This fan is being built off site and i would assume that the fan wheel would be balanced separate on a balancing stand. We plan to visit this shop and check the final results. Can you give me the formula for oz.-in./lb to find the acceptable vibration levels?
It is not an easy task but it can be done with a proper approach. You need not to have a balancing machine if the imeller is not two long. ( D/L ratio is high)
First balance the fan on two knife edges to a maximum. Then fix the fan on the impeller and check the vibration with a known mass and a vibrometer. Selecting the correct mass is to be done on experience depending on the impeller weight. If it could not do completely in the first step you may have to repeat the trial two three times. If the vibration is very large( even difficult to measure the vibration) speed reduction for the test would be a better idea.