Common Malfunctions in the Use of Combustible Gas Detectors
Combustible gas detectors are mainly applied in the petrochemical industry involving flammable gases, such as gas supply, petroleum and chemical sectors. They are used to detect dangerous gas leaks in indoor and outdoor environments, serving as vital equipment to safeguard personal safety and production security. Once a combustible gas leak is detected at a specific location, the detector converts the gas signal into voltage or current signals and transmits them to the alarm controller. The instrument then automatically displays the concentration value relative to the Lower Explosive Limit (LEL) of the combustible gas. Upon receiving the audible and visual alarm, operators can implement safety measures to avert fire and explosion accidents.
Nevertheless, many improper practices exist when selecting various gas detectors, mainly reflected in the following two aspects: ① More emphasis is placed on the detection of combustible gases than toxic gases; ② Greater attention is paid to gases that cause acute poisoning than those leading to chronic poisoning.
Bloody lessons from numerous explosion accidents caused by flammable gas leaks have led industries to attach great importance to combustible gas monitoring. In almost every petrochemical and chemical plant, the majority of hazardous gas detectors are LEL monitors. However, relying solely on LEL detectors is far from sufficient to fully protect workers' safety and health. Admittedly, most volatile hazardous substances are combustible, yet catalytic combustion LEL detectors are not the optimal choice for all flammable gases. They are calibrated primarily for methane, with poor response to other compounds. As a result, the measurable LEL reading for gases other than methane is far higher than their permissible exposure limits.
Prudent evaluation based on actual working conditions is required for the proper deployment of combustible gas detectors: ① Determine the diffusion path of leaked combustible gas according to on-site airflow, wind direction and other ambient parameters. ② Analyze the specific leakage mode at each release point, and work out corresponding budget and disposal plans based on different scenarios. ③ Establish a three-dimensional gas diffusion model by referencing the density of leaked gas and air circulation patterns, so as to formulate a reliable layout scheme. ④ In open areas with poor ventilation, freely diffusing combustible gases may easily reach or approach the explosive concentration range; such positions shall be set as key safety monitoring points. ⑤ Identify all potential leakage points on monitored equipment, and assess the severity of leaks in light of gas emission direction and pressure.
