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Re: Fire investigation for forensic engineers, Jan 14 in Phoenix
Posted by: Mark Goodson (IP Logged)
Date: October 08, 2017 02:53PM
An interesting blog, with several factors left out... It depends upon what the engineer was retained to do...
Some / many engineers work fires, but do not per se do O&C work. The book / guide makes it very clear as to the fact that it is NOT an engineering text. I personally submitted that back in about 2011, as I recall. If I am analyzing an electrical system, there is NO PART of 921 I am going to refer to on how an electrical system works.
Years ago, someone tried to challenge my opinion that a notch in a wire overheated and the wire acted like a fuse and parted. 921 was cited at the Daubert hearing - it says notched wires do not overheat. Well, I was about to take a screwing over 921. How dare I disagree!!! In fact, a notched wire can and does overheat - and they fail at the notch. That is in fact how a fuse is built. When you read the 921 book, it fails to state that the lack of overheating occurs at listed current for the wire - 20 amperes for a 12 AWG conductor. I was dealing with an overloaded circuit carrying about 120 amps.
John Lentini's point is well taken. Engineers like to use sound engineering judgment in an analysis. That is fine and it works well IF the engineer is proficient. It is a disaster if the engineer does not understand the concepts involved.
Lastly, someone made the comment that some professionals do not accept 921. That is once again partially true. If doing O&C, there is acceptance. If carrying out an engineering analysis, then it is probably not accepted.
Some / many engineers work fires, but do not per se do O&C work. The book / guide makes it very clear as to the fact that it is NOT an engineering text. I personally submitted that back in about 2011, as I recall. If I am analyzing an electrical system, there is NO PART of 921 I am going to refer to on how an electrical system works.
Years ago, someone tried to challenge my opinion that a notch in a wire overheated and the wire acted like a fuse and parted. 921 was cited at the Daubert hearing - it says notched wires do not overheat. Well, I was about to take a screwing over 921. How dare I disagree!!! In fact, a notched wire can and does overheat - and they fail at the notch. That is in fact how a fuse is built. When you read the 921 book, it fails to state that the lack of overheating occurs at listed current for the wire - 20 amperes for a 12 AWG conductor. I was dealing with an overloaded circuit carrying about 120 amps.
John Lentini's point is well taken. Engineers like to use sound engineering judgment in an analysis. That is fine and it works well IF the engineer is proficient. It is a disaster if the engineer does not understand the concepts involved.
Lastly, someone made the comment that some professionals do not accept 921. That is once again partially true. If doing O&C, there is acceptance. If carrying out an engineering analysis, then it is probably not accepted.
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