2021 RETA Breeze May-June

MICROBIAL HAVEN TO SAFE HAVEN

Achieving the proper balance between supply air and exhaust air is critical to proper system operation and control. When done correctly, airflow should move from the cleanest to the least clean areas and outside air make up should be supplied to exhausted areas so as not to create negative pressure zones within the building. Because both airflow and the sources of air can be hard to control during processing conditions, it’s best to set up a hierarchy using relative pressurizations. Don’t Forget About Air Filtration Air filtration is the fourth component in the good air quality mix. Air needs to be adequately filtered to maintain air quality levels and control contaminants as directed by the QA/QC department. To determine whether your filters are acceptable, check whether pre-filters and final filters are installed on your equipment. If not, where are they missing? If so, what are the MERV ratings (see “Helpful Definitions,”page 4) of those filters? Optimizing the Room Once you’ve compiled the data from the four components outlined above, you’ll then need to determine the most likely source(s) of your temperature/ condensation issues. Is it an undersized refrigeration system? Is there too little insulation? Are doors being left open? Is there air infiltration or are cold surface temperatures causing the problems? After determining likely problem areas, you’ll want to identify what the optimal state for the room would be in terms of temperature, humidity, pressurization and filtration: • Heat and Moisture Loads. Calculate heat and moisture loads as well as the outside air requirements that the room should have based on a typical day. Room load calculations should take into consideration sensible heat and latent heat (see “Helpful Definitions,” page 4) and air infiltration. At this point, you’ll also need to determine the dew point temperature of the room air as well as the temperature of the supply air

coming into the room. The room air should not have a higher dew point temperature than the surface temperatures within the room or condensation will form. • Pressurization. As mentioned, air should move from cleanest to least clean areas and make up air must be brought in as needed to achieve proper pressurization. To calculate required air volume, determine the free opening areas in the room – full openings and 1/4" crack around doors – for total area (in square feet – sq. ft.), then multiply by 50 to 100 (in feet per minute - fpm) out openings/cracks plus air required for exhaust make up (in cubic feet per minute - cfm). • Air Filtration. Identify the air filtration needs (which equipment and at what MERV rating) for the room. From a design perspective, Hixson recommends that packaging area equipment have pre-filters with MERV ratings of 7-8 and final filters with ratings of 13-14. • Purge Cycle. Keep in mind the sanitation purge cycle necessary for cleaning and start up requires a 2 to 2.5 minute air change rate (per Hixson recommendations). This rate will help keep the fog cleared and help dry the room out faster. To assist in this, the chart included at the end of this article outlines standard conditions for typical rooms found within the meat plant setting. Note that these will not be perfect for every meat plant but are intended to be used as guidelines for typical “ideal” conditions. Consider theWhole Facility! By comparing the data collected and other calculations with the information found in the table, you should be able to identify any new air handling equipment and/or other fixes required to keep rooms cold and dry. However, before instituting changes in any room, you’ll need to assess the impacts those changes may have on rest of the facility:

• Will a domino effect occur? Adding outside air to solve pressurization and condensation issues adds to your overall cooling load and can create the

need for additional compressors, condensers, etc. How will these

additional systems affect other systems and rooms within your facility? Will you have room for this new equipment? Will even more equipment be required down the road? • What is the air balance and pressurization throughout the facility? It is virtually impossible to maintain a positive pressurization in a particular area if the adjoining area air system is not properly balanced. Plus, adding too much outside air in one area may affect the air balance of the facility and create adverse pressurization (preventing doors from closing), which can ultimately have an impact on the goals you’re trying to achieve. • Is your solution cost-effective? Remember that it is more economical to provide make up air to ambient areas being exhausted, than to allow outside air to be brought in through refrigerated areas. When All Else Fails This information is intended to help you understand what problems you may have within the facility and the solutions that may help address those challenges. Because every facility is different, this information may not solve every problem and some challenges may require a more complex, in-depth examination by a professional engineer. However, these guidelines are a good place to start when attempting to apply the AMI principles and make effective cost-to-value decisions within your facility.

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