Grain dust concentrations that exceed the minimum explosive concentration (MEC) can be ignited by an innocent spark or a terrorist action with the resulting explosion resulting in death and property destruction. Reported data indicate 106 grain dust explosions (elevators) with 16 deaths, 126 injuries and property damage of $162.8 Million (USD) in the 10-year period of 1996-2005. At present, and in spite of significant development efforts, there is no viable, field deployable monitoring device to warn the operators when the MEC is approached or exceeded. The purpose of this research is to develop a low-cost, reliable, and accurate Mass Loading Monitor (MLM) that will provide a warning signal when the minimum explosive concentration (MEC) is approached in the sensitive areas of a grain handling facility. This warning signal will allow the operators to take corrective action and avoid an explosion. OBJECTIVES: The objectives are to establish the component parts that will be incorporated into the Phase II working prototype of a field deployable "Mass Loading Monitor" (MLM). The MLM is to provide a warning signal, to the operators of a grain handling facility, when the mass loading: grams/m3 approaches the minimum explosive concentration level. Specifically, sensors that will provide the required position (x p), the velocity (d(x p)/dt) and the acceleration (d2(x p)/dt2) of the MLM piston at the measurement position and the pressure transducer that provides the pressure (p(t m)), - where tm is the designated time for the measurement - will be established in the Phase I efforts. These sensors will be installed on the Phase I prototype MLM device. A further objective is to proof-test the Phase I MLM prototype using the known dust loading conditions provided by the to-be-developed test chamber. APPROACH: The test chamber will be developed through our subcontract at Michigan State University (MSU). Known concentrations of representative grain dust material will be levitated in this chamber. An impeller will mix the air and the dust inside the enclosed chamber. The MLM device, which will be mounted on the side wall of the chamber, will ingest samples of the mixture and determine the mass loading for each sample. The average mass loading from an ensemble of samples will be used to calibrate the MLM device. Specifically, as shown in the analytical derivation of the proposal (Equation 9a) quantitative values of the piston position (x p), its velocity dx p/dt and its acceleration can be related to the density of the air-plus-dust mixture. However, the physical effects of the wall shear stress and the non-uniform exit velocity profile require that the measurable terms of (9a) be supplemented by a direct calibration as expressed in Equation (9b). Hence, the measured piston face pressure: p(t m), will be calibrated for the known mixture density values using the test chamber. Additional measurements, for the "air-only" or ambient density condition, will define the density ratio condition that will determine the calibration coefficient in Equation (9b). The mass loading value follows as shown by Equation (10) of the proposal
