Patent Application
20190331223
The present invention relates to seal assemblies, and more particularly to axial face seals used in abrasive environments.
Axial face seals are known and typically include an annular seal body formed of an elastomeric material. The seal body has at least one radial-extending surface on an axial end which sealingly engages an annular surface or “face” of a component, such as a drill pipe. Particularly when used in a highly abrasive environment, such in as a fracking pipe-line swivel joint, the combination of relative rotation of one pipe and the abrasive materials in the fracking fluid often cause degradation of the seal body material and possible failure of the seal.
In one aspect, the present invention is a seal assembly for sealing between first and second tubular members, each tubular member having a central passage and a generally annular end surface surrounding the passage. The first member passage is fluidly coupled with the second member passage and the first member end surface faces and is spaced apart from the second member end surface along a central axis. Also, the first member is angularly displaceable about the axis with respect to the second member. The seal assembly comprises a generally annular primary seal member formed of a first, generally compressible polymeric material. The primary seal member has inner and outer radial ends, a first axial end disposeable against the first tubular member end surface and a second axial end disposeable against the second tubular member end surface. The first axial end has a radially-extending, generally annular primary sealing surface sealingly engageable with the first tubular member end surface. A generally annular secondary seal member is formed of a second, generally rigid polymeric material. The secondary seal member has opposing first and second axial ends and a radially-extending, generally annular secondary sealing surface on the first axial end. The secondary seal member is coupled with the first seal member such that the secondary sealing surface extends generally coaxially about the primary sealing surface, the secondary sealing surface being sealingly engageable with the first tubular member end surface.
In another aspect, the present invention is a mechanical assembly comprising a first tubular member having a central passage and a generally annular end surface surrounding the passage and a second tubular member having a central passage and a generally annular end surface surrounding the passage. The first member end surface faces and is spaced apart along a central axis from the second member end surface and the first member is angularly displaceable about the axis with respect to the second member. A seal assembly is provided for sealing between the first and second member end surfaces and includes a generally annular primary seal member formed of a first, generally compressible polymeric material. The primary seal member has inner and outer radial ends, a first axial end disposeable against the first tubular member end surface and a second axial end disposeable against the second tubular member end surface. The first axial end has a radially-extending, generally annular primary sealing surface sealingly engageable with the first tubular member end surface. A generally annular secondary seal member is formed of a second, generally rigid polymeric material. The secondary seal member has opposing first and second axial ends and a radially-extending, generally annular secondary sealing surface on the first axial end. The secondary seal member is coupled with the first seal member such that the secondary sealing surface extends generally coaxially about the primary sealing surface. The secondary sealing surface is also sealingly engageable with the first tubular member end surface.
The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
Certain terminology is used in the following description for convenience only and is not limiting. The words “inner”, “inwardly” and “outer”, “outwardly” refer to directions toward and away from, respectively, a designated centerline or a geometric center of an element being described, the particular meaning being readily apparent from the context of the description. Further, as used herein, the words “connected” and “coupled” are each intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.
Referring now to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown in
The second polymeric material M2 has a coefficient of friction substantially lesser than the coefficient of friction of the first material M1. As such, the secondary seal member 40 experiences substantially less wear and generates substantially less heat during angular displacement of the first tubular member 12, during which the tubular member annular surface 18 slidably displaces against the sealing surfaces 34, 44. Preferably, the first polymeric material M1 is an elastomer, such as natural or synthetic rubber, most preferably a highly chemical compatible elastomer such as highly saturated nitrile, e.g., hydrogenated nitrile butadiene rubber (“HNBR”), an FKM fluoroelastomer (“FKM”), or any other generally similar materials. The second polymeric material M2 is preferably a thermoplastic polymer, most preferably polytetrafluorethylene (“PTFE”) or alternatively nylon, Delrin, or any other generally similar materials.
The primary seal member 30 includes a generally annular body 31 having a centerline LCP, inner and outer radial ends 30a, 30b, a first axial end 32A and a second axial end 32B, as indicated in
Thus, when the seal assembly 10 is installed within the seal gland GS, axial displacement of one of the tubular members 12, 14 toward the other member 14, 12 compresses the primary seal member 30 between the two end surfaces 18, 22. Conversely, the primary seal member 30 decompresses or expands during axial displacement of one of the tubular members 12, 14 away from the other member 14, 12 to maintain contact with the end surfaces 18, 22 of the tubular members 12, 14, respectively. Thereby, sealing engagement of the primary sealing surface 34 with the first tubular member end surface 18 is maintained during angular displacement of the first tubular member 12 or/and axial displacement of either tubular member 12 or 14.
Referring to
With the structure of the two seal members 30, 40, both the primary sealing surface 34 and surrounding secondary sealing surface 44 are engaged with the end surface 18 of the first tubular member 12 when the seal assembly 10 is installed within the seal gland GS, with the primary seal member 30 preferably being generally in a state of compression. When one of the first and second tubular members 12, 14 displaces axially toward the other one of the first and second tubular members 14, 12, the primary seal member 30 compresses, or compresses further, between the first and second tubular members 12, 14. During such compression of the primary seal member 30, the secondary sealing surface 44 remains sealingly engaged with the first tubular member 12 as the secondary seal member 40 displaces axially with the compressed “backing” portion of the primary seal member 30. i.e., the portion of the seal member 30 between the secondary seal member 40 and the second tubular member 14. Alternatively, when one of the first and second members 12, 14 displaces axially away from the other tubular member 14, 12, the primary seal member 30 expands between the first and second tubular members 12, 14 while the secondary sealing surface 44 remains sealingly engaged with the first tubular member 12 as the secondary seal member 40 is displaced or biased by the “backing portion” of the primary seal member 30.
Thus, the structure of the rigid secondary seal member 40 being coupled with and carried by the compressible primary seal member 30 ensures that sealing engagement of both sealing surfaces 34, 44 is maintained during relative angular and/or axial displacement of the tubular members 12, 14. Further, due to the substantially lesser coefficient of friction of the secondary seal member 40, the amount of heat generated during relative angular displacement of the first and second tubular members 12, 14 is significantly reduced. Thereby, material degradation of the primary seal member 30, particularly within the region of the sealing surface 34, is also substantially reduced or even entirely eliminated in comparison with previously known axial “face” seals.
Referring now to
Preferably, the backing ring 50 has generally L-shaped axial cross-sections and includes an axially-extending portion 52 located generally at the primary seal member outer radial end 30b and a radially-extending portion 54 located generally at the primary seal member first axial end 32A, as indicated in
Referring to
With the above structure of the primary seal member 30, the secondary seal member 40 is preferably disposed circumferentially about the axial shoulder 36 of the primary seal member 30 and is preferably sized such that an inside diameter (not indicated) of the secondary seal member 40 is slightly larger than an outside diameter (not indicated) of the axial shoulder 36. However, the axial shoulder 36 and secondary seal member 40 may be alternatively sized so as to engage with an interference fit to assist in retaining the secondary member 40 on the primary member 30, or even to define a gap (not shown) between the shoulder 36 and the seal member 40.
Further, the secondary seal second axial end 42B is disposed generally against at least a section of the recessed side portion 38 of the primary member first axial end 32A, and the secondary seal member 40 preferably has an axial thickness (i.e., between the axial ends 42A, 42B) about equal to the axial length (not indicated) of the axial shoulder 36. Thereby, the primary sealing surface 34 and the secondary sealing surface 44 are generally radially “flush” or located generally within the same radial plane (not indicated) when the assembly 10 is installed in the gland GS, as best shown in
As best shown in
Referring again to
Further, the secondary seal member 40 is preferably a first secondary seal member 43A with a first secondary sealing surface 45A and the seal assembly 10 further comprises a second secondary seal member 43B having a second secondary sealing surface 45B. The second secondary seal member 43A is coupled with the primary seal member 30 such that the secondary sealing surface 45B extends generally coaxially about the second primary sealing surface 35B, preferably about the second axial shoulder 37B. When the seal assembly 10 is installed in one orientation as depicted in the drawing figures, the second secondary sealing surface 45B is sealingly engageable with the second tubular member end surface 22 and when installed in the reversed orientation, the second secondary sealing surface 45B is sealingly engageable with the end surface 18 of the first tubular member 12. Both the first and second secondary seal members 43A, 43B are preferably identically constructed and formed as described in detail above.
Furthermore, the backing ring 50 is preferably a first backing ring 51A and the seal assembly 10 preferably further comprises a second backing ring 51B formed generally identical with the first backing ring 50 and as described as above. The second backing ring 51B is disposed on the primary seal member 30 such that the ring axial portion 52 extends along a second radial recessed portion 62 on the primary seal member outer radial end 30b and the ring radial portion 54 extends along a second axial recessed portion 38 on the seal member second axial end 32B. The second backing ring 51B functions to prevent extrusion of the primary seal member 30 in the region of the outer axial end 30b when the seal assembly 10 is arranged in the second orientation (not shown).
Thus, with the preferred symmetric structure, the seal assembly 10 may be installed within the annular gland GS such that either primary sealing surface 35A or 35B and the associated secondary sealing surface 45A, 45B, respectively, sealingly engages the end surface 18 of the first tubular member 12. However, the seal assembly 10 may alternatively be formed having only a single primary sealing surface 34, preferably provided on an annular axial shoulder 36, a single secondary seal member 40 with a secondary sealing surface 44, and a single backing ring 50.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as generally defined in the appended claims.
