Developments in flame detectors

Abstract

Flame detectors are extensively used for outdoor risks and for indoor risks where flammable solvents and liquids are used. Two types of flame detector are available, one type detecting the infra-red radiation from the flame and the other type detecting the ultraviolet radiation. The ultraviolet detector has been extensively used for protection against outdoor risks because of its insensitivity to solar radiation, while the infra-red detector has advantages in the indoor environment because of a greater detection range and reduced cost. Both types of detector can be affected by their environment causing false alarms, the ultraviolet detector being extremely sensitive to arc welding and the infra-red detector being affected by hot sources, such as lamps and heaters. The paper reviews the state of the art of flame detectors comparing performance, reliability, etc. of the various types on the market and describes the methods employed to reduce false alarms from environmental factors. The paper also describes the design, construction and performance of a new infra-red flame detector now on the market. This detector has been designed for use in hostile environments both indoors and outdoors. It is unaffected by solar radiation and is intrinsically safe, thus being suitable for use in hazardous environments.