Plastic pipe, primarily polyethylene pipe, offers natural gas utilities significant operational and economic advantages over traditional materials. Plastic pipe is not subject to corrosion, and it costs less to install and maintain than steel or cast-iron main. The percentage of plastic natural gas distribution mains in place in the United States grew from 29 percent in 1993 to over 50 percent in 2007. The percentage of plastic natural gas services installed in the United States rose from 41 percent in 1993 to over 63 percent in 2007.
The U.S. Department of Transportation (DOT) is seeking to respond to a recommendation by the National Transportation Safety Board (NTSB) that raised concerns about the susceptibility of older generation plastic pipe to brittle cracking. Some of the plastic pipe manufactured almost 40 years ago was susceptible to cracking, mostly in combination with other stress factors such as improper installation or environmental causes. Most of the pipe that was subject to failure in this manner has been replaced or dealt with appropriately.
AGA strives to ensure plastic pipe is used safely and effectively by natural gas utilities, in part by working with DOT, standards organizations and other stakeholders to make sure regulations and reference materials keep pace with technology and industry trends.
The AGA, American Public Gas Association, Plastics Pipe Institute, National Association of Regulatory Utility Commissioners, National Association of Pipeline Safety Representatives, NTSB and DOT participate on a committee that collects and assesses in-service plastic piping material failures with the objective of identifying possible trends in the performance of these materials. Collected data include both actual failures and negative reports (forms that indicate that no failure occurred during the month). AGA has collected this data on behalf of the committee since January 2001, and the data is examined each time the committee meets in an effort to identify trends in the performance of plastic piping materials. The committee has developed a DOT response to address the NTSB’s concerns, identifying the older materials susceptible to such failure and a DOT notification to industry. To date, approximately 162 companies representing 51 percent of the miles of installed plastic main and 56 percent of the installed plastic services in the United States have joined the data collection program, and AGA continues to urge companies with plastic main or services to join the voluntary data collection effort.
More than seven years’ worth of collected data reinforce what is historically known about certain older plastic piping materials and components. Thus far, this collection of data has not shown additional trends. In an effort to assist gas utilities, the Gas Piping Technology Committee (GPTC) prepared guidance material that an operator can use when these older plastic pipe materials are known to be present in their piping system. This guidance material was published in 2005.
In addition, the AGA Plastic Materials Committee has updated the AGA Plastic Pipe Manual (2007). This manual contains information on plastic pipeline materials, including factors affecting plastic piping performance, engineering consideration for plastic pipe utilization, installation guidance and other valuable information. Finally, the committee is compiling a series of documents that capture plastic material information to be of use for gas companies in Distribution Integrity Management Programs.
AGA Contact: Christina Sames, (202) 824-7214, firstname.lastname@example.org