A design change during maintenance in 2011 was a contributing factor in the collapse of a 150-foot tower at Imperial's Sarnia site, the company said.
In a message to the community posted on Facebook Thursday, refinery manager Rohan Davis said the cause of the collapse on April 2 has been attributed to pyrophoric materials that can ignite when exposed to air. He said the design change "unknowingly increased the risk of pyrophorics" and their investigative team "was able to verify with absolute certainty that the cause was not related to the age, inspection or maintenance of the tower."
Davis told BlackburnNews.com that pyrophoric material is generated as part of processing oil and gas, and is not an issue during normal plant operations.
"However, in this case here, we were opening up some equipment for maintenance, and the pyrophoric material generated heat which resulted in the failure of the tower," said Davis.
He noted the tower had been opened several times in the past without issue, before the design change.
"The recommendations from the investigation are very focused on changes to procedures and work processes that we have within the company, and how we design equipment and how we'll open it and manage it in the future," he said.
Davis said they've carefully reviewed other equipment at the Sarnia site, and they're circulating the findings of their investigation across all Imperial and ExxonMobil refineries, as well as sharing the findings with industry across Sarnia.
Imperial was under environment ministry direction to report on the cause of the collapse by the end of June.
Luckily no one was hurt when the fuel processing tower collapsed the night of April 2.
It was being prepared for planned maintenance at the time and did not contain petroleum products.
Davis said the collapsed tower was moved last Sunday but remains on site and work is being done to make sure it's safe for transportation. He said the cleanup and demolition of the impacted area is underway, and a new tower is being built locally that will incorporate learnings from their investigation.
-With files from Melanie Irwin