P_max AND (dP/dt)_max

 

[EN 14034-1 and 14034-2; ASTM E 1226]

 

The powder to be tested is blown into a 20-ℓ-Apparatus and the resulting dust cloud is ignited with two chemical igniters, having a total ignition energy of IE = 10.000 J.

 

The ignition delay time (turbulence level) in the 20-l-Apparatus is tv = 0,06 s.

 

The pressure inside the sphere is recorded.

 

By variation of the dust concentration, the most critical conditions are determined (three test series).

 

To characterize the explosion of the powder P_max and K_max are determined.

 

K_max is the maximum rate of pressure rise normalized for a container size of 1 m³.

 

K_max = (dP/dt)_max x V^1/3 [bar·m/s]

 

P_max is the maximum explosion overpressure starting from an initial pressure of 1 bar.

 

Based on the K_max values the dust is classified into several dust explosion classes St:

 

Dust explosion constant Kmax [bar·m/s]	Dust explosion class St	Maximum explosion overpressure Pmax [bar]
0 < Kmax ≤ 200	St 1	≤ 10
200 < Kmax ≤ 300	St 2	≤ 10
Kmax > 300	St 3	≤ 12

 

P_max and K_max or the dust explosion class St are the basis for the design of constructive explosion protection measures.