| 摘要 |
<p>Fire protection valve for air circulation ducts, consists of a built-in sleeve enclosing a valve-seat and a valve closure body which operates automatically when the valve reaches a predetermined temp. The valve seat and the closure body are of fire-resistant materials which are completely in contact when the valve is closed. The fire resistant material pref. consists of an asbestos, gypsum, cement mixt. pref. 40/30/30 wt.%, the cement esp. being a white cement. The sleeve is esp. made of asbestos and is sealed against the frame with rubber O-rings. The device not only prevents the passage of fire through the valve but also closes it to prevent hot air passing through to the rooms to which an air duct leads.</p> |
