.3 FIRE AND GAS DETECTION SYSTEMS: ACTIONS AND LOCATION CRITERIA
The characteristics and position of F&G Detection Devices in the Platform are in compliance with EN ISO 10418. All F&G Devices and their location are shown in the F&G Detection Layouts.
The following general criteria have also been applied.
The Fire and Gas Detection Systems are connected with the ESD/F&G System, as well as with Local and Remote Emergency and Alarm Systems.
Shut-down actions that are set to automatically occur due to detector alarms, shall require a voting System of instruments.
In particular, for Gas Detection, the 1ooN voting logic has been applied, including the failure case, such as:
• ALARM (20% LEL) → no automatic action (just alarm at NA/Q-PIII and NA/Q-PI Control Room);
• ACTION (50% LEL) → automatic action and alarm at NA/Q-PIII and NA/Q-PI Control Room;
• FAULT → just an alarm at NA/Q-PIII and NA/Q-PI Control Room.
The shut-down logic governing executive actions in response to Fire and Gas Detection is described in ESD/PSD Block Diagram and Cause & Effects Matrix.
In general, the issues which have been considered in determining the control actions initiated by the F&G System include:
• isolate the installation from the reservoir and pipeline;
• initiate the emergency depressurization process;
• initiate shut-down of Ventilation System to minimize ingress of smoke of flammable gas;
• initiate isolation of electrical equipment (except the Essential Safety System: safety lights and navigation aids) and other potential ignition sources upon detection of flammable gas to minimize the risk of ignition;
• initiate active fire protection Systems where these have been provided to control or mitigate hydrocarbon fires;
• activate PA/GA System in order to allow muster of personnel.
The Fire and Gas Detection System is connected with the ESD as well as with local and remote emergency and alarm Systems.
Typical applications and actions relevant to Fire/Gas Detection are shown in the following table, integrally extract from standard ISO 13702, to be taken into account where applicable according to Platform configuration: