CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

Plant personnel reported that the February 20 explosions caused large amounts of dust that had collected
on overhead surfaces (e.g., on top of blend rooms, beams, ledges) to descend upon them. CSB found
accumulations of combustible dust burned onto flat surfaces in the CTA production area. However,
because of the extensive fire and explosion damage, CSB could not determine the thickness of the dust
layer on flat surfaces prior to the fire.
Housekeeping involved cleaning floors and plant equipment on a daily basis. In the year prior to the
incident, the facility’s housekeeping crew for this type of cleaning was reduced in size. The reduced crew
was able to clean a limited area within the plant each day. Daily housekeeping on production lines
became a job duty of line operators.
The CTA cleaning program focused on production line, floor, and baghouse cleaning. It did not
adequately address other flat surfaces such as I-beams, process ducts and pipes, roof trusses, and the top
of the blend rooms. Semi-annual cleanings (Section 4.4) during plant shutdowns were supposed to be
scheduled; however, CSB did not find evidence that these cleanings occurred. Housekeeping inspections
did not detect accumulations of combustible dust that could not be seen at floor level.
Good housekeeping is critical for combustible dust control. NFPA 654 (2000) states: “[R]egular
cleaning frequencies shall be established for floors and horizontal surfaces, such as ducts, pipes, hoods,
ledges, and beams, to minimize dust accumulations within operating areas of the facility.” It further
recommends that spaces inaccessible for cleaning be sealed to prevent dust accumulation and that
combustible dust inspection programs specifically address housekeeping. A more effective housekeeping
program at CTA would have limited the buildup of combustible dust.
8.5.3 Nonroutine Operations
The doors on the line 405 oven were left open because the oven was operating too hot. Personnel viewed
the temperature control problem exclusively as a product quality concern, so the safety hazard of
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