When we come into contact with many companies, we have found that many companies believe that the classification of hazardous areas in explosive gas environments is based on the reserves or properties of hazardous substances, and are divided into "Zone 0", "Zone 1", and "Zone 2". However, this is actually a mistaken understanding:
The classification of hazardous areas in explosive gas environments is mentioned in the standard documents "GB 50058-2014 Code for Design of Electrical Installations in Explosive Hazardous Environments" and "AQ 3009-2007 Code for Electrical Safety and Explosion Protection in Hazardous Areas". However, the "AQ 3009-2007 Code for Electrical Safety and Explosion Protection in Hazardous Areas" also references relevant viewpoints from the "GB 50058-2014 Code for Design of Electrical Installations in Explosive Hazardous Environments".
Firstly, the classification of hazardous areas in explosive gas environments is based on the frequency and duration of the occurrence of explosive gas mixtures, which are divided into Zone 0, Zone 1, and Zone 2. The zoning should comply with the following regulations:
Zone 0 should be an environment where explosive gas mixtures occur continuously or for a long time;
Zone 1 should be an environment where explosive gas mixtures may occur during normal operation;
Zone 2 should be an environment where explosive gas mixtures are unlikely to occur during normal operation, or where explosive gas mixtures only exist for a short period of time if they do occur.
It can be seen that the classification of hazardous areas in explosive gas environments is actually based on the duration of the presence of hazardous substances in the area, rather than the storage capacity of the substances.
Under certain specific conditions, even if there are hazardous substances in the area, it can still be classified as a non hazardous area. If one of the following conditions is met, it can be classified as a non explosive hazardous area:
Areas without release sources and where it is impossible for flammable substances to invade;
The maximum concentration of combustible substances that may occur does not exceed 10% of the lower explosive limit;
Near equipment that uses open flames during the production process, or near equipment where the surface temperature of hot components exceeds the ignition temperature of combustible materials in the area;
Outside the production facility area, there are overhead pipeline zones for transporting flammable substances that are set up outdoors or in an open manner, but their valve locations are determined according to specific circumstances;
When the hazardous area is judged to be "well ventilated", the hazard level of the explosion-proof area can be reduced at discretion; When there is poor ventilation, the danger level of the explosion-proof area should be increased.
The following places can be designated as well ventilated places:
? Outdoor spaces;
? Open type buildings, with openings in the walls and roofs of the building, whose size and location ensure that the ventilation effect inside the building is equivalent to that of outdoor areas;
? Non open buildings with permanent openings to provide natural ventilation conditions;
? For enclosed areas, provide at least 0.3 cubic meters of air per minute per square meter of floor area or at least 6 air changes per hour.
When using mechanical ventilation, the following situations may not be considered as the impact of mechanical ventilation failure:
? Install backup independent ventilation systems in enclosed or semi enclosed buildings;
? When the ventilation equipment malfunctions, preventive measures such as setting automatic alarms or stopping the process flow to prevent the release of flammable substances, or taking preventive measures to power off the equipment.
In summary, the classification of hazardous areas in explosive gas environments is based on the duration of the existence of hazardous substances. Under specific conditions, the hazard level of the area can be reduced or even classified as non explosive hazardous areas.
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