Voiceover: November 27, 2019, the TPC Group Chemical Plant in Port Neches, Texas. A release of highly flammable butadiene caused a series of explosions that could be felt up to 30 miles away. The blast destroyed a portion of the TPC facility, damaged nearby homes and businesses and prompted a mandatory evacuation of residents living within four miles of the plant.
Several workers and members of the public reported injuries, and fires burned at the facility for over a month. Johnson: The incident at TPC was the result of a known hazard where popcorn polymer grew and formed inside equipment that was poorly managed and controlled at the facility. Gaps in industry good guidance on the management of popcorn polymer formation played a role.
The result was a catastrophic incident that disrupted life at the facility as well as the local community. Voiceover: TPC is a petrochemical manufacturing company with several facilities along the Gulf Coast of Texas and Louisiana. At the time of the incident, the company produced butadiene at its Port Neches plant.
Butadiene is used as a building block in the production of a wide range of products but is most commonly used to produce synthetic rubber. It is a highly reactive chemical which if not properly managed can lead to serious hazards. For instance in the presence of oxygen, high purity butadiene can undergo reactions to form a solid substance known as popcorn polymer.
If popcorn polymer accumulates and grows inside process equipment, it can lead to very high pressure and ultimately cause the equipment to rupture. On August 4, 2019, a worker performed a routine operation in TPC's butadiene unit. As part of that operation, the worker shut down a primary pump that was part of the butadiene production process.
When the worker tried to restart the pump, it would not operate. The primary pump was sent for repair and remained out of service from that date forward. A spare pump was used to continue operations.
The inoperable pump created a significant dead leg, which is an area of piping that is open to the process but does not have any material flowing through it. The CSB determined that over the next 114 days popcorn polymer began to form and accumulate within the dead leg. But the CSB could not find evidence that anyone at TPC recognized the hazard created by the dead leg.
At 12:54 a. m. on November 27, excessive popcorn polymer buildup caused the dead leg piping to suddenly rupture.
Approximately 6,000 gallons of liquid primarily composed of butadiene emptied through the ruptured piping in less than a minute. The liquid vaporized upon release to the atmosphere, forming a flammable cloud. Three nearby workers were startled by the rupture.
They immediately recognized the danger and quickly departed as the vapor cloud grew. In just two minutes, the flammable vapor cloud found an ignition source and exploded. The resulting pressure wave destroyed parts of the facility and injured two TPC employees and a security contractor.
The blast damaged nearby homes and buildings and was reportedly felt up to 30 miles away. Local officials stated five residents reported minor injuries. At least two additional explosions occurred following the initial blast.
Some of the piping damaged by those explosions could not be isolated. As a result, flammable process fluid continued to escape from ruptured equipment, nd smaller contained fires burned for more than a month. At 10:09 a.
m. on January 4, 2020, the TPC incident command confirmed that all fires were finally out. The chemical safety board launched an investigation into the incident at TPC and found four key safety issues contributed to the incident.
They are: dead leg identification and control; process hazard analysis action item implementation; control and prevention of popcorn polymer; and remotely operated emergency isolation valves. The first safety issue is dead leg identification and control. The TPC Port Neches facility had an operating procedure in place called Dead Legs in a High-Purity Butadiene Service that was intended to minimize the formation of popcorn polymer.
The procedure called for running spare pumps within the unit twice per month in order to circulate material through piping that was connected to the pumps and was otherwise out of service, forming a dead leg. The procedure did not, however, identify the potential for a dead leg to form if the primary pump was out of service for an extended amount of time, which is what happened in the months leading to the incident. Therefore the procedure did not specify ways to mitigate the hazard of popcorn polymer formation should the primary pump be offline.
And the CSB found that although repair of the primary pump was initially prioritized as urgent, it was soon changed to routine due to the existence of the spare pump. This led to a dead leg that existed for at least 114 days, allowing dangerous levels of popcorn polymer to form and grow. Griffin: Had TPC's procedure specifically identified the potential for a dead leg to form when the primary pump was offline, personnel may have taken action to prevent accumulation of popcorn polymer, such as prioritizing repair of the pump, purging the piping or adding popcorn polymer inhibitor to the dead leg.
Instead TPC appeared to consider the offline pump as a threat to maintaining unit operation, not as a threat to process safety. And the result was the destruction of the unit. Voiceover: In its final report, the CSB made a recommendation to TPC Group to develop and implement a process to identify and control or eliminate dead legs in high-purity butadiene service.
In addition the CSB identified gaps in industry guidance around the issue of dead legs in butadiene units. A guidance document developed by the American Chemistry Council called The Butadiene Product Stewardship Guidance Manual is designed to provide general information to companies that may handle or store butadiene. While the manual gives a general overview of popcorn polymer, it does not contain any information on the potential consequences of dead legs or how companies should identify, control or prevent dead legs.
The CSB believes that such additional guidance could have helped to prevent this incident and could help prevent similar incidents in the future. As a result, the CSB made a recommendation to the American Chemistry Council to revise its Butadiene Product Stewardship Guidance Manual to include guidance on identifying and controlling or eliminating dead legs in high-purity butadiene service. The second safety issue identified by the CSB is process hazard analysis action item implementation.
The CSB reviewed two process hazard analyses or PHA's that focused on TPC's butadiene process. In one of them, a PHA performed in 2016. The hazard of popcorn polymer accumulation causing low or no flow was identified.
The PHA team made a recommendation to TPC to assure that when equipment is out of service for maintenance, the lines are still flushed monthly. TPC management accepted this recommendation and assigned a due date for implementation in December 2016, almost three years before the incident. But the CSB found the recommendation was never implemented.
Griffin: Had TPC implemented the 2016 recommendation for personnel to regularly flush piping associated with out of service equipment, the dangerous buildup of popcorn polymer that led to this incident could have been prevented. Voiceover: The third safety issue is control and prevention of popcorn polymer. The CSB found that TPC did not take steps to effectively control or prevent the buildup of popcorn polymer despite a history of experiencing popcorn polymer formation at its facility.
For instance prior to the incident, in April 2019 TPC began a series of operational trials including removing a piece of equipment considered problematic from service. TPC also reduced the amount of popcorn polymer inhibitor that was injected into the production stream and used new injection equipment. Soon after the trials commenced, TPC experienced increased popcorn polymer formation within the process.
Evidence of popcorn polymer formation was noticed by TPC employees as early as May and June. But in the meantime, TPC continued operating its butadiene unit and did not halt the trials that may have contributed to the problem. And the facility continued to experience popcorn polymer and equipment plugging in the butadiene process, which led to serious operational problems within the butadiene unit.
After the extensive popcorn polymer plugging, TPC employees considered shutting down the unit for an unscheduled mini outage to clean up the polymer and make necessary modifications and improvements and bring the unit up to best practice standards. But after clearing several popcorn polymer blockages, TPC ultimately decided to delay this shutdown until 2020 when it was too late. Griffin: Popcorn polymer excursions are highly hazardous events.
If there are any process vulnerabilities like unknown dead legs, popcorn polymer can cause equipment ruptures, leading to explosions and fires. Butadiene facilities should develop robust policies aimed at preventing and controlling popcorn polymer. Facilities should also develop policies to shut down units and investigate popcorn polymer formation when it is observed.
Had TPC had such policies in place, this incident could've been avoided. Voiceover: The CSB also found an additional gap in the ACC's Butadiene Product Stewardship Guidance Manual. The manual did not specify conditions that could justify shutting down and cleaning a butadiene unit.
As a result, the CSB recommended that the American Chemistry Council revise the manual to provide guidance to help companies identify what should be considered excessive or dangerous amounts of popcorn polymer in a unit, and provide mitigation strategies that operators should take when dangerous amounts of popcorn polymer are identified to control or eliminate the hazard. Finally the fourth safety issue identified by the CSB is remotely operated emergency isolation valves. At TPC the butadiene process was not adequately equipped with remotely operated emergency isolation valves designed to stop process releases remotely from a safe location.
Had the butadiene process been equipped with remotely operated emergency isolation valves, it is possible that the process speed upstream of the release could have been stopped shortly after the release began, minimizing the size of the initial vapor cloud and explosion. Additionally any secondary releases caused by the first explosion could have been stopped early in the incident. That step could have prevented some of the subsequent explosions and fires, minimizing the damage caused by the incident.
Instead the unit was primarily equipped with manual and locally controlled emergency block valves, and these could not be safely accessed during the incident, meaning equipment could not be isolated. As a result, severe explosions caused one process tower to propel through the air and land within the facility and other process towers to fall within the unit. Fires burned for more than a month and led to the ultimate destruction of the unit.
Griffin: Manual and locally controlled valves are not reliable in a catastrophic incident since often these valves cannot be safely accessed. Companies that handle large amounts of flammable or toxic material should furnish equipment with remotely operated emergency isolation valves so that potential releases can be stopped from a safe location. Johnson: We believe our final report and recommendations will help facilities that handle and store large quantities of butadiene better control popcorn polymer within their processes.
Doing so can prevent another terrible incident like the one that occurred at TPC. Thank you for watching this CSB safety video. Voiceover: For more information, please visit CSB.
gov.
