HAZ AREA Standards Terms And Definitions

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Combustible Liquid
Any liquid, other than a flammable liquid, that has a flash point, and has a fire point that is less than its boiling point.

Explosive atmosphere
Mixtures with air, under atmospheric conditions, of substances in the form of gas, vapour, mist or dust, fibres and flyings, in which after ignition, combustion spreads throughout the unconsumed mixture.

Extent of zone (Gas, Vapour)
Distance in any direction from the source of release to the point where the gas/air mixture has been diluted with air to a value below he lower explosive limit.

Extent of zone (dust)
Distance in any direction from the source of release to the point where the hazard associated with the release is considered to exist no longer.

Fire Point
In relation to a liquid, the fire point is the temperature at which the liquid, when tested according to the method set out in ISO 2592, first evolves vapour at a sufficient rate to sustain burning for at least 5 seconds after application of the specified test flame.

Flash Point
The lowest temperature, corrected to a barometric pressure of 101.3 kPa, at which application of a test flame causesthe vapour of the test portion to ignite under the specified conditions of test.

Flammable liquid
Liquids, or mixtures of liquids, or liquids containing solids in solution or suspension (e.g. paints, varnishes, lacquers, etc., but not including substances otherwise classified on account of their dangerous characteristics) which give off a flammable vapour at temperatures of not more than 60.5°C, closed cup test, or not more than 65.6°C, open cup test, normally referred to as the flash point.

Grades of release
There are three basic grades of release, as listed below in order of decreasing frequency and likelihood of the explosive gas atmosphere being present:
  • continuous grade;
  • primary grade;
  • secondary grade.
Hazardous area
An area in which an explosive atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of potential ignition sources.

Zones
Hazardous areas are classified into zones based upon the frequency of the occurrence and the duration of the explosive atmosphere.
 

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Non-hazardous Area
Area in which an explosive atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of electrical apparatus

Certificate
Document that assures the conformity of a product, process, system, person, or organization with specified requirements

The certificate may be either the supplier’s declaration of conformity or the purchaser’s recognition of conformity or certification (as a result of action by a third party) as defined in ISO/IEC 17000.

Equipment Certificate
A certificate prepared for equipment other than an Ex Component. Such equipment may include Ex Components, but additional evaluation is always required as part of their incorporation into equipment.

Equipment (for explosive atmospheres)
General term including apparatus, fittings, devices, components, and the like used as a part of, or in connection with, an electrical installation in an explosive atmosphere.

Equipment Protection Level (EPL)
Level of protection assigned to equipment based on its likelihood of becoming a source of ignition and distinguishing the differences between explosive gas atmospheres, explosive dust atmospheres, and the explosive atmospheres in mines susceptible to firedamp.

A. Equipment Protection Levels (Gas)
EPL Ga
Equipment for explosive gas atmospheres, having a "very high" level of protection, which is not a source of ignition in normal operation, during expected malfunctions or during rare malfunctions.
EPL Gb
Equipment for explosive gas atmospheres, having a "high" level of protection, which is not a source of ignition in normal operation or during expected malfunctions.

EPL Gc
Equipment for explosive gas atmospheres, having a "enhanced" level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp).​
B. Equipment Protection Levels (Dust)
EPL Da
Equipment for explosive dust atmospheres, having a "very high" level of protection, which is not a source of ignition in normal operation, during expected malfunctions, or during rare malfunctions.
EPL Db
Equipment for explosive dust atmospheres, having a "high" level of protection, which is not a source of ignition in normal operation or during expected malfunctions.
EPL Dc
Equipment for explosive dust atmospheres, having a "enhanced" level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp)​
 

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Approved
Acceptable to, and meeting the prescribed standards of, the technical regulator.

Certified I Certification
Assessed by a certifying body and having a certificate number to demonstrate compliance with a Standard

Certifying body
A body acceptable to the technical regulator that provides assurance of compliance of appliances and components with nominated Standards and other accepted safety criteria.

Gas, high pressure
Gas supplied at pressures of over 200 kPa (29 psi) and not exceeding 1050 kPa (152.3 psi).

Gas, low pressure
Gas supplied at pressures of 7 kPa (1.015 psi) or less.

Gas, medium pressure
Gas supplied at pressures of over 7 kPa (1.015 psi) and up to 200 kPa (29 psi).

Relief device
A safety device designed to forestall the development of a dangerous condition by preventing pressure, temperature or vacuum build-up.
 
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