In-Depth Survey Report: Control Technology for Dowel Drilling in Concrete.

摘要

This study evaluated the ability of a commercially-available dust-control system to reduce respirable dust emissions during dowel drilling. Dowel drilling is a task performed during new concrete runway and highway construction (e.g., when a lane is added) or during full-depth repair of concrete pavement to provide load transfer across transverse pavement joints. Dowel drilling machines typically contain one or more pneumatic or hydraulic percussion drills aligned in parallel in a frame that acts to control drill alignment and prevent wandering. The dust control evaluated in this report included a close-capture hood surrounding each of the steels and bits at the work surface, a length of corrugated flexible hose connected to each hood, and a dust collector at the back of the dowel drill unit. Compared with the use of no dust control during dowel drilling in concrete, the dust-control system significantly (p less than 0.0001) reduced geometric mean respirable dust emissions by 93 percent to 96 percent when measured with filter samples. Arithmetic mean respirable dust emissions measured on filters were significantly (p less than 0.0001) reduced 92 percent to 96 percent by the use of the dust control system. The use of the dust control also significantly reduced respirable dust emissions (p less than 0.0001) by 87 percent to 94 percent when measured with a nephelometer. The different measurement techniques probably account for the disparity in results obtained with filter samples and the nephelometers. The dust-control system significantly (p less than 0.0001) reduced geometric mean respirable quartz emissions by 92 percent to 96 percent when measured with filter samples and significantly (p less than 0.0001) reduced arithmetic mean respirable quartz emissions measured on filters by 90 percent to 96 percent. The measurements were conducted in a tent to exclude diesel exhaust particulate emitted by the compressor used to power the dowel-pin drill and isolate the drill from the effects of wind and weather during the tests. The use of this technique means that it would not be appropriate to compare the results to any exposure indices. Recommendations are offered at the end of the report to improve the system. These include recommending that the manufacturer consider installing a pressure gauge across the filter in the dust collector to provide the drill operator with information needed to determine when to clean or change the filter. The manufacturer should also consider installing static pressure taps near the duct connection to each hood that can be connected to vacuum gauges on the operator's instrument panel. Monitoring hood static pressure would indicate to the operator when the dust collection system was not performing as designed.