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First Chemical Corp. Reactive Chemical Explosion

Overview

On October 13, 2002, a violent explosion occurred in a mononitrotoluene (MNT) distillation tower at First Chemical Corporation in Pascagoula, Mississippi. The explosion sent heavy debris over a wide area, injured three workers in the control room by shattered glass, punctured a nitrotoluene storage tank, and ignited a fire that burned for several hours. The CSB found that a dangerous chemical reaction had started weeks before the explosion and that the facility lacked an effective system for evaluating hazards and sharing safety information between operations.

Incident Snapshot

Field Value
Facility / Company First Chemical Corporation
Location Pascagoula, Mississippi
Incident Date 10/13/2002
Investigation Status The final CSB report on this investigation was approved at a Board public meeting in Pascagoula on October 15, 2003.
Accident Type Reactive Incident
Final Report Release Date 10/15/2003

What Happened

  • Five weeks prior to the accident, the company temporarily shut down the MNT distillation process.
  • During the shutdown, about 1,200 gallons of MNT were left inside the tower, which continued to be heated by steam pipes.
  • Operators later closed the steam supply valves to the MNT tower and shut off the facility steam system.
  • On October 5, 2002, the steam system was restarted; although the steam valves for the MNT tower were left closed, the aging valves leaked and steam again heated the MNT inside the tower.
  • During the days leading up to the explosion, the hot MNT began to decompose, forming unstable chemicals.
  • Plant operators did not monitor the tower’s internal temperature, which investigators found had hovered above 400°F.
  • On October 12, 2002, a liquid-level alarm activated from high on the tower, but no action was taken.
  • At about 5:00 a.m. on October 13, 2002, workers heard a loud rumbling noise and observed a smoky substance venting rapidly from the MNT distillation tower.
  • A short time later, the tower exploded violently.

Facility and Process Context

  • The incident occurred in the plant’s continuous MNT production process.
  • The tower was used to distill mononitrotoluene (MNT), a raw material used to produce dyes, rubber, and agricultural chemicals.
  • The continuous process had been operating at the plant since the late 1960s.
  • In 1996, the company analyzed the hazards of a separate MNT batch production process at the same facility.
  • The facility was a major producer of aniline and nitrotoluene intermediates and derivatives.
  • The control room for the aniline unit, including the MNT columns, was located approximately 50 feet from the #1 MNT column (C-501).

Consequences

  • Fatalities: 0
  • Injuries:
  • Three workers in the control room were injured by shattered glass.
  • The report also states 3 FCC employees were injured, with one requiring additional medical treatment.
  • Environmental release:
  • Heavy debris was sent over a wide area.
  • A storage tank approximately 500 feet away was punctured, igniting a fire.
  • Black smoke moved over Chevron property and the Gulf of Mexico.
  • The Jackson County Emergency Management Agency called a shelter-in-place for nearby residents.
  • Facility damage:
  • The force of the explosion blew off the upper 35 feet of the tower and sent tons of debris flying up to a mile away.
  • One piece of the tower punctured a storage tank approximately 500 feet away that contained more than 100,000 gallons of MNT, igniting a fire that burned for about three hours.
  • Several fires broke out on the plant grounds and along a nearby highway.
  • Plant equipment was damaged.
  • The control room windows burst inward.
  • The control room roof and door were extensively damaged.
  • Cinderblock walls were cracked and distorted.
  • Exterior doors were buckled and glass broken.
  • The cooling tower caught fire.
  • An administration building over 400 feet from C-501 was significantly damaged.
  • Operational impact:
  • The tower exploded violently.
  • Fires broke out on the plant grounds and along a nearby highway.
  • The facility emergency plan was activated.
  • All personnel were accounted for.
  • On-site fire brigade members fought several small fires.
  • The large fire was extinguished after about three hours.
  • All fires were out by 8:30 a.m. on October 13.

Key Findings

Immediate Causes

  • Steam leaking through manual valves heated mononitrotoluene (MNT) inside a distillation column that was shut down and thought to be isolated.
  • The decomposition of mononitrotoluene inside the distillation column resulted in a runaway reaction and explosion.
  • The rupture of the 145-foot-tall distillation column (C-501) caused the October 13, 2002 explosion and fire.

Contributing Factors

  • Plant operators did not monitor the tower’s internal temperature.
  • On October 12, a liquid-level alarm activated from high on the tower, but no action was taken.
  • The company’s instructions to employees did not provide effective guidance on how to shut off the steam supply to the MNT distillation tower.
  • Operating procedures did not require workers to take steps that could have revealed the failure of the steam shutoff valves, such as monitoring the temperature inside the tower after the valves were nominally closed.
  • The steam shutoff valves had significant steam leaks due to internal corrosion and erosion.
  • The tower lacked high-temperature alarms and interlocks.
  • The tower lacked an effective pressure-relief mechanism.
  • The control room was located too close to the distillation tower.
  • The control room windows were not reinforced to withstand excess pressure.
  • The steam line to the reboilers was not positively isolated.
  • The steam line was not double blocked and bled.
  • Blinds were not installed in the steam line.
  • The pressure safety valve (PSV-502) was inadequate to prevent overpressurization and catastrophic failure of the column.
  • The community notification system was ineffective.

Organizational and Systemic Factors

  • The facility lacked an effective system for evaluating hazards and for sharing safety information between different facility operations.
  • The results from the 1996 hazard analysis were not used to modify equipment or procedures for the continuous MNT process.
  • The training, procedures, and material safety data sheets (MSDSs) provided to operators of the continuous process did not adequately warn of the danger of heating MNT or the potential for an explosion.
  • No interlock system was added to the distillation tower to prevent overheating.
  • The facility did not have adequate safety measures, sometimes referred to as layers of protection, to prevent a major explosion involving MNT.
  • The FCC Pascagoula facility did not have an adequate management system for evaluating the hazards of processing MNT and did not apply lessons learned from hazard analyses of similar processes in the plant.
  • There was no formal hazard analysis for the continuous MNT unit or for C-501.
  • The system for ensuring consistent work practices when isolating equipment was ineffective.
  • The program to ensure the integrity of isolation valves in the steam line connected to the MNT column was inadequate.
  • The steam supply valves had not been evaluated to determine what maintenance activities were appropriate to ensure proper function.
  • FCC did not monitor the condition of the steel in C-501.
  • FCC had no documentation on the design basis for the installed PSV on C-501.
  • Neither the construction of the control room nor its proximity to the process was evaluated to ensure that employees would be protected from catastrophic events.
  • The system for notifying the surrounding community about chemical releases or other hazardous incidents was inadequate.
  • The facility had no effective system for ensuring safe work practices when isolating equipment.
  • The facility had no effective system for ensuring safe work practices when isolating equipment.
  • The facility had no effective system for ensuring safe work practices when isolating equipment.
  • The facility had no effective system for ensuring safe work practices when isolating equipment.

Failed Safeguards or Barrier Breakdowns

  • temperature limits were incorporated into the operating procedures for the batch process
  • an interlock system was installed to prevent the batch distillation equipment from overheating
  • No interlock system was added to the distillation tower to prevent overheating.
  • The tower lacked high-temperature alarms and interlocks that could have warned operators and automatically shut down the heating source.
  • The tower also lacked an effective pressure-relief mechanism in case the MNT decomposed to produce gases.
  • The control room windows were not reinforced to withstand excess pressure, and they burst inward when the accident occurred, injuring the operators.
  • First Chemical’s procedures did not explicitly require the use of either a blind or the double-block and bleed method.
  • Seven of the eight temperature indicators were functioning at the time of the incident, but they were not equipped with alarms.
  • The steam line to the reboilers was not positively isolated.
  • The steam line was not double blocked and bled.
  • Blinds were not installed in the steam line.
  • The valve seats leaked a significant amount of steam, even when the valves were in the closed position.
  • The pressure safety valve (PSV-502) was inadequate to prevent overpressurization and catastrophic failure of the column.
  • The control room was not evaluated for structural integrity or proximity to the process.
  • The community notification system was ineffective.

Recommendations

  1. 2003-01-I-MS-R1 | Recipient: E. I. du Pont de Nemours and Company | Status: Not specified | Conduct audits to ensure that the First Chemical Pascagoula facility addresses the issues detailed below, under “DuPont–First Chemical Pascagoula Facility.” Communicate results of these audits to the workforce.
  2. 2003-01-I-MS-R2 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Establish a program for conducting process hazard analyses of processes involving reactive materials.
  3. 2003-01-I-MS-R3 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Evaluate the need for layers of protection and install appropriate safeguards, such as alarms and interlocks, to reduce the likelihood of a runaway reaction and catastrophic release of material.
  4. 2003-01-I-MS-R4 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Review and revise as necessary procedures for units that process highly energetic material, effectively communicate the updated procedures, and train workers appropriately. Revised procedures should include specific steps for isolation of energy sources; warnings and cautions concerning process chemicals and consequences of deviations from operating limits; critical operating limits and guidance when the limits are exceeded; instruction on how to perform a shutdown for all foreseeable causes, to ensure proper isolation, and to continue monitoring critical parameters (such as temperature) while the column is shut down; in addition, review conditions under which material must be deinventoried (such as during extended shutdowns).
  5. 2003-01-I-MS-R5 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Conduct a facility-wide survey of pressure vessels to ensure that all equipment that processes reactive materials has appropriate overpressure protection.
  6. 2003-01-I-MS-R6 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Identify equipment critical to safe operation of processes containing reactive materials. Upgrade the maintenance program and establish inspection schedules to ensure the integrity of such equipment.
  7. 2003-01-I-MS-R7 | Recipient: DuPont–First Chemical Pascagoula Facility | Status: Not specified | Survey and take appropriate action to ensure that buildings occupied by plant personnel are of adequate construction and are located so as to protect people inside in the event of an explosion in equipment processing reactive materials.
  8. 2003-01-I-MS-R8 | Recipient: Jackson County | Status: Not specified | Update the community notification system to immediately alert residents in the Moss Point community when an incident occurs that could affect their health and safety; determine when a community response should be initiated; communicate the nature of the incident and the appropriate response by residents; alert residents when the incident is over (i.e., the all-clear has sounded).
  9. 2003-01-I-MS-R9 | Recipient: Jackson County | Status: Not specified | Conduct an awareness campaign to educate residents on the proper steps for a shelter-in-place and orderly evacuation.
  10. 2003-01-I-MS-R10 | Recipient: American Chemistry Council (ACC) | Status: Not specified | Amend the Technical Specifications guidelines in the Responsible Care Management System to explicitly require facilities to identify findings and lessons learned from process hazard analyses and incident investigations in one unit and apply them to other equipment that processes similar material.
  11. 2003-01-I-MS-R11 | Recipient: American Chemistry Council (ACC) | Status: Not specified | Ensure that ACC members understand the audit requirements of Responsible Care and accurately identify and address gaps in facility process safety programs.
  12. 2003-01-I-MS-R12 | Recipient: American Chemistry Council (ACC) | Status: Not specified | Communicate the findings of this report to your membership.
  13. 2003-01-I-MS-R13 | Recipient: Synthetic Organic Chemical Manufacturers Association (SOCMA) | Status: Not specified | Amend the Technical Specifications in the Responsible Care Management System to explicitly require facilities to identify findings and lessons learned from process hazard analyses and incident investigations in one unit and apply them to other equipment that processes similar material.
  14. 2003-01-I-MS-R14 | Recipient: Synthetic Organic Chemical Manufacturers Association (SOCMA) | Status: Not specified | Ensure that SOCMA members understand the audit requirements of Responsible Care and accurately identify and address gaps in facility process safety programs.
  15. 2003-01-I-MS-R15 | Recipient: Synthetic Organic Chemical Manufacturers Association (SOCMA) | Status: Not specified | Communicate the findings of this report to your membership.

Key Engineering Lessons

  • Shutdown and isolation procedures for reactive-service equipment must include explicit steps to positively isolate energy sources and verify isolation.
  • If a reactive material remains inventoried during shutdown, critical parameters such as temperature must continue to be monitored.
  • Alarms, interlocks, and overpressure protection are necessary layers of protection for equipment processing reactive materials.
  • Isolation valves in steam lines require an integrity and maintenance program sufficient to prevent leakage through closed valves.
  • Lessons learned from hazard analyses of one process must be applied to similar processes at the same facility.
  • Occupied buildings near reactive-process equipment should be evaluated for structural integrity and siting to protect personnel from explosion overpressure.
  • Community notification systems should be capable of immediate alerting, response guidance, and all-clear notification during hazardous incidents.

Source Notes

  • Priority 1 final report content was not separately provided; consolidation used the detailed final investigation report extract and the supporting transcript/digest, with conflicts resolved in favor of the final report extract where applicable.
  • The incident location is normalized to Pascagoula, Mississippi from the metadata spelling 'Pascgoula, MS'.
  • The report materials use both 'MNT' and 'mononitrotoluene'; both terms are preserved where relevant.
  • Some supporting documents refer to the storage tank as PNT or para-MNT; the final report extract identifies the tank as a para-MNT storage tank.
  • Repeated statements in the source documents were consolidated where they described the same finding.

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