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Gas Pressure Regulator Failure and Building Explosion During Fumigation

A fumigation company "tented" a termite-infested, two-story apartment building in Santa Clara, California. 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. The fumigators began releasing 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. The building was destroyed in a spectacular explosion while fire engines were being deployed. Fire Department investigators later 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 APTECH to investigate. First, we determined that the fumigator had erred in including the regulator inside the tent. Second, we found that the fumigator had not properly shut off the gas. The fumigator 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.

Satish Almaula		Plant failure and root cause analysis; process and design engineering analysis; process technology development and testing; plant engineering, operations, maintenance and safety management; plant and process control system management.

Kimble Clark, Ph.D.		Natural gas and propane gas migration, failure analysis, chemical process analysis, heat transfer and thermodynamics, fuel science, industrial fires and explosions.

Richard Schreiber, P.E.		Machinery and mechanical device failure analysis, mechanical testing, combustion and heat transfer, industrial fires and explosions, gas appliances.

Geoffrey Egan, Ph.D.		Engineering mechanics, welding engineering, stress and fatigue analysis, risk analysis, nondestructive examination, project management.