| 摘要 |
<p>A safety valve has a lock open feature that is actuated by expanding or penetrating the flow tube to disconnect the link between the piston in the hydraulic control system and the flow tube. In normal operation, downward movement of the piston moves the flow tube against a power spring. When the flow tube is expanded, penetrated, or otherwise altered, the piston no longer acts on the flow tube and the flow tube can be simply pushed down and locked in position with the flapper wide open.</p> |
