Hazardous Areas and Classification by NEC

NEC articles 500-516 inform about hazardous area classifications and standards application in united states. Article 505 tells the use of zone system for flammable gasses, vapors and liquids. Zones does not apply to dust, fiber or flyings


Table 1 - Class location definitions

 

Table 2 – Area location comparison, Class I NEC® Zone versus Division locations

 
Hazardous area locations are classified by the type of combustible material present, the extent of time it is present, and the physical construction of the area where such material is present.
 
The presence of flammable gasses or vapors in sufficient quantities to produce an explosive or ignitable mixture constitutes a Class I location. A Class II location is characterized by combustible dust. Class III locations have easily ignitable fibers, but not suspended in the air in quantities sufficient to produce an ignitable airborne mixture.

Division 1 locations, in general, are those areas where ignitable or flammable concentrations of combustible materials exist continuously or repeatedly during normal operations. Division 2 locations, in general, are those areas where such materials exist in ignitable or flammable concentrations only during periods of abnormal operating conditions.

Zone 0 locations, in general, are those areas where ignitable or flammable concentrations of combustible materials exist continuously or for long periods of time. Zone 1 locations, in general, are those areas where ignitable or flammable concentrations of combustible materials are likely to or frequently exist during normal operations. Zone 2 locations, in general, are those areas where ignitable or flammable concentrations of combustible materials are not likely to occur during normal operations or will exist for only a brief period of time.

For all of these locations there are also various groups of gasses, vapors, dusts or fibers. The groups have been established based on the ignition energy required for each of the constituents within that group. Table 3 identifies typical materials within each group and the group identification

All flammable materials have an ignition temperature. Even if the material is not exposed to an open flame or spark, they will ignite if they are exposed to an object whose temperature exceeds the ignition temperature for that material. All apparatus designed for installation in hazardous areas are rated for their maximum surface temperature. Consequently, all apparatus have a temperature code associated with their hazardous area classification. Table 4 shows the temperature code/class for apparatus.



selected equipment shall have site casing operational temperature below the above temperature.

IEC Index

IEC 60027-1 1992
Letter symbols to be used in electrical technology - Part 1: General

IEC 60034-1 2004
Rotating electrical machines - Part 1: Rating and performance

IEC 60617-DB-12M 2001
Graphical symbols for diagrams - 12-month subscription to online database comprising parts 2 to 11 of IEC 60617

IEC 61082-1 1991
Preparation of documents used in electrotechnology - Part 1: General requirements

IEC 61082-2 1993
Preparation of documents used in electrotechnology - Part 2: Functionoriented diagrams

IEC 61082-3 1993
Preparation of documents used in electrotechnology - Part 3: Connection diagrams, tables and lists

IEC 61082-4 1996
Preparation of documents used in electrotechnology - Part 4: Location and installation documents

IEC 60038 2002
IEC standard voltages

IEC 60664-1 2002
Insulation coordination for equipment within low-voltage systems - Part 1: Principles, requirements and tests

IEC 60909-0 2001
Short-circuit currents in three-phase a.c.systems - Part 0: Calculation of currents

IEC 60865-1 1993
Short-circuit currents - Calculation of effects - Part 1: Definitions and calculation methods

IEC 60781 1989
Application guide for calculation of shortcircuit currents in low-voltage radial systems

IEC 60076-1 2000
Power transformers - Part 1: General

IEC 60076-2 1993
Power transformers - Part 2: Temperature rise

IEC 60076-3 2000
Power transformers - Part 3: Insulation levels, dielectric tests and external clearances in air

IEC 60076-5 2006
Power transformers - Part 5: Ability to withstand short circuit IEC/TR 60616 1978 Terminal and tapping markings for power transformers

IEC 60076-11 2004
Power transformers - Part 11: Dry-type transformers

IEC 60445 1999
Basic and safety principles for manmachine interface, marking and identification - Identification of equipment terminals and of terminations of certain designated conductors, including general rules for an alphanumeric system

IEC 60073 2002
Basic and safety principles for manmachine interface, marking and identification – Coding for indicators and actuators

IEC 60446 1999
Basic and safety principles for manmachine interface, marking and identification - Identification of conductors by colours or numerals

IEC 60447 2004
Basic and safety principles for manmachine interface, marking and identification - Actuating principles

IEC 60947-1 2004
Low-voltage switchgear and controlgear - Part 1: General rules

IEC 60947-2 2003
Low-voltage switchgear and controlgear -Part 2: Circuit-breakers

IEC 60947-3 2005
Low-voltage switchgear and controlgear -Part 3: Switches, disconnectors, switchdisconnectors and fuse-combination units

IEC 60947-4-1 2002
Low-voltage switchgear and controlgear -Part 4-1: Contactors and motor-starters –Electromechanical contactors and motorstarters

IEC 60947-4-2 2002
Low-voltage switchgear and controlgear -Part 4-2: Contactors and motor-starters –AC semiconductor motor controllers and starters

IEC 60947-4-3 1999
Low-voltage switchgear and controlgear -Part 4-3: Contactors and motor-starters –AC semiconductor controllers and contactors for non-motor loads

IEC 60947-5-1 2003
Low-voltage switchgear and controlgear -Part 5-1: Control circuit devices and switching elements – Electromechanical control circuit devices

IEC 60947-5-2 2004

Low-voltage switchgear and controlgear -Part 5-2: Control circuit devices and switching elements – Proximity switches

IEC 60947-5-3 2005
Low-voltage switchgear and controlgear -Part 5-3: Control circuit devices and switching elements – requirements for proximity devices with defined behavior under fault conditions

IEC 60947-5-4 2002
Low-voltage switchgear and controlgear - Part 5: Control circuit devices and switching elements – section 4: Method of assessing the performance of low energy contacts. Special tests

IEC 60947-5-5 2005
Low-voltage switchgear and controlgear - Part 5-5: Control circuit devices and switching elements – electrical emergency stop device with mechanical latching function

IEC 60947-5-6 1999
Low-voltage switchgear and controlgear -Part 5-6: Control circuit devices and switching elements – DC interface for proximity sensors and switching amplifiers (NAMUR)

IEC 60947-6-1 2005
Low-voltage switchgear and controlgear - Part 6-1: Multiple function equipment – Automatic transfer switching equipment

IEC 60947-6-2 2002
Low-voltage switchgear and controlgear -Part 6-2: Multiple function equipment -Control and protective switching devices (or equipment) (CPS)

IEC 60947-7-1 2002
Low-voltage switchgear and controlgear -Part 7: Ancillary equipment - Section 1: Terminal blocks for copper conductors

IEC 60947-7-2 2002
Low-voltage switchgear and controlgear -Part 7: Ancillary equipment - Section 2: Protective conductor terminal blocks for copper conductors

IEC 60439-1 2004
Low-voltage switchgear and controlgear assemblies - Part 1: Type-tested and partially type-tested assemblies IEC 60439-2 2005 Low-voltage switchgear and controlgear assemblies - Part 2: Particular requirements for busbar trunking systems (busways)

IEC 60439-3 2001
Low-voltage switchgear and controlgear assemblies - Part 3: Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access for their use -Distribution boards

IEC 60439-4 2004
Low-voltage switchgear and controlgear assemblies - Part 4: Particular requirements for assemblies for construction sites (ACS)

IEC 60439-5 1998
Low-voltage switchgear and controlgear assemblies - Part 5: Particular requirements for assemblies intended to be installed outdoors in public places -Cable distribution cabinets (CDCs) for power distribution in networks

IEC 61095 2000
Electromechanical contactors for household and similar purposes

IEC/TR 60890 1987
A method of temperature-rise assessment by extrapolation for partially type-tested assemblies (PTTA) of low-voltage switchgear and controlgear

IEC/TR 61117 1992
A method for assessing the short-circuit withstand strength of partially type-tested assemblies (PTTA)

IEC 60092-303 1980
Electrical installations in ships. Part 303: Equipment - Transformers for power and lighting

IEC 60092-301 1980
Electrical installations in ships. Part 301: Equipment - Generators and motors

IEC 60092-101 2002
Electrical installations in ships - Part 101: Definitions and general requirements

IEC 60092-401 1980
Electrical installations in ships. Part 401: Installation and test of completed installation

IEC 60092-201 1994
Electrical installations in ships - Part 201: System design – General

IEC 60092-202 1994
Electrical installations in ships - Part 202: System design – Protection

IEC 60092-302 1997
Electrical installations in ships - Part 302: Low-voltage switchgear and controlgear assemblies

IEC 60092-350 2001
Electrical installations in ships - Part 350: Shipboard power cables – General construction and test requirements

IEC 60092-352 2005
Electrical installations in ships - Part 352: Choice and installation of electrical cables IEC 60364-5-52 2001 Electrical installations of buildings – Part 5-52: Selection and erection of electrical equipment – Wiring systems

IEC 60227
Polyvinyl chloride insulated cables of rated voltages up to and including 450/ 750 V
1998 Part 1: General requirements
2003 Part 2: Test methods
1997 Part 3: Non-sheathed cables for fixed wiring
1997 Part 4: Sheathed cables for fixed wiring
2003 Part 5: Flexible cables (cords)
2001 Part 6: Lift cables and cables for flexible connections
2003 Part 7: Flexible cables screened and unscreened with two or more conductors

IEC 60228 2004
Conductors of insulated cables

IEC 60245
Rubber insulated cables - Rated voltages up to and including 450/750 V
2003 Part 1: General requirements
1998 Part 2: Test methods
1994 Part 3: Heat resistant silicone insulated cables
1994 Part 4: Cords and flexible cables
2004 Part 4: Cord and flexible cables
1994 Part 5: Lift cables
1994 Part 6: Arc welding electrode cables
1994 Part 7: Heat resistant ethylene-vinyl acetate rubber insulated cables
2004 Part 8: Cords for applications requiring high flexibility

IEC 60309-2 2005
Plugs, socket-outlets and couplers for industrial purposes - Part 2: Dimensional interchangeability requirements for pin and contact-tube accessories

IEC 61008-1 2002
Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCBs) -Part 1: General rules

IEC 61008-2-1 1990
Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCB’s). Part 2-1: Applicability of the general rules to RCCB’s functionally independent of line voltage

IEC 61008-2-2 1990
Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCB’s). Part 2-2: Applicability of the general rules to RCCB’s functionally dependent on line voltage

IEC 61009-1 2003
Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBOs) -Part 1: General rules

IEC 61009-2-1 1991
Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBO’s) Part 2-1: Applicability of the general rules to RCBO’s functionally independent of line voltage

IEC 61009-2-2 1991
Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBO’s) -Part 2-2: Applicability of the general rules to RCBO’s functionally dependent on line voltage

IEC 60670-1 2002
Boxes and enclosures for electrical accessories for household and similar fixed electrical installations - part 1:General requirements

IEC 60669-2-1 2002
Switches for household and similar fixed electrical installations - Part 2-1: Particular requirements – electronic switches

IEC 60669-2-2 2002
Switches for household and similar fixed electrical installations - Part 2: Particular requirements – section 2: Remote-control switches (RCS)

IEC 60669-2-3 1997
Switches for household and similar fixed electrical installations - Part 2-3: Particular requirements – time-delay switches (TDS)

IEC 60079-10 2002
Electrical apparatus for explosive gas atmospheres - Part 10: Classification of hazardous areas

IEC 60079-14 2002
Electrical apparatus for explosive gas atmospheres - Part 14: Electrical installations in hazardous areas (otherthan mines)

IEC 60079-17 2002
Electrical apparatus for explosive gas atmospheres - Part 17: Inspection and maintenance of electrical installations in hazardous areas (other than mines)

IEC 60269-1 2005
Low-voltage fuses - Part 1: General requirements

IEC 60269-2 1986
Low-voltage fuses. Part 2: Supplementary requirements for fuses for use by authorized persons (fuses mainly for industrial application)

IEC 60269-3-1 2004
Low-voltage fuses - Part 3-1:Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications) -Sections I to IV: Examples of types of standardized fuses

IEC 60127-1/10
Miniature fuses –
2003 Part 1: Definitions for miniature fuses and general requirements for miniature fuse-links
2003 Part 2: Cartridge fuse-links 1988 Part 3: Sub-miniature fuse-links
2005 Part 4: Universal Modular Fuse-Links (UMF)Through-hole and surface mount types
1988 Part 5: Guidelines for quality assessment of miniature fuse-links
1994 Part 6: Fuse-holders for miniature cartridge fuse-links
2001 Part 10: User guide for miniature fuses

IEC 60730-2-7 1990
Automatic electrical controls for household and similar use. Part 2-7:Particular requirements for timers and time switches

IEC 60364-1 2005
Low-voltage electrical installations Part 1: Fundamental principles, assessment of general characteristics,
Definitions

IEC 60364-4-41 2005
Low-voltage electrical installations Part 4-41: Protection for safety -Protection against electric shock

IEC 60364-4-42 2001
Electrical installations of buildings Part 4-42: Protection for safety -Protection against thermal effects

IEC 60364-4-43 2001
Electrical installations of buildings Part 4-43: Protection for safety -Protection against overcurrent

IEC 60364-4-44 2003
Electrical installations of buildings Part 4-44: Protection for safety -Protection against voltage disturbances and electromagnetic disturbances

IEC 60364-5-51 2005
Electrical installations of buildings Part 5-51: Selection and erection of electrical equipment Common rules

IEC 60364-5-52 2001
Electrical installations of buildings Part 5-52: Selection and erection of electrical equipment Wiring systems

IEC 60364-5-53 2002
Electrical installations of buildings Part 5-53: Selection and erection of electrical equipment Isolation, switching and control

IEC 60364-5-54 2002
Electrical installations of buildings Part 5-54: Selection and erection of electrical equipment Earthing arrangements, protective conductors and protective bonding conductors

IEC 60364-5-55 2002
Electrical installations of buildings Part 5-55: Selection and erection of electrical equipment Other equipment

IEC 60364-6-61 2001
Electrical installations of buildings Part 6-61: Verification - Initial verification

IEC 60364-7 1984…2005
Electrical installations of buildings Part 7: Requirements for special installations or locations

IEC 60529 2001
Degrees of protection provided by enclosures (IP Code)

IEC 61032 1997
Protection of persons and equipment by enclosures - Probes for verification

IEC/TR 61000-1-1 1992
Electromagnetic compatibility (EMC) Part 1: General - Section 1: application and interpretation of fundamental definitions and terms

IEC/TR 61000-1-2 2001
Electromagnetic compatibility (EMC) Part 1-2: General - Methodology for the achievement of the functional safety of electrical and electronic equipment with regard to electromagnetic phenomena

IEC/TR 61000-1-3 2002
Electromagnetic compatibility (EMC) Part 1-3: General - The effects of highaltitude EMP (HEMP) on civil equipment and systems