| 摘要 |
<p>1424573 Valves J GACHOT 10 April 1973 [25 April 1972] 17245/73 Heading F2V In a valve for inclusion in pipelines for conveying petroleum products, a ball closure member 3 is provided with a certain freedom of movement in the downstream direction when the valve is closed and the seating ring 8 is made of a plastics material, e.g. p.t.f.e., which becomes molten at high temperatures such that when the valve is closed in the event of fire, the seat becomes molten and the pressure of the upstream fluid moves the member 3, forces the seating ring 8 into a relief space and the member 3 then seats on a supplementary metallic seat 7 formed on the end pieces 2 of the body of the valve as shown in Fig. 3. The movement is made possible by a groove 11 in the member which freely accommodates an extension of the spindle. The ring material may comprise 50% p.t.f.e. and 50% small particles of stainless steel. The supplementary metal seating ring 24, Fig. 8, of another embodiment is provided separate from the housing and is joined to the plastics seating ring 21 and also covered with the same plastics material.</p> |
