In electrical and safety engineering, hazardous locations are places where fire or explosion hazards may exist. Sources of such hazards include gases, vapors, dust, fibers, and flyings, which are combustible or flammable. Electrical equipment installed in such locations could provide an ignition source, due to electrical arcing, or high temperature. Standards and regulations exist to identify such locations, classify the hazards, and design equipment for safe use in such locations.
A light switch may cause a small, harmless spark when switched on or off. In an ordinary household this is of no concern, but if a flammable atmosphere is present, the arc might start an explosion. In many industrial, commercial, and scientific settings, the presence of such an atmosphere is a common, or at least commonly possible, occurrence.
Equipment can be designed or modified for safe operation in hazardous locations. The two general approaches are:
1. Intrinsic safety
Intrinsic safety, also called non-incendive, limits the energy present in a system, such that it is insufficient to ignite a hazardous atmosphere under any conditions. This includes low both power levels, and low stored energy. Common with instrumentation.
2. Explosion proof
Explosion-proof or flame-proof equipment is sealed and rugged, such that it will not ignite a hazardous atmosphere, despite any despite sparks or explosion within.
- Several techniques of flame-proofing exist, and they are often used in combination:The equipment housing may be sealed to prevent entry of flammable gas or dust into the interior.
- The housing may be strong enough to contain and cool any combustion gases produced internally.
- Enclosures can be pressurized with clean air or inert gas, displacing any hazardous substance.
- Arc-producing elements can be isolated from the atmosphere, by encapsulation in resin, immersion in oil, or similar.
- Heat-producing elements can be designed to limit their maximum temperature below the autoignition temperature of the material involved.
- Controls can be fitted to detect dangerous concentrations of hazardous gas, or failure of countermeasures. Upon detection, appropriate action is automatically taken, such as removing power, or providing notification.
Here we focus on the enclosure method in TLS to keep the electrical equipment inside. TLS designs and manufactures the containerised solutions with intelligent control system, hazardous gas detecting system, fire & gas system following IEC 60079-13 standards.
IEC 60079-13:2017 gives requirements for the design, construction, assessment, verification and marking of rooms used to protect internal equipment:
– located in a Zone 1 or Zone 2 or Zone 21 or Zone 22 explosive atmosphere without an internal source of gas/vapour release and protected by pressurisation;
– located in a Zone 2 explosive atmosphere with or without an internal source of gas/vapour release and protected by artificial ventilation;
– located in a non-hazardous area, containing an internal source of gas/vapour release and protected by artificial ventilation;
– located in a Zone 1 or Zone 2 or Zone 21 or Zone 22 explosive atmosphere containing an internal source of gas/vapour release and protected by both pressurisation and artificial ventilation.