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Control technology for ready-mix truck drum cleaning at Hilltop Basic Resources, Cincinnati, Ohio.

Almaguer D; Shulman S; Echt A
Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 247-19, 2001 May; :1-21
A NIOSH research study was conducted to evaluate worker exposures to respirable crystalline silica during interior cleaning of ready-mix concrete truck drums. The cleaning of ready-mix drum interiors becomes necessary as the drum interior becomes coated with hardened concrete. During truck maintenance activities, workers are required to enter the interior of the cement-mixer drum (a confined space) to remove the hardened concrete. The workers utilize a jackhammer to break the hardened concrete. The study was conducted at a ready-mix concrete plant with a fleet of 27 ready-mix trucks. The drum cleaning operation is conducted on an annual basis, during the winter construction slowdown. For this study, NIOSH personnel developed and field tested engineering controls designed to capture or suppress silica-containing dusts that are generated during drum cleaning operations, thereby reducing employee exposures. The controls developed included a local exhaust ventilation (LEV) system and water-spray dust suppressant controls for the jackhammer, and a general exhaust ventilation (GEV) system for removal of dust from the mixing drum. During this study, only the LEV and GEV systems were field tested. The water-spray system was not tested due to reluctance and objections of the company and plant personnel to using water, which they felt may freeze or result in a slipping hazard. The LEV system was designed to be attached to the jackhammer to remove the generated dust at the jackhammer blade. The GEV system was designed to fit over the drum discharge outlet and remove suspended dust from the drum interior. Four control combinations (no controls, LEV, GEV, and LEV/GEV combined) were evaluated to determine how effective the two control designs, and their combination, were at reducing worker exposures during concrete removal operations. To evaluate the effectiveness of the designed controls, personal breathing zone air samples were collected on employees entering the drum interior. Additionally, video exposure monitoring was conducted utilizing a real time monitor which was synchronized with a video recorder.
Respirable-dust; Silica-dusts; Ventilation; Ventilation-equipment; Ventilation-systems; Concretes; Construction; Construction-equipment; Construction-workers; Confined-spaces; Control-equipment; Control-technology; Environmental-control-equipment; Exhaust-systems; Exhaust-ventilation; Dust-sampling; Equipment-design; Jack-hammers; Engineering-controls; Equipment-reliability; Testing-equipment; Exposure-levels; Trucking; Maintenance-workers; Region-5
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Document Type
Field Studies; Control Technology
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NIOSH Division
Priority Area
Disease and Injury; Asthma and Chronic Obstructive Pulmonary Disease; Research Tools and Approaches; Control Technology & Personal Protective Equipment
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National Institute for Occupational Safety and Health
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division