After submitting a petition for approval of Phast 8.4 as an alternate model for calculating flammable vapor dispersion exclusion zones under 49 C.F.R. § 193.2059(a), DNV is thrilled to announce that PHMSA has granted approval to our petition.
PHMSA and the approval
The Pipeline and Hazardous Materials Safety Administration (PHMSA) is a United States government agency responsible for ensuring the safe transportation of hazardous materials (such as chemicals, explosives, and radioactive materials) by pipelines, trucks, trains, and other modes of transportation. PHMSA is also responsible for regulating the design, construction, operation, maintenance, and spill response planning of hazardous liquid and gas pipelines. The agency works closely with industry, state and local governments, and other stakeholders to promote safety and prevent accidents related to the transportation of hazardous materials.
As the regulator in the US that authorizes and approves models that can be used for LNG siting applications, PHMSA will only accept hazard zone calculations based on models on an approved list.
Prior to the approval of Phast 8.4, DNV customers were restricted to using version 6.7, which was the last version approved back in 2011. This scenario meant that assessments were being based on models that were over a decade old. Despite numerous updates and enhancements to our modelling, US customers were still obliged to use the outdated version. The software architecture has since evolved, making it difficult for customers and DNV to support version 6.7. Receiving the approval allows our customers to transition to version 8.4, with improved access to support and superior modelling capabilities.
The decision letter can be found on the PHMSA website.
Benefits of the approval
In the process of conducting risk analysis for these facilities, safety professionals are tasked with determining potential hazard zones for onsite LNG. The magnitude of these zones often directly correlates with the level of concern and the likelihood of obtaining approval. Zone sizing is heavily dependent on the software employed to estimate hazard ranges predicted from failure scenarios resulting in LNG spills and vapor cloud formation.
The approval process ensures that the software used for simulating these scenarios has been scrutinized and endorsed by industry experts, validating its usage. With the recent endorsement, Phast 8.4 can now be utilized as an alternative model for flammable vapor-gas dispersion when calculating flammable vapor dispersion distances to the Lower Flammable Limit (LFL).
Phast users no longer need to maintain outdated versions and legacy systems. Some users persisted with version 6.7 to avoid dealing with two versions concurrently; however, this will no longer be a concern. We have also implemented numerous improvements in the modelling in areas besides LNG, as well as new features that users of Phast 8.4 will benefit from, contributing to an overall more effective and efficient experience.
Additional benefits of a switch to Phast 8.4 include:
- New 64-bit architecture – with improved stability and performance
- A ‘modern’, user friendly user interface (UI)
- Improved graphs and reports
- New UDM model, including major changes to dispersion from and over pools, far-field along-wind diffusion, gravity spreading
- Improved instantaneous expansion model, especially for 2-phase releases
- Crater formation for ruptures of buried pipelines
- Improved modelling of time-varying releases from vessels and short pipes, including ability to model isolation and vessel blowdown
Frequently asked questions
- Can versions later than Phast 8.4 be used?
At the time of submitting the petition, Phast 8.4 was the latest version commercially available. Therefore, this is the version that has been granted the approval. Later versions can be used in the US for other types of studies, but Phast 8.4 is the version to use for LNG flammable vapor-gas dispersion exclusion zones.
- How can I obtain the latest approved version and read the release notes?
The latest version approved by PHMSA and the release notes, with dates for each release, are available through our knowledge centre – all our customers with service level agreements (SLAs) have access to this site. The release notes include detailed information about each version.
Phast is a globally adopted solution for modelling discharge, dispersion, fires, explosions, and toxic effects of a wide range of loss of containment scenarios. It is great for:
- Accident and incident investigation
- Consequence estimation for HAZOP, HAZID, PHA and LOPA
- Emergency response planning
- Equipment design, facility siting and layout optimization
- Regulatory obligations (e.g. safety reports)
- Other general consequence estimation
More information about Phast
AuthorsMike Harper, Senior Principal Specialist, DNV
Frank Hart, Principal Specialist, DNV
James Pickles, Product Manager for Phast, Safeti, KFX and EXSIM, DNV