44
CPA operating instructions
1.2 EXPLOSION PROTECTION
units for operation in areas with potentially explosive gases/air
or steam/air atmospheres or inflammable mist
In explosive areas, caused by flammable gases or liquids, the ignition
temperature (lowest temperature at a hot surface) must not be exceeded.
In exceptional cases the surface temperature must not exceed 80% of
the ignition point of the gas in degrees Celsius (°C).
units for operation in dust/air atmospheres
In areas, which are explosive by inflammable dusts, the surface tem-
perature must not exceed ⅔ of the minimum ignition point in °C of the
dust/air mixture. Temperatures of surfaces, which can be subject to
dangerous deposits of ignitable dusts, must be one safety margin lower
than the minimum ignition temperature of the layer which can possibly
be generated by the respective dust. This requires a safety margin of
75 K between the minimum ignition point of a dust deposit and the
surface temperature of the unit. If the dust deposit exceeds a thickness
of 5 mm, larger safety margins are required.
The relevant key data of dusts can be called up via the GESTIS-STAUB-EX
database at www.dguv.de or taken from the HVBG/BIA report 12/97
“Combustion and explosion characteristics of dusts” and be converted:
Starch/milk powder/gelatine
Ignition temperature 390° C x ⅔ = 260° C max. permissible surface
temperature
Wood / grinding dust
Glow temperature 290° C – 75° C = 215° C max. permissible surface
temperature
Classification of the units
Based on comprehensive tests under extreme conditions, the CPA
series can be classified as follows for intended use in general industrial
applications.
II 3 GD c IIB T4 X
II: Equipment group II = other areas
3: Category 3 for zone 2 or zone 22
GD: G for gases, vapours, mists; D for dusts
c: Protection type c = design safety
IIB: Explosion group
T4: Temperature class T4 = 135°C
Fig. 2
EXPLOSION GROuPS AND TEMPERATuRE CLASSES OF SOME GASES AND vAPOuRS (SELECTION)
Ex group
Temperature classes
T1
T2
T3
T4
T5
T6
Ignition temperature range of the mixtures
> 450°C
> 300
≤
450°C
> 200
≤
300°C
Permissible max. surface temperature of the equipment
450°C
300°C
200°C
135°C
100°C
85°C
IIA
Acetone
Acetic anhydride
Petrol (general)
Acetaldehyde
Ammonium
Cyclohexanone
Diesel fuels
Benzene (pure)
Ethanol
Aircraft fuels
Carbon monoxide
i-Amyl acetate
Fuel oil DIN 51603
Ethane
n-Butane
n-Hexane
Ethyl chloride
n-Butanol
Ethyl ethanoate
Kohlenmonoxid
Methane
Methanol
Methyl chloride
Naphthalene
Phenol
Propane
Toluene
IIB
City gas
Ethene
Ethylene oxide
Hydrogen sulphide
Ethyl glycol
Diethyl ether
IIC
Hydrogen
Acetylene
Carbon
disulphide
