Mechanical 3 - Silica Particle Sampler
Student Team: Sara Ratigan, Steve Klemp, Jacqueline Davis, James Moody
Advisor: Mike Keegan
Liaison: Art Miller
Sponsoring Organization: NIOSH
Mine workers are exposed to respiratory hazards in the form of airborne particles, including silica, which causes silicosis in exposed workers. NIOSH research to reduce silicosis in miners includes studies of the properties of mine dust particles. Collecting silica-bearing particles for analysis can be done by collecting samples onto filters for bulk analysis, but that does not assist in learning about the properties of individual particles. In order to individually characterize such airborne particles using offline methods, the particles must be collected on special substrates and viewed by electron microscopy. Methods of collecting particles onto substrates include the application of techniques such as aerodynamic impactors, gravitational settling, vapor deposition and electrostatic precipitation. Another potentially effective method for particle collection is by thermophoretic deposition, which is where particles are driven toward a collection plate via the uni-directional diffusion created by a temperature gradient. This approach has the benefit of “gentle” collection of particles, which is less likely to alter their morphology, and also has the potential to fill the need for a more portable sampler for mining applications, especially one that is potentially “permissible” (able to be used in explosive atmospheres). A previous CEDE team developed a mechanical design for such a sampler, aimed at improving the performance of collection. The current project will entail using that design, with some modification, and package it in a way that is user friendly, mine-worthy and functional for collecting mine dust samples.
The goal of this project is to modify an existing design for a thermal-based particle sampler and incorporate it into a new design which is field-portable, user friendly and effective for use in collecting samples of particles in dusty mines, for lab analysis by electron microscopy.
The project team will study the current NIOSH design for a thermal sampler (including the work done by a previous CEDE team), and adapt the technology to the design of a battery operated, portable sampling device. Design drawings will be made and a prototype built, including an on board pump, compact heating and cooling and a removable substrate holder. The device will also include a user interface i.e. an LED screen (preferably touch screen) that communicates with the electrical/mechanical systems to allow user control of the sampling. The device will be tested using lab-generated aerosols, to insure that performance (collection efficiency) is comparable or better than previous designs. One of the issues involved in collection efficiency is obtaining a “representative” sample i.e. a sample which reflects the actual size distribution of the in-situ aerosol. To achieve this, analysis of the collected particles will be done to give a size distribution, which will then be compared to aerosol size distribution measurements conducted in parallel. The NIOSH/OMSHR-Spokane staff will provide suitable test facilities, machine shop support, and various fabrication materials. The results of this research will enable the detailed characterization of silica particles in mines, and will also be of interest to many researchers and industrial hygienists who work in the field of aerosols and airborne contaminants
Project Management and Communication Expectations: