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Abstract A reliable fire and gas detection system is vital for early detection of potential hazards and prevents escalation to catastrophic consequences by alerting the operator to take appropriate timely actions and initiating relevant automatic actions; it is more emphasized for relatively congested offshore facilities having limited means of safe personnel evacuation from toxic exposure/explosion hazards. To achieve a reliable fire and gas detection, it is essential to have a robust fire and gas detection system and strategic detectors placement. There are industry standard guidelines which propose suitable types of fire and gas detectors and provide advice for selection and placement. In addition, fire and gas mapping tools are becoming popular means to justify the correct location of fire and gas detectors. Rapid evolution to fire and gas detection technology has further contributed to the design challenges impacting detector quantity and its associated downstream system design. Ambiguities in Codes & Standards and the approach adopted during various stages of the project often cause over design and burden to Company. NPCC has experienced variety of challenges and lessons learned in fire and gas detectors selection and layout during EPC stage executed in the recent past. In one project, open path gas detectors suggested at FEED stage were changed to point type gas detectors during the EPC due to multiple cases of line of sight obstruction in the offshore platforms which resulted in a 4 fold increase to gas detector quantity. In another project, fusible plugs were considered during the FEED stage, to detect fire on unmanned well pads. However during EPC, fire and gas mapping study suggested using UV/IR type flame detectors as the fusible plugs cannot be considered for area coverage in the mapping study. This resulted in an additional 116 flame detectors besides the fusible plug type fire detectors. Finally, in another case, fire and gas mapping study during FEED stage suggested using HC detectors to monitor H2S leak at stoichiometric concentration. However, during EPC, it was recommended to use separate HC and H2S gas detectors resulting in doubling of the number of gas detectors. In conclusion, careful use of available technology and finalization of F&G detection philosophy at early stage of project is the first step for cost-effective solutions. Secondly, close coordination with the Consultant performing the mapping study to avoid unnecessary detectors is required. This paper attempts to outline the challenges and ‘Lessons Learnt’ by EPC Contractor for fire and gas detectors selection and placement. Finally, the paper proposes a way forward for effectively handling the same.
Abstract Passive Fire Protection (PFP) is a vital component of fire safety strategy for oil and gas installations. Passive fire protection ensures that relevant structures, piping and equipment or its components have adequate fire resistance with regard to the load bearing properties, integrity and insulation properties during a dimensioning fire event to prevent against escalation of consequences. PFP is generally used for protection of the safety critical systems, maintaining integrity of structures, protection of equipment, barrier walls and floors to provide stability as well as to segregate the plant into areas of manageable risk. It thereby helps in limiting the impact of fire on a facility, safeguards lives of personnel, restricts the growth and spread of fire, allows personnel to escape and offers protection to firefighters. The applicable Codes & Standards for PFP design are not prescriptive; rather performance based evaluation of the design is required to achieve desired fire safety. This approach, however, does not give unequivocal guidance to designers and can lead to ambiguities and overdesign due to interpretation differences. In the experience of authors, overdesign of PFP in many cases has had significant domino effects on other aspects of the design such as: Increased space requirement and layouts changes Increased weight which further impacts structural design particularly on off-shore installations Cost impact and schedule delays during the engineering phases Increased installation cost Added cost and complexity to plant inspection & maintenance for the entire operational life In one such case, it was observed that the incorrect selection of acceptable fire duration and heat flux values resulted in more than double the required quantity of PFP. In another case for an offshore installation, higher heat flux, impairment probability and frequency values were applied for the entire facility, including elevated process facilities that were beyond the range of the jet fires. This resulted in an excessive requirement of PFP leading to weight and space increase as well as difficulties in implementation and project delays. Based on these as well as other experiences, this paper proposes a structured and cost effective way forward for determining extent and reliable design of PFP while meeting current safety standards. The paper also presents some of the challenges the Contractor has encountered by way of actual case studies to demonstrate the effectiveness of the proposed methodologies for PFP estimation and optimization.