Special Investigation Report
Brittle-Like Cracking in
Plastic Pipe for Gas Service
Special Investigation Report
Brittle-Like Cracking in
Plastic Pipe for Gas Service
NTSB Number SIR-98/01
NTIS Number PB98-917001
PDF Document (833K)
Synopsis: Despite the general acceptance of plastic piping
as a safe and economical alternative to piping made of steel or other materials,
the National Transportation Safety Board notes that a number of pipeline
accidents it has investigated have involved plastic piping that cracked
in a brittle-like manner. This special investigation report concludes that
the procedure used in the United States to rate the strength of plastic
pipe may have overrated the strength and resistance to brittle-like cracking
of much of the plastic pipe manufactured and used for gas service from
the 1960s through the early 1980s. As a result, much of this piping may
be susceptible to premature brittle-like failures when subjected to stress
intensification, and these failures represent a potential public safety
hazard.
The safety issues discussed in this report are the vulnerability of plastic piping to premature failures due to brittle-like cracking; the adequacy of available guidance relating to the installation and protection of plastic piping connections to steel mains; and performance monitoring of plastic pipeline systems as a way of detecting unacceptable performance in piping systems.
As a result of this special investigation, the National Transportation Safety Board issued recommendations to the Research and Special Programs Administration, the Gas Research Institute, the Plastics Pipe Institute, the Gas Piping Technology Committee, the American Society for Testing and Materials, the American Gas Association, MidAmerican Energy Corporation, Continental Industries, Inc., Dresser Industries, Inc., Inner-Tite Corporation, and Mueller Company.