22-05-2014, 04:56 PM
Small Human Errors Cause Major Accidents Case History
Formosa-IL PVC Plant
The Formosa-IL PVC plant, bought from Borden Chemical, used 24 reactors to produce up to 400 million pounds of PVC resins per year. The reactor building housed the two PVC production areas – PVC1 and Paste. At the time of the incident, Formosa-IL employed 139 workers.
OPERATION
Six operators per shift worked in the PVC1 area where the incident occurred.
Two operators, a poly operator and a blaster operator, were responsible for the reactor involved in this incident.
The poly operator worked exclusively on the upper level of the building where the reactor controls and indicators were located,
The blaster operator worked on all levels.
POLY OPERATOR
To manufacture a batch of PVC, the poly operator readied the reactor,
Added the raw materials, and heated the reactor.
Monitored the reactor temperature and pressure until the batch was complete,
Then vented pressure from the reactor,
Told the blaster operator to transfer the batch to the stripper.
BLASTER OPERATOR
To transfer the batch to the stripper, on the lower level the blaster operator opened the transfer and reactor bottom valves. When the transfer was complete, the blaster operator closed the transfer valve, and the poly operator purged the reactor of hazardous gases to prepare the reactor for cleaning. The blaster operator cleaned the reactor by
opening the reactor manway,
power washing PVC residue from the reactor walls, and
Opening the reactor bottom valve and drain valve to empty cleaning water to floor drains.
Once the blaster operator finished cleaning the reactor, he closed the reactor bottom and drain valves, and gave the poly operator a completed checklist indicating that the reactor was ready for the next batch of PVC.
THE INCIDENT
The shift supervisor instructed operators to open vent valves on reactor D310 to relieve pressure and slow the release. At this point, he saw that the reactor pressure had already dropped to 10 psi, further indicating a large release.
Attempting again to go to the lower level, the shift supervisor descended an exterior stairway
Just then a series of explosions occurred.
The explosions knocked over two 3,000 gallon VCM recovery tanks; lifted multi-ton dryers off their supports; and destroyed the laboratory, safety, and engineering offices. The ensuing fire spread to the PVC warehouse west of the reactor building, burned for hours, and sent a plume of acrid smoke into the community.
Four operators were killed by the explosions: two working near the top of the reactor and two working on the lower level. A fifth operator died in the hospital two weeks later. The shift supervisor and two workers were hospitalized, and four workers were treated at the scene.
INCIDENT ANALYSIS
human error is a large contributor to fatalities, injuries, and property damage in the chemical industry
humanerror is both inevitable and unpredictable.
At Formosa-IL, several factors combined to make the human error in this incident more likely.
At Formosa-IL, the PVC1 reactors were arranged in groups of four, with a control panel for every two reactors. Both reactors (D306 and D310) involved in this incident occupied the same relative position among groups of four reactors(see figure)
Reactor bottom and drain valve control panels were on the lower level. Each reactor was labeled with the reactor number.
The control panels, also labeled with the reactor number, had clearly labeled indicator lamps showing the bottom and drain valve positions
Operators working on the lower level had no means to communicate with operators on the upper level who had ready access to reactor status information
an operator at the valve control panel on the lower level, who questioned why a bottom valve would not open, would have to climb the stairs to the upper level to determine reactor status.
This “inconvenience” may have contributed to a scenario in which the blaster operator might guess reactor status instead of climbing the stairs to get the status.
(operators at Formosa’s Baton Rouge, Delaware City, and Point Comfort plants either carry radios or have access to an intercom system on the lower level.)