Morton International Inc. Runaway Chemical Reaction

To workers at the Morton International chemical plant in Paterson the evening of April 8, the gathering noise “sounded like a train rumbling through.” The 2,000-gallon chemical reactor shook as the internal temperature rose ever higher.Nearly four decades old, the kettle was nine feet tall with carbon-steel walls an inch thick. Inside were thousands of pounds of reacting chemicals. Minutes earlier, everything had appeared to be normal. At 7:40 p.m., workers turned on the steam supply to the kettle, beginning what they assumed would be a routine sixto eight-hour production run of Automate Yellow 96, a dye used to tint petroleum fuel products. But the lead operator watched with concernas the kettle temperature began to climb precipitously, reaching 212˚F less than half an hour later, at 8:05 p.m. A vigorous heat-producing reaction was underway, and it was warming the kettle much faster than steam alone would do.

To control the reaction, the lead operator decided to cut off the steam and turn on the cooling water. A couple of minutes later, the kettle began to vibrate ominously as it surpassed the intended maximum processing temperature of 300˚F. Liquid and gas began venting from the top of the kettle, as the internal pressure built. Unknown to the workers, the chemicals inside the kettle would begin to decompose at 380˚F. That would initiate an even more violent runaway reaction that could rip the steel vessel apart.

Moments later, as the temperature rocketed past 380˚F, the rumbling grew louder still. Workers began rushing for the exits. At about 8:18 p.m., the Morton plant shook as accumulated pressure blew off the 18-inch metal hatch that was clamped to the top of the kettle. The kettle was lifted from its moorings and driven into the floor below. A fiery stream of gas and liquid erupted through the roof of the building, raining down chemicals onto the surrounding community. Residents in a 100 city-block area were confined to their homes, voluntarily sheltering in place for up to three hours while officials evaluated health risks. Firefighters and workers in neighboring businesses reported throat, eye, and skin irritations consistent with chemical exposure. Meanwhile, the last two fleeing workers had been caught by the blast and were knocked down a flight of stairs before collapsing to the ground. In all, nine workers were injured, including two with severe burns. As one of the injured said later at a public meeting of the U.S. Chemical Safety Board, “The pressure was so much on me, I couldn’t move. It had pinned me against the wall. It seemed like forever.”

The CSB investigation found that Morton had not adequately evaluated or controlled the hazards of the Yellow 96 production process. Neither the preliminary assessment conducted in 1990 nor a subsequent hazard analysis five years later considered the possibility of a runaway chemical reaction – one of the most common reactive hazards. As a result, the production kettle was not provided with sufficient cooling capacity or adequate emergency shutdown or venting systems. Morton’s analyses never considered possible scenarios – such as excessive heat input or inadequate cooling – that could trigger a runaway reaction.