Dawn Pisturino's Blog

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Gas Pipeline Maintenance and Safety

on April 19, 2022

       The main goal of a natural gas distribution company is to deliver affordable energy to customers in a safe manner at the lowest possible cost.  Utility companies in the United States are private businesses, even though they are regulated by local, state, and federal agencies, and must make a reasonable profit in order to pay employees, finance support services, expand services, and keep the natural gas distribution system well-maintained and safe (Busby, 1997, p. 45).

       Before a pipeline is even built, it must be approved by the Federal Energy Regulatory Commission (FERC).  Companies must submit their “construction plans and economic studies that demonstrate a demand for gas in the area to be served and an available, adequate supply of gas” (Busby, 1997, p. 45).  Companies must also detail the pipeline’s environmental impact on the local surroundings.  Once the FERC approves the pipeline, it issues a certificate to the company (Busby, 1997, p. 44-45).

       The next steps are to purchase the right-of-way and lease property along the path of the pipeline.  Peculiarities in the local environment, the length of the pipeline, the local population, expected customer needs, and the projected load dictate what choices the design engineers make – gas pressure, pipe diameter, pipe wall thickness, type and spacing of compressors, and more. Computer software now exists to assist engineers to choose the right location and calculate the right specifications.  Once all this is done, the appropriate pipes, valves, and other parts and equipment are ordered (Busby, 1997, p. 45).

       Ditching machines dig deep trenches in the ground, and sections of pipe are laid out along the trench.  The sections of pipe are held in place while welders weld the lengths of steel pipe into one long pipeline.  After the pieces of pipe are welded, “the outside surface of the pipe is cleaned, coated, and wrapped to inhibit external corrosion” (Busby, 1997, p. 46).  Frequently, these pipes have been coated inside at the steel mill to prevent corrosion; to aid internal inspection of the pipe; to reduce water retention after hydrostatic testing; to reduce absorption of gas odorants; to create a friction-free surface.  After the pipe is welded, coated, and inspected, it is lowered into the trench, where it is re-covered with appropriate backfill (Busby, 1997, p. 46-47). 

       At any point along this timeline, safety issues can come up which might not become apparent until months or years later.  A faulty pipe, an inappropriate valve, a design flaw, a pipeline that is allowed to carry too much pressure, an improper weld or inappropriate backfill, may lead to a dangerous break or leak later on down the line.

       Safety is the paramount concern in pipeline operations.  “Pipelines require regular patrol, inspection, and maintenance, including internal cleaning and checking for signs of gas leaks” (Busby, 1997, p. 51-52).  A major pipeline disaster could lead to political and economic repercussions, as well as environmental pollution and threats to property and human lives (Busby, 1997, p. 51-52).

       The most common cause of pipeline damage is third-party damage, caused by contractors and other people digging too close to natural gas lines.  Any damage to the pipe, the coating, or the welded joints can cause leakage and breakage.  Most states now have requirements for contractors to determine the location of utility lines before they dig new trenches (Busby, 1997, p. 52).

       Corrosion is the second most common cause of pipeline damage. “To minimize corrosion, pipeline companies install electrical devices called cathodic protection systems, which inhibit electrochemical reactions between the pipe and surrounding materials” (Busby, 1997, p. 52).  Any kind of rust, cracking, or pitting can cause pipe breakage or leakage.  If the original coating on the pipe was defective before use, the problem may go undetected for a long time (Busby, 1997, p. 52).

       A hydrostatic test can prove whether or not a pipeline is defective or needs repairs.  The gas is removed from the pipeline and the pipe is filled with high-pressure water.  But this is an expensive procedure so pipeline operators use a device called a pig that travels through the pipeline to remove dirt and corrosion.  These materials can cause damage to the pipes, regulators, and meters.  More advanced pigs (smart pigs) use technology that can measure pipe wall thickness and other abnormalities which can indicate corrosion and other damage (Busby, 1997, p. 52-53).

       Aerial patrols of transmission lines make routine surveys that can detect signs of leakage, such as patches of yellow vegetation in areas that are normally green; construction projects that may have damaged the line; or bare pipes that need to be re-covered (Busby, 1997, p. 53).

       Leak detectors can detect gas leaks above and below the ground.  Workers can detect leaks by the presence of brown or yellow vegetation.  By digging small holes at these locations, gas leaks can be detected by visual inspection or the odor of gas.  Inline cameras are used to detect leaks inside pipelines (Busby, 1997, p. 67).

       Workers routinely survey pipelines for leaks on a set schedule.  Public buildings, such as schools, hospitals, government offices, and theaters, are given priority attention.  Serious leaks are repaired immediately.  Companies are obligated to investigate customer reports of gas odor, leaks, explosion, or fire in a reasonable amount of time, according to the severity of the leak (Busby, 1997, p. 67).  Natural gas utilities post information on their websites educating consumers on detecting and reporting natural gas leaks.

       Mains and other distribution pipes made of plastic are repaired by shutting off the gas and squeezing closed the pipe on each side of the leak.  The leaking section is replaced with new pre-tested plastic piping and appropriate connections made on each end. “Mechanical couplings are commonly used for this purpose” (U.S. Department of Transportation, 2017, p. VI-20).  Repairs must be done by qualified technicians (Busby, 1997, p. 69). 

       Leaks in steel pipes can be repaired with “leak clamp[s] applied directly over the leak” (U.S. Department of Transportation, 2017, p. VI-20).  If multiple leaks are found, the easiest way to repair the pipe is to replace it altogether with pre-tested pipe that has been coated, wrapped, and strengthened by cathodic protection.  Steel pipe can also “be replaced by inserting PE pipe manufactured according to ASTM D2513 in the existing line and making the appropriate connections at both ends” (U.S. Department of Transportation, 2017, p. VI-20).  Qualified technicians must be used to make the repairs who will use the proper connections, provide adequate support, and consider thermal expansion and contraction of the PE pipe (U.S. Department of Transportation, 2017, p. VI-20).

       Instead of repairing cast iron natural gas pipes, the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) instituted programs to identify, manage, and replace cast and wrought iron pipelines as early as 2009.  The Distribution Integrity Management Programs (DIMP) became mandatory for all U.S. pipeline operators in 2011 (U.S. Department of Transportation, 2020).

       In 2012, PHMSA urged state pipeline safety agencies to “monitor cast iron replacement programs, establish accelerated leak surveys, focus safety efforts on high-risk pipe, incentivize pipeline rehabilitation, repair and replacement programs, strengthen inspection, accident investigation, and enforcement actions, and install home methane gas alarms” (U.S. Department of Transportation, 2020).  While cast iron gas pipes can be repaired using PE or steel pipe and the appropriate connections by qualified technicians, the official recommendation is to replace these pipes altogether.

       The United States Department of Labor’s Occupational Safety and Health Administration (OSHA) is restricted by Section 4(b)(1) of the Occupational Safety and Health Act when it comes to oversight of oil and gas pipelines.  OSHA’s authority is largely limited to contractors hired by pipeline owners and operators and their workers when it comes to occupational health and safety hazards (United States Department of Labor, 2004).

       The U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) is the primary regulator of oil and gas pipelines in the United States.  The administration sponsors a Gas Distribution Integrity Management Program which requires all operators to create a Distribution Integrity Management Program (DIMP) that includes the following elements: “knowledge; identify threats; evaluate and rank risks; identify and implement measures to address risks; measure performance, monitor results, and evaluate effectiveness; periodically evaluate and improve program; report results” (U.S. Department of Transportation, 2020).

       Gas distribution systems are a necessary part of modern life.  With all stakeholders working together to achieve optimal safety, natural gas will continue to be a safe, low-cost, efficient form of energy.

References

Busby, R.L. (Ed.). (1999). Natural Gas in Nontechnical Language. Tulsa, OK: PennWell.

U.S. Department of Transportation. (2017). Guidance Manual for Operators of Small Natural

       Gas Systems. Oklahoma City, OK: U.S. Department of Transportation.

U.S. Department of Transportation. (2020). Pipeline replacement. Retrieved from

https://www.phmsa.dot.gov/data-and-statistics/pipeline-replacement/

U.S. Department of Transportation. (2020). Gas distribution integrity management. Retrieved

       From https://www.phmsa.dot.gov/technical-resources/pipeline/gas-distribution-integrity-

       management-program/

U.S. Department of Labor. (2004). Laws and regulations. Retrieved from

https://www.osha.gov/laws-regs/standardinterpretations/2004-05-28-0

Dawn Pisturino

Thomas Edison State University

December 8, 2020; April 19, 2022

Copyright 2020-2022 Dawn Pisturino. All Rights Reserved.


15 responses to “Gas Pipeline Maintenance and Safety

  1. kvbclarke says:

    Full of great detail to understand this system more and how to pay attention to our safety!

    Liked by 2 people

  2. orededrum says:

    It seems a huge industry. Thank you for this well documented post !

    Liked by 2 people

  3. Very detailed and informative indeed. Thanks for sharing, Dawn. 💖

    Liked by 2 people

  4. […] Gas Pipeline Maintenance and Safety — Dawn Pisturino’s Blog […]

    Liked by 1 person

  5. Timothy Price says:

    Another excellent and informative write up.

    Liked by 2 people

  6. elvira797mx says:

    Wow! Huge ndustry, interesting! Thank’s dear, Dawn.
    Nice day full of blessings.

    Liked by 2 people

  7. balladeer says:

    Interesting as always!

    Liked by 1 person

  8. Harshi says:

    Well researched and informative!
    “Gas distribution systems are a necessary part of modern life.” I completely agree!

    Liked by 1 person

  9. Americaoncoffee says:

    Hi Dawn! A very interesting share. I have never viewed a pipeline. I am wondering now about how environmentally safe they are, especially the Alaskan pipeline.

    Liked by 1 person

  10. […] Gas Pipeline Maintenance and Safety […]

    Liked by 1 person

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