[Federal Register: September 6, 2007 (Volume 72, Number 172)]
[Notices]
[Page 51301-51303]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr06se07-126]
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DEPARTMENT OF TRANSPORTATION
Pipeline and Hazardous Materials Safety Administration
[Docket No. PHMSA-2004-19856]
Pipeline Safety: Updated Notification of the Susceptibility to
Premature Brittle-Like Cracking of Older Plastic Pipe
AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA);
DOT.
ACTION: Notice; Issuance of Advisory Bulletin.
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SUMMARY: PHMSA is issuing this updated advisory bulletin to owners and
operators of natural gas pipeline distribution systems concerning the
susceptibility of older plastic pipe to premature brittle-like
cracking. PHMSA previously issued three advisory bulletins on this
subject: Two on March 11, 1999 and one on November 26, 2002. This
advisory bulletin expands on the information provided in the three
prior bulletins by listing two additional pipe materials with poor
performance histories relative to brittle-like cracking and by updating
pipeline owners and operators on the ongoing voluntary efforts to
collect and analyze data on plastic pipe performance. Owners and
operators of natural gas pipeline distribution systems are encouraged
to review the three previous advisory bulletins in their entirety.
FOR FURTHER INFORMATION CONTACT: Richard Sanders at (405) 954-7214, or
by e-mail at richard.sanders@dot.gov.
SUPPLEMENTARY INFORMATION:
I. National Transportation Safety Board (NTSB) Investigation
On April 23, 1998, the National Transportation Safety Board (NTSB)
issued its Special Investigation Report, Brittle-Like Cracking in
Plastic Pipe for Gas Service, NTSB/SIR-98/01. The report described the
results of the NTSB's special investigation of polyethylene gas service
pipe, which addressed three major safety issues: (1) Vulnerability of
plastic piping to premature failures due to brittle-like cracking; (2)
adequacy of available guidance relating to the installation and
protection of plastic piping connections to steel mains; and, (3)
effectiveness of performance monitoring of plastic pipeline systems to
detect unacceptable performance in piping systems.
(1) Vulnerability of plastic piping to premature failures due to
brittle-like cracking: The NTSB found that failures in polyethylene
pipe in actual service are frequently brittle-like, slit failures, not
ductile failures. It concluded the number and similarity of plastic
pipe accident and non-accident failures indicate past standards used to
rate the long-term strength of plastic pipe may have overrated the
strength and resistance to brittle-like cracking for much of the
plastic pipe manufactured and used for gas service from the 1960s
through the early 1980s. The NTSB also concluded any potential public
safety hazards from these failures are likely to be limited to
locations where stress intensification exists. The NTSB went on to
state that more durable modern plastic piping materials and better
strength testing have made the strength ratings of modern plastic
piping more reliable.
(2) Adequacy of available guidance relating to the installation and
protection of plastic piping connections to steel mains: The NTSB
concluded that gas pipeline operators had insufficient notification of
the brittle-like failure potential for plastic pipe manufactured and
used for gas service from the 1960s to the early 1980s. The NTSB also
concluded this may not have allowed companies to implement adequate
surveillance and replacement programs for older plastic piping. The
NTSB explained the Gas Research Institute (GRI) developed a significant
amount of data on older plastic pipe but the data was published in
codified terms making it insufficient for use by pipeline system
operators. The NTSB recommended that manufacturers of resin and pipe,
industry trade groups and the Federal government do more to alert
pipeline operators to the role played by stress intensification from
external forces in the premature failure of plastic pipe due to
brittle-like cracking.
(3) Effectiveness of performance monitoring of plastic pipeline
systems as a way of detecting unacceptable performance in piping
systems: The NTSB's analysis noted that Federal regulations require
pipeline operators to have an ongoing program to monitor the
performance of their pipeline systems. However, the NTSB investigation
revealed some gas pipeline operators' performance monitoring programs
did not effectively collect and analyze data to determine the extent of
possible hazards associated with plastic pipeline systems. The NTSB
pointed out, ``such a program must be adequate to detect trends as well
as to identify localized problem areas, and it must be able to relate
poor performance to specific factors such as plastic piping brands,
dates of manufacture (or installation dates), and failure conditions.''
[[Page 51302]]
Copies of this report may be obtained by searching the NTSB Web
site at http://www.ntsb.gov.
II. Advisory Bulletins Previously Issued by PHMSA
The NTSB made several recommendations to PHMSA and to trade
organizations in its 1998 special investigation report. In response,
PHMSA issued three advisory bulletins. The first advisory bulletin,
ADB-99-01, Potential Failure Due to Brittle-Like Cracking of Certain
Polyethylene Plastic Pipe Manufactured by Century Utility Products Inc,
was published in the Federal Register (FR) on March 11, 1999 (64 FR
12211) to advise natural gas pipeline distribution system operators
that brittle-like cracking may occur on certain polyethylene pipe
manufactured by Century Utility Products, Inc.
The second advisory bulletin, ADB-99-02, Potential Failures Due to
Brittle-Like Cracking of Older Plastic Pipe in Natural Gas Distribution
Systems, was also published in the Federal Register on March 11, 1999
(64 FR 12212) to advise natural gas pipeline distribution system
operators of the potential for brittle-like cracking of plastic pipes
installed between the 1960s and early 1980s.
The third advisory bulletin, ADB-02-07, Notification of the
Susceptibility To Premature Brittle-Like Cracking of Older Plastic
Pipe, was published in the Federal Register on November 26, 2002 (67 FR
70806) to reiterate to natural gas pipeline distribution system
operators the susceptibility of older plastic pipe to premature
brittle-like cracking. The older polyethylene pipe materials
specifically identified in ADB-02-07 included, but were not limited to:
Century Utility Products, Inc. products;
Low-ductile inner wall ``Aldyl A'' piping manufactured by
DuPont Company before 1973; and
Polyethylene gas pipe designated PE 3306.
This third advisory bulletin also listed several environmental,
installation and service conditions in which plastic piping is used
that could lead to premature brittle-like cracking failure. PHMSA also
described six recommended practices for polyethylene gas pipeline
system operators to aid them with identifying and managing brittle-like
cracking problems.
III. Plastic Pipe Studies
Beginning January 25, 2001, the American Gas Association (AGA)
began to collect data on in-service plastic piping material failures
with the objective of identifying trends in the performance of these
materials. The resulting leak survey data, collected from 2001 to
present, on the county's natural gas distribution systems includes both
actual failure information and negative reports (reports of no leads)
submitted voluntarily by participating pipeline operating companies.
The AGA, PHMSA, and other industry and state organizations continue
to collect and analyze the data. Unfortunately, the data cannot be
correlated with the quantities of each plastic pipe material that may
be in service across the United States. Therefore, the data does not
assess the failure rates of individual plastic pipe materials on a
linear basis (i.e. per foot, per mile, etc.). However, the failure data
reinforces what is historically known about certain older plastic
piping and components. The data also indicates the susceptibility of
additional specific materials to brittle-like cracking.
IV. Advisory Bulletin ADB-07-01
To: Owners and Operators of Natural Gas Pipeline Distribution
Systems.
Subject: Updated Notification of the Susceptibility of Older
Plastic Pipes to Premature Brittle-Like Cracking.
Advisory: All owners and operators of natural gas distribution
systems who have installed and operate plastic piping are reminded of
the phenomenon of brittle-like cracking. Brittle-like cracking refers
to crack initiation in the pipe wall not immediately resulting in a
full break followed by stable crack growth at stress levels much lower
than the stress required for yielding. This results in 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 result from geometrical
discontinuities, excessive bending, improper installation of fittings,
dents and/or 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.
All owners and operators of natural gas distribution systems are
future advised to review the three earlier advisory bulletins on this
issue. In addition to being available in the Federal Register, these
advisory bulletins are available in the docket, and on PHMSA's Web site
at http://phmsa.dot.gov/ under Pipeline Safety Regulations.
In the first advisory bulletin, ADB-99-01, published on March 11,
1999 (64 FR 12211), PHMSA advises natural gas distribution system
operators of the potential for poor resistance to brittle-like cracking
of certain polyethylene pipe manufactured by Century Utility Products,
Inc. In the second advisory bulletin, ADB-99-02, published on March 11,
1999 (64 FR 12212), PHMSA advises natural gas distribution system
operators of the potential for brittle-like cracking of plastic pipes
installed between the 1960s and early 1980s.
In the third advisory bulletin, ADB-02-07, published on November
26, 2002 (67 FR 70806), PHMSA reiterates to pipeline operators the
susceptibility of some older plastic pipe to premature brittle-like
cracking which could substantially reduce the service life of natural
gas distribution systems and to explain the mission of the Plastic Pipe
Database Committee (PPDC) ``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.'' The advisory
bulletin also lists several environmental, installation and service
conditions under which plastic piping is used which is used which could
lead to premature brittle-like cracking failure. PHMSA also describes
six recommended practices for polyethylene gas pipeline system
operators to aid them with identifying and managing brittle-like
cracking problems.
Lastly, the susceptibility of some polyethylene pipes to brittle-
like cracking is dependent on the resin, pipe processing, and service
conditions. As noted in ADB-02-07, these older polyethylene pipe
materials include, but are not limited to:
Century Utility Products, Inc. products;
Low-ductile inner wall ``Aldyl A'' piping manufactured by
DuPont Company before 1973; and
Polyethylene gas pipe designated PE 3306.
The data now supports adding the following pipe materials to this list:
Delrin insert tap tees; and,
Plexco service tee Celcon (polyacetal) caps.
Authority: 49 U.S.C. chapter 601 and 49 CFR 1.53.
[[Page 51303]]
Issued in Washington, DC, on August 28, 2007.
Jeffrey D. Wiese,
Associate Administrator for Pipeline Safety.
[FR Doc. 07-4309 Filed 9-5-07; 8:45 am]
BILLING CODE 4910-60-M