What Does Intrinsic Safety (IS) Mean?
Intrinsic safety is an explosion prevention technique used to ensure safe operation of electrical equipment in a hazardous area. It uses low-energy signaling technique by limiting the energy within the equipment well below the energy required to initiate an explosion. The equipment and control circuits can still operate with low currents and voltages that are adequate for its operation.
Safeopedia Explains Intrinsic Safety (IS)
Intrinsic safety prevents sparks and heat from being generated from electrical equipment, devices and instruments that otherwise would have initiated an explosion in a hazardous space. Intrinsically safe equipment uses low current and low voltage, which is insufficient to create such sparks and heat. Hazardous spaces may belong to the following, but are not limited to petrochemical refineries, storages, transports, mines, painting, grain, waste water, printing, distilling, pharmaceutical, brewing, cosmetics, plastics and utilities. Sparks may cause explosions to acetylene, hydrogen, ethylene, propane, metal dust, carbon dust, flour, starch, grain, pyrotechnics and explosives. Hot surfaces may cause explosions when in the vicinity of explosives, gas and vapor mixtures. Intrinsically safe equipment cannot replace explosion proof devices, but can provide significant cost savings in installation and maintenance.
Intrinsic safety is achieved by using Zener Diodes (to limit voltage), resistors (to limit current) and a fuse (to cut off electricity). Equipment or devices that may be made intrinsically safe include: switches, two wire transmitters, thermocouples, resistance temperature detector (RTDs), strain gages, pressure/flow and level switches, converters, solenoid valves, proximity switches, infrared temperature sensors, potentiometers, LED indicating lights, magnetic pickup flow meters. This equipment must first be approved for use in an intrinsically safe system by 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).