A gas explosion severely injured a homeowner in their kitchen during morning breakfast prep. The fire marshal’s investigation concluded that a leak occurred due to a loose broiler gas tube connection on a new range installed by the homeowner the previous day. An initial lab-based inspection performed by another involved party claimed there were no tool tightening marks on some brass compression nuts and a gas tube end compressed by one of the nuts looked abnormal and was evidence of factory over-torquing.
Our Approach
After carefully reviewing the previous lab inspection work product, ESi worked closely with the manufacturer to understand the range gas tube factory installation. Pneumatic wrenches with C-shaped tool inserts were used at several assembly stations. The tool inserts engaged five of six brass compression nut hex flats and tightened the nuts to compress and seal pre-formed aluminum tube ends. The factory generated exemplar seals to the specified target torque on several connections with the same tools used to assemble the subject range. One connection was purposefully over-torqued. The connections were all determined to be leak free in factory testing.
After disassembly of the connections, these exemplars were provided to ESi for a lab-based inspection. Optical microscopic and stereomicroscopic examinations of the aluminum tube ends and brass nuts were performed. The exam results indicated that tightening witness marks on the brass nut flats varied significantly depending on the station tool and operator. The appearance of the sealed aluminum tube ends also varied in appearance despite the same applied torque and their all being leak-tight. Given the variations observed, it was not possible conclude, as alleged by the other involved party, that a connection on the subject range was not properly assembled, over-torqued and leaking. In short, testing trumped speculation.
Instead, a fire cause and origin investigator determined that the gas leak causing the explosion was due to the homeowner’s improper use of Teflon tape to install the range to the home gas supply.
Services Utilized
Expertise Utilized
The Outcome
Prior to trial in this litigation matter, an undisclosed settlement was reached. This project demonstrated the beneficial interaction between ESi and its client to provide factory exemplar testing that importantly informed opinions that no manufacturing defects contributed to this unfortunate accident.
