Pipeline Rupture Detection Standards

PHMSA Publishes NPRM for Pipeline Rupture Detection Standards

On February 6, PHMSA published to the federal register a Notice of Proposed Rulemaking (NPRM) titled: “Amendments to Parts 192 and 195 to Require Valve Installation and Minimum Rupture Detection Standards.”

This NPRM proposes to revise the Pipeline Safety Regulations applicable to newly-constructed and entirely replaced (two or more miles) onshore natural gas transmission and hazardous liquid pipelines with nominal diameters greater than or equal to 6 inches.

PHMSA is proposing that operators of these lines install remote-control or automatic shutoff valves — or equivalent technology — to mitigate ruptures.

Additionally, PHMSA is proposing to revise the regulations regarding rupture detection for certain pipelines in high-consequence and select non-high-consequence areas to shorten pipeline segment isolation times.

“This rule will improve critical safety requirements for the next generation of energy pipelines as U.S. energy production continues to grow,” said U.S. Transportation Secretary Elaine L. Chao in a news release on the NPRM.

Ultimately, PHMSA is proposing the new rule to reduce the consequences of large-volume, uncontrolled releases of natural gas and hazardous liquid pipeline ruptures.

How is a Rupture Defined in the NPRM?

The proposed revision to PHMSA pipeline safety regulations defines “ruptures” as an event that encompasses any type of large-volume, rapidly occurring, and uncontrolled release or failure.

A rupture, as defined in the NPRM, would include any of the following events that involve an uncontrolled release of a large volume of product over a short period of time:

  • An unanticipated or unplanned pressure loss of 10 percent or more, occurring within a time interval of 15 minutes or less (with certain specific exceptions relevant to gas and liquid pipelines).
  • An unexplained flow-rate change, pressure change, instrumentation indication, or equipment function.
  • An apparent large-volume, uncontrolled release of gas or a failure observed by operator personnel, the public, or public authorities.

Ruptures would also include events that have rupture-like characteristics in terms of pressure and flow profiles. These events include:

  • Failures due to mechanical punctures, line breaks, and other large-scale failures.
  • Seam splits.
  • Large through-wall cracks.
  • Sheared lines due to natural or other outside force damage.
  • Valves inadvertently left open.

Standards For Identifying And Responding to a Rupture

The proposed rulemaking outlines standards related to rupture identification and pipeline segment isolation. This includes establishing a 40-minute maximum rupture-mitigation valve closure time.

PHMSA is also proposing requirements that fall under prevention, maintenance, and response to improve operator rupture mitigation:

  • Valve maintenance and inspection
  • Valve spacing
  • Rupture-mitigation valve risk analysis
  • Post-incident investigation and review
  • Enhanced coordination with 911

“This proposal is backed by extensive research that supports the use of remotely controlled and automated valves as both cost-effective and capable of minimizing potential delays between the identification and isolation of a pipeline release,” said PHMSA Administrator Skip Elliott in the news release.

How the NPRM Would Affect Gas and Liquid Pipelines

In the NPRM, PHMSA is recognizing rupture mitigation differences between natural gas pipelines and hazardous liquid pipelines.

Gas Pipelines: PHMSA is defining the behavior of a gas pipeline rupture as a sudden release of energy that is sustained for long periods of time even after the system is shut down, as the pressurized gas expands into the atmosphere and remains in relative proximity to the failure site.

PHMSA is recognizing that when gas ruptures ignite, the length of time that the gas pipeline is not shut down and isolated could lead to consequences such as fires. These fires may be containable, but could also spread outward and cause significant additional damage beyond the immediate impact zone.

Liquid Pipelines: PHMSA is defining a hazardous liquid pipeline rupture as an event when the volume of product released increases and spreads further over the surrounding terrain. As response and isolation times are prolonged, this significantly increases the potential for adverse consequences.

The goal is to limit the amount of product released and to minimize the size of the affected area. Otherwise, it could take months or even years to restore a site to its pre-incident condition.

– The commonality for both gas and liquid, as identified by PHMSA, is to quickly isolate the rupture segment so that it does not significantly alter the immediate impact of the rupture.

Through the proposed rulemaking, PHMSA is seeking to drive improvement in rupture response and isolation times to reduce a rupture’s extended consequences. The common objectives for both gas and liquid boils down to:

  • Prompt identification
  • Rapid system shutdown
  • Segment isolation

What’s Next for Pipeline Operators Responding to the NPRM?

– The immediate response from PHMSA-regulated pipeline operators is to take advantage of the opportunity to submit comments to the NPRM.

Comments are due 60 days after the publication of the NPRM, which is April 6, 2020. The proposed rulemaking includes instructions for how to submit comments.

– As the NPRM proceeds through the federal rulemaking process, we also recommend that operators perform an evaluation of your rupture mitigation approach.

Ensure that your operation is aligned with the objective to reduce the consequences of ruptures. This includes focusing on improving both rupture identification and rupture mitigation. Specifically, more rapid and effective isolation of failed pipeline segments.

Have questions about the proposed PHMSA pipeline safety regulations? Contact EnerSys today to discuss the NPRM and how it may affect your operation.