140
• Application in Explosive Environments
Classification Meeting CENELEC and IEC
WAGO-I/O-SYSTEM 750
DeviceNet
Explosive Areas Resulting from Gases, Fumes or Mist:
•
Zone 0 areas are subject to an explosive atmosphere
(> 1000 h /year) continuously or for extended periods.
•
Zone 1 areas can expect the occasional occurrence of an explosive at-
mosphere (> 10 h
≤
1000 h /year).
•
Zone 2 areas can expect the rare or short-term occurrence of an explo-
sive atmosphere (> 0 h
≤
10 h /year).
Explosive Areas Subject to Air-borne Dust:
•
Zone 20 areas are subject to an explosive atmosphere
(> 1000 h /year) continuously or for extended periods.
•
Zone 21 areas can expect the occasional occurrence of an explosive at-
mosphere (> 10 h
≤
1000 h /year).
•
Zone 22 areas can expect the rare or short-term occurrence of an explo-
sive atmosphere (> 0 h
≤
10 h /year).
6.3.2 Explosion Protection Group
In addition, the electrical components for explosive areas are subdivided
into two groups:
Group I:
Group I includes electrical components for use in fire-damp
endangered mine structures.
Group II:
Group II includes electrical components for use in all other
explosive environments. This group is further subdivided by
pertinent combustible gases in the environment.
Subdivision IIA, IIB and IIC takes into account that differ-
ent materials/substances/gases have various ignition energy
characteristic values. For this reason the three sub-groups
are assigned representative types of gases:
•
IIA – Propane
•
IIB – Ethylene
•
IIC – Hydrogen
Minimal Ignition Energy of Representative Types of Gases
Explosion Group
I
IIA
IIB
IIC
Gases
Methane
Propane
Ethylene
Hydrogen
Ignition Energy (µJ)
280
250
82
16
Hydrogen being commonly encountered in chemical plants, frequently the
explosion group IIC is requested for maximum safety.
