Events and Exhibitions
substances or an explosive atmosphere in the interior . Energy saving comes from adaptation of the volume flow to requirements and is the most important reason for selecting variable air flow , noted Unterdorfer .
There are special situations which require a constant air volume control for fume hoods . These include :
• High thermal loads due to there being a lot of equipment inside from which there is heat dissipation
• If there is a fume scrubber or washer for the extraction of air and causing a high pressure drop , requiring constant high volume flow to combat that pressure drop which then suits constant air flow
• For some people it is the lower investment that prompts the choice of constant air volume control , as it requires fewer sensors and simpler , possibly mechanical , controls
There are six control strategies of fume hoods :
• Constant volume
• 2-point control
• 3-point control
• Sash position sensor
• Face velocity sensor
• Combination of face velocity and sash position RACA
TROX branding at the event .
velocity sensors . Different monitoring concepts are required , and finally what is most important in the market is easy installation and wiring . The system is already complicated enough without further complexity in installation ,” he said .
When it comes to fume hoods and extract cabinet control ( which are similar ), from a controls point of view a fume hood is just a box with a window . The requirements of a fume hood are retention , purging and protection . Retention in a fume hood means it must avoid escape of gases , whereby particles can disappear out of the interior fume hood . For purging the fume hood , dangerous concentrations must be avoided inside the hood and it must have a splash guard and shatter protection .
“ A complete solution which is highly efficient , modular and offers a high degree of flexibility to future extensions or refurbishments of laboratory spaces .”
WHY VARIABLE AIR VOLUME CONTROL FOR FUME HOODS ? For optimal airflow , there must be low-turbulence flushing of the fume cupboard at all opening heights of the sash ; formation of a roller through optimal flushing with the sash closed ; no turbulence on the table ; no influence on experiments ; risk reduction of the formation of high concentrations of hazardous
A selection of the attendees present at the TROX SA presentation .
www . refrigerationandaircon . co . za RACA Journal I April 2023 23