Development of Guidance on Potential Cascading Effects from Flammable Vapor Cloud Explosions

Main Objective

The overall objective of this research is to provide guidance on the potential cascading effects from flammable vapor cloud explosions and projectiles regarding structural damage at LNG facilities.In support of the above, the following objectives are outlined:

• Identify the range of LNG facility types and configurations, with an emphasis on defining the explosion sources, flammable inventories and the characteristics of targets.
• Assess the blast capacities of the targets.
• Define the VCE potential of the explosion sources and how this interacts with the targets.
• Develop guidance on the cascade potential that is sensitive to the characteristics of the type of LNG facility.

Public Abstract

The LNG industry has historically maintained a high degree of safety in its operations. This has been built on a clear understanding of the hazards associated with LNG processes, storage and transportation. There is however a need to examine the potential for incidents that are outside the normal experience of the LNG industry, so called ‘Black Swan' events.

One possibility, seen rarely in the global petrochemical industry, is a vapor cloud explosion (VCE). These events occur following the ignition of significant vapor clouds formed by accidental release of flammable fluids and can involve generating damaging overpressures. LNG, which in its vapor form is natural gas, is inherently safer in this respect compared to other fuels, but this does not remove the need to consider these events.

A key aspect of a VCE is that the damaging pressures can cause further failures in equipment and as a result, the incident escalates. These ‘Cascade Effects' can significantly increase the severity and extent of a VCE event. Understanding the potential for Cascade Effects on LNG facilities can inherently improve safety, protecting both people and key energy infrastructure.

DNV GL and Thornton Tomasetti have long experience in assessing the severity of explosions and the response of structures to exceptional loads. This expertise has been brought together in our proposal to develop guidance in how to assess the potential for Cascade Effects and, more importantly, how to avoid them. The research will commence with a review of existing and proposed LNG facilities to ensure guidance is relevant to actual facilities. We will then define the VCE potential and conduct detailed simulation of the explosion events and the response of structures to the explosion pressures. The technical work will then be translated into guidance for both PHMSA and the LNG industry.