- Photo courtesy of KTRK.

Photo courtesy of KTRK.

A ruptured filtration filter is the focus of a U.S. Chemical Safety Board investigation into an explosion and fire at a Texas chemical plant in April that killed one person and injured 30 others, an update issued this week states.

On April 2, 2019, the operational staff at the KMCO facility in Crosby, TX, was engaged in making a batch of sulfurized isobutylene. Sometime later an operator walking by the sulfurized isobutylene batch reactor heard a loud "pop" followed by a loud whooshing noise similar to "an air hose coming off."

Investigating further the operator described a white cloud of vapor hovering near the ground with three or four feet of wavy, hazy vapor above it. An immediate evacuation order was issued via the plant radio system.

Approximately four minutes later the isobutylene vapor cloud exploded. After the blast, with a hole roughly three inches by 5.5 inches was found in a cast iron filtration strainer or y-strainer on the inlet suction piping to the isobutylene charge pump, the update states.

At least one witness said the strainer's location was consistent with where isobutylene was seen escaping, the update states.

The resulting blast levelled a building previously used as a control room. One of the responders described what the building looked like after the explosion.

"There was nothing left of it," the responder said. "Wires, there was nothing there. There wasn't a building there anymore."

The single fatality was found near the entrance of the destroyed building, the update reports.

Meanwhile, the CSB investigation is ongoing. Investigator will continue developing the incident causal analysis based on evidence collected with the goal of issuing a final report after completition.