Standard Test Method for Explosibility of Dust Clouds

Importancia y uso:

5.1 This test method provides a procedure for performing laboratory tests to evaluate deflagration parameters of dusts.

5.2 The data developed by this test method may be used for the purpose of sizing deflagration vents in conjunction with the nomographs and equations published in NFPA 68, ISO 6184/1, or VDI 3673.

5.3 The values obtained by this testing technique are specific to the sample tested and the method used and are not to be considered intrinsic material constants.

5.4 For dusts with low K_St values, discrepancies have been observed between tests in 20-L and 1-m³ chambers. A strong ignitor may overdrive a 20-L chamber, as discussed in Test Method E1515 and Refs (1-4).8 Conversely, more recent testing has shown that some metal dusts can be prone to underdriving in the 20-L chamber, exhibiting significantly lower K_St values than in a 1-m³ chamber (5). Ref (6) provides supporting calculations showing that a test vessel of at least 1-m³ of volume is necessary to obtain the maximum explosibility index for a burning dust cloud having an abnormally high flame temperature. In these two overdriving and underdriving scenarios described above, it is therefore recommended to perform tests in 1-m³ or larger calibrated test vessels in order to measure dusts explosibility parameters accurately.

Note 5: Ref (2) concluded that dusts with K_St values below 45 bar m/s when measured in a 20-L chamber with a 10 000-J ignitor, may not be explosible when tested in a 1-m³ chamber with a 10 000-J ignitor. Ref (2) and unpublished testing has also shown that in some cases the K_St values measured in the 20-L chamber can be lower than those measured in the 1-m³ chamber. Refs (1) and (3) found that for some dusts, it was necessary to use lower ignition energy in the 20-L chamber in order to match MEC or MIC test data in a 1-m³ chamber. If a dust has measurable (nonzero) P_max and K_St values with a 5000-J or 10 000-J ignitor when tested in a 20-L chamber but no measurable P_max and K_St values with tests conducted using an ignition source less than or equal to 2500 J, it may be helpful to test the material in a larger chamber such as a 1-m³ chamber using at least a 10 000-J ignition source to further characterize the material’s explosibility in dust cloud form.

Subcomité:

E27.05

Referida por:

E2931-13R19, E1515-14R22, E1491-06R25, E2019-03R25, E1445-08R23

Volúmen:

14.01

Número ICS:

13.230 (Explosion protection), 17.100 (Measurement of force, weight and pressure)

Palabras clave:

dust explosion; explosion pressure;