Rock Products

OCT 2014

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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T his article describes the latest ad‐ vancements in technology to im‐ prove how mine operators can investigate and assess the respirable dust exposure of their workers. Re‐ cently, Unimin Corp. and the National Institute for Occupational Safety and Health (NIOSH) developed the Helmet‐ CAM technology, a dust exposure as‐ sessment tool designed specifically for the mining industry. This assessment technique is per‐ formed by having a miner wear a small video recorder on his or her hardhat along with a real‐time aerosol monitor that is housed in a backpack, on a safety belt, or safety vest and records the individual's respirable dust exposure at two‐second inter‐ vals. After a miner performs his or her job while wearing the unit, the video and dust exposure data files are downloaded to a computer and then merged together using a NIOSH‐de‐ veloped computer software program called EVADE (Enhanced Video Analy‐ sis of Dust Exposure). By providing synchronized playback of the merged video footage and logged dust exposure data, the EVADE soft‐ ware allows for the assessment and identification of key work areas and processes, as well as work tasks that significantly impact a worker's per‐ sonal respirable dust exposure. The Helmet‐CAM respirable dust expo‐ sure assessment technology is now available for use and allows mining op‐ erators to quickly and efficiently iden‐ tify work tasks, areas and practices contributing to respirable dust expo‐ sure, as well as to evaluate the effec‐ tiveness of implemented control techniques aimed at lowering worker's exposure to respirable dust. Mining companies wishing to use this new dust exposure assessment tech‐ nology can purchase a commercially available video camera and a direct‐ reading aerosol monitor to obtain the necessary data. NIOSH has recently released a beta version of the EVADE software and user manual, which can be downloaded from the NIOSH website at: www.cdc.gov/niosh/min‐ ing/Works/coversheet1867.html. Background on Respirable Dust Sampling The exposure of miners to respirable dust, especially respirable dust con‐ taining crystalline silica, has been an area of concern for decades, and the adoption of permissible exposure lim‐ its upon the creation of the 1977 Fed‐ eral Mine Safety & Health Act only provided additional reasons to under‐ stand exposures and their sources. These personal dust sampling trains are composed of a 10‐mm Dorr‐Oliver cyclone, sampling pump calibrated to 1.7 liters per minute (lpm), 37‐mm polyvinyl chloride (PVC) filter, sampling assembly, and a piece of tygon tubing. The 10‐mm cyclone has a 50 percent cut‐point at four microns which is in‐ tended to replicate the respirable por‐ tion of dust that may reach the gas exchange region of a worker's lungs. It is this respirable dust – the dust that reaches the gas exchange region of the lungs – that can inflict injury to the lung tissue and may negatively impact pul‐ monary function. To perform personal sampling with the Dorr‐Oliver cyclone, a 37‐mm PVC filter is attached to the 10‐mm cyclone via a stainless steel assembly positioned in the worker's breathing zone. A sam‐ pling pump calibrated to 1.7 lpm draws dust‐laden air through the cyclone. The respirable portion of dust is deposited via impaction on the 37‐mm PVC filter and the non‐respirable fraction (larger sized) of dust falls into a grit pot located at the bottom of the cyclone. The sampling pump is normally at‐ tached to the miner's belt and a short section of flexible tygon tubing is then used to connect the sampling pump to the sampling assembly. The only signif‐ icant change over the past few decades DUST MONITORING ROCK products • OCTOBER 2014 www.rockproducts.com 26 Here Comes The Helmet-CAM By Andrew B. Cecala and Andrew D. O'Brien A Recent Advance In Technology Can Improve How Mine Operators Investigate And Assess Respirable Dust. Figure 1 - Helmet-CAM setup showing video camera lens on a miner's hardhat and 10-mm cyclone on backpack shoulder strap (left), and video logger and pDR-1500 dust monitor in backpack (right).

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