| Ex-Info : Some Basics about Explosion |
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| Definition explosive atmosphere : |
Mixture
from air and flammable substances e.g.
gases, vapours, mists or types of dust under
atmospheric conditions,in which the
burning process is passed after ignition to
the entire unburned mixture.
Atmospheric Conditions:
Mixture pressure 0.8 bar to 1.1 bar and
Mixture temperature -20°C to +60°C |
| How to Avoid Explosion? |
Avoidance of the simultaneous occurrence of:
– Flammable substances (gases, vapours, mists or dusts)
in dangerous quantities
– Oxygen
– Ignition source (Energy in the form of heat or sparks) |
| Lower and Upper Explosion Limits |
Lower Explosion Limit (LEL):
The lower explosion limit is the concentration of a mixture,
that is not yet combustible
(mixture is too lean)
Upper Explosion Limit (UEL):
The upper explosion limit is the maximum concentration
of a mixture, that is still combustible
(mixture is too rich) |
| Lower and Upper point of explosion
further examples |
| Material |
LEL [Vol.-%] |
UEL [Vol.-%] |
| Acetaldehyde |
4,0 |
60,5 |
| Acetone |
2,5 |
13,0 |
| Ethyl alcohol |
3,5 |
15,0 |
| Benzene |
1,2 |
8,0 |
| Diesel fuel |
0,6 |
6,5 |
| Petrol |
0,6 |
8,0 |
| Carbon disulfide |
1,0 |
60,0 |
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| Basic Principle of Safety |
| Safety measures should be made in the following
order: |
| 1) Avoid the formation of explosive atmospheres |
- Prevention of formation of combustible
atmosphere
- outside of the explosion limits
- Inerting
- tightness of equipments
- Ventilation measures
- monitoring of the concentration
- eliminating dust deposits
|
| 2) Avoid the ignition of
explosive atmospheres |
- Energy limited circuits like IS circuits
- Range of the protection measures
- Ignition sources (different types)
|
| 3) Reduce the effects of an explosion |
- Explosionproof Construction
- Explosion Pressure Relief
- Explosion Suppression
- Prevent transfer of exlposion energy
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