Air cleaning performance of a new environmentally controlled primary crusher operator booth

Abstract

The National Institute for Occupational Safety and Health (NIOSH) cooperated with 3M Company in the design and testing of a new environmentally controlled primary crusher operator booth at the company’s Wausau granite quarry near Wausau, WI. This quarry had an older crusher booth without a central heating, ventilation and air conditioning (HVAC) system, and without an air filtration and pressurization system. A new replacement operator booth was designed and installed by 3M based on design considerations from past NIOSH research on enclosed cab filtration systems. NIOSH conducted pre-testing of the old booth and post-testing of the new booth to assess the new filtration and pressurization system’s effectiveness in controlling airborne dusts and particulates. The booth’s dust and particulate control effectiveness is described by its protection factor, expressed as a ratio of the outside to inside concentrations measured during testing. Results indicate that the old booth provided negligible airborne respirable dust protection and low particulate protection from the outside environment. The newly installed booth provided average respirable dust protection factors from 2 to 25 over five shifts of dust sampling with occasional worker ingress and egress from the booth, allowing some unfiltered contaminants to enter the enclosure. Shorter-term particle count testing outside and inside the booth under near-steady-state conditions, with no workers entering or exiting the booth, resulted in protection factors from 35 to 127 on 0.3- to 1.0-μm respirable size particulates under various HVAC airflow operating conditions.

Dust control handbook for industrial minerals mining and processing. Second edition.

“…The advantage of particle counting as compared to gravimetric sampling for measuring an enclosure's filtration system performance is that a large number of smaller particles in the submicron size range (< 1 micron) are available at lower respirable dust mass concentrations, providing a better test medium for comparative performance testing of environmental enclosures NIOSH 2008a;Organiscak et al 2013;Organiscak et al 2016]. Figure 10.19, right, shows an example of a six-channel particle counting instrument that can detect six particle size ranges of 0.3-0.5 microns, 0.5-0.7 microns, 0.7-1.0 microns, 1.0-3.0 microns, 3.0-5.0 microns, and > 5.0 microns.…”

“…Since this sampling method introduces individual instrumental error biases into the particle counting measurements, it is recommended that the instruments be rotated between the sampling locations an equal number of times during testing to average out these biases. The two-instrument methodology was initially specified for mobile testing of a cab by ASAE and was primarily used by NIOSH in laboratory and field studies [ASAE 1997;Heitbrink et al 1998;Hall et al 2002;Heitbrink et al 2003;NIOSH 2008a;Organiscak and Cecala 2008;Cecala et al 2012;Organiscak et al 2013;Cecala et al 2016;Organiscak et al 2016].…”

“…When performing this type of enclosure testing, particle concentrations should be continuously measured to detect when they reach their lowest and most stable interior levels for comparison with the outside concentrations for the same time period. In NIOSH laboratory and field testing, researchers typically conducted enclosure testing for 45 minutes when using only an intake filter and for 30 minutes when using both an intake filter and a recirculation filter [NIOSH 2008a;Organiscak and Cecala 2008;Cecala et al 2012;Organiscak et al 2013;Cecala et al 2016;Organiscak et al 2016]. The most stable data and the last 15 minutes of data for these test periods were averaged and were used for the protection factor calculations of each test discussed above.…”

Improving protection against respirable dust at an underground crusher booth

“…Designed and installed correctly, enclosed cabs, operator booths and control rooms offer mine workers protection from noise and physical hazards, such as flying rock and debris, as well as a more comfortable environment in regards to temperature and humidity (Organiscak et al, 2016). While it is easy to quantify the operation of a cab’s air-conditioning unit by measuring the temperature, or observe whether the cab offers protection from flying debris, it is somewhat more difficult to quantify its performance in reducing respirable dust hazards.…”