Upcoming performance standards proposed for US gas pipelines
To reduce methane emissions as part of the USA’s Methane Emission Reduction Action Plan, the Gas Pipeline Leak Detection and Repair ruling is currently in the notice of proposed rulemaking (NPRM) phase.
This ruling would require new and existing gas transmission pipelines, distribution pipelines, regulated gas gathering pipelines (types A, B, C and offshore), underground natural gas storage facilities and liquefied natural gas facilities to reduce their emissions.
This regulatory action aims to reduce both fugitive emissions, which result from leaks and equipment failures, and vented (intentional) emissions, which are caused by blowdowns, equipment design features and other intentional releases.1
Figure 1: Two types of emissions targeted by PHMSA in §192.763
While representing a series of regulatory amendments to Title 49 of the Code of Federal Regulations, crucial to this ruling are the proposed performance standards for advanced leak detection programs (§192.763).
Here, Business Development Director for gas Bob Truman will discuss §192.763 and how operators can prepare for it.
Breaking down §192.763: why have new performance standards been proposed?
Historically, PHMSA regulations have prioritized addressing incidents such as the ignition or large volume releases of gas while neglecting background leaks in gas gathering, transmission and distribution pipeline facilities.2 These leaks can go unnoticed for a period of time and escalate into catastrophic incidents if they go unrepaired.
PHMSA are required to issue performance standards reflecting commercially available, advanced leak detection technologies and practices for leak detection and repair programs, according to section 113 of the 2020 PIPES Act.3 § 192.763 was proposed to satisfy this mandate.
What are the new proposed performance standards?
The new performance standards associated with an advanced leak detection programme (ALDP) can be categorized into:
- Leak detection technology standards
- Leak detection practices
- Leakage survey frequency
- Program evaluation and improvement
Leak detection technology standards
Relating to the technology operators use for leakage surveys, the investigation of leaks and pinpointing leak locations, requirements are set out in § 192.763(a)(1).
A notable proposition from PHMSA is that any leak detection equipment used for leakage surveys must have a minimum sensitivity of 5 ppm or less.
The new leak detection standards also indicate when operators should use leak detection equipment and when they can use methods that rely on human or animal senses, such as line walking and sniffer dogs.4
This element relates to operators’ leak detection, investigation and location procedures. As a minimum, operators are being asked to include procedures for performing leakage surveys and investigating and locating identified leaks, as well as the role each piece of ALDP leak detection equipment would have in performing any involved tasks.
Operators must also define conditions under which their procedures can and can’t be used, such as in the case of external factors like environmental conditions including humidity, temperature, time of day and more. Procedures must also be consistent with any instructions, allowable operating and environmental parameters of the leak detection equipment’s manufacturer.
To improve on leak location, ALDP procedures are required to investigate and pinpoint the location of all reported leaks. Onshore pipelines and offshore pipeline facilities above the waterline must use handheld leak detection equipment with a minimum sensitivity of 5 ppm and procedures must be in place for validating that these devices meet sensitivity requirements before initial use. This can be achieved by testing the equipment against a concentration of gas.5
Under the proposed ALDP requirements, there’s now a minimum leakage survey frequency. For example, an operator’s leak detection equipment with low sensitivity may need more regular leakage surveys and these must be documented in the operator’s ALDP.6
Program evaluation and improvement
The following elements of the ALDP must be reevaluated annually as a minimum:
- Performance of the leak detection equipment used
- Adequacy of leakage survey procedures
- Advances in leak detection technologies and practices
- Number of leaks initially detected by third parties
- Number of leaks and incidents on the pipeline
- Estimated emissions from detected leaks
The expectation from this part of the NPRM is that operators will iteratively improve their leak detection programs based on leak detection data and technological advancements.
For example, an operator could discover that their ALDP only detects grade 1 and 2 leaks but not grade 3 leaks, proving the importance of continuous program evaluation and improvement (see Figure 2).
Figure 2: Leak grades as defined by the Gas Piping Technology Committee8
*Example leaks for each grade don’t represent an exhaustive list
Planning for the ALDP performance standards
Operators must factor a range of standards into their ALDP, including:
- Capability for detecting all leaks that produce a reading of 5 ppm or greater of gas when measured from 5 feet from the pipeline
- The 5 ppm standard must include commercially available, advanced leak detection equipment
- When leak detection equipment should be used and when methods that rely on human senses can be used
- Procedures for performing leakage surveys and investigating and locating identified leaks
- The minimum leakage survey frequency
- Program evaluation and improvement
While the Gas Pipeline Leak Detection and Repair ruling is currently still in NPRM phase and not guaranteed to come into force, the standard aims to periodically survey pipelines and equipment for leaks. In the meantime, Computational Pipeline Monitoring (CPM) methods should be considered for continuous leak detection as is required on hazardous liquids that will detect leaks as they occur and help reduce the volume of the larger incidents that create large emissions very quickly. There are already well developed and tested CPMs available such as Atmos Pipe and Atmos Simulation (SIM) Suite.
Atmos Pipe
Since its release as the first statistical volume balance system in 1995, Atmos Pipe has been at the forefront of leak detection technology. It uses the powerful Sequential Probability Ratio Test (SPRT) with pressure and flow analysis to optimize leak detection.
Atmos Simulation (SIM) Leak Detection
Atmos SIM leak detection module continuously calculates the volume balance. This volume balance is obtained by calculating the total flow into the system minus the total flow out of the system corrected by the inventory changes calculated by Atmos SIM.
The volume balance is statistically analyzed by the sequential probability ratio test (SPRT), which calculates the ratio of leak probability over no-leak probability. This ratio is then tested against certain threshold values to provide leak warnings/alarms.
References
2 https://www.federalregister.gov/d/2023-09918/p-236
4 https://www.federalregister.gov/d/2023-09918/p-499
5 https://www.federalregister.gov/d/2023-09918/p-509
6 https://www.federalregister.gov/d/2023-09918/p-513