Hazardous Location Basics
HAZARDOUS LOCATION: An Area where the possibility of explosion and fire is created by the presence of flammable gases, vapors, dusts, fibers or flying.
CLASS I (NEC-500-4): Those areas in which flammable gases or vapors may be present in the air in sufficient quantities to be explosive or ignitable.
CLASS II (NEC-500-4): Those areas made hazardous by the presence of combustible dust.
CLASS III (NEC-500-6): Those areas in which there are easily ignitable fibers or flying present, due to type of material being handled, stored, or processed.
DIVISION 1 (NEC-500,4,5,6): Division One in the normal situation, the hazard would be expected to be present in everyday production operations or during frequent repair and maintenance activity.
DIVISION 2 (NEC-500,4,5,6): Division Two in the abnormal situation, material is expected to be confined within closed containers or closed systems and will be present only through accidental rupture, breakage, or unusual faulty operation.
GROUPS (NEC-500-2 & 502-1): The gases of vapors of Class I locations are broken into four groups by the code. A, B, C, and D. Theses materials are grouped according to the ignition temperature of the substance, its explosion pressure and other flammable characteristics.
CLASS II: dust locations - groups E, F, and G. These groups are classified according to the ignition temperature and the conductivity of the hazardous substance.
SEALS (NEC-501-5 & 502-5): Special fittings that are required either to prevent the passage of hot gasses in the case of an explosion in a Class I area of the passage of combustible dust, fibers, or flyings in a Class II or III area.
ARTICLES 500 Through 503 (1978 NEC): Explain in detail the requirements for the installation of wiring of electrical equipment in hazardous locations. These articles along with other applicable regulations, local governing inspection authorities, insurance representatives, and qualified engineering/technical assistance should be your guides to the installation of wiring or electrical equipment in any hazardous or potentially hazardous location.
Typical Class I Locations:
- Petroleum refineries, and gasoline storage and dispensing areas.
- Industrial firms that use flammable liquids in dip tanks for parts cleaning or other operations.
- Petrochemical companies that manufacture chemicals from gas and oil.
- Dry cleaning plants where vapors from cleaning fluids can be present.
- Companies that have spraying areas where they coat products with paint or plastics.
- Aircraft hangars and fuel servicing areas.
- Utility gas plants, and operations involving storage and handling of liquefied petroleum gas or natural gas.
Typical Class II Locations:
- Grain elevators, flour and feed mills.
- Plants that manufacture, use, or store magnesium or aluminum powders.
- Plants that have chemical or metallurgical processes or plastics, medicines and fireworks, etc.
- Producers or starch or candies.
- Spice-grinding plants, sugar plants and cocoa plants.
- Coal preparation plants and other carbon-handling or processing areas.
Typical Class III Locations:
- Textile mills, cotton gins, cotton seed mills, and flax processing plants.
- Any plant that shapes, pulverizes, or cuts wood and creates sawdust or flyings.
NOTE: fibers and flyings are not likely to be suspended in the air, but can collect around machinery or on lighting fixtures and where heat, a spark, or hot metal can ignite them.:
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- Lamp Guide: Fluorescent
- Lamp Guide: HID
- Lamp Guide: Incandescent
- Line Noise
- Power Surges and Spikes
- Heat Dissipation in Electrical Enclosures
- Hazardous Location Basics
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- Occupancy Sensor Design Guide
- Occupancy Sensor Application Guide
- Color Application for HID Lamps
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- General Electric Heater Coil
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- Conduit Fill Table
- NEMA Straight Blade Configs
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- Common Conversion Factors
- Derate 3 Conductors in a Raceway
- Direct Current Motor Full Load Current
- Approximate Full Load Amperes
- Full Load Current: Three Phase AC Motors
- Full-Load Current: Single Phase AC Motors
- Specific Resistance
- Temperature Conversion Table
- UL Fuse Classification Chart
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- Ohm's Law
- Electrical Formulas
- Full Load Formula
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- Backbone Runs: UTP Cable
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- Cable Administration
- Category Cables
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- Common Ethernet Systems
- Common Types of Cabling
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- 10Base-T Crossover Patch Cord
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- General Cable Installation Rules
- UTP Cable Attenuation
- Installing Category Data Cables
- Parameters of EIA/TIA 568
- Separation from Sources of Interference
- Structured Cabling (568) Systems
- Standard Networking Configurations
- Telecommunication Outlet Specifications
- UTP Connecting Hardware