Patent Application
20120012327
The field of the invention is barrier valves and more particularly valves for subterranean use that have a pressure equalizing feature that is operated by the control system for opening and closing the valve.
Isolation valves are used in subterranean locations for separating one location from another by preventing flow. Some of these devices are safety valves that have the ability to control pressure differential in a direction from below to above. These safety valves have a closure device known as a flapper that is operated by a flow tube that is in turn actuated by a hydraulic piston operated through a hydraulic system controlled at a surface location. In flapper type valves the need to equalize pressure across the flapper when in the closed position has been met with a valve located in the flapper that is first encountered by the flow tube to open a passage through the flapper for pressure equalization before the flow tube pushes the flapper itself to turn 90 degrees to the open position as the flow tube advances past the displaced flapper. Examples of such designs can be seen in U.S. Pat. Nos. 4,478,286; 6,644,408; 6,848,509 and 6,877,564.
Other designs have focused on pressure equalizing across the hydraulic piston that actuates the flow tube in the event there is a seal leak or tubing failure in the control system. In those instances in systems with two control lines there is an equalizing valve in the hydraulic system that can open to put the operating piston in pressure balance so that a closure spring acting on the hydraulic piston pushes up the hydraulic piston and with it the connected flow tube so that the safety valve can close. One example of such a system is U.S. Pat. No. 6,109,351.
The present invention also deals with the concept of pressure equalization across a closed closure member. The reason to equalize pressure across the closure element is to make it possible for the operating system for the closure member to do its job. The control system components do not have to be designed to resist the higher differential pressures which for example can significantly increase seal friction when trying to for example rotate the ball or plug to the open position. There are basically three ways to equalize across a closed valve member before trying to open it. The flow can be equalized either through the member, between the member and one of its seats or between locations on opposed sides of the closed member but spaced apart from the member. In the present invention, the latter option is employed and the normal hydraulic system for opening and closing the valve member is employed in a manner that allows for equalization through passages that are discrete from the hydraulic lines that normally operate the valve member. In essence, in the preferred embodiment, the equalization takes place via the same mechanism that will ultimately open the valve. These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
A barrier valve has an equalizing feature for the ball or plug when in the closed position before it is opened. A hydraulic open and a close line are connected to a housing so that they can move a piston in opposed directions. The piston ends are sealed and the exterior of the piston is tapered to push one or more bypass valves open to connect tubing pressure across the ball when ramped off its seat. Pressure on the main hydraulic line to close the ball reverses the piston movement and allows a spring bias to close the bypass valve or valves. The equalizing system can be integrated into the barrier valve housing or can be separate as a retrofit.
The valve 10 is shown in
The equalization in this design occurs when lines 46 and 48 are connected to the equalizer valve assembly 50. Line 46 branches from line 38 and line 48 branches from line 42. Line 46 connects at connection 52 and line 48 connects at connection 54.
Referring to
Line 104 carries tubing pressure above ball 18 and extends from the valve housing 16 to connection 72 while line 106 carries tubing pressure and extends from housing 110 and below the ball 18 to connection 74. Annulus 108 extends around piston 56 and between seals 58 and 60. When poppets 68 and 70 ride up ramps 62 and 64 the flanges 76 and 80 lift off the seats 78 and 82 and flow is established for tubing pressure between connections 72 and 74 and pressure on opposed sides of the closed ball 18 is equalized followed by pressure buildup on piston 34 that turns the ball to open. The open sequence is initiated with pressure on line 38 that goes into line 46 to move the piston 56 to the right to a travel stop. That movement ramps out the poppets 68 and 70 and immediately equalizes pressure on closed ball 18 by opening tubing flow between connections 72 and 74. Further pressure buildup beyond what it took to slide the piston 56 against seal friction at seals 58 and 60 shifts the piston 34, the carriage 30 and the piston 36 to the right in
While the housing 50 is shown in
The illustrated design has advantages over an equalizing method that involves separation of seals 24 or 26 from ball 18. The problem is the separation at ball 18 can cause a momentary high flow situation past the seals 24 or 26 which can erode them to the point of being unserviceable after a predetermined number of cycles. The illustrated equalizing method orients the passages from the connections 72 and 74 at a shallow angle to the seats 78 and 82 so that erosion effects are minimized. In the
While there concerns regarding seal failures as there would be in any such device, from a perspective of a failsafe operation barrier valves are invariably installed in a well with other safety valves that have systems designed to allow well closure should the illustrated systems develop a seal problem to the point of being inoperable.
The operating personnel need not be concerned with the pressure equalizing before trying to open the valve 10 under differential pressures as high as full working pressure because the feature works automatically to equalize and resets the system when the ball is again closed.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
