| 摘要 |
In combination with a subsurface safety valve for controlling fluid flow through a well tubing of an equalizing system for reducing the pressure differential across the first valve. A housing includes an equalizing line in communication with the bore between points above and below the first valve. An equalizing valve is positioned in the line, operated from hydraulic pressure and opens prior to the opening of the first valve. A labyrinth passageway is provided in the equalizing line upstream of the equalizing valve for providing pressure drops for controlling the velocity of the fluid flowing through the equalizing valve. A seal is provided in the housing to engage the flow tube in its open position for blocking fluid flow in the equalizing line. The equalizing valve closes before the first valve starts to close thereby preventing flow through the equalizing valve. Preferably the labyrinth passageway includes a plurality of grooves and ridges.
|
