MKOC Process Safety Center 2017 International Symposium
A Fire & Gas Detection System enables detection of a gas release or a fire scenario and raises alarms and/or initiates appropriate control action (system isolation, deluge, facility shutdown, etc.). This serves to minimize the potential for escalation of events that could lead to a catastrophic damage. To achieve this objective, the coverage of fire and gas detectors should be sufficient to detect gas leaks and fires and this should be set as a performance requirement. Risk assessments which take credit for successful detection of a release activating isolation and blowdown must be required to demonstrate the assumed performance can be achieved. Relying on conventional approaches based on experience and engineering judgement for developing fire and gas detector layout may not be sufficient. A 3D evaluation of the process unit helps to improve the coverage and demonstrate performance, taking into account detector specifications (technology, sensitivity, detection range, etc.), voting logic and reliability.
This paper examines various aspects of fire and gas detection, identifying the gaps and inconsistencies that exist in the detector layout developed based on conventional approaches. Using case studies, the paper demonstrates the necessity to refine these approaches to ensure all hazard sources are covered sufficiently. Furthermore, this paper presents the benefits of adopting a 3D assessment for fire and gas detector coverage using appropriate software tools and the aspects to be considered when such 3D calculations are used to determine coverage. Using case studies, the paper demonstrates how such 3D techniques can optimize the number and location of detectors. It also presents a brief overview of how advanced modelling using Computational Fluid Dynamics (CFD) can be used to supplement the 3D mapping tools.