Abstract:
A threaded union includes a threaded union nut configured to couple abutting ends of a threaded nipple on a distal end of a first joint and a shouldered nipple on a distal end of a second joint and a lower wedge and an upper wedge positioned within an offset distance formed between a lower surface of the union nut and an upper surface of an enlarged section of the shouldered nipple.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of a provisional application under 35 U.S.C. §119(e), namely U.S. Patent Application Ser. No. 61/374,121 filed on Aug. 16, 2010, which is incorporated by reference in its entirety herein. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     Embodiments disclosed herein relate generally to the use of threaded unions, particularly so-called “hammer unions.” More specifically, the current disclosure relates to apparatus and method for locking threaded unions in a made-up condition, especially hammer unions subject to vibration or impacts, or which are located in inaccessible areas. 
     2. Background Art 
     Threaded unions, particularly “hammer” unions, are commonly used in petroleum exploration and production to join conduits together, for example, conduits carrying high-pressure fluids such as drilling mud, fracturing fluids, and oil and gas produced incidental to drilling activities. Hammer unions are generally considered to be economical, simple, reliable, and robust, and very easy to make-up and break-out quickly. Examples of hammer unions include, but are not limited to, the WECO® brand hammer unions available from FMC Technologies of Houston, Tex. 
     Typically, hammer unions are used in more temporary situations, such as joining together sections of joints (e.g., Chicksan® joints) used for pumping fracturing fluids into a wellbore under high pressure. In these applications, hammer unions rarely loosen (or “back-off”) in service because the duration of the application is so short. However, hammer-unions may also be used in certain long-term applications for their ease of make-up and break-out, especially, for example, for equipment that may need to be replaced quickly and efficiently (e.g., rotary hoses for conveying drilling mud between a stand-pipe manifold and a rotary swivel or top drive, or components of a choke manifold, such as valves, chokes and spools, which may fail unexpectedly due to erosive flows). In these longer-term applications, there may be a need to ensure that the hammer union does not loosen during service. 
     Several locking mechanisms for threaded unions are described in the prior art, for example: U.S. Pat. No. 4,501,521, disclosing a castellated locking fastener assembly, U.S. Pat. No. 6,139,068, disclosing a union lock for maintaining a union between two conduits, and U.S. Pat. Nos. 7,258,372 and 7,201,404 (by the same inventor) disclosing a union nut with lock members. Locking mechanisms for quick-disconnect fittings are also known in the prior art, for example, U.S. Pat. No. 5,374,085, which discloses a mechanical locking device for use with conventional quick-disconnect fluid couplings. 
     Hammer unions typically include three major parts: a shouldered nipple, a union nut, and a threaded nipple. The hammer union is typically made-up and broken-out by applying a sledge hammer to radial lugs on the union nut. Refer now to  FIG. 1A , a cross-sectional view of a conventionally made-up hammer union with a spherical metal-to-metal pressure seal is shown. Other types of pressure seals are possible, including those having elastomeric or composite seals, especially for (relatively) low working-pressure unions. Union nut  1  has hammer lugs  1 A, internal threads  1 B and flat surface  1 C. Union nut  1  bears on shoulder  2 A on a distal end of shouldered nipple  2 , which also has sealing surface  2 C and outer diameter  5 . Threaded nipple  3  has external threads  3 A and sealing surface  3 B. 
       FIG. 1B  shows a perspective view of a hammer union with an external shoulder, which in this example is a hose ferrule for attaching the union to high pressure flexible hose. The hammer union comprises union nut  1  with hammer lugs  1 A and flat surface  1 C, shouldered nipple  2 , and threaded nipple  3 . In this example, which is typical of many applications on drilling rigs, shouldered nipple  2  has an enlarged section  2 D (in this example, a hose ferrule) with transition profile  2 E and external shoulder  2 F. Transition profile  2 E may be a constant or variable radius fillet or a chamfer, or another profile known in the art. Below union nut  1 , shouldered nipple  2  has outer diameter  5 . In the made-up condition, union nut  1  is separated from shoulder  2 F by offset distance  4 , which is typically designed to allow union nut  1  to drop down, exposing sealing surface  2 C of shouldered nipple  2  (shown in  FIG. 1A ) so that it may be cleaned and inspected. 
     Other prior-art hammer union configurations include a union nut separated by an offset distance from an external shoulder, including valve bodies, hydraulic wyes, crosses and manifolds. Still other prior-art hammer union configurations may include a union nut separated by an offset distance from a small external shoulder or groove, while other prior-art hammer union configurations may include a shouldered nipple with a constant external diameter, that is, without external shoulders or grooves. Accordingly, there exists a need for a locking mechanism for a threaded union in a made-up condition that may be quickly installed on existing threaded unions. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, embodiments disclosed herein relate to a threaded union including a threaded union nut configured to couple abutting ends of a threaded nipple on a distal end of a first joint and a shouldered nipple on a distal end of a second joint and a lower wedge and an upper wedge positioned within an offset distance formed between a lower surface of the union nut and an upper surface of an enlarged section of the shouldered nipple. 
     In other aspects, embodiments disclosed herein relate to a locking mechanism for a threaded union, the locking mechanism including a lower wedge and an upper wedge positioned within an offset distance formed between a lower surface of a union nut and an upper surface of an enlarged section of a shouldered nipple, and at least one mechanical fastener configured to urge the lower wedge and the upper wedge together, wherein the lower and upper wedges are urged together to create an axial force against the lower surface of the union nut and the upper surface of the enlarged section. 
     In other aspects, embodiments disclosed herein relate to a method to lock a union nut of a threaded union, the method including threading the union nut over abutting ends of a threaded nipple and a shouldered nipple, mating a lower wedge with an upper wedge within an offset distance formed between a lower surface of the union nut and an upper surface of an enlarged section of the shouldered nipple, urging the lower and upper wedges together, and generating axial forces against the lower surface of the union nut and the upper surface of the enlarged section of the shouldered nipple. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  shows a cross-sectional view of a conventional hammer union with a spherical metal-to-metal pressure seal. 
         FIG. 1B  shows a perspective view of a conventional hammer union with an external shoulder. 
         FIGS. 2A and 2B  show exploded perspective views of a locking mechanism in accordance with one or more embodiments of the present disclosure. 
         FIGS. 3A-3C  show perspective views of a locking mechanism installed on a threaded union in accordance with one or more embodiments of the present disclosure. 
         FIG. 4  shows a perspective view of a locking mechanism installed on a threaded union in accordance with one or more embodiments of the present disclosure. 
         FIG. 5  shows a perspective view of a locking mechanism installed on a threaded union in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In one aspect, embodiments disclosed herein relate to a locking mechanism that may be installed onto a made-up threaded union to prevent the threaded union from loosening. 
     Referring to  FIG. 2A , an exploded perspective view a locking mechanism in accordance with one or more embodiments of the present disclosure is shown. The locking mechanism includes a lower wedge  20  having a horizontal surface  20 A and inclined surface  20 B, which are separated by wedge angle  20 F. Lower wedge  20  may also have an elongated groove  20 C with a groove width  20 G, cut into a pointed end  20 H of the lower wedge  20 . Oval through-holes  20 D may be substantially parallel to horizontal surface  20 A. Elongated groove width  20 G may be slightly larger than outer diameter  5  of the shouldered nipple  2  (shown in  FIGS. 1A and 1B ). Profiled edge  20 E between elongated groove  20 C and horizontal surface  20 A is configured to fit transition profile  2 E shown in  FIG. 1B . 
     Further, the locking mechanism includes an upper wedge  21  having a horizontal surface  21 A and an inclined surface  21 B, which are separated by wedge angle  21 F. Upper wedge  21  may also have an elongated groove  21 C with a groove width  21 G, cut into a pointed end  21  H of the upper wedge  21 . Elongated groove width  20 G may be slightly larger than outer diameter  5  of the shouldered nipple  2 . Profiled edge  21 E between elongated groove  21 C and horizontal surface  21 A (like profiled edge  20 E described above) is shown as a relieved or “rabbetted” edge configured to fit over a snap-ring (not shown), which is commonly fitted beneath union nut  1  in  FIGS. 1A and 1B . While the lower wedge  20  and upper wedge  21  are shown substantially rectangular in a plan view, those skilled in the art will understand other shapes in which the lower and upper wedges  20 ,  21  may be configured as shown in plan view, for example, round. 
     Those having ordinary skill in the art will recognize that profiled edges  20 E and  21 E may have different profiles than shown in the figures, for example, to best conform to a particular transition profile. In certain embodiments, lower wedge  20  may have profiled edge  20 E that is radiused to substantially match a particular transition profile, and upper wedge  21  may have profiled edge  21 E hat is rabbetted. In other embodiments, only one of lower wedge  20  and upper wedge  21  may have a profiled edge. In yet further embodiments, neither lower wedge  20  nor upper wedge  21  may have a profiled edge. 
     Lower wedge  20  and upper wedge  21  may be mated at inclined surfaces  20 B and  21 B and urged together by mechanical threaded fasteners, such as hex headed cap screws  23 , washers  23 A and nuts  23 B, passing through oval through-holes  20 D and  21 D. Those skilled in the art will appreciate other fasteners that may be used to urge together the lower wedge  20  and upper wedge  21 , such as, for example, spherical nuts embedded in one wedge, or adjustable cam-type clamps in lieu of threaded fasteners. 
     Wedge angles  20 F and  21 F may be substantially the same such that when the wedges are mated at inclined surfaces  20 B and  21 B, horizontal surfaces  20 A and  21 A may be substantially parallel. In certain embodiments, wedge angles  20 F and  21 F may be between about  15  and  21  degrees. In other embodiments, wedge angles  20 F and  21 F may be about  18  degrees.  FIG. 2B  shows the underside of the lower and upper wedges  20 ,  21  shown in  FIG. 2A , more clearly showing elongated grove  20 C and profiled edge  20 E of lower wedge  20 , and elongated groove  21 C and profiled edge  21 G of upper wedge  21 . 
     Referring now to  FIGS. 3A-3C , perspective views of the locking mechanism as installed onto a threaded union in accordance with one or more embodiments disclosed herein are shown. The made-up threaded union includes a union nut  1  with hammer lugs  1 A and a flat surface  1 C, shouldered nipple  2  with an external shoulder  2 F and outer diameter  5 , and a threaded nipple  3 . Lower wedge  20  is disposed around shouldered nipple  2  between flat surface  1 C of union nut  1  and external shoulder  2 F of shouldered nipple  2  such that elongated groove  20 C is substantially concentric with outer diameter  5 . Lower wedge  20  and upper wedge  21  are mated at inclined surfaces  20 B and  21 B such that elongated groove  21 C may be substantially concentric to outer diameter  5  and horizontal surfaces  20 A and  21 A are substantially parallel. As shown, lower and upper wedges  20 ,  21  are disposed within an offset distance  4 , which is formed between a lower surface  1 C of the union nut  1  and an upper surface  2 F of enlarged section  2 D. Lower wedge  20  and upper wedge  21  may be urged together by threaded fasteners (including hex headed cap screws,  23 ), such that horizontal surfaces  20 A and  21 A bear on external shoulder  2 F and flat surface  1 C respectively. 
     In certain embodiments, wedge angles  20 F and  21 F of lower and upper wedges  20 ,  21 , respectively, may be between about 15 and 21 degrees and lower and upper wedges  20 ,  21  may be urged together with a total force of between 3,000 and 5,000 lbs force (force applied by mechanical fasteners). In other embodiments, the lower and upper wedges  20 ,  21  may be urged together until they apply a total force on external shoulder  2 F and flat surface  1 C (substantially along the axis of the hammer union) of between about 5,000 and 15,000 pounds force. In still further embodiments, wedge angles  20 F and  21 F of lower and upper wedges  20 ,  21 , respectively, may be about  18  degrees and the lower and upper wedges  20 ,  21  may be urged together until they apply a substantially axial force of about 9,000 lbs on external shoulder  2 F and flat surface  1 C. 
     Lower and upper wedges  20 ,  21  may be made from a number of materials known in the art. In certain embodiments, lower and upper wedges  20 ,  21  may be made from an aluminum alloy. In other embodiments, the lower and upper wedges  20 ,  21  may be made from thermoplastic, for example, high density polyethylene. In certain embodiments, at least one of the wedges may include a resilient material such that when the wedges are urged together, a spring force may exist normal to the horizontal surfaces  20 A and  21 A. For example, lower wedge  20  may include aluminum with a resilient elastomeric pad (e.g., high durometer rubber or urethane) on horizontal surface  20 A. Thus, when the lower and upper wedges  20 ,  21  are urged together, the resilient elastomeric pad may compress, thereby creating a residual spring force normal to the horizontal surfaces  20 A and  21 A. In further embodiments, at least one of the wedges includes alternating layers of resilient and non-resilient materials. In still further embodiments, at least one of horizontal surfaces  20 A and  21 A may include a high friction surface configured to impede rotation of the union nut  1  ( FIG. 3A ). For example, the high friction surface may include, but is not limited to, an elastomeric surface, an abrasive surface, and a grooved surface. 
     Referring now to  FIG. 4 , a perspective view of a locking mechanism installed on a threaded union in accordance with one or more embodiments of the present disclosure is shown. Threaded union includes union nut  1  with hammer lugs  1 A, shouldered nipple  2 , and threaded nipple  3 . Lower wedge  20  and upper wedge  21  are mated at inclined surface  20 B and  21 B and urged together with threaded fasteners, which include cap screws  23 , washers  23 A and nuts  23 B. In certain embodiments, upper wedge  21  may include a lug nub  21 H, which protrudes from horizontal surface  21 A and may bear on one or more hammer lugs  1 A to prevent rotation of union nut  1 . Lug nub  21 H may be an integral part of upper wedge  21  (as shown), or may be a separate part attached to upper wedge  21  (as with threaded fasteners or by other means known in the art). Nub  21 H may be substantially arcuate to conform to union nut  1 , or may be other shapes. In certain embodiments, upper wedge  21  may have one or more holes (not shown) drilled and tapped in horizontal surface  21  to accommodate, for example, threaded dowels or similar to serve as lug nubs. 
     Methods of installing the locking mechanism shown in  FIG. 4  onto a made-up threaded union in accordance with embodiments disclosed herein may proceed as follows. The lower wedge  20  and the upper wedge  21  are assembled on the made-up threaded union between the union nut flat surface  1 C and a shoulder  2 F with mechanical fasteners  23 . The assembled wedges may be rotated in the make-up direction (i.e., the direction in which the threaded union nut  1  is rotated for tightening) until one or more nubs  21 H ( FIG. 4 ) on horizontal surface of the upper wedge  21  are in contact with a hammer union lug  1 A. At this point, the lower and upper wedges  20 ,  21  may be tightened about the threaded union by urging the wedges together with the mechanical fasteners  23 . 
     Referring now to  FIG. 5 , a perspective view of a locking mechanism installed on a threaded union in accordance with one or more embodiments of the present disclosure is shown. Threaded union includes union nut  1  with radial lugs  1 A, shouldered nipple  2 , and threaded nipple  3 . However, in certain instances, the threaded union may not have an external shoulder  2 F (shown in  FIG. 1B ) on shouldered nipple  2  for the wedges to wedge between. Instead, lower and upper wedges  20 ,  21  may be urged into place by threaded fasteners (comprising cap screws  23 , washers  23 A and nuts  23 B) between union nut  1  and a split collar  50 . 
     Split collar  50  includes half collars  50 A and  50 B joined together by socket-headed cap screws  50 C. Collars of other designs known in the art may be used, including multi section collars or collars which lock circumferentially. In all cases, the selected collar must be capable of resisting the axial thrust imparted by lower wedge  20  and upper wedge  21 . In certain embodiments, a shallow groove on shouldered nipple  2  may be fit with a split collar, which fits into the shallow groove. In other embodiments, a small external shoulder on shouldered nipple  2  may be fit with split rings bearing on the small shoulder and a retaining collar which may be placed over the end of the shouldered stub to retain the split rings and to provide a surface to carry the axial thrust imparted by the wedges. 
     Methods of installation of the locking mechanism shown in  FIG. 5  include fitting the threaded union with a split collar  50  located at a known axial distance from the made-up union nut. After the split collar is installed, the lower and upper wedges  20 ,  21  may be assembled on the made-up threaded union between the union nut  1  and the split collar  50  with mechanical fasteners  23 . 
     Advantageously, embodiments of the present disclosure provide locking mechanism that may be installed onto made-up threaded unions, or hammer unions, to prevent the union nut from backing off over longer periods of use that the threaded union may experience. In addition, the locking mechanism of embodiments disclosed herein may be quickly and easily installed onto the made-up threaded union. The locking mechanism reduces installation time while adding reliability to the threaded union. 
     While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.