How to set up the gas alarm for gas with dual flammable and toxic properties
In some production workshops or storage tank areas, there are usually some toxic gases, such as methanol, benzene, and carbon monoxide. When configuring the gas alarm in the relevant place, usually according to the relevant provisions of GB50493 "Petrochemical Combustible Gases and Toxic Gas Detection and Alarm Design Specifications", the flammable and toxic gas only needs to be equipped with a toxic gas alarm. However, according to the actual operation process, the toxic gas detection alarm value is low for the general factory area where there is a running drip, and the slight leakage is the alarm. In order not to affect production, the operator simply turns off the alarm, which actually brings greater hidden dangers.
For example, methanol gas, if treated as a toxic gas, short-term exposure to an allowable concentration of 50mg / m3, that is, the alarm value should be set at 35ppm; if treated as flammable gas, the lower explosion limit of 5.5% (V / V), the alarm value is set to 25 LEL %, That is 13750ppm, far higher than the upper limit of toxic alarm 35ppm. At this time, if it is set according to the toxic gas, it will alarm if there is a slight leak, causing some trouble to the relevant staff.
According to GBZ / T 233 toxic gas setting principle 4.1.1 "High toxic / highly toxic gas must be equipped with toxic gas alarm", there is no dispute, other toxic gases are "large discharge / easy to gather" occasions where toxic gas alarm No dispute.
In other cases, it is recommended to comprehensively assess the degree of risk by combining site conditions, meteorological conditions, operation methods of operators, inspection frequency, etc.
① Combustible gas alarms are set according to combustibility in open and well-ventilated places,
② Indoor, closed and semi-closed places where leakage gas is not easy to diffuse and people come and go frequently should be set as toxic gas alarms.
③Operators should be equipped with portable toxic gas detection alarms during sampling and inspection.
Therefore, it is necessary to set the toxic gas alarm or combustible gas alarm according to the actual situation.