My company builds industrial sized centrifugal fans (40"-120"+ impeller diameters), and we treat "Fan Engineering" like it is the Bible.  Recently I have been put in charge of developing a damper line to go with our fans.  I've started with the AMCA books (500-503), but I was hoping some of you could site some good references for me to help guide my research.  Most of the information I have found so far is about lightwheight dampers with velocities below 2000fpm, but I am dealing with velocities in the range of 3000-8000fpm.  Anyways I'd like to take a detailed planned approach at this and I need a good starting point.

A company called ACDC-get your minds out of the gutter it stands for Air Clean Damper Company wrote the book on dampers and changed them from being just a piece of duct work to an engineered product.

I don't know if they are still around, but their chief engineer left and founded a company named Effox.  (Guess what his name was.)  I'm pretty sure they are still around.

They should be able to give you some good standards.  Don't try to reinvent this wheel or you will become just one more fan company suppling a piece of junk for the damper.

Ruskin makes heavy duty dampers for high velocity/pressure application. I suggest also you look into butterfly valve design and consult control vendors to make sure you get the correct damper operator and control setup tp prevent shock.
We had a client that wanted to save money by omitting isolation dampers in dual fan (parallel operation) systems. He said they would just block the the failed fan with plywood to prevent recirculation. I hope he reinforce that plywood with 2" x 4" on 6'" centers!
There is also a new design called fan wall wherein numerous small plug fans are used in parallel to produce large CFM but in a very short length section. The fans are controlled in unison by a VFD. Thus if one fan fail, the other fans speed up to makeup for the recirculated flow in the failed fan.

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