OSHA Inspection: CORRECT BUILDING PRODUCTS LLC

Issued

Jun 23, 2005

Abate by

Jul 26, 2005

Penalty

Initial $2,500 · Current $1,250 Reduced

General-duty citation text

Section 5(a)(1) of the Occupational Safety and Health Act of 1970:
The employer did not furnish employment and a place of employment
which were free from recognized hazards that were causing or likely
to cause death or serious physical harm to employees in that
employees were exposed to wood dust fire and explosion hazards:
Production Area - Employees were exposed to wood dust fire and
explosion hazards due to lack of control systems or due to
inadequate control systems, including systems to eliminate or
control sources of ignition:
The following conditions contributed to wood dust fire and
explosion hazards:
a)The potential of hot particles being drawn from inside an
extruder and becoming a source of dust ignition
downstream in the:
1.Dust collection lines at the extruder mixing
hoppers that run to the dust collectors
2.Open auger dust feed lines (under no/low feed
conditions)
3.Blue bin transfer hopper
4.Dust collector(s) and lines to the dust collector
These conditions may have caused the wood dust explosion in
the blue bin transfer hopper, the wood dust fire in the #2
extruder dust feed system, the dust collection ductwork, and
the dust collector, on May 8, 2005.
b)The blue bin transfer hopper was a totally enclosed
space; a concentration of dust in the explosive range in
combination with a source of ignition could have resulted
in a dust explosion, as occurred on May 8, 2005.
b(1)On 06/09/05, after permanent openings in the top of the
hopper had been made, excessive fugitive dust emissions
were emitted from the blue bin transfer hopper as
evidenced by the accumulation of 7 millimeters of layered
wood dust on top of the hopper.  NFPA 664 8.2.3.1.2
requires: "All equipment shall be designed to minimize
fugitive dust emissions from the equipment."
c)The bridge breaker in the blue bin transfer hopper did
not effectively maintain dust feed to extruder supply
augers.
d)The vacuum created by the dust collector on the upstream
dust feed system was excessive.  This high vacuum on the
blue bin transfer hopper, on the wood dust feed auger
lines to the extruder (when they were open and not full
of wood dust under no/low feed conditions), and on the
vertical feed lines and throat to the extruder (at no/lowfeed conditions)
increased the likelihood of hot
particles being drawn into the above system and resulting
in the ignition of wood dust somewhere in this system.
e)The operation (and valve configuration) of the vacuum
cans at the extruder allowed outside air into the
extruder which ignited hot particles inside the extruder
that became sources of ignition for wood dust under the
high vacuum/no dust feed conditions described in (d)
above.
f)The wood dust feed supply to the extruders was often lost
due to inadequate controls on the wood dust levels in the
blue bin transfer hopper and the wood dust supply to this
hopper.
g)Sparks or propagating flame in the ductwork caused a fire
at the dust collector.
h)The potential of sparks being produced (and becoming
sources of dust ignition) by the "chattering" of the
steel feed supply augers against the steel pipe auger
casings, under no/low dust feed conditions.
i)The hot external surfaces of the extruders, especially
near the feed throats, were not adequately sealed and
protected from contacting wood dust.  Dust accumulation
at the extruder throat have became hot embers and
potential sources of dust ignition for accumulations of
dust on the extruder and on the horizontal flanges and
surfaces of the vertical feed system (mixing hoppers,
scales, duct flanges, etc).
j)Dust accumulated on horizontal surfaces including
equipment tops (i.e. the blue bin transfer hopper), the
horizontal surfaces of the vertical feed system to the
extruders, including tops of hoppers, scales, horizontal
duct flanges, etc.)
k)Extruder heating plates had the potential to exceeding
normal operation temperatures and become sources of
ignition.  No high temperature alarms or interlocks were
present.
l)Static electricity was a potential source of ignition.
Plastic piping in line between steel piping could
possibly create differences in electrical potential that
could produce a build up of static charge.
m)Rogue stone and rogue metal (iron and steel) that was
carried through the feed system was a source of ignition.
n)The red coloring containing iron reduced the
effectiveness of the magnet in the extruder throat feed
to capture rogue iron or steel.
It is recommended that NFPA 664 - Standards for the Prevention
of Fires and Explosions in Wood Processing Facilities--be
followed for feasible control methods and good practices.  A
process hazard analysis of the system is recommended using the
What If-Check List method (using NFPA 664 as the check list)
or the Haz Op method as described in 1910.119(e) or by the
Center for Process Safety of the American Institute of
Chemical Engineers.
Among the feasible methods of controls for the conditions
described above include:
In general, install spark suppression systems at key points in
the system that have or may encounter potential ignition
sources.
(Note:  The control method a) below corresponds to hazard a)
above; hazard b) is linked to control method b), etc.)
a)Eliminate the possibility of hot particles from the
extruder being drawn into the feed system and into the
dust collection lines at the extruder mixing hoppers by:
1)Installation of a spark suppression system at the
feed (throat) to the extruder, or
2)Apply a nitrogen blanket to the extruder feed that
is interlocked with and triggered by a low throat
feed level (or some other suitable trigger).
b)Provide permanent openings in the top of the blue bin
transfer hopper to eliminate the explosion potential of
a totally enclosed space.
b(1)Redesign the openings in the top of the blue bin transfer
hopper to prevent fugitive dust emissions while keeping
smaller openings to eliminate the explosion potential of
a totally enclosed space.
c)Install an effective bridge breaker near the bottom of
the blue bin transfer hopper to maintain dust feed to
extruder supply augers.  Provide a dust supply header at
the blue bin to more evenly distribute dust feed across
the width of the bin.  Install automatic stop valves in
the auger lines that are interlocked with the low feed
supply sensors.
d)Dramatically reduce the vacuum created by the dust
collector on the upstream dust feed system to reduce the
likelihood of hot particles being drawn into the system
from the extruder at no/low feed conditions.e)Reconfigure vacuum can
valves and change procedures to
not allow outside air into the extruder at no/low feed
conditions.
f)Install level sensors and feed sensors in the blue bin
transfer hopper to control feed and to maintain levels in
the blue bin that cover the intake to the auger feed
lines.  This will reduce the potential of vacuum on the
auger feed lines drawing hot particles from the
extruders.  Create work practices that do not allow the
auger feed system run out of sawdust.
g)Install a spark suppression system at each dust
collector.
h)Maintain the auger feed lines in the "full" condition and
provide an emergency interlock and alarm when the auger
feed lines approach a no/low feed condition.  Create work
practices that do not allow the auger feed system run out
of sawdust.
i)Improve the insulation and dust seal at the extruder
throats to prevent hot dust embers from forming.
k)Provide audible and visual alarms and interlocks on the
extruder heating plates and thermocouple to prevent
plated from exceeding normal operation temperatures.
l)Evaluate whether plastic piping is actual a legitimate
source of ignition.  Determine whether all parts of the
system are grounded and at the same electrical potential.
m)Install screens to catch stones.
n)Substitute a non-iron containing coloring.
Note:  Employees must be trained in the engineering and work
practice controls to prevent wood dust fire and explosion as
described in instances a) thru n) above.

Issued

Jun 23, 2005

Abate by

Jul 26, 2005

Penalty

Initial $1,750 · Current $875 Reduced

Issued

Jun 23, 2005

Abate by

Jun 29, 2005

Penalty

Initial $375 · Current $188 Reduced

Issued

Jun 23, 2005

Abate by

Jul 26, 2005

Penalty

Initial $1,750 · Current $875 Reduced