| 摘要 |
<p>1451510 Downhole well safety valves SCHLUMBERGER TECHNOLOGY CORP 20 Dec 1973 [29 Dec 1972] 59016/73 Heading E1F A downhole well safety valve has a main closure member 82 cooperable with a seat ring 70 arranged downstream of a further seat 212 cooperable with a flow restrictor member 210 which is normally held clear of seat 212 by ambient pressure acting thereon in opposition to a spring 208 and a gas pressure in chamber 170. The main closure member is connected to an operator sleeve 90 carrying a piston 134 responsive to ambient pressure acting upwards thereon over area A 1 in opposition to spring 112 and the pressure downstream of the seat ring 70 acting over area A 2 . The valve is adapted to be latched in a production string and if due to excess flow through the string, the ambient pressure falls to a level allowing the flow restrictor member 210 to approach seat 212, the consequent pressure differential arising across the piston 134 raises the latter and the operator sleeve 90 to engage closure member 82 with seat ring 70. The flow restrictor member returns to its lower position as the ambient pressure subsequently increases, and the closure member is movable to its open position by increasing the pressure in the production string until the pressure in the string acting on piston 134 depresses the latter against the action of the ambient pressure. Extension 135 of the piston cooperates with an extension 137 of sub 38 to discourage sand from accumulating above the seal ring 132 of the piston.</p> |
