There are eight recognised concepts of explosion protection within Europe. These are detailed in the European EN 60079 series of Standards shown below
There are four basic methods utilised in order to avoid un-controlled ignitions and we recommend reviewing EN 1127 for further guidance available from BSI, cover page shown opposite
Exclusion of the flammable substance.
Prevention of component sparks or hot surfaces.
Explosion quenching.
Energy limitation.
By applying individually or in combination, the following protection concepts are applied to equipment in order to achieve this.
Protection Concept |
Zone of use |
ATEX Category |
Methodology |
|
Intrinsic Safety |
ia |
0, 1, 2 |
1 |
Limited energy - will not cause ignition in normal operation, with one fault and with any combination of two faults applied |
ib |
1, 2 |
2 |
Limited energy - will not cause ignition in normal operation, with one single fault applied |
|
ic |
2 |
3 |
Limited energy - will not cause ignition in normal operation |
|
Flameproof |
d |
1, 2 |
2 |
Explosion containment, will not allow transmission of an internal explosion to the surrounding environment |
Increased Safety |
e |
1, 2 |
2 |
Prevention of arcs, sparks and hot surfaces in normal operation |
Pressurization |
p |
1, 2 |
2 |
Excludes the hazardous atmospheres by 50Pa positive pressure of inert gas |
Powder Filled |
q |
1, 2 |
2 |
High power electronics, such as solenoids, capacitors etc. prevents the explosive atmosphere reaching a hazard |
Encapsulation |
m |
1, 2 |
2 |
Light current applications and instrumentation |
Oil Filled |
o |
1, 2 |
2 |
High current switchgear, transformers etc. prevents the explosive atmosphere reaching a hazard |
Non Sparking |
n |
2 |
3 |
Is not capable of causing an ignition and faults are unlikely to occur |
Mechanical Equipment
There are seven recognised concepts of explosion protection for non-electrical equipment within Europe.
These are detailed in the European EN 13463 series of Standards shown below
Type “n” equipment protection measures are shown below for completeness, in essence they are simplified versions of the main electrical protection concepts
Type "n" Protection Concepts |
|
Non sparking |
EEx nA |
Restricted breathing |
EEx nR |
Simplified Pressurization |
EEx nP |
Energy limiting apparatus |
EEx nL |
Sealed device |
EEx nC |
Enclosed break |
EEx nC |
Hermetically sealed |
EEx nC |
Encapsulated |
EEx nC |
Protection Concept |
Zone of use |
ATEX Category |
Methodology |
|
Constructional Safety |
c |
0, 1, 2 |
1 |
Constructional measures are applied so as to protect against the possibility of ignition from hot surfaces, sparks and adiabatic compression generated by moving parts |
Inherent Safety |
g |
1, 2 |
2 |
Prevention of arcs, sparks and hot surfaces in normal operation |
Control of Ignition |
b |
1, 2 |
2 |
Automatic/manual ignition prevention measures, to prevent potential ignition sources becoming effective |
Pressurization |
p |
1, 2 |
2 |
Excludes the hazardous atmospheres by 50Pa positive pressure of inert gas |
Flameproof |
d |
1, 2 |
2 |
Explosion containment, will not allow transmission of an internal explosion to the surrounding environment |
Liquid Immersion |
k |
1, 2 |
2 |
A type of protection in which potential ignition sources are made ineffective |
Flow Restriction |
fr |
2 |
3 |
Flow restricting enclosures are simple enclosures, which will prevent, with adequate probability, the atmosphere inside the enclosures becoming explosive |
The Protective measures shall be considered or applied in the following order
Ensure ignition sources can not arise (protection concept c)
Ensure ignition sources can not become effective (protection concept g and b)
Prevent explosive atmosphere reaching ignition sources (protection concept fr, p and k)
Contains the explosion and prevent flame propagation (protection concept d)