Determination of Dust Explosion Parameters
In accordance with the specification R 003 6/2000 of the Chemical Industry Trade Co-operative Association, a 20 l dust explosion sphere or a 1 m³ vessel serves as a standard laboratory apparatus which is suitable for examining explosive gases, fumes and dusts. The maximum operating pressure is 25 bar. The following parameters, among others, are determined in this sphere:
- Maximum explosion pressure
- Maximum speed of pressure increase
- K values for division into explosion classes
- Explosion limits
- Oxygen limit concentrations
In connection with dust explosions the maximum pressure pmax and the maximum pressure increase over time (dp/dt)max are determined for the explosion of a dust/air mixture in closed vessels at optimum concentration.
A dust in the respectively examined form (e. g. grade, humidity) is not explosive when no ignition occurs over a wide range of concentration (at least 30–2000 g/m³).
A material can only be classified as "non-dust-explosive" if exothermal oxidation reactions can be ruled out by its chemical characteristics or if the examinations of the explosiveness have not led to an explosion either for fine dust (< 63 µm).
The maximum pressure increase over time is volume-dependent. The product of the maximum pressure increase over time and the cubic root of the volume concerned is constant (cubic law) and is known as the KSt-value.
Different explosion classes can be defined for combustible dust based on this:
| KSt-Wert | Staubexplosionsklassen |
| < 200 bar m s-1 | St 1 |
| < 300 bar m s-1 | St 2 |
| > 200 bar m s-1 | St 3 |
The dust explosion class only gives a recommendation for which protection concept or what constructive explosion protection measures are to be applied in connection with dust explosions.