In this thesis the procedures for qualifying fiberglass pipes are discussed in relation to industry needs. The ultimate elastic wall stress (UEWS) test appears to provide an efficient means of rating pressure pipes, and indeed vessels, for cases where weepage failure occurs resulting from the accumulation of matrix cracks. The principle behind the UEWS test is to identify from stress-strain response, a stress level below which damage growth is either negligible or at least sufficiently low to avoid failure within the design life. An experimental investigation into the UEWS of ±55⁰ filament wound composite pipes has been conducted under various load and environmental conditions. The pipes were subjected to biaxial loading, which was achieved by a combination of hoop and axial stress loading. Loads were applied as groups of 10 one-minute pressure cycles, recording the hoop or/and axial strain. These pressure groups were gradually increased until the UEWS had been determined. Various ratios of hoop to axial stress were applied, ranging from pure axial to pure hoop loading at room temperature, 65⁰C and 95⁰C. These ratios were investigated by applying different pressures in both the main and small chambers built inside the pipe, and therefore it was unnecessary to add external load to the pipe wall. Tests were stopped at the first observed leakage through the pipe wall. The UEWS test appears to provide an attractive alternative to the currently used procedure laid down in ISO 14692. This involves an expensive series of long term constant pressure tests described in ASTM 2992, running for over 10,000 hours. It is shown here that the UEWS test reflects the cyclic fatigue behaviour of fiberglass pipe, but further work on the relationship between cyclic and static behaviour is needed. The test results are presented in the form of UEWS and failure envelopes showing the effects of testing at elevated temperature, and the degradation in pipe properties as the test progressed. Acoustic emission examinations were also conducted to detect damage development in the GRE pipes during the tests, allowing its compatibility with the UEWS test to be assessed. Four different types of failure mode were observed according to the loading conditions. It has been shown that a Miner‟s Law approach is effective in modelling damage due to combined static and cyclic effects, and that damage can be directly related to matrix crack growth. This approach could form the basis of future procedures for describing the lifetime behaviour of GRE pipes under any required combination of static, fatigue, hydrostatic and non-hydrostatic (multi-axial) loading.

In this thesis, the development on Fault Detection and Isolation (FDI) and its application on the nonlinear pipeline based on an observer design techniques are presented. The main focus is to perform the analysis on pipeline systems characteristics and then, systematic approaches are designed for leak diagnosis system based on transient response. In order to monitor the transient response,three different types of observer designs are introduced in this work together with different aspects of leakage are discussed. Each of the presented observer design methods significantly reduce the required time for leak detection and location. A model is developed on the basis of motion and continuity equations for the single pipeline systems. These equations are derived from fluid transient flow through a cylindrical pipe. The systems are, then, measured by transient flow and pressure measuring devices at two signals point in the beginning and the end of pipeline. The research, devoted primarily to continuous monitoring of the flowrate and pressure that are performed along the pipeline systems. The steady-state analysis technique is verified using simulation via FDI procedure. Presented methods are derived using knowledge from different research fields such as mathematical modelling, systematic inspection and monitoring techhniques. The structure of this thesis is set out in a systematic way so that each of the derived techniques is presented in an individual chapter, which can be read separately.

From the water quality perspective, looking at a sewer system as a reactor whose effluent should be regulated in terms of water quality, solute tracer studies need to be undertaken to define the retention and spread of temporally varying concentrations. Focussing on a manhole, its aspects such as shape, ratio of pipe and manhole diameter, and pipe direction all affect the transport of the solute through the sewer system. The aim of this study is to quantify the magnitude and changes in dispersive fraction (y) used in the ADZ technique, and head loss coefficient (K) due to changes in pipe direction across a manhole. Under surcharge conditions, solute transport along plane angles such as 0°, 30°, 60° and 90°, of an inlet and an outlet pipes with/without benching was investigated for a range of surcharge and discharge. Additionally, the head losses due to such an angle were also measured. From data analysis, both the dispersive fraction and the head loss coefficient were properties of each plane angle. For example, at the angle of 300 -unbenched, the dispersive fraction was constant at approximately 0.7 and the head loss coefficient was constant at about 2.22. Moreover, these comprehensive processed data were beneficial to basic knowledge of solute mixing. First, the square root of the ratio of head loss and residence time, represented by energy dissipation, was found to be linear to flow rate. Hence, it might be used as a conversion of a head loss to residence time. Second, two cell ADZ technique was developed to enhance the travel time prediction of a downstream concentration profile. The two cell technique was able to predict the concentration profile very well, but due to difficulty in application, a single cell ADZ technique was more useful in general.

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The behaviour of piping elbows under bending and internal pressure is more complicated than expected. The main problem is that the coupling of bending and internal pressure is non-linear; stress and displacement cannot be added according to the principle of superposition. In addition, internal pressure tends to act against the effect caused by the bending moment. If bending moment ovalises the elbow crosssection, with internal pressure acting against this deformation, then the deformed cross-section tries to deform back to the original circular shape. It is then introduced the term ''pressure reduction effect". Current design piping code treats the pressure reduction effect equally for in-plane (closing and opening) moment and out-of-plane moment. In this thesis, the pressure reduction effect is reassessed for in-plane closing moment through parametric study by performing detailed large deformation finite element analysis. The study is then extended to assess the pressure reduction effect for inplane opening moment and out-of-plane moment. Approximate formulae for ovalisation, flexibility, and stress-intensification factor are developed through a systematic analysis of the finite element generated data. Comparison of results presented in this thesis and the current ASME piping code for the pressure reduction effect under in-plane closing bending confirms that the ASME code formulae underestimates the pressure reduction for flexibility and stress-intensification. If the ASME formulae are applied for in-plane opening bending and out-of-plane bending, it overestimates the pressure reduction for the flexibility factor. If the ASME formulae for the pressure effect on stress-intensification factor is applied, it underestimates the pressure reduction for closing bending and out-of-plane bending, but overestimates for opening bending. It is therefore proposed that different formula for different direction of bending load should be used and the results presented in this thesis should be useful for this purpose.

This Engineering Doctorate is concerned with change detection. The application of fuzzy clustering and fuzzy classification for online pipeline leak detection is investigated. Three different fuzzy methodologies are derived using one real data set and tested on multiple other real data sets. The first classification methodology, based on a fixed classifier, uses a novel merging algorithm developed to reduce the influence of cluster initialisation on the data space partition. Rules derived from this partition are subsequently used in the second methodology, to define a linguistic rule-based system, classifying without clustering. Instead, it evaluates membership functions to classify. The third methodology is a combination of the previous two, enhanced with cluster rejection and statistical change detection in the form of Shewhart charts.

Electrical Impedance Tomography (ElT) has been used as a visualisation and measurement tool in many fields such as medical imaging, geophysical prospecting and industrial process applications. To date, single sensing ring strategies and two-dimensional (2D) electric field reconstruction algorithms are mostly used in ElT applications. The quality of measurement will be affected by the three-dimensional (3D) effects that cause imaging errors in both the near-sensor-region and the spatial coordination of a conventional 2D sensor. The typical errors include the object off-plane sensing and offpath trajectory effects - objects lying a short axial distance from the image plane are reconstructed closer to the central axis than their true position. There is a distinct possibility that it may also give a rise to erroneous velocity components normal to the axial direction. The aim of this thesis is to reduce the 3D effects by designing and implementing a full 3D pipeline sensing strategy which takes into account of the 3D nature of the ElT sensing field. The main approaches of the thesis are: (1) a new sensing system, the Zigzag sensor, which represents a new electrode configuration has been designed; (2) a fast forward solver, using Finite Element Modelling, has been implemented with the aim of achieving real-time processing of tomographic measurements; (3) the Sensitivity Conjugate Gradient (SCG) Algorithm has been adapted to 3D ElT for the first time. Moreover, the thesis contributes towards the application of the developed 3D ElT system for dynamic flow visualisation and velocimetry with 3D auto-correlation method which provided a balance between the requested imaging precision and computation speed. The thesis details both theoretical and experimental approaches as well as evidences that the zigzag sensor with the 3D SCG offers some advantage over conventional methods to reduce the 3D effects on ElT pipeline imaging.

To relieve the axial stress induce rature high-pressure pipelines in deepwater, current design methods leave the pipe unburied and allow the formation of the lateral buckles along the pipeline in a controlled manner. However, this approach requires a better understanding of the interaction between the seabed soil and the partially embedded pipeline under both vertical and lateral movements. Research has been carried out to examine the two soil-pipe interaction mechanisms, vertical pipe penetration and lateral pipe movement, involved in the installation and operation of an on-bottom offshore pipeline. The findings reported in this thesis improve the current knowledge of pipe-soil interaction in clay. A series of physical model tests was conducted to investigate the behaviour of pipe penetration and lateral pipe movement in clay. The experiments were carried out using short pipe sections in a I g model tank equipped with a transparent Perspex window in the front panel, from which high quality images were obtained for the measurement of the soil deformation in the tests using an image analysis technique. The computational limit analysis, Discontinuity Layout Optimisation (DLO), was adopted to back-analyse and compare with the experimental results. In addition, parametric studies were conducted using DLO to investigate the effects of the change in soil geometry and soil condition on the pipe resistances and soil flow mechanisms for the vertical pipe penetration and the lateral pipe sweep processes. Experimental results showed that pipe penetration, prior to the fully embedded flow-around failure mechanism at very deep penetrations, involves four distinct stages in development of the failure mechanism from 'soil heave' to 'local flow-around' at shallow and deep pipe embedments, respectively. Good agreement was observed between the experimental and numerical results. The results of the parametric studies suggested that the onset depth of the fully embedded flow-around failure mechanism is strongly dependent on the undrained strength profile and tensile strength of the soil. The lateral resistance of a partially embedded pipe under different loading conditions was measured at both small and large lateral displacements. Results showed that the lateral resistance is strongly affected by the change in soil geometry, soil heave induced by the initial penetration and formation of the active berm in front of the pipe during lateral movements. Based on the results from the numerical and experimental studies, design equations are proposed for the predictions of (i) the pipe penetration resistance at both shallow and deep embedments, and (ii) the lateral resistance of a partially embedded pipe under combined vertical and horizontal loads at both small and large lateral displacements.

No description available.

No description available.