Damper Sizing Conventions

[simpeltech]

I am having a discussion on damper sizing and it came down to which factor to use for calculating the required torque for a damper. Now, I proposed the use of the following will more than suffice:

1. For opposed blade actuators with seals is ~5 in-lb/sq.ft.
2. Torque Loading multiplier of 1.5 for fpm of 2000 to 3000 fpm.
3. So 7.5* X sq.ft. = Total torque required(in-lbs)

So, I was told to use 14 in-lb/sq.ft. for a 40+ year old OA damper that is 30.38 sq.ft and 888 fpm. Does that sound right to anyone? Is my information above bad? My logic is that at the actuator will be oversized to overcome a lack maintainance on the damper. And also, will oversizing have a negative effect on a dampers' mechanical operation?

Thanks to everyone ahead of time for your help and time.

 

[CountOlaf]

Your 5 to 7.5 in-lb/SF seems in-lne with the recommendations Belimo has for selecting actuators (albeit, for new dampers presumably). I don't know how much of a fudge factor you'd have to add for age. Given some of the standard actuator sizes, you might have to go to 2 actuators even using your numbers much less the 14 in-lb/SF factor. Could try contacting Belimo directly to see what they recommend--if you need two actuators anyway and you have to go with standard sizes, it might not make that much difference (e.g., two, 180 in-lb actuators--won't get you to 14 but close to 12).

FYI, there was a "damper actuator torque" post from this past December where someone had a link to the full Belimo catalogue.