CSB Issues Final Synthron Explosion Report, Releases Accident Video Simulation

In a final report released today on last year's fatal explosion at the Synthron chemical manufacturing facility in Morganton, N.C., the U.S. Chemical Safety Board (CSB) concluded that the company's management of reactive chemical hazards was inadequate and that the facility was unprepared for a chemical process emergency. CSB also found that ineffective corporate oversight by French parent company Protex International contributed to the likelihood and severity of the accident.

The explosion occurred on Jan. 31, 2006, as the result of a runaway chemical reaction in a 1500-gallon process vessel inside the Synthron production building. One worker was fatally burned and fourteen others were injured, two seriously. The blast destroyed the facility and broke windows up to one-third of a mile away. Two churches and a home were damaged and were later condemned. Synthron filed for bankruptcy following the accident and the facility has not been rebuilt.

A two-minute computer-animated video depicting the sequence of events that led to the Synthron explosion has been released, it is also part of a new 20-minute CSB safety video on reactive chemical hazards, titled "Reactive Hazards: Dangers of Uncontrolled Chemical Reactions," which was also released today in an effort to draw increased attention to the dangers from uncontrolled chemical reactions.

"The accident at Synthron emphasizes the need for effective corporate oversight, emergency planning, and reactive chemical process training and safeguards," said John S. Bresland, CSB member. "If these measures had been in place, this accident could have been prevented."

Synthron manufactured acrylic polymers for use as paint and coating additives, which were typically produced inside a batch reactor by chemically reacting a blend of acrylic monomers in a mixture of flammable solvents.

The accident occurred when plant managers attempted to fulfill an order for acrylic polymer that exceeded the normal batch size for this product. Instead of making two smaller batches to fill the order, managers decided to make a single, larger batch. Managers decided to add all the extra acrylic monomer during the first stage of the reaction process, which was a critical mistake according to subsequent laboratory testing by the CSB that showed increasing the batch size in this manner raised the maximum heat output from the reaction by a factor of at least 2.3. The heat output exceeded the cooling capacity of the condenser and the reaction accelerated out of control or "ran away."

CSB said that after initiating the reaction on Jan. 31, 2006, operators observed solvent vapor leaking from a hatchway on top of the reactor as the process overheated and pressure built up inside the reactor. Operators fled the production building and gathered just outside a doorway. A flammable vapor cloud formed inside the building, and a short time later it ignited and exploded, destroying the production facility and fatally burning a maintenance supervisor who had remained inside. Personnel who gathered just outside the building were among the injured.

"Synthron had apparently never documented the actual capacity of the cooling equipment, which was essential to keeping reactions from running out of control," said CSB Lead Investigator Jim Lay. "The CSB found no evidence that the company had ever cleaned or inspected the cooling water side of the condenser on the reactor for 30 years." CSB later found that this surface was fouled with scale, rust, and sediment which likely degraded the cooling capability of the condenser by at least 25 percent.

It's estimated that the flammable release occurred when the reactor reached a pressure of 23 pounds per square inch gauge (psig), which was well below the reactor's maximum working pressure of 75 psig, but Synthron had a longstanding practice of improperly securing the reactor hatch, CSB said, using only four of the 18 metal clamps recommended by the manufacturer. The failure to fully clamp down the hatchway compromised the performance of the hatchway gasket, which allowed flammable solvent vapors to be released into the building.

Among the findings, CSB's investigation determined that Synthron had gathered only minimal safety information on its polymer-producing processes, and personnel, including the managers, were poorly prepared to recognize the dangers from an uncontrolled chemical reaction. Also, it found that Synthron had not performed a systematic safety review of the reactor, also known as a process hazard analysis, and failed to install safeguards to automatically detect, prevent, or mitigate a runaway reaction.

CSB also concluded that Synthron was not prepared for an emergency. Operating procedures did not instruct employees on what to do in the event of a chemical release or loss of chemical reactor control. Evacuation drills had not been conducted and the facility was not equipped with an emergency alarm system. Investigators concluded there was adequate time available to have evacuated all personnel to a safe location after vapor escaped from the reactor hatchway, and that such an evacuation would likely have prevented the death and injuries.

Synthron LLC was owned by a French company, Protex International, which has operations in Europe, Asia, North America, and South America. Protex has chemical facilities in Massachusetts, New Jersey, and Florida. The investigation found that Protex had testing equipment at its European facilities to measure chemical reaction hazards, but did not use this equipment to determine the safety of Synthron's processes or provide adequate technical support to Synthron.

CSB recommended that Protex International establish a program to follow good industry safety practices for managing reactive hazards at all its remaining U.S. facilities.

For more information or to view the computer animation video, visit www.csb.gov/index.cfm?folder=current_investigations.

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