This thesis is focused on the application of cross-correlation technique for leak detection and location in medium density polyethylene (MDPE) pipes. A leaking water pipe generates noise that depends primarily on water pressure, pipe characteristics and the leak size and shape. This noise, commonly called leak signals, can be used for the purpose of leak detection and leak location in MDPE pipes. A correlation technique is typically employed to detect, position and characterise these water leaks and is proved to be very efficient for metallic pipes. However, the same is not true for MDPE pipes where the attenuation rate with distance of the leak/source signal is very high, and the generated leak signals are of low frequency and narrow bandwidth. In order to locate leak with good accuracy in MDPE pipes, the correlation process relies on the estimation of speed of leak signals in water/pipe and the time delay between leak signals measured at two locations. For time delay estimation, a correlation function is used. Its accuracy depends upon the sharpness of the correlation peak, type and positioning of sensor, and the processing of signals obtained, which in turn further depends upon the characteristics of leak signals. In MDPE pipes, leak signals are of low frequency and narrow bandwidth; however, their frequency response is not well characterised. Therefore, this thesis presents an analytical model to explain the acoustic characteristics of leak signals in MDPE pipes. The model is used to study the effects of the cut-off frequencies of low, high and band pass digital filters and the selection of acoustic/vibration sensors for the correlation technique. It detailed the importance of the cut-off frequency of the high pass filter and the insensitivity of the correlation function to the cut off frequency of the low pass filter.

A ocorrência de elevados índices de perdas por vazamentos em sistemas de abastecimento de água é frequentemente ligada às inúmeras quebras de tubulações originadas em decorrência de elevados níveis de pressão atuantes. O controle efetivo de tais perdas requer a detecção e localização dos vazamentos para uma rápida reparação do sistema. Neste sentido, a consideração de análises hidráulicas no escoamento transitório tem se revelado especialmente útil aos propósitos de calibração e detecção de vazamentos. Tal análise pode revelar substancial quantidade de informações sobre as propriedades físicas e o nível de integridade do sistema, pois as ondas de pressão resultantes são afetadas pelos diversos dispositivos e fenômenos, incluindo os vazamentos. Assim, o presente trabalho visa o estudo dos transitórios hidráulicos para a calibração e detecção de vazamentos em modelos de sistemas de distribuição de água. Para tanto, são utilizados dados de redes hipotéticas e de laboratório, e modelos inversos resolvidos por métodos de busca global e local. Devido o emprego de tubos plásticos no circuito de laboratório, o clássico modelo da coluna elástica demonstrou-se ineficiente na reprodução do comportamento hidráulico de tal sistema. Resultados satisfatórios foram obtidos somente com um modelo hidráulico que considere o comportamento viscoelástico dos materiais dos tubos do circuito experimental. / The occurrence of large leakage losses in water supply systems has been frequently linked with pipe breaks resulting from high pressures levels in pipes. Efficient location of leakages is required in order to effectively control water losses and quickly repair the system. Analysis of hydraulic transients has been particularly useful for calibration and leak detection purposes. System observation for such analysis can reveal a substantial amount of information concerning physical properties and the integrity of the system, since water hammer waves are affected by different features and phenomena, including leaks. Thus, this research focuses on hydraulic transients for leak detection and calibration of water distribution system models. These objectives are achieved using data obtained from experiments performed on an experimental facility and numerical experiments on hypothetical networks. Inverse methods were based on both global and local search methods. Classic water hammer theory proved to be imprecise in describing the observed behavior of the hydraulic system composed of plastic pipes. Satisfactorily results were obtained with a hydraulic transient solver considering viscoelastic behavior of the pipe material.

O presente trabalho tem como objetivo principal o desenvolvimento de um sistema de identificação do surgimento de vazamentos (rupturas) em dutos, através da análise do sinal de sensores de pressão de resposta rápida (frequência de corte superior a 1 kHz). O reconhecimento do sinal de vazamento se realiza através de uma rede neural artificial feed-foward do tipo Perceptron Multi Camadas, previamente treinada. Neste trabalho, a implementação para tal operação foi feita off-line, mas devido ao baixo custo computacional pode ser facilmente implementada em eletrônica embarcada, em tempo real (on-line). Os resultados experimentais foram obtidos no oleoduto piloto do NETeF - Núcleo de Engenharia Térmica e Fluidos da USP - Universidade de São Paulo, com uma seção de testes com 1500 metros e diâmetro de 51,2 mm. Especificamente, os resultados foram obtidos com escoamento monofásico de água. Os resultados mostram-se promissores, visto que o sistema de redes neurais artificiais foi capaz de discriminar 2 universos linearmente separáveis, para sinais de vazamento e de não vazamento, para diversas vazões e localizações de vazamentos simulados. / The present dissertation deals with the development of a system to identify abrupt leaks (ruptures) in pipelines, by analyzing the signal of fast response pressure sensors (cutoff frequency over then 1kHz). The recognition of the leak signal is established by an artificial neural network feed-forward Perceptron Multi Layer, previously trained. In the present work the implementation was performed off-line, but due to low computational costs, the neural network can be easily implemented in real time embedded electronics (online). The experimental results were obtained in a 1500 meter-long and 51.2 millimeter-diameter pilot pipeline at the Center of Thermal Engineering and Fluids. Specifically, the results were obtained with single-phase flow of water. The results have proven to be promising, as the trained neural network was capable of classifying the 2 types of signals into 2 linearly separable regions, for leakage signals and no leakage signals, for various flow rates and locations of simulated leaks.

Soft robots and particularly inflatable robots are of interest because they are lightweight, compact, robust to impact, and can interact with humans and their environment relatively safely compared to rigid and heavy traditional robots. Improved safety is due to their low mass that results in low-energy collisions and their compliant, soft construction. Inflatable robots (which are a type of soft robot) are also robust to impact and have a high torque to weight ratio. As a result inflatable robots may be used for many applications such as space exploration, search and rescue, and human-robot interaction. One of the potential problems with inflatable or pneumatically actuated robots is air leaking from the structural or actuation chambers. In this thesis methods are demonstrated to detect leaks in the structural and actuation chambers of inflatable and pneumatically actuated robots. It is then demonstrated that leaks can be slowed by lowering a target pressure which affects joint stiffness to prolong the life of the system. To demonstrate the effects of lowering the target pressure it is first shown that there exists a trade-off between the commanded target pressures at steady-state and the steady-state error at the robot end effector under normal operation. It is then shown that lowering the target pressure (which is related to stiffness) can extend the operational life of the system when compressed air is a limited resource. For actuator leaks a lower target pressure for the leaking joint is used to demonstrate the trade-off between slowing the leak rate and system performance. For structural leaks a novel control algorithm is demonstrated to lower target pressure as much as possible to slow the leak while maintaining a user specified level of accuracy. The method developed for structural leaks extends the operational life of the robot. Long-term error during operation is decreased by as much as 50% of the steady-state error at the end effector when compared to performance during a leak without the control algorithm. For actuation leaks in a joint with a high-torque load the possibility of a 30% increase in operation time while only increasing steady-state error by 2 cm on average is demonstrated. For a joint with a low-torque load it is shown that up to a 300% increase in operation time with less than 1 cm increased steady-state error is possible. The work presented in this thesis demonstrates that varying stiffness may be used to extend the operational life of a robot when a leak has occurred. The work discussed here could be used to extend the available operation time of pneumatic robots. The methods and principles presented here could also be adapted for use on other types of robots to preserve limited system resources (e.g., electrical power) and extend their operation time.

Advancement in infrared imaging technology has allowed the thermal imaging to detect and visualize several gases, mostly hydrocarbon gases. In addition, infrared cameras could potentially be used as a non-contact temperature measurement for gas and vapor. However, current application of infrared imaging techniques for gas measurements are still limited due to several uncertainties in their performance parameters. The aim of this research work was to determine the key factors in the application of infrared imaging technology for gas visualization and a non-contact temperature measurement. Furthermore, the concentration profile and emission rate of the gas are predicted by combining the application of the infrared imaging method with gas dispersion modeling. In this research, infrared cameras have been used to visualize liquefied natural gas (LNG) plumes from LNG spills on water. The analyses of the thermograms showed that the apparent temperatures were different from the thermocouple measurement which occurred due to the assumption of that the object emissivity was always equal to unity. The emissivity for pure methane gas and a mixture of methane and atmospheric gases were then evaluated in order to obtain the actual temperature distribution of the gas cloud. The results showed that by including the emissivity value of the gas, the temperature profile of the dispersed gas obtained from a thermal imaging measurement was in good agreement with the measurement using the thermocouples. Furthermore, the temperature distribution of the gas was compared to the concentration of a dispersed LNG vapor cloud to obtain a correlation between the temperature and the concentration of the cloud. Other application of infrared imaging technique was also conducted for leak detection of natural gas from a pipeline. The capability of an infrared camera to detect a fugitive gas leak was combined with the simulation of vapor discharge and dispersion in order to obtain a correlation between the emission rates and the sizes of the gas plume to the minimum detectable concentration. The relationship of the methane gas cloud size to the gas emission rate was highly dependent to the prevailing atmospheric condition. The results showed that the correlation were best to predict the emission rate less than 0.2 kg/s. At higher emission rate, the increase in gas release rate did not change the size of the cloud significantly.

A ocorrência de elevados índices de perdas por vazamentos em sistemas de abastecimento de água é frequentemente ligada às inúmeras quebras de tubulações originadas em decorrência de elevados níveis de pressão atuantes. O controle efetivo de tais perdas requer a detecção e localização dos vazamentos para uma rápida reparação do sistema. Neste sentido, a consideração de análises hidráulicas no escoamento transitório tem se revelado especialmente útil aos propósitos de calibração e detecção de vazamentos. Tal análise pode revelar substancial quantidade de informações sobre as propriedades físicas e o nível de integridade do sistema, pois as ondas de pressão resultantes são afetadas pelos diversos dispositivos e fenômenos, incluindo os vazamentos. Assim, o presente trabalho visa o estudo dos transitórios hidráulicos para a calibração e detecção de vazamentos em modelos de sistemas de distribuição de água. Para tanto, são utilizados dados de redes hipotéticas e de laboratório, e modelos inversos resolvidos por métodos de busca global e local. Devido o emprego de tubos plásticos no circuito de laboratório, o clássico modelo da coluna elástica demonstrou-se ineficiente na reprodução do comportamento hidráulico de tal sistema. Resultados satisfatórios foram obtidos somente com um modelo hidráulico que considere o comportamento viscoelástico dos materiais dos tubos do circuito experimental. / The occurrence of large leakage losses in water supply systems has been frequently linked with pipe breaks resulting from high pressures levels in pipes. Efficient location of leakages is required in order to effectively control water losses and quickly repair the system. Analysis of hydraulic transients has been particularly useful for calibration and leak detection purposes. System observation for such analysis can reveal a substantial amount of information concerning physical properties and the integrity of the system, since water hammer waves are affected by different features and phenomena, including leaks. Thus, this research focuses on hydraulic transients for leak detection and calibration of water distribution system models. These objectives are achieved using data obtained from experiments performed on an experimental facility and numerical experiments on hypothetical networks. Inverse methods were based on both global and local search methods. Classic water hammer theory proved to be imprecise in describing the observed behavior of the hydraulic system composed of plastic pipes. Satisfactorily results were obtained with a hydraulic transient solver considering viscoelastic behavior of the pipe material.

O presente trabalho tem como objetivo principal o desenvolvimento de um sistema de identificação do surgimento de vazamentos (rupturas) em dutos, através da análise do sinal de sensores de pressão de resposta rápida (frequência de corte superior a 1 kHz). O reconhecimento do sinal de vazamento se realiza através de uma rede neural artificial feed-foward do tipo Perceptron Multi Camadas, previamente treinada. Neste trabalho, a implementação para tal operação foi feita off-line, mas devido ao baixo custo computacional pode ser facilmente implementada em eletrônica embarcada, em tempo real (on-line). Os resultados experimentais foram obtidos no oleoduto piloto do NETeF - Núcleo de Engenharia Térmica e Fluidos da USP - Universidade de São Paulo, com uma seção de testes com 1500 metros e diâmetro de 51,2 mm. Especificamente, os resultados foram obtidos com escoamento monofásico de água. Os resultados mostram-se promissores, visto que o sistema de redes neurais artificiais foi capaz de discriminar 2 universos linearmente separáveis, para sinais de vazamento e de não vazamento, para diversas vazões e localizações de vazamentos simulados. / The present dissertation deals with the development of a system to identify abrupt leaks (ruptures) in pipelines, by analyzing the signal of fast response pressure sensors (cutoff frequency over then 1kHz). The recognition of the leak signal is established by an artificial neural network feed-forward Perceptron Multi Layer, previously trained. In the present work the implementation was performed off-line, but due to low computational costs, the neural network can be easily implemented in real time embedded electronics (online). The experimental results were obtained in a 1500 meter-long and 51.2 millimeter-diameter pilot pipeline at the Center of Thermal Engineering and Fluids. Specifically, the results were obtained with single-phase flow of water. The results have proven to be promising, as the trained neural network was capable of classifying the 2 types of signals into 2 linearly separable regions, for leakage signals and no leakage signals, for various flow rates and locations of simulated leaks.

This research used an Integrated Water Resource Management approach to investigate how Water Demand Management (WDM) measures at government, utility and end-user levels could contribute to providing sustainable water supply to Bahrain, which is in an arid to semiarid region. The main driver for this research was the supply-driven orientation favoured by policy makers and practitioners in Bahrain with little consideration for demand management. This leads to a high estimated gross per capita consumption 525 l/c/d as of 2010. There was also a need to investigate the institutional environment for managing water resources and delivering sustainable water supply to Bahrain. The research adopted a case study methodology which included qualitative analysis of interviews and documents from the water authority, and quantitative analysis of questionnaire surveys and pilot studies. The research adopted a cross-sectional approach to the analysis of activities associated with WDM practice in Bahrain. All findings and conclusions were evaluated/validated using surveys distributed to water experts and customers. Based on their feedback, findings and conclusions were revised. The main finding of this research was that the tariff is highly subsidized by the government and there is no encouragement for water savings. The low tariff leads to low revenue which in turn affects the budget allocated to the relevant departments and units at the Electricity and Water Authority (EWA). This impacts negatively on their activities. It was found that there is no effective strategy for integrated water resources management; there is a high level of Non Revenue Water (NRW) (38%); and limited reuse of grey water and water use saving devices. In addition there is a lack of public awareness and understanding of the benefits of WDM among all levels of society including professionals and water supply providers. The research concluded that improving water use efficiency in Bahrain should be a priority due to the current high water supply costs. There is a need for proper legislation that enforces the use of WDM; establishment of a national WDM committee with the Water Resources Directorate, and for water resource professionals to follow WDM oriented policies. The research proposed six areas to be further investigated to achieve more efficient use of water: (a) Water tariff reform to recover full water supply costs; (b) institutional reform through activating and enforcing Water Resources Council roles; (c) promoting public awareness about WDM and its benefits; (d) reducing non revenue water; (e) applying positive economic sliding scale incentives for customers who reduce their water consumption.

This diploma thesis deals with the study of leakage problems in industry and the use of Agilent weight detectors for its detection. Based on the studies conducted, a hardware and software solution has been proposed for connecting the measuring elements to a helium detector at a simple configurable station. Additionally, a C# application was created. This application allows the leak detector to be controlled and data collected from the detector and its surroundings. The created application was tested in a real environment. The conclusion of this work is devoted to the possibilities of using the created application.

abstract: Water is one of, if not the most valuable natural resource but extremely challenging to manage. According to old research in the field, many Water Distribution Systems (WDSs) around the world lose above 40 percent of clean water pumped into the distribution system because of unfortune leaks before the water gets anywhere from the fresh water resources. By reducing the amount of water leaked, distribution system managers can reduce the amount of money, resources, and energy wasted on finding and repairing the leaks, and then producing and pumping water, increase system reliability and more easily satisfy present and future needs of all consumers. But having access to this information pre-amatively and sufficiently can be complex and time taking. For large companies like SRP who are moving tonnes of water from various water bodies around phoenix area, it is even more crucial to efficiently locate and characterize the leaks. And phoenix being a busy city, it is not easy to go start digging everywhere, whenever a loss in pressure is reported at the destination. Keeping this in mind, non-invasive methods to geo-physically work on it needs attention. There is a lot of potential in this field of work to even help with environmental crisis as this helps in places where water theft is big and is conducted through leaks in the distribution system. Methods like Acoustic sensing and ground penetrating radars have shown good results, and the work done in this thesis helps us realise the limitations and extents to which they can be used in the phoenix are. The concrete pipes used by SRP are would not be able to generate enough acoustic signals to be affectively picked up by a hydrophone at the opening, so the GPR would be helpful in finding the initial location of the leak, as the water around the leak would make the sand wet and hence show a clear difference on the GPR. After that the frequency spectrum can be checked around that point which would show difference from another where we know a leak is not present. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019