Case Study: Providing a proactive risk management approach for rupture mitigation valves

Special Focus—Valves, Pumps, Compression and Turbomachinery

C. PARKER, Dynamic Risk, Washington D. C. (U.S.)

U.S. federal natural gas pipeline regulation 49 CFR 192.935(c) requires that operators perform a risk analysis to determine where the use of rupture mitigation valves (RMVs), such as remote-controlled valves and automatic shutoff valves, may be efficient to add protection to high consequence areas. In addition, regulation 49 CFR 192.935(f) requires that these risk analyses are certified by a senior executive of the pipeline operator on an annual basis.

In 2023, to support meeting these regulatory requirements and to enhance existing risk management, a U.S. transmission pipeline operator retained the author’s company to perform an independent RMV risk analysis. Effectively, an RMV risk analysis must evaluate the potential risk reduction from a rapid valve closure enabled through the installation and operation of RMV technology. Since the rapid valve closure is a mitigative measure that would occur after a pipeline rupture has occurred, the focus of the risk analysis was on evaluating the reduction in consequences of failure. Additionally, in the context of natural gas pipelines, the primary benefit of rapid valve closure is to minimize damage to buildings by allowing faster, safer access for emergency responders, particularly to extinguish secondary fires. 

While the pipeline operator’s existing pipeline risk assessment model utilized for integrity management evaluated the likelihood and consequences of failure, a targeted risk analysis was sought to proactively analyze the specific mitigative measure of a rapid valve closure—this was  in conjunction with firefighting efforts to potentially reduce building damage following a hypothetical ignited pipeline rupture. 

Solution. Evaluating the potential damage reduction of rapid valve closure along with the firefighting response is a complex analysis that encompasses the consideration of several variables:   

• The time it takes to close valves to isolate a pipeline segment  

• The location of the pipeline rupture 

• The properties of the pipeline at the rupture location  

• The transient gas release mass flow  

• Thermal radiation based on the transient gas release 

• The proximity of structures to the pipeline 

• The area where buildings could be potentially impacted by thermal radiation [potential impact circle (PIC)] 

• The type and size of structures potentially impacted by thermal radiation 

• The area where firefighters could safely access buildings after a rupture [firefighting circle (FFC)] 

• The response time for building firefighting. 

The author’s company developed a risk-based solution to consider these variables and simulate a hypothetical rupture at multiple points along the pipeline system to determine site locations where rapid valve closure, combined with fire-fighting efforts, could potentially reduce building damage.   

A simplified framework of the RMV risk analysis solution is shown in FIG. 1.

As a first step, the pipeline operator provided the author’s company with geospatial data of its pipeline system, as well as any buildings in proximity to the pipeline. Then, utilizing geospatial analytics technology, the pipeline and buildings data were integrated within a gas release model, thermal radiation model and an emergency response model to perform consequence estimation at dynamically segmented points along the pipelines, including the evaluation of: 

• The radius of the PIC was determined based on the formula in CFR 192.903. 

• The radius of the FFC was estimated based on assumptions for the time to close valves, the gas release model, the thermal radiation model and the emergency response model. 

• The buildings within the PIC and FFC were identified. 

An example of the buildings within the PIC and FFC at one point in the pipeline system is illustrated in FIG. 2. 

Buildings that were determined to be within the PIC but not within the FFC were considered to be potentially mitigated by firefighting activities. The value of the potential building damage reduction was based on several factors, including the size and type of building. Once the potential building damage reduction was estimated, it could be plotted along each pipeline segment (FIG. 3). 

Subsequently, for each of the approximately 300 pipeline segments assessed in the pipeline operator’s network, a comparison was made between the maximum potential reduction in building damage for each segment and the projected cost of installing RMV technology in that segment. This comparison aimed to evaluate whether implementing RMVs was an efficient mitigation strategy, specifically determining if the potential reduction in building damage outweighed the costs associated with application of the mitigation measure. 

Project outcome. The RMV risk analysis was completed over a period of several weeks after receiving the geospatial data. The analysis report provided potential building damage reduction estimates along each of the pipeline segments that were in a high consequence area (HCA). Considering the estimated installation costs of RMVs, a comprehensive assessment was performed to determine where RMVs may be an efficient measure to add protection to an HCA. This provided a screening level risk-based prioritization for the pipeline segments in the scope of the project. 

Overall, the results of the analysis showed that for most of the pipeline segments, the estimated cost of installing RMVs exceeded the estimated potential building damage reduction cost, and thus may not be an efficient use of resources to manage risk. For those few pipeline segments where the potential building damage reduction was estimated to exceed the cost to install RMVs, they were prioritized for additional detailed analysis. 

The RMV efficiency results provided reasonably addressed the requirements of CFR 192.935(c). The results can inform and support the pipeline operator’s decision-making about potential additional measures that could be taken to mitigate the consequences of a potential pipeline rupture, including the option of installing RMVs. In addition, information was provided from the analysis that was useful in support of the pipeline operator’s broader transmission integrity management program.   

A key to the project’s success was close collaboration with the pipeline operator’s team to iteratively adjust as the solution was applied to actual geospatial data. Many variables had to be considered and aligned with the appropriate attributes in the geospatial database to ensure accurate results, and the cooperation between teams made this possible in a timely manner. 

Benefits. The following benefits of the analysis were realized: 

• It demonstrated adherence to U.S. federal regulations by conducting a thorough RMV risk analysis as mandated, ensuring that the process meets or exceeds the established standards. 

• It provided for a proactive approach to risk mitigation, identifying and addressing potential issues before they escalate into serious problems. 

• It highlighted pipeline segments where the installation of RMVs exhibited a potential to be an effective mitigative measure, indicating areas where investment in RMVs could yield significant safety improvements. 

• It established a framework to prioritize pipeline segments requiring in-depth consequence analysis, thereby enabling the allocation of resources towards areas with the highest potential for risk reduction. 

• It increased the effectiveness of risk management by ensuring that the pipeline operator’s resources are invested in the highest value risk management projects and activities. 

• It identified opportunities to enhance emergency response planning and preparedness. 

• It augmented the pipeline operator’s existing risk management program with a detailed characterization of potential consequences that enables targeted prevention and mitigation measures. 

• It integrated the latest technological advancements in RMV systems, ensuring that the pipeline operator’s infrastructure benefits from the most efficient and reliable safety mechanisms currently available. 

• It established a system for regularly updating risk analysis models to incorporate new data, technological improvements and changes in regulatory standards, ensuring that the risk management strategy remains current and effective. GP&LNG

ABOUT THE AUTHOR

Curtis Parker is a recognized leader with more than 20 yr of experience asset reliability management of energy infrastructure, including in design, construction and operations of natural gas and liquid pipeline systems, and natural gas utilities. His experience includes directing a pipeline integrity organization responsible for reliability of > 16,000 mi of gas transmission pipelines across 30 U.S. states, Canada and Mexico. Parker has proven hands-on and management expertise of asset reliability, including risk assessment, inspection, repair and maintenance, with extensive experience managing field construction, inspection and repair projects. He has led pipeline rupture investigations and interfaced directly with federal regulator staff. Parker has an in-depth working knowledge of safety management systems, as well as regulations and industry standards for integrity management, including DOT 49CFR 192, ASME B31.8S, and API 1173. He earned a BS degree in mechanical engineering from the University of Saskatchewan.

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