When monitoring flammable gas and or toxic gas leaks in the area of process plants and storage and transportation facilities (including Class A gas and liquefied hydrocarbon storage tank farms, Class A and B liquid storage tank areas, loading and unloading facilities, filling stations, etc.),Flammable gas detectors(detector) and toxicgas detector(detector) shall be set in accordance with the following provisions.
1. When flammable gas or toxic gas leaks, the flammable gas concentration can reach 25%LEL, but when the maximum allowable toxic gas concentration is not reached, Flammable gas detectors should be set;
2. When toxic gas or flammable gas leaks, the toxic gas concentration can reach the maximum allowable concentration, but when the flammable gas concentration cannot reach 25%LEL, toxic gas detectors should be installed;
3. In the place where flammable gas and toxic gas exist at the same time, when the flammable gas concentration may reach 25% LEL and the toxic gas concentration may reach the maximum allowable concentration, flammable gas and should be set separatelytoxic gas detector；
4. When the same gas is both flammable and toxic, only toxic gas detectors should be set up; [SH3063-1999] Process units and storage and transportation facilities (including Class A gases, liquefied hydrocarbons, and Class A gases) that produce or use flammable gas. Flammable gas detection and alarm devices are set up in Class A liquid storage tank areas, loading and unloading facilities, gas filling stations, etc., and two new areas.
In the process equipment and storage and transportation facilities that generate or use toxic gas, toxic gas detection and alarm devices shall be set up in accordance with this specification.
1. Among themflammable gasor toxic gas leakage may reach 25% LEL, but toxic gas cannot reach the maximum allowable concentration, flammable gas detection alarm should be set;
2. When toxic gas or flammable gas leaks, toxic gas may reach the maximum allowable concentration, but when flammable gas cannot reach 25% LEL, a toxic gas detection alarm device should be set up;
3. Both flammable gas and toxic gas should be equipped with toxic gas detection and alarm devices;
4. When flammable gas and toxic gas exist at the same time, flammable gas and should be settoxic gasThe detection and alarm device is the same time.
Note: The division of Zone 2 and Additional Zone 2 is described in the Code for the Design of Electrical Installations in Explosion and Fire Hazardous Environments (GB 50058).