Operating mechanism which automatically unlatches the blade of the fire damper if the temperature in the duct exceeds a certain level (standard 72°C, but also possible for model CK2 for higher temperatures of 100 or 140°C).
Due to the temperature rise the lead melts down and the fusible link opens. The internal torsion spring thus loosens and the blade closes. Once the fusible link has melted down, it needs to be replaced.
The correct functioning of the fire damper with fusible link can periodically be tested by manually unlocking and rearming it. By installing an end of range switch on the mechanism, the position (open or closed) of the fire damper can be controlled.
