Uncovered Hazards: Explosion at the DeRidder Pulp and Paper Mill

Summary

On February 8, 2017, a catastrophic explosion at PCA's DeRidder, Louisiana, mill killed three and injured seven. The CSB investigation revealed PCA's failure to apply its process safety management system to the tank that exploded, overlooking the potential for a flammable atmosphere. Despite industry recommendations, PCA did not conduct a Process Hazard Analysis, which could have prevented the tragedy. The CSB urged OSHA to revise the PSM standard to include atmospheric storage tanks and provided safety guidance to prevent future incidents.

Takeaways

• 🚨 On February 8, 2017, a catastrophic explosion at PCA's DeRidder mill resulted in three fatalities and seven injuries due to a failure to apply process safety management to a tank containing flammable vapors.
• 🔍 The Chemical Safety Board (CSB) investigation found that PCA did not apply its process safety management system to the tank, leading to inadequate hazard evaluation and control.
• ⚠️ Despite industry guidance, PCA overlooked the potential for a flammable atmosphere to form within the tank, which was a critical oversight.
• 🔧 The explosion was triggered during a maintenance shutdown when welding on piping above the tank likely ignited the flammable vapors inside.
• 🛠️ Hot work was performed without recognizing the tank's hazardous contents, highlighting a lack of proper risk assessment.
• 💧 The tank, which should have been drained and purged, was left with residual turpentine that contributed to the explosion.
• 📝 There was confusion over operational responsibility for the tank, leading to a failure to remove flammable substances and maintain safety.
• 🔄 The vacuum relief valve, intended to prevent tank damage from low pressure, inadvertently allowed air into the tank, creating an explosive mixture.
• 🛑 The CSB emphasized the need for a robust safety management system, especially for processes involving non-condensible gases, which was not followed by PCA.
• 👷‍♂️ Workers were not adequately trained or informed about the hazards associated with the tank, increasing the risk of such incidents.
• 📚 The CSB's final report provided safety guidance for pulp and paper mills, urging the application of effective process safety management systems and training to prevent future tragedies.

Q & A

What event occurred at the Packaging Corporation of America's DeRidder, Louisiana, Pulp and Paper Mill on February 8, 2017?

A tank violently exploded during a planned maintenance shutdown, killing three contract workers and injuring seven others.

What was the primary finding of the Chemical Safety Board's investigation into the explosion?

PCA did not apply its process safety management system to the process that included the tank that ultimately exploded, leading to inadequate evaluation of hazards such as the potential for a flammable atmosphere to form within the tank.

What is the purpose of the foul condensate tank in the pulp production process?

The foul condensate tank is used to store foul condensate, a liquid containing mostly water, residual sulfur compounds, and turpentine, at or close to atmospheric pressure. It regulates the flow of liquid between the turpentine stripping column and a downstream unit that removes remaining sulfur components.

Why was the welding work (hot work) being performed on the piping above the foul condensate tank?

The water piping above and connected to the foul condensate tank had shifted and cracked months earlier, requiring repair.

What incorrect assumptions did the company make before the hot work began, which could have contributed to the explosion?

The company assumed that the tank contained mostly water, was sealed off from the atmosphere, and did not pose a safety risk.

Why was there a flammable atmosphere inside the foul condensate tank during the annual shutdown?

Residual turpentine, which is flammable, collected on top of the liquid in the tank, and the tank was not properly vented or monitored to prevent the buildup of a flammable atmosphere.

What actions could have been taken to prevent the explosion, as suggested by the CSB's investigation?

A properly conducted Process Hazard Analysis (PHA) could have identified the need to drain, flush, and leave the foul condensate tank open, as well as implement other safeguards such as low pressure alarms, oxygen analyzers, and interlocks to prevent a flammable atmosphere from forming.

What was the role of the vacuum relief valve in the incident?

The vacuum relief valve likely opened to add air into the tank due to low pressure conditions, which could have created an explosive atmosphere by introducing enough oxygen into the tank.

What recommendation did the CSB make to OSHA regarding the Process Safety Management (PSM) standard after the incident?

The CSB recommended that OSHA revise the PSM standard to cover atmospheric storage tanks that could be involved in a potential catastrophic release due to being interconnected with a covered process containing 10,000 pounds of a flammable substance.

What was the role of the United Steelworkers union in the aftermath of the explosion?

The United Steelworkers union, representing PCA employees, advocated for better training and education for workers regarding the hazards and the importance of process safety management in preventing such incidents.

What safety guidance did the CSB provide to pulp and paper mills in its final report?

The CSB provided guidance to apply effective process safety management systems to non-condensible gas systems, consider expanding PSM program boundaries, apply industry standards for explosion prevention and safety interlock systems, and provide workers with periodic training to understand process safety hazards.