SIL aspects in relationship to Fire and Gas systems

The paper will look at a number of aspects in determining the safety requirements for Fire & Gas system associated with a Oil & Gas production or petrochemical plant. Two approaches will be considered. One approach will be by considering the number of general cases and determining a general SIL target for Fire & Gas safety loops, the other approach will be to undertake a SIL targeting exercise for each of the plant location and determine the requirements using LOPA. Clearly for the safety loops to be effective, not only will they have to met the require reliability but the detectors have correctly located and the paper will also include examples of dispersion modelling to assist in the location of gas detectors.