The Bureau of Mines has evaluated a number of ventilation systems for potential application in lowering the dust exposure of workers who stack bags of mineral product material in enclosed vehicles. Workers who stack these bags in enclosed vehicles usually have the highest dust exposure among all workers in processing plants. This is because dust liberated while the vehicle is being loaded has no means of exiting the vehicle or being diluted with fresh air so that dust concentrations increase to substantial levels. Laboratory- scale testing was performed in a railcar to compare the effectiveness of a number of different ventilation systems in reducing the bag stacker's dust exposure. The most effective system was taken into the field to optimize its performance. The final and recommended system exhausted about 2,000 cfm through 10-ft-long, 12- in-diam fiberglass tubing located 3.5 Ft past the slinger at a 6.5- Ft height so as to not interfere with the bag stacker's job. A 6-in- diam tube exhausted approximately 300 cfm at the snake conveyor- slinger transfer point to capture the dust generated there. With this system, dust reductions in and around the bag stacker ranged between 65 and 95 pct when loading both 50- and 100-lb bags of product into railcars and trailer trucks.

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