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Natural Gas: Industry Continues to Strengthen Gas Pipeline Safety Regulations

by Bob Shively, Enerdynamics President and Lead Instructor

“Safety is cited as the No. 1 concern among all sectors of the natural gas industry”[1]

As we have often discussed in Energy Currents blog posts over the last two years, safety of natural gas pipelines and storage fields has become a critical issue for the industry. Significant recent incidents have exposed the risks associated with aging infrastructure and traditional operating procedures.

In response to congressional mandates and various industry safety recommendations, the federal agency responsible for regulating pipeline safety (the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration, commonly called PHMSA) recently proposed a new natural gas transmission rule.

Principles of Pipeline Safety

Before discussing the changes proposed in the new rule, let’s review some principles associated with gas pipeline safety. Key components in the gas delivery system that impact safety include:

  • the pipe that holds the gas;
  • valves that control flow of gas;
  • and compressors and regulators that control gas pressure.

 


        Above graphic is available for download at http://www.enerdynamics.com/resources.asp

 

Pipeline incidents are caused by various factors. Design of the system and emergency response procedures impact the significance of an incident once it occurs. Key factors that cause pipeline incidents are:

 

  • External damage from dig-ins or natural forces
  • External corrosion
  • Improper pipe manufacture or field construction
  • Exceeding pressure limit due to equipment failure or operator error

The ability of a pipe to hold gas without leaking is called pipeline integrity. It is impacted by pipe manufacturing, pipeline design and construction techniques, pipeline maintenance and pipeline operations. To avoid leaks, pipe must resist stresses including internal stress from the pressure of the gas and external stress from natural and man-made forces.

Graphic is from the Enerdynamics Gas System Fundamentals seminar, for details see http://www.enerdynamics.com/Gas-Industry/Gas-System-Fundamentals-Seminar.asp

A key factor for ensuring pipeline safety is the Maximum Allowable Operating Pressure (MAOP). MAOP is the highest pressure that a pipe should ever withstand to avoid the risk of causing a pipe rupture. It is determined by pipe strength, the manufacturing process, and location. The determination of MAOP includes a design factor to give a “cushion of safety.” The design factor is impacted by population density in the area around the pipe, which is why location matters.


Graphic is from the Enerdynamics Gas System Fundamentals seminar

 

MAOP is determined prior to construction of a new pipeline segment and new pipelines are pressure tested prior to being put into service to ensure that the line can actually safely operate under the design MAOP. For segments that include other components such as valves or regulators a Maximum Operating Pressure (MOP) is determined. The MOP includes the capabilities of the pipe as well as those for the other components.

For older pipelines, assuring a safe MAOP or MOP can be more difficult. For pipelines built prior to 1970, industry practice has been to assign a maximum pressure based on the highest recorded pressure at which the line was safely operated during the period 1965-1970. Only recently have many pipeline systems begun going back and using pressure testing or other techniques to verify the MAOP of older pipeline segments. The issue is one of cost and practicality – it is very expensive to pressure test existing lines, and many were not designed to allow easy use of modern testing techniques.

Beyond testing, another key factor in ensuring pipeline system integrity is maintenance and pipe surveying. Operable components such as valves and regulators are regularly tested and maintained as part of the pipeline’s integrity management program. Pipe can be checked through surface leak surveys and through internal surveys using devices such as pigs or robots.

Lastly, pipeline design and operating procedures can be structured to rapidly identify and minimize incidents when they do occur. This includes sophisticated pipeline monitoring and control systems plus strategic location of valves used to shut off flow when necessary. Automated valves are especially helpful, but their use is restricted to critical locations due to cost.

To ensure safe operations, each pipeline develops and implements a Pipeline Integrity Management (PIM) program that evaluates the current condition of pipeline assets, possible threats, likelihood of failure of specific assets, and the consequences of failure. The PIM then lays out preventative and mitigative measures the pipeline owner plans to implement. Special attention is given to so-called High Consequence Areas (HCAs) where incidents may result in serious consequences due to population density or other factors.

Proposed Changes to PHMSA Rules

The proposed new rule changes would extend to additional parts of the pipeline system and would expand rules associated with parts covered in existing rules. Changes include [2]:

  • Extending rules to many gas gathering pipelines and to newly defined Moderate Concentration Areas (MCAs)
  • Applying pressure testing and MAOP verification to pre-1970 pipelines
  • Modifying pipeline repair criteria
  • Providing additional direction on evaluation of internal inspection results
  • Clarifying requirements for conduction risk assessments, including addressing seismic risk
  • Expanding mandatory data collection and integration requirements
  • Requiring additional post-construction quality inspections
  • Requiring new safety features for pipeline launchers and receivers used in internal pipeline inspections
  • Requiring a systematic approach to verifying MAOP, and requiring operators to report when a pipe’s MAOP has been exceeded

The proposed new rules are out for public comment as I write this article and are expected to be implemented quickly. The result will be increasing time and money spent on pipeline safety, but hopefully a corresponding reduction in pipeline incidents.


 

Footnotes:

 

[1] “Pipeline Safety: Top Concern for All Segments of Natural Gas Industry,” Christina McKenna, Enerdynamics Energy Currents Blog, November 6, 2014

 

[2] For more discussion on pipeline safety, see: PHMSA Proposes New Safety Regulations for Natural Gas Transmission Pipelines, http://www.phmsa.dot.gov/pipeline/phmsa-proposes-new-safety-regulations-for-natural-gas-transmission-pipelines; PHMSA proposes significant changes for pipelines, http://www.lexology.com/library/detail.aspx?g=db6679c9-efe5-4b22-a4be-6c1d50da66e8; Significant New Safety Requirements Proposed for Natural Gas Pipelines, http://www.lexology.com/library/detail.aspx?g=5579ff62-5a03-4896-9307-073de1e4e8b9

 

 

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