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Catalyst Systems Inc. Reactive Chemical Explosion

Overview

On January 2, 2003, a vacuum dryer holding nearly 200 pounds of benzoyl peroxide (BPO) exploded at the Catalyst Systems Inc. production facility in Gnadenhutten, Ohio. Employees were drying granular 75 percent BPO to make 98 percent BPO when the material explosively decomposed. The explosion and subsequent fire damaged the BPO processing building. One employee received a minor injury while evacuating.

Incident Snapshot

Field Value
Facility / Company Catalyst Systems, Inc.
Location Gnadenhutten, OH
Incident Date 01/02/2003
Investigation Status The Board approved a case study report on this investigation at a public meeting in Washington, DC, on October 29, 2003.
Accident Type Reactive Incident
Final Report Release Date 10/29/2003

What Happened

  • On Friday morning, December 27, Catalyst Systems employees began normal procedures to prepare a batch of 98 percent BPO.
  • The vacuum dryer was loaded with 200 pounds of granular 75 percent BPO and started.
  • Hot water to the dryer was shut off at about 2:00 pm to allow the material to cool.
  • At approximately 3:30 pm, the entire drying system was shut down for the day.
  • On Monday morning, December 30, operators followed normal procedure to restart the drying system.
  • The drying process was repeated.
  • On the following 2 days—plant holidays—the drying system was not operated, and the dryer remained sealed.
  • Plant personnel returned to work on January 2, 2003.
  • The dryer was opened and sampled at approximately 8:00 am.
  • The plant laboratory determined the concentration to be 97 percent BPO.
  • The drying system was started.
  • At about 8:50 am, operators heard the hot water valve close, indicating that the temperature inside the dryer had reached 42°C.
  • They then closed a manual valve on the hot water line to ensure that the hot water did not automatically restart.
  • The dryer continued to rotate under vacuum to allow the material to cool.
  • At 11:30 am on January 2, the operators took their lunch break at a table located in the Building 2 paste room.
  • One of the operators noted an unusual noise coming from the vacuum pump.
  • At 11:55 am, the vacuum dryer suddenly exploded while the operators were still seated at the lunch table.
  • The employees described thick black smoke with rolling flames and a loud boom.
  • They quickly exited the building and went to the designated evacuation area.
  • One of the employees received a minor puncture wound on his shoulder, possibly from flying debris.
  • The automatic building sprinkler system activated.
  • The Gnadenhutten Police and Fire Departments responded immediately; they extinguished a small fire in the southwest corner of the paste room.
  • The Tuscarawas County Hazardous Materials Team and several other nearby fire departments were called to assist.
  • Following the advice on the material safety data sheet (MSDS) for BPO, the fire department continued to put water on the building and its contents.
  • Runoff water leaving the property was tested at several locations and determined to be non-hazardous.

Facility and Process Context

  • Catalyst Systems is a wholly owned subsidiary of U.S. Chemical and Plastics, Inc., a privately owned corporation headquartered in Massillon, Ohio, which is a subsidiary company of Alco Industries.
  • Twenty-five people are employed at the facility in Gnadenhutten, Ohio.
  • The plant site has two buildings.
  • Building 1 contains offices, a quality control laboratory, a shop, storage areas, and a paste filling and packaging area.
  • Building 2 was constructed in 1977 and is used solely for BPO production.
  • Building 2 is divided into a manufacturing area and a paste room.
  • In the manufacturing area, raw materials are added to a reactor to produce 20 percent BPO, which is then sent through a centrifuge, where water is removed.
  • The resulting product is 78 percent granular BPO.
  • Some of this material is packaged in drums for sale or further processing.
  • In the paste room, the 78 percent BPO, a plasticizer, water, pigments, and surfactants are mixed to create 50 percent BPO paste.
  • A 98 percent granular BPO product is also made in the paste room by drying batches of purchased 75 percent granular BPO using a spherical rotating vacuum dryer.
  • The 98 percent product is packaged into 1-pound bags.
  • Catalyst Systems began producing 98 percent granular BPO 5 years ago for the rubber, marine, and printed circuit board industries.
  • This product was initially manufactured by air-drying 75 or 78 percent BPO granular products in open metal pans in an oven over several days.
  • Because the process was both time consuming and subject to quality problems, Catalyst Systems determined that vacuum drying was more economical and maintained the required quality control.
  • In June 2001, Catalyst Systems purchased a used double-cone vacuum dryer, which was jacketed and glass-lined.
  • Maintenance personnel installed the equipment and placed it in the northwest corner of the paste room.
  • The vacuum dryer was loaded through a feed port with 200 pounds of 75 percent BPO.
  • Hot water (approximately 82°C) was circulated through the dryer’s jacket to indirectly heat the BPO.
  • The dryer rotated slowly, causing the BPO to tumble and evenly heat, minimizing the production of hot spots.
  • The atmosphere in the dryer was placed under vacuum.
  • As the BPO was heated, the vacuum system pulled air and water vapor from inside the dryer through a polypropylene bag filter, then a separator, and finally to a water suction vacuum pump.
  • Hot water from the building’s heating system circulated through the dryer’s jacket.
  • There were three automatic valves in the hot water piping.
  • When operating normally, valves V1 and V2 are open and V3 is closed.
  • A temperature control system used a probe located inside the vacuum dryer to determine when to open and close the hot water valves.
  • When the thermocouple reached 42°C, the inlet and outlet valves on the jacket lines closed and the bypass line opened, which stopped hot water from circulating through the jacket.
  • A typical batch took 2 to 2.5 working days to dry from 75 to 98 percent BPO.
  • The drying system was started in the morning and ran until about 2:00 pm, when the hot water was shut off; however, the dryer continued to rotate under vacuum until 3:30 pm, when the entire system was shut down for the evening.
  • The same procedure was followed on the second day.
  • On the morning of the third day, the cover was removed and a sample taken for analysis.
  • If the concentration was at 98 percent, the dryer was unloaded; otherwise, the BPO was subjected to additional heating cycles.
  • The 98 percent BPO was emptied through the bottom butterfly valve discharge opening into fiber drums.
  • BPO from the drums was then packaged in 1-pound plastic bags—20 bags to a box—for shipping.
  • The dryer was cleaned after every second batch by rinsing with water and allowing it to air-dry with the doors open.

Consequences

  • Fatalities: 0
  • Injuries: One employee was slightly injured; one employee received a minor puncture wound on his shoulder, possibly from flying debris.
  • Environmental release: Runoff water leaving the property was tested at several locations and determined to be non-hazardous.
  • Facility damage: The BPO processing building was significantly damaged. The dryer was propelled through the corrugated steel dividing wall and through several pallets of filled fiber drums. The siding and siding supports on the south side of the building, as well as the dividing wall, were extensively damaged. The building’s primary structural frames were intact, though the roof decking and supports in the southwest corner were badly damaged.
  • Operational impact: The vacuum dryer exploded and the BPO processing building was significantly damaged; the automatic building sprinkler system activated and a small fire in the southwest corner of the paste room was extinguished.

Key Findings

Immediate Causes

  • The January 2 explosion at Catalyst Systems was most likely caused by a thermal decomposition of 98 percent BPO.

Contributing Factors

  • Other possible causes or contributors include contamination, static electricity, or friction.
  • The Catalyst Systems BPO drying system had no indicators or recording devices for temperature or pressure; it was primarily manually controlled.
  • Because the drying system was extensively damaged and there was little recorded information, it was not possible to determine exactly what initiated the explosion.
  • The drying system was running very close to the thermal decomposition temperature for 98 percent BPO.
  • The self-accelerating decomposition temperature (SADT) for a 1-pound bag of 98 percent BPO is 68°C.
  • Half-life data suggest that half of the 98 percent BPO in the dryer would have decomposed in about 3 hours at 82°C.
  • Catalyst Systems was aware of the SADT for a 1-pound package of BPO, but this information was inappropriately used to determine the high temperature limit for the much larger amount in the dryer.
  • Little consideration was given to adequately grounding the dryer to dissipate static charges that might accumulate while the material tumbled.
  • There was no consideration of whether the polypropylene bag filter over the vacuum inlet might be a source of static electricity inside the dryer.
  • It is unknown whether the grease in the sealed bearings was conductive.
  • If nonconductive grease was used, the rotating dryer shell might have been totally isolated from the frame, allowing static charges to accumulate on and inside the dryer.
  • There was no wiring diagram, no sketches or basic process flow diagrams, and no engineering drawings for major system components.
  • There were no written operating procedures for drying BPO using the vacuum dryer; management provided only verbal instructions to the operators.
  • Catalyst Systems did not conduct a reactive hazard evaluation.
  • Catalyst Systems did not complete any formal hazard reviews during design and installation of the BPO drying system.
  • Catalyst Systems did not complete a prestartup safety review.
  • During its design process, Catalyst Systems planned to include redundancy in the control of valves in the heated water piping to protect against the failure of a single valve; however, this safety feature was removed due to wiring problems during installation.
  • Catalyst Systems had no established preventive maintenance program for the BPO drying system.
  • The temperature controller was critical to safe operation of the system and should have been included in such a program.
  • Interviews with operators revealed that a chip had developed in the glass lining.
  • Granular BPO may have become lodged in this chip and overheated, creating a hot spot.
  • The metal under the glass lining provided a potential source of contamination.
  • Operators received on-the-job training only.
  • There were no written procedures and no structured training.
  • There were no procedures for abnormal situations.

Organizational and Systemic Factors

  • Catalyst Systems did not have a process safety management program in place, nor were employees trained in the use of these management systems.
  • The development, understanding, and application of process safety information during process design was inadequate for managing the explosive decomposition hazard of 98 percent BPO.
  • Catalyst Systems did not have a management system in place that mandated prestartup safety reviews.
  • Catalyst Systems should have reviewed consensus standards and guidance documents on the handling, storage, and manufacture of BPO, and implemented their recommended practices.
  • Dry BPO is hazardous in any quantity.
  • Regardless of OSHA PSM coverage, companies should implement good engineering practices when working with BPO, such as gathering relevant hazard information, reviewing reactive hazards, developing a preventive maintenance program, and developing and conducting training on operating procedures for normal and abnormal situations.

Failed Safeguards or Barrier Breakdowns

  • The Catalyst Systems BPO drying system had no indicators or recording devices for temperature or pressure.
  • The temperature control system relied on a probe located inside the vacuum dryer.
  • The jacket was not designed to be drained; the water remained in the jacket at 82°C until it was cooled by heat losses to the surrounding environment.
  • There were no temperature controls and alarms installed accordingly.
  • Equipment used to heat organic peroxides should be isolated from storage areas, other equipment, and work areas.
  • Buildings that house manufacturing equipment should be built with fire- and explosion-resistant walls with adequate capabilities to vent pressure.
  • Safeguards should be in place to protect against the possibility of exposing BPO to ignition sources, friction, and shock.
  • Electrical equipment in areas with open containers of BPO should be classified according to Class I, Division 1, of Article 500 of the National Electric Code.
  • All equipment should be adequately grounded.
  • BPO generates large volumes of gases during decomposition and should not be confined.
  • Precautions should be taken to avoid contamination, which may initiate the decomposition reaction.
  • There were no written operating procedures for drying BPO using the vacuum dryer.
  • There was no formal process hazard analysis.
  • There was no prestartup safety review.
  • There was no established preventive maintenance program for the BPO drying system.
  • The temperature controller was not included in a preventive maintenance program.
  • The glass lining was not inspected and repaired as necessary.
  • Operators were not trained on abnormal situations.

Recommendations

  1. Recommendation 1
  2. Recipient: Not specified in provided source text
  3. Status: Not specified in provided source text
  4. Summary: Not specified in provided source text

Key Engineering Lessons

  • Do not use self-accelerating decomposition temperature data for a small package to set operating limits for a much larger process inventory without process-specific evaluation.
  • Reactive chemical drying systems need temperature and pressure indication or recording, not only manual control.
  • Static electricity, friction, contamination, and hot spots must be evaluated as credible hazards in rotating vacuum drying of benzoyl peroxide.
  • Critical controls such as temperature controllers and valve redundancy should be included in preventive maintenance and design reviews.
  • Written operating procedures, abnormal situation procedures, and structured training are necessary for safe operation of reactive chemical processes.
  • Process hazard analysis, reactive hazard evaluation, and prestartup safety review are needed before and during operation of a benzoyl peroxide drying system.

Source Notes

  • Priority 1 final report used as primary authority for incident facts, findings, and consequences.
  • Priority 4 supporting documents were used only to supplement sequence and context where consistent with the final report.
  • Where the transcript and final report both described the event, the final report terminology was preferred.
  • No external facts were added beyond the provided source extracts.

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