A numerical and experimental investigation of crystalline silica exposure control during tuck-pointing.
Bennett-J; Echt-A; Heitbrink-W
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California. Fairfax, VA: American Industrial Hygiene Association, 2002 Jun; :100
Tuck-pointing occurs on a scaffold, which limits the size and power of the LEV system. Thus, the goal of this study was to reduce the flowrate necessary for exposure control. Control addresses flow induced by the rotating grinding wheel, flow induced by the mortar particle stream, and particle momentum. Computational fluid dynamic (CFD) simulation of the grinder, supported by some experimental measurements, showed the relative importance of these factors through varying parameters and tracking particles. A simulation with the grinding wheel in a gap between the bricks, but with no particles, induced an airflow of 7.14 cfm out of the shroud exhaust, 6.5% less than the experimental measurement. With no gap the induced airflow was -0.461 cfm (0.461 into the exhaust take-off). However, when a stream of 10 microm particles was launched from the grinding wheel edge, the simulations with and without the gap had nearly identical induced flow rates, 10.8 and 10.9 cfm. Experiments and simulations indicated that between 80 and 100 cfm was required for good control of silica exposure, making induced flows relatively unimportant. In the simulations angle of particle launch affected whether a particle was captured. Stopping the particle stream through collision greatly reduced the required flow rate. This is difficult in practice because the gaps between the shroud and the brick and between bricks create escape paths.
Respiratory-system-disorders; Respirable-dust; Workers; Silica-dusts; Dust-particles; Dusts; Particulate-dust; Particulates; Masons
Work Environment And Workforce; Research Tools and Approaches; Exposure Assessment Methods; Control Technology & Personal Protective Equipment
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California