Page 153 - Dust Explosions in the Process Industries

126 Dust Explosions in the Process Industries

and the operational requirements themselves may change. However, it is also quite pos-
sible that safety standards fall off with time because experience of satisfactory opera-
tion leads to overconfidenceand a false sense of security.
For these reasons, safety audits are used in many operating companies.These may vary
from a half-day tour by the works manager to a review lasting several weeks carried out
by a team of engineers covering different disciplines and independent of the regular oper-
ational management of the plant. For the most penetrating audits, the study should not
be announced in advance.
In practice, the assessment of dust explosion hazards is bound to be subjective,because
the problem is too complex for quantitative analytical methods to yield an indisputable
answer. In Figure 1.140,four different scenarios for a given industrialplant are indicated.

LOW

Y
v,
c
z
0
wl
0
-I
Q
25
c
wl
3
0

I
TRAINING PREVENTING CONTROL OF ISOLATION
MOTIVATION IGNITION DUST CONC. VENTING
ORGANIZATION SOURCES INERTING CONTAINMENT
HOUSEKEEPING SUPPRESSION
MAINTENANCE

Figure 1.I 40 Effect of various means of preventing and mitigating dust explosions. Four different
scenarios for a given plant. Extended and generalized presentation based on an originalscenario (A)
by Pinkwasser and Haberli (1987).

ScenarioA, which was assumedby Pinkwasser and Haberli (1987)for the grain, feed,
and flour industry, suggests that most of the dust explosion hazard can be eliminated by
“soft” means, such as training, motivation, improving the organization, good house-
keeping, and proper maintenance.The alternative scenario (B) suggeststhat concentrating