A LOOK AT THE
BRITTLE-LIKE CRACKING OF THE GAS PVC TRANSMISSION OR DISTRIBUTION PIPES THAT
CAUSED SIGNIFICANT LOSS OF LIFE AND PROPERTY DAMAGE
The exact cause of the natural gas explosion that killed eight people, injured at least 68, and displaced 100 others when it leveled two buildings in East Harlem in March hasn’t been determined, but it is known the block was serviced by a leaking 127-year-old cast iron main.
A considerable amount of degradation and some corrosion, probably from repair parts for the 1880s-era system, was visible as crews installed a new section of polyethylene pipe under the street in New York City.
In a recent blog we addressed the root
causes and contributing factors of gas pipeline failures. The link to that blog is https://sites.google.com/site/metropolitanforensics/root-causes-and-contributing-factors-of-gas-and-liquid-pipeline-failures
In the first half of the 20 century, cast and wrought iron pipe were used, which resist corrosion but can be damaged by ground settlement, freezing/thawing, and excavation. These pipelines were built to transport manufactured gas, but when they were switched to drier natural gas, pipes dried out and became brittle.
Cast iron pipe is not the only source of leakage: construction techniques of welding and joining have changed and improved over the century, but many older systems suffer from leaks due to outdated methods. However, cast iron pipe tops the list of problem pipelines.
During the 1950s and 60s, when half of the
countries pipelines were built, steel pipe became state-of-the art. However, in
early installations, steel pipe was not coated and was susceptible to corrosion.
Most people do not know that between the 1960s
through early 1980s, the oil and gas pipeline industry replaced some of the
then aging cast iron transmission or distribution pipes with plastic pipe. Then, the plastic pipe ruptures started
piling up, causing significant loss of life and extensive property damage; all
that because of the failing plastic pipe.
In 1998, as a result of these failure
events, the National Transportation safety Board (NTSB) noted that a number of
pipeline accidents it has investigated have involved plastic piping that
cracked in a brittle-like manner. In a
special investigation report (“Brittle-Like Cracking in Plastic Pipe for Gas
Service, PB98-917001, Wash., DC 20594) the NTSB concluded 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.
Failures
in polyethylene piping that occur under actual service conditions are
frequently slit failures; ductile failures are rare. Figure above shows a slit (brittle-like)
fracture in a pipe that was found leaking and had to be replaced. A rock pressing against the plastic pipe
generated long-term stress intensification that led to the formation of the
brittle-like crack. Slit failures in
polyethylene, whether occurring during stress rupture testing or under actual
service conditions, result from crack initiation and slow crack growth and are
similar to brittle cracks in other materials in that they can occur with little
or no visible deformation.
The Figure
above illustrates brittle-like cracking that was found in a plastic pipe
involved in the fatal propane gas explosion in San Juan, Puerto Rico, in November
1996. That pipe was manufactured in 1982
by E. I. du Pont de Nemours & Company, Inc., (DuPont) at its Pencador,
Delaware, plant. Apparently,
differential settlement resulting from inadequate support under the piping generated
long-term stress intensification that led to the formation of brittle-like
cracks in the pipe.
A
failed PVC pipe was blamed for a February 2009 explosion in Milwaukee that
injured two people and destroyed two buildings. A federal report said extreme cold caused the
ground to freeze to the depth of the pipe, causing the break.
As a result of that 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.
RECOMMENDATIONS OF
THE NTSB
·
Notify
pipeline system operators who have installed polyethylene gas piping extruded
by Century Utility Products, Inc., from Union Carbide Corporation DHDA 2077 Tan
resin of the piping's poor brittle-crack resistance. Require these operators to
develop a plan to closely monitor the performance of this 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.
·
Determine
the extent of the susceptibility to premature brittle-like cracking of older
plastic piping (beyond that piping marketed by Century Utility 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.
·
Immediately
notify those States and territories with gas pipeline safety programs of the
susceptibility to premature brittle-like cracking of much of the plastic piping
manufactured from the 1960s through the early 1980s and of the actions that the
Research and Special Programs Administration will require of gas system
operators to monitor and replace piping that indicates unacceptable
performance.
·
In
cooperation with the manufacturers of products used in the transportation of
gases or liquids regulated by the Office of Pipeline Safety, develop a
mechanism by which the Office of Pipeline Safety will receive copies of all
safety-related notices, bulletins, and other communications regarding any
defect, unintended deviation from design specification, or failure to meet
expected performance of any piping or piping product that is now in use or that
may be expected to be in use for the transport of hazardous materials.
·
Revise
the Guidance Manual for Operators of Small Natural Gas Systems to include more
complete guidance for the proper installation of plastic service pipe
connections to steel mains. The guidance should address pipe bending limits and
should emphasize that a protective sleeve, in order to be effective, must be of
the proper length and inner diameter for the particular connection and must be
positioned properly.
THE BEGINNING OF THE REPLACEMENT OF
THE PVC PIPES
As
a result of these recommendations, pipeline owners begun to remove the plastic
pipe. In a recent report in Wisconsin on
the safety of gas pipelines, it was stated that natural gas and propane explosions have
killed at least 135 people, injured 600 others and caused $2 billion in damage
in the United States since 2004. The 13 utilities that
operate natural gas and propane pipelines in Wisconsin reported an average of
six hazardous leaks per 1,000 miles of pipes in 2013. The national average was 35 leaks. The state also did well in unaccounted-for
gas, a leak indicator measuring gas that enters the distribution system but
doesn't reach a meter at a home or business. Wisconsin utilities averaged 0.3
percent lost gas, compared to a national average of 2.3 percent. The utilities in that state they are still
replacing the PVC pipes installed before the 1980s, with a completion date of
2017.
There are 2 million plus miles of distribution pipeline in the country. The Pipeline and Hazardous Materials Safety Administration (PHMSA) estimates that less than 3% are cast or wrought iron. Since 2004, the number of cast iron main lines decreased by 16% and service lines by 66%, replaced by plastic or steel pipelines. In 2012, however, there were still 34,000 miles of cast iron main lines and 15,000 miles of service lines.
How dangerous are deteriorating pipes? In addition to causing deaths and injuries, leaks and subsequent explosions damage property, disrupt business and power to consumers. Leaks can damage the environment and released methane is a greenhouse gas.
Reporting of actual incidents has become mandatory only recently, and accuracy is problematic because, as PHMSA states, reporting criteria “has changed both significantly and multiple times over the years.” Giving this caveat, PHMSA recorded 2604 incidents between 1994 and 2013, with 289 fatalities and 1,080 injuries.
PHMSA data in 2009 indicates that there was one leak per every 8 miles of main line and one leak per every 2 miles of service lines. Not all these leaks are attributable to faulty pipe, but PHMSA reports that 31% of incidents between 2008 and 2010 are attributable to material and/or weld failures. Cast iron pipe poses the most significant problem:
- 11% of all main line incidents involve cast iron, but it comprises only 2.6% of the lines
- 37% of iron main line incidents caused a fatality or injury, other materials caused a fatality in 21% of incidents
- 67% of iron service line incidents caused a fatality or injury, other materials caused a fatality in 32% of incidents
What has been done about this problem in the past? PHMSA reports that incidents involving death or injury have been reduced by half over the last 20 years, because of pipelines “gradually improving safety performance.” This improvement comes from better material, better construction techniques and better leak detection technology.
Why do we still have a problem with aging, deteriorating pipe? Although the technology exists to improve the entire distribution system, many challenges exist. First, operators have to know where to replace pipe, cast iron or not. PHMSA only recently began to “become a data-driven organization” for collecting data on our pipeline infrastructure and industry performance, and only recently have operators been required to report the type of material in pipelines and their history of incidents.
Second, deteriorating pipe may be difficult to replace. Unfortunately, much of the old cast iron pipe is buried in densely populated urban areas. Access is very problematic, as well as gas service disruption, traffic disruption and getting local authorities to issue permits.
Third, inspections require highly trained technical personnel. Even now, expertise and sheer manpower may be lacking, according to the NTSB and engineering experts. PHMSA does have a “Training and Qualifications” team that communicates new regulation to operators and conducts seminars, but more technical assistance is needed and companies must satisfy the operator qualification rules.
Because of the difficulties involved, the cost to accomplish replacement is in the billions of dollars. This is money that most companies may not have, and probably will not have because of the current approach to rate-making at both the Federal and State level.
As reported by PHMSA in 2011, many States have mandated pipeline replacement programs for some types of older pipes. Some states have incentivized operators to replace cast iron pipe by providing operators with rate relief to accelerate replacement. However, some of these replacement programs in the larger states are not scheduled for completion for many decades.
In fact, The PHMSA reports that the ten states that have 80% of the cast iron main lines in the country, have extremely long-term, if any, replacement goals:
·
Alabama
2040
·
Connecticut
2080
·
Illinois
2031
·
Maryland
No program
·
Massachusetts
No timeline
·
Michigan
2040
·
Missouri
2059
·
New
Jersey 2035
·
New
York 2090
·
Pennsylvania
2111
These programs must be accelerated if more deaths, injuries and property damage are to be avoided. PE is the plastic replacement material of choice for modernizing the natural gas distribution system — so much so some are concerned about resin and pipe shortages. However, Performance Pipe expects the plastics industry to keep up with demand. Our concern though is with quality of the pipe, considering the significant demand and the rush to meet it.
Demand for next-generation plastics, like PE pipe, started rising in 2009 and really picked up in 2011. That’s when the federal government required natural gas utility operators to have a distribution integrity management plan (DIMP) in place to address the highest risk segments of their systems. There’s still roughly 30,000 miles of cast iron in the ground in distribution, but 10 years ago there were 40,000 miles so it is being replaced over time.
Plastic pipe has several advantages over steel pipe; however, plastic is more susceptible to damage from digging, static electricity and it requires the use of tracer wire to locate during excavations. Bar codes are gaining traction.
New Jersey Gas Pipeline Problem
New Jersey’s aging gas mains last year had twice the number of hazardous leaks than the nation’s gas mains on the whole. Faced with alarms raised by federal authorities over the safety of old pipes, the four gas utilities operating in New Jersey are working to replace older stocks of bare-metal or coated but unprotected mains with plastic or steel pipes that have protective coating. North Jersey-based Elizabethtown Gas Co. has the state’s highest leak rate: 97.3 hazardous leaks per 1,000 miles of mains.
New Jersey has 5,000 miles of the type of gas mains that raise the most concern for safety: cast iron. About 17 percent of New Jersey’s 34,000 miles of gas mains were made up of cast iron or bare steel at the end of 2013 — or 6,437 miles. The national average is 7 percent.
Between 2007 and 2013 in New Jersey, cast-iron mains have been reduced by 717 miles and bare-steel mains by 574 miles, according to the BPU.
That dropped the miles of bare-metal mains over that six-year period by about 3.3 percent a year. If the pace continues, the old mains would be replaced in 30 years.
And in the six-year period, 101,376 bare-steel service lines have been replaced with new pipe. At the end of 2013, there were about 270,000 bare-steel service lines — those that run from gas mains to customers’ buildings. If that rate of replacement continues, it would take about 16 years to switch them all. There are no cast-iron service lines.
The most common way of causing gas explosion is through pipe rupture by excavating machines or drilling rigs, just like what happened in March 2014 in Ewing, New Jersey. A contractor doing electrical repair work at the scene is believed to have damaged a gas line, which sparked the blast. The explosion destroyed at least 20 townhouses and caused over $10M in damages, including one dead person.
The contractor hired by PSE&G — Henkels & McCoy — has been the subject of more than 130 incident investigations over the past decade, and OSHA fined them $221,000 for 29 violations in New Jersey, but PSE&G is praising the work they’ve done. During a news conference at Ewing Police Headquarters, Mike Gaffney, the director of Gas Distribution for PSE&G, said what happened is an incredible tragedy, but he insists that the contractor was qualified and has a good history. However, typically PSE&G would hire the low bidder, who in turn would use inexperienced or improperly trained personnel to do the work and be able to turn profit at the same time. Pretty much the same thing that has been happening with Verizon and the cell tower maintenance subcontractors. These brave subs have been falling like ripe grapes to their death during the last two years or so.
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