www . refrigerationandaircon . co . za RACA Journal I July 2023 27
Feature
Next is the SOP ( Standard Operating Procedure ), a guide for establishing appropriate housekeeping procedures essential for the overall contamination control programme of the facility . Within each industry they normally have a specification as to how clean the facility must be , varying from sector to sector .
“ It comes down not just to the correct filtration , but also the correct amount of air changes within that classified facility and the distribution of the air diffusers in the right places to get the correct ISO standard ,” says Rean van Wyk .
“ The impact of clean air is tremendous : for example , we ’ ve had reports from a chicken farmer as to how much quicker their chickens grew after installing HEPA filters in the supply air to the chickens .
“ If it ’ s a storage facility for , say , raw materials , one has to look at what is the raw material : sealed , corrosive or non-corrosive , if in the cold chain does it have to be temperature- and humiditycontrolled ? From that one can determine the correct filters as they form part of the broader HVAC system .
“ If it ’ s a facility where there ’ s fumes or odours from production , the air needs to be extracted – but while extracting , you need to provide fresh air from somewhere , and that needs a filter to keep out external dust and particles that can cause contamination ,” says Rean van Wyk .
Carel van Wyk adds , “ When simply providing fresh air to a standard office building , the first defense is primary filters ( G2 to G4 ). They are often cheap , washable filters with a rule of thumb being to wash it three to four times and thereafter dispose of . There ’ s no fixed rule because it entirely depends on the circumstances , including their position in the HVAC system .”
The secondary defence is a pocket or a bag filter , and through the years the technology on these filters has improved considerably – for instance , instead of stitching the fabric it is today welded with what is called sonic fusion .
“ It ’ s a good filter , but what we see in practice is maintenance people trying to clean it by vacuum , which causes damage . In the pharmaceutical or medical sector , these filters are inappropriate and instead a cassette filter should be employed for its very good dust holding capacity and greater longevity .”
The third defence in filtration is the HEPA filter for any microbial growth , viruses or germs . There are also different classifications as to efficiency of the HEPA filter , points out Carel van Wyk . Where filter technology is headed is to manufacture filters on which the pressure drop is lower , thereby requiring a smaller lower-energy fan motor . Fan technology has changed in terms of the fan design to also make the fan more energy efficient , especially the EC fan . RACA
www . refrigerationandaircon . co . za RACA Journal I July 2023 27