[Federal Register Volume 67, Number 228 (Tuesday, November 26, 2002)]
[Notices]
[Pages 70806-70808]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-30055]


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DEPARTMENT OF TRANSPORTATION

Research and Special Programs Administration


Notification of the Susceptibility To Premature Brittle-Like 
Cracking of Older Plastic Pipe

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

ACTION: Notice; issuance of advisory bulletin.

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SUMMARY: RSPA is issuing this follow-up advisory bulletin to owners and 
operators of natural gas distribution systems to inform them of the 
susceptibility to premature brittle-like cracking of older plastic pipe 
and the voluntary efforts to collect and analyze data on plastic pipe 
performance. A Special Investigation Report issued by the National 
Transportation Safety Board (NTSB) 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. On March 11, 
1999, RSPA issued two advisory bulletins on this issue. The first 
bulletin reminded natural gas distribution system operators of the 
potential poor resistance to brittle-like cracking of certain 
polyethylene pipe manufactured by Century Utility Products, Inc. The 
second bulletin advised natural gas distribution system operators of 
the potential vulnerability of older plastic pipe to brittle-like 
cracking.

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 e-mail at [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    On April 23, 1998, NTSB issued a Special Investigation Report 
(NTSB/SIR-98/01), Brittle-like Cracking in Plastic Pipe for Gas 
Service, that describes 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 
early-1980s. NTSB believes any vulnerability of this material to 
premature cracking could represent a potentially serious hazard to 
public safety. Copies of this report may be obtained by calling NTSB's 
Public Inquiry Office at 202-314-6551.
    RSPA has already issued two advisory bulletins on this issue. The 
first advisory bulletin, ADB-99-01, which was published in the Federal 
Register on March 11, 1999 (47 FR 12211), reminded natural gas 
distribution system operators of the potential poor resistance to 
brittle-like cracking of certain polyethylene pipe manufactured by 
Century Utility Products, Inc. The second advisory bulletin, ADB-99-02, 
also published in the Federal Register on March 11, 1999 (47 FR 12212), 
advised natural gas distribution system operators of the potential 
brittle-like cracking vulnerability of plastic pipe installed between 
the 1960s and early 1980s.
    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 openings and gas leaks. 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 installation of fittings, 
and 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 pipe failure causes fragmentation of the pipe.
    The NTSB 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

[[Page 70807]]

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 RSPA on the need for a better understanding of the 
susceptibility of plastic pipe to brittle-like cracking. This advisory 
bulletin responds to one of the NTSB recommendations. It is 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. Inform gas system operators of the findings and require 
them to closely monitor the performance of the older plastic piping and 
to identify and replace, in a timely manner, any of the piping that 
indicates poor performance based on such evaluation factors as 
installation, operating, and environmental conditions; piping failure 
characteristics; and leak history.''
    In order to obtain the most complete information on the extent of 
the susceptibility to premature brittle-like cracking of older plastic 
pipe, a meeting was convened in May 1999 with all the stakeholders to 
determine how information on older plastic pipe could be assembled. The 
meeting included representatives of the American Gas Association (AGA), 
the American Public Gas Association (APGA), the Gas Research Institute 
(GRI) (now the Gas Technology Institute), the Midwest Energy 
Association (MEA), and the Plastic Pipe Institute (PPI).
    As a result of the May 1999 meeting, the Joint Government-Industry 
Plastic Pipe Study Committee was formed to address the recommendations 
of the NTSB Special Investigation Report. The committee held three 
separate meetings to prepare a draft response to the NTSB 
recommendations and a draft industry notification of brittle-like 
cracking problems, the subject of this advisory bulletin. The committee 
membership consisted of a representative from OPS, a gas distribution 
operator from AGA, and the Transportation Safety Institute. Meetings 
were facilitated by General Physics Corporation, Columbia, MD. One of 
the committee findings was that there is a lack of data available from 
the industry to completely identify older plastic pipe that is still in 
service and may be susceptible to brittle-like cracking.
    This finding led to the formation of the Plastic Pipe Database 
Committee (PPDC) to develop a process for gathering data on future 
plastic pipe failures with involvement from the states, which have 
assumed the authority from OPS over gas distribution systems, where 
most of the plastic pipe is installed. The PPDC is comprised of 
representatives from Federal and State regulatory agencies and from the 
natural gas and plastic pipe industries. Members include AGA, APGA, 
PPI, the National Association of Regulatory Utility Commissioners 
(NARUC), the National Association of Pipeline Safety Representatives 
(NAPSR), and OPS.
    The PPDC database is expected to improve the knowledge base of gas 
utility operators and regulators and is intended to help reveal any 
failure trends associated with older plastic piping materials. The 
PPDC's mission is ``to develop and maintain a voluntary data collection 
process that supports the analysis of the frequency and causes of in-
service plastic piping material failures.'' It provides an opportunity 
for government and industry to work together to evaluate the extent of 
plastic pipe performance problems and to mitigate any risks to safety. 
The PPDC started gathering data in January 2001 from OPS and State 
pipeline safety agencies. For more information on the PPDC, go to the 
AGA Web page (http://www.aga.org), and enter ``PPDC'' in the keyword 
search.

II. Advisory Bulletin (ADB-02-7)

    To: Owners and Operators of Natural Gas Distribution Pipeline 
Systems.
    Subject: Notification of the Susceptibility to Premature Brittle-
like Cracking of Older Plastic Pipe.
    Advisory: In recent years, brittle-like cracking has been observed 
in some polyethylene pipes installed in gas service through the early 
1980s. This brittle-like cracking (also known as slow crack growth) can 
substantially reduce the service life of polyethylene piping systems.
    The susceptibility of some polyethylene pipes to brittle-like 
cracking is dependent on the resin, pipe processing, and service 
conditions. A number of studies have been conducted on older 
polyethylene pipe. These studies have shown that some of these older 
polyethylene pipes are more susceptible to brittle-like cracking than 
current materials. These older polyethylene pipe materials include the 
following:
    [sbull] Century Utility Products, Inc. products.
    [sbull] Low-ductile inner wall ``Aldyl A'' piping manufactured by 
Dupont Company before 1973.
    [sbull] Polyethylene gas pipe designated PE 3306. (As a result of 
poor performance this designation was removed from ASTM D-2513.)
    The environmental, installation, and service conditions under which 
the piping is used are factors that could lead to premature brittle-
like cracking of these older materials. These conditions include, but 
are not limited to:
    [sbull] Inadequate support and backfill during installation.
    [sbull] Rock impingement.
    [sbull] Shear/bending stresses due to differential settlement 
resulting from factors such as:

--Excavation in close proximity to polyethylene piping
--Directional drilling in close proximity to polyethylene piping
--Frost heave

    [sbull] Bending stresses due to pipe installations with bends 
exceeding recommended practices.
    [sbull] Damaging squeeze-off practices.
    Service temperatures and service pressures also influence the 
service life of polyethylene piping. Piping installed in areas with 
higher ground temperatures or operated under higher operating pressures 
will have a shorter life.
    Gas system operators may experience an increase in failure rates 
with a susceptible material. A susceptible material may have leak-free 
performance for a number of years before brittle-like cracks occur. An 
increase in the occurrence of leaks will typically be the first 
indication of a brittle-like cracking problem. It is the responsibility 
of each pipeline operator to monitor the performance of their gas 
system. RSPA issues the following recommendations to aid operators in 
identifying and managing brittle-like cracking problems in polyethylene 
piping involving taking appropriate action, including replacement, to 
mitigate any risks to public safety.
    Because systems without known susceptible materials may also 
experience brittle-like cracking problems, RSPA recommends that all 
operators implement the following practices for all polyethylene piping 
systems:
    1. Review system records to determine if any known susceptible 
materials have been installed in the system. Both engineering and 
purchasing records should be reviewed. Based on the available records, 
identify the location of the susceptible materials. More frequent 
inspection and leak surveys should be performed on systems that have 
exhibited brittle-like cracking failures of known susceptible 
materials.

[[Page 70808]]

    2. Establish a process to identify brittle-like cracking failures. 
Identification of failure types and site installation conditions can 
yield valuable information that can be used in predicting the 
performance of the system.
    3. Use a consistent record format to collect data on system 
failures. The AGA Plastic Failure Report form (Appendix F of the AGA 
Plastic Pipe Manual) provides an example of a report for the collection 
of failure data.
    4. Collect failure samples of polyethylene piping exhibiting 
brittle-like cracking. Evidence of brittle-like cracking may warrant 
laboratory testing. Although every failure may not warrant testing, 
collecting samples at the time of failure would provide the opportunity 
to conduct future testing should it be deemed necessary.
    5. Whenever possible record the print line from any piping that has 
been involved in a failure. The print line information can be used to 
identify the resin, manufacturer and year of manufacture for plastic 
piping.
    6. For systems where there is no record of the piping material, 
consider recording print line data when piping is excavated for other 
reasons. Recording the print line data can aid in establishing the type 
and extent of polyethylene piping used in the system.

(49 U.S.C. chapter 601; 49 CFR 1.53)

    Issued in Washington, DC, on November 21, 2002.
Stacey L. Gerard,
Associate Administrator for Pipeline Safety.
[FR Doc. 02-30055 Filed 11-25-02; 8:45 am]
BILLING CODE 4910-60-P