|
Where potentially
explosive atmospheres are present, equipment and systems need
to employ a method of protection to prevent ignition of external
gases or dusts. The following methods of protection are commonly
used:
|
Protection Method
|
Code
|
Zone
|
N.American Practice
|
Division
|
General
Principle
|
|
Flameproof
|
EEx d
|
1, 2
|
Explosion- proof
|
(1), 2
|
Contain the explosion,
quench the flame. |
|
Powder-filling
|
EEx q
|
1, 2
|
Not Recognised
|
-
|
|
Pressurisation
|
EEx p
|
1, 2
|
Purging
|
1, 2
|
Keep
flammable gas out.
|
|
Encapsulation
|
EEx m
|
1, 2
|
Not Recognised
|
-
|
|
Oil-immersion
|
EEx o
|
1, 2
|
Oil-immersion
|
1, 2
|
|
Increased Safety
|
EEx e
|
0, 1, 2
|
Not Recognised
|
-
|
No
arcs, sparks or hot surfaces.
|
|
Intrinsic Safety
|
EEx ia
|
0, 1, 2
|
Intrinsic Safety
|
1, 2
|
Limit
energy of sparks and surface temperature
|
|
EEx ib
|
1, 2
|
Not Recognised
|
-
|
| European &
IEC Classification |
Criteria |
North American Equivalent |
| NEC 500 |
NEC 505 |
Zone 0
(gases)
Zone 20 (dusts) |
Flammable material
present continuously or for long periods (typically >1000
hours per year) |
Division 1
(gases & dusts) |
Zone 0 |
Zone 1
(gases)
Zone 21 (dusts) |
Flammable material
present in normal operation (typically >10 and <1000
hours per year) |
Division 1
(gases & dusts) |
Zone
1
|
Zone 2
(gases)
Zone 22 (dusts) |
Flammable material
present in abnormal conditions only for short periods (typically
<10 hours per year) |
Division 2
(gases & dusts) |
Zone 2 |
|
Gas / Vapour
|
Apparatus group required |
Temperature class required |
| Acetic acid |
IIA
|
T1
|
| Acetone |
IIA
|
T1
|
| Acetylene |
IIC
|
T2
|
| Ammonia |
IIA
|
T1
|
| Butane |
IIA
|
T2
|
| Cyclohexane |
IIA
|
T3
|
| Ethanol (ethyl alchohol) |
IIA
|
T2
|
| Ethylene |
IIB
|
T2
|
| Hydrogen |
IIC
|
T1
|
| Kerosene |
IIA
|
T3
|
| Methane (natural
gas) |
IIA (non mining)
|
T1
|
| Methanol (methyl alchohol) |
IIA
|
T1
|
| Methyl ethyl ketone (MEK) |
IIA
|
T1
|
| Propane |
IIA
|
T1
|
| Propan-1-ol (n-propyl alchohol) |
IIB
|
T2
|
| Propan-2-ol (iso-propyl alchohol) |
IIA
|
T2
|
| Tetrahydrofuran (THF) |
IIB
|
T3
|
| Toluene |
IIA
|
T1
|
| Xylene |
IIA
|
T1
|
|