This accident occurred December 7, 2009, with a violent rupture of an ASME pressure vessel. The video contains an animation which depicts the stress corrosion cracking (SCC) that accumulated over time in the walls of a pressure vessel where synthetic quartz crystals were manufactured under extremely high pressures and temperatures. The incident had many failures and is a case study on PRESSURE VESSEL MANAGEMENT. Improper design, construction, testing, and inspection ALL played a roll in this CATASTROPHIC FAILURE of an ASME PRESSURE VESSEL. So the next time anyone tells you “these vessels just do not have a history of failing”… well now you know!
A combination of animation and surveillance video shows how one piece of steel from the building was blown 650 feet, striking and killing a truck driver who was walking back to his vehicle. Another piece – a vessel fragment weighing over 8,000 pounds – tore through a wall at the facility, skipped across a neighboring parking lot and struck the wall of an automotive supply company where 70 people were working; but only one was injured. The video displays text of a direct warning by a third-party safety auditor called in by the plant insurance carrier following an uncontrolled leak of hot, caustic material in January 2007 from the lid of another similar pressure vessel. The consultant concluded the accident resulted from the vessel’s improper design, fabrication and material selection, determined four vessels were experiencing stress corrosion cracking, and advised against returning any of the facility’s eight vessels into service, saying “far more catastrophic scenarios are possible,” specifically naming danger of public death or injury at the gas station where the truck driver would be killed in 2009. But the plant never established an internal vessel inspection program and did not perform testing on the vessels before returning them to service.
The CSB found that the Illinois Board of Boiler and Pressure Vessel Safety – after incorrectly designating the vessels for non-corrosive service – did not conduct internal inspections. The state conducted three inspections of the vessel that failed in 2003, 2006 and 2009 (less than three months prior to the incident) but these inspections focused ONLY on accessible external surfaces and did NOT look for inside corrosion.
The investigation determined that the vessels did NOT meet requirements of the American Society of Mechanical Engineers’ (ASME) Boiler and Pressure Vessel Code. The report found the vessel walls, eight inches thick, exceeded the recommended limits – seven inches, making them possibly too thick for proper heat treatment during manufacturing. Investigator Lucy Sciallo-Tyler said, “Evidence from the 2007 and the 2009 accidents suggests the excessive wall thickness at ____ resulted in improper manufacturing and contributed to the metallurgical damage mechanism that led to the catastrophic rupture.”
The investigation also examined zoning laws that permitted the plant to be built near the Illinois Tollway Oasis and other nearby businesses including the automotive supply company. The CSB found that the plant’s property was zoned “light industrial,” for businesses such as car repair shops or lumberyards. Investigators determined that the plant should have been considered “heavy industrial,” in the category of oil refineries, metal and ore manufacturing and fertilizer manufacturing. However, the CSB found no evidence the plant informed the City of Belvidere that its pressure vessels would operate at extremely high and potentially dangerous temperatures and pressures typical of heavy industry.
KEY FINDINGS
- Stress corrosion cracking likely caused the catastrophic rupture of a high-pressure crystal production vessel, fatally injuring a member of the public 650 feet away at a highway rest stop.
- The company relied upon the in-process formation of an acmite coating inside the production vessel to protect the low alloy, high-strength steel from caustic sodium hydroxide used in the manufacturing process. However, the plant did not verify the integrity or effectiveness of this coating, and the caustic chemicals promoted stress corrosion cracking that weakened the vessel.
- The Illinois Board of Boiler and Pressure Vessel Safety did not conduct internal inspections of the vessels as required under state regulations for pressure vessels subject to internal corrosion. Instead, the state says it relied on the company to perform internal inspections, but it did not verify whether these were actually occurring. The state conducted three certificate inspections of the vessel that failed in 2003, 2006, and 2009 (less than three months prior to the incident) but these inspections focused only on accessible external surfaces.
- In 2007, the plant learned that stress corrosion cracking was occurring in four of eight pressure vessel lids at the facility. A consultant to the insurance company warned of “serious reservations” about returning the vessels to service after this discovery and specifically cited the possible danger to members of the public at the nearby rest stop in case of a catastrophic vessel failure.
- Despite the insurance company warning, the plant did not perform recommended non-destructive examinations of all vessels prior to returning the vessels to service.
- The plant did not perform annual internal inspections as recommended by the vessel designer when the vessels were initially constructed.
- Temper embrittlement, or some other form of heat treatment embrittlement, cannot be ruled out as a contributing factor in addition to the SCC. The vessels exceeded the ASME wall thickness recommendations for closed-end forgings, which may have resulted in improper heat treatment during the manufacturing process.
- The ASME Boiler and Pressure Vessel Code does not have specific wall thickness limitations for pressure containing components.
CLICK HERE for the full CSB Report