| 摘要 |
PURPOSE:To operate a valve without an increase in diameter of a valve stem of a packing portion more than required by providing a self-sealing heat-resisting packing adapted to operate only at the time of an abnormal high temperature such as a fire or the like outside the conventional packing for sealing a fluid round the valve stem to be used in combination therewith. CONSTITUTION:In the normal use condition, a fluid between a valve stem 25 and a valve cover 16 is sealed by a soft packing 37. In such a condition, a heat-resisting packing 44 is not pressed to the valve stem 25 not to be damaged. When a valve is subjected to a high temperature such as a fire, an annular disc 39 is first fused due to a temperature rise of the valve to flow out to an escape space 40, so that a packing presser loses the axial support force, and the heat-resisting packing 44 mounted on the forward end of a taper projection 38 is forced to slide along the taper surface of a taper seal hole portion 42 and pushed up by the fluid pressure applied to the cross-sectional area of the soft packing 35, thereby to seal a fluid round the valve stem 25.
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