A CRITICAL EVALUATION OF EXPLOSIBLE DUST TESTING METHODS: PART II

作者：Ganesan B^*; Parnell C B Jr; McGee R O; Faulkner W B

来源：Applied Engineering in Agriculture, 2015, 31(2): 203-209.

DOI：10.13031/aea.31.10603

• ASTM explosible dust test method
• Combustible dust
• Combustion
• Deflagration
• Detonations
• Explosible dusts
• Minimum explosible concentration
• Particle density
• Particle size distribution
• Primary dust explosion

The Center for Agricultural Air Quality Engineering and Science (CAAQES) tested cotton gin dust (CGD) and reported that it was not explosible. A commercial laboratory tested the same CGD and determined that CGD was explosible based on American Society for Testing and Materials (ASTM). A detailed study of the two protocols by CAAQES determined that ASTM protocol for classifying a dust explosible was flawed. As a consequence, non-explosible dusts such as CGD are being classified as explosible. CAAQES personnel have developed an alternative protocol that more accurately characterizes the explosibility of dusts. The CAAQES protocol uses the criterion specified by Palmer (1973) that a dust must have a minimum explosible concentration (MEC) for the dust to be explosible. The MEC is the lowest dust concentration in which the dispersed dust cloud result in a self-propagating flame, when contacting an ignition source. The ASTM protocols consists of (1) dispersing dust in a totally enclosed 20 L chamber, (2) forcing a 10,000 J flame through the dust cloud, and (3) measuring the resulting pressure rise. If the pressure rise exceeds 1 bar (14.5 psi), the dust is explosible. There is no requirement that the dust must have a MEC to be explosible with the ASTM protocol. The CAAQES protocol for determining the MEC is to test a wide range of concentrations of dusts in a 28.2 L (1 ft(3)) plexiglas chamber with a diaphragm engineered to rupture at approximately 2 psi. A precisely measured mass of dust is placed in a crucible below the ignition source (heating coil). A 1.5 second blast of air at 40 psig is used to disperse the dust into a dust cloud. The Plexiglas chamber allows for video recordings of reactions in the chamber. Pressure sensors are installed in the CAAQES chamber to record the pressure rise due to deflagration (explosion). If a self-propagating flame results as indicated by the diaphragm bursting, the pressure vs. time (PvT), and the flame leaving the chamber, a deflagration occurred during the test and the dust is explosible. It was concluded that the current ASTM explosible testing method yields false positive results, leading to mislabel a non-explosible dust as explosible.

• 出版日期2015-3