Accidental Production of Hydrogen and Fire in a Silicone Manufacturing Plant
The event occurred in a silicon hydride (SiH) emulsion production process inside an enclosed production building. The process generated a flammable gas cloud gas ignited, which later ignited causing an explosion and fire.The explosion caused four fatalities and one injured worker, heavily damaged the production building and its force was felt up to 20 miles away. According to the CSB preliminary report, various investigations are still ongoing to understand in details the sequence of events of this accident. The most plausible explanation is that the flammable mixture (hydrogen) has been generated by the run-away of a chemical reaction when producing the SiH emulsion. Short before the start of the accidents, the reactor tanks were seen producing a large quantities of foam, typically induced by bulk production of hydrogen in viscous liquids. This emulsion is made of silane (SiH4) and siloxane polymers. One of the raw materials used to make this emulsion is a methyl-hydrogen polysiloxane copolymer, which is a SiH compound. All these chemicals have the capability of producing large amounts of hydrogen gas under certain conditions (pH, temperature, chemical bonds, total mass, catalysts presents).
Event Date
May 3, 2019
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes (Select all applicable options):
Cause Comments
The immediate cause of the event was the production of a flammable mixture (very probably hydrogen) and its delayed ignition during a chemical reaction process.Contributing cause were the absence of flammable gas detectors or hydrogen gas detectors able to warn workers. Also the position of the main air mover near the process location and the decision to open the door of the building to remove smoke increased the potential of explosion from flammable gases.The root cause is very probably to be found in the absence of preventive and mitigating measures tailored to that specific chemical process. This implies an inadequate risk assessment.
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
silicon-hydrogen reaction tanks
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
The production process had a highly manual was character. It used two atmospheric tanks equipped with agitators. These vessels did not have automatic feeds, requiring operators to add raw materials into the tanks manually. Also the assessment of the quality of the reaction required visual operation. At the time of the incident there were nine employees onsite. The reaction was on going when one of the tank started overflowing with foam. The shift supervisor ordered to open the garage doors and to turn on forced ventilation to remove the hazy vapor which had started to form. Before these two actions could take place, the explosion took place.
Lessons Learned
The CSB report (see references) says that the root cause investigation is still ongoing (checked October 2020). Nevertheless, from the absence of flammable gas (hydrogen) detection, it can be already concluded that the risk assessment of this process was not foreseeing the possibility of hydrogen evolution, suggesting an inadequate risk inventory and/or the failing of setting the related preventive measures. One of these measure (compliance of electrical equipment and installations in the production approved for hazardous locations) is the reason of the OHSA legal penalty request..
Emergency Action
The local fire department responded to the scene 13 after the start of the fire. Mutual Aid from surrounding areas responded and provided support, as swell as the Hazardous Materials and Special Technical Rescue The fire was mostly extinguished after one and a half days.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
OHSA (Occupational Safety and Health Administration) news of 25/10/2019
https://www.osha.gov/news/newsreleases/region5/10252019
(accessed October 2020)
616_HIAD_938 picture from the ABS report.JPG
OHSA (Occupational Safety and Health Administration)full repor:
(accessed October 2020)