[Federal Register Volume 73, Number 43 (Tuesday, March 4, 2008)]
[Pages 11695-11697]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-4155]



Pipeline and Hazardous Materials Safety Administration

[Docket No. PHMSA-RSPA-2004-19856]

Pipeline Safety: Issues Related to Mechanical Couplings Used in 
Natural Gas Distribution Systems

AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), 

ACTION: Notice; issuance of advisory bulletin.


SUMMARY: Recent events concerning failures of mechanical couplings and 
related appurtenances have raised concerns about safety in natural gas 
distribution systems. This notice updates information provided in 
Advisory Bulletin ADB-86-02 and advises owners and operators of gas 
pipelines to consider the potential failure modes for mechanical 
couplings used for joining and pressure sealing two pipes together. 
Failures can occur when there is inadequate restraint for the potential 
stresses on the two pipes, when the couplings are incorrectly installed 
or supported, or when the coupling components such as elastomers 
degrade over time. In addition, inadequate leak surveys which fail to 
identify leaks requiring immediate repair can lead to more serious 
incidents. This notice urges operators to review their procedures for 
using mechanical couplings and ensure coupling design, installation 
procedures, leak survey procedures, and personnel qualifications meet 
Federal requirements. Operators should work with Federal and State 
pipeline safety representatives, manufacturers, and industry partners 
to determine how best to resolve potential issues in their respective 
state or region. Documented repair or replacement programs may prove 
beneficial to all stakeholders involved.

FOR FURTHER INFORMATION CONTACT: Richard Sanders at (405) 954-7214, or 
by e-mail at [email protected]; or Max Kieba at (202) 493-0595, 
or by e-mail at [email protected].


[[Page 11696]]

I. Background

    Mechanical couplings are fittings used for joining and pressure 
sealing two pipes together. Other methods of joining pipe include 
welding for steel and heat fusion for plastic. There have been 
improvements in materials and manufacturing methods over the years, but 
the basic design concept has not changed. Most couplings rely on 
elastomers and compression as sealing mechanisms. Couplings appear in a 
variety of configurations: Straight or inline couplings, elbows (45 or 
90 degree), tees, reducing couplings (for joining pipes of different 
diameters), and couplings integrated with risers. A variety of gaskets 
and sleeves also exist. Properly installed and supported, couplings 
successfully connect steel, cast iron, copper, and plastic pipes. 
However, there is also a history of significant incidents related to 
coupling failures.
    Advisory Bulletin ADB-86-02, issued February 26, 1986, informed 
natural gas pipeline operators to review procedures for using 
mechanical couplings and ensure coupling design, procedures, and 
personnel qualifications meet 49 CFR part 192 requirements. ADB-86-02 
is posted on PHMSA's Web site and in Docket ID PHMSA-RSPA-2004-19856. 
The bulletin discussed pipeline failures that had been attributed to 
temperature-related contraction of the plastic pipe and the inadequate 
restraint capabilities of mechanical couplings.
    Additionally, the National Transportation Safety Board (NTSB) 
issued a Pipeline Accident Report titled ``National Fuel Gas Company, 
Natural Gas Explosion and Fire, Sharpsville, Pennsylvania, February 22, 
1985'' (NTSB/PAR-85/02). The factors involved in the Sharpsville 
incident were similar to those of several other incidents reported to 
PHMSA's Office of Pipeline Safety. As documented in the NTSB report, 
the cyclic effects of temperature-related contraction and expansion on 
plastic pipe in an improperly designed mechanical joint can be 
cumulative and lead to a failure even after several years of 
satisfactory service.
    A number of incidents have occurred since issuance of ADB-86-02. 
PHMSA searched 3,417 gas distribution incident reports submitted to the 
agency since 1984, and identified 274 incidents that could potentially 
include coupling or fitting failures. After closer examination of the 
incident detail, PHMSA determined 148 of those incidents more reliably 
appear to be coupling or fitting failures on steel or plastic pipe. 
Although this accounts for only four to eight percent of all 
distribution incidents reported to PHMSA, the significant incidents 
within that data, as well as the potential for additional significant 
incidents, should not be ignored. Significant incidents include the 
following: a failure in Buffalo, Minnesota on February 19, 2004 that 
resulted in significant property damage; a failure in Ramsey, Minnesota 
on December 28, 2004 that resulted in three fatalities and one serious 
injury; and, a failure in Wylie, Texas on October 16, 2006 that 
resulted in two fatalities.
    It is important to note that this data only includes incidents that 
were reportable to PHMSA. These numbers could be much greater if they 
included incidents that were reported at the State level.
    In addition to these incidents, a number of other issues have been 
     In 1993, the New York State Public Service Commission (NY 
PSC) concluded an investigation concerning the increased incidence of 
leaks attributed to gaskets and gas quality in a coupled steel natural 
gas distribution system on Long Island.
     In 2005, Washington Gas Company issued a report on the 
increased incidence of natural gas leaks attributed to gaskets and gas 
quality on mechanically coupled steel pipe in a major portion of its 
distribution system.
     In 2005, the Public Utilities Commission of Ohio (PUCO) 
opened a statewide investigation due to a series of natural gas 
incidents reported to PUCO by local distribution companies involving 
risers, the vertical portions of the service lines that connect the 
distribution systems to customers' meters. In addition to four 
reportable incidents, a number of ``non-incident'' riser failures were 
also reported to the staff. The PUCO opened a case to examine riser 
types, reviewing installation and overall performance because of the 
potential risk posed by risers as links between the gas distribution 
service lines and meters, located near or within a customer's premises.
     In addition to the 2004 incidents in Minnesota already 
discussed, two other incidents occurred in the State. After the first 
incident, Minnesota's Office of Pipeline Safety began to review the 
couplings installed in the system in question. The second incident 
occurred while the study was being conducted.
    Between 1980 and 2007, seven incidents occurred in Texas. These are 
outlined in a February 2008 Railroad Commission of Texas report titled 
``Study Report on Compression Type Couplings.'' (http://www.rrc.state.tx.us/divisions/gs/pls/TXcouplingrpt.pdf)
    These incidents involve a variety of types and sections of 
couplings or risers. For example, the issues surrounding the Ohio 
couplings were slightly different than the Texas couplings. Both were 
related to risers, but the Ohio issues involved the compression 
mechanisms located aboveground on the risers that connect meter 
settings to underground service lines. The couplings in Texas have been 
located on the ends of service risers where service lines connect to 
risers. While some incidents in question were reportable to PHMSA and 
investigated by PHMSA, those that were not were investigated by the 
relevant State pipeline safety agency. This notice does not focus on a 
particular State, operator, or type of coupling. Rather, it intends to 
provide generally applicable advice on incidents affecting multiple 
stakeholders and systems throughout the country.
    Although a number of variables exist, the safety problem appears to 
involve two predominant failure modes. First, in the cases involving 
pullout of pipe, often plastic, from compression couplings, an 
additional and perhaps unique factor produced the pullout forces. These 
additional factors could include cyclic fatigue from changing of the 
seasons (especially in northern climates), or soil shifting by other 
means (ground movement from earthquakes or after heavy rains). Improper 
installation (most couplings currently come with product warnings) or 
old age (parts of the coupling deteriorating) could also have 
contributed to the pullout. Some studies found couplings that were 
installed with components that differed from the original manufacturer 
specifications, modified prior to installation, or missing parts 
entirely. As another example of incorrect application, the coupling 
involved in the Ramsey, Minnesota incident was designed to be used on 
steel pipe, not plastic, and had a service tee welded to it contrary to 
manufacturer's recommendations. The common factor in all incidents 
involving pullout is that the compression fitting did not have adequate 
restraint to assure safety under service conditions. In some cases, the 
coupling failed after many years of successful service.
    The second failure mode involves leakage through the sealing 
surface between the coupling and the pipe. This occurred when the 
integrity of long-term viscous and elastic effects of the seals 
degraded which eventually caused a leak path to develop. In some cases, 
a change in the gas quality in the distribution system may have 
contributed to the failure.

[[Page 11697]]

    Other contributing factors can also lead to incidents. These 
factors include leak surveys conducted in conditions that prevent gas 
from properly migrating to the surface, such as after heavy rains or 
certain soil and surface features. Some incidents indicated leak 
surveys involving equipment not calibrated properly or not appropriate 
for the intended use, or personnel not sufficiently trained. If an 
operator is doing proper leak surveys at regular intervals, an operator 
can usually detect a leak early, fix the source of the leak, and 
prevent an incident. There have, however, been cases where a leak 
survey, using properly calibrated equipment showing no problems, was 
followed by an incident involving sudden pullout only weeks later.
    Follow-up has already occurred with some of the incidents mentioned 
in this bulletin:
     The NY PSC and the operator agreed to a replacement 
program involving approximately 45,000 natural gas service lines 
equipped with couplings.
     In Ohio, nearly 500,000 risers were identified by the 
PUCO's study as prone to failure. Currently, the PUCO is working with 
the operators who have these risers and the Ohio Consumers' Counsel to 
set up replacement schedules and address costs.
     In May 2005, Minnesota's Office of Pipeline Safety issued 
a compliance order to an operator to replace service lines installed 
prior to January 1, 1984, or visually inspect the entire service line 
to verify it contains only mechanical fittings that comply with 49 CFR 
192.283(b). Any mechanical fittings identified that did not meet the 
requirements were required to be replaced.
     The Railroad Commission of Texas has required operators to 
replace, within a 2-year period, 97,000 remaining old mechanical 
couplings that have been in service for some 28 to 30 years. In 
addition, the Railroad Commission of Texas has adopted mandatory 
replacement programs in an effort to remove compression couplings found 
leaking on both steel and plastic pipe that are susceptible to pullout.
    A number of other studies, tests, and repair or replacement 
programs, some of them voluntary, have been conducted in other States.

II. Advisory Bulletin (ADB-08-02)

    To: All Gas Distribution Operators.
    Subject: Identifying Issues with Mechanical Coupling That Could 
Lead to Failure.
    Advisory: Due to variables related to age of couplings, specific 
procedures and installation practices, and conditions specific to 
certain regions of the country, it is difficult to cite common criteria 
affecting all failures that operators should address. However, PHMSA 
advises operators of gas distribution pipelines using mechanical 
couplings to do the following to ensure compliance with 49 CFR part 
    (1) Review procedures for using mechanical couplings, including the 
coupling design and installation and ensure that they meet 
manufacturer's recommendations;
    (2) Review leak survey procedures to ensure that leak surveys are 
properly conducted, taking into account other contributing factors 
(i.e., weather conditions, calibration); and,
    (3) Review personnel qualifications to ensure they address leak 
surveys sufficiently.
    PHMSA also advises operators of gas distribution pipelines using 
mechanical couplings to consider taking the following measures to 
reduce the risk of failures of mechanical couplings:
    (4) Use Category 1 fittings only if mechanical couplings are used 
on pipe sizes \1/2\' CTS (Copper Tube Size) to 2' IPS (Iron Pipe Size). 
Per ASTM D2513-99 titled ``Standard Specification for Thermoplastic Gas 
Pressure Pipe, Tubing and Fittings,'' Category 1 is a mechanical joint 
design that provides a seal plus a resistance to a force on the pipe 
end equal to or greater than that which will cause a permanent 
deformation of the pipe. At this time there is insufficient data to 
indicate there are issues involving fittings for larger diameter pipe. 
PHMSA will revisit if such issues do arise with larger diameter pipe.
    (5) Improve recordkeeping on specific couplings that exist, i.e., 
their type, installation date, maintenance schedule, and any failures 
encountered, to help identify a trend of problems that may occur with a 
specific coupling or type of installation.
    (6) Consider whether to adopt a full replacement program if there 
are too many unknowns related to couplings in service.
    (7) Work with Federal and State pipeline safety representatives, 
manufacturers, and industry partners to determine how best to resolve 
potential issues in their respective state or region.
    Documented repair and replacement programs may prove beneficial to 
all stakeholders involved. If operators are unsure of the appropriate 
representative, contact the individual(s) listed in this advisory 
bulletin for further information.

    Issued in Washington, DC, on February 28, 2008.
Jeffrey D. Wiese,
Associate Administrator for Pipeline Safety.
[FR Doc. E8-4155 Filed 3-3-08; 8:45 am]