Many modern industrial operations create dust as either a by-product or an end product. In certain conditions, some of these dusts can release hazardous amounts of energy when ignited. But, questions then arise as to which dusts are susceptible, what can be done to reduce the risk of a dust explosion, and why do they occur? It is the purpose of this presentation to answer these questions. This knowledge will enable a systematic method of hazard assessment and mitigation to provide the maximum protection of the employees and assets within the organization.
It should be the intent of every Safety Professional, Manager, Technical Engineer, and Operator to work diligently to prevent these incidents of explosions from happening. One of the best preventatives is to understand how they occur and then put irreversible corrective actions in place to keep them from occurring. The pages that follow offer a primer on the conditions leading to and the prevention of dust explosions in industrial settings.
One of the first recorded dust explosions occurred in Turin Italy in 1785 at a flour mill. Since that time dust explosion events have continued to cause devastation, destruction, and death. In a study completed by the National Fire Protection Association in 1957, 1123 dust explosions occurred between 1900 and 1956 in the United States, across many industries (NFPA, 1957). Figure 1 illustrates the scale of destruction and potential danger from dust explosions.
In the early 1900s coal-mining incidents occurred in Monongah, West Virginia, and in Darr, Pennsylvania, with a combined total of over 600 deaths. These two explosions were so devastating because of the number of people who lost their lives that the United States Government began an explosive testing program under the Federal Geological Survey. The laboratory was later transferred to the Bureau of Mines in the U.S. Department of Interior. Testing was conducted on a laboratory scale and in a full-scale mine trial in Pennsylvania. The results from these tests were helpful to the mining industry by reducing the number of mine dust explosion events. Testing continued in the United States through the 1940's and 50's under the Bureau of Mines and the Department of Agriculture (Cashdollar and Hertzberg, 1987). During this time, researchers at the Bureau of Mines developed a cylindrical tube dust explosion apparatus with the capability of testing dusts for explosive potential. The Hartmann Test Apparatus, as it was called, has been used by the Bureau of Mines to study many different dusts over the past century (see Figure 2). This machine, which measures the rate of pressure rise and the maximum pressure resulting in an explosion, was used to develop much of the explosibility data found in most of the reference books of the 1950's, 60's and 70's. Continued research identified and corrected flaws in the design of the Hartmann tube which, in general, tends to underestimate key measures of dust deflagration energy.
