Testing Your Dust
By Jason Reason, CIH, CSP, CHMM
Combustible Dust Consultant – Lewellyn Technology
Almost every industry in the United States manufactures, processes, conveys, packages, handles, and/or generates combustible dusts. Combustible dusts include organic materials (flour, sugar, grain, wood, etc.), as well as inorganic materials (metals, plastics, rubber, etc.). To adequately identify and assess the hazards posed by combustible dusts, it is required to test each dust or powder to determine its physical properties (i.e. combustibility). Specific tests may also be required to effectively assess and select the appropriate explosion protection or prevention method for a specific enclosure (dust collectors, dryers, bins, etc.)
There are many tests available that determine specific properties of a combustible dust. Often, employers tend to “over-test” their dust in terms of performing unnecessary tests and testing too many samples. Thus, prior to performing any tests, a detailed sampling strategy should be developed to determine where dust samples should be collected and what types of tests should be performed on the dust samples. This sampling strategy will not only ensure that the physical properties of the dust(s) is/are adequately characterized, but it will also reduce unnecessary capital expenditures because only the minimum amount of samples are analyzed and the minimum amount of tests are performed.
Every dust or powder that is suspected of being classified as a combustible dust must be tested to determine its Kst, Pmax, and particle size. Even dusts and powders (coal, wood, etc.) that are known to be combustible must be tested to determine their Kst, Pmax, and particle size. The Kst and Pmax values of the specific combustible dust are required when designing explosion protection and prevention systems (e.g. deflagration venting, explosion suppression systems, etc.). If these values are unknown (including using reference data), the explosion protection and prevention systems may not be designed correctly, which could lead to catastrophic failure of the enclosure or process equipment (dust collector, dryer, etc.).
After all of the required physical properties of the combustible dust have been determined, the employer should use these properties to effectively assess and mitigate all of the potential hazards associated with the combustible dust(s). The most effective way this can be done is through a Process Hazard Analysis (PHA). This can also be done through a thorough audit that assesses all of the potential combustible dust hazards located throughout the facility.