Page 560 - Dust Explosions in the Process Industries

Assessment of lgnitability 527

Figure 7.50 Photograph of the version of the
Hartmann bomb shown in Figure 7.49.

Figure 7.51 Glowing resistance wire coil (continuous ignition source) (a) and chemical match
head (instantaneous source) (b) used in Hartmann bomb tests (From Eckhoff, 1976).

nature of the ignition source is not decisive, because the maximum pressure is rather insen-
sitive to the turbulence of the dust cloud at the moment of ignition. For the rate of pres-
sure rise, however, turbulence is a key parameter and the moment of ignition must be
exactly defined (see Section 7.15).
The development of explosion pressure as a function of time is recorded as illustrated
in Figure 7.52 over a range of nominal dust concentrations (dispersed dust mass divided
by bomb volume). Due to statistical scatter, several tests have to be determined at each
nominal dust concentration. A typical set of results is shown in Figure 7.53. This figure