General Major Incident # 3: NDK Crystal Inc. Explosion with Offsite Fatality

general incidents Oct 01, 2020



1. Location:

On 12/07/2009, in the NDK Crystal Inc. Explosion with Offsite Fatality, located in Belvidere, IL.


2. Incident Description:

The incident resulted from corrosion in a pressure vessel, which was not inspected for years. The rupture occurred in the Number 2 vessel which was growing synthetic quartz crystals at extremely high pressure and temperature. One piece of steel from the building was blown 650 feet, striking the 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.


3. Links to the photos or videos related to this incident


4. Root Cause of Failure:

• Stress corrosion cracking likely caused the catastrophic rupture of a high-pressure crystal production vessel at NDK Crystal, Inc.

• NDK 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, NDK did not verify the integrity or effectiveness of this coating, and the caustic chemicals promoted stress corrosion cracking that weakened the vessel.


5. Financial Loss:

The total loss was $950,000.


6. Safety Consequences:

There was not death and injury inside the NDK Crystal but Fatally injured a member of the public 650 feet away at a highway rest stop.


7. Environmental Consequences:

The state EPA said about 800 gallons to 850 gallons of sodium hydroxide solution as well as quartz crystals were released during the explosion. However, the agency suspects that wastewater and process chemicals might have been discharged through the facility’s floor drain.


8. Did the company have any RBI or Reliability or Integrity program at the time of incident?

Yes, As a result of the vessel lid failure investigation, in July 2007 the consultant hired by NDK’s insurance company notified the insurer it had “serious reservations” about returning any of the vessels to service, specifically Vessels No. 3 and 5, and a decision to do so would be a “seriously flawed decision and not based on sound engineering analyses.


9. Was there any missing inspection or reliability practice that has led to incident?

The CSB found that had NDK Crystal ignored a direct warning by a third-party safety auditor called in by its 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. NDK never established an internal vessel inspection program and did not perform testing on the vessels before returning them to service


10. How this incident could have been avoided?

If NDK established an internal vessel inspection program so they could have known that the raw mined quartz, or silica which was mixed with a corrosive sodium hydroxide solution at high pressures and temperatures and as a resulting reaction with the steel vessels formed a layer of iron silicate, called acmite, on the inside of the vessel walls, which the company believed would protect the vessels from corrosion, if the inspection was done company could find that corrosion is occurring, resulting in a phenomenon known as stress corrosion cracking, or SCC, NDK continued to operate the vessels without performing the recommended inspections


11. What were the main recommendations of the CSB to solve the problem?

• Revise the ASME Boiler and Pressure Vessel Code to include specific material thickness limitations for the design of pressure-containing components to ensure proper heat treatment and avoid environmentally induced damage mechanisms.

• Develop and implement state requirements and procedures to ensure the pressure vessel approval process accurately identifies vessels that may be subject to corrosion or similar deterioration mechanisms, and ensure regular inspections in accordance with these state requirements.

• Implement an annual inspection and corrective action program to ensure vessels remain resistant to environmentally induced damage mechanisms based on the inspection guidelines set forth in the American Petroleum Institute (API) Standard 510, Pressure Vessel Inspection Code


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