POWER April 2014 - 86

PLANT SAFETY
Also, electrical equipment located above
the suspended ceiling was not rated for use
around combustible dust (Figure 5).
The post-incident investigation found that
employees were not trained about the hazards
of combustible dust. OSHA, local fire
department, and insurance company inspectors
inspected the plant, although none made
comment about the potential for a dust explosion.
The CSB determined that if the company
had " adhered to NFPA standards for
combustible dust, the explosion could have
been prevented or minimized. "
The second incident occurred in an aluminum
products manufacturing plant in Indiana,
where an explosion killed one worker
and injured several others. The plant recycled
scrap aluminum produced by its production
line and fed it into a melt furnace. Transporting
the aluminum scrap produced aluminum
dust that was sucked into a dust collector.
The explosion occurred in an inadequately
vented and cleaned dust collector that was located
too close to the scrap processing area.
" The initial explosion spread through ducting,
causing a large fireball to emerge from
the melt furnace. " Dust was also present on
overhead beams and other structures that was
lofted as a result of the first explosion.
The proximate cause of the fire that
burned the facility to the ground was a dust
collector that was " not designed or maintained
to prevent dust explosions. " Neither
the owner nor regulators adequately investigated
earlier dust fires at the facility, nor
were any process changes made. Again, the
CSB determined that if the company had
" adhered to the NFPA standard for combustible
metals, the explosion could have been
prevented or minimized. "
The third major eruption occurred in a
facility located in Kentucky that produced
acoustic insulation for automobiles. The explosion
claimed the lives of seven workers,
injured 37, and completely destroyed the
facility. According to the CSB, " the manufacturing
process began by impregnating a
fiberglass mat with phenolic resin, and then
used air to draw the resin into the fiberglass
webs. On the day of the explosion, a curing
oven that had been left open because of a temperature
control problem likely ignited the
combustible resin dust stirred up by workers
cleaning the area near the oven. "
With the knowledge of plant managers,
dust had accumulated throughout the manufacturing
facility in dangerous amounts. The
production process used compressed air for
cleaning, often blowing large amounts of resin
dust into the air. Again, Kentucky OSHA,
state fire marshals, and insurance company
safety inspectors had inspected the facility,
but all failed to recognize the combustible
86
dust hazard. Again, the CSB determined that
if the company had " adhered to NFPA standards
for housekeeping and fire/explosion
barriers, the explosions could have been prevented
or minimized. "
OSHA Resists Issuing Dust Safety
Regulations
The CSB report on the hazards of dust in the
workplace was released to the public at a
Washington, D.C., press conference on Nov.
9, 2006. The CSB's two-year study called for
OSHA to prepare a new regulatory standard
" designed to prevent combustible dust fires
and explosions. " The report noted that there
is no comprehensive federal safety regulation
designed to prevent dust explosions and that
engineers, regulators, fire inspectors, and insurance
companies are generally unaware of
dust explosion hazards.
Also, there were common causal factors
shared by the three tragedies mentioned
above. First, the hazards of dust were not
adequately communicated to employees. The
Material Safety Data sheets " do a poor job of
informing workers of dust explosion hazards
and the OSHA regulation for hazard communication
. . . do not address combustible
dust. " Second, each plant produced dust that
accumulated on structures in excess of the
NFPA standard that warns that layers 1/32nd
of an inch thick, less than the thickness of a
dime, can constitute a hazardous condition.
Finally, any material that will burn in air can
become a combustible dust.
OSHA's response since release of the CSB
report has been silence. On July 25, 2013,
the CSB at a follow-up public meeting in
Washington, D.C., " declared the response by
OSHA . . . on combustible dust . . . to be 'unacceptable.'
"
The CSB also " voted to make adoption of
a combustible dust standard . . . first priority
in the CSB's recently established 'Most
Wanted Safety Improvements Program.' " To
its credit, the CSB has taken its case public
and promises " stepped-up advocacy " for
regulations that can prevent dust explosions.
The CSB stated that it strongly believes the
regulatory changes suggested in its 2006 report
will prevent similar incidents and will
save lives.
The CSB noted that OSHA " recognized
the importance of NFPA's dust standards "
by including fugitive dust as a " National
Emphasis Program that OSHA began last
year and reissued earlier this year [2013]. "
However, without a comprehensive standard,
businesses and regulators don't know which
NFPA standard applies, so compliance requirements
aren't clearly stated.
Since the release of CSB's 2006 investigative
report, dust explosions have continued
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to occur. For example, an explosion occurred
at a sugar company in February 2008 caused
by large accumulations of powdered sugar, in
a plant were the powder accumulations were
often up to " mid-leg " height or was airborne
in the facility, often making it difficult to
see across the plant. Fourteen workers were
killed and 36 were injured. The subsequent
investigation found much of the electrical
equipment in the plant was not dust-tight and
the dust collection system was inadequate.
Another CSB investigation continues on
the December 2010 dust explosion at a West
Virginia plant processing titanium powder
that claimed the lives of three workers and
at a Tennessee plant where multiple iron dust
flash fires combined with a hydrogen explosion
that destroyed a plant in January 2011,
killing three workers.
In the power industry, there have been
many coal-dust related explosions that
caused injury and property damage over the
years for these very same reasons. It appears
the turning point for the power industry was
the secondary coal dust explosion at Ford's
River Rouge manufacturing plant, located in
Dearborn Mich., in February 1999 that killed
six workers and injured 36. According to the
Michigan OSHA investigative report, housekeeping
failed to control accumulations of
coal dust throughout the plant. The triggering
event was a relatively small natural gas
explosion in the power plant, but the shock
wave shook free suspended dust accumulations
that produced a massive secondary coal
dust explosion that caused the majority of the
damage to the plant.
In 2000, the Powder River Basin Coal
Users' Group (PRBCUG) was formed to address
the " safe, efficient, and economic use "
of PRB coal, which is more prone to secondary
explosions than other types of coal.
Members of the PRBCUG and POWER have
written extensively about how to avoid coal
dust explosions since that time. The PRBCUG
has also produced webinars on the
topic and its Powersafe Combustible Dust eLearning
course, " Combustible Dust Awareness
for Coal, " is available online (www.
prbcoals.com).
The excellent work of the PRBCUG in educating
plant owners and workers about the
danger of poor coal dust housekeeping and
for providing a forum in which experiences
can be shared has helped make a significant
reduction of major coal dust-caused incidents
in the power industry over the past few
years. Complacency often follows success so
learn from the experiences of others and take
a fresh look at your plant's safety program.
There is always room for improvement. ■
-Dr. Robert Peltier, PE is POWER's
consulting editor.
POWER | April 2014
http://www.prbcoals.com http://www.powermag.com
POWER April 2014

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