Pyrolytic Severity Test

If an unstable substance or self-reactive substance in a tank or drum meets with a fire during storage or transportation, it begins to decompose with the heat conducted through the container. When the thermal decomposition is severe, an explosion or bursting may occur, causing damage. 

The Keonen test 3 7i, the Netherlands method 37 4 6 and the American method 3 7 4 7 for pressure vessel testing are known as test methods for evaluating fire dangers. For conventional methods for pressure vessel testing, refer to the previous book 1) where they are described in detail. 

In Japan, the Fire Services Law(FSL) has recently been revised 1011 and a pressure vessel test has been newly stipulated as the test method for determining the pyrolytic severity of Dangerous Goods- Class 5 Self—Reactive Substances—set forth in the FPL 31 . In this section a description will be given of the procedure for pressure 

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The purpose of this test is to evaluate the pyrolytic severity of solid or liquid substances. For this purpose, the article under test is heated in a pressure vessel to examine if a bursting plate is ruptured at a probability of 50% when a prescribed orifice is used. 

Despite data on the conventional test for pressure vessels showing much variation, the test is considered effective in determining the pyrolytic severity of unstable substances including organic peroxides. 

Heat load tests were performed on isotropic graphites, pyrolytic coated graphites with a coating thickness of 5-30 pm, and a C/C composite (felt type). The sample sizes were 25 X 25 X 3-10 mm, the beam diameter was 12.7 mm, and the heat load duration was 5 s. The results are shown in Table 6. Severe erosion was observed on the surface of most specimens. The erosion mechanism may be vaporization and ejection of small carbon particles from the surface due to thermal stress. The incubation time to erosion increased in all cases with sample thickness. This means that the erosion process is controlled by the surface temperature, because increasing rate of the surface temperature decreases with increasing of thickness. 

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