POWER May 2011 - 79

HEALTH & SAFETY
stockpiling, reclaiming, rat-holing, and dust
generation from vibrating equipment. All
these challenges must be handled during the
engineering phase of a project or by assessing
and determining problems during the operations
phase.
The often-neglected fly ash-handling
systems and others areas of the plant that
regularly experience dispersed fly ash and
pulverized fuel mixtures also represent
sources of combustible dust. Remember, fly
ash concentrations as low as 6% to 10% by
mass are explosive.
Five Factors Contributing to
Combustible Dust Explosions
For a dust explosion to occur, five conditions
must be met:
■ A fuel source.
■ An oxidant.
■ An ignition source.
■ Dispersion of the dust into a cloud.
■ Some form of confinement of the dust
cloud.
These conditions are often referred to as
the " explosion pentagon " (Figure 3).
In a typical power generation facility,
the fuel is commonly the material burned to
generate power. The oxidant is commonly
3. Explosion pentagon. For a dust explosion
to occur, five conditions must be met.
Unfortunately, all the components required for
a dust explosion are quite common in many
coal-fired power plants. Courtesy: P2
3. Ignition source
4. Dispersion
Explosion
5. Confinement
oxygen in the air. The ignition source can
be self-heating fuel, a hot surface, electrostatic
discharges from pulverized coal, an
open spark, unrated electrical equipment, hot
work, or an open flame/fire. Confinement
can be provided by the process equipment
or the structure in which the equipment is
housed. Dispersion can occur from fuel- or
waste-conveying activities or during an upset
condition. Unfortunately, all the components
required for a dust explosion are quite common
in the power generation industry (Figure
4).
The PRB Coal Users' Group and
OSHA Initiatives
The PRB Coal Users' Group (PRBCUG)
asked that I serve as director of governmental
affairs, responsible for tracking the regulations
and administrative efforts being carried
out by the U.S. Occupational Safety and
Health Administration (OSHA). This role
frequently takes me to Washington, D.C.
OSHA has made significant inroads in
completing a new combustible dust standard.
In fact, at press time, the proposed standard
was scheduled to be released for preliminary
introduction to the small business community.
However, despite impressive efforts of the
groups within OSHA working toward completion
of this new standard, the constantly
changing political landscape is creating heavy
counter-currents that are interfering with its
timely completion. I have been impressed
with OSHA's efforts to assist industry while
staying sensitive to the need to avoid the enactment
of any regulation that overreaches.
In 2009 and 2010, the PRBCUG requested
1. Combustible
dust (fuel)
2. Oxygen
in air
4. Dusty breeze. Acute coal dust dispersion
is combustible and respirable. Courtesy: P2
input from members of the electric power industry,
which, in turn, was passed to OSHA
without identification of those companies
that wished to remain anonymous. We have
represented ourselves as a clearinghouse for
such information, without exceeding the limits
of our tax status. Our group has gained
a fair amount of attention that has given
us better access to key individuals within
the Department of Labor and the Chemical
Safety Board (CSB). We did this by introducing
ourselves as an industry that annually
handles more than 150 million tons of <100
mesh combustible dust (by the time it gets
to the boiler), which has a Kst (dust deflagration
index) more than 2.5 times that of sugar
and other bituminous coals. Explaining our
group's background has given it better access
to OSHA to discuss the very latest problems
and the progress of the new combustible dust
standard.
Living with the Current OSHA Rule
The OSHA National Emphasis Program
(NEP) for combustible dust is very spe78
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cific
in its guidelines about how workers
should handle utility coal. Currently, there
are several congressmen in Washington,
D.C., who routinely push for a temporary
combustible dust rule. (See " Proposed
Combustible Dust Rule Sparks Debate "
in our Mar. 2011 issue or online at www.
powermag.com.) However, a temporary
rule may not be effective because of the
ambiguity and confusion it would cause.
The existing NEP is sufficient; it is actionable
now, we know its intent, and we have
some history concerning how inspectors
and judges have interpreted it.
In addition, we should be confident that
the current direction of the NEP is worth
our compliance investment and that the
eventual new combustible dust standard
will not cause the abandonment of mitigation
actions or projects due to any major
regulatory change.
Plant Professionals (P2) has been advising
customers that the new standard may
follow a different rule-of-law for enforcement
and a different level of detail. However,
the general theory governing safety
and the avoidance of hazardous incidents
will not differ from the current NEP. In
short, don't ignore the protection of your
workers and your facility while waiting for
the new standard.
Promoting Safe Management of
Combustible Dust
The top priority is to stay safe. P2 staff spend
a lot of time traveling around the globe teaching
and advising coal-based power generation
companies. We focus on key tools need
to promote combustible dust safety. I review
and emphasize the following two tools at the
end of each training session.
Conducting Plant Assessments. These
evaluations are the single most significant
step the staff at any power station can take
to gain an understanding of the gap between
good practice/regulations and actual current
plant conditions. This, in turn, helps a plant
choose low-hanging fruit and create a plan
focused on improving safety and risk management.
P2
has implemented more than 150 assessments
of coal-fired power stations in
the U.S., Europe, and Asia. The best indication
of assessment quality is how well
the document is utilized for planning and
its operational clarity. Engineers are not
the best source of such documents; a thorough
gap analysis is better. Gap analysis is
a tool that helps a company to compare its
actual performance with its potential performance.
Operators can provide focused
and accurate gap analyses, which can include
the following:
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POWER May 2011

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