% pentane and viscosity was reduced by four orders of magnitude from 23,000 mPa?s to 4-6 mPa?s.
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Effects of a Non-Condensable Gas on the Vapex ProcessFriedrich, Karen January 2005 (has links)
It is estimated that Canada has 1. 7 trillion barrels of oil contained in oil sands located mainly in Alberta. However, the oil contained in the oil sands is a very viscous, tar-like substance that does not flow on its own and cannot be produced with conventional methods. Economical production of this vast resource requires new technology and research. Research in Canada has helped maintain leadership in heavy oil recovery technology. <br /><br /> One method of viscosity reduction is through dilution, which is controlled by two mechanisms—mass transfer and gravity drainage. In the vapour extraction (Vapex) process, vapour of a light hydrocarbon solvent is injected into the reservoir. The mass transfer of vapour into bitumen is driven by a concentration gradient; the vapour diffuses into the heavy oil, causing a reduction in viscosity. The viscosity reduced oil is referred to as "live oil" and is now able to flow by gravity to a horizontal production well. At the surface, solvent can be easily separated and recovered from the produced oil through a flash separation/distillation process. <br /><br /> Under reservoir conditions, extraction solvents such as butane and pentane would condense, increasing the amount of solvent required and decreasing the density difference between solvent and bitumen. The solvent can be maintained in a gaseous phase, by co-injecting a non-condensable gas (NCG), reducing the partial pressure of the solvent and thus preventing condensation. Two types of models were used to observe the VAPEX process while varying the concentration of air and pentane in the system. Experimental results will help to determine the effect of increasing NCG concentration on the rate of live oil production. <br /><br /> The apparatus consists of a porous media model saturated with bitumen and placed inside acrylic housing. NCG (air) exists in the housing before liquid pentane is added. Pentane vapour continuously evolves from a reservoir of liquid pentane, maintained at constant temperature. A concentration gradient was established allowing pentane to flow into the system where the partial pressure of pentane in the bitumen phase is lower than the vapour pressure of pentane. The bitumen, diluted at the bitumen-gas interface, drains under the action of gravity. The advancement of the bitumen-gas interface was monitored to determine the live oil production rate. By varying the temperature of liquid pentane, the partial pressure of pentane in the extraction vessel was varied. <br /><br /> Results from five experiments in trough models and two in micromodels show that the rate of interface advancement in the presence of a NCG is proportional to the square root of time. Similarly, cumulative volume of oil produced was proportional to the square root of time. Previous works [Ramakrishnan (2003), James (2003), Oduntan, (2001)] have shown that interface advancement and production using a pure solvent was proportional to time. In the experimental range examined (24-32°C) temperature did not effect the rate of production for a given time or interface location. <br /><br /> The average steady state effective diffusion coefficient was calculated from production data to be 0. 116 cm<sup>2</sup>/s, five times larger than estimated from the Hirschfelder Equation. <br /><br /> Live oil properties were found to be consistent throughout each experiment and between experiments. On average, live oil contained 46-48 wt% pentane and viscosity was reduced by four orders of magnitude from 23,000 mPa?s to 4-6 mPa?s.
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Improvement on Guided Wave Inspection in Complex Piping Geometries by Wavelet Transform AnalysisLee, Ping-Hung 20 August 2010 (has links)
The safety of pipelines distributed in the infrastructure of many industries has become very important since the industrial revolution. The guided ultrasonic wave technique can provide the possibility for rapid screening in long pipelines with corrosion. Especially the torsional mode T(0,1) of guided waves has been used in the cases of the pipe in the hidden region substantially. The ability of evaluating the inaccessible areas of the pipe makes the guided ultrasonic wave technique sit high on the roster of non-destructive testing tool for pipe inspection. However, the problem arises when attempting to detect the corrosions at the welded support bracket or under the bitumen coating on the pipe. The signal reflected from the corrosion will be covered by a large signal induced by the welded support or attenuated by the bitumen coating seriously. Therefore, the effects of welded support and bitumen coating on the T(0,1) mode are investigated by the experimental and the simulative methods. The continuous wavelet transform analysis is the signal processing method to extract the hidden signal of corrosion in this dissertation. There are five test pipes in the experiments. The response of the normal welded support is studied on the #1 test pipe. The #2 test pipe is used for attenuation investigation. The reflected signals of the features on the #3, #4, and #5 test pipes are measured and processed by continuous wavelet transform during defect detection process. In addition, the linear hexahedron elements are used to build the finite element models of the 6-inch steel pipe with support bracket and the pipe with bitumen coating. It is found that the effects of support bracket on the reflection comprise mode conversion, delayed appearance, trailing echoes, and frequency dependent behavior. When the T(0,1) mode impinges on to the support bracket, it will convert into the A0 mode inside the support due to the circumferential disturbance on the pipe surface. The reflection of the support bracket is identified as three parts formed by the direct echo, delayed echo and the trailing echo. The constructive interference of the A0 mode reflecting from the boundaries inside the support causes that the reflection spectrum shows two maxima peak at around 20-22 kHz (frequency regime of 0.0) and 32-34 kHz (frequency regime of 4.0) from both the experimental and simulated results. For the bitumen coating, the data collected from the welds and defects under the bitumen coating on the #2 test pipe show the attenuation effect on guided wave propagation and the difficulty of minor corrosion detection. In the finite element model of coated pipe, the results of predicted attenuation curves of T(0,1) mode indicate that the attenuation effect on guided wave propagation is aggravated with the increased value of the thickness, density or damping factor of the coated layer. Especially, in the case of 5-mm, the predicted attenuation curve shows a maximum point. Before this point, the attenuation increases with the operating frequency. For long range pipe inspection, it is the best way to avoid choosing the operating frequency around the corresponding frequency of the point. The measured data of corrosion affected by the welded support or the coated bitumen layer was processed by continuous wavelet transform to form a time-frequency analysis. The corrosion signals were identified in the contour map of the wavelet coefficient successfully. The understanding of the guided wave propagation on the pipe welded with support or pipe coated with bitumen is helpful to interpret the reflected signals. The use of continuous wavelet transform on signal processing techniques can improve the ability of defect detection on pipe with complex geometries.
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