(198f) Importance of Properly Designing Dust Explosion Protection Systems: Case Study:  2014 Georgia Pacific Corrigan Facility Fire and Explosion

When designing handling and conveying equipment for combustible dusts, it is crucial to properly implement protective measures (e.g., deflagration venting, suppression, and isolation) capable of mitigating the potential consequences in the event the dust is ignited. Generally speaking, dust processing, storage, and collection equipment, such as cyclones, mills, baghouses, dryers, and silos are typically connected via pipes, pneumatic conveyors, and dust extraction or aspiration lines. If a fire or dust explosion occurs in one vessel, the flame front or pressure can quickly propagate through these conduits to other parts of the plant and potentially escalate to even worse consequences than the original event. More specifically, pressure piling or flame jet ignition in the connected vessels can result in a series of more catastrophic secondary events. To effectively prevent and mitigate this phenomenon, suppression or deflagration venting is used in the source vessel, and explosion isolation is used to prevent the explosion or fire from propagating to neighboring vessels in order to protect adjacent parts of the plant. Improper design of isolation devices can be costly, and the present paper will illustrate this by presenting a case study on the fire and explosion that occurred in 2014 at the Georgia Pacific Corrigan plywood facility.

On April 26, 2014, a fire that originated at a plywood sander eventually propagated through the pneumatic dust conveying system and resulted in an explosion in the baghouse (dust collector), fatally injuring two employees, and seriously injuring others who were responding to the incident. Sparks from the sander entered the extraction pipe, which was protected by an active suppression/isolation system (spark-sprinkler-abort gate) upstream of the baghouse. When the fire in the extraction pipe was discovered, the extraction blower downstream the baghouse (negative pressure system) was turned off and allowed smoldering and burning to continue within the pipe. The blower was subsequently turned back on, at which time a flame front developed that propagated into the baghouse which was not properly isolated. This incident occurred because of the improper design of a back-blast damper as an isolation device and operational errors associated with the blower being turned off and back on prior to extinguishing the burning material. This paper will analyze the root cause of the incident as well as key lessons learned related to: system design; performing a dust hazard analysis; required air stream flow rates; proper back blast designs; impeding deflagration vents; and exclusion zones in the path of a vented deflagration in the baghouse.