Karen Crippen, Ernest Lever
Papers # 2014 Chicago
DOT/PHMSA held a Government/Industry Pipeline R&D Forum on July 18-19, 2012. Five working groups met to discuss key pipeline technical challenges facing industry and government. The Design/Materials/Welding-Joining & Valves working group identified the effects of hydrocarbon permeation on plastic pipe strength and fusion performance as a gap that needs to be addressed. There is mounting evidence in certain regions that PE gas distribution pipelines are being exposed to hydrocarbon contamination. Because PE is nonpolar, it is a very poor barrier to nonpolar hydrocarbons as might be found in the natural gas industry. In the case of liquid permeation, the diffusion phenomenon occurs in areas of gross contamination when liquid hydrocarbon condensates form in gas pipelines, or when soil surrounding the pipe is heavily contaminated with liquid hydrocarbons (diesel, gasoline, etc.). The presence of these hydrocarbons in the plastic matrix can have a negative influence on two important aspects associated with gas operations: thermal fusion quality and pipe strength. The magnitude of the impact depends on the amount of contamination. The most common issue is that heat joining techniques on hydrocarbon permeated pipes may result in lower strength joints. Because the source of contamination can be both internal and external, it can affect any type of saddle and butt fusions. If the pipe wall is weakened, it may require derating. Also of interest is the impact of impregnated hydrocarbons on slow crack growth (SCG). It is not understood whether the presence of hydrocarbons inhibits or accelerates SCG. This paper will provide an update on the status of the two year research project that GTI has undertaken to quantify the effects of hydrocarbon contamination on PE pipe. Current results will be presented and discussed at the conference presentation.
