Intrinsic safety is an explosion prevention technique used to ensure safe operation of electrical equipment in a hazardous area. This technique uses a low-energy signalling technique that reduces the energy within the equipment to below that required to initiate an explosion, whilst maintaining an energy level this is an be used for its operation.
What is a hazardous area?
A hazardous or explosion-prone relates to an environment that has vast amounts of flammable substances such as combustible particles, gases, vapor. Hazardous industrial areas include oil refineries, mining, distilleries and chemical plants. The main safety issue in these industrial scenarios is that of flammable vapours and gases. This is because when they are mix with oxygen within the air, they can establish an explosion-prone environment. Food processing factories, grain handling facilities, recycling operations, and even flour mills generate combustible dust, which is why these are classed as too hazardous locations. Hazardous places are classified in terms of zones on the basis of the frequency and duration of the occurrence of an explosive atmosphere. Areas subject to flammable gas hazards are classified as either Zone 0, Zone 1 or Zone 2.
How does it work?
Intrinsic safety prevents sparks and heat from being generated from any electrical equipment, devices or instruments that otherwise ay have initiated an explosion in a hazardous area. Hazardous spaces may belong, but are not limited to, to the following: petrochemical refineries, mines, agriculture grain storage, wastewater, distilling, pharmaceutical, brewing, and utilities.
Intrinsic safety is achieved with the use of a Zener Diodes which limits voltage, resistors that limit the current and a fuse to cut off electricity. Equipment or devices that may be made intrinsically safe must first be approved for use in an intrinsically safe system through a competent authority, such as the National Fire Protection Agency (NFPA), the Canadian Standards Association (CSA), Underwriters Laboratories (UL), Factory Mutual (FM), National Electric Code (NEC), and the Instrument Society of Measurement and Control (ISA).
The advantages of Intrinsic Safety
The main advantage is that it provides a solution to all problems that occur in a hazardous area regarding equipment. It prevents the cost and bulk of explosion proof enclosures, with additional cost savings as a result of the ability to use standard instrumentation cables. Additionally, the maintenance and diagnostic work can be performed without shutting down production and ventilating the work area.
Levels of protection
Intrinsic safety relates to three levels of protection, ‘ia’, ‘ib’ and ‘ic’ that aim to balance the probability of an explosive atmosphere, assessing the probability of whether that is an ignition capable situation that may occur.
Offers the highest level of protection and any equipment that is given this level is generally considered adequately safe for use in the most hazardous locations (Zone 0) with two faults.
This level is considered adequately safe with one fault is considered safe for use in less frequently hazardous areas (Zone 1).
This level is given for ‘normal operation’ with a unity factor of safety is generally acceptable in infrequently hazardous areas (Zone 2).
Level of protection
Normal Zone of use
To note, although it is normal for a whole system to be allocated a level of protection, it is also possible for different parts of the system to have different levels of protection.