At approximately 7:20 a.m. on April 3, 2017, the bottom of a steam condensate (hot water) storage tank catastrophically failed at the Loy-Lange Box Company (LLBC), located at 222 Russell Boulevard in St. Louis, Missouri. The 1952-pound, 30-inch diameter by 17-½-feet long steel tank, called a Semi-Closed Receiver (SCR)4 contained about 510 gallons condensed steam (water at about 330 °F and 100 psig.) Condensate from the vertically-mounted SCR was normally sent to two associated steam generators.

As the pressure in the tank suddenly dropped due to the failure of the tank bottom, a portion of the water in the SCR instantaneously exploded into steam, resulting in an increase in volume of about 75 times the volume of the SCR. A steam explosion of this type is extremely hazardous. The energy released was equivalent to about 350 pounds of TNT. Some of that energy dissipated when the escaping steam condensed to water, but the surveillance video from a nearby custom work truck shop clearly shows the power of the explosion and the effect on the building, as does the damage evident after the event.

The force of the steam explosion exiting the bottom of the SCR destroyed a large portion of the LLBC facility, and launched the storage tank like a rocket through the roof. One LLBC employee was fatally injured, and a second was left in critical condition.

Even after pulling loose from all of the piping and floor attachments, and crashing up through the structure of the building and out through the roof, the 1952-pound SCR was still traveling at about 120 mph. It rose to about 425 feet above street level and traveled laterally across about 520 feet. It remained airborne for over 10 seconds. As it fell, the SCR crashed through the roof of Faultless Healthcare Linen’s property at 2030 S. Broadway, fatally injuring three individuals.

KEY ISSUES:
• CORROSION
• MECHANICAL INTEGRITY & INSPECTION

ROOT CAUSES:
1. Steam generator repairs.

Image credit: CSB