DEVELOPMENT OF A CENTRALIZED EARLY WARNING DETECTION SYSTEM IDENTIFYING EXPLOSIVE CONDITIONS IN GRAIN HANDLING FACILITIES

摘要

This presentation discusses preliminary investigations into the feasibi1ity of early warning detection of explosive conditions and defines problem areas needing additional research or development. An integrated minicomputer-controlled detection system can continuous monitor the states of the three conditions for combustion (i.e., com bustible material, oxygen, and an ignition source) and then provide the proper response or warning. However, to be of practical value such a system should be adaptable for installation in existing as well as in new facilities and must be highly reliable and economically attractive. Also discussed is the initial work of Iowa State University on detection of aerosol or gas emissions from grain dust at temperatures well below the ignition temperature and work on photoelectric detectors to provide early warning of dust concentrations exceeding the lower explosive limit (LEL). A brief overview is given about state-of-the-art computerized monitoring systems. Eight different types of detectors are discussed including temp-erature, belt or bucket elevator slow-down, electric motor overload, ioni¬zation and combustible gas, dust concentration, electric field, humidity, and oxygen detectors. Some of these detectors are commercially available. Detailed discussions are included on the ionization, combustible gas, and dust concentration detectors. Central processing units (CPU) which monitor the outputs of these detectors are also discussed. The CPU is usually a minicomputer which is currently available and readily adaptable. Preliminary cost estimates indicate the centralized early warning system would cost approximately 3-5% of the total facility cost depending on the number of signal points required. By expanding the scope of this work, considera¬tion can be given to the development of new and improved dust ignition proof or intrinsically safe detectors which will optimize and assure early warning via an integrated minicomputer system.