The search for a reliable method of testing commercial kitchen grease filters turned into a multi-year quest. Two different universities working on ASHRAE grants of approximately $100,000 each failed to effectively develop a repeatable process of testing individual grease filters.
While progress was made in each of the first two attempts, those attempts did not achieve the ultimate goal of developing a repeatable test method. ASHRAE’s TC 5.10 Kitchen Ventilation technical committee was not to be denied in their quest.
After the second unsuccessful attempt, Don Fisher rallied members of the manufacturing community that build hoods and filters to fund yet a third attempt. Many of those manufacturers are volunteer members of ASHRAE’s TC 5.10 for Kitchen Ventilation. TC stands for Technical Committee for those of you easily confused by the ever growing and sometimes overwhelming use of acronyms.
These members pooled their ideas, expertise and money to take a fresh approach. In a reasonably short period of time using the previous research gathered, they developed an idea of how to mechanically produce repeatable and consistent grease molecules. The challenge was to reproduce and emulate varying grease molecule sizes as they appear in the normal cooking processes.
They then hired the University of Minnesota’s Engineering Department to conduct independent third party testing of the new test equipment. Professor Tom Kuehn, P.E. chaired the research and development. After the university confirmed the accuracy of the new test equipment, it was submitted and accepted by ASTM. Information can be accessed at www.astm.org. Copy the standard number ASTM F2519-05 into the search field on the ASTM home page.
In the past, food tests were conducted using hundreds of pounds of products to test filter efficiency. It was time consuming and expensive. Moreover, it was thought that the consistency of products being tested often skewed the results.
For years we were convinced that baffle type filters introduced in the 60’s were far more effective than mesh filters. This belief was based on Navy test data established in the 1940’s. What we never knew until recently was that the Navy test was based on particles 10 microns (>10 microns) and larger.
Normal cooking processes generate grease particles from as small as less than 1 micron (< 1 micron) on up to as large as 40 microns (~ 40 microns). A greater amount of foodservice grease molecules generated by typical cooking, grilling, broiling, etc., are generally in the 1 to 10 micron size. That range is where the industry has focused their research. Further retesting is indicating efficiency ratings for the typical baffle filter to be in the 30% range. That is a far cry from the 90% plus efficiency ratings we as designers and salespeople erroneously believed for some four decades.
Two newer styles have been introduced over the last few years. One style is called a centrifugal filter. Air enters the filter at the top and bottom only. Then centrifugal force spins the air within the chambers until it exists at slots at the rear. This filter can approach 70% to 90% efficiency ratings. Efficiency is based on air speed. Click on the following links for more information. www.haltoncompany.com; www.greenheck.com
Both the Halton Company and Greenheck market this style of filter. Halton was the developer of this style filter in the late 1970’s.
Another style produced by Greenheck combines the centrifugal filter with a second stage packed with beads that attract grease molecules. The two parts easily separate for cleaning in a commercial dishwasher. This dual or multi-stage filter requires a higher static pressure but can achieve results up to 99%.
A second company named Captrate also produces a dual stage filter that is said to have similar efficiency ratings. Captrate is in the process of having their filter tested by an independent testing agency to officially confirm their internal results. Go to www.captrate.com
All three companies are sponsors of UP YOUR STACK®.com. |
