Preparing for potential ruptures
As part of their “Valve installation and minimum rupture detection standards” final rule introduced in 2022, the Pipeline and Hazardous Materials Safety Administration (PHMSA) aim to reduce the consequences of large-volume, uncontrolled releases of natural gas and hazardous liquid pipeline ruptures after a number of reported incidents caused significant damage to the environment or human life.1
Included in this final rule is a set of actions required from pipeline operators upon “Notification of Potential Rupture”. In this blog, Senior Vice President Adrian Kane summarizes the “Valve installation and minimum rupture detection standards” before introducing the “Notification of Potential Rupture” requirement and what’s expected from pipeline operators.
About the Valve Installation and Minimum Rupture Detection Standards
This final rule was published on April 8, 2022, becoming effective from October 5, 2022.
The aim of the rule is to establish minimum safety performance standards for the identification of ruptures, pipeline segment isolation and other mitigative actions for pipelines on which rupture mitigation valves (RMVs) or alternate technologies are installed.
The standards apply to most Type A gas gathering and gas transmission lines (with limited exceptions, such as if the pipeline segment is in a Class 1 or Class 2 location and has a potential impact radius less than or equal to 150 feet).2 The standards also apply to hazardous liquid and carbon dioxide pipelines and include a small subset of rural gathering lines which cross bodies of water greater than 100 feet wide.
Corrections to the final rule
On August 1, 2023, amendments to the final rule were published. In addition to typographical corrections to avoid confusion, PHMSA made the following technical changes:*
- Rupture mitigation valves (RMV) or alternative technologies are required and the minimum performance standards need to be met for the operation of those valves to reduce environmental consequences and impacts to public safety in the event of a rupture
- On onshore gas pipeline segments 6 inches or greater in diameter, RMVs must be installed (with some exemptions)
- All new pipelines, regardless of high consequence area (HCA) status or class location definition must install RMVs in accordance with 192.179
- Valve spacing requirements are now available in 192.610 for certain gas pipeline operators to follow when a class location change occurs
- All operational requirements from 192.634 for rupture identification, valve shut-off time and flow modeling for automatic shut-off valves (ASVs) were originally included in the new § 192.636
The Valve Installation and Minimum Rupture Detection standards contains the “Notification of Potential Rupture” requirement, which received its own corrections on August 1, 2023, including:*
- Clearer explanation that the uncontrolled release of hazardous liquids includes carbon dioxide
- Re-inserting the word “mainline” in 195.420(b) to clarify which valves need to be inspected at least twice each calendar year (but not at intervals exceeding seven and a half months)
- Specifying what “drill” means in the context of RMVs
*This doesn’t represent an exhaustive list and PHMSA reserves the right to make future corrections to the Valve Installation and Minimum Rupture Detection Standards. For full details of the August 1, 2023 corrections, click here
Defining the “Notification of Potential Rupture” requirement
The “Notification of Potential Rupture” can generally be defined as the notification or observation by an operator that the criteria for an unintentional or uncontrolled release of a large volume of hazardous liquid, carbon dioxide or other gas from a pipeline has been met.3,4
This decision is reached via rupture identification. PHMSA has separate definitions for a rupture related to a hazardous liquid or carbon dioxide release and a hazardous gas release.
Hazardous liquid or carbon dioxide rupture definitions (as defined in 195.417)
1. A release observed and reported to the operator by a controller in the control room, field personnel, nearby pipeline or utility personnel, the public, local responders or public authorities, relating to one or more of the below signs of a potential unintentional or uncontrolled release of a large volume of hazardous liquids or carbon dioxide from a pipeline:
a. Unanticipated or unexplained pressure loss outside a pipeline’s normal operating pressures from the operator’s written procedures
When there is a pressure loss greater than ten percent occurring within a time interval of 15 minutes or less, the operator must establish in the written procedures that the unanticipated or unplanned pressure loss is outside the pipeline’s normal operating pressures, unless the operational need for a greater pressure-change threshold due to pipeline flow dynamics are documented in the operator’s written procedures
b. Unanticipated or unexplained flow rate change, pressure change, equipment function or other pipeline instrumentation indication at the upstream or downstream section that could represent an event from 1.a
c. An unanticipated or unexplained rapid release of a large volume of hazardous liquid or carbon dioxide, a fire or an explosion in the immediate vicinity of the pipeline
2. “Notification of Potential Rupture” occurs when an operator initially receives notice of or observes an event specified in 1.
3. The requirements in this section don’t apply to gathering lines
Hazardous gas rupture definitions (as defined in §192.635)
1. A release observed and reported to the operator by a controller in the control room, field personnel, nearby pipeline or utility personnel, the public, local responders or public authorities, relating to one or more of the below signs of a potential unintentional or uncontrolled release of a large volume of gas from a pipeline:
a. Unanticipated or unexplained pressure loss outside a pipeline’s normal operating pressures from the operator’s written procedures
When there is a pressure loss greater than ten percent occurring within a time interval of 15 minutes or less, the operator must establish in the written procedures that the unanticipated or unplanned pressure loss is outside the pipeline’s normal operating pressures, unless the operational need for a greater pressure-change threshold due to pipeline flow dynamics that are caused by fluctuations in gas demand, gas receipts or gas deliveries, are documented in the operator’s written procedures
b. Unanticipated or unexplained flow rate change, pressure change, equipment function or other pipeline instrumentation indication at the upstream or downstream section that could represent an event from 1.a
c. An unanticipated or unexplained rapid release of a large volume of gas, a fire or an explosion in the immediate vicinity of the pipeline
2. “Notification of Potential Rupture” occurs when an operator first receives notice of or observes an event specified in 1.
“Notification of Potential Rupture” requirements
Operators demonstrating compliance with the Valve Installation and Minimum Rupture Detection Standards are required to make the following preparations for the “Notification of Potential Rupture”:
1. Establish written procedures for identifying and responding to a rupture
2. Respond to an identified rupture by closing rupture mitigation valves (RMVs) or by using other equivalent technology to provide complete valve shut off and segment isolation within 30 minutes of a rupture being identified
3. Perform post-event reviews of any incidents, accidents or other failure events involving the closure of RMVs or other equivalent technologies
4. Perform maintenance on RMVs and other equivalent technologies, including drills for other equivalent technology that is manually or locally operated
5. Remediation measures for repair or replacement of inoperable RMVs and other equivalent technologies, including an RMV or other equivalent technology that cannot maintain shut-off, as soon as possible
Atmos helps prepare operators for the “Notification of Potential Rupture” requirements
As new rulings emerge and existing rulings are frequently updated, it’s important for operators to demonstrate compliance and have the relevant documentation, procedures and training in place.
Most liquid pipelines will exceed the threshold that classifies a pressure drop as a rupture during shutdowns and other legitimate operations (see Figure 1).
In response to the “Notification of Potential Rupture” requirements, Atmos has added new functionality within the latest versions of our Atmos Pipe leak detection system in the form of the Atmos 417 Rupture Compliance Module.
Figure 1: Atmos 417 Rupture Compliance module’s presented pressure drops as percentages over four days. The top line represents the average operating pressure of the pipeline over a four day period, the middle line shows the percentage change from the historical average pressure and the bottom line presents the system output flagging to the user when the pressure drop has exceeded 10%
Atmos’ 417 Rupture Compliance Module can provide a rupture classification either separately to or in tandem with Atmos’ leak detection systems. When integrated with Atmos’ suite of leak detection software, the Rupture Compliance Module uses the same data retention methods, system management tool and trending system (see Figure 2) already familiar to Atmos users.
Figure 2: Charting of information and table display of data provided by Atmos Trend. Figure 1 demonstrates an example pipeline exceeding 10% average pressure drops due to normal operating conditions. Here, the trending tool presents that information to the operator so they can make an adjustment to the system thresholds
The module connects to the control system to obtain data and will return classification notifications via the same channel using a wide range of industry protocols.
Atmos 417 Rupture Compliance Module works with Atmos Pipe to reassure operators that they are demonstrating compliance with the specific requirements of the “Notification of Potential Rupture”.
Learn more about regulation compliance support at Atmos
Leak detection regulation compliance service Guidance on leak detection regulations
References
1 https://www.phmsa.dot.gov/regulations/federal-register-documents/2022-07133