Explosion proof grade of explosion-proof electric valve
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2019-03-18
How to distinguish and choose the explosion-proof grade of explosion-proof electric control valve? First of all, let's understand explosion. Explosion is a material from one state, after physical or chemical changes, suddenly changes into another state, and releases huge energy. The rapid release of energy will cause the surrounding objects to suffer severe impact and damage.
Three conditions for explosion
1) Explosive substances: substances that can react with oxygen (air), including gases, liquids and solids. (gas: hydrogen, acetylene, methane, etc.; liquid: alcohol, gasoline; solid: dust, fiber dust, etc.) 2) Oxygen: air. 3) Ignition source: including open fire, electrical spark, mechanical spark, electrostatic spark, high temperature, chemical reaction, light energy, etc.
Why explosion proof
Explosive substances: many production sites will produce some combustible substances. There are explosive substances in about two-thirds of underground coal mines, and more than 80% of production workshops in chemical industry. Oxygen: oxygen in the air is everywhere. Ignition source: a large number of electrical instruments are used in the production process. Various friction sparks, mechanical wear sparks, electrostatic sparks, high temperature, etc. are inevitable, especially when the instrument and electrical fault occurs.
Objectively, many industrial sites meet the explosion conditions. When the mixed concentration of explosive substance and oxygen is within the explosion limit range, if there is an explosion source, the explosion will occur. Therefore, it is necessary to take explosion-proof.
Format of explosion proof sign:
Ex (ia) ⅡC T4
Explosion proof mark explosion-proof grade gas group temperature group explosion-proof grade Description:
Class Ia: electrical equipment that cannot ignite explosive gas mixture in normal operation, one fault and two faults.
In normal operation, the safety factor is 2.0;
When one fault occurs, the safety factor is 1.5;
For two faults, the safety factor is 1.0.
Note: the contact with spark must be equipped with flameproof enclosure, air tight enclosure or double safety factor.
IB grade:
Electrical equipment that cannot ignite explosive gas mixtures in normal operation and a fault.
In normal operation, the safety factor is 2.0;
When a fault occurs, the safety factor is 1.5.
In normal operation, the contacts with spark must be protected by flameproof or air tight enclosure, and there should be measures for self display of faults. The safety factor of one fault is 1.0.
According to the ignition energy, small ignition temperature and the time period of the existence of explosive dangerous gas in the factory or mining area, the explosion-proof signs and explosion-proof forms of on-site explosion-proof equipment are determined.
Format of explosion-proof sign:
Ex: explosion proof mark (IA): explosion proof grade Ⅱ C: Gas Group T4: temperature group
Explosion proof grade: ia grade:
Electrical equipment in which neither one fault nor two faults can ignite an explosive gas mixture during normal operation. In normal operation, the safety factor is 2.0; in case of a fault, the safety factor is 1.5; in normal operation, the contact with spark must be added with flameproof enclosure or air tight enclosure or double the safety factor.
IB grade:
Electrical equipment that can not ignite explosive gas mixture in normal operation and one fault. In normal operation, the safety factor is 2.0; in case of a fault, the safety factor is 1.5; in normal operation, the contact with spark must be protected by flameproof enclosure or air tight enclosure, and there are measures for fault self display.
