I’m getting a loss number of 186″ (or some other absurdly high number). Can this be correct?
In theory it can. In reality, no centrifugal blower can run at losses that high so it has not been tested. Look at the velocities, and the CFM input. Read the example at the bottom of the example problem, about 10,000 CFM in a 4″ duct. The sheet will not differentiate between an absurd input and a reasonable one. • You keep talking about velocity, velocity, velocity. I’m thinking in terms of CFM. How are they related? Velocity is measured in feet per minute (FPM). To get good pickup of sawdust and chips plus keep our vertical runs from plugging we need a target airspeed of at least 3700 FPM. Air engineers try to provide 4000 FPM airspeed to provide a little extra without forcing the use of too large of a blower that will cost more to buy and run. Pressure drop is calculated based on velocity in FPM, not CFM. CFM and FPM are related by the cross sectional area of the duct. FPM = CFM / AREA, where CFM is in cubic feet per minute and area is in square feet. For example, a 4″ duct has a cr
