Application in Explosive Environments • 309
Modular I/O System
ETHERNET TCP/IP
8.3.5
Types of ignition protection
Ignition protection defines the special measures to be taken for electrical com-
ponents in order to prevent the ignition of surrounding explosive atmospheres.
For this reason a differentiation is made between the following types of igni-
tion protection:
Identifi-
cation
CENELEC stan-
dard
IEC stan-
dard
Explanation
Application
EEx o
EN 50 015
IEC 79-6
Oil encapsulation
Zone 1 + 2
EEx p
EN 50 016
IEC 79-2
Overpressure encap-
sulation
Zone 1 + 2
EEx q
EN 50 017
IEC 79-5
Sand encapsulation
Zone 1 + 2
EEx d
EN 50 018
IEC 79-1
Pressure resistant
encapsulation
Zone 1 + 2
EEx e
EN 50 019
IEC 79-7
Increased safety
Zone 1 + 2
EEx m
EN 50 028
IEC 79-18
Cast encapsulation
Zone 1 + 2
EEx i
EN 50 020 (unit)
EN 50 039 (system)
IEC 79-11
Intrinsic safety
Zone 0 + 1 + 2
EEx n
EN 50 021
IEC 79-15
Electrical components
for zone 2 (see below)
Zone 2
Ignition protection “n“ describes exclusively the use of explosion protected
electrical components in zone 2. This zone encompasses areas where explosive
atmospheres can only be expected to occur rarely or short-term. It represents
the transition between the area of zone 1, which requires an explosion protec-
tion and safe area in which for instance welding is allowed at any time.
Regulations covering these electrical components are being prepared on a
world-wide scale. The standard EN 50 021 allows electrical component manu-
facturers to obtain certificates from the corresponding authorities for instance
KEMA in the Netherlands or the PTB in Germany, certifying that the tested
components meet the above mentioned standards draft.
Type “n” ignition protection additionally requires electrical components to be
marked , with the following extended identification:
•
A – non spark generating (function modules without relay /without
switches)
•
AC – spark generating, contacts protected by seals (function modules with
relays / without switches)
•
L – limited energy (function modules with switch)
i
Further information
For more detailed information please refer to the national and/or international
standards, directives and regulations!