Abstract:
To seal an inboard member to an outboard member, a metallic annular seal is inserted into the outboard member to align with an inwardly-open channel in the outboard member. The seal is outwardly expanded at least partially into the channel by a combination of elastic and plastic deformation. The seal is released to allow inward elastic partial recovery. The inboard member is inserted into the seal with interference so as to further outwardly expand the seal and provide sealing engagement between the inboard and outboard members.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of U.S. patent application 60/870,142, entitled SEAL and filed Dec. 15, 2006, the disclosure of which is incorporated in its entirety herein as if set forth at length. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to seals. More particularly, the invention relates to sealing between concentric members. 
     Sealing between inboard and outboard concentric members has presented practical problems, especially when involving aggressive or high temperature fluids. The problems generally relate to the capturing of the seal by one of the members. For example, the seal may be captured in a radially open channel/groove in one of the members and may engage a cylindrical surface of the other member. If the channel is an outwardly open channel in the inner/inboard member, placing the seal in the channel presents difficulties. An elastomeric seal may simply be stretched and released into the channel. A metallic seal may need to be split to permit its expansion. Accordingly, side-by-side dual split metallic seals are often used in combinations where the splits are offset from each other and the associated gaps are sealed radially by means of another split ring between the pair and the channel base. 
     Whereas elastomeric seals may suffer lower robustness than metallic seals, the metallic seals may suffer greater complexity and manufacturing cost. An alternative may involve assembling at least one of the members of multiple pieces so that the channel is closed only after a continuous metallic seal ring is installed. This, however, also presents manufacturing and space-efficiency detriments. 
     An inwardly open channel in the outer/outboard member may be used with an elastomeric or split seal wherein the seal is contracted (e.g., by looping, flexing, or overlapping of ends) to permit installation and then manipulated (e.g., worked in by hand) to fill the channel. This presents similar detriments to those described above. 
     SUMMARY OF THE INVENTION 
     Accordingly, one aspect of the invention involves a method for sealing an inboard member to an outboard member. A metallic annular seal is inserted into the outboard member to align with an inwardly-open channel in the outboard member. The seal is outwardly expanded at least partially into the channel by a combination of elastic and plastic deformation. The seal is released to allow inward elastic partial recovery or springback. The inboard member is inserted into the seal with interference so as to further outwardly expand the seal (e.g., to achieve sealing engagement with both members). 
     In various implementations, during the insertion of the inboard member, a first longitudinal end of the channel may restrain the seal. The insertion of the inboard member may bring the seal into bi-directional sealing engagement with the channel. The insertion of the inboard member may bring the seal into engagement with an outboard base surface of the channel. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial central longitudinal sectional view of a pipe coupling. 
         FIG. 2  is an enlarged view of a seal region of the coupling of  FIG. 1 . 
         FIG. 3  is a partial central longitudinal sectional view of the seal of the coupling of  FIG. 1 . 
         FIG. 4  is a partial central longitudinal sectional view of the seal of  FIG. 1  in a first stage of installation. 
         FIG. 5  is a view of the seal of  FIG. 4  in a second stage of installation. 
         FIG. 6  is a view of the seal of  FIG. 4  in a third stage of installation. 
         FIG. 7  is a view of the seal of  FIG. 4  in a fourth stage of installation. 
         FIG. 8  is a view of the seal of  FIG. 4  fully installed. 
         FIG. 9  is a view of the seal of  FIG. 7  under internal pressure loading. 
         FIG. 10  is an end view of an expander. 
         FIG. 11  is a sectional view of the expander of  FIG. 10 , taken along line  11 - 11 . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a pipe coupling (coupler)  20  including first and second members (or coupling moieties)  22  and  24  and a central longitudinal axis  500 . The exemplary members have (longitudinally) outboard ends  26  and  28  and inboard ends  30  and  32 . Portions adjacent the outboard ends may be adapted (e.g., sized, shaped, or otherwise configured) for mating to associated pipes  34  and  36  (e.g., by welding as is known in the art). The members  22  and  24  may be pre-mated to the respective pipes  34  and  36  (i.e., before mating the members to each other), although other variations are possible. A portion  40  of the first member near the inboard end  30  has an exterior sealing surface  42 . A portion  44  between the sealing surface and the outboard end is externally threaded. In the coupled/assembled/mated condition of the exemplary coupling, an annular rim surface  46  of the first member  22  at its inboard end  30  abuts an internal shoulder surface  48  of the second member  24 .  FIG. 1  also shows a radial direction  502  and a direction of insertion  504  of the first member  22  into the second member  24 . 
     The second member  24  has an internally threaded portion  50  positioned to mate with the externally threaded portion  44  of the first member. Between the internally threaded portion  50  and the outboard end  28 , the second member has a sealing portion  52  having an interior surface  54  and an inwardly open channel  56 . A seal  60  ( FIG. 2 ) is carried in the channel to seal with the sealing surface  42  of the first member. The exemplary channel  56  is a right channel having an inboard radially-extending longitudinal end (side) wall  62 , an outboard radially-extending longitudinal end wall  64  spaced therefrom, and a longitudinally-extending base wall  66  joining the end walls  62  and  64 . Non-right channels may be used (e.g., a dovetail where both end walls taper to converge away from the base wall or semi-dovetail where just one (e.g.,  64 ) does). 
     The exemplary seal  60  is a continuous annular metal ring (e.g., not split or segmented) which may be radially expanded to fit in the channel.  FIG. 3  shows the ring as having an exemplary central longitudinal cross-section characterized by a rounded-corner equilateral triangle. The triangle has three faces  80 ,  82 , and  84  and three rounded corners  86 ,  88 , and  90 . The exemplary triangle is oriented so that: one of the corners forms an inboard extreme  92  of the seal in a relaxed condition; another of the corners forms a relaxed outboard radial extreme  94  and one of the longitudinal extremes or rims  96 ; and the final corner forms the other longitudinal extreme or rim  98 .  FIG. 3  further shows a seal height H (between longitudinal extremes  96  and  98 ), an inner radius R I  at the inboard extreme  92 , and an outer radius R O  at the outboard extreme  94 . 
     The corners  86 ,  88 , and  90  have respective centerlines  100 ,  102 , and  104 . The seal may be placed in the channel  56  via an at least partially inelastic expansion. The centerline  100  of the illustrated inboard corner  86  is angled off-radial (by an angle θ i ) to project from the corner partially against the direction of insertion  504  of the first member relative to the second member. 
     In an exemplary installation sequence, the seal is mounted to a segmented expander such as is known for use in flaring or expanding tubing. An outer diameter (OD) surface of each segment or shoe  120  ( FIG. 4 ) engages the seal along the inboard corner  86 . The exemplary shoes  120  have a radially outwardly open circumferential channel  122  defined by a surface  124 . A cross-section of the channel  122  may be complementary to the cross-section of the seal  60  to longitudinally retain the seal relative to the shoes during seal insertion and expansion. For example, outside of the coupling the shoes may initially be in a maximally radially retracted condition wherein the seal may be installed via passing over a radial rim  126  or  128  of the assembly of shoes. The shoe assembly may then be radially expanded to capture and retain the seal via the channel  122 . The expander may then be inserted (e.g., through the end  32  of the first member  24 ) to bring the seal into longitudinal alignment with the channel  56  ( FIG. 4 ). 
     The shoes/segments are then driven radially and circumferentially apart to expand the seal to enter the channel  56  ( FIG. 5 ). This expansion may include elastic and inelastic (plastic) components. The expander shoes may be configured so that their seal-engaging OD peripheries are coaxial with the axis  500  at the completion of seal expansion and before expander contraction. The expander may be contracted to release the outward pressure on the seal. A portion of the expansion will reverse (elastic springback). However, the non-reversed expansion is enough to leave the seal partially within the channel ( FIG. 6 ). When sufficiently contracted, the expander may then be withdrawn/extracted from the second member  24 . 
     Upon insertion of the first member  22  (e.g., in a final stage of the threading of the first member into the second member  24 ), a portion of the first member may engage the seal ( FIG. 7 ). In the illustrated example, a portion having a tapered surface  130  between the first end  30  and the sealing surface  42  initially engages the seal. Further insertion (e.g., via further threading) drives the members  22  and  24  further together. The seal  60  is retained by the second end wall  64  of the channel engaging the corner  90 . The insertion causes interference between the seal  60  and the first member  22  (e.g., surface  130 ) and second member  24  (e.g., end wall  64 ) and drives the seal radially outward along the tapered surface  130  to expand the seal into engagement with the channel base surface  66 . In/after a final stage of insertion, the interference is such that the seal inboard corner  86  is sealingly engaged to the sealing surface  42  while the corner  88  is sealingly engaged to the channel base surface  66  to seal the members ( FIG. 8 ). 
     Internal pressurization of the joint (e.g., from the working fluid) may expose a portion of the channel space on one side of the seal to a pressure above that on the other side of the seal. The shape and dimensions of the seal cross-section may be configured so that this pressure biases the seal into firmer engagement with the channel  56  and/or sealing surface  42 . In the exemplary seal ( FIG. 9 ), the inboard corner  86  and adjacent sides  80  and  82  separate a portion of the space  150  from a portion  152 . The exemplary portion  150  may be proximate the interior of the coupling whereas the portion  152  may be proximate the exterior. Internal pressurization thus acts to provide a pressure differential in the portion  150  over the portion  152 . In the exemplary seal, this pressure difference may act to bias the corner  88  into engagement with the longitudinal end wall  62  (e.g., into engagement with a rounded intersection of the end wall  62  with the base  66 ). This intersection and the corner  88  may thus serve as a fulcrum about which the pressure differential seeks to rotate the seal cross-section clockwise as viewed in  FIG. 9 . This pressure difference may, therefore, bias the inboard corner  86  into firmer engagement with the sealing surface  42  so as to maintain sealing integrity. During this process, the remaining seal end  90  may be out of engagement with the channel end (e.g., having a slight gap). 
       FIG. 10  is a view of an exemplary expander  200  having a circumferential array of expander shoes  202 . The shoes  202  are mounted for radial movement to a baseplate  204  ( FIG. 11 ). The baseplate and second member may have mating features for longitudinally registering the seal with the channel. An exemplary mating feature includes a radial shoulder  208  of the baseplate engaging a mating shoulder (e.g.,  48 ) of the second member  24 . An expander  210  (e.g., a pyramid expander having camming facets  212 ) may be mounted to the baseplate for relative longitudinal reciprocal motion (e.g., driven by a push-pull cylinder or other actuator  220 ). When the pyramid expander is driven toward the baseplate, the camming surfaces  212  drive associated surfaces  230  of the segments radially outward. The exemplary expander  210  may bottom against a shim pack  240  carried by the baseplate. The thickness of the shim pack may be selected to provide a desired expansion at the point of bottoming. The expander may be retracted to permit release of the segments. The segments may radially retract under bias of return springs  250  guided by shoulder bolts  252 . Exemplary shoe and expander material is beryllium copper. Exemplary baseplate material is aluminum alloy. 
     The use of metallic seal may provide improved robustness over elastomeric seals (e.g., a greater pressure capacity and temperature capability). The use of a continuous seal rather than a split ring may present one or both of improved sealing and reduced manufacturing cost. The formation of the channel  56  in a single piece (e.g., rather than one piece forming surface  62  and another forming surface  64 ) may provide one or more of space efficiency, reduced manufacturing cost, and robustness. Exemplary use is in the oil industry (e.g., pipes conveying crude or refined oil). In exemplary oil applications, the coupling members  22  and  24  may be made of a corrosion-resistant steel or other alloy. Other exemplary alloys used in the manufacture of seals may also be used for the present seals and include nickel-aluminum bronze, beryllium copper, nickel-based superalloys (e.g., Alloy 718, optionally silver plated), and stainless steel. Exemplary couplings have minimum inner diameters (ID) of at least 200 mm (e.g., 200-600 mm). Various alternative rectangular, trapezoidal, and other shapes of seal cross-section and their associated manufacturing techniques are disclosed in U.S. patent application Ser. No. 11/610,220, filed Dec. 13, 2006, the disclosure of which is incorporated by reference herein as if set forth at length. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the particular anticipated pressure differences may influence the selection of seal cross-sectional shape and orientation (e.g., for desired pressure assist in one or both sealing directions). Use may be in joints other than those shown (e.g., bolted flange joints or clamped joints instead of threaded joints). Use may be in situations more complex than simple end-to-end pipe coupling (e.g., within wellheads, distribution manifolds or other situations). In reengineering, remanufacturing, or retrofit applications, details of the existing components to be sealed may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.