Stuck gas valve triggers boiler to overheat and sustain damage

The resident building manager of a multi-story residential building found an issue in the building's boiler room and contacted a mechanical contractor. The contractor who attended the scene found that the boiler room was full of steam and the boiler was running. The boiler was de-energized but continued to run even without electricity. In order to stop the flow of gas to the unit, the manual gas shutoff valve was closed.

Upon investigation, it was discovered that the boiler’s gas valve was stuck in the open position, bypassing the system's electronic safety controls and allowing an uncontrolled flow of gas to the boiler’s main burners. The boiler’s supply and return piping system and safety controls were damaged after the boiler overheated.

The boiler involved was supplying the heating water to the building’s hydronic heating system. A circulating pump circulates water through the boiler, which is heated to the desired temperature (180 degrees F) and supplied to the heat emitters serving the building’s suites.

Other factors that contributed to the incident were the age of the valve and the lack of a redundant second valve.

Read the complete incident investigation report.

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