Combustion factor/combustion behavior, burn rate

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Combustion factor/combustion behavior, burn rate

If substances in powder form are used in a production plant, it is essential that these substances be tested with respect to their burning and explosion behavior.

An important parameter here is the combustion factor. It is one measurement of how a stored dust ignites and behaves after ignition.

The combustion behavior often is also of interest at higher temperatures, such as in drying processes. The combustion factor can therefore also be determined at an increased temperature of 100 °C, as there are often significant differences in the combustion behavior here.

If the test substance melts and, due to melting, does not burn, the test is conducted in a mixture with 20% diatomaceous earth by weight. The test examines whether product accumulations in porous materials spontaneously combust.

Combustion factor Description Example
1 No ignition Table salt
2 Brief ignition and rapid extinguishing Tartaric acid
3 Local burning or smoldering with only slight spreading Lactose
4 Smoldering without sparks (smoldering fire) or 
slow decomposition without flames Tobacco
5 Spread of open fire or burning with flying sparks Sulfur
6 Flash fire or rapid decomposition without flames Gunpowder

Combustion behavior is not only of interest in terms of the plant safety concept, however, but also for the classification of solid goods as defined by the transport law, GHS or CLP Regulation. Classification for the transportation of solid substances with regard to their combustion behavior is determined with the help of the burn rate (UN Test N.1).

The combustion factor can also provide valuable information here as well. If, for example, a combustion factor of BZ 1 to BZ 3 is determined, a self-actuating spread of fire by the test substance is not postulated. Accordingly, test efforts to determine the burn rate (UN Test N.1) can be reduced.
If we can assist you with a similar issue, please contact us. Our experts will be happy to help you.

Sources
UN Transportation Directive:
UN Recommendations on the Transport of Dangerous Goods: Manual of Tests and Criteria, Rev. 5 (2009) and UN-Model Regulations, Rev. 19 (2015)

Regulation (EC) 440/2008 establishing test methods according to Regulation (EC) 1907/2006 (REACH)

VDI 2263, Sheet 1: “Test methods for the determination of the safety characteristic of dusts.”