17 - Fire and Gas Detection and Alarm Systems

Abstract

This chapter discusses the fire gas detection and alarm systems. Various simple and sophisticated fire and gas detection systems are available to provide early detection and warnings of a hydrocarbon release that supplement process instrumentation and alarms. The overall objectives of fire and gas detection systems are to warn of possible impending events that may be threatening to life, property, and continued business operations, and that are external to the process operations. The chapter briefly explains several detectors; smoke detectors are employed where the type of fire anticipated and equipment protection needs a faster response time than heat detectors. A smoke detector will detect the generation of the invisible and visible products of combustion before temperature changes are sufficient to activate heat detectors. The ability of a smoke detector to sense a fire is dependent on the rise, spread, rate of burn, coagulation, and air movement of the smoke itself. Thermal or heat detectors respond to the energy emission from a fire in the form of heat. The normal means by which the detector is activated is by conventional currents of heat air or combustion products or by radiation effects. Another detector is gas detector; gas detection is provided in the process industries to warn and possibly prevent the formation of a combustible gas or vapor mixture that could cause an explosive overpressure blast of damaging proportions or initiation of fire.