Abstract:
A fluid swivel which will tend to generate heat by the sliding friction of the seals on the mandrel which has cooling through the central portion which has enhanced cooling by providing a greater heat transfer area in a restricted area than would be available from a common circular drilled hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Patent application titled MULTI-CHANNEL HIGH PRESSURE SWIVEL filed on the same date.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT: N/A  
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK: N/A  
       BACKGROUND OF THE INVENTION  
         [0002]    The field of this invention is that of multi-port hydraulic swivels for the purpose of communicating high pressure liquids or gasses from a non-rotating location to a rotating location. The most common application is on the central shaft of a hose reel in which the central shaft of the reel rotates with the drum. The drum will be rotating as the hose is rolled out to its intended service. The pressure fluid supply to the reel will characteristically not be rotating, and therefore a rotating union will be required between the non-rotating fluid supply and the rotating main shaft of the reel drum.  
           [0003]    The importance of this type swivel has greatly increased as the drilling of oil and gas wells has moved to deep offshore waters. Drilling contemporarily occurs in 8,000 to 10,000 feet of seawater. In lowering the drilling system to these depths and in lowering certain completion and testing equipment, continuous pressure contact is desired to be maintained between the surface and the subsea equipment being lowered and/or operated. In some cases operational pressure is required as the equipment is lowered. In other cases, maintaining pressure on the system is a safety consideration. If the operator releases the pressure, the hose will become disconnected from the heavy package being lowered and allow the hose to be recovered. This is especially important if the heavy package becomes stuck on lodged in deep water.  
           [0004]    As greater depths are encountered and higher pressures are desired to be maintained as the reel and swivel are rotated. This higher pressure and the inherently higher number of rotations associated with deeper water depth cause specific problems with the swivels.  
           [0005]    A first problem is that a high degree of wear tends to occur in soft seals which can be inserted into machined grooves in the inner or outer surface of the mating parts. If a harder seal can be utilized at the higher pressures, a better or more extended wear life can be provided. An opposing pair of seals can be installed in the end of the outer body to a stopping shoulder and followed by a threaded gland to act as the opposing shoulder. On the other end of the outer body a second set of seals can be inserted to the opposite side of the central shoulder and again followed by a gland. This configuration can be utilized for a single or dual channel swivel, but there are needs for triple and quadruple channel swivels which cannot be serviced in this manner as there are only two ends to the outer body.  
           [0006]    A second problem is that the higher pressure and higher number of rotations generates heat. Heat generated on the outside of the seals disperses into the outer body which has progressively greater area as the distance moves away from the seals, and has a relatively large outer surface to dissipate the heat to the environment. The heat generated at the I.D. of the seal moves toward the centerline of the mandrel portion of the swivel, and literally runs into the heat generated on the opposite of the mandrel. The heat has no place to go, so it builds up to higher temperatures. The higher temperatures characteristically increase the friction, generating more heat at an even faster rate. In some cases we have seen, the heat gets so high in contemporary applications that the seals are actually cooked and fail.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The object of this invention is to provide a swivel which provide enhanced cooling for the removal of heat which is generated by sliding seal friction. A second object of the present invention is more surface area for heat transfer than would be available from a round hole of the same cross sectional area. 
       
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a partial section thru a subsea blowout preventer stack and a view of a reel in which a swivel of this invention would be used.  
         [0009]    [0009]FIG. 2 is a schematic showing how a swivel of this invention is used.  
         [0010]    [0010]FIG. 3 is a half section of a swivel of this invention.  
         [0011]    [0011]FIG. 4 is a partial section of the swivel of this invention showing a spiral thread in one of the circulation ports.  
         [0012]    Section. “A-A” of FIG. 4 is an end view of the circulation port of FIG. 4.  
         [0013]    [0013]FIG. 5 is a partial section of the swivel of this invention showing a spiral thread insert in one of the circulation ports.  
         [0014]    Section “B-B” of FIG. 5 is an end view of the circulation port of FIG. 5.  
         [0015]    [0015]FIG. 6 is a partial section of the swivel of this invention showing a spiral thread insert with a broached hole in one of the circulation ports.  
         [0016]    Section “C-C” of FIG. 6 is an end view of the circulation port of FIG. 6.  
         [0017]    [0017]FIG. 7 is a partial section of the swivel of this invention showing a porous sintered metal insert insert in one of the circulation ports.  
         [0018]    Section “D-D” of FIG. 7 is an end view of the circulation port of FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring now to FIG. 1, a blowout preventer (BOP) stack  10  is landed on a subsea wellhead system  11 , which is supported above mudline  12 . The BOP stack  10  is comprised of a wellhead connector  14  which is typically hydraulically locked to the subsea wellhead system  11 , multiple ram type blowout preventers  15  and  16 , an annular blowout preventer  17  and an upper mandrel  18 . A riser connector  19 , and a riser  20  to the surface are attached for communicating drilling fluids to and from the surface.  
         [0020]    Reel  30  has a frame  31 , spool  32 , and a swivel  33  mounted on the central shaft of the spool (not shown). Hose and/or cable reel  34  is shown going from the spool  32  of the reel  30  to a control box  35  on the subsea blowout preventer stack  10 . From the control box  35 , appropriate hoses  37  go to control various functions, such as ram blowout preventer  16 .  
         [0021]    Referring now to FIG. 2, a reel schematic is shown. Spool  32  is shown mounted on the central shaft  50  which is supported by conventional bearings (not shown). On the left end of the central shaft  50  is mounted a swivel  33  having an outer body  52  and a mandrel  53 . connection  54  attaches the swivel  51  to central shaft  50 .  
         [0022]    Hydraulic lines  60 - 63  are attached to the swivel outer body  52  to deliver pressurized fluids to the swivel from the non-rotating hydraulic supply (not shown). Within the spool, line  70  connects with line  60  and exits the main shaft  50  and goes directly to the hose bundle  80  going to the ocean floor. This line is characteristic of the lines which need the pressure to be maintained during the rotating operations. Gage  81  is provided on this line to monitor the pressure in this line. Line  71  connects with line  61  and also goes directly to the hose bundle and is characteristic of a return line which would not require the high pressure during rotation. Line  72  and  73  connect with lines  62  and  63  respectively and supply a multi-valve panel  82  on the side  83  of the spool  32  for individual control of a multiplicity of lines to subsea equipment.  
         [0023]    Stab Plate  84  engages receptacle plate  85  to give individual hydraulic supply to various selected lines when the reel is not rotating. Control box  86  provides for operational control of the spool  32 , failsafe brakes  87  provide stopping power for the spool  32 , locking pin  88  provides positive position stopping for the spool  32 , and motor  89  provides operations power for the spool  32 .  
         [0024]    Referring now to FIG. 3, a half section of the swivel of this invention can be seen. Inner mounting plate  100  is attached to the main shaft  50  by bolts  101 . Outer mounting plate  102  is mounted to the mandrel  103  by bolts  104 . Outer mounting plate  102  is attached to the inner mounting plate  100  by bolts  105 .  
         [0025]    Mandrel  103  is an cylindrical member with 8 seal surfaces  110 - 117  and locating shoulders  120  and  121 . Fluid pressure communicates thru port  130 , thru seal sub  131 , drilled hole  132 , and out port  133 . Similar flow paths occur in ports  134 , 135  and  136  at 90 degree spacings around the mandrel  103 .  
         [0026]    Body  140  provides a central locating shoulder  141 , and end thread  143  which engaged by a gland  144 , and an end thread  145  which is engaged by gland  146 . The space between the central locating shoulder  141  and the glands  144  and 146 provides cavities for the insertion of seals  150  and  151  on one end and  152  and  153  on the other end. This provides that when high pressure is in the area between these seals, the outward force is directed by an appropriate shoulder or gland to resist the force. By providing the threaded gland design, seals made of hard plastic like material are able to be installed to give superior wear life with respect to soft seals which can be inserted into grooves.  
         [0027]    Similarly, Body  160  provides a central locating shoulder  161 , and end thread  163  which is engaged by a gland  164 , and an end thread  165  which is engaged by gland  166 . The space between the central locating shoulder  161  and the glands  164  and  166  provides cavities for the insertion of seals  170  and  171  on one end and  172  and  173  on the other end. This provides that when high pressure is in the area between these seals, the outward force is directed by an appropriate shoulder or gland to resist the force.  
         [0028]    In this way each of 2 bodies has provided a central shoulder and a gland on each end to trap 2 sets of seals each, for a total of 4 sealed ports. The mandrel  103  has been made from a single piece of metal and provides a straight continuous flow path for the porting. The outer body is not continuous but is rather made of 2 independent bodies  140  and  160 . Mating shoulders  180  and  181  keep the bodies  140  and  160  accurately aligned and bolts  182  keep them attached together for rotary operation. In this way we can install four sets (pairs) of seals which are not amenable to deforming and insertion into grooves. This allows a single swivel to have 3, 4, or more channels of high pressure service.  
         [0029]    Port  190  is an air inlet port which can be used to flow air thru port  191  to allow for cooling of the internal portion of the mandrel  103 . Ports  200 - 204  provide for leak detection from the seals. Thread  210  provides for an anti-rotation means to stop the rotation of the bodies while the mandrel is being rotated.  
         [0030]    Referring now to FIG. 4, the cooling hole  191  has a spiral cut such as with a unified national V thread profile. The depth of the V grooves at 30 degrees will approximately double the metal to air interface for the transfer of the heat from the metal base to the air coolant. Air is the most logical coolant to use as when it is expelled out of the end of the swivel, there is no need to capture the exhausted air. Other medium such as water can be used but would normally require both supply and return plumbing. In addition to the benefit of greater surface area for transferring the heat from the mandrel to the air, the spiral will tend to cause the air to spin and in some cases will cause some turbulence in the air. Smooth laminar flow is not as efficient as tumbling turbulent air for the carrying away from the heat.  
         [0031]    Section “A-A” is an end view of the circulation hole of FIG. 4.  
         [0032]    Referring now to FIG. 5, a similar design is shown, except that the thread type profile is not cut into the base metal, sometimes requiring an extremely deep tapping operation on multi-channel swivels. In this case a slightly larger hole is drilled and then a series of short internally threaded sleeves  230  are pressed or glued in place.  
         [0033]    Section “B-B” is an end view of the circulation hole of FIG. 5.  
         [0034]    Referring now to FIG. 6, a design similar to FIG. 5 is shown, except that notches  241  are shown in the threaded profile  242  in the internally threaded sleeve  240 . In this case a square broach of an appropriate size is pushed through the threaded profile to give 4 notches at approximately 90 degrees. These notches w ill tend to break up the flow and contribute to the turbulence mixing and therefore efficiency of heat transfer.  
         [0035]    Section “C-C” is an end view of the circulation hole of FIG. 6.  
         [0036]    Referring now to FIG. 7, an alternate style is shown with a hole drilled and then a set of porous sintered metal inserts  250  are inserted. The porous material will be intimate contact with the base material of the mandrel, and will communicate the heat through the porous material at the heat transfer rate of that material. Being adequately porous, the air will flow thru the porous material and have substantial extra contact areas to receive heat.  
         [0037]    Section “D-D” is an end view of the circulation porous material of FIG. 7. Other combinations of spirals, notches, porous materials and similar method can be used to enhance the heat transfer efficiency of this system.  
         [0038]    The foregoing disclosure and description of this invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as the details of the illustrated construction may be made without departing from the spirit of the invention.