Abstract:
An automatic locking mechanism for a telescoping joint for a riser functions in several modes. In an operating mode, the joint is free to have its inner and outer barrels move with respect to each other without engaging each other in a locking relationship. In a second position, the telescoping joint locks when it is fully retracted. In a third position, the system locks the inner and outer barrels together to hold them in a fixed position. The inner and outer barrels are locked when a movable sleeve is properly positioned to allow spring-loaded dogs to be biased through windows in the sleeve so as to act as a landing shoulder to catch a groove on the outer barrel. By putting the actuating sleeve in a variety of positions, the various modes of the locking assembly can be deployed.

Description:
FIELD OF THE INVENTION 
     The field of this invention relates to selective locking systems for telescoping joints in offshore riser systems. 
     BACKGROUND OF THE INVENTION 
     Riser systems are used in offshore systems to connect surface equipment to the BOP stack mounted subsea on the wellhead. The telescoping joint compensates for movement of the surface equipment due to wave action. Conditions arise when the telescoping joint needs to be in a locked position. One such situation can occur during times of bad weather when the riser is disconnected from the BOP stack and is freely suspended above the BOP stack. Other operating conditions may dictate that when the telescoping joint strokes to its retracted position that it be automatically locked. Other situations may arise where the telescoping joint needs to be locked in its retracted position where its overall length is the shortest. These situations occur when the joint is being transported or stored. 
     In the past, when it has been desirable to lock the telescoping joint of a riser system, a manual operation was required. Thus, bolts having eccentric lugs on one part of the joint would have to be turned with tools to orient the eccentrically mounted lug into a groove on another part of the joint so as to hold the telescoping joint in a retracted position. Dual packer assemblies made by Cooper Cameron Corporation included this feature. The problem with doing this was that the riser system is in a relatively inaccessible area known as the “moonpool” of the surface rig. Thus, operating personnel had to be hoisted to obtain access to the various bolts and try to rotate them while suspended adjacent to them in a sling. This procedure was difficult to accomplish and involved certain risks from a safety standpoint. 
     Different types of connections for other applications involving hydraulic assist for make-up have been used. Cooper Cameron makes an HC collet connector which employs hydraulic cylinders moving a sleeve to cam a grooved collet to catch a groove on the collet around mating flange connections of a joint to hold the joint together. Other connectors are illustrated in U.S. Pat. Nos. 4,348,039; 4,372,584; 4,632,432; 4,854,777; 5,163,783; 5,462,121; 5,692,564; 5,718,291. 
     What these connections lack is a simple design which can support extremely high loads and be adjusted easily for different modes of operation. The prior designs, specific to the application of telescoping joints for risers, involved manual operations which were time-consuming and presented risks to personnel. Thus, one of the objects of the present invention is to provide a simple system which can accommodate a variety of situations without the need of close access to the telescoping joint by personnel within the moon-pool. Another objective of the present invention is to provide a design which will accommodate the high loads required, while at the same time be easily positionable in multiple positions where either normal operations can take place, or the telescoping joint is locked in a retracted position, or that the telescoping joint locks if it reaches a fully retracted position during normal operations. 
     These and other advantages will become apparent to those skilled in the art from a review of the preferred embodiment described below. 
     SUMMARY OF THE INVENTION 
     An automatic locking mechanism for a telescoping joint for a riser functions in several modes. In an operating mode, the joint is free to have its inner and outer barrels move with respect to each other without engaging each other in a locking relationship. In a second position, the telescoping joint locks when it is fully retracted. In a third position, the system locks the inner and outer barrels together to hold them in a fixed position. The inner and outer barrels are locked when a movable sleeve is properly positioned to allow spring-loaded dogs to be biased through windows in the sleeve so as to act as a landing shoulder to catch a groove on the outer barrel. By putting the actuating sleeve in a variety of positions, the various modes of the locking assembly can be deployed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional elevational view with the actuating sleeve in the position where the telescoping joint will lock on full retraction, showing the position of the dogs extending through the actuating sleeve. 
     FIG. 2 is the view of FIG. 1, showing the outer barrel assembly displacing the dogs through the windows of the actuating sleeve. 
     FIG. 3 is the view of FIG. 2, showing the biased dogs falling into a groove in the connector at the end of the outer barrel assembly. 
     FIG. 4 is the view of FIG. 3, showing the dogs fully locked in a groove in the outer barrel assembly. 
     FIG. 5 is the view of FIG. 4, with the actuating sleeve shifted down to lock the dogs in position, trapping the outer barrel assembly. 
     FIG. 6 is the view of FIG. 1, with the actuating sleeve in an upward position, precluding the dogs from entering the window. 
     FIG. 7 is a section view of the locking assembly, with the dogs extending through the window. 
     FIG. 8 is the outside view of FIG. 7, showing the hydraulic cylinders. 
     FIG. 9 is a detailed view of the dogs displaced out of the window against the force of a spring. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a housing  10  supports the inner barrel  12  which is telescopically movable inside the outer barrel  14 . The outer barrel  14  terminates in a specially designed male end connector  16 . Connector  16  has a tapered camming shoulder  18  and a groove  20 , which comprises of tapered surface  22 , cylindrical surface  24 , and radial surface  26 . As shown in FIG. 4, the surfaces  22 ,  24 , and  26  accept a dog  28 , as will be described in more detail below. 
     The housing  10  includes an actuating sleeve  30  which has a series of windows or openings  32  around its periphery. In the preferred embodiment, the sleeve  30  has a pair of lugs  34  at 180° separation. Each of the lugs  34  is attached to a fitting  36  which accepts a shaft (not shown) extending from a hydraulic cylinder  38 . The cylinders are remotely actuated by a control system panel  39  (see FIG.  8 ). Thus, in the preferred embodiment, a pair of hydraulic cylinders  38  is connected respectively to a fitting  36  to move opposed lugs  34  upwardly or downwardly into three different positions for the sleeve  30 . The three separate positions of sleeve  30  are illustrated, respectively, in FIGS. 1,  5 , and  6 . The position in FIG. 1 is intermediate to the positions in FIGS. 5 and 6. 
     Referring again to FIG.  1  and to dogs  28 , it can be seen that each of them has a loading surface  40  which, when it extends into window  32  below radial surface or shoulder  26  of end connector  16 , will allow the locking connection L to remain in the fully retracted position where the inner barrel  12  is retracted to the maximum into the outer barrel  14 . 
     The dogs  28 , as seen in FIG. 9, are biased toward the position shown in FIG. 5 by a spring  42  which, coupled with the weight distribution of dogs  28 , results in the weight of dogs  28  also acting to move dogs  28  about pin  44  to the FIG. 5 position. In essence, the center of gravity is to the right of pin  44 , as shown in FIG.  9 . Adjacent the loading surface  40  is a cylindrical surface  46  which can be engaged by the top of the window  32  of actuating sleeve  30 , as shown in FIG. 5, so as to fully lock the inner barrel  12  to the outer barrel  14 . Those skilled in the art will appreciate that the hydraulic cylinders  38  have been actuated to move the sleeve  30  into its most downward position with the dogs  28  extending through the windows  32  and further into groove  20  of end connector  16 . When the actuating sleeve  30  is brought down to the position of FIG. 5 with the dogs  28  into groove  20  of end connector  16 , the cylindrical surface  46  is locked inside the actuating sleeve  30 ; thus, the dogs  28  cannot be rotated about pin  44  when the sleeve  30  is in the position of FIG.  5 . 
     FIGS. 1-4 illustrate the normal operation of the locking connection L if it is desired to have the connection L lock automatically when the inner barrel  12  is fully retracted into the outer barrel  14 . The sequence begins with FIG. 1, as relative movement between the inner barrel  12  and the outer barrel  14  begins. The outer barrel moves up and/or the inner barrel moves down to lock connection L. Eventually, shoulder  18  engages surface  48  of dogs  28 . Further retraction of the inner barrel  12  into the outer barrel  14  allows shoulder  18  to cam the dogs  28  about their respective pivots  44  against the force of spring  42 . This movement is shown in FIG. 2, indicating that the shoulder  18  has now moved completely past dogs  28 , bringing groove  20  into alignment with the spring-loaded dogs  28 . Further relative movement of the inner barrel  12  into the outer barrel  14  forces the end connector  16  into contact with housing  10  at its top surface  50 . In that position, the groove  20  on end connector  16  has moved somewhat past the dogs  28  such that surface  48  of dogs  28  is now resting on tapered surface  22  of groove  20 . FIG. 4 now shows what happens upon further relative movement of the inner barrel  12  out of the outer barrel  14 . The bias of spring  42  pulls the dogs  28  into groove  20  while being supported by the lower edge of the window  32 , preventing further outward movement of inner barrel  12  with respect to outer barrel  14 , as shown in FIG.  4 . 
     As previously stated, the locked position of the inner barrel  12  to the outer barrel  14  can be secured by operation of hydraulic cylinders  38 , with the components illustrated in the position of FIG.  4 . Upon downwardly shifting the sleeve  30  with the dogs  28  fully inserted into groove  20 , the top of window  32  engages the cylindrical surface  46 , thus preventing any rotational movement of the dogs  28 . 
     FIG. 6 illustrates the sleeve  30  placed into its upwardmost position by hydraulic cylinders  38 , which brings window  32  up to the point where dogs  28 , under the force of springs  42 , cannot pivot sufficiently to present any portion of loading surface  40  within the sleeve  30 . In the position shown in FIG. 6, during normal operations the inner barrel  12  will telescope into and out of the outer barrel  14  without ever locking to it because the dogs  28  are disabled. 
     Those skilled in the art can now appreciate the three different positions to meet different conditions of the locking joint L for a riser system. For transport or during storms where the riser system is disconnected from the BOP stack, it is desirable to put the locking connection L into the fully locked position shown in FIG.  5 . The locking connection L is strong enough to support the BOP stack if it is disconnected from the wellhead but connected to the riser. To accomplish locking, the inner barrel  12  is telescoped fully into the outer barrel  14 , with the sleeve  30  in the position shown in FIG. 1, whereupon the sleeve  30  is shifted downwardly using the hydraulic cylinders  38  so that the dogs  28  are locked into extension through the windows  32  and into the groove  20  of the end connector  16 . The telescoping riser is now at its shortest length for transport or for support of the BOP stack or just the riser assembly when disconnected from the wellhead such as when storms are approaching. If operation is desired where the telescoping riser system will lock upon full retraction of the inner barrel  12  into the outer barrel  14 , then the actuating sleeve  30  is placed in the middle position and FIGS. 1-4 illustrate that upon sufficient retraction of the inner barrel  12  into the outer barrel  14 , the dogs  28  will jump out of the way so that groove  20  of end connector  16  can present itself opposite the windows  32 . At this time, the springs  42  pull the dogs  28  downwardly to allow the conforming shapes of the dogs  28  and the groove  20  to fully engage, whereupon the load connected to the end connector  16  is fully supported off of loading surface  40  of dogs  28 . This position is shown in FIG.  4 . 
     The third position is seen in FIG. 6 where the actuating sleeve  30  is moved to its uppermost position, precluding any entrance of dogs  28  through the windows  32 . This allows full telescoping action as between the inner barrel  10  and the outer barrel  14  without a locking relationship possible on full retraction of the inner barrel  12  into the outer barrel  14 . 
     Another feature of the locking connection L is shown in FIG.  7 . An indicating rod  52  connected to sleeve  30  extends through housing  10  and serves as a guide for sleeve  30  when sleeve  30  is moved up or down by hydraulic cylinders  38 . The amount of extension of rod  52  out of housing  10  also gives a visual signal to operating personnel regarding the position of the sleeve  30 . Those skilled in the art will appreciate that the position of the rod  52  can also be connected to a sensor which will display its position on a control panel  39  for the hydraulics which control the operation of hydraulic cylinders  38 . Thus, apart from giving a visual or other type of signal as to the position of sleeve  30 , the extension of rods  52  and, in the preferred embodiment there are two of them at 180°, provides a guide for the movement of sleeve  30 . Also shown in FIG. 7 are fasteners  54  which are used to secure the inner barrel  12  to the locking connector L by preventing the inner barrel from becoming unthreaded. 
     Those skilled in the art will appreciate that the prior designs which involved manual operation in the moonpool have been dramatically improved with this design for a locking connector L for a riser system in an offshore drilling or production environment. Personnel can now select from at least three desirable modes of operation. In times of storm, for example, or during transport, the locking connector L can be placed in the position of FIG. 5 where the telescoping connection is locked into its shortest position where it can support substantial loads such as the BOP stack or just the riser assembly which may have been disconnected from the wellhead during times of storms at the surface. By using the position of FIG. 6, the locking connection L can be easily placed in a configuration where the inner and outer barrels  12  and  14  can telescope fully in both directions without locking to each other. Finally, by placing the sleeve  30  in the position shown in FIG. 1, the locking connector L will only lock the inner barrel  12  to the outer barrel  14  upon maximum retraction of the inner barrel  12  into the outer barrel  14 . 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.