Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Microfiche copy available in Archives and Aero. / Vita. / Includes bibliographical references. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Suzanne Marie Burzyk. / B.S.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Vita. / Bibliography: leaves 73-77. / Ph.D.

In the oil and gas industry, statistical methods have been used for corrosion analysis for various asset systems such as pipelines, storage tanks, and so on. However, few industrial standards and guidelines provide comprehensive stepwise procedures for the usage of statistical approaches for corrosion analysis. For example, the UK HSE (2002) report "Guidelines for the use of statistics for analysis of sample inspection of corrosion" demonstrates how statistical methods can be used to evaluate corrosion samples, but the methods explained in the document are very basic and do not consider risk factors such as pressure, temperature, design, external factors and other factors for the analyses. Furthermore, often the industrial practice that uses linear approximation on localised corrosion such as pitting is considered inappropriate as pitting growth is not uniform. The aim of this research is to develop an approach that models the stochastic behaviour of localised corrosion and demonstrate how the influencing factors can be linked to the corrosion analyses, for predicting the remaining useful life of components in oil and gas plants. This research addresses a challenge in industry practice. Non-destructive testing (NDT) and inspection techniques have improved in recent years making more and more data available to asset operators. However, this means that these data need to be processed to extract meaningful information. Increasing computer power has enabled the use of statistics for such data processing. Statistical software such as R and OpenBUGS is available to users to explore new and pragmatic statistical methods (e.g. regression models and stochastic models) and fully use the available data in the field. In this thesis, we carry out extreme value analysis to determine maximum defect depth of an offshore conductor pipe and simulate the defect depth using geometric Brownian motion in Chapter 2. In Chapter 3, we introduce a Weibull density regression that is based on a gamma transformation proportional hazards model to analyse the corrosion data of piping deadlegs. The density regression model takes multiple influencing factors into account; this model can be used to extrapolate the corrosion density of inaccessible deadlegs with data available from other piping systems. In Chapter 4, we demonstrate how the corrosion prediction models in Chapters 2 and 3 could be used to predict the remaining useful life of these components. Chapter 1 sets the background to the techniques used, and Chapter 5 presents concluding remarks based on the application of the techniques.

A principal forma de transporte de petróleo e derivados, entre outras substâncias, são os dutos, e um dos processos críticos relacionados é a sua inspeção periódica, que é necessária e obrigatória, de alto custo devido à sua complexidade, e que na maioria das vezes são realizadas manualmente, em procedimentos demorados, pouco confiáveis e insalubres devido ao meio e aos riscos a que o trabalhador é exposto. Este trabalho tem o objetivo de testar diversas aplicações e situações de um sistema de inspeção de dutos robótico desenvolvido. O interesse de observação foi a praticidade e facilidade de montagem e desmontagem do equipamento sobre a tubulação, a agilidade dos graus de liberdade propostos para o sistema, a flexibilidade do equipamento para utilização de diferentes métodos de inspeção, a rapidez e confiabilidade dos resultados de inspeção por ultrassom para varredura de espessuras em busca de corrosão generalizada interna de uma tubulação e a capacidade de precisão e resolução desta inspeção por ultrassom. Para abordar estes pontos, foram realizados uma série de testes, inicialmente para verificação do bom funcionamento dos graus de liberdade do sistema, e posteriormente com métodos diferenciados de inspeção, como testes para medição geométrica externa de uma tubulação, testes com sistemas de ultrassom embarcado em laboratório e em campo com diferentes malhas de inspeção e com um ou múltiplos cabeçotes, e para diferentes tubulações e formatos de redução de espessuras de parede na tubulação. / The main way for transporting petroleum and substances alike is through ducts, and one of the most critic processes involved is the periodic inspection, wich is necessary and mandatory, with a high cost due to its complexity, and, in most cases, done manually in long time consuming procedures and with little reliability and high risk for the workers involved. This work is intended to test various situations of a robotic inspection system developed. The observation interest was the practicity and easiness of assembling and disassembling the equipment on the pipes, the agility of degrees of freedom proposed for the system, the flexibility of the equipment for the use in different methods of inspection, the quickness and reliability of the results by ultrasound for scanning different thicknesses of a duct in search of "generalized internal corrosion" and the level of precision and resolution of this ultrasound scan. To approach this topics, a series of test were conducted, at first to check if the degrees of freedom of the system were working as intended and afterwards with different methods of inspection, such as external geometric measurements of the pipes, tests with onboard ultrasound systems in lab and on the field with different inspection grades and with one or multiple ultrasound sensors, and for different kinds of pipes and thickness reduction shapes of the pipe's walls.

Subsea pipelines form an integral part of the infrastructure associated with offshore oil and gas developments. These pipelines fulfill a range of functions from linking extraction wells to other subsea infrastructure to transporting products onshore, or to a central processing facility. Ancillary pipelines may also be present for gas or water injection to the reservoir or transporting additives. Pipelines are typically installed directly onto the seabed and, in the absence of significant drivers to undertake burial operations, they may remain on the seabed for the remainder of their design life. This is typically the case for deepwater developments. Subsea pipelines are subjected to a wide range of load cases including, self weight, installation loads, thermal and pressure driven expansion and hydrodynamic loading. Design of pipeline systems to accommodate these load cases requires an understanding of pipe-soil interaction. This thesis reports the results of a research study investigating pipe-soil interaction on a clay seabed, as relevant to the design of subsea pipeline systems. This study has utilised numerical analysis techniques based on the finite difference code FLAC to investigate a range of problem definitions. These problem definitions include pipelines subject to both vertical loading (V) and combined vertical and horizontal (V-H) loading. Factors such as variation in interface conditions, large strain and large displacement effects, soil unit weight effects and variation in shear strength conditions were considered in these problem definitions. Reliability based analysis techniques have also been used to investigate both V and V-H loading problem definitions. The analyses and investigations undertaken as part of this study generally achieved the following; reproduction and validation of earlier research with additional interpretation, extension of problem definitions to deeper pipeline embedment depths and investigation of pipe-soil interaction problem definitions that have not previously been considered. Reliability based analysis techniques have also provided some interesting insights into the impact of soil shear strength variation as well as providing a fundamental link between safety factors and probability of failure. Application to design practice of this, and similar studies, has been considered as part of this thesis and potential areas for future research have also been suggested.

abstract: This work helps to explain the drag reduction mechanisms at low and moderate turbulent Reynolds numbers in pipe flows. Through direct numerical simulation, the effects of wall oscillations are observed on the turbulence in both the near wall and the bulk region. Analysis of the average Reynolds Stresses at various phases of the flow is provided along with probability density functions of the fluctuating components of velocity and vorticity. The flow is also visualized to observe, qualitatively, changes in the total and fluctuating field of velocity and vorticity. Linear Stochastic Estimation is used to create a conditional eddy (associated with stress production) in the flow and visualize the effects of transverse wall oscillations on hairpin growth, auto-generation and structure. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

In closed conduit water systems, being able to accurately measure flow is absolutely essential. For many meter designs, including electromagnetic induction meters (also known as magnetic flow meters), the greatest accuracy is achieved when the device is calibrated correctly. Optimal meter accuracy often depends on the flow conditions associated with the upstream geometry in the pipe system. Manufacturers typically give standards for the length of straight pipe required upstream of the meter. These standards vary, however, and do not address every possible configuration that may be installed upstream of the straight pipe requirement. An investigation on the effects of the length of straight pipe between a single 90° elbow and the upstream side of magnetic flow meters was completed in this research. Eleven 10-inch meters were chosen for testing. The procedure included a baseline test with more than forty diameters of straight pipe between the elbow and the meter. The accuracy of the meter was determined over a range of flow velocities typical for operation of this type and size of meter. Further tests were performed with the meter installed only three diameters downstream of the elbow. These tests constitute Phase I. In Phase II, four meters were tested with the upstream pipe length varying from a close-coupled installation to ten diameters of straight pipe between the elbow and the meter to observe variances in accuracy with distance from the elbow. The intent of the research was to show whether manufacturer accuracy specifications are achievable in actual application. It was determined that very few meters meet the manufacturer’s specification for accuracy even when installation requirements were met. Post-factory calibrations and minimization of velocity profile disruption through consideration of upstream geometry is recommended.

Energy dissipation problems are often encountered where pipelines discharge into open channels. Normal pipe flow velocities most often result in super-critical velocities in canals. These high velocities may cause scour, overtopping, and unstable flow in the channel. The principal objective of the study was to find an efficient and economical design of a stilling basin transition from pipe flow to open channels. Pertinent variables were selected and their effects determined by extensive experimentation. An efficient stilling basin was developed utilizing a short dissipator pipe on the wall opposite the inflow pipe. The optimum diameter, length, and differential elevation between center lines was determined.

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