Auf Feuer ansprechende Spindelhaltevorrichtung

摘要

A fire responsive stem retention apparatus for a non-rising stem valve including an outer hollow sleeve secured to the top of the valve bonnet around the valve stem. An inner cap is received in the outer hollow sleeve and closely fitted therewithin, and houses upper and lower stem bearings therein. The inner cap has a shoulder which provides an upper support for the upper stem bearing. Under normal environmental conditions, the inner cap is sweated to the outer sleeve with a thin layer of fusible material. The upper bearing and stem are prevented from moving upward by the shoulder on the inner cap, and an annular shoulder on the stem is prevented from engaging a backseat in the bonnet. Under fire conditions, the thin layer of fusible material melts rapidly, freeing the inner cap from the outer sleeve and permitting the stem to rise until the annular shoulder on the stem engages the backseat in the bonnet. A screw in the inner cap rides in a slot in the outer sleeve, preventing removal of the inner cap from the sleeve.