Q&A: Fiber Optics in Explosive Environments Ask Mike Chairman ANSI B11.19 1-888-3-SENSORS Description: An environment that is potentially explosive is one with the right combination of fuel, a source of ignition and an oxidizer (oxygen). The PICO-GUARD fiber optic safety technology is ideal for use in explosive environments because the fiber optic elements do not provide a source of ignition in an explosive environment but will provide Category 4 safety in a variety of applications. Q: What is the difference between an “explosive” and a “hazardous” area? A: Industries that normally deal with potentially explosive atmospheres use the terms “explosive” and “hazardous” interchangeably. For our purposes, let’s use the following terms to refer to personnel safety: hazardous area, hazardous location, or hazardous situation. A potentially explosive situation, let’s describe as an explosive environment or explosive atmosphere. Q: Where are explosive environments typically found? A: Here are just a few applications: Paint booths Paint/stain manufacturers Gaseous fill (e.g. cigarette lighters) Cosmetics/perfume manufacturers Film/web processes Chemical processes Battery manufacturers Pharmaceuticals Semiconductor industry Q: What can I do to prevent explosions? A: The best way to do this is to eliminate or limit the source of energy, thus preventing ignition. Methods such as Intrinsic Safety, the use of fiber optics or pneumatic systems are ways to limit energy. Explosion-proof enclosures can be used to contain the explosion. Purged and pressurized enclosures can be used to prevent build-up. Q: What is considered fuel? A: Fuel, or flammable materials, may take the form of flammable gas, vapors, combustible dust or combustible fibers. For more information, consult Articles 500 and 505 of the National Electrical Code (NEC) which cover the requirements for electrical equipment and wiring in explosive environments. Q: What are sources of ignition? A: Flammable materials may be ignited by thermal energy or a spark. Some examples include: hot surfaces, open flames, electrical arcing, electrostatic discharge, lighting, electromagnetic radiation, or chemical reactions. Q: The PICO-GUARD is an electronic device. Won’t it provide a source of ignition when it turns on or off? A: NO! At least not the fiber optic portion. Optical fibers are basically light conduits, piping a controlled amount of red light from the controller to the point of guarding and back. Because the optical energy is limited it will not provide a source of ignition, therefore the optical elements of the PICO-GUARD can be located within the explosive environment. However, the PICO-GUARD controller and any other electrical device interfaced to it must be located away from the explosive environment or within an explosion-proof housing. Q: What makes the PICO-GUARD safe? A: The PICO-GUARD is safe because of the following: It uses the same self-checking, redundant microprocessor technology that you'd find in a Type 4 / Category 4 safety light screen. Emitter LEDs and receiver cells are physically located and shielded so an internal optical short circuit will not occur. Also, the light from one optical channel will not be recognized by another optical channel. Externally, the light transmitted through the optical fiber cannot affect or be affected by external sources of electrical noise. All failure modes result in a stop sign to the machine, thus complying with Control Reliability and Type 4 / Category 4 requirements.

Q: The PICO-GUARD is labeled “Class 1 / Division 1”. What does that mean? A: The primary style of describing explosive environments in the U.S. is based on Class/Division/Groups, as described in Articles 500 and 505 of the National Electrical Code (NEC). Class refers to the types of fuels that may be present in an environment. The PICO-GUARD may be used in the presence of Class 1 types of fuels which include gases or vapors. Division refers to the possibility of ignitable concentrations of fuel being present in an environment. Division 1 means that the PICO-GUARD can be in an environment where ignitable concentrations of fuel may be present or likely to be present during normal operation, maintenance, or under fault conditions. Q: And to what does “Zone 0 / Group IIC” refer? A: In Europe, the ATmosphere EXplosible (ATEX) Directive cover the requirements for electrical equipment and wiring in explosive environments, and is based on Zones/Groups. Zone is the possibility of ignitable concentrations of fuel being present in an environment. Zone 0 means that the PICO-GUARD can be in an environment where ignitable concentrations of fuel are present continuously, frequently, or for long periods of time. Group is the location and specific type of fuel/ignition capabilities. In the case of the PICO-GUARD, it may be located in areas where acetylene and hydrogen might be present. Q: In what explosive environments has the PICO-GUARD been certified to be used? A: The PICO-GUARD has been certified for use by FM, CSA, and NEMCO to the ATEX directive for the following: Class I, Division 1, Groups A,B,C&D (Gases) Class I, Division 2, Groups A,B,C&D (Gases) Zone 0, Group IIC (Gases) Zone 22 (Dust, Not normally present) Q: Can the PICO-GUARD be used to protect a hand in a point-of-operation guarding application? A: Yes, with the 12mm safety fiber points (SFP series). See PICO-GUARD Application and Design Guide or Contact Banner for more information. Q: What other type of applications can the PICO-GUARD solve? A: Some other applications include monitoring interlocked guards with the safety fiber interlock switches, and monitoring access and perimeter guards with the safety fiber points and safety fiber grids. Q: What are my options with fiber optic safety technology? A: You can use the PICO-GUARD as an interlock device, or you can use the grids and points to detect an individual or in equipment protection applications. You can also get these optical components in a variety of different housing styles from impact-resistant polycarbonate plastic to stainless steel for rugged environments. Related Links: Download the PICO-GUARD Application and Design Guide here. Visit the PICO-GUARD product page. Get more general info about Banner fiber optic safety systems. Take some tutorials on iKnow Machine Safety.