System Reliability Assessment of Offshore Pipelines

The title of this thesis, System Reliability Assessment of Offshore Pipelines, portrays the application of probabilistic methods in assessing the reliability of these structures. The main intention of this thesis is to identify, apply and judge the suitability of the probabilistic methods in evaluating the system reliability of offshore pipelines subjected to corrosion. The analysis was first emphasized on interpreting corrosion data as random variables and probabilistic functions, through which uncertainties of the corrosion inspection tool could be taken into account. The reliability of the pipeline was initially studied by treating the structure as an independent unit. The analysis was further elaborated for pipelines arrayed as a series system of units, with the consideration of length effects. A framework for the reliability-based maintenance model was also developed in this thesis, aiming at optimizing the pipeline system operations. Herein, the analysis was mainly focused on improving the practice of releasing corrosion inhibitors into the pipeline. The use of inhibitors is considered to be the most applied maintenance practice among pipeline industries because of its simple mechanism to fight against corrosions. Last but not least, the thesis also looked into interpreting corrosions in space using theories on hydrodynamics.Hydraulic EngineeringCivil Engineering and Geoscience

Risk based maintenance of a cross-country petroleum pipeline system

This paper proposes a data-driven approach in determining an optimal inspection interval for a petroleum pipeline system. The approach accounts for the determination of both the probability of failure and its associated consequences. The probability of failure is estimated by fitting the historical data of failure of the pipeline into either a homogenous Poisson process or non-homogenous Poisson process (power law). The analysis of historical data reveals the Poisoneous form that gives better description of the failure process. The consequences of failure are calculated in terms of economic loss, environmental damage and loss of human life. Both the failure probability and consequences are utilized to estimate the total loss of an operating pipeline system. A risk based integrity maintenance optimization of the pipeline is achieved by minimizing the economic loss, while taking the human risk and maintenance budget as constraints. The proposed framework is utilized in the maintenance planning of a very long cross country petroleum pipeline system. The outcomes are robust and well validated. The framework can be applied to any engineering system that requires inspection and maintenance planning.Hydraulic EngineeringCivil Engineering and Geoscience

Reliability assessment for corroded pipelines in series considering length-scale effects

This paper presents a method for assessing the reliability of a corroded pipeline placed in series, with special consideration given to the effect of the length scale imposed by each segment of the pipe. The features of corrosion in different pipe segments are statistically correlated; thus, a failure in one section may impact the adjacent sections. Herein, using a correlation distance parameter, such statistical correlation is described considering the length-scale effects. The reliability of the corroded pipeline is presented in the form of a failure probability. The results show that analysing a corroded pipeline by considering length-scale effects produces a higher failure probability compared with the case where such effects are excluded, even when the parameters that govern corrosion in a pipeline are included in the analysis.Safety and Security Scienc