The Difference Between Intrinsically Safe and Explosion-Proof Systems

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While safety is the main concern when hazardous locations and materials are involved, two different systems exist to eliminate ignition or explosions: intrinsically safe and explosion-proof. The difference between the two comes down to the difference between preventing and containing explosions.

Intrinsically safe

In an intrinsically safe system, energy is limited in the component or wiring of the pressure transmitters in an effort to prevent ignition. When this system is used, an

intrinsically safe pressure transmitter is placed in the hazardous area while the power supply to the transmitter is located in the safe area. The power to the pressure transmitter is regulated through a zener diode barrier.

Pressure transmitters including the IS-20 or IS-21, engineered by WIKA, are intrinsically safe because they are designed to operate on low power, can tolerate two internal faults without overheating, and do not use components that store enough energy for ignition. Plus, they are designed to be non-incendive, meaning they cannot store enough energy internally to cause a spark when energy is released.

Explosions cannot occur under defined failure conditions, but the system does not protect against explosions induced by mechanically induced electrical sparking, chemical reactions, radio waves, or lightning strikes. Common applications for intrinsically safe pressure transmitters include landfill sites, wastewater plants, petrochemical refineries, and natural gas wells.

Explosion-proof

If a system or component is explosion-proof, an explosion is possible, but a specifically designed enclosure keeps the flames, sparks, or hot gases from exiting the enclosure. They typically have extended treaded flanges that provide a long flame path designed to cool and contain the explosion, therefore any ignition is both contained and controlled.

The beauty of explosion-proof pressure transmitters, including the WIKA Hazardous Area Explosion-Proof Pressure Transmitter, is that they ease design concerns by isolating the three basic components of the combustion triangle – oxygen, heat, and fuel. In other words, explosion-proof pressure transmitters allow components to be placed within hazardous locations. Plus, they can also be used with systems and components requiring any amount of power.

Compared to intrinsically safe systems, explosion-proof systems are bulkier, heavier, usually more expensive, and more difficult to install. Power must be removed from explosion proof systems if they are opened in a hazardous area, often requiring a "hot permit" prior to servicing.  Intrinsically safe systems can be serviced while powered.

Contact WIKA for more information about the intrinsically safe and explosion proof pressure transmitters.

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