Abstract:
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.

Description:
FIELD OF THE INVENTION 
       [0001]    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. 
       BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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. 
         [0004]    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. 
       SUMMARY OF THE INVENTION 
       [0005]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an overall view showing the pressure equalizing system associated with the barrier valve; 
           [0007]      FIG. 2  is the equalizing valve assembly in the closed position; and 
           [0008]      FIG. 3  is the equalizing valve assembly in the open position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    The valve  10  is shown in  FIG. 1 . It has a top sub  12  and a bottom sub  14  for connection to a tubing string that is not shown. In between is a multi-component housing that has a ball  18  that is shown in the open position and flanked by sleeves  20  and  22 . Sleeves  20  and  22  have at their respective ends that face the ball  18  seals  24  and  26 . The ball  18  rotates on axis  28  supported in a frame  32 . A movable carriage  30  engages the ball  18  in an offset location from the axis  28  so that opposed translation of the carriage  30  results in rotation of the ball  18  between the open position that is shown and the closed position. Hydraulic pistons  34  and  36  are on opposed sides of the carriage  30  to urge it in opposed direction depending on where the hydraulic pressure is applied. Applying pressure in line  38  at connection  40  pushes the assembly of piston  34 , carriage  30  and piston  36  to the right to move the ball  18  to the shown open position. Hydraulic pressure in line  42  at connection  44  moves the carriage  30  and the pistons  34  and  36  in the opposite direction to close the ball  18 . Lines  38  and  42  continue to the surface where the controls are located for opening or closing the ball  18  by selectively applying pressure in one of those lines and removing applied pressure from the other. In this manner the operation of the ball  18  is controlled but without any feature for pressure equalization before attempting to operate the ball  18 . 
         [0010]    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 . 
         [0011]    Referring to  FIG. 2  the equalizing valve assembly  50  is shown in more detail. A passage  109  extends between connections  52  and  54 . A piston  56  has a seal  58  near connection  52  and a seal  60  near connection  54 . Piston  56  is solid and has ramps  62  and  64  that are spaced apart. In the view of  FIG. 2  the ball  18  is in the closed position and poppet valves  68  and  70  are both in the closed position to block off connections  72  and  74 . Poppet  68  has a flange  76  that is sealing against a seat  78  and poppet  70  has a flange  80  that seals on seat  82 . Spring  84  bears on flange  76  to hold it against seat  78 . Spring  86  bears on flange  80  to hold it against seat  82 . Caps  88  and  90  respectively retain the assemblies of poppets  68  and  70  in the ports  92  and  94 . Ports  92  and  94  go into a reduced dimension where the poppets  68  and  70  extend. The reduced dimension defines the seats  78  and  82 . At their lower ends the poppets  68  and  70  have a T-shaped passage, respectively,  96  and  98 . In the  FIG. 2  position the aligned opposed angled ends of the T-shaped passages are up against the reduced bores  100  and  102  formed in the housing  50 . 
         [0012]    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  FIG. 1  to open the ball  18  after pressure is equalized across it. Putting pressure on line  42  pushes piston  56  to the  FIG. 2  position from the  FIG. 3  position and allows both poppets  68  and  70  to reseat after riding down ramps  62  and  64 . 
         [0013]    While the housing  50  is shown in  FIG. 1  separate from the body  16  of the barrier valve  10 , it can just as easily be integrated into the body  16  to take up less space and to facilitate making the tubing connections and to provide greater protection for the structures as an integrated unit. While  FIGS. 2 and 3  show the use of a shifting piston ramping out poppets to cause pressure equalization for ball  18  there are other ways to cause that result and they are within the scope of the invention. Those skilled in the art will appreciate that the design allows for normally actuating the closed valve to open from the surface with a pressure applied to one control line and removed from another while automatically getting the benefit of equalizing pressure on the closed ball before the pistons that turn the ball are actuated. It should be noted that in a two control line system as illustrate the assembly is depth insensitive as the hydrostatic pressure in one of the control line is offset with the hydrostatic pressure in the adjacent line for the opposite function. Accordingly piston  56  is in pressure balance hydrostatically as are the operating pistons  34  and  36 . Those skilled in the art will appreciate that a single line system can be used instead of a two control line system where the closing force can be provided by a spring assembly either mechanically or pneumatically such as by using a charged pressure chamber. The piston  56  in such systems can also be similarly biased as the operating pistons  34  and  36  to the valve closed position of ball  18 . 
         [0014]    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  FIG. 3  position when flow begins into the T-shaped passages  96  or  98  the entering flows abut each other to reduce their velocity and also minimize erosion. Optionally the entire poppet assembly and its mating seat can be a unit that is easily removed from housing  50  after use to put the assembly quickly back into service. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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.