[Federal Register Volume 64, Number 47 (Thursday, March 11, 1999)]
[Notices]
[Pages 12212-12213]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-6051]


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DEPARTMENT OF TRANSPORTATION

Research and Special Programs Administration


Potential Failures Due to Brittle-Like Cracking of Older Plastic 
Pipe in Natural Gas Distribution Systems

AGENCY: Research and Special Programs Administration (RSPA), DOT.

ACTION: Notice; issuance of advisory bulletin on brittle-like failures 
of plastic pipe to owners and operators of natural gas distribution 
systems.

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SUMMARY: RSPA is issuing this advisory bulletin to owners and operators 
of natural gas distribution systems to inform them of the potential 
vulnerability of older plastic gas distribution pipe to brittle-like 
cracking. The National Transportation Safety Board (NTSB) recently 
issued a Special Investigation Report (NTSB/SIR-98/01), Brittle-like 
Cracking in Plastic Pipe for Gas Service, that described how plastic 
pipe installed in natural gas distribution systems from the 1960s 
through the early 1980s may be vulnerable to brittle-like cracking 
resulting in gas leakage and potential hazards to the public and 
property. RSPA has also issued an additional advisory bulletin (ADB-99-
01) reminding natural gas distribution system operators of the 
potential poor resistance to brittle-like cracking of certain 
polyethylene pipe manufactured by Century Utility Products, Inc.

ADDRESSES: This document can be viewed on the Office of Pipeline Safety 
(OPS) home page at: http://ops.dot.gov.

FOR FURTHER INFORMATION CONTACT: Gopala K. Vinjamuri, (202) 366-4503, 
or by email at [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    The National Transportation Safety Board (NTSB) recently issued a 
Special Investigation Report (NTSB/SIR-98/01), Brittle-like Cracking in 
Plastic Pipe for Gas Service, that described how plastic pipe installed 
in natural gas distribution systems from the 1960s through the early 
1980s may be vulnerable to brittle-like cracking resulting in gas 
leakage and potential hazards to the public and property. An NTSB 
survey of the accident history of plastic pipe suggested that the 
material may be susceptible to premature brittle-like cracking under 
conditions of local stress intensification because of improper joining 
or installation procedures. Hundreds of thousands of miles of plastic 
pipe have been installed, with a significant amount installed prior to 
the mid-1980s. NTSB believes any vulnerability of this material to 
premature failure could represent a potentially serious hazard to 
public safety.
    The NTSB report addressed the following safety issues:
     The vulnerability of plastic pipe to premature failures 
due to brittle-like cracking;
     The adequacy of available guidance relating to the 
installation and protection of plastic pipe connections to steel mains; 
and
     Performance monitoring of plastic pipeline systems as a 
way of detecting unacceptable performance in piping systems.
    Copies of this report may be obtained by calling NTSB's Public 
Inquiry Office at 202-314-6551.
    The phenomenon of brittle-like cracking in plastic pipe as 
described in the NTSB report and generally understood within the 
plastic pipeline industry relates to a part-through crack initiation in 
the pipe wall followed by stable crack growth at stress levels much 
lower than the stress required for yielding, resulting in a very tight 
slit-like opening and gas leak. Although significant cracking may occur 
at points of stress concentration and near improperly designed or 
installed fittings, small brittle-like cracks may be difficult to 
detect until a significant amount of gas leaks out of the pipe, and 
potentially migrates into an enclosed space such as a basement. 
Premature brittle-like cracking requires relatively high localized 
stress intensification that may be a result from geometrical 
discontinuities, excessive bending, improper fitting assemblies, and/or 
dents and gouges. Because this failure mode exhibits no evidence of 
gross yielding at the failure location, the term brittle-like cracking 
is used. This phenomenon is different from brittle fracture, in which 
the failure results in fragmentation of the pipe.
    The report suggests that the combination of more durable plastic 
pipe materials and more realistic strength testing has improved the 
reliability of estimates of the long-term hydrostatic strength of 
modern plastic pipe and fittings. The report also documents that older 
polyethylene pipe, manufactured from the 1960s through the early 1980s, 
may fail at lower stresses and after less time than was originally 
projected. NTSB alleges that past standards used to rate the long-term 
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.
    In 1998, NTSB made several recommendations to trade organizations 
and to the Research and Special Programs Administration (RSPA) on the 
need for a better understanding of the susceptibility of plastic pipe 
to brittle-like cracking. NTSB recommended that RSPA ``[d]etermine the 
extent of the susceptibility to premature brittle-like cracking of 
older plastic piping (beyond that marketed by Century Utilities 
Products Inc.) that remains in use for gas service nationwide.''

II. Advisory Bulletin (ADB-99-02)

    To: Owners and Operators of and Natural Gas Distribution Pipeline 
Systems
    Subject: Potential susceptibility of plastic pipe installed between 
the 1960 and the early 1980s to premature failure due to brittle-like 
cracking.
    Purpose: To inform natural gas distribution pipeline operators of 
the need to determine the extent of susceptibility to brittle-like 
cracking of plastic pipe installed between the years 1960 and early 
1980s.
    Advisory: A review of Office of Pipeline Safety (OPS) reportable 
natural gas pipeline incidents and the findings of NTSB Special 
Investigation Report (NTSB/SIR-98/01) indicates that certain plastic 
pipe used in natural gas distribution service may be susceptible to 
brittle-like cracking. The standards used to rate the long-term 
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.
    It is recommended that all owners and operators of natural gas 
distribution systems identify all pre-1982 plastic pipe installations, 
analyze leak

[[Page 12213]]

histories, and evaluate any conditions that may impose high stresses on 
the pipe. Appropriate remedial action, including replacement, should be 
taken to mitigate any risks to public safety.

    Authority: 49 U.S.C. Chapter 601; 49 CFR 1.53.

    Issued in Washington, D.C. on March 3, 1999.
Richard B. Felder,
Associate Administrator for Pipeline Safety.
[FR Doc. 99-6051 Filed 3-10-99; 8:45 am]
BILLING CODE 4910-60-P