下水道和化粪池内可燃气体浓度预警模式研究

Study on Early Warning Mode of Flammable Gases Concentration in Urban Sewers and Septic Tanks

建立下水道和化粪池气体安全监控系统,实现可燃气体浓度超限预警是预防和减少下水道和化粪池气体爆炸事故的有效方式。针对现有气体安全监控系统存在的频繁报警与"误报"现象,通过现场调研和数据收集,分析重庆市主城区已发生气体爆炸事故以及重庆市南岸区一年来的监测数据,建立了可燃气体浓度预警模式:稳定模式、扰动模式和聚集模式,并建立了相应的判别标准。预警模式判别标准基于可燃气体浓度变化趋势判别式,若从某一采样时刻起,连续3次出现后一时刻的采样浓度大于前一时刻的现象,即判定为可燃气体浓度有增加趋势。通过该判别标准,至少能使现有系统报警次数减少50%,从而提高气体监控预警系统的可靠性和有效性。

The establishment of gas safety monitoring system of sewers and septic tanks to achieve off-gauge early warning of flammable gases concentration is an effective way to prevent and reduce gas explosion accidents. This study addresses frequent alarm and false alarm phenomena in gas monitoring system by field investigation and data collection of gas explosions in metropolitan Chongqing. Also, data from Nan＇ an District was collected for one year and the early warning modes of flammable gases concen- tration were established： stability mode, perturbation mode and accumulation mode. Discrimination standards were determined. The discrimination standard was based on concentration trends of flammable gases. If the concentration at a subsequent moment is consistently three times higher than that at its preceding moment during a sampling period, an increasing trend of flammable gases concentration is marked. According to this discrimination standard, the alarm frequency of the existing gas safety monitoring system can be reduced by at least half, improving the system reliability and validity.