User Manual

BRITECELL System Manual MN010-04 June 2003 Page 77 of 78
The company has a policy of continuous product development and improvement and we therefore
reserve the right to vary any information quoted without prior notice.
67. APPENDIX C - Classifying hazardous areas
Hazardous Area
A hazardous area is defined as: "An area in which a flammable substance in the
form of gas or vapour or dust, when mixed with air, is present in such proportions
that it can explode when in contact with an ignition source.
Area Classification
Hazardous areas are classified with respect to the potential danger or an explosion,
and the areas are divided into zones:
CONDITIONS CE Code EC
Continuously Hazardous Division 1
Zone 0 - An area in which an explosive gas/air mixture is
continuously present or is present for long periods.
Periodically Hazardous Division 1
Zone 1 - An area in which an explosive gas/air mixture is
likely to occur under normal operating conditions.
Occasionally Hazardous Division 2
Zone 2 - An area in which an explosive gas/air mixture is
unlikely to occur, but if it occurs, it will be of short duration.
Gases & vapour classification
Gases are grouped together basing on the amount of energy required to ignite the
most explosive mixture of the gases with air. Equipment is classified into groups
according to the gases and vapours for which it is suitable and must be selected
with a grouping, which covers the gases and vapours which, will be present where
it is to be installed:
Group Representative Gas Ignition Energy
I
IIA
IIB
IIC
Methane
Propane
Ethylene
Hydrogen
320 Microjoules
300 Microjoules
160 Microjoules
40 Microjoules
GAS CE CODE IEC
Acetylene Class I, Group A Group IIC
Hydrogen, Butadiene, Ethylene Oxide, Propylene Oxide, or Acrolein Class I, Group B Group IIC
Ethylene, Cyclopropane, Ethyl Ether, or Ethylene Class I, Group C Group IIB
Propane, Acetone, Alcohol, Ammonia, Benzine, Benzol, Butane,
Gasoline, Hexane, Laquer Solvent vapours, Naptha, Natural Gas
Class I, Group D Group IIA
Coal Mines
Gaseous Mines Group 1
Combustible Dusts Class II
Ignitable Fibres or Flying Class III
To ensure the suitability of electrical equipment for use in hazardous areas, the
equipment is certified and uses various techniques known as Methods of
Protection. As not all Methods of Protection are suitable for all hazardous areas,
care must be taken to select equipment, which is suitable for use in the Zone in
which it is installed.
Zone 0 Zone 1 Zone 2
Ex ia - Intrinsic safety
Ex s - Special protection i
f
specifically certified for Zone 0
Method suitable for Zone 0
Ex ib - Intrinsic Safety
Ex d - Flameproof enclosure
Ex e - Increased safety
Ex m - Encapsulation
Ex s - Special protection
Method suitable for Zone 0 or l
Ex N - Type of protection N
Ex o - Oil immersion*
Ex q - Powder filling*
Ex p - Pressurised or purging
* may be suitable for Zone 1