When is a Gas Release Significant Enough to Require Detection?
Over the past decade significant improvements have been made in the design methods for gas detection systems by the application of risk-based approaches replacing outdated and inaccurate heuristics. With the initial release of ISA technical report 84.00.07 in 2010 (revised 2018), the use of quantitative analysis of coverage provided detector arrays is now common and expanding. This technical report introduced the concept of coverage, in terms of both simple geometry assumptions (geographic/volumetric coverage), and actual modeled release scenarios (scenario coverage). While dispersion modeling techniques, both similarity gaussian models and computational fluid dynamics, are established and understood, there is a lot of confusion as to what should be modeled as the basis for the design. Options include various hole sizes (e.g., 5 mm, 25 mm), release rates (e.g. 100 kg per hour), gas cloud flammable mass, gas cloud flammable distances (5 m), and countless other options. Engineers lack guidance in what the basis should be and why. Furthermore, different industries have different philosophies that will make these numbers change.
In this webinar, we will briefly explore the history of gas detection mapping, including migration to a preference of scenario-based coverage. We will also present different philosophies, such as accumulation detection, smallest credible consequence, insurance-level loss prevention, and offsite consequence avoidance. Finally, we will describe the philosophies and provide step-by-step processes for determining what should be modeled as a function of the philosophy for gas detection at a site.