In-Depth Survey Report: Control Technology for Falling Solids at Cincinnati Paint and Varnish, Cincinnati, Ohio

摘要

A visit was made to the Cincinnati Paint and Varnish Company, Cincinnati, Ohio, to determine the effectiveness of control measures used to contain dust generated during the manufacturing of custom coatings. Dust arose when 50 pound bags of different powdered materials, titanium-dioxide (1343677), talc (14807966), and crystalline silica (7631869), were emptied into 600 gallon mixing tanks by a worker. The worker slit the bags with a knife, lifted the bag, poured the contents into the mixer, and returned the empty bags to the floor. Exterior surfaces of the bags were dusty; handling them released some dust into the atmosphere. A slot hood was used to capture dust generated during the operation. Air velocity toward th slot hood along the lip of the tank where the bags were emptied ranged from 50 to 100 feet per minute. The total dust concentrations determined for crystalline silica during this operation averaged 3.0mg/cum. During a revisit to the site this worker's exposure was below 0.15mg/cum for a time weighted average of less than 0.004 mg/cum. The difference in liquid level in the tank at the time each powdered ingredient was added may have significantly affected the amount of dust released. Measurements of the actual process indicated that the silica had to fall almost 1 meter before reaching any liquid in the mixing tank whereas the talc had to fall only 25 centimeters.