A test protocol is described which evaluates the self-heating potential of liquid materials, notablywood stains. The protocol employs 25 cotton rags, each have a dry weight of 25 – 30 grams coated withan equal weight of the test material, arranged in a hemispherical pile and placed on a raised, insulatedbase. This arrangement approximates the thermal characteristics of a sphere1. The protocol is conductedwithin a vented enclosure at approximately 20?C. Thermocouples placed at the center of the rag balls thatare in contact with the insulated base provide the time history of the temperature distribution within thebase layer of the 25-rag pile. The applicable theory governing the thermal characteristics of the 25-ragpile and the self-heating process are discussed2. The results of experiments employing the protocol areshown for a variety of vegetable-based oils. Both sub-critical and super-critical (i.e. self-heating toignition) cases are demonstrated.This self-heating protocol has been useful as a means of judging the risk associated with a given product’spropensity for self-heating to ignition. The 25-rag pile represents a practical conservative case forthermal characteristics and thus is useful for many consumer and commercial applications. Materials thatshow critical, or near critical behavior, are discouraged from entering the marketplace. This protocol hasalso proven useful in forensic fire reconstructions3, where a specific material is suspected of self-heatingto ignition.
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