Squeeze-off & gel patch repair methods for polyethylene pipe in natural gas distribution lines

Graduation date: 2007The natural gas industry has become essential in many areas in the United States. Currently there is over 37.5 million miles of natural gas distribution lines. A large majority of these lines are polyethylene pipes. With such a large percentage of polyethylene lines in use gas companies are continually looking for ways to improve repair procedures.\ud The focus of this work was two fold. One of the objectives was to mechanically characterize the squeeze-off of polyethylene pipe, assess damage (if any) to the pipe and use this information in the design of a squeeze-off tool that could be used in a keyhole (18 inch diameter hole) by a single operator. Equations were developed to predict required squeeze-off forces under different conditions, such as temperature, tool radius, squeeze-rates, and swivel versus fixed jaws. This tool is now in commercial use across the US.\ud The second objective was the development a patch consisting of a solvent swollen polyethylene film that can be applied to a live natural gas line, in a keyhole if necessary. This patch is applied under elevated temperature conditions allowing for a modified solvent weld, effectively repairing pipe lines in a quarter of the time of current repair procedures