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Explosive suction media properties
Minimum Ignition Energy
Minimum Ignition Energy MIE
- Smallest energy that is required for the ignition of the explosive atmosphere
Minimum Ignition Temperature MIT (explosive atmosphere)
- Relevant for the maximum equipment surface temperature
Minimum Glow Temperature (only for dust layer)
- Relevant for the maximum equipment surface temperature
A basic classification can be made in order to decide about suction system specification as follows:
A Standard : | MIE > 10 mj | ST Class 1 or 2 |
B Specific : | MIE 3-10 mj | ST Class 1 or 2 |
C Extreme : | MIE 1 - 3 mj | ST Class 1 or 2 or 3 |
D Highly reactive: | MIE < 1 mj | ST Class 1 or 2 or 3 |
The Kst value is calculated as the equivalent pressure in a 1 m3 sphere from the cube law (Kst value = cube root of volume x explosion pressure rise).
The ST class is based on the Kst value as follows:
ST class 0 - Kst value = 0
ST class 1 - Kst value less than 200 bar m/sec
ST class 2 - Kst value between 200 and 300 bar m/sec
ST class 3 - Kst value greater than 300 bar m/sec
Explosion testing for Kst value & Pmax is essential to validate protection design (explosion venting, explosion suppression and explosion containment). Results of testing from our database for common dusts are shown in the table below.
Kst, Pmax & ST class test results table
| Grain dust | 89bar.m/sec | 9.3bar g | ST1 |
| Coal dust | 85bar.m/sec | 6.4bar g | ST1 |
| Flour | 63bar.m/sec | 9.7bar g | ST1 |
| Sugar | 138bar.m/sec | 8.5bar g | ST1 |
| Wood dust | 224bar.m/sec | 10.3bar g | ST2 |
| Aluminium dust | 515bar.m/sec | 11.2bar g | ST3 |
| Sewage sludge | 102bar.m/sec | 8.1bar g | ST1 |
| GRP dust | 216bar.m/sec | 7.6bar g | ST2 |