Hazardous Area Definitions and Classifications.

To allow for operator interface in hazardous environments, specially designed hazardous area computers or monitors must be utilized. Hazardous environments usually contain amounts of explosive gases or dust either during normal operation or during an abnormal circumstance.

The function of GE Fanuc Intelligent Platforms hazardous area computers and monitors is to provide computer controls or information while preventing or containing an explosion. This can be accomplished by protecting the operator interface system from its environment, or protecting the environment from the operator interface system.

GE Fanuc Intelligent Platforms hazardous area computers and monitors must comply with some of the most stringent safety guidelines defined by worldwide regulatory agencies. To increase the potential for global marketability, the United States has incorporated the IEC (International Electrotechnical Commission) Zone system into a parallel classification system to the traditional U.S. Class I Division system -- the U.S. Class I Zone system.

The key concepts of the IEC system include area classification, gas grouping, temperature codes, protection methods and markings. Under both the Division and Zone systems, GE Fanuc Intelligent Platforms hazardous area computers for use in explosive gas atmospheres are identified based on designations that address:

1. The likelihood that the explosive gas atmosphere is present when hazardous area computers or monitors are operating (see the Division and Zone designations in Table 1);

2. The ignition-related properties of the explosive gas atmosphere (see the Gas Group designations in Table 2);

3. The maximum surface temperature of the equipment under normal operating conditions (see the Temperature Code designations in Table 3); and

4. The protection method(s) used by the equipment to prevent ignition of the surrounding atmosphere (see the Protection Method designations in Table 4).

Defining Class I Specifications and Subgroups

Class I is part of the National Electric Code definitions of hazardous location classifications and protection techniques. The Class I classification is a segment of the basic designation which is listed by ''class'' and ''division.''

Class I locations are areas where flammable gases may be present in sufficient quantities to produce explosive or flammable mixtures. Class II locations can be described as hazardous because of the presence of combustible dust. Class III locations contain easily ignitable fibers and flyings. Division 1 designates an environment where flammable gases, vapors, liquids, combustible dusts or ignitable fibers and flyings are likely to exist under normal operating conditions. On the other hand, Division 2 is an environment where flammable gases, vapors, liquids, combustible dusts or ignitable fibers and flyings are not likely to exist under normal operating conditions. Hazardous atmospheres are further defined by ''groups.'' These include:

Group A: Atmospheres containing acetylene.

Group B: Atmospheres containing hydrogen, gases or vapors of equivalent hazard such as manufactured gas.

Group C: Atmospheres containing ethyl-ether vapors, ethylene, or cyclo-propane.

Group D: Atmospheres containing gasoline, hexane, naptha, benzene, butane, propane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas.

Group E: Atmospheres containing metal dust - including aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics.

Group F: Atmospheres containing carbon black, coal or coke dust.

Group G: Atmospheres containing flour, starch, or grain dusts.

Multiple Dangers, Multiple Solutions

GE Fanuc Intelligent Platforms hazardous area monitors and computer systems are often semi-custom designs. This level of customization is a necessity because of the sheer number of the different potential environments into which one of our systems could be introduced. There’s simply no “one size fits all” solution to this array of potential dangers.

It is also important to note that in some cases there is no need for a human machine interface, and that the monitor or system can simply serve to process and display information. In such cases, the solution may be relatively simple. However, in cases where operator input is required, the complexity of our solution greatly increases. Nevertheless, in these cases, GE Fanuc Embedded Systems is able to offer certifiable solutions, such as touch screens input devices, which allow for operator input while still isolating the system from the environment.

Because there are so many variables in both the potential environmental dangers and in the available solutions to these dangers, we make it a practice to personally engage our customers in a discussion of their unique needs before making recommendations. For information on how GE Fanuc Embedded Systems may be able to solve your hazardous area computer challenges, please contact us at 1.864.627.8800 or visit our website at www.gefanucembedded.com for a listing or local sales and service representatives.