What is gas group IIA IIB?
– Group IIA—Atmospheres containing propane, or gases and vapors of equivalent hazard. – Group IIB—Atmospheres containing ethylene, or gases and vapors of equivalent hazard. – Group IIC—Atmospheres containing acetylene or hydrogen, or gases and vapors of equivalent hazard.
What causes an explosive atmosphere?
Explosive atmospheres can be caused by flammable gases, mists or vapours or by combustible dusts. If there is enough of the substance, mixed with air, then all it needs is a source of ignition to cause an explosion.
What is Zone 2 area classification?
The definition of Zone 2 is a hazardous area classified as an atmosphere where a mixture of air and flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation, but if it does occur, will persist for a short period only.
Is IIB better than IIC?
Gas Groups Gas explosion protection is divided into 3 groups: IIA, IIB and IIC. Gases in Gas Group IIA require a higher ignition energy than Gas Group IIB. Gases in Gas Group IIC require the lowest ignition energy to ignite.
What is ATEX Ex H?
Ex h. Potentially explosive atmosphere – General requirements. for non-electrical devices. Protection types for gear units (mechanical units) The protection type specifies the method used for explosion protection. h (c)
What is difference between EXE and EXD?
It’s easy to think of Exe enclosures and Exd enclosures as both being explosion proof, but the different designations have slightly different meanings. Exe enclosures are deemed ‘explosion protected’ but not necessarily ‘flame proof’ Exd enclosures are ‘flame proof’ which means they should contain an explosion.
What is meant by explosive atmosphere?
An explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.
What is a flammable atmosphere?
Flammable atmosphere means an atmosphere containing more than ten percent of the lower flammable limit (LEL) of a flammable or combustible vapor or dust mixed with air. Such atmospheres are usually toxic as well as flammable.
What is difference between Zone 1 and Zone 2?
Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation; Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time.
What is explosion proof classification?
NEC ENCLOSURE CLASSIFICATIONS. Explosion-Proof Enclosure: An enclosure which can withstand the pressures resulting from an internal explosion of specified gases, and contain such an explosion sufficiently to prevent the ignition of the explosive atmosphere surrounding the enclosure (for Class I, II and III).
What class is explosion proof?
There are three classes of explosion proof lights, known as Class I, Class II, and Class III. These are the broadest sense in which explosion proof lights are distinguished from each other. The classes are then each broken down further into two separate divisions.
Which is the most hazardous gas group?
The hazard level of the gases increases from gas group IIA to IIC with group IIC being the most severe. Substances in this group can be ignited very easily with Hydrogen being the most at risk to ignition.
What can form an explosive atmosphere?
Gases, vapours, mists and dusts can all form explosive atmospheres with air. Hazardous area classification is used to identify places where, because of the potential for an explosive atmosphere, special precautions over sources of ignition are needed to prevent fires and explosions.
What are the effects of secondary explosions?
Secondary Explosions Are Catastrophic. An initial (primary) explosion in processing equipment or in areas where fugitive dust has accumulated, may dislodge additional dust or damage a collection system (such as a duct, vessel or collector). This dust, if ignited,
Can carbon dust cause an explosion?
(additives) Carbon Dust : Coal If a high concentration of wood dust becomes airborne and contacts an ignition source in a contained area, an explosion could occur. How bad could it be? Secondary Explosions Are Catastrophic.
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