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Gas Pressure Regulator Failure and Building Explosion

DATE:2014-06-27 | comments: | posted by:admin
An apartment building exploded when a utility’s pressure regulator failed and injected natural gas under the fumigation tent.

A fumigation company “tented” a termite-infested, two-story apartment building. The fumigators turned off the gas to the building, but left the electricity on to power the circulation fans that they distributed in the apartment units. They began releasing the Vikane gas and left the site. Several hours later, a passerby called 911 after hearing a loud hissing sound coming from under the tent. A gas leak was suspected.

While the fire engines were being deployed, the building was destroyed in a spectacular explosion. Later, the fire department investigators found that the building’s main natural gas pressure regulator had failed and had been injecting gas into the tent. There were many possible ignition sources, including the still-energized Vikane circulating fans and refrigerator thermostats.

The local gas utility company hired Intertek to investigate. First, we determined that the fumigator had erred in including the regulator inside the tent. Next, we found that the fumigator had not properly shut off the gas. He was supposed to have closed the main gas valve upstream of the regulator, but instead closed the meter valves for the individual apartment units. This meant that the regulator was forced into lock-up, with full line pressure upstream. We arranged a pressure test and inspection of the regulator, with all interested parties attending. We found that the regulator’s rubber diaphragm had ruptured, probably during the lock-up condition. Follow-up work included investigating the failure modes and root cause of failure of the diaphragm.
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