Objectives/ scope

This paper analyses the dangers of inappropriate design of Fire and Gas (F&G) systems not only to the hazards in question, but in failing to take account of the hardware/ environmental drawbacks to ensure a safe and reliable system. The review will detail common misconceptions of F&G devices, focusing on flame detectors and flammable gas detectors.

Methods, Procedures, Process

This will also review the significant cost savings which can be introduced when incorporating knowledge of how these instruments operate, and the hazards in question, in the F&G design. Taking account of these factors has been demonstrated to increase overall plant safety and greatly reduce the CAPEX costs of projects. It is also evident that when these systems are not adequately designed, the costs in unwanted shutdown/ plant down time can be unnecessarily excessive.

The paper will discuss the matters in light of the current challenging climate of the Oil and Gas Industry and how different disciplines must work together to ensure while overheads are being reduced, this is not at the expense of safety.

Results/ Observations/ Conclusions

The main conclusion to be drawn is that: 1) too much emphasis is placed on the simple percentage coverage achieved which can significantly over engineer a system; and 2) not enough emphasis is placed on the characteristics of the hardware being mapped which can cause issues at a later date with unwanted downtime.

Novel/ Additive Information

As the process industry moves towards the reduction of the potential for ‘fail to danger’ in safety related systems (with an increase in the prevalence of IEC 61508 and IEC 61511), it is of great concern that designs of fire and gas detection technologies (whether classed as a SIS or not) applied today still provide this potential, and even worse, these drawbacks may never be accounted for in design. In light of this, the guidance within the recent guidance document ‘ISA TR84.00.07 Guidance on the Evaluation of Fire and Gas System Effectiveness’ shall be reviewed with reference to its efficiency and what can be done better by those following the guidance, to ensure it remains relevant in the current challenging climate.

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