Process safety incidents rarely have conventional "happy endings," but the U.S. Chemical Safety and Hazard Investigation Board reports that a chemical release at MGPI Processing Inc. on Oct. 21, 2016, resulted in the company initiating corrective action that went beyond CSB's recommendations, earning it formal recognition from the organization. MGPI produces distilled spirits, specialty wheat proteins and starches.
The release occurred at MGPI's plant in Atchison, Kan., when a truck delivering sulfuric acid from Harcros Chemicals Inc. was inadvertently connected to a tank containing incompatible sodium hypochlorite. The plume of chlorine and other compounds caused by the resulting chemical reaction led to a shelter-in-place order for thousands of local residents and at least 120 employees and members of the public seeking medical attention.
CSB issued five safety recommendations, including two to MGPI, two to Harcros, and one to Atchison County's emergency management department. Of the four that were eventually accepted and closed, two exceeded CSB's recommended requirements. The county is working on closing the remaining recommendation.
Especially because the release directly impacted its community, MGPI took the incident very seriously and began implementing changes before CSB released its report. These included:
Retained a third-party engineering firm to independently evaluate the plant's Mod B facility building and ventilation system;
Relocated and rerouted the HVAC air intake for the control room away from the chemical tank yard;
Moved the Mod B motor control center (MCC) room intake and the outlet fan for the make-up air;
Installed actuated dampers in the control room inlet ductwork as well as the inlets to the reactor room and MCC room, which serve as a physical barrier to air contaminants;
Installed new emergency shutdown device (ESD) buttons at the chemical unloading pad, control room, and outside the egress of the Mod B control room;
Tied all ESB buttons to the ventilation damper system;
Implemented an interlock system tied into air contaminant sensors and alarms that trigger engineering controls when activated;
Upgraded chemical unloading and transfer equipment with chemical portal separation, signage, unique locks and fittings, and implemented an innovative key control and chemical unloading sequence;
Upgraded monitoring and detection equipment to decrease risk of chemical releases, including pump and valve interlocks and automatic engagement of the deluge system;
Extended and upgraded the deluge system to cover the propylene oxide day tank and all sides of the truck and trailer during unloading;
Added an egress to the Mod B control room, installed more emergency supplied air packs along the egress path, and improved movement in the control room by moving the center control console from the middle of the room to its walls;
Established inspection, testing and documentation requirements, and applicable standards for pressure vessels, piping, storage tanks, pressure-relieving devices, pumps, and control systems; and
Remove the plant's acetic anhydride process.
Further details of MGPI's remediation efforts are at www.csb.gov/assets/recommendation/status_change_summary_mgpi_(mgpi_r1)_c-aa_.pdf and at www.csb.gov/assets/recommendation/status_change_summary_mgpi_(mgpi_r2)_c-era.pdf