-Additional help: We already had 3 of our belt-driven exhaust fans installed on the back wall of our welding department to draw out welding fumes and for general ventilation. For this project, we custom made the panels for two of these fans to have holes to act as outlets at the end of the blower ducts. Thanks to this design; when these fans run they help draw out additional airflow from the blowers’ outlets. Now, the blowers provide localized exhausting of each welding job while the wall fans remove any excess to keep the air of our plant clean.
Measuring Your Airflow:
If you need to figure out how much CFM your fan or blower is moving, you can use an airflow meter to measure the velocity of the air, and use the formula below to turn you feet per minute (FPM) to cubic feet per minute (CFM):
CFM = FPM x Duct Cross Section Area
In our case, we had 6-inch round ducts. So after converting that to feet, we used to find the cross section area, where r is the radius of the duct, or .25 feet, making the area .196 square feet. Multiplying whatever FPM measurement you get on your airflow meter will give you your CFM.
Maximizing CFM is all about limiting disruptions to the airflow. While the ideal solution would have been to have a blower per table, we believe we did the practical solution, and ended up getting approximately 230 CFM per table.