Date of Graduation
Honors Research Project
Dr. George Chase
Dr. Gang Cheng
The purpose of this experiment is to compare the efficiency of four different filter media with two different drainage channel materials when filtering out aerosolized oil. The filter media include 2 micron stainless steel fibers, 6.5 micron stainless steel fibers, 2 micron woven glass fibers, and 6 micron woven glass fibers. The drainage channel materials are 500 micron Teflon (PTFE) and nylon mesh.
One major application that this research is targeted towards is air compressors. Air compressors use lubricating oil to minimize wear and corrosion. During operation some of this lubricating oil is aerosolized into the outgoing air stream. Inhalation of the aerosolized lubricating oil could potentially result in concentrations in the body high enough to cause respiratory irritation and other effects . Filtering the oil out, allowing it to drain and recirculate back to the compressor will also help to reduce the oil loss in the compressor, reducing the amount of preventative maintenance required.
Another significant aspect of this project is to test alternative filter media. Recent awareness of potential side effects man made mineral fibers (MMMF) which contain silica have raised concerns about the production and usage of woven fiberglass filter media. This experiment tests woven stainless steel filter media which could be a potential alternative to fiberglass should restrictions be put into place on the production and usage of fiberglass filter media.
The experiment was conducted using the experimental setup in ASEC 81 C. The setup utilizes compressed air to aerosolize lubricating oil and pass it through the filter media. A scanning mobility particle sizer which uses an electrode to separate droplets of particular size and a condensation particle counter were used to detect the change in concentration of droplets across the filter. The pressure drop across the filter was also recorded. These values were used to generate quantities called the filter efficiency and filtration index. Filter efficiency is dependent on the concentration gradient and the filtration index incorporates the filter efficiency as well as pressure drop across the filter.
At smaller fiber diameters the change in drainage material did not significantly affect the efficiency or filtration index. The exception to this is the nylon run. One potential explanation for this is the highly wetting nature of nylon towards oil . As these were the first set of experiments run, it may be better to attribute these results to inexperience operating the experiment.
At larger fiber diameters the change in drainage material resulted in a more dramatic shift in efficiency, pressure drop and filtration index. The nylon as previously stated has a higher wettability than the Teflon. It would appear from the data that the lower wettability of Teflon allowed the filter media to drain more easily and achieve higher efficiencies with a lower pressure drop.
Comparing small fiber sizes to large fiber sizes it was seen that the efficiencies of the small fibers were roughly comparable for stainless steel, but with a much higher pressure drop and lower filtration index with the 2 micron fibers. This is due to the capillary forces that were discussed previously which causes the filtration media to compress, decreasing the porosity and increasing the pressure drop. The efficiencies of the 2 micron glass fibers were higher than the 6 micron fibers, but with an increased pressure drop and lower filtration index due to the smaller pore size.
With regards to this project further trials are recommended using greater variations in filter material, drainage material, and different dimensions of both. This trial is largely limited due to the amount of time it takes to run each experiment which was typically a little over four hours.
Boldon, Corey A., "Filtration of Aerosolized Oils with Layered Filter Media and Drainage Channels" (2015). Honors Research Projects. 147.