FLAME OUT CONDITIONS IN A HEATER IS DANGEROUS!

On February 18, 2023, at 2:50 p.m., flammable fuel gas ignited, resulting in an explosion of a boiler at a  Coke Plant in Ohio. Estimated property damage was approximately $1 million.

On the day of the incident, tubes inside the boiler were carrying water, and a burner inside the structure heated the water to produce steam. The boiler’s burner was combusting fuel gas (composed of natural gas and coke oven gas) to heat the water to produce steam. The forced draft fan that introduced air to the burner unexpectedly shut down, and without air being fed to the burner, the burner flame went out. Flammable fuel gas continued to enter and accumulate in the boiler, however, and about ten minutes later, the accumulated flammable gas ignited, resulting in an explosion. The company determined that the oxygen analyzer installed in the boiler was the source of ignition. The explosion caused extensive damage to the boiler and ductwork.
The company's investigation found insufficient alarms to alert operators that the forced draft fan had shut down. A visual alarm signaling loss of air had activated on a control room screen, but the operator was looking at a different screen at the time of the incident and did not see the alarm. In addition, there were no cameras installed to monitor the burner flame and no dedicated video monitor for operators to view the boiler exhaust, which could have indicated an operational problem with the boiler. After the incident, the company’s corrective actions included installing audible alarms for the boiler fans, cameras on the burners, and a dedicated video monitor for the boiler exhaust.
The company did not determine the amount of the combustion products accidentally released, but the company estimated that approximately 28,000 cubic feet of fuel gas had accumulated before the explosion.

Based on the company's investigation, the probable cause of the incident was the ignition and explosion of accumulated flammable fuel gas inside a boiler. The flammable fuel gas accumulated in the boiler after the air flowing to the boiler’s burner stopped, and the burner flame went out. Insufficient safeguards to prevent fuel gas from flowing to the boiler when the burner flame went out contributed to the incident.

Source:CSB.gov