National Electric Code

Each segment of the insulated wire and cable industry has its own set of standards, and cables are built to conform to specifications provided by a large variety of technical associations such as The Institute of Electrical Electronic Engineers (IEEE), The Insulated Cable Engineers Association, (ICEA), National Electrical Manufacturers Association (NEMA), Underwriters Laboratories (UL), Rural Electrification Administration of the U.S. Department of Agriculture (REA), Association of Edison Illumination Companies (AEIC), MiUtary Specifications of the Department of Defense (MIL), American Society for Testing and Materials (ASTM), National Electrical Code (NEC), etc. 

Each plant or laboratory should adopt definite rules and procedures for electrical iastahations and work. All iastahations should be ia accordance with the National Electrical Code (NEC) for the type of ha2ard, eg. Class I flammable gas or vapor Class II organic, metallic, or conductive dusts and Class III combustible fibers and the degree of process containment, eg. Division 1 open and Division 2 closed (67). Regardless of the flammabiUty of the materials ia the iastaHed operations, changes ia procedure involving use of such materials often occur, sometimes without concurrent alteration of the electrical iastaHation. 

National Electrical Code, No. 70, National Fire Protection Association, Boston, Mass., 1993 Electrical Installations in Chemical Plants, No. 497A, 1992. Electrical Safety Practices, Monograph Nos. 110—113, Instmment Society of America, Research Triangle Park, N.C., 1965—1972 Electrical Safety Abstracts, 4th ed., 1972. 

National Electric Code,No. 70, National Fire Protection Assn., Boston, Mass., 1971. 

Electiical classification. Article 500 of the National Electric-Code provides for the classification of the hazardous nature of the process area in which the measurement device will be installed. If the measurement device is not inherently compatible with this classification, suitable enclosures must be purchased and included in the installation costs. 

Explosion-proof enclosures are characterized by strong metal enclosures with special close-fitting access covers and breathers that contain an ignition to the inside of the enclosure. Field wiring in the hazardous environment is enclosed in a metal conduit of the mineral-insulated-cable type. All conduit and cable connections or cable terminations are threaded and explosion-proof. Conduit seals are put into the conduit or cable system at locations defined by the National Electric Code (Article 501) to prevent gas and vapor leakage and to prevent flames from passing from one part of the conduit system to the other. 

NFPA 70 National Electric Code. National Fire Protection Association, Quincy, MA. 

While some video display screens such as liquid crystal, gas plasma or vacuum fluorescent displays do not present the same charged screen hazards as CRTs, this does not imply that they are safe for use in hazardous locations. This requires special design and certification for use with a given flammable atmosphere. Non-certified equipment used in locations classified as hazardous under Article 500 of NFPA 70 National Electrical Code require a purged or pressurized enclosure to control ignition hazards as described in NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment. The screen in this case is located behind a window in the enclosure. 

National Electrical Code, 257 Naval Boiler and Turbine Laboratory, 337 NEMA, 115, 262, 335 NEMASM-23, 194 Newton s law, 391 Nilson, Hans, 95 Nilson, Rune, 96 Noise... 

All electrical equipment shall be constructed, wired, and tested in accordance with the NFPA 70 National Electrical Code and Specificaton ME-O-JFI 15. 

NFPA. 1999. National Electrical Code Handbook, Articles 500-504. 

In Division 1 areas, the National Electrical Code (NEC) allows only the following wiring methods ... 

Flammable and Combustible Liquids Code Standard for the Installation and Use of Stationary Combustion Engines and Turbines National Electrical Code Recommended Practice on Static Electricity Lightning Protection Code... 

Flame arresters are categorized by the MESG of the gas being handled and its corresponding classification by the National Electrical Code (NEC) groups in the US or the International Electrotechnical Commission (lEC) groups in Europe (see Chapter 5). 

All wiring and electrical equipment in chemical plants should be installed in accordance with the National Electrical Code. Electrical equipment for use in hazardous locations should be recognized by Underwriters Laboratories (or other testing organizations recognized by the authority having jurisdiction) for the conditions to be encountered. 

Mixers and agitators designed for flammable liquids or dusts should be constructed to minimize fire and explosive possibilities. Electrical equipment should follow the requirements of Uie National Electrical Code. Equipment should be bonded and grounded to prevent Uie accumulation of staUc electricity. 

Define plant areas requiring explosion-proof, drip-proof and open motor and associated electrical components. Refer to National Electrical Code and National Electrical Manufacturer s Association Standards. 

It is essential that the process hazardous atmosphere and the process system and handling of combustible hydrocarbons/chemicals be recognized in the physical designs by conforming to the appropriate class of atmos-phere/environment codes specified by the National Electrical Code [71, 83, and 84]. 

Tables 14-8B-1-4 are a selected group of National Electrical Code Articles that recognize certain subjects with which the process engineer should be acquainted. These subjects...

The standard reference for manufacturers as well as the application of electrical equipment in process plants is The National Electrical Code. The Intro-... 

Typical Hazardous Classifications Summary According to the National Electric Code (NEC)... 

Table 14-8A briefly identifies the key hazardous classifications established by the National Electrical Code, Articles 500-505. A more detailed copy of selected portions of the NEC is included in Tables 14-8B and 14-8B-1-4. Depending on the scope of any particular project, the engineer should examine the topics covered in the entire NEC for applicable requirements. 

Reprinted with permission National Electrical Code 1996 Ed., 1995. This and all other reprinted material is not the complete and official position of the NEPA on the referenced subject, which is represented only by the standard in its entirety. National Electrical Code and NEC are registered trademarks of the National Eire Protection Association, Inc., Quincy, MA., 02269. 

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