Page 214 - Dust Explosions in the Process Industries

786 Dust Explosions in the Process Industries

Table 2.1 Sequence, relative strengths, and locations of nine successive dust explosions in the
Harbin Linen Textile Plant, Harbin, Peoples Republic of China, March 15, 1987, postulated on the
basis of damage analysis in the plant and a seismic recording of the explosion

Selsmic
Explosion Onset of energy
number explosion (s) (T erg) Location of explosion in plant
1 0.0 50.7 Southern central dust collector
2 0.6 5.4 Northern central dust collector
3 1.2 2.5 Precarding machine
4 1.6 7.6 Carding and prespinning shops
5 3.0 6.8 Eastern dust collectors
6 4.8 1.4
7 6.0 3.9 Undergroundlinen flax stores
a 7.3 2.2
9 8.2 0.45

Table 2.1 summarizes the findings of Xu Bowen et al. (1988) that led to the sugges-
tion of the explosion development indicated in Figure 2.24. According to this scenario,
the explosion was initiated in one of the nine units in the central dust collector system.
All nine units were connected by ducting. The ignition sources were not identified, but
an electrostatic spark was considered a possibility, a local fire or glow another. The ini-
tial flame was transmittedimmediately to the next dust collectingunit and both units (1)
exploded almost simultaneously, giving rise to the first major impact pulse in Figure
2.25(B). The explosion then propagated through the other seven dust collecting units in
the central collecting plant (2), and into the precarding area, where the blast wave pre-
ceding the flame generated an explosible dust cloud in the room, which was ignited by
the flamejet from the dust collectors (3). The room explosion propagated further to the
carding and prespinning shops (4), right up to the eastern dust collectors, where another
distinct explosion (5) occurred. The final four explosion pulses were generated as the
explosion propagated further into the underground linen flax stores, where it finally ter-
minated after having traveled a total distance of about 300 m. The chain of nine explo-
sions lasted for about 8 seconds.

2.9.3
EXPLOSION INITIATION AND DEVELOPMENT, SCENARIO 2

This alternative scenario originates from the investigation of Zhu Hailin (1988), who
found evidence of an initial smoldering dust fire caused by a live 40 W electricalportable
light lamp lying in a flax dust layer of 6-8 cm thickness in a ventilation room. He also
found evidence of flame propagation through the underground tunnels for the dust col-
lection ducting. On the basis of his analysis, Zhu suggested that the explosion was ini-
tiated in the eastern dust collectors (5 in Figure 2.24) from which it transmitted to nine
units of the central dust collecting plant (1 and 2 in Figure 2.24) via the ducting in the
underground tunnels. Severe room explosions were initiated when the ducting in the