There are areas that are extremely hazardous like oil refineries, chemical plants and paint shops where a small spark is enough to ignite a fire or lead to an explosion. These places generally have special technologies in place, but in spite of that hazardous explosions can take place even if there is a slight carelessness.
The designing of these places referred to as “hazardous locations” has strict guidelines to adhere to. If electrical equipment needs to be used or installed in such locations where the combustible vapours or gases are already present then a prescribed set of guidelines need to be followed. These parameters when followed help the workforce and the persons who stay in the vicinity of such places to stay safe in case of explosion eventualities.
Such hazardous locations require special equipment like explosion proof control panels to be installed the guidelines for which are specified in explosion proof classification.
This special equipment generally falls under two broad categories:
- The explosion proof equipment
- The intrinsically safe equipment
Explosion Proof Technique
In this technique, which is also called explosion containment method, the explosion proof enclosures are designed in such a manner that if explosion happens, it remains confined in a particular area. Thus, the material used for the construction of these enclosures is usually heavy duty like steel or aluminium.
The Designing Principles Required
- The enclosures must be really sturdy.
- The explosion proof panels must be capable of withstanding highpressure explosions.
- Servicing of the devices should be done only by trained personnel making use of proper tools.
Limitations of theTechnology:
- Using stainless steel or aluminium for making enclosures results in them being really expensive.
- In humid atmosphere, condensation causes problems inside the enclosures.
- The heavy weights of these enclosures can cause complications during the installation process.
- If any change needs to be implemented at the later stage then it is difficult to carry.
- If the inspection deadlines are not followed diligently then safety is compromised.
The Intrinsically Safe Technique
This method (also called prevention method) works in a completely different manner. It is engineered in such a way that no ignition or explosion happens in case of a fault in the electrical circuit. The wiring here is done in such a manner that temperature remains below the threshold required to cause an ignition.
Limitations and Benefits of Intrinsically Safe Technique
- The power quantity here is regulated using intrinsic security barriers, but the technique can only be used on devices that require low power for operation.
- The installation is easy as light materials are used for enclosure unlike explosion proof technique, but then it cannot withstand any harsh environmental condition or explosion.
- The accessories used in this method are cheap.
- During the maintenance or if calibration required, there is no need to switch off the power.
Both the methods have their pros and cons. Depending on the power requirement of the plant, the decision should be taken.