torque requirement for damper

[spike]

We use a motor to open or close dampers on a hvac type unit. Various manufacturers of dampers publish values of torque requirements in lb-in per square foot of damper area. These values are based on Face velocity (fpm)and static pressure (in.wc).
How would you determine the torque requirement if the dampers are opened or closed when there is no fan running, that is, there is no face velocity or static pressure when the motor is used.

 

[byrdj]

i would assume the required torque would be reduced to the "weight" of the flapper and the friction on the shaft and linkage. i invision the flapper could be "balanced" and thus the operating torque will be friction. The amount of friction would depend upon the precission and sophictication of the design. Thus a very good design assembled properly will take very little torque. The actual torque could be measured with the proper size torque wrench or with an attached arm and fish scale.

 

[plasgears]

A damper element with hinge line located near the middle should be nearly load canceling, meaning that air loads with be minimized for the actuator. Unless you're using low friction bushings, the main load will be frictional. Provide for end-of-travel slipping or stops to avoid damaging the damper.

 

[MintJulep]

I would ask the damper manufacturer. If they don't have the answer at-hand, I would measure some that I had.

 

[amorrison]

Well . . .
If you have the face velocity vs. torque curve graph look at the line where the velocity is zero.