Songbei QA | How to divide the hazardous area of explosive gas atmosphere?
Date:2022-04-02 16:59:08 Views:305
A: (1/2)
No. 1:
Explosive gas atmospheres should be classified according to the following provisions according to the frequency and duration of the occurrence of explosive gas mixtures:
(1) Zone 0: an environment where explosive gas mixtures appear continuously or for a long time;
(2), Zone 1: the environment where explosive gas mixture may appear during normal operation
(3) Zone 2: An environment where an explosive gas mixture is unlikely to occur during normal operation, or an environment where an explosive gas mixture exists only for a short time even if it occurs.
No. 2:
When one of the following conditions is met, it can be classified as a non-explosive hazardous area:
(1) Areas where there is no release source and there is no possibility of intrusion of flammable substances;
(2) The highest possible concentration of flammable substances does not exceed 10% of the lower explosion limit;
(3) Near the equipment that uses an open flame in the production process, or near the equipment where the surface temperature of the hot parts exceeds the ignition temperature of the flammable substances in the area;
4. Outside the production facility area, the overhead pipeline area for conveying flammable substances is set in the open air or in the open, but the valve position shall be determined according to the specific situation.
The release source shall be classified according to the frequency and duration of the release of flammable substances, and shall meet the following requirements.
(1) Continuous-level release sources: release sources that are expected to be released for a long time or are frequently released in a short period of time. Similar to the following conditions, it can be classified as a continuous release source:
1. Surfaces of flammable liquids in fixed-top tanks not covered with inert gas;
2. Surfaces of flammable liquids that are in direct contact with space, such as oil and water separators;
3. Free vents and other orifices that release vapors of flammable gases or flammable liquids into the space frequently or over long periods of time.
(2) The first-level release source: the release source that is expected to be released periodically or occasionally during normal operation. Similar to the following situations, it can be classified as a first-level release source:
1. Seals of pumps, compressors and valves, etc. that release flammable substances during normal operation;
2. Drainage systems installed on containers containing flammable liquids that release flammable substances into the space during normal operation;
3. Sampling point where flammable substances are released into space during normal operation.
(3) Second-level release source: it is not expected to be released under normal operation, and even if it is released, it is only an occasional short-term release source. Similar to the following situations, it can be classified as a second-level release source:
1. Seals of pumps, compressors and valves that release flammable substances cannot occur during normal operation;
2. Flanges, connections and pipe joints that cannot release flammable substances during normal operation;
3. Safety valves, vents and other orifices that cannot release flammable substances into the space during normal operation;
4. Sampling points where flammable substances cannot be released into space during normal operation.
(4) Multi-level release source: a release source composed of the above two or three levels of release sources.
No. 4:
Ventilation in explosion-hazardous areas, when the air flow can quickly dilute the flammable substances to below 25% of the lower explosion limit value, it can be regarded as well-ventilated.
When mechanical ventilation is used in one of the following situations, the influence of mechanical ventilation failure can be ignored:
1. Standby independent ventilation systems should be provided for enclosed or semi-enclosed buildings;
2. In the event of a ventilation failure, set up precautions such as automatic alarms or stop the process flow to ensure that the release of flammable substances is prevented, or precautions to de-energize electrical equipment.
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