In numerous sectors, a variety of hazerdous area solutions are employed to safeguard process and control equipment that is used in dangerous environments. The fundamental objective of these safety measures is to stop an explosion by getting rid of one of the fire triangle’s elements.
In the process control sector, the following hazardous area protection techniques are most frequently used:
- Energy limitation
1. Containment methods
An explosion is kept inside the equipment enclosure using the containment method. Sparks or flames won’t escape into the dangerous atmosphere and start another fire or explosion, as a result. With spark-producing components like switch gears, control boards, or transformers, containment is frequently used. (Ex d) denotes an explosion-proof enclosure.
Explosion-proof Enclosures (Ex d)
Equipment elements that could spark or otherwise ignite an explosive atmosphere are encased in explosion-proof (or flameproof) enclosures. The following requirements must be met by explosion-proof enclosures:
- All enclosure joints that open to the outdoors must be flameproof.
- There must be enough strength in the enclosure to resist an interior explosion without rupturing or permanently deforming.
- The surface temperature of the enclosure must never be higher than the temperature at which the ambient gas-air mixture will ignite.
- Users should take the material’s thickness, corrosion resistance, impact strength, and porosity into account when choosing an explosion-proof material.
2. Energy limitation
Additionally, explosions can be avoided by extracting enough energy from fleeing gasses to keep it below the minimum ignition energies of all flammable gasses and combustible dusts in the surrounding atmosphere.
An explosion won’t happen if energy levels are kept below certain thresholds. The most popular technique for energy restriction is to utilize intrinsically safe barriers, which are frequently seen in process transmitter installations, or to design a device to be inherently safe.
Equipment that is intrinsically safe contains the marking or symbol (Ex i)
Intrinsic Safety (Ex i)
By restricting the discharge of enough electrical energy to ignite explosive gasses in the atmosphere under normal or predetermined fault conditions, intrinsically safe (I.S.) machinery and wiring prevent explosion.
An externally installed I.S. The barrier (often provided by the installer) limits the amount of energy that is permitted into the dangerous site. I.S. methods have several benefits, including:
- Safe system maintenance requires fewer operator actions.
- The equipment is simpler to maintain and repair.
Maximum restrictions for voltage, current, capacitance, inductance, and power supply are allocated to I.S. devices. The amount of energy storage permitted in the I.S. The circuit is based on the magnitude of these factors.
The avoidance approach guards against explosions by utilizing machinery or portions of machinery that do not arc or spark during routine use, hence preventing the occurrence of the ignition source. Ex. e indicates equipment with greater safety, while Ex. n indicates non-sparking equipment.
Increased Safety (Ex e)
Perhaps the most frequently employed form of protection is increased safety. Increased safety equipment does not include regularly sparking components in its design or production. Manufacturers create various parts with the following features to drastically lower the possibility of fault circumstances that could result in ignition:
- Lowering and managing workplace temperatures
- Making certain trustworthy electrical connections
- Increasing the efficiency of the insulation
- Lessening the likelihood that contaminants such as dirt and moisture may enter the system.
Terminal and connection boxes, control boxes, and light fixtures are a few applications with greater safety that are frequently used.
Non-Sparking Equipment (Ex n)
In order to increase reliability, extra care is taken when connecting and wiring non-sparking equipment. Arcs, sparks, or hot surfaces are not produced by the device when it is in regular use. In hazardous environments, three-phase induction motors are frequently utilized with non-sparking equipment.