Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Civil and Environmental Engineering

Supervisor

Dr. Wenxing Zhou

Abstract

Statistical analyses of the pipe-related incident data for onshore gas transmission pipelines between 2002 and 2013 collected by the Pipeline and Hazardous Material Safety Administration (PHMSA) of the United States Department of Transportation (DOT) are conducted. It is found that the total length of the onshore gas transmission pipelines in the US is approximately 480,000 km as of 2013. The third-party interference, external corrosion, material failure and internal corrosion are the leading causes for the pipe-related incidents, responsible for over 75% of the total incidents between 2002 and 2013. Based on the pipeline mileage and incident data, the average rate of rupture incidents over the 12-year period between 2002 and 2013 is calculated to be 3.1 × 10-5 per km per year. Furthermore, external corrosion is found to be the leading cause for rupture incidents, with a corresponding rupture rate of 1.0 × 10-5 per km per year

A log-logistic model is developed to evaluate the probability of ignition (POI) given a rupture of an onshore gas transmission pipeline using the maximum likelihood method based on a total of 188 rupture incidents between 2002 and 2014 collected from the PHMSA pipeline incident database. The product of the pipeline internal pressure at the time of incident and outside diameter squared is observed to be strongly correlated to POI while the location class of the pipeline is not, and thus the former is adopted as the sole predictor in the model. The 95% confidence interval is evaluated, and for practical engineering use, the 95% upper confidence bound is tabulated in a look-up table. The proposed model is further validated using an independent dataset reported in the literature.

The quantitative risk assessment of a hypothetical onshore gas transmission pipelines is illustrated by incorporating the statistics of the pipeline rupture incidents and POI model obtained in the present study. The thermal radiation hazards resulting from an ignited rupture of the pipeline are quantified using the well-known C-FER model. The heat intensity thresholds leading to fatality and injury for both the outdoor and indoor exposure conditions are selected from the literature. The societal risk is then evaluated in terms of the expected number of casualties and F-N curve for the population located in the vicinity of the pipeline, whereas the individual risk is calculated as the annual probability of casualty of a specific individual located in the vicinity of the pipeline. The F-N curve is evaluated for each one kilometer section of the pipeline such that the section corresponding to the most critical F-N curve is identified.

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