Abstract:
A mud saver valve is constructed so that the valve seats self align preventing the loss of fluid when the valve is in the closed position. One or both seats can skew their longitudinal axes to get the alignment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/234,528 filed Aug. 17, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of this invention relates to a method of preventing the leakage or spillage of mud in a drilling environment using a valve having at least on floating seat to provide self-alignment of both seats in the valve. 
       BACKGROUND OF THE INVENTION 
       [0003]    During the process of drilling and completing a well it is necessary to run or pull the pipe into or out of the wellbore. When one section of pipe is removed from the top drive or kelly, mud which is located above the pipe being removed will spill on the rig floor or into the environment. Mud saver valves are available and are in use for the purpose of preventing such spillage. These valves have at least one seat, which is firmly attached to a rigid portion of the valve system. The second seat is firmly guided into contact with the first seat such that if the seats are not perfectly aligned there will be a leak path between them. In practice these devices seldom form a perfect seal and will allow mud to leak onto the rig floor or into the environment. Such an example is disclosed in a Product Bulletin titled “Mud Saver Valve” from Smith Services, a business unit of Smith International. 
         [0004]    Accordingly, it is an object of the present invention to provide a mud saver valve having a seat with at least one seat allowed to float allowing the seats to self align when forced together over their entire surface to prevent leakage of fluid. It is recognized that both seats could be allowed to float further assuring alignment of the sealing faces to provide a seal. 
       SUMMARY OF THE INVENTION 
       [0005]    A mud saver valve attached to a top drive or kelly is disclosed which has at least one floating, self aligning seat to prevent the leakage of mud when sections of pipe below the valve are removed. Such a valve has many uses other than being placed on a top drive or kelly. For example such a valve can be used with casing or drill pipe fill-up or circulating equipment to prevent leakage of mud. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a sectional view of the apparatus shown in the closed position; 
           [0007]      FIG. 2  is a sectional view of the apparatus shown in the open position; and 
           [0008]      FIG. 3  is a sectional view of alternate design shown in the closed position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    Referring to  FIG. 1 , the apparatus is shown inserted into a section of the drill string  10  known as a saver sub. The saver sub is attached to the lower most portion of a top drive, kelly or in a section of a fill-up and circulating device (not shown) at thread B. Drill pipe is attached to the saver sub by and at thread C. Drilling mud is pumped through the central bore E, D of the saver sub  10 . When a section of drill pipe is to be added to the drill string the previous section of drill pipe attached below the saver sub is unscrewed at thread C from the saver sub and another length of drill pipe is added. When thread C is disconnected the mud in the top drive or kelly wants to flow out of the saver sub. 
         [0010]    The valve consists of a lower seat  2  inside of a housing  3 , supported by mandrel  8 . Seal  9  prevents fluid from flowing between the housing  3  and saver sub  10 . A seal  7  is located between the seat  2  and housing  3 . Seat  2  has clearance around seal  7  so that it can relatively rotate with respect to upper seat  1  to improve the alignment at A to enhance the quality of the seal in the closed position of  FIG. 1 . Seal  11  between lower seat  2  and mandrel  8  prevents flow of fluid to prevent erosion of seat  2 , mandrel  8  and the spring  4 . 
         [0011]    The lower seat  2  and mandrel  8  are forced upward by a spring  4 . These components are assembled inside of housing  3  and held in place by upper seat  1 . Upper seat  1  is attached to housing  3  at P. Housing  1  has a seal  13  against bore E. The spring force from spring  4  urges mandrel  8  upward into contact with lower seat  2 . This surface is shown to be arcuate or rounded to allow seat  2  to float or pivot about the center of the arcuate or rounded portion of mandrel  8 . As mandrel  8  and lower seat  2  are forced upward seat  2  contacts upper seat  1  and rotates about the arcuate or rounded surface to force the valve surfaces at A to be in close alignment and firm contact across the entire junction A. When these two surfaces are in close contact is a seal formed. A ball  6  is shown on top of seat  1  also forming a seal between these two surfaces. Ball  6  prevents fluid from flowing out of the valve but allows pressure below the ball  6  to push the ball  6  up so that fluid below the valve can freely flow in an upward direction through the valve. The ball  6  is retained close to seat  1  with a cap  5  which is attached to upper seat  1  at M. 
         [0012]    With the valve in the  FIG. 1  closed position and fluid pressure above ball  6  seated on seat  1 , the valve will not open until the pressure above seated ball  6  exceeds the force of the spring  4  on the lower seat  2  and mandrel  8 . 
         [0013]    Referring to  FIG. 2 , the saver sub  10  is shown in the open position with fluid flowing along flow lines N-N′. Seat  2  and mandrel  8  are forced downward compressing spring  4  by the differential pressure across the area formed by seal  7  and the inside diameter of mandrel  8 . When flow stops spring  4  will urge the mandrel  8  and lower seat  2  into contact with upper seat  1  forming a seal and preventing fluid from falling out of the valve. 
         [0014]    Those skilled in the art will appreciate that the rounded or arcuate portion of the top end of the mandrel  8  allows the seal  7  to be aligned with the seal  11  to improve the sealing quality of the assembly and reduce or prevent unwanted mud spillage when the string is disconnected to add or remove a joint. 
         [0015]    Referring now to  FIG. 3  The saver sub is not shown in this view, only the mud saver valve itself. The valve consists of a lower seat  2  attached to a mandrel  8 , which is guided in a seal surface of housing  3 . Seal  7  forms a tight seal with the seal bore of housing  3  to prevent fluid from flowing through the valve. The lower seat  2  and mandrel  8  are forced upward by a spring  4 . These components are assembled inside of housing  3  and held in place by upper seat  1 . Upper seat  1  is held inside of housing  3  by a keeper ring  9 . Upper seat  1  has an outer surface which is spherical or arcuate or rounded in shape to allow seat  1  to rotate relatively with respect to lower seat  2  to improve the alignment at A to enhance the quality of the seal in the closed position of  FIG. 3 . Seal  11  on the outer surface of valve seat  1  prevents fluid from flowing between upper seat  1  and housing  3 . In operation to open, the pressure from above orients upper seat  1  while flow through upper seat  1  pushes lower seat  2  away from seat  1  to allow flow through the mandrel  8 . 
         [0016]    Those skilled in the art will appreciate that either the upper seat or the lower seat or both can rotate in a way that skews its respective longitudinal axis to promote better alignment in the closed position at location A. As an option at A the seats  1  and  2  can meet as a metal to metal seal or there can also be at least one resilient seal at the interface A.