As the North Star fire raged close to ammonia tanks, officials evacuated the entire town of St. Charles, Minn.
Photos courtesy of Minnesota State Fire Marshal Division

A process heating consulting company and a burner manufacturer whose product it recommended, installed and serviced have been sued by a food processor more than a year after a fire destroyed the plant. North Star Foods of St. Charles, Minn., now known as Northern Meat Products Inc., claims in its lawsuit filed in U.S. District Court in Minneapolis, that the fire, which caused the evacuation of the entire town of about 3,300 residents, was the fault of Marshall W. Nelson & Associates, Milwaukee, and Flynn Burner Corp., New Rochelle, N.Y.

According to the lawsuit, the fire occurred April 17, 2009, about 30 minutes after a Marshall Nelson technician serviced and adjusted the Flynn burners in the meat processing plant’s natural gas highlighter oven, which places grill-like marks on meat.

The burners, which had been installed just two months earlier, still were being tweaked to meet product requirements, according to the state fire marshal’s report. Shortly after the technician left, employees saw smoke and fire in the ceiling immediately above the highlighter.

The highlighter oven at the food processing plant and all its components were destroyed in the fire.

The fire spread rapidly and the plant was evacuated. Because the building contained an ammonia refrigeration system with nearby tanks containing thousands of pounds of anhydrous ammonia, fire officials also evacuated the town. Although the building was destroyed, no one was seriously hurt. North Star claims that property damage and business losses exceed $55 million.

The fire investigation report says the fire originated at the exhaust chimney for the highlighter oven within the checker cook portion of the process line. The Flynn direct-flame burners replaced infrared panels and still were being tweaked to get the desired effects.

The new burner system created “potential for more heat to develop within the checker room itself, within the vent hood or the exhaust stack,” according to the report’s author, Steve Wolf, deputy state fire marshal, who investigated the fire.

“It is my opinion that heat built up to the point where it heated the exhaust stack which, in turn, ignited caulking, wood, rubber roof membrane, or Styrofoam insulation,” Wolf writes. “It appears that the exhaust vent may not have been large enough or adequate for the heat produced or there was a situation involving a failure of an exhaust blower or motor on these powered vents.”

While the fire that ravaged the plant started in the oven’s exhaust, the state’s fire investigation report notes that pinpointing the exact cause of the fire can't be determined at this time.

In its response to the lawsuit, Marshall Nelson denies it was at fault. Flynn has not yet responded to Process Heating’s inquiries.

Wolf notes that while it is significant that a service technician was present just prior to the fire and had made adjustments to the burner system, “one cannot overlook the possibility this fire could have smoldered for some time prior to being noticed.”

Also, in the report’s conclusion, Wolf notes that it is yet unknown if any of the blower motors or exhaust-removal equipment were working and installed properly. Without further information, Wolf says the exact cause of the North Star fire is undetermined.