DAITO Dampers

[DUCTIAQ]

I am in the process of performing a fire damper inspection for a client and have come across a damper that I have never seen before. It is a blade style fire damper with no visible fusible link. Mounted on the outside of the duct, on the damper blade pivot rod, is an arm (approx. 8" long) with a weight on the end, that appears to be designed to help close the damper. The word "DAITO" is cast onto the weight. On the opposing side of the pivot rod and weighted arm there is a "nipple" protruding from the side of the duct that is engaged to keep the weighted arm up (and the damper open). I believe the damper may be activated when heat in the duct affects the "nipple", causing it to retract and allowing the weighted arm to drop , which causes the damper blade to rotate and close.

Is this anywhere near being a correct scenario? I need to know how this damper operates so that I can test the damper per code requirements. I can't find any info on the web regarding this type of damper. Any help would be greatly appreciated.

Thank you.

[powerhead]

Google is your friend:
http://www.freepatentsonline.com/4958687.html

When you get to the page, scroll down for info.

[Tech Rob]

Are you sure it's not a static pressure regulated damper? They also have an extension with a weight attached to the end of the shaft. They open when the static pressure on the inlet side of the damper exceeds the pressure exerted on the shaft by the weight.

[DUCTIAQ]

It could be, but I'm pretty sure it is a fire damper, as it is at a penetration through a 2-hour rated fire wall and not near the AHU. The damper is just a steel blade on a pivot rod. The "nipple" holding the damper open is located on the side wall of the duct, just below the blade damper. I don't see where it would sense any pressure changes there. My thought is that it retracts due to heat and allows the damper to close.

Although, do you think that if heat/smoke sensors were to detect heat (fire) and then shut down the unit, then the "nipple" (static sensor) would detect the pressure drop and close then??

Thanks for the input. I've been on a few forum sites with no responses at all and have exhausted searches on Google and have come up with nothing! Sheesh! Who knew??