PIPELINE REPLACEMENT UPDATES FROM THE UNITED STATES PHMSA
PIPELINE REPLACEMENT UPDATES FROM THE UNITED STATES PHMSA
Background
Aging pipelines
In January 2012, President Obama signed the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011, which examines and improves existing pipeline safety regulations and provides the regulatory certainty necessary for pipeline owners and operators to plan infrastructure investments and create jobs.
Pipeline transportation is one of the safest and most cost-effective ways to transport natural gas and hazardous liquid products. As America continues to develop and place more demands on energy transportation, it becomes more necessary to invest in upgrading its infrastructure, including aging pipelines. To follow State's progress in pipeline infrastructure upgrades, or to obtain contact information and incident and mileage data, visit PHMSA’s state pipeline profiles.
In 2011, following major tragic natural gas incidents, DOT and PHMSA issued a Call to Action to accelerate the repair, rehabilitation, and replacement of the highest-risk pipeline infrastructure. Among other factors, pipeline age and material are significant risk indicators. Pipelines constructed of cast and wrought iron, as well as bare steel, are among those that pose the highest-risk.
Reports
To illustrate the progress pipeline operators are making in the replacement of aging gas pipelines, PHMSA provides an annually-updated online inventory of high-risk pipeline infrastructure by state. Specifically, the dynamic inventory highlights efforts to replace iron and bare steel gas distribution pipelines. and shows trends in pipeline miles by decade of installation.
About Cast and Wrought Iron Pipelines
Cast and wrought iron pipelines are among the oldest energy pipelines constructed in the United States. Many of these pipelines were installed over 60 years ago and still deliver natural gas to homes and businesses today. However, the degrading nature of iron alloys, the age of the pipelines, and pipe joints design have greatly increased the risk involved with continued use of such pipelines.
The Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 calls for DOT to conduct a state-by-state survey on the progress of cast iron pipeline replacement. For updates on the states’ progress, contact information and incident and mileage data, the public should visit PHMSA’s state pipeline profiles.
The amount of cast and wrought iron pipeline in use has declined significantly in recent years, thanks to increased state and federal safety initiatives and pipeline operators’ replacement efforts.
Sixteen states have completely eliminated cast or wrought iron natural gas distribution lines within their borders, Alaska, Arizona, Hawaii, Idaho, Montana, North Carolina, North Dakota, New Mexico, Nevada, Oklahoma, Oregon, South Carolina, Utah, Vermont, Wisconsin, and Wyoming.
Approximately 97 percent of natural gas distribution pipelines in the U.S. were made of plastic or steel at the end of 2012. The remaining 3 percent is mostly iron pipe.
About Bare Steel Pipelines
Uncoated steel pipelines are known as bare steel pipelines and while many of these pipelines have been taken out of service, some of these pipelines are still operating today. The age and lack of protective coating typically makes bare steel pipelines of higher risk as compared to some other pipelines and candidates for accelerated replacement programs.
About Decade Installed
From the early 1900’s through today, the integrity of energy pipelines have all benefited from improvements in pipe manufacturing, pipe materials, construction methods, and maintenance practices.
Recent Incidents Involving Cast Iron Pipelines
Even though the amount of cast iron pipelines is declining, there have been a number of recent incidents caused by cast iron gas distribution main failures, resurging attention to the risks associated with cast and wrought iron pipelines.
January 9, 2012 – A home exploded on Payne Ave in Austin, Texas, resulting in one fatality and one injury. The leak originated at a break in a four-inch cast iron gas main installed in 1950. The cast iron main break occurred after rainfall that followed extended drought conditions.
February 9, 2011 – A tragic explosion occurred on North 13th Street in Allentown, Pa. Local emergency responders worked to limit the spread of the fire while the operator cut through reinforced concrete to access the gas main. A preliminary investigation found a crack in a 12-inch cast iron main that was installed in 1928 and was operating at less than 1 psig at the time of incident. As a result of the explosion and ensuing fire, five people lost their lives, three people required in-patient hospitalization, and eight homes were destroyed.
January 18, 2011 – An explosion and fire caused the death of one gas utility employee and injuries to several others while gas utility crews were responding to a natural gas leak in Philadelphia, Pa. A preliminary investigation found a circumferential break on a 12-inch cast iron distribution main that was installed in 1942 and was operating at 17 psig.
Incident and Consequence Analysis
PHMSA regulations require gas distribution operators to submit incident reports when a leak causes an injury or fatality, property damage in excess of $50,000, or the unintentional release of more than three million standard cubic feet of gas. Gas distribution incident reports (excluding those caused by leaks beyond the customer meter) for 2005 through 2013 show the following:
10.5 percent of the incidents occurring on gas distribution mains involved cast iron mains. However, only 2.5 percent of distribution mains are cast iron.
In proportion to overall cast iron main mileage, the frequency of incidents on mains made of cast iron is more than four times that of mains made of other materials.
38 percent of the cast/wrought iron main incidents caused a fatality or injury, compared to only 20 percent of the incidents on other types of mains.
12 percent of all fatalities and 8 percent of all injuries on gas distribution facilities involved cast or wrought iron pipelines.
What Causes Iron Pipe Leaks?
The biggest threat to cast or wrought iron pipe is earth movement. If these pipelines are disturbed by digging, seasonal frost heave, or changes in ground water levels, leakage may occur.
Another serious threat called graphitization is a natural process in which iron degrades to softer elements, making iron pipelines more susceptible to cracking. The extent of graphitization depends on many factors, but gas may leak from the joints or through cracks in the pipe if graphitization has occurred.
When leaks occur on low-pressure systems with cast or wrought iron distribution lines, the volume of gas escaping through the failure point is much less than what might escape through the same size failure in a system operating at higher pressures. However, even a relatively small volume of natural gas leakage can have catastrophic consequences.
History
Cast and wrought iron pipelines were originally constructed to transport manufactured gas beginning in the 1870s and 1880s, with cast iron becoming more popular in the early 1900s.
In 1970 PHMSA began collecting data about gas pipelines mileage categorized by pipe material type. In 1983, gas distribution pipeline operators reported 61,536 miles of cast iron and 4,371 miles of wrought iron pipe. Operators began submitting merged data for the two beginning in 1984.
Wrought iron pipelines were joined end-to-end using either threaded or compression couplings, while cast iron pipelines were linked using bell and spigot joints with packing material stuffed in the bell to form a gas tight seal. Since these pipelines transported wet, manufactured gas, the packing material absorbed moisture and generally did not leak.
As dry, natural gas began supplanting manufactured gas use in the mid-20th century, the packing material sealing the joints dried out, causing leaks. A variety of clamping and encapsulation techniques have been implemented over the years to repair the joints.
Distribution Integrity Management Programs
In late 2009, PHMSA implemented pipeline safety regulations for managing the integrity of gas distribution pipelines. Operators were required to create and implement Distribution Integrity Management Programs (DIMP) by August 2011. Operators are required to know the specific characteristics of their system and operating environment to identify threats, evaluate the risk, and take measures to reduce the risk.
Specifically for cast/wrought iron, operators must have knowledge of the specific characteristics of the pipe and environments where graphitization could be severe. Evaluating past leak history and monitoring cast/wrought iron pipe during excavations are also key components of maintaining integrity.
National Transportation Safety Board Recommendations
The National Transportation Safety Board is an independent federal agency that conducts investigations to determine the probable causes of transportation accidents.
In 1986, the NTSB investigated an explosion at a restaurant in Derby, Conn., that killed six people and injured 12. The NTSB issued recommendations for corrective action only to the pipeline operator. In 1990, a natural gas explosion and fire killed one person, injured nine, destroyed two homes, and damaged two adjacent houses in Allentown, Pa. The NTSB report found that a water main leak eroded support under a 4-inch cast iron gas main. This ground disturbance results in a circumferential crack in the gas main. Natural gas migrated through the soil and into the basement of one of the homes where it ignited, exploded, and burned. The cast iron gas main was significantly weakened by graphitization.
In 1991, the NTSB recommended that PHMSA – then called the Research and Special Projects Agency – require pipeline operators to implement a program to identify and replace cast iron pipelines that may threaten public safety. PHMSA issued two Advisory Bulletins related to cast iron replacement programs.
RSPA Alert Notice 91-02 Encourages operators to develop procedures to identify segments of cast iron pipe that may need replacement. Reminds operators that pipeline safety regulations require generally graphitized cast iron pipe to be replaced and protect excavated cast iron pipe from damage.
RSPA Alert Notice 92-02 Reminds operators that pipeline safety regulations require operators to have a procedure for continuing surveillance of pipeline facilities to identify problems and take appropriate action concerning failures, leakage history, corrosion, and other unusual operating and maintenance conditions. This procedure should also include surveillance of cast iron to identify problems and take appropriate action concerning graphitization.
Cast and Wrought Iron Inventory
Reports
The inventory opens in a new window and contains three reports about each state with cast or wrought iron pipe.
In the first report , you can rank states by either gas distribution main miles or service line counts. Distribution mains are natural gas distribution pipelines that serve as a common source of supply for more than one service line. Service lines are the pipelines that transport gas to a customer’s meter or piping. The table is initially sorted by the number of miles of cast or wrought iron gas distribution main, but can be sorted by any of the columns.
The second report shows the change in main miles and service line counts over the years. Nationally, iron distribution main mileage has decreased by nearly 24 percent from 2004 to 2013 . The number of cast or wrought iron service lines has decreased by nearly 73 percent over the same time period. The third report shows data for each operator reporting iron pipelines since 2004.
All of the reports can be limited to a single state by using the state prompt at the top. Any state not included in the drop-down either never had cast and wrought gas distribution pipelines or all were removed before 2004.
Iron Gas Distribution Pipeline Inventory Reports
Bare Steel Inventory
Reports
The inventory opens in a new window and contains three reports about each state with bare steel pipe.
In the first report, you can rank states by either gas distribution main miles or service line counts. Distribution mains are natural gas distribution pipelines that serve as a common source of supply for more than one service line. Service lines are the pipelines that transport gas to a customer’s meter or piping. The table is initially sorted by the number of miles of bare steel gas distribution main, but can be sorted by any of the columns.
The second report shows the change in main miles and service line counts over the years. Nationally, bare steel gas distribution main mileage has decreased by nearly 24 percent from 2004 to 2013 . The number of bare steel service lines has decreased by nearly 49 percent over the same time period. The third report shows data for each gas distribution operator reporting bare steel pipelines since 2004.
All of the reports can be limited to a single state by using the state prompt at the top. Any state not included in the drop-down either never had bare steel gas distribution pipelines or all were removed before 2004.
Bare Steel Gas Distribution Pipeline Inventory Reports
Background and History
Uncoated steel pipelines are known as bare steel pipelines. While many of these pipelines have been taken out of service, some of these pipelines are still operating safely today. The age and lack of protective coating typically makes bare steel pipelines candidates for accelerated replacement programs.
The lack of protective coating on these lines requires a high level of cathodic protection current for corrosion protection of the pipeline. Surveys used to determine the effectiveness of cathodic protection on bare steel pipelines focus on identifying larger corrosion cells called “hot spots,” However, small, localized corrosion areas are difficult to identify and can lead to integrity issues.
Bare steel pipe was used extensively in distribution pipelines until the 1960’s, when the availability of plastic pipelines had expanded to natural gas distribution systems. Until pipeline coatings were required with the establishment of federal mandates in 1971, some transmission and distribution operators, continued to install pipelines without coatings, particularly in dry areas of the country.
Distribution Integrity Management Programs
Pipeline integrity, refers to a system that is in sound, unimpaired condition that can safely carry out its function under the conditions and parameters for which it was designed. An integrity management program is a documented set of policies, processes, and procedures that are implemented to ensure the integrity of a pipeline.
Cathodic protection is a method of protecting metallic pipelines from corrosion. Applied cathodic protection and external coating are important components of the pipeline corrosion protection system.
Assessing the integrity of bare steel pipelines is more difficult than for other coated pipelines as the assessment methodology employed must be closely monitored. Magnetic flux leakage is most commonly used to identify areas of metal loss. Corrosion that may exist along bare steel lines could mask some of the magnetic leakage, and cause measurement inaccuracy regarding the depth of metal loss. Inspection tools that make direct measurements, such as ultrasonic metal loss tools, will give better results on bare steel lines. Bare steel pipelines are also difficult to inspect with external corrosion direct assessment (ECDA) because many ECDA tools rely on indications of coating faults or coating conditions which are not applicable to uncoated pipelines.
Bare steel pipelines are a focus for many pipeline replacement and rehabilitation programs that are planned or in place across the country. In areas where pipe replacement by excavation is too cumbersome, bare steel pipe may be inserted with new plastic pipe. In addition to cathodic protection surveys that identify areas of active corrosion and interference currents, leak detection surveys utilized at an increased frequency beyond minimum federal requirements can identify leaks early as well.
By-Decade Inventory
Reports
The inventory opens in a new window and contains four tabs with information about miles of pipeline by decade of installation. The first three tabs contain reports for gas distribution, gas transmission, and hazardous liquid pipelines.
The first report on these tabs, shows how the number of miles installed in each decade has changed since 2005. One bar chart shows the decades before 1970 and a separate chart shows decades after 1970. The first report also includes a table of the data. In the second report, you can select a single decade and see the trend line since 2005. For gas distribution, you can choose to see data for mains or services. For hazardous liquid, you can select one or more commodities.
The national reduction in pre-1970 pipelines in 2013 compared to 2005 is:
The last tab includes two reports ranking states by miles of pre-1970 pipelines. The first report is for gas pipelines and the second report is for hazardous liquid. The reports can be sorted by any of the columns.
Miles by Decade of Installation Inventory Reports
Pipeline Practices over the Decades
From the early 1900’s through today gas transmission, hazardous liquid and gas distribution pipelines have all benefited through each decade from improvements in pipe manufacturing, construction, and operational and maintenance (O&M) practices.
Pipe Manufacturing Process included improvements in steel metallurgy, seam welding techniques, seam non-destructive testing, pipe rolling practices, and quality control through pressure testing and inspection before the pipe leaves the mill.
Lap welded, hammer welded, low frequency electric resistance (LF-ERW) and flash welded (FW) pipe were all used starting in the early 1900’s. Pipes manufactured during the post-World War II construction boom that lasted well into the 1960’s were vulnerable to seam quality issues. Since the late 1960’s and early 1970’s, these seam types are no longer manufactured or installed by pipeline operators. They have been replaced with high frequency (HF) ERW pipe, submerged arc welded (SAW) or seamless pipe, which all have improved steel and seam properties.
Current manufacturing processes include improved steel rolling practices, non-destructive seam inspection, and pressure testing of the pipe before it leaves the mill.
Since the late 1960’s, the use of plastic pipe in gas distribution pipelines has steadily increased. Some vintages installed between the 1960s and early 1980s have the potential for brittle-like cracking. The susceptibility is dependent on the resin, pipe processing, and service conditions.
Construction practice improvements have been in field girth welding and non-destructive testing (NDT), pipe coating, pipe bending, use of select backfill, in-place hydrostatic pressure testing and inspection.
Construction practices beginning in the early 1900’s included the use of wrinkle bends, threaded collars, oxy-acetylene welding, backing rings for welding, and non-coated pipe. Beginning in the 1930’s and 1940’s improved girth welds using shielded metal arc welding (SMAW) , pipe bending practices, usage of pipe coating, and girth weld non-destructive inspection were beginning to be used by most pipeline operators. The need for pipeline non-destructive testing (NDT) grew very rapidly with the increase of offshore gas and oil exploration in the 1970s.
O&M practice improvement have included usage of cathodic protection for external corrosion mitigation, programs for internal corrosion such as operational pigging and inhibitor injection programs, integrity management assessments, smart pigging, remediation of defects found, and right-of-way monitoring that includes one-call programs.
O&M practices in the early 1900’s through the early 1950’s by some pipeline operators did not include designs for operational pigging, usage of cathodic protection, and sometimes pipe external coatings. Beginning in the 1950’s usage of full opening valves for pigging, cathodic protection, and external pipe coatings were being used by most pipeline operators. The first smart pig was developed in the 1960s using Magnetic Flux Leakage (MFL) technology to inspect the bottom portion of the pipeline. Development of both pipeline pigs for electromagnetic and ultrasonic detection of wall thinning, and X-ray crawlers for weld inspection in long runs of pipe occurred during the 1970s. Pigs and crawlers were the only means of inspecting for erosion, corrosion (internal and external) and other types of defect in buried pipes. Operator Qualification (OQ) regulation was implemented in 1999 to require that maintenance personnel performing the work on the pipeline were qualified. A critical improvement to O&M practices was integrity management program requirements to assess the condition of pipelines and remediate defects that compromised pipeline safety. Learn more about integrity management assessment techniques:
In-Line Inspections (Smart Pigs)
Direct Assessment (DA) - Gas Pipelines
Direct Assessment (DA) - Hazardous Liquid Pipelines
Overall improvements in pipe manufacturing, construction, and O&M practices have been an integral part of the pipeline industry efforts to reduce risk and improve public safety from incidents beginning in the 1900’s through today. The Gas Code (Part 192) was implemented in 1970 and the Hazardous Liquid Code (Part 195) was implemented in 1979. Their basis was in the technical standard ASME B31.8. Many states had already adopted ASME B31.8 prior to the federal gas codes. The implementation of these codes has been an integral part in further reducing risks and improving safety through consistent regulations and standards for all pipeline operators.
Pipelines constructed before adoption of federal safety rules in 1970 were allowed a grandfathering exemption for establishing maximum allowable operating pressure (MAOP). This allowed natural gas transmission lines installed before July 1, 1970 to be operated in some cases without having been: pressure tested in the field, higher MAOPs than allowed for new pipelines constructed after implementation of the regulations, and without material records. Hydrostatic pressure testing can identify latent manufacturing and construction defects.
Eliminating or limiting the grandfather clause could have a significant impact on industry because about 50% of onshore natural gas transmission lines were constructed before 1970.
PHMSA held public a workshop, The Integrity Verification Process, which included discussion of possible removal of parts of the grandfather clause, remediation of pipe with seam integrity issues, and material documentation.