Wells – Valves – closures or changeable restrictors – Longitudinally movable operator
Reexamination Certificate
1999-07-13
2001-05-08
Bagnell, David (Department: 3672)
Wells
Valves, closures or changeable restrictors
Longitudinally movable operator
C137S515000, C137S527000, C137S535000, C251S298000, C251S337000
Reexamination Certificate
active
06227299
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to flapper type valves and, in particular, to a flapper type valve that includes a flapper closure plate for controlling fluid flow therethrough that is biased into sealing engagement with the flapper seat by a flapper closure assembly that pushes on the back face of the flapper closure plate.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, the background will describe surface controlled, subsurface safety valves, as an example.
Surface controlled, subsurface safety valves are commonly used to shut in oil and gas wells in the event of a failure or hazardous condition at the well surface. Such safety valves are typically fitted into the production tubing and operate to block the flow of formation fluid upwardly therethrough. The subsurface safety valve provides automatic shutoff of production flow in response to a variety of out of range safety conditions that can be sensed or indicated at the surface. For example, the safety conditions include a fire on the platform, a high or low flow line temperature or pressure condition or operator override.
During production, the subsurface safety valve is typically held open by the application of hydraulic fluid pressure conducted to the subsurface safety valve through an auxiliary control conduit which extends along the tubing string within the annulus between the tubing and the well casing. Flapper type subsurface safety valves utilize a closure plate which is actuated by longitudinal movement of a hydraulically actuated, tubular piston. The flapper valve closure plate is maintained in the valve open position by an operator tube which is extended by the application of hydraulic pressure onto the piston. A pump at the surface pressurizes a reservoir which delivers regulated hydraulic control pressure through the control conduit. Hydraulic fluid is pumped into a variable volume pressure chamber and acts against the crown of the piston. When, for example, the production fluid pressure rises above or falls below a preset level, the control pressure is relieved such that the piston and operator tube are retracted to the valve closed position by a return spring. The flapper plate is then rotated to the valve closed position by a torsion spring or tension member.
It has been found, however, that in tight safety valve applications having a large inner diameter and a small outer diameter, typical torsion spring or tension member designs provide insufficient bias or closure force to lift the flapper plate to the closed position. In the case of a torsion spring, the size and therefore the closure force of the torsion spring are limited by the space available to house the torsional spring. In the case of a tension member, closure force is limited by length of the lever arm between the hinge pin of the flapper plate and the location where in the tension member is attached to the linkage that extends from the hinge in the direction opposite of the flapper plate.
Therefore, a need has arisen for a flapper valve that has sufficient bias or closure force to lift the flapper plate into the closed position in tight applications. A need has also arisen for such a flapper valve the can produce the required closure force without increasing the space available for a spring within the flapper valve. A need has further arisen for such a flapper valve that can take advantage of a longer lever arm to exert a greater closure force to the flapper plate.
SUMMARY OF THE INVENTION
The present invention disclosed herein comprises a flapper valve assembly that has sufficient closure force to move the flapper closure plate to the closed position in tight applications. The flapper valve assembly disclosed herein produces the required closure force without the need for increasing the size of the spring within the flapper valve. The flapper valve assembly of the present invention utilizes a longer lever arm to exert an increased closure force to the flapper plate.
The flapper valve assembly of the present invention comprises a tubular valve housing having a hinge and a longitudinal hole. A valve seat is mounted within the housing. The valve seat has a valve seat sealing surface and defines a flow passage therethrough. A flapper closure plate is rotatable about the hinge between a valve open position and a valve closed position. In the valve open position, the flapper closure plate is removed from the valve seat. In the valve closed position the sealing surface of the flapper closure plate sealingly engages the valve seat sealing surface for preventing flow through the flow passage.
The flapper closure plate has a notch on the side opposite the sealing surface of the flapper closure plate that is spaced a distance from the pivot point of the hinge. A flapper closure assembly biases the flapper closure plate toward the closed position. The flapper closure assembly includes a spring that is mounted within the longitudinal hole and a connection member that is operably coupled to the spring and engages the notch such that when the flapper closure plate is moved toward the open position, the spring is compressed causing the connection member to urge the flapper closure plate toward the closed position. The distance between the notch and the hinge provides a moment arm sufficient for the flapper closure assembly to bias the flapper closure plate from the open position to the closed position which may be about 90 degrees.
The flapper closure assembly may include a piston member that is at least partially disposed within the hole. The piston member couples the spring to the connection member. The connection member may be rotatably coupled to the piston member and may be rotatably received within the notch of the flapper closure plate. The connection member may have an arcuate shape such that the connection member exerts a moment on the flapper closure plate when the flapper closure plate is in the open position.
In one embodiment of the present invention, the flapper valve assembly may be incorporated into a subsurface safety valve that is adapted to be placed in a well tubing string to control flow therethrough. The subsurface safety valve comprises a valve housing having a bore therethrough, a hinge and a longitudinal hole. A flapper closure plate is mounted within the bore and is rotatable about the hinge. The flapper closure plate is movable between an open position and a closed position. The flapper closure plate has a sealing surface on one side and a notch on the opposite side. An operator is movably disposed within the bore for controlling movement of the flapper closure plate from the closed position to the open position. A flapper closure assembly biases the flapper closure plate toward the closed position. The flapper closure assembly includes a spring mounted within the longitudinal hole and a connection member that is operably coupled to the spring and that engages the notch such that when the flapper closure plate is moved toward the open position, the spring is compressed causing the connection member to urge the flapper closure plate toward the closed position. A valve seat is disposed within the valve housing. The valve seat has a sealing surface such that when the subsurface safety valve is in the closed position, the sealing surface of the flapper closure plate sealingly engaging the sealing surface of the valve seat.
REFERENCES:
patent: 5145005 (1992-09-01), Dollison
patent: 5159981 (1992-11-01), Le
patent: 5201371 (1993-04-01), Allen
patent: 5310005 (1994-05-01), Dollison
patent: 6050294 (2000-04-01), Makowan
Bagnell David
Dougherty Jennifer R.
Halliburton Energy Service,s Inc.
Herman Paul I.
Youst Lawrence R.
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