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Packaging Corporation of America Hot Work Explosion

Overview

On February 8, 2017, three contractors were fatally injured and seven contractors sustained injuries in an explosion at the Packaging Corporation of America facility in DeRidder, Louisiana. The CSB final report identified the event as a non-condensable gas system explosion at the PCA DeRidder paper mill involving a foul condensate tank that contained a flammable atmosphere.

Incident Snapshot

Field Value
Facility / Company Packaging Corporation of America (PCA)
Location DeRidder, LA
Incident Date 02/08/2017
Investigation Status The CSB's final investigation report was released on April 24, 2018.
Accident Type Hot Work - Explosion and Fire
Final Report Release Date 04/24/2018

What Happened

  • On Wednesday, February 8, 2017, at approximately 11:05 am, a foul condensate tank, part of a non-condensable gas system, exploded at the Packaging Corporation of America (PCA) containerboard mill in DeRidder, Louisiana.
  • At the time of the incident, the mill was undergoing its annual planned maintenance outage, also referred to as a shutdown.
  • Air likely entered the foul condensate tank through a vacuum relief device on the tank’s roof.
  • During typical operation, automatic controls continually cycled the liquid level inside the tank, creating routine periods of low pressure.
  • These low-pressure conditions were relieved by the vacuum relief device, which pulled air into the tank.
  • During the annual outage, air also likely entered the tank as its contents cooled.
  • On the day of the incident, contractors supporting the annual outage work made repairs by welding on water piping above and de-coupled (disconnected) from the foul condensate tank.
  • The CSB determined that air entered the foul condensate tank and mixed with the tank’s flammable turpentine vapor.
  • This created an explosive atmosphere within the tank.
  • Ongoing hot work repairs above the tank likely ignited this vapor and caused the explosion.

Facility and Process Context

  • The PCA DeRidder mill is an integrated containerboard mill that brings wood onsite, chips and pulps the raw materials, and makes containerboard paper.
  • The DeRidder mill was built in 1969.
  • In October 2013, PCA acquired Boise Inc., the former owner and operator of the DeRidder mill.
  • The DeRidder mill consists of a pulp mill area and a paper mill area.
  • The pulp mill is composed of various smaller processing areas, including the Powerhouse and the Pulp mill.
  • The foul condensate tank has a capacity of approximately 100,000 gallons.
  • At normal operating conditions, PCA keeps the foul condensate tank at approximately 185 degrees Fahrenheit and at or near atmospheric pressure.
  • The foul condensate tank is designed for 8-inches of water pressure and 10-inches of water vacuum.
  • The foul condensate tank was not insulated.
  • The bottom 10-feet of tank and the area near the ladder were coated to reduce heat transfer and to protect personnel from the hot surface.
  • The foul condensate tank provides a means to regulate flow fluctuations between the upstream turpentine-stripping column and a downstream foul condensate-stripping column.
  • The foul condensate tank is part of the process equipment that recovers turpentine and water from the pulping process.
  • The CNCG system operates at a slight vacuum to collect NCG and direct them to power boilers for destruction and energy recovery.
  • Clean condensate piping (water piping) also connects to the foul condensate tank.
  • The mill uses this water piping to periodically clean the inside of the tank so that workers can enter the foul condensate tank to perform inspection or maintenance.
  • The DeRidder mill did not clearly define tank responsibility and neither the pulp mill personnel nor the powerhouse personnel appeared to know which operations area was responsible for operating and maintaining the foul condensate tank.

Consequences

  • Fatalities: 3
  • Injuries: 7
  • Environmental Release: Not stated in the source extract.
  • Facility Damage: The explosion heavily damaged the surrounding process. The explosion damaged the pipe rack structure, its associated piping located above the tank, a work platform at the top of a powerhouse stack, and ductwork attached to the precipitator in the powerhouse area. Other areas of the mill also sustained damage. The foul condensate tank traveled approximately 375 feet and over a six-story building before landing on process equipment.
  • Operational Impact: The mill was undergoing its annual planned maintenance outage. The annual outage began on February 5 and was scheduled to end on February 12. The emergency response plan in place at the DeRidder mill was not properly implemented across the entire facility. OSHA issued citations to PCA for those violations.

Key Findings

Immediate Causes

  • Air entered the foul condensate tank and mixed with the tank’s flammable turpentine vapor.
  • This created an explosive atmosphere within the tank.
  • Ongoing hot work repairs above the tank likely ignited this vapor and caused the explosion.

Contributing Factors

  • Air likely entered the foul condensate tank through a vacuum relief device on the tank’s roof.
  • During typical operation, automatic controls continually cycled the liquid level inside the tank, creating routine periods of low pressure.
  • During the annual outage, air also likely entered the tank as its contents cooled.
  • These sources of air ingress allowed air to mix with turpentine vapor and thereby form an explosive mixture in the tank’s vapor space.
  • The foul condensate tank likely contained water, a layer of flammable liquid turpentine on top of the water, and an explosive vapor space containing air and flammable turpentine vapor.
  • The tank was left with a liquid level because improvements made in the process eliminated the need to de-inventory the tank for the annual outage, there were no known risks among mill personnel of leaving liquid in the tank, the company did not have plans to work directly on the tank during the outage, and there were resource limitations as mill staff had numerous other tasks to complete during the annual outage.
  • The planned repair required welding.
  • The permit focused on the water piping, pipe bridge, and surrounding platform, however, the permit did not consider the potential hazards within adjacent vessels or piping, such as inside the foul condensate tank.
  • PCA workers found the platform around the welding site to be free of flammable vapors; however, no one checked the inside of the foul condensate tank for a flammable atmosphere.
  • Continuous combustible gas monitoring provided a weak safeguard against the February 8 incident.
  • The foul condensate tank sat within 35 feet of the hot work, and the exterior of the tank served as the primary barrier between the flammable atmosphere and the hot work.
  • The tank could have leaked or the tank exterior could have provided for heat conduction had a source of ignition come into contact with the tank.
  • The foul condensate tank may have intermittently vented NCG via the tank’s pressure vacuum breaker or the valve on the three-inch water piping.
  • The foul condensate tank likely contained a larger than anticipated quantity of turpentine because the weir within the tank had not been operational for approximately three months.
  • Because this valve remained closed, turpentine collection in the foul condensate tank was not controlled, and PCA removed the turpentine only when the tank was periodically emptied.
  • During the 12 hours of operation captured in Figure 26, process data indicate that the pressure vacuum breaker opened enough for air to enter the foul condensate tank at least 14 times.
  • As the tank level decreased from 20 to 16 feet, the internal pressure decreased, pulling as much as 1,800 cubic feet of air through the vacuum breaker and NCG from the CNCG piping into the foul condensate tank.
  • As the temperature within the foul condensate tank cooled, some internal vapor likely condensed to liquid, which lowered the pressure inside the tank.
  • Air pulled into the foul condensate tank during cooling likely provided additional oxygen to support an explosive atmosphere of NCG and turpentine vapor inside the foul condensate tank.

Organizational and Systemic Factors

  • PCA did not perform a hazard analysis on key components of the CNCG system, including the foul condensate tank, to identify, evaluate, and control process hazards.
  • PCA did not identify with sufficient clarity those operations personnel who were responsible for the foul condensate tank, leading to confusion within the mill workforce.
  • PCA did not observe established industry safety standards and good practice safety guidance.
  • PCA did not adequately demonstrate a learning culture with respect to making needed improvements based on lessons learned from past publicized and well-understood industry incidents.
  • PCA did not conduct a hazard analysis of the foul condensate tank.
  • PCA did not effectively assign or communicate clear ownership of the tank to any operations group.
  • PCA did not install instrumentation on the tank that was capable of detecting when the vapor inside the tank entered an explosive range.
  • PCA lacked knowledge of both the turpentine accumulation and the air ingress within the tank.
  • PCA did not apply its process safety management system to the CNCG system.
  • PCA did not apply the ISA-84 safety standard to the foul condensate tank or the CNCG header system.
  • PCA did not clearly define tank responsibility and neither the pulp mill personnel nor the powerhouse personnel appeared to know which operations area was responsible for operating and maintaining the foul condensate tank.
  • PCA did not adequately review and communicate potential hazards, and DeRidder employees did not understand that the tank routinely pulled in air during the automatic cycling of the level.
  • PCA did not understand that allowing the foul condensate tank to cool could create enough of a vacuum to draw air into the tank through the vacuum breaker.
  • PCA did not apply PSM to the foul condensate tank despite the fact that the foul condensate tank contained some quantity of turpentine and that the tank was directly connected to the turpentine system.
  • By applying these strict PSM boundaries, a formal hazard analysis was not required and was therefore not performed, and additional effective safeguards were never considered.

Failed Safeguards or Barrier Breakdowns

  • pressure vacuum breaker
  • rupture disks
  • flame arrestors
  • water seals
  • hot work permit program
  • combustible gas monitoring of the tank vapor space
  • barriers or covers
  • fire blanket
  • process hazard analysis
  • instrumentation on the tank that was capable of detecting when the vapor inside the tank entered an explosive range
  • safety interlock
  • oxygen analyzers
  • NFPA 69
  • ISA-84
  • NFPA 68
  • weak roof-to-shell attachment (frangible roof)
  • draining, purging, and inerting the foul condensate tank
  • positive isolation device, such as a blind flange
  • continuous water flow to the foul condensate tank’s overflow water seal
  • sight glass or instrumentation to monitor the seal liquid level

Recommendations

  1. 2001-05-I-DE-R1 | Recipient: OSHA | Status: reiterated | Summary: Amend its Process Safety Management (PSM) Standard, 29 C.F.R. § 1910.119, to ensure coverage under the standard of atmospheric storage tanks that could be involved in a potential catastrophic release as a result of being interconnected to a covered process with 10,000 pounds of a flammable substance.
  2. 2017-03-I-LA-R1 | Recipient: Packaging Corporation of America (PCA) | Status: Closed – Acceptable Action | Summary: Apply the CSB safety guidance to PCA pulp and paper mills that produce NCG [Non-Condensable Gas] and operate NCG systems, which includes all foul condensate tanks. For these NCG systems: Apply effective process safety management elements using good practice guidance, such as CCPS Guidelines for Risk Based Process Safety, and Guidelines for Implementing Process Safety Management; Consider further expanding process safety management program boundaries beyond the minimum legal requirements to provide heightened coverage of process safety hazards; Apply NFPA 69, Standard on Explosion Prevention Systems, to provide effective explosion prevention; Where explosions cannot be prevented in accordance with NFPA 69, apply NFPA 68, Standard on Explosion Protection by Deflagration Venting, to provide explosion protection; Ensure safety instrumented systems (safety interlocks) achieve desired risk reduction by applying the life-cycle approach provided in ISA-84, Functional Safety: Safety Instrumented Systems for the Process Industry Sector; Apply TIP 0416-09, Collection and burning of concentrated noncondensible gases: regulations, design and operation, for effective NCG system design and operation; Provide workers with periodic training to ensure they have an understanding of all process safety hazards applicable to areas of their responsibility and job tasks, including the safety conditions needed to permit hot work
  3. Packaging Corporation of America | Recipient: Packaging Corporation of America | Status: new | Summary: Apply the CSB safety guidance to PCA pulp and paper mills that produce NCG and operate NCG systems, which includes all foul condensate tanks.
  4. Not stated | Recipient: Not stated | Status: Not stated | Summary: Ensure safety instrumented systems (safety interlocks) achieve desired risk reduction by applying the life-cycle approach provided in ISA-84, Functional Safety: Safety Instrumented Systems for the Process Industry Sector;
  5. Not stated | Recipient: Not stated | Status: Not stated | Summary: Apply TIP 0416-09, Collection and burning of concentrated non-condensible gases: regulations, design and operation, for effective NCG system design and operation;
  6. Not stated | Recipient: Not stated | Status: Not stated | Summary: Provide workers with periodic training to ensure they have an understanding of all process safety hazards applicable to areas of their responsibility and job tasks, including the safety conditions needed to permit hot work.

Key Engineering Lessons

  • CNCG systems must be designed and operated to prevent ingress of air because air can create a potentially explosive mixture with flammable vapors.
  • Hot work permits must consider hazards in adjacent vessels and connected process equipment, not only the immediate work area.
  • A tank connected to a flammable process stream can require hazard analysis and safeguards even if it is not the direct target of maintenance work.
  • Instrumentation or other safeguards capable of detecting an explosive atmosphere in the tank vapor space were identified as missing and should be considered for similar systems.
  • Process safety boundaries that exclude interconnected atmospheric storage tanks can leave significant hazards unanalyzed and unprotected.

Source Notes

  • Priority 1 final report used to resolve conflicts and populate the authoritative incident record.
  • Priority 3 recommendation status summary used only for recommendation status updates and corroborating wording where consistent with the final report.
  • All fields contain only information explicitly stated in the provided source extracts.

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