Abstract:
A valve assembly including a first member having a first undulating sealing surface, the first undulating sealing surface having a ridge extending therefrom, a second member having a second undulating sealing surface, the first and second undulating sealing surfaces being complementarily formed, the second member having a seal element for sealing the valve assembly when the first and second members are engaged, the ridge operatively arranged to increase a contact pressure between the first member and the seal element.

Description:
BACKGROUND 
       [0001]    Valves are known in the drilling and completion arts for selectively preventing or enabling a flow of fluid or the like through the valve. Subsurface safety valves are commonly used in these arts. Under low pressure scenarios, valves, such as flapper valves, do not always create an adequate seal as fluid pressure against the flapper is utilized as a part of the energy that causes the sealing effect of the valve. As a result, the industry is always desirous of new valve features with the aim of providing an improved seal. 
       BRIEF DESCRIPTION 
       [0002]    A valve assembly including a first member having a first undulating sealing surface, the first undulating sealing surface having a ridge extending therefrom, a second member having a second undulating sealing surface, the first and second undulating sealing surfaces being complementarily formed, the second member having a seal element for sealing the valve assembly when the first and second members are engaged, the ridge operatively arranged to increase a contact pressure between the first member and the seal element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0004]      FIG. 1  schematically illustrates a perspective view of a flapper valve assembly in an open position; 
           [0005]      FIG. 2  schematically illustrates an enlarged view of a ridge on a sealing surface of the flapper taken generally along line  2 - 2  of  FIG. 1 ; 
           [0006]      FIG. 3  schematically illustrates the ridge of the flapper of  FIGS. 1 and 2  being aligned for engagement with a seal element of a valve seat; and 
           [0007]      FIGS. 4-6  schematically illustrate variables for deriving an equation for forming an undulating sealing surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0009]    Referring to  FIG. 1 , it can be seen that a valve assembly  10  includes a seat  12  and a flapper  14 . The seat  12  includes a groove  16 , which extends around the entire periphery of the seat  12 . The groove  16  is formed in a sealing surface  18  of the seat  12 . The flapper  14  includes a sealing surface  20  that is complementarily formed for mating engagement with the sealing surface  18  of the valve seat  12 . The sealing surfaces  18  and  20  are undulating and/or sinusoidal, as will be described in more detail below. In one embodiment, as indicated in  FIG. 1 , the sealing surfaces  18  and  20  are each formed in an undulating plane transverse to a longitudinal axis  24  around the entire periphery. The flapper  14  includes a hinge  22  in order to enable the flapper  14  to rotate with respect to the seat  12  in order to open and close the valve  10 . 
         [0010]    The sealing surface  20  of the flapper  14  includes a ridge  26  for providing improved sealed engagement between the flapper  14  and the seat  12 . The ridge  26  is shown in more detail in  FIGS. 2-3 . The ridge  26  is formed as a relatively small bump, lip, ridge, crest, protrusion, etc. extending axially from the sealing surface  20  of the flapper  14 . The ridge  26  could be pointed, rounded, flattened, etc. In  FIG. 2 , the ridge  26  has an axial height A and is pointed as a result of the radially inner and outer edges of the ridge  26  being radiused by a radius R 2 . 
         [0011]    As shown in  FIG. 3 , the ridge  26  is aligned with a seal element  28 . The seal element  28  is shown disposed in the groove  16  of the seat  12 . The seal element  28  is, for example, a polytetrafluoroethylene seal, or some other resilient seal element. When the flapper is closed (it is partially opened in  FIG. 3 ), the ridge  26  will “bite” into the seal  28 , which improves sealing performance, particularly low pressure sealing performance, of the flapper  14  and the seat  12 . Alternatively stated, the ridge  26  is included to increase the contact pressure between the flapper  14  and the seal element  28 , thus enabling improved sealed engagement of the flapper  14  and the seat  12  of the valve assembly  10 . In one embodiment, the radii R 2  are approximately in the range of 0.03 inches, while the axial height A is approximately in the range of 0.010 to 0.015 inches. Of course, smaller or larger ridges could also be used, depending on the particular conditions in which the valve assembly  10  is used, although it is to be noted that making the ridge  26  too large may not significantly increase contract pressure, while making the ridge  26  too small may not provide enough material or durability to seal properly or repeatedly. 
         [0012]    Manufacture of the sealing surfaces  18  and  20  of the seat  12  and flapper  14  will be better appreciated in view of  FIGS. 4-6 . In  FIG. 4 , the X-axis represents the centerline of the cutting tool and an arrow  30  the direction of the rotation of the cutting tool. The milling machine holds the piece along the Y-axis and is capable of advancing along the Y-axis, while at the same time rotating it in the direction shown by an arrow  32 . It will be noted that the longitudinal axes of the cutting tool and the piece being cut are perpendicular with respect to each other. The piece to be cut on the Y-axis, whether it is a seat or a flapper (e.g., the seat  12  or the flapper  14 ), is engaged in a machine and rotated and fed along the Y-axis with respect to the cutter, which rotates along the X-axis as indicated by the arrow  30 . 
         [0013]      FIGS. 3-6  illustrate one embodiment of relationships that can be used to program a computer-controlled milling machine in order to produce a sealing surface, which is generally flat, to the longitudinal axis of the seat and the flapper. The significant variables which dictate the positioning of the piece with respect to the cutter are as follows: X 1  dictates the rotational movement required about the Y-axis of the piece with respect to the rotating cutter; R is the inside radius of the sealing (e.g., the surface  18  or  20 ); R 1  is an intersecting radius; and the variable Y illustrates the movement along the Y-axis of the piece with respect to the rotating cutter. Using algebra and known geometric relationships, the variables X and Y can be calculated in terms of known quantities and the machine can be programmed accordingly. The derivation is given in  FIG. 5 : h+Y=R 1 ; Y=R 1 −h ; h 2 +X 1   2 =R 1   2 ; h=(R 1   2 −X 2 ) 0.5 ; Y=R 1 −(R 1   2 −X 1   2 ) 0.5  and in view of  FIG. 6 , with T expressed in radians: sin(T)=X 1 /R; X 1 =R*sin(T); Y=R 1 −{R 1   2 −[R*sin(T)] 2 } 0.5 ; circumference (C)=R*T(2π radians), cord length (X)=R*T(radians) for unwrapped X position on circumference; X=R*T. 
         [0014]    As a result of using these techniques, a seat or flapper can be produced having a sinusoidal or other undulating profile, throughout the 360 degree extent of the surface, where the sealing surfaces are presented in a transverse plane to the longitudinal axis of the seat and the flapper when placed in a mating closed position. 
         [0015]    While the profile of the seat when extended into a two-dimensional plane can be a true sinusoid, modification of a true sinusoid is also within the scope of the invention. In fact, a succession of undulating curves, each forming a segment of a circle having a finite radius, can also be used to create the undulating shape of the seat and the matching flapper. It is also to be appreciated that although the flapper  14  is shown having the ridge  26 , that in other embodiments, the flapper could include a groove and a seal element, while a ridge is disposed on the seat. 
         [0016]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.