Fire detector scanning arrangement

摘要

A detector that monitors infra-red ray emission from an air preheater to detect a temperature rise that precedes a fire within the air preheater. The detector of infra-red rays is alternately moved between a "detecting" stage within the air preheater and a "cleaning" stage in clean ambient air where particulate matter deposited thereon by dirty gas may be removed to maintain the detector at a high degree of operating efficiency.