On December 19, 2007. an exothermic reaction at T2 Laboratories, a Jacksonville, Florida-based chemical manufacturer, led to a runaway condition resulting in a massive explosion that killed four workers, injured 32 others and destroyed neighboring businesses.
That day, the workers were mixing a batch of methylcyclopentadienyl manganese tricarbonyl (MCMT), also known as the gasoline additive Ecotane. Although they had mixed and processed batches of Ecotane at least 100 times before (they started in 2004), they had persistently ignored some early warning signs that foretold the very real possibility of catastrophic failure. On the day of the disaster, a fire started and, within 10 short minutes, the process condition accelerated from a familiar problem they had faced before to a full-fledged disaster. The result was an explosion so powerful that a one-ton chunk of the steel reactor was flung into another building 400 feet away.
A core element when implementing high plant safety standards is to closely analyze key processes so that imminent threats to safety can be identified and neutralized. An analysis of this infamous T2 Laboratories incident helps to reveal where mistakes were made and is helpful for safety engineers who a dealing with safety challenges at their own sites on an ongoing basis.
Let’s analyze the T2 Laboratories timeline on the day of the disaster:
At 7:30 a.m. the day shift process operator began manufacturing “Batch 175” of the Ecotane from the control room adjacent to the process line. He engaged the automated process control system to load the reactor with the raw materials. An outside operator hand-loaded the reactor with blocks of sodium metal, and then sealed the reactor.
At 11 a.m., the process operator began heating the batch to melt the sodium and initiate the chemical reaction, while monitoring the temperature and pressure on the process control screen. Once the sodium melted, at 210°F, the process operator started the mixing process. In the process of mixing, as usual, the reaction created more heat. That heat continued rising in the reactor. At a temperature of 300°F, the process operator turned off the heating system as specified in the procedure, but as the mixture was exothermic, heat from the reaction continued to rise.
At a temperature of 360°F, the process operator initiated the cooling process. However, the cooling process never started. The control system cooling program called for water to inject into a jacket surrounding the reactor, but a malfunction occurred and the water never made it to the jacket.
At 1:23 p.m., the plant operator reported the cooling problem to the owners and asked them to return to the site. Upon their return, one of the two owners went to the control room to assist. Fearing a fire, the owner rushed outside to tell workers near the reactor to evacuate as a precaution. The owner then went back into the control room.
At 1:33 p.m., the reactor burst and its contents exploded, killing the owner and the process operator who were in the control room and two outside operators who were exiting the reactor area.
According to the Chemical Safety Board (CSB) investigation, T2 Laboratories’ runaway exothermic reaction occurred during the first step of the MCMT mixing process. A loss of sufficient cooling likely resulted in the runaway reaction, leading to an uncontrollable pressure and temperature rise in the reactor. The pressure burst the reactor; the reactor’s contents ignited, creating an explosion equivalent to 1,400 pounds of TNT.
In hindsight, it might be easy to question why more water wasn’t added into the cooling system so that the rising pressure could be relieved earlier. While the answer to that question may appear simple now, in the heat of the moment, the disaster was caused by a lack of knowledge on the part of staff of the ongoing safety threats.
At the time of the incident, no emergency instructions existed for addressing a loss of cooling situation. Standard procedures directed operators to fully open the water supply valve and the manual bypass valve in order to cool the reactor. A secondary (backup) source of water stored on site was not immediately available to the process operator in an emergency.
So, what was the root cause of the blast? T2 did not recognize the runaway reaction hazard associated with the MCMT it was producing. The chemical maker’s cooling system was susceptible to a single point of failure due to a lack of design redundancy. In addition, the company did not have the pressure relief capacity in place to safely vent an uncontrolled reaction. Chemists and chemical engineers involved in developing and operating the T2 MCMT process were also unaware of the need to perform runaway reaction testing, address emergency relief, and identify and evaluate previous process anomalies.
The unexpected exothermic reactions were managed, on the fly, as they occurred, and the T2 employees were under the mistaken impression that the owner and chemical engineer could control any incidents.
This combination of lax safety standards, incomplete communication, human error and mechanical error can happen within any organization at any time. Preventing such events in the future depends on analyzing an existing process with an eye on safety gaps. In the case of T2 Laboratories, if the possibility of a runaway reaction were modeled or analyzed, a conclusion would have been drawn for deploying a more comprehensive pressure release system and redundant cooling system.
A complete a hazard and operability study (HAZOP), could also have helped in identifying the need for testing to determine the thermodynamic and kinetic nature of the reaction.
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