Working in hazardous locations increases the chances of an explosion happening so it is important to get rid of the components that cause ignition. Here are three basic methods of protection: explosion containment, prevention and segregation.
Explosion Proof Enclosures – This sole technique allows the explosion to happen but limits it to an area, preventing any propagation to the surrounding atmosphere. This is the technique on which explosion-proof areas are based.
Prevention – This technique controls the amount of energy - both thermal and electrical -maintaining safe levels under all conditions. Intrinsic safety is the most representative technique.
Segregation – This technique works toward isolating hot surfaces and electrical parts from igniting and exploding. The technique is comprised of different methods such as encapsulation, pressurization, etc.
- Explosion Proof Enclosures: Explosion-proof enclosures, the sole technique based on containing an explosion, allows for the source of ignition to come into contact with the flammable air compound. After which, the explosion is allowed to happen but must be contained in a specially-made explosion-proof enclosure to handle the extra force of the contained explosion. This eliminates the spread of the explosion and its byproduct into the atmosphere. This is only possible if the openings into the explosion-proof enclosure are very small. The concept is that the consequent gas jet that comes out of the enclosure is quickly cooled with the enclosure’s heat conduction and the dilution and expansion of the hot gas in the colder external atmosphere. This is contained with the use of heavy duty enclosures and conduit. The enclosure is made of a sturdy mechanical construction and the highest surface temperature is lower than the ignition temperature of the gas, present in the location it is installed in. Bear the specific standards of the regulations when designing or buying an explosion-proof enclosure.
- Prevention Method: This technique is centered on a segregation concept which does not allow flammable gases to come into contact with the enclosure containing electrical materials, as it can cause ignition at high temperatures. Therefore, a protective gas is kept within the enclosure at a higher pressure – higher than typically found in the atmosphere. Meanwhile, the internal overpressure will stay constant with or without a constant flow of protective gas. The enclosure does need a certain amount of tightness because the pressure supported is not very high. To keep constant pressure, the protective gas supply has to compensate when in use for any leakage and access by personnel where it’s possible.Flammable gas can remain in the enclosure even after the pressurization system is turned off, making it vital to remove it by adding more protective gas to ensure nothing ignites when restarting equipment. The electrical apparatus used when the maximum or the minimum temperature occurs is protected with another form of protection.This purging method does not depend on the type of gas but rather the enclosure it is kept in. This prevents the flammable gases from coming into contact with the electrical component that can heat up and lead to ignition.
- Segregation: This technique separates the electrical parts that lead to the ignition of the flammable gases due to overheating. Unfortunately, it is not recognized by all standards.Encapsulation prevents contact with flammable air compound and is used to protect the electrical circuits not made up of any moving parts. Encapsulation is needed for other protection techniques.Simply connecting wiring is not enough as the wires have to connect according to safety specifications. Understand the hazardous locations to ensure you understand its benefits.
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