Patent Publication Number: US-10316604-B2

Title: Inflatable seal with fabric expansion restriction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/020,263 filed Jul. 2, 2014, which is hereby incorporated by references in its entirety. 
    
    
     BACKGROUND 
     The present invention generally relates to diverters and in particular to a diverter flowline seal used in subsea drilling. 
     Installing large diameter elastomeric diverter flowline seals can often be difficult since compressing a substantial amount of rubber into sealing position can require substantial force that is not always available. Also, stabbing an external piston type seal into a bore without damaging the seal or surrounding hardware is difficult when the diameters of the seal and surrounding hardware are equal to or greater than the receiving bore diameter. Unidirectional elastomeric seals such as a lip seal can be used to alleviate stabbing problems since they do not require cross-sectional compression of the elastomeric material by utilizing a lip that can easily be bent inward. However, many seal applications require bidirectional sealing and using two lip seals is not desirable since one lip seal must be stabbed in a direction that could snag the lip. 
     A diverter flowline seal used in subsea drilling that must be stabbed into a mating bore, is an example of a large diameter seal that is difficult to install. A common practice is to use an inflatable seal that, in its preinstalled state, has significant clearance with the mating bore, and when inflated with auxiliary fluid pressure, expands to firmly engage and seal against the bore. This type of seal is easy to install and once inflated provides bidirectional sealing. 
     Conventional diverter flowline seal designs rely on rigid metal end rings partitioned by a bonded elastomeric sealing element which can be slipped onto and retained on a stabbing mandrel. Elastomeric seals such as o-rings form a seal between the inner diameter of the metal rings and the exterior of the stabbing mandrel. A channel within the stabbing mandrel transmits auxiliary fluid pressure between the two end ring seals and inflates the bonded elastomeric section of the flowline seal assembly after the mandrel is stabbed into position. The inflated bonded elastomeric section expands to contact the receiving bore and a bidirectional seal is created between the diverter flowline seal and the receiving bore. An inherent weakness in this design, however, is located at the bonded boundary between the rigid metal end rings and the inflatable elastomeric section. Fatigue at this highly stressed boundary causes bond separation or tearing of the elastomeric sealing element and initiates a leak. 
     Another conventional diverter flowline seal design is shown in U.S. Pat. Nos. 5,890,535 and 6,290,231. The diverter flowline seal design shown in these patents eliminates the potential leakage across the bonded area between the rigid metal end rings and the inflatable elastomeric section by moving the sealing bead of the internal seals that seal off against the stabbing mandrel from the inner diameters of the metal rings to lip seals that are formed within the bonded elastomeric section. Shoulders extending from the rigid metal end rings extend over the internal lip seals and restrict expansion of the lip diameters during inflation. The contrasting material modulus at the boundaries of the rigid metal end rings and the inflatable elastomeric section, however, still creates high stress concentrations with the elastomeric section and can initiate tearing at this boundary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an inflatable seal assembly. 
         FIG. 2  is a cross-sectional view of the inflatable seal assembly of  FIG. 1  installed on a stabbing mandrel. 
         FIG. 3  is a cross-sectional view of the inflatable seal assembly shown in  FIG. 2  installed on a stabbing mandrel and in the condition in which an inflatable elastomeric section has been inflated. 
         FIG. 4  is a cross-sectional view of an inflatable seal assembly similar to that shown in  FIG. 1  with expandable fabric outer corners. 
         FIG. 5  is an enlarged view of a portion of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1 and 2 , a sealing ring  10  is shown which comprises a generally C-shaped elastomeric body  12  having an inner diameter side  14 , and an outer diameter side  16  that form a seal and define a cavity  20  when in contact with a stabbing mandrel  22 . The inner diameter side  14  includes axially inward and diametrically opposed sealing lip portions  18  located adjacent to axially outward and diametrically opposed base portions  24 . One or more layers of a high modulus reinforcing material is integrally molded to the elastomeric body  12  at the base portions  24  at a position adjacent to and axially outward from the sealing lips  18  on the inner diameter side  14  of the elastomeric body  12 . According to several exemplary embodiments, the high modulus reinforcing material has good bonding strength to the elastomeric body  12 . According to several exemplary embodiments, the high modulus reinforcing material has a modulus that is higher than the modulus of the elastomeric material that forms the elastomeric body  12 . According to several exemplary embodiments, the high modulus reinforcing material is a fabric formed from a material used in rubber molding. The term fabric as used with respect to the high modulus reinforcing material of the exemplary embodiments, is used in the broadest sense and includes any cloth or cloth-like structure made by any technique such as knitting, weaving or felting of fibers of natural or synthetic materials as well as mixed fibers and includes, without limitation, fibers of cotton, carbon, Nomex®, nylon, polyester, polyester blends, aramid (aromatic polyamide) fibers, fiberglass fibers or a metallic band or any combination thereof. According to several exemplary embodiments, the high modulus reinforcing material is wrapped in a hoop orientation which minimizes radial expansion of the high modulus reinforcing material when the inner cavity  20  of the sealing ring  10  is pressurized as will be discussed below in connection with  FIG. 3 . Those of ordinary skill in the art will recognize that the number of layers of high modulus reinforcing material needed to restrict radial expansion of the inner diameter side  14  of the elastomeric body  12  is related to the modulus of the high modulus reinforcing material, the modulus of the elastomeric body, the diameter of the flowline seal, and the proportions of the elastomeric body. 
     Referring to  FIG. 5  a sealing ring  10  is shown which includes a seal body  12  having a generally C-shaped cross section, the seal body  12  having an inner diameter end  14 , an opposite outer diameter end  16 , and first and second side ends  44 ,  44 ′. The seal body  12  is formed of an inflatable elastomeric material having a first modulus and the inner diameter end  14  of the seal body  12  includes diametrically opposed first and second axially inward lip portions  18 ,  18 ′ and diametrically opposed first and second axially outward base portions  24 ,  24 ′. As shown in  FIG. 5 , the inner diameter end  14  and the outer diameter end  16  have approximately equal axial dimensions. Each of the first and second side ends  44 ,  44 ′ has a first end  46 ,  46 ′ adjacent a corresponding one of the base portions  24 ,  24 ′ of the inner diameter end  14  of the seal body  12 , and a second end  48 ,  48 ′ adjacent the outer diameter end  16  of the seal body  12 . The seal body  12  defines an inner region  20  into which fluid pressure is adapted to be delivered to inflate the inflatable elastomeric material having the first modulus. As depicted in  FIG. 5 , an interface boundary  66  is defined between the seal body  12  and the inner region  20  such that the inflatable elastomeric material having the first modulus, and the inner region  20  together define the generally C-shaped cross section of the seal body  12 . Also, the inflatable elastomeric material having the first modulus extends uninterruptedly throughout the generally C-shaped cross section of the seal body  12 . Accordingly, due to the uninterrupted extension of the inflatable elastomeric material throughout the generally C-shaped cross section of the seal body  12 , the inflatable elastomeric material having the first modulus extends uninterruptedly along the interface boundary  66  in its entirety between the seal body  12  and the inner region  20 , and thus the inflatable elastomeric material having the first modulus is adjacent the inner region  20  along the interface boundary  66  in its entirety between the seal body  12  and the inner region  20 . 
     With continuing reference to  FIG. 5 , the diametrically opposed first and second axially outward base portions  24 ,  24 ′ include first and second recesses  50 ,  50 ′ formed in the seal body  12 , and each of the first and second recesses  50 ,  50 ′ define a radially-extending surface  52 ,  52 ′ and an axially-extending surface  54 ,  54 ′. The first and second recesses  50 ,  50 ′ are axially spaced from each other, while the radially-extending surfaces  52 ,  52 ′ of the first and second recesses  50 ,  50 ′ are axially spaced from each other in a parallel relation, and the axially-extending surfaces  54 ,  54 ′ of the first and second recesses  50 ,  50 ′ are axially spaced from each other and are coaxial with each other. The axially-extending surface  54  defined by the first recess  50  extends from the radially-extending surface  52  defined by the first recess  50  to the first end  46  of the first side end  44 , and thus the axially-extending surface  54  defined by the first recess  50  is adjacent the first end  46  of the first side end  44 . Also, the axially-extending surface  54 ′ defined by the second recess  50 ′ extends from the radially-extending surface  52 ′ defined by the second recess  50 ′ to the first end  46 ′ of the second side end  44 ′, and thus the axially-extending surface  54 ′ defined by the second recess  50 ′ is adjacent the first end  46 ′ of the second side end  44 ′. 
     As shown in  FIG. 5 , a first layer of reinforcing material  56  having a second modulus that is higher than the first modulus is integrally molded to the seal body  12  at the first axially outward base portion  24 . The first layer of reinforcing material  56  is disposed within the first recess  50  such that the first layer of reinforcing material  56  extends from the radially-extending surface  52  defined by the first recess  50  to the first end  46  of the first side end  44  of the seal body  12 . The first layer of reinforcing material  56  defines first and second faces  58 ,  58 ′ spaced axially and in a parallel relation and first and second surfaces  60 ,  60 ′ spaced radially and in a concentric relation. Each of the first and second surfaces  60 ,  60 ′ of the first layer of reinforcing material  56  extends from the first face  58  of the first layer of reinforcing material  56  to the second face  58 ′ of the first layer of reinforcing material  56 . The first face  58  defined by the first layer of reinforcing material  56  is approximately axially aligned with the first side end  44  of the seal body  12  and the second face  58 ′ defined by the first layer of reinforcing material  56  contacts the radially-extending surface  52  defined by the first recess  50 . The first surface  60  of the first layer of reinforcing material  56  contacts the axially-extending surface  54  defined by the first recess  50  and the second surface  60 ′ of the first layer of reinforcing material  56  is radially positioned between the axially-extending surface  54  defined by the first recess  50  and at least a portion of the first axially inward lip portion  18  of the seal body  12 . 
     As also shown in  FIG. 5 , a second layer of reinforcing material  56 ′ having the second modulus is integrally molded to the seal body  12  at the second axially outward base portion  24 ′. The second layer of reinforcing material  56 ′ is disposed within the second recess  50 ′ and the second layer of reinforcing material  56 ′ is axially spaced from the first layer of reinforcing material  56  in a parallel relation. The second layer of reinforcing material  56 ′ extends from the radially-extending surface  52 ′ defined by the second recess  50 ′ to the first end  46 ′ of the second side end  44 ′ of the seal body  12 . The second layer of reinforcing material  56 ′ defines first and second faces  62 ,  62 ′ spaced axially and in a parallel relation and first and second surfaces  64 ,  64 ′ spaced radially and in a concentric relation. Each of the first and second surfaces  64 ,  64 ′ of the second layer of reinforcing material  56 ′ extends from the first face  62  of the second layer of reinforcing material  56 ′ to the second face  62 ′ of the second layer of reinforcing material  56 ′. The first face  62  defined by the second layer of reinforcing material  56 ′ is approximately axially aligned with the second side end  44 ′ of the seal body  12  and the second face  62 ′ defined by the second layer of reinforcing material  56 ′ contacts the radially-extending surface  52 ′ defined by the second recess  50 ′. The first surface  64  of the second layer of reinforcing material  56 ′ contacts the axially-extending surface  54 ′ defined by the second recess  50 ′ and the second surface  64 ′ of the second layer of reinforcing material  56 ′ is radially positioned between the axially-extending surface  54 ′ defined by the second recess  50 ′ and at least a portion of the second axially inward lip portion  18 ′ of the seal body  12 . 
     As shown in  FIG. 2 , the sealing ring  10  is installed on a stabbing mandrel  22  which is typically formed of steel. The stabbing mandrel  22  includes a shoulder  26  which supports the sealing ring  10  on one side and a rigid ring  28  held by a retaining ring  30  which supports the other side of the sealing ring  10 . The stabbing mandrel  22  includes a passage  32  which is in fluid communication with the inner cavity  20  of the sealing ring  10 . 
     Referring now to  FIG. 3 , when the sealing ring  10  is pressurized, fluid pressure is delivered from the passage  32  to the inner cavity  20  and is sealably trapped within the inner cavity  20  by the sealing lip portions  18 . Also, upon pressurization, the elastomeric body  12  expands radially outward to sealably contact the receiving bore  34  of surrounding hardware. The high modulus reinforcing material that is integrally bonded with the elastomeric body  12  keeps the sealing lip portions  18  and the base portions  24  of the inner diameter side  14  of the elastomeric body  12  in contact with the stabbing mandrel  22 , especially when pressure is low and the pressure acting on the sealing lip portions  18  is insufficient to overcome the tension from the inflatable elastomeric body  12 . With the internal fluid pressure from passage  32  radially expanding the elastomeric body  12  so that the outer diameter side  16  engages the receiving bore  34 , fluid pressure in annuli  38 , 40  formed between the stabbing mandrel  22  and the receiving bore  34  cannot pass the sealing ring  10  unless the annuli pressure exceeds the fluid pressure in the internal cavity  20 . 
     With further reference to  FIG. 3 , when the sealing ring  10  is pressurized, fluid pressure delivered from the passage  32  to the inner cavity  20  causes the inflatable elastomeric body  12  to expand, such that portions  42  move into the annuli  38 , 40 . 
     With continuing reference to  FIG. 3 , upon pressurization, the outer diameter side  16  of the sealing ring  10  expands to meet the receiving bore  34 . Typically the receiving bore  34  has approximately a ¼ inch of diametrical clearance with the sealing ring  10  so the radial distance travelled by the expanding sealing ring  10  is about ⅛ of an inch. Without the high modulus reinforcing material, a substantial void would form behind the sealing lip portions  18  of the inner diameter end  14  of the elastomeric body  12 . As a result, the sealing lip portions  18  would tend to break sealable contact with the stabbing mandrel  22 , especially at lower pressures when the pressure exerted on the sealing lip portions  18  is not sufficient to overcome the tension from the inflatable elastomeric body  12 . This is caused by the tension from the inflatable elastomeric body  12  lifting the sealing lip portions  18  away from the stabbing mandrel  22  before the internal fluid pressure in the cavity  20  can adequately force the sealing lip portions  18  into the stabbing mandrel  22 . Even if the sealing lip portions  18  did maintain sealable contact with the stabbing mandrel  22  at lower pressures (below 100 psi), the high internal pressure (potentially thousands of pounds per square inch) in the cavity  20  could invert or blow out the sealing lip portions  18  into the void. According to several exemplary embodiments, the high modulus reinforcing material located at the base portions  24  adjacent the sealing lip portions  18  at the inner diameter end  14  of the sealing ring  10  assist the sealing lip portions  18  in maintaining contact with the stabbing mandrel  22  and also provide back-up support to keep the sealing lip portions  18  from blowing outward. 
       FIG. 4  shows a sealing ring  100  that is similar to the inflated sealing ring  10  shown in  FIG. 3  but with the inclusion of fabric  108  supporting the elastomeric body  102  and preventing it from extruding into annuli  110 , 112 . Specifically, the fabric  108  is located at a junction portion  114  between a side end  116  and the outer diameter side  118  of the elastomeric body  102  and at a junction portion  120  between a side end  122  and the outer diameter side  118  of the elastomeric body. According to several exemplary embodiments, the fabric  108  is allowed to stretch by either being composed of a low modulus material or oriented to allow expansion. This is in contrast to the high modulus reinforcing material  106  that is wrapped in hoop orientation to restrict expansion. 
     As can be readily seen from the foregoing, principles of the present invention provide an inflatable seal assembly that includes high modulus reinforcing material integrated with an elastomeric seal to restrict expansion of the inner diameter side of the elastomeric seal so that sealing contact is maintained on the inner diameter side of the elastomeric seal even after the seal is inflated and the outer diameter side of the elastomeric seal is expanded. The integration of high modulus reinforcing material as a composite with the elastomeric material eliminates stress concentrations that are present with an elastomeric seal having rigid metal end rings bonded to the elastomeric expandable seal. 
     As can also be readily seen from the foregoing, principles of the invention also provide an inflatable seal assembly that includes one or more layers of a calendared fabric material positioned on the inner diameter side of the seal. Adjacent to the layers of the calendared fabric material towards the interior of the seal are two opposing lips that diametrically interfere with a stabbing mandrel and form a sealed cavity within which auxiliary fluid pressure can be injected. The layers of calendared fabric material can be bonded to the elastomer with a calendared rolling process and then can be molecularly cured to the homogeneous body of the seal. The layers of the calendared fabric material have an improved bonded surface due to the high modulus fibers in the fabric, and upon inflation of the seal, the outward radial elastomeric section of the seal is free to expand. 
     According to several exemplary embodiments of the present invention, the inflatable seal assembly includes an elastomeric body that is free to deform during expansion without initiating high stresses at bonded radially extending surfaces. The interior sealing lips are kept tightly in contact with the stabbing mandrel to maintain the seal of the interior cavity seal during inflation. 
     According to several exemplary embodiments of the present invention, the inflatable seal assembly does not include a metal component in contact with the mandrel surfaces so that the possibility of damage to the stabbing mandrel or sealing bore during assembly or pressurization is avoided. 
     According to several exemplary embodiments of the present invention, the inflatable seal assembly includes calendared fabric that is fashioned on a bias that allows expansion. According to such embodiments, the fabric can be used as an anti-extrusion device. Also, according to several exemplary embodiments, fabric designed for expansion is molded within the exterior corners of the seal which can help prevent extrusion after the seal is inflated. 
     The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.