Abstract
The design of Fire and Gas Detection System (FGDS) is by now a consolidated practice in the Oil & Gas industries. Excluding the building application (covered by specific standards), the design of the FGDS in terms of type, location, and number of the field fire and gas detection devices has been left to the single Oil & Gas Company Standards and Codes. Current discussions within the international community focus on how the FGDS should be designed so that it can be considered as a truly effective safety measure, capable of reducing the frequency of occurrence and/or the magnitude of the accidental event. In this context, the effectiveness of the FGDS depends not only on the reliability of its hardware and software, but also on the level of detection coverage it is able to ensure. Detection coverage is usually evaluated by analysing the overlap of coverage area of single detectors, while also considering blockage effects caused by structures, equipment, and piping. The detection coverage degree is defined as the ratio between the volume covered by detectors (detected volume) and the volume where the hazard can occur (risk zone). This paper focuses on the aspects of fire coverage degree, which can be evaluated by a 3D Detection Mapping Assessment (3DMA). The paper highlights how the flame Field of View (FOV) may be impaired in case of obstacles or improper installation and analyses the FGDS engineering life cycle from the definition of fire zones, the fire detectors voting for automatic alarms and Emergency Shut-Down (ESD) system activation, the impact on process solutions for shut-down and blowdown activation and the relevant 3DMA to the fire detectors installation and operation.
