Fire/Arson Investigations : Fire/Arson Investigations
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Re: Ignition temperature of wood
Posted by: dcarpenter (IP Logged)
Date: October 08, 2020 11:56AM
It would appear that there is antidotal evidence to formulate the hypothesis that dimensional lumber may self-heat at temperatures that are less than would be estimated by theory or by experimental testing.
There is evidence that is consistent with this theory and testing for exposure temperatures on the order of 150 degrees C with an open configuration with heat losses to the environment.
Thus, it appears that the hypothesis for lower temperatures must be augmented to include a variable or variables that are not included in the theory or the testing. My point is that the basic theory of self-heating makes some simplifying assumptions that may not be appropriate based on the empirical evidence. That is, heat losses at the surface of the wood are lost and not able to contribute to the continued self-heating process. The empirical data suggests that this takes place inside wood enclosures. This is not the same scenario dimensional lumber in the "open" or non-insulated. Thus, our theory and experimental testing can only take us so far at the moment. Thus, more work needs to be done to develop data to test hypotheses and develop a theory to include the other relevant variables and predict the specific conditions.
An alternative hypothesis is that the temperature of the pipe was not 77 degrees C. Although rare, you can get a failure prior to the incident that "corrects itself" or is corrected by someone else after the fact. For the same thermal input, a low water condition can create pressurized steam in the tank that could elevate the pipe temperature to well-above the 77 degrees C reported and measured after the test. If the tank is filled at the time of the measurement, it may not produce the same exposure temperature was experienced at the time of the incident.
Can we use the available scientific literature and experimental testing to predict of self-heating can occur? Like a lot of phenomenon where we have not saturated the science, "it depends." Our determinations are only was reliable as the available science since science is a compilation of reliable knowledge.
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
There is evidence that is consistent with this theory and testing for exposure temperatures on the order of 150 degrees C with an open configuration with heat losses to the environment.
Thus, it appears that the hypothesis for lower temperatures must be augmented to include a variable or variables that are not included in the theory or the testing. My point is that the basic theory of self-heating makes some simplifying assumptions that may not be appropriate based on the empirical evidence. That is, heat losses at the surface of the wood are lost and not able to contribute to the continued self-heating process. The empirical data suggests that this takes place inside wood enclosures. This is not the same scenario dimensional lumber in the "open" or non-insulated. Thus, our theory and experimental testing can only take us so far at the moment. Thus, more work needs to be done to develop data to test hypotheses and develop a theory to include the other relevant variables and predict the specific conditions.
An alternative hypothesis is that the temperature of the pipe was not 77 degrees C. Although rare, you can get a failure prior to the incident that "corrects itself" or is corrected by someone else after the fact. For the same thermal input, a low water condition can create pressurized steam in the tank that could elevate the pipe temperature to well-above the 77 degrees C reported and measured after the test. If the tank is filled at the time of the measurement, it may not produce the same exposure temperature was experienced at the time of the incident.
Can we use the available scientific literature and experimental testing to predict of self-heating can occur? Like a lot of phenomenon where we have not saturated the science, "it depends." Our determinations are only was reliable as the available science since science is a compilation of reliable knowledge.
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
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