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BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Apparatus for providing a rotatable pipe flange is provided. More particularly, a rotatable flange adapter or rotatable flange is provided that may be used, for example, on land drilling rigs between a blowout preventer and a flanged connector and for other applications.  
         [0003]     2. Description of Related Art  
         [0004]     Normal practice in drilling of wells for hydrocarbon production is to place a blowout preventer (BOP) at the surface of the earth. This is a device designed to prevent flow outside the drill pipe should excess pressure be encountered during drilling of a well. When drilling a well that may encounter high pressure, a ram-type BOP is employed, along with an annular BOP and related equipment to form a “BOP stack.” The combined devices may weigh as much as 85,000 pounds or more. The rams may extend several feet in a vertical plane in each direction from the axis of the BOP.  
         [0005]     During drilling of wells, the BOP stack is connected to casing that has been previously placed in the well. The BOP stack may be installed and removed several times during drilling of the well as additional casing strings are placed and cemented in the well. The first casing string placed in the well is called the “conductor casing.” It may be driven into the earth or placed and cemented in a drilled hole. Conductor casing is often 20 inches in outside diameter. After it is placed, the well is drilled to a selected depth and the next smaller casing string is placed in the well. In land wells, this is often a casing string having a diameter of 13-  5 / 8  inches. It is called the “surface casing.”  FIG. 1  illustrates well  10  that has been drilled to an intermediate depth. Conductor casing  11  was placed in the well at a shallower depth, then the well was drilled deeper and surface casing  12  was placed in the well and cemented in place. Casing head  14  was attached to the top of surface casing  12 . Spool  16  has been placed on the surface casing. Spool  16  may be a tubing head spool, for example, or may be a spool for supporting a smaller casing string. Spool  16  has flange  18 , which may have a diameter of 11 inches or 13-  5 / 8  inches. Casing head  14  of surface casing  12  normally has a 13-  5 / 8 -inch flange. Double studded adaptor  20  is necessary to join casing head  14  and spool flange  18  if flange  18  is 11-inch. Typical wellhead assembly nomenclature and geometry are provided in API Specification 6A/ISO 10423, available from the American Petroleum Institute.  
         [0006]     A conventional BOP flange, having a diameter of 13-  5 / 8  inch, is suited for use on the surface casing head, which normally has a 13-  5 / 8 -inch flange. However, after the first spool is attached, as shown in  FIG. 1 , when the blow-out preventer is to be re-attached for drilling ahead, another spool adapter must be used to transition from flange  19 , which is an 11-inch flange, to a 13-  5 / 8 -inch flange. This can be accomplished by use of double studded adapter  20 , placed in the reverse direction from its initial use between flange  14  and flange  18 .  
         [0007]     To understand the need on a drilling rig for the invention disclosed here, the procedure for attaching a BOP stack to flange  19  or flange adaptor  20  must be understood. Referring to  FIG. 2 , BOP stack  22 , which may be comprised of BOP pipe rams  22 A, annular preventer  22 B and other ram  22 C, is supported from beams  23  under the drilling floor (not shown) of a land rig by supports  23 A and hoist  23 B. It is common practice now for the workers to rotate BOP stack  22  while it is hanging from beams  23  by applying force to hoists  23 B. This may be necessary in order: to align bolt holes in flanges  24  and  19  or a double-studded adaptor attached to flange  19 , or to avoid interference of a structure under the rig floor with rams  22 A, for example. This rotation places unpredicted side loads on BOP stack  22  and unpredicted additional tension in supports  23 A. The rotation also causes BOP stack  22  to move upward, requiring adjusting hoist  23 B to lower stack  22 . This rotation and lowering of the BOP to match flanges becomes an operation that can put workers at risk. Hence, the need for the rotatable flange adapter  25 , disclosed herein. Alternatively, a rotatable flange could be provided as an integral part of a BOP stack.  
         [0008]     Other instances arise where rotatable pipe flange adaptors or rotatable flanges are needed. The need may arise when flanges are used for structural applications. In this instance there is no requirement for a pressure seal between flanges, and the flanges then are used to transfer mechanical forces. A rotatable flange can provide adjustable positions of structural parts. When pressure is to be confined in tubulars attached to the flanges, a seal is required, but rotatable flanges may still be needed to allow infinite adjustment of the angle of one flange with respect to another flange. A rotatable flange will not be limited to aligning flanges only by rotating to another bolt hole in the flanges.  
         [0009]     A swivel ring flange is known in the art. Such devices are available from the HydroTech division of Oil States, for example. This device, although it facilitates bolt hole alignment, requires external retaining means for keeping a rotating flange ring integral to the hub of the device. “Rotating Joint” devices are also known and available from FMC and others. Typical rotating joints are designed to allow for one segment of a pressure-containing pipe to rotate relative to another segment. The joint also includes a pressure seal between the rotating segments.  
         [0010]     What is needed is apparatus and method that eliminate the need to rotate a BOP stack in order to match bolt holes in flanges or to avoid interference from rig structure with a BOP. Also, apparatus and method are needed to provide adjustment of the angular position of one flange with respect to another flange and transmitting force between the flanges, with or without pressure sealing between the flanges.  
       SUMMARY OF INVENTION  
       [0011]     In one embodiment, rotatable flange adaptor is provided that can be used to align a blowout preventer (BOP) flange and a flange on a well structure without rotating the BOP during installation. This is accomplished by providing a device comprised of two parts, called a hub and a ring, that are rotatable around their common axis. The hub and the ring each have a flange of a selected size and hole-pattern. The hub provides a pressure seal inside the contact between the hub and ring, so no moving pressure seal is necessary. The hub and ring are joined mechanically by keys inserted in matching races in each of the moving parts. In an alternate embodiment, the hub is made an integral part of a blowout preventer or other apparatus and a rotatable flange is mechanically joined thereto. In yet another embodiment, rotatable flange or flange adaptor without a pressure seal is provided for structural applications. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  illustrates common industry practice during drilling of a well, where two casing strings and a spool have been installed by using a double-studded adaptor (Prior Art).  
         [0013]      FIG. 2  illustrates installation of a BOP stack on a spool using a rotatable flange adaptor disclosed herein.  
         [0014]      FIG. 3  is a drawing of one embodiment of a rotatable flange adaptor wherein the hub and ring are mechanically joined by cylinders in races formed in each part.  
         [0015]      FIG. 4  is a cross-sectional view of the rotatable flange adaptor of  FIG. 3 .  
         [0016]      FIG. 5  is a drawing of one embodiment of a rotatable flange adaptor wherein the hub and ring are mechanically joined by balls in races formed in each part.  
         [0017]      FIG. 6  is a cutaway view of the rotatable flange adaptor of  FIG. 5 .  
         [0018]      FIG. 7  is a drawing of one embodiment of a rotatable flange adaptor wherein the hub and ring are mechanically joined by a split ring in races formed in each part.  
         [0019]      FIG. 8  is an assembly view of the rotatable flange adaptor of  FIG. 7 .  
         [0020]      FIG. 9  is a drawing of a rotatable flange as an integral part of a blowout preventer.  
         [0021]      FIG. 10  is a close-up view of the rotatable flange of  FIG. 9 .  
         [0022]      FIG. 11  is a side view of the rotatable flange and blowout preventer of  FIG. 9 . 
     
    
     DETAILED DESCRIPTION  
       [0023]     Referring to  FIG. 1 , well  10  is being drilled in the earth. Conductor casing  11  has been placed in the well and the well has then been drilled below the conductor casing to a selected depth. Surface casing  12  has then been placed in the well and cemented in place. Casing head  14  has been attached to surface casing  12  and double studded adapter  20  has been attached to the casing head. Spool  16 , having flanges  18  and  19 , has been attached to the double studded adapter. The double studded adapter is necessary when flange  18  on spool  16  is smaller in size then the flange on casing head  14 . With this equipment on the well, the well is to be drilled deeper toward a target in the earth. Before drilling proceeds below surface casing  12 , it is necessary to attach a blowout preventer (BOP) to the casing in the well.  
         [0024]     Referring to  FIG. 2 , blowout preventer stack  22  is to be attached to the well. Stack  22  is supported from beams  23  below the drilling rig floor. Supports  23 A and hoist  23 B support stack  23 . Stack  22  includes annular BOP  22 B and ram-type BOPs  22 A and  22 C. The BOP stack may also include other equipment not shown in  FIG. 2 . At the bottom of stack  22  is flange  24 , which is to be attached to the well by flange  19  and pressure-sealed. Normally, flange  19  has a diameter of 11 inches. Therefore adapter  25  must be inserted between the 11-inch flange  19  and the normally 13-  5 / 8 -inch flange  24  on a BOP. One alternative is to employ a double studded adapter, such as shown at  20  in  FIG. 1 , in the opposite direction to convert the 11-inch connection to a connection suitable for the 13-  5 / 8 -inch flange  24 . This is normal practice. Flange  25  of  FIG. 2  is the rotatable flange disclosed herein. It will be described in more detail, in its various embodiments, below. A salient feature of adapter  25  is that it provides a means to avoid rotating BOP stack  22  while it is being placed on the well using supports  23 A and hoists  23 B.  
         [0025]      FIG. 3  shows a drawing of one embodiment of a rotatable flange adapter. Hub  30  includes race  32 A. At the top of hub  30  is ring groove  35 , adapted to receive ring gaskets (not shown), which provide a pressure seal on hub  30 . Other means for providing a pressure seal may be provided, such as an o-ring in an o-ring groove, or other sealing methods known in the art may be used. A ring groove or other sealing means is also present on the other (not shown) side of hub  30 . Ring  38  is adapted to be placed over hub  30  and to rotate with respect to hub  30  above a shoulder on the hub. Ring  38  includes boltholes  39 , port  40  and race  32 B. Port  40  is to be used for placing cylinders  34  into the space between races  32 A and  32 B. After cylinders are placed, using procedures described below, plug retainer  42  is inserted into port  40  and held in place by screw  42 A. A port for grease injection into race  32 B (not shown) may be placed in ring  38 . Grease seals may be added on each side of the race in either ring  38  or hub  30 .  
         [0026]     To assemble the adapter flange, hub  30  may be placed on a bench and supported with its axis in the horizontal direction. Ring  38  may then be lifted with an overhead hoist and its internal diameter placed over hub  30  in a concentric location. Port  40  would preferably be in a vertical or 12 o&#39;clock position. Rollers would then be inserted through port  40  and allowed to find the bottom of races  32 A and  32 B, which are preferably filled with cylinders. Once all of the cylinders are placed, plug  42  is inserted and fastened into place with screw  42 A.  
         [0027]      FIG. 4  shows a cross-sectional view of the flange adapter of  FIG. 3 . Ring  38  is adapted to rotate on hub  30 , with cylinders  34  in matching races that are formed into hub  30  and ring  38 . Cylinders  34  serve as shear keys. They are used to transmit forces from the hub to the ring. Port  42  is sized to allow cylinders  34  to pass down the port, into the races without becoming lodged in the port. Ring groove  35  at the top of hub  30  and ring groove  33  at the bottom of hub  30  are also shown. Holes  31  are preferably threaded and sized to accept stub bolts used for attaching hub  30  to other pressurized equipment. Holes  37  are provided to be used by insertion of a rod or other tool in a hole to assist in rotating ring  38 . Alternatively, flats may be formed on ring  38  to assist in rotating ring  38 .  
         [0028]      FIG. 5  illustrates an alternate embodiment of a rotatable adapter flange. Hub  50  includes race  52 A, which receives balls  54 . Matching race  52 B has been formed in ring  58 . Ring  58  also includes bolt holes  59  and holes  60  for assisting in rotation of the ring. Grease port and seals (not shown) may be added for supplying grease to the races.  
         [0029]      FIG. 6  shows a cutaway view of the rotatable adapter flange of  FIG. 5 . Hub  50  includes bolt holes  51  that are threaded to receive stud bolts. Ring groove  63  is adapted with ring gaskets (not shown) for pressure sealing of hub  50  to adjoining apparatus. Port  61  allows placement of balls  54  into the races between hub  50  and ring  58 . Plug  62  may be placed into port  61  after balls  54  are in place. Again, balls  54  serve as shear keys to couple hub  50  and ring  58  so that forces may be transmitted between of the two parts of the rotatable adapter flange.  
         [0030]     Referring to  FIG. 7 , yet another alternative embodiment of a rotatable adapter flange is illustrated. Hub  70  contains race  72 A and seal ring groove  76 . Ring  78  is sized to be placed on hub  70 , with matching race  72 B. Split ring  74  is placed in race  72 B before ring  78  is brought into place over hub  70 . Ring  78  is then placed over hub  70 . Fasteners  82  are then inserted into holes  80  to cause split ring  74  to move into a keying position in matching races  72 A and  72 B. The location of fasteners  82  may be measured and marked such that split ring  74  is in proper position. Bolt holes  79  may be used for mating ring  78  with adjoining equipment. Provisions for supplying grease to the races may be added, as described above.  
         [0031]      FIG. 8  shows a drawing of the rotatable adapter of  FIG. 7  after ring  78  is in place and stud bolts  82  have been inserted and moved to position to place the split ring in a keying position between hub  70  and ring  78 .  
         [0032]     The rotatable flange adapters illustrated in the figures above are provided as separate apparatus that may be attached to well equipment such as shown in  FIG. 2 . The equipment may be installed at a well site as follows. The hub (13-  5 / 8  inch side) is bolted to the bottom flange of the BOP using stud bolts. The BOP is moved into position over the wellhead mating flange, as shown in  FIG. 2 . This flange is normally an 11-inch flange. The ring portion of the adapter flange may then be rotated to mate stud bolts  25 A in the holes of flange  19 . The blind drilled holes such as shown at  60  in  FIG. 5  or in  FIG. 7  may be used along with a spanner or cheater bar to assist in rotating a ring to the desired position. A flange gasket may be put into place in a groove. Illustrated in the figures is a ring gasket; however it should be understand that any other flange-sealing apparatus may be used. The BOP may then be lowered down to rest on the mating gasketed flange. Stud bolts may then be installed and tightened as required.  
         [0033]     Referring to  FIG. 9 , a rotatable flange on an integral hub is illustrated. BOP rams  90  have integrally formed hub  92 . Race  94 A has been formed in hub  92 . Ring  98 , having matching race  94 B, is adapted to be placed over hub  92 . Shear keys such as cylinders  96  may then be placed in races  94 A and  94 B. Plug  99  is sized to be used in port  99 A  
         [0034]     By using an integral hub to a BOP, as shown in  FIG. 9 , a manufacturer may avoid welding a ring flange hub to the BOP body. Welding requires a high-integrity connection, which is very costly. This is especially true for high pressure ratings, where thick walls are necessary. Therefore, the manufacturers of these components either cast of forge the basic shape of the flange into the body of the pressure-containing parts. Prior art ring flanges must be welded on since the outer ring is assembled onto the hub from one side to mate the load-bearing shoulders. This limits assembly to the side that is to be welded onto the component fitted to. In the apparatus disclosed herein, the ring can be assembled to the hub without the limitation posed by the load shoulder.  
         [0035]      FIG. 10  shows a close-up of the flange of  FIG. 9 . Port  99 A is more clearly seen, along with cylinders  96  that may be inserted through port  99 A.  FIG. 11  is a side view of the same apparatus, showing that hub  92  is make integral with BOP  90 .  
         [0036]     Although the present disclosure has been described in detail, it should be understood that various changes, substitutions and alterations can be made thereto without departing from the scope and spirit of the invention as defined by the appended claims.

Summary:
Rotatable flange adaptor or rotatable flange is provided, such that bolt holes may be aligned for joining of flanges. A sealing device may be added to the hub of the adaptor, such that the sealing surfaces are not rotated. Keys are placed in races to provide for transmittal of force along the axis of the device while allowing rotary motion of a flange or flange adaptor.