CSB report on furnace explosion

The CSB has issued a report on the carbide furnace explosion. The CSB states that:

"The investigation report proposed two scenarios for the development of cooling water leaks that likely resulted in the overpressure and explosion. In one scenario, fouling – or the accumulation of solids inside the hollow chamber where water flows – resulted in localized overheating, eventually causing sections of the cover to sag and crack. 

           

 Another possible cause of the leaks could have been the sudden eruption of hot liquid from the furnace, which operators called a “boil-up.” Hot liquids contact the underside of the furnace cover, eroding its ceramic lining, and eventually melting holes through which water leaks. Post-incident examination revealed recurring water leaks in multiple zones of the furnace cover. Rather than replacing the furnace cover, the company directed workers to attempt repairs. The investigation found that the company would inject a mixture of oats and commercially available “boiler solder” into the cooling water, in an effort to plug the leaks and keep the aging cover in operation.

 

 Water leaks into the furnace interfere with the steady introduction of lime and coke raw materials, through an effect known as “bridging” or “arching,” the report noted. In a carbide-producing electric arc furnace, this can result in an undesirable and hazardous side reaction between calcium carbide and lime, which produces gas much more rapidly that the normal reaction to produce calcium carbide itself. Industry literature described the phenomenon as early as 1965, and an independent CSB analysis confirmed that operating conditions at Carbide on the day of the incident could have resulted in this effect, causing hot materials to be expelled from the furnace.

             

 CSB lead investigator Johnnie Banks said, “One of our key findings was that Carbide Industries issued 26 work orders to repair water leaks on the furnace cover in the five months prior to the March 2011 incident. It was distressing to find that the company nonetheless continued operating the furnace despite the hazard from ongoing water leaks. We also found that the company could have prevented this incident had it voluntarily applied elements of a process safety management program, such as hazard analysis, incident investigation, and mechanical integrity.”

Read the report in this link. 


Contribute to the surviving victims of Bhopal by buying my book "Practical Process Safety Management"