How many hours can operators stay at the plant before their effectiveness begins to deteriorate? Bayer found out.
One element that figured prominently in the 2008 explosion at the Bayer Crop Science facility in Institute, West Virginia, was a lack of operator training for the new DCS that had just been installed at the methomyl production unit. While this was undoubtedly a major contributor, it underestimates the extent of the personnel issues within the plant. There were equipment problems to be sure, however the steps leading up to the explosion were more the result of bad decisions from operators.
Some of the problems related to training, but operators were also reaching their breaking point due to overwork and stress. Larvin insecticide is a seasonal product so there are limited times during which it sells. Methomyl is necessary for its manufacture, and available inventory was running out. The upstream process feeding to the methomyl unit was starting and would soon be sending feedstock, so Bayer put on pressure to get the unit restarted, driving its people to get the work done. This led to major increases in the workload on the staff. Investigations after the incident showed that many operators and other people were working 60 to 70 hours per week prior to the startup. Some ended up working 18-hour shifts for days at a time, disrupting normal sleep cycles and leading to high fatigue levels.
Asleep at the board
These kinds of disruptions can impair decision-making, reaction times, and communication. Operators struggling with their own fatigue while they’re trying to understand an unfamiliar control system driving a complex chemical process are bound to make mistakes. A labor-intensive process like a unit startup under these conditions is a recipe for disaster.
In this particular case, communication between operators on different shifts began to break down, which also allowed problems to escalate. Operators were supposed to maintain an activity log using an electronic notepad that would explain what had been going on during the previous shift with instructions for the next shift. Operators were also supposed to have a brief discussion of the general situation during the handoff. Unfortunately, as the unit restarted, these did not happen as they should have.
Dangers of shift changes
In the 48 hours leading up to the incident, there were several critical handoff mistakes:
• The day before, when the night shift came on duty, the operators were unaware that the solvent run and residue treater refill, as specified in the procedure, had not been done. This omission was not noted in the log, nor was it discussed verbally.
• The night shift did not tell the day shift the next morning that they had started pumping flasher bottoms (methomyl-contaminated solvent) into the empty residue treater vessel.
• The next day shift operator did not tell the next night shift operator that the flasher bottoms in the vessel had excessively high methomyl concentrations.
And so it went until the conditions were right for the runaway reaction to take off and the tank exploded. More experienced operators might have realized what was happening and understood the potential consequences for some of the steps that had been overlooked. However the technical support staff had been reduced through various reorganizations. There was only one technical advisor who had to oversee multiple units, and he worked on the day shift. During the startup, Bayer brought in a second adviser to help carry the extra workload, but he was not familiar with the methomyl process.
Investigations after the incident showed that the operators simply didn’t understand what was happening in the process. Synthesis of methomyl is complex, and some of the decisions operators made indicated they did not have a grasp of what was going on in the various steps. At one point, they concluded incorrectly that methomyl was not forming properly, when in fact it was. Their resulting assumption was that the flasher bottoms had little or no methomyl content when lab tests showed that it was, in reality, excessively high. This information did not get to the right people with fatal results.