| 摘要 |
<p>A Fire Safe Seal for a valve having a metallic seat ring slidable in a cylindrical internal surface with an elastomer ring sealing between the seat ring and the internal surface. An elastomer seal ring or even a highly finished surface on the leading face effects a seal with the valve closure member. An emergency seal ring having a forwardly extending, sharp annular lip with an internal chamfer is engageable, when forced, over a complementary chamfer around the trailing end of the seat ring and into the clearance around the seat ring to seal it off. A spacer ring of a heat destructible material is interposed between the emergency seal ring and the seat ring to render the emergency ring inactive normally.</p> |
