Available for NEC and CEC codes, each book provides a compilation of key changes to the current regional code and covers the classification of hazardous atmospheres, explosion prevention techniques, equipment, wiring methods and more.
|Industrial Fittings Bend Radius and Cubic Capacity Chart||View|
|Industrial Fittings Wire Fill Chart||View|
|TSC Sealing Compound||
|Corrosion Inhibitor Device (CID)||-----||View||
Chico A Sealing Compound (Chico A/Chico A3/Chico A4/Chico A05/Chico A200)
CHICO X Fiber (Chico X Fiber/Chico X4/Chico X6/Chico X7)
|STL-2 Thread Lubricant||View||-----||-----||-----|
|STL-8 Thread Lubricant||View||-----||-----||-----|
|HTL4 High Temperature Thread Lubricant||View||-----||-----||-----|
|Water absorbing Pack/Dessicant||-----||View||-----||View|
|Isocyanate - Chico Speedseal (SS2 & SS6) Part 1 of 2||
|Polyol - Chico Speedseal (SS2 & SS6) Part 2 of 2||View||-----||-----||-----|
|Battery for emergency ballast in DMVFB, EVLPFB, Fluorescent||-----||View||-----||-----|
|Battery for N2LPS||-----||View||-----||-----|
Battery for ELPS
Chico Liquid Sealing Compound (10, 20, 200) Part 1
Chico Liquid Sealing Compound (10, 20, 200) Part 2
|Chico Liquid Sealing Compound (75, 400) Part 1||View||-----||-----||-----|
Chico Liquid Sealing Compound (75, 400) Part 2
Additional Information on NEC, CEC and IEC Hazardous Areas
|Example||NEC 500-503||NEC 505|
|CLASS I (Gases and Vapors)||
IIC or IIB+H2
|CLASS II (Dusts)||
|CLASS III (Fibers & Flyings)||
|Typical Gas Hazard||North America NEC Article 500 (Class I)||CENELEC EN 50 014 IEC|
|HYDROGEN||B||IIC or IIB +H2|
|Gas classification and ignition temperatures relate to mixtures of gas and air at ambient temperature and atmospheric pressure.|
|Division 1||Division 1||Division 2|
(Zone 20 dust)
(Zone 21 dust)
(Zone 22 dust)
|Max. surface temp.(°C)||NEC Table500-3(d)||
|EN 50 014|
|A full list of gases and temperature classifications is published in the Crouse-Hinds Code Digest.|
|OIL IMMERSION||1 or 2||1 or 2||6||015||o|
|PRESSURIZATION||1 or 2||1 or 2||2||016||p|
|2||1 or 2||5||017||q|
|FLAMEPROOF||-||1 or 2||1||018||d|
|2||1 or 2||7||019||e|
|1 or 2||0*,1 or 2||11||
|ia or ib|
|1 or 2||1 or 2||-||-||-|
|ENCAPSULATION||-||1 or 2||18||028||m|
|SPECIAL||-||1 or 2||None**||None||s|
*ia: Zone 0,1,2; ib: Zone 1,2, not Zone 0
** mentioned in IEC 79-0
^ includes non-sparking, restricted breathing, hermetically-sealed, non-incendive, etc.
Protection against solid bodies
Protection against liquid
|0 - NO PROTECTION||0 - NO PROTECTION|
|1- OBJECTS EQUAL TO OR GREATER THAN 50 mm||1 - VERTICALLY DRIPPING WATER|
|2 - OBJECTS EQUAL TO OR GREATER THAN 12.5 mm||2 - 75 TO 105°-ANGLED DRIPPING WATER|
|3 - OBJECTS EQUAL TO OR GREATER THAN 2.5 mm||3 - SPRAYING WATER|
|4 - OBJECTS EQUAL TO OR GREATER THAN 1.0 mm||4 - SPLASHING WATER|
|5 - DUST-PROTECTED||5 - WATER JETS|
|6 - DUST-TIGHT||6 - HEAVY SEAS, POWERFUL WATER JETS|
|7 - EFFECTS OF IMMERSION|
|8 - INDEFINITE IMMERSION|
Type 3 Enclosure
Type 3 enclosures are intended for outdoor use primarily to provide a degree of protection against windblown dust, rain, sleet and external ice formation.
Type 3R Enclosure
Type 3R enclosures are intended for outdoor use primarily to provide a degree of protection against falling rain and external ice formation.
Type 3S Enclosure
Enclosures are intended for outdoor use primarily to provide a degree of protection against rain, sleet, windblown dust, and to provide
for operation of external mechanisms when ice laden.
Type 4 Enclosure
Type 4 enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, hose-directed water and external ice formation.
Type 4X Enclosure
Type 4X enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose-directed water and external ice formation.
Type 7 Enclosure
Type 7 enclosures are for use indoors in locations classified as Class I, Groups A, B, C or D, as defined in the National Electrical Code®.
Type 9 Enclosure
Type 9 enclosures are for use in indoor locations classified as Class II, Groups E, F or G, as defined in the National Electrical Code®.
Type 12 Enclosure
Type 12 enclosures are intended for indoor use primarily to provide degree of protection against dust, falling dirt and dripping noncorrosive liquids.
Adequately Ventilated Area:
An adequately ventilated area is an area that has a ventilation system (natural or artificial) that, as a minimum, prevents the accumulation of gases or vapors to an explosive level. Most standards and recommended practices recommend preventing levels in excess of 25 percent of the Lower Flammable (Explosive) Limit (LFL/LEL). NOTE - Adequate ventilation of an area alone is not an effective means for the prevention of dust explosions.
Acceptable to the authority having jurisdiction. NOTES: 1) See Authority Having Jurisdiction; 2) In determining the acceptability of installations or procedures, equipment, or material, the authority having jurisdiction may base acceptance on compliance with appropriate standards. In the absence of such standards, said authority may require evidence of proper installation, procedure, or use. The authority having jurisdiction may also refer to the listing or labeling practices of product-testing organizations. These organizations are in a position to determine compliance with appropriate standards for the current production of listed or labeled items.
An electrical make/break component, that is generally interpreted as capable of producing an arc with energy sufficient to cause ignition of a specific ignitable mixture.
Apparatus in which the circuits are not intrinsically safe themselves but affect the energy in the intrinsically safe circuits and are relied upon to maintain intrinsic safety. Associated electrical apparatus may be either: a) electrical apparatus that has an alternative type of protection for use in the appropriate hazardous (classified) location, or b) electrical apparatus that is not protected and, therefore, cannot be used within a hazardous (classified) location. NOTE - See also Intrinsic Safety.
Authority Having Jurisdiction:
The organization, office, or individual that has the responsibility and authority for approving equipment, installations, or procedures. NOTE - The term Authority Having Jurisdiction is used in a broad manner since 'jurisdiction' and 'approval' agencies vary, as do their responsibilities. Where public safety is primary, the authority having jurisdiction may be a federal, state/provincial, local, other regional department, or an individual such as an inspector from a labor or health department, electrical inspector, or others having statutory authority. An insurance inspection agency, rating bureau, or other insurance company representative may be the 'authority having jurisdiction.' An owner or his designated agent may also assume the role. At government-owned installations, the commanding officer, departmental official, or designated agent may be the 'authority having jurisdiction.'
The permanent joining of metallic parts to form an electrically conductive path that will ensure electrical continuity and the capacity to conduct safely any current likely to be imposed.
Generic term referring to equipment that has been evaluated by a recognized testing agency and confirmed to be in compliance with the applicable standard(s). NOTE - Some agencies use the terms 'approved', 'listed', or 'labeled equipment' to indicate compliance with the acceptable standard.
Class I Location:
A location in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.
Class I, Division 1 Location:
A location (1) in which ignitable concentrations of flammable gases or vapors can exist under normal operating conditions; (2) in which ignitable concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (3) in which breakdown or faulty operation of equipment or processes might release ignitable concentrations of flammable gases or vapors and might also cause simultaneous failure of electrical equipment that could act as a source of ignition.
Class I, Division 2 Location:
A location (1) in which volatile flammable liquids or flammable gases are handled, processed, or used, but in which the liquids, vapors, or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or systems, or in case of abnormal operation of equipment; or (2) in which ignitable concentrations of gases or vapors are normally prevented by positive mechanical ventilation and might become hazardous through failure or abnormal operation of the ventilating equipment; or (3) that is adjacent to a Class I, Division 1 location and to which ignitable concentrations of gases or vapors might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided.
Class II Location:
A location that is hazardous because of the presence of combustible dust.
Class II, Division 1 Location:
A location (1) in which combustible dust is in the air under normal operating conditions in quantities sufficient to produce explosive or ignitable mixtures; or (2) in which mechanical failure or abnormal operation of machinery or equipment might cause such explosive or ignitable mixtures to be produced and might also provide a source of ignition through simultaneous failure of electrical equipment, operation of protection devices, or from other causes; or (3) in which combustible dusts of an electrically conductive nature may be present in hazardous quantities.
Class II, Division 2 Location:
A location in which combustible dust is not normally in the air in quantities sufficient to produce explosive or ignitable mixtures and dust accumulations are normally insufficient to interfere with the normal operation of electrical equipment or other apparatus, but combustible dust may be in suspension in the air as a result of infrequent malfunctioning of handling or processing equipment and where combustible dust accumulations on, in, or in the vicinity of the electrical equipment may be sufficient to interfere with the safe dissipation of heat from electrical equipment or may be ignitable by abnormal operation or failure of electrical equipment.
Class III Location:
A location that is hazardous because of the presence of easily ignitable fibers or flyings but in which such fibers or flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures.
Class III, Division 1 Location:
A location in which easily ignitable fibers or materials producing combustible flyings are handled, manufactured, or used.
Class III, Division 2 Location:
A location in which easily ignitable fibers are stored or handled (except in the process of manufacture).
A drawing or other document provided by the manufacturer of the intrinsically safe or associated apparatus that details the allowed interconnections between the intrinsically safe and associated apparatus.
Degree of Protection (IP):
A system of rating standard levels of protection provided by apparatus for the protection of persons against contact with live or moving parts inside the apparatus, as well as the protection provided by apparatus against ingress of solids and/or liquids. This type of protection classification is in addition to (and not an alternative to) the types of protection necessary to ensure protection against ignition in hazardous (classified) locations. Definitions are found in IEC Publication 529. NOTE - See also Enclosure Type.
Any finely divided solid material 420 microns or less in diameter (i.e. material passing a U.S. No. 40 sieve) that presents a fire or explosion hazard.
A term used to describe an enclosure that will exclude ignitable amounts of dust that might affect performance or rating and that, when installed in accordance with the original design intent, will not permit arcs, sparks, or heat otherwise generated or liberated inside the enclosure to cause ignition of exterior accumulations or atmosphere suspensions of a specified dust in the vicinity of the enclosure.
Dust Layer, Combustible:
Any surface accumulation of combustible dust that is thick enough to propagate flame or will degrade and ignite.
A term describing an enclosure in which the ingress of dust is not totally prevented, but does not enter in sufficient quantity to interfere with the safe operation of the equipment or accumulate in a position within the enclosure where it is possible to cause an ignition hazard.
An enclosure so constructed that dust will not enter the enclosing case under specified test conditions.
Designation of explosion protected apparatus complying with European Standards.
Designation of explosion protected apparatus.
An international system of certification for explosion protected apparatus administered by the IEC and described by IECEE-04. The eventual goal of this scheme is that a manufacturer of hazardous location electrical equipment would be able to obtain a single 'Ex' Certificate of Conformity from one Certification Laboratory and sell that product in any participating country without legal or technical obstacle and without the need to get it recertified locally.
A type of protection in which the parts that could ignite an explosive atmosphere by either sparking or heating are enclosed in an encapsulant in such a way that this explosive atmosphere cannot be ignited. This type of protection is referred to as 'm'.
A North American system of rating standard levels of protection provided to electrical apparatus by enclosures for (1) the protection of persons against contact with live or moving parts inside the enclosure; (2) the protection provided by enclosure against ingress of solids and/or liquids; (3) the protection provided by the enclosure against the deleterious effects of corrosion; and (4) the protection provided by the enclosure against damage due to the formation of external ice. This enclosure type is in addition to (and not an alternative to) the types of protection necessary to ensure protection against ignition in hazardous (classified) locations. Definitions are found in ANSI/UL 50 or ANSI/NEMA 250. NOTE - See also Degree of Protection.
A concept that allows interconnection of intrinsically safe apparatus to associated apparatus not specifically examined in such a combination. The criteria for interconnection is that the voltage (Vmax) and current (Imax) which intrinsically safe apparatus can receive and remain intrinsically safe, considering faults, must be equal to or greater than the voltage (Voc or Vt) and current (Isc or It) levels which can be delivered by the associated apparatus, considering faults and applicable factors. In addition, the maximum unprotected capacitance (Ci) and inductance (Li) of the intrinsically safe apparatus, including interconnecting wiring, must be equal to or less than the capacitance (Ca) and inductance (La) that can safely be connected to the associated apparatus. If these criteria are met, then the
A method of connection of an electrical apparatus to the external circuits by means of the connecting facilities inside the main enclosure or in a terminal compartment having a free opening to the main enclosure.
A method of connection of an electrical apparatus to the electrical circuits by means of a terminal box or a plug and socket connection which is external to the main enclosure. (IEV 426-04-08).
Apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby. NOTE - See also Flameproof Enclosure.
A mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapor, mist, dust, or fibers in which, after ignition, combustion spreads throughout the unconsumed mixture. NOTE - See also Hazardous (Classified) Location.
Fault (As Applicable to Intrinsically Safe Systems):
A defect or electrical breakdown of any component, spacing, or insulation that alone or in combination with other defects or breakdowns may adversely affect the electrical or thermal characteristics of the intrinsically safe system. If a defect or breakdown leads to defects or breakdowns in other components, the primary and subsequent defects and breakdowns are considered to be single fault. Certain components may be considered not subject to fault when analyses or tests for intrinsic safety are made. NOTE - See also Protective Component.
Fibers and Flyings:
These are materials not normally in suspension in air; and are of larger particle size than dusts. Fibers and flyings include materials such as cotton linters, sawdust, textile fibers, and other particles that are usually more a fire hazard than an explosion hazard.
A type of protection of electrical apparatus in which the enclosure will withstand an internal explosion of a flammable mixture which has penetrated into the interior, without suffering damage and without causing ignition, through any joints or structural openings in the enclosure, of an external explosive atmosphere consisting of one or more of the gases or vapors for which it is designed. This type of protection is referred to as 'd'. NOTE - See also Explosionproof Apparatus.
Flammable (Explosive) Limits:
The flammable (explosive) limits of a gas or vapor are the lower (LFL/LEL) and upper (UFL/UEL) flammable (explosive) limit percentages by volume of concentration of gas in a gas-air mixture that will form an ignitable mixture.
Any liquid having a flash point below 37.8°C (100°F) and having a vapor pressure not exceeding 275 kPa (40 psia) at 37.8°C (100°F).
Flammable Gas or Vapor:
A gas or vapor which, when mixed with air in certain proportions, will form an explosive gas atmosphere.
The minimum temperature at which a liquid gives off vapor in sufficient concentration to form an ignitable mixture with air near the surface of the liquid, as specified by test.
A classification of electrical apparatus related to the explosive atmosphere for which it is to be used.
Hazardous (Classification) Location: A location in which fire or explosion hazards may exist due to an explosive atmosphere of flammable gases or vapors, flammable liquids, combustible dust, or easily ignitable fibers or flyings. NOTE - See also Explosive Atmosphere.
Hermetically Sealed Device:
A device that is sealed against the entrance of an external atmosphere and in which the seal is made by fusion, e.g. soldering, brazing, welding, or the fusion of glass to metal.
High Temperature Apparatus:
As specified by ANSI/NFPA 70, Article 501-5(a)(1), the term HIGH TEMPERATURE APPARATUS is to be interpreted as apparatus in which the maximum operating temperature (including ambient temperature effect) exceeds 80 percent of the autoignition temperature in degrees Celsius (°C) of the gas or vapor involved.
Ignition (Autoignition) Temperature (AIT):
The minimum temperature required to initiate or cause self-sustained combustion of a solid, liquid, or gas independently of the heating or heating elements. NOTES: 1) For additional information refer to ANSI/NFPA 325M. 2) A distinction is made between ignition temperature and flash point. See Flash Point.
Equipment or wiring that under normal conditions, or under specified abnormal conditions, can release sufficient electrical or thermal energy to cause ignition of a specific explosive atmosphere.
Type of protection applied to electrical apparatus that does not produce arcs or sparks in normal service and under specified abnormal conditions, in which additional measures are applied so as to give increased security against the possibility of excessive temperatures and of the occurrence of arcs and sparks. This type of protection is referred to as 'e'.
A type of protection in which a portion of the electrical system contains only intrinsically safe equipment (apparatus, circuits and wiring) that is incapable of causing ignition in the surrounding atmosphere. No single device or wiring is intrinsically safe by itself (except for battery-operated self-contained apparatus such as portable pagers, transceivers, gas detectors, etc., which are specifically designed as intrinsically safe self-contained devices) but is intrinsically safe only when employed in properly designed intrinsically safe system. This type of protection is referred to as 'i'. NOTE - See also Associated Apparatus.
Intrinsically Safety Barrier:
A component containing a network designed to limit the energy (voltage and current) available to the protected circuit in the hazardous (classified) location under specified fault conditions.
Intrinsically Safe Circuit:
A circuit in which any spark or thermal effect, produced either normally or in specified fault conditions, is incapable, in the specified test conditions, of causing ignition of a given explosive atmosphere.
Intrinsically Safe Electrical Apparatus:
Electrical apparatus in which all the circuits are intrinsically-safe circuits.
Intrinsically Safety Ground Bus:
A grounding system that has a dedicated conductor separate from the power system so that the ground currents will not normally flow and that is reliably connected to a ground electrode. NOTE - For further information, refer to Article 504 of ANSI/NFPA 70, or Section 10 of CSA C22.1 or ANSI/ISA rp 12.6.
Intrinsically Safe System:
An assembly of interconnected intrinsically safe apparatus, associated apparatus, other apparatus, and interconnecting cables in which those parts of the system that may be used in hazardous (classified) locations are intrinsically safe circuits.
A liquid having a flash point at or above 37.8°C (100°F). Combustible liquids are subdivided as follows: a) Class II liquids include those having flash points at or above 37.8°C (100°F) and below 60°C (140°F); b) Class IIIA liquids include those having flash points at or above 60°C (140°F) and below 93°C (200°F); c) Class IIIB liquids include those having flash points at or above 93°C (200°F). NOTE -For additional information, refer to e.g. NFPA 321, Basic Classification of Flammable and Combustible Liquids. It should also be noted that these 'Classes' have no relation to the hazardous location 'Classes'.
Equipment or materials included in a list published by an organization acceptable to the AUTHORITY HAVING JURISDICTION and concerned with product evaluation, that maintains periodic inspection of production of listed equipment or materials, and whose listing states either that the equipment or material meets appropriate designated standards or has been tested and found suitable for use in a specified manner. NOTE - The means for identifying listed equipment may vary for each organization concerned with product evaluation, some of which do not recognize equipment as listed unless it is also labeled. The AUTHORITY HAVING JURISDICTION should utilize the system employed by the listing organization to identify a listed product.
Lower Explosive Limit (LEL):
Refer to Flammable (Explosive) Limits.
Lower Flammable Limit (LFL):
Refer to Flammable (Explosive) Limits.
Components having contacts that can interrupt a circuit (even if the interruption is transient in nature). Examples of make/break components are relays, circuit breakers, servo potentiometers, adjustable resistors, switches, connectors and motor brushes.
Maximum Surface Temperature:
The highest temperature attained by a surface accessible to flammable gases, vapors or combustible dusts under conditions of operation within the ratings of the apparatus (including specified abnormal conditions).
Minimum Cloud Ignition Temperature:
The minimum temperature at which a combustible dust atmosphere will autoignite and propagate an explosion.
Minimum Dust Layer Ignition Temperature:
The minimum temperature of a surface that will ignite a dust on it after a long time (theoretically, until infinity). In most dusts, free moisture has been vaporized before ignition.
Minimum Explosive (Dust) Concentration:
The minimum concentration of a dust cloud that, when ignited, will propagate a flame away from the source of ignition.
Minimum Ignition Energy (MIE):
The smallest amount of energy that can ignite the most easily ignitable mixture of a specific gas or vapor-in-air mixture or dust-in-air mixture.
Maximum Experimental Safe Gap (MESG):
The maximum clearance between two parallel metal surfaces which has been found, under specified test conditions, to prevent an explosion in a test chamber from being propagated to a secondary chamber containing the same gas or vapor at the same concentration.
Minimum Igniting Current Ratio (MIC Ratio):
The ratio derived by dividing the minimum current required from an inductive spark discharge to ignite the most easily ignitable mixture of a gas or vapor by the minimum current required from an inductive spark discharge to ignite methane under the same test conditions.
Nonhazardous (Unclassified) Location:
A location in which fire or explosion hazards are not expected to exist specifically due to the presence of flammable gases or vapors, flammable liquids, combustible dusts, or ignitable fibers or flyings. Such a location may also be referred to as a Safe Area.
A circuit, other than field wiring, in which any arc or thermal effect produced, under intended operating conditions of the equipment, is not capable, under specified test conditions, of igniting the flammable gas-, vapor-, or dust-in-air mixture. NOTE - See also Nonincendive Field Wiring.
A component having contacts for making or breaking an ignition-capable circuit and in which the contacting mechanism is constructed so that the component is incapable of igniting the specified explosive atmosphere. The housing of a nonincendive component is not intended to (1) exclude the flammable atmosphere; or (2) contain an explosion. This type of protection is referred to as 'nA'.
Equipment having electrical/electronic circuitry and components that are incapable, under normal conditions, of causing ignition of the flammable gas-, vapor-, or dust-in-air mixture due to arcing or thermal effect. This type of protection is referred to as 'NA', 'NC', or 'NR'.
Nonincendive Field Wiring:
Wiring that enters or leaves an equipment enclosure and, under normal operating conditions of the equipment, is not capable, due to arcing or thermal effects, of igniting the flammable gas-, vapor-, or dust-in-air mixture. Normal operation includes opening, shorting, or grounding the field wiring. NOTE - See also Nonincendive Circuit.
Equipment is generally considered to be under normal conditions when it conforms electrically and mechanically with its design specifications and is used within the limits specified by the manufacturer.
Type of protection in which the electrical apparatus or parts of the electrical apparatus are immersed in a protective liquid in such a way that an explosive atmosphere which may be above the liquid or outside the enclosure cannot be ignited. This type of protection is referred to as 'o'.
A type of protection in which the parts capable of igniting an explosive atmosphere are fixed in position and completely surrounded by filling material to prevent the ignition of an external explosive atmosphere. This type of protection is referred to as 'q'. NOTE - This type of protection may not prevent the surrounding explosive atmosphere from penetrating into the apparatus and Ex components and being ignited by the circuits. However, due to the small free volumes in the filling material and due to the quenching of a flame which may propagate through the paths in the fillings material, an external explosion is prevented.
The technique of guarding against the ingress of the external atmosphere into an enclosure by maintaining a Protective Gas therein at a pressure above that of the external atmosphere. This type of protection is referred to as 'p'.
Pressurization, Type X:
A method of reducing the classification within an enclosure from Division 1/Zone 1 to nonhazardous (unclassified).
Pressurization, Type Y:
A method of reducing the classification within an enclosure from Division 1/Zone 1 to Division 2/Zone 2.
Pressurization, Type Z:
A method of reducing the classification within an enclosure from Division 2/Zone 2 to nonhazardous (unclassified).
Protection, Type of:
The specific measures applied to electrical apparatus to avoid ignition of a surrounding explosive atmosphere. Examples are 'e' and 'n'.
Protective Component (As Applied to Intrinsic Safety):
A component that is so unlikely to become defective in a manner that will lower the intrinsic safety of the circuit that it may be considered not subject to fault when analyses or tests for intrinsic safety are made.
The gas used for pressurization or for the dilution of flammable gases to a level well below their lower explosive limit, usually below 25 percent LFL/LEL. The Protective Gas may be air, nitrogen, other nonflammable gas, or a mixture of such gases.
In a pressurized enclosure, the operation of passing a quantity of Protective Gas through the enclosure and ducts, so that the concentration of the explosive gas atmosphere is brought to a safe level.
A protection technique in which the tightness of an enclosure is assured so that short-term presence of a flammable gas or vapor cloud around the enclosure will not cause the concentration inside the enclosure to reach the LFL/LEL because of breathing or diffusion. This type of protection is referred to as 'nR'.
Refer to Nonhazardous (Unclassified) Location.
Seal, Cable, Explosionproof:
A cable termination fitting filled with compound and designed to contain an explosion in the enclosure to which it is attached or to minimize passage of flammable gases or vapors from one location to another. A conduit seal may also be used as a cable seal.
Seal, Conduit, Explosionproof:
A sealing fitting, filled with a poured potting compound, designed to contain an explosion in the enclosure to which it is attached and to minimize passage of flammable gases or vapors from one location to another.
A construction where components capable of initiating an internal explosion due to arcing, sparking, or thermal effects under normal conditions are isolated from the wiring system by means of factory-installed flameproof seal or joint for the purpose of eliminating the need for an external, field-installed conduit seal and, in some cases, a field-installed cable seal.
A device so constructed that it cannot be opened during normal operational conditions or operational maintenance; it has a free internal volume less than 100 cubic centimeters (6.1 cubic inches) and is sealed to restrict entry of an external atmosphere. This type of protection is referred to as 'nC'.
Simple Apparatus (As Applied to Intrinsic Safety):
A device that will not generate or store more than 1.2 V, 0.1 A, 25 mW, or 20J. Examples are: switches, thermocouples, light-emitting diodes, and resistance temperature detectors (RTDs).
Source of Release:
A point from which flammable gases or vapors, flammable liquid, combustible dusts, or ignitable fibers or flyings may be released into the atmosphere.
The temperature of air or other media where electrical apparatus is to be used.
Temperature Identification Number (T Code/Temperature Class):
A system of classification by which one of 14 temperature identification numbers (for Zones, six temperature classes) is allocated to apparatus. The temperature identification number represents the maximum surface temperature of any part of the apparatus that may come in contact with the flammable gas or vapor mixture.
Type of Protection:
Refer to Protection, Type of.
Upper Explosive Limit (UEL):
Refer to Flammable (Explosive) Limits.
A method of specifying the probability that a location is made hazardous by the presence, or potential presence, of flammable concentrations of gases and vapors, or combustible mixtures of dusts.
Zone 0 (IEC):
An area in which an explosive gas atmosphere is present continuously or for long periods.
Zone 0 (NEC):
A Class I, Zone 0 location is a location (1) in which ignitable concentrations of flammable gases or vapors are present continuously; or (2) in which ignitable concentrations of flammable gases or vapors are present for long periods of time. (NEC Section 505-9(a)
Zone 1 (IEC):
An area in which an explosive gas atmosphere is likely to occur in normal operation.
Zone 1 (NEC):
A Class I, Zone 1 location is a location (1) in which ignitable concentrations of flammable gases or vapors are likely to exist under normal operating conditions; or (2) in which ignitable concentrations of flammable gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (3) in which equipment is operated or processes are carried on, of such a nature that equipment breakdown or faulty operations could result in the release of ignitable concentrations of flammable gases or vapors and also cause simultaneous failure of electrical equipment in a mode to cause the electrical equipment to become a source of ignition; or (4) that is adjacent to a Class I, Zone 0 location from which ignitable concentrations of vapors could be communicated, unless communication is prevented by adequate positive-pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided. (NEC Section 505-9(b)).
Zone 2 (IEC):
An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it does occur, is likely to do so only infrequently and will exist for a short period only.
Zone 2 (NEC):
A Class I, Zone 2 location is a location (1) in which ignitable concentrations of flammable gases or vapors are not likely to occur in normal operation and if they do occur will exist only for a short period; or (2) in which volatile flammable liquids, flammable gases, or flammable vapors are handled, processed, or used, but in which the liquids, gases, or vapors normally are confined within closed containers or closed systems from which they can escape only as a result of accidental rupture or breakdown of the containers or system, or as the result of abnormal operation of the equipment with which the liquids or gases are handled, processed, or used; or (3) in which ignitable concentrations of flammable gases or vapors normally are prevented by positive mechanical ventilation, but which may become hazardous as the result of failure or abnormal operation of the ventilation equipment; or (4) that is adjacent to a Class I, Zone 1 location, from which ignitable concentrations of flammable gases or vapors could be communicated, unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided. (NEC Section 505-9(c))
Zone 21 (IEC):
An area not classified as Zone 20 in which combustible dust, as a cloud, is likely to occur during normal operation, in sufficient quantity to be capable of producing an explosive concentration of combustible dust in mixture with air. This zone can include, among others, areas in the immediate vicinity of powder filling or emptying points and areas where dust layers occur and are likely in normal operation to give rise to an explosive concentration of combustible dust in mixture with air.
Zone 22 (IEC):
An area not classified as Zone 21 in which combustible dust, as a cloud, can occur infrequently, and persist only for a short period, or in which accumulations or layers of combustible dust can give rise to an explosive concentration of combustible dust in mixture with air. This zone can include, among others, areas in the vicinity of equipment containing dust, which dust can escape from leaks and form deposits (e.g. milling rooms in which dust can escape from the mills and then settle).