Patent Publication Number: US-11035194-B2

Title: Pressure control device, and installation and retrieval of components thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of prior application Ser. No. 15/252,499 filed on 31 Aug. 2016. The entire disclosure of this prior application is incorporated herein by this reference. 
    
    
     BACKGROUND 
     This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides a pressure control device, and tools for installation and retrieval of the pressure control device. 
     A pressure control device is typically used to seal off an annular space between an outer tubular structure (such as, a riser, a housing on a subsea structure in a riser-less system, or a housing attached to a surface wellhead) and an inner tubular (such as, a drill string, a test string, etc.). At times it may be desired for components (such as, bearings, seals, etc.) of the pressure control device to be retrieved from, or installed in, an outer housing (such as, a riser housing). 
     Therefore, it will be appreciated that advancements are continually needed in the arts of constructing and operating pressure control devices. In particular, it would be desirable to provide for convenient and efficient installation and retrieval of pressure control device components respectively into and out of an outer housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative partially cross-sectional view of an example of a well system and associated method which can embody principles of this disclosure. 
         FIG. 2  is a representative cross-sectional view of an example of a replaceable assembly being installed in a pressure control device outer housing. 
         FIG. 3  is a representative cross-sectional view of the replaceable assembly in a run-in configuration suspended on a running tool. 
         FIG. 4  is a representative elevational view of the replaceable assembly. 
         FIG. 5  is a representative cross-sectional view of the replaceable assembly. 
         FIG. 6  is a representative cross-sectional view of a section of the replaceable assembly. 
         FIGS. 7A  &amp; B are representative cross-sectional views of the replaceable assembly as landed and set, respectively, in the outer housing. 
         FIGS. 8A  &amp; B are representative cross-sectional views of a section of the replaceable assembly in respective landed and set configurations. 
         FIG. 9  is a representative cross-sectional view of a lower latch section of the pressure control device. 
         FIG. 10  is a representative partial cross-sectional view of the replaceable assembly and running tool in the landed configuration. 
         FIGS. 11A-C  are representative elevational, longitudinal cross-sectional and lateral cross-sectional views, respectively, of a collet and iris mechanism section of the pressure control device. 
         FIGS. 12A-C  are representative cross-sectional views of the iris mechanism in respective retracted, partially extended and fully extended configurations. 
         FIG. 13  is a representative exploded perspective view of the collet and iris mechanisms section of the pressure control device. 
         FIG. 14  is a representative exploded perspective view of the iris mechanism. 
         FIG. 15  is a representative exploded perspective view of components of the iris mechanism. 
         FIG. 16  is a representative perspective view of a segment of the iris mechanism. 
         FIG. 17  is a representative exploded perspective view of the collet mechanism. 
         FIG. 18  is a representative cross-sectional view of the replaceable assembly set in the outer housing. 
         FIG. 19  is a representative cross-sectional view of a latch section releasably securing the replaceable assembly in the outer housing. 
         FIGS. 20A-C  are representative cross-sectional and perspective views of components of the latch section. 
         FIG. 21  is a representative cross-sectional view of the pressure control device during drilling operations. 
         FIG. 22  is a representative cross-sectional view of the pressure control device during a retrieval operation. 
         FIG. 23  is a representative cross-sectional view of a section of the pressure control device as a latch is being disengaged. 
         FIG. 24  is a representative cross-sectional view of the latch in a disengaged configuration. 
         FIG. 25  is a representative cross-sectional view of the replaceable assembly and running tool as retrieved from the outer housing. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIG. 1  is a well system  10  and associated method which can embody principles of this disclosure. However, it should be clearly understood that the system  10  and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system  10  and method described herein and/or depicted in the drawings. 
     In the system  10  as depicted in  FIG. 1 , a generally tubular riser string  12  extends between a water-based rig  14  and a lower marine riser package  16  above a subsea wellhead installation  18  (including, for example, various blowout preventers, hangers, fluid connections, etc.). However, in other examples, the principles of this disclosure could be practiced with a land-based rig, or with a riser-less installation. 
     In the  FIG. 1  example, a tubular string  20  (such as, a jointed or continuous drill string, a coiled tubing string, etc.) extends through the riser string  12  and is used to drill a wellbore  22  into the earth. For this purpose, a drill bit  24  is connected at a lower end of the tubular string  20 . 
     The drill bit  24  may be rotated by rotating the tubular string  20  (for example, using a top drive or rotary table of the rig  14 ), and/or a drilling motor may be connected in the tubular string  20  above the drill bit  24 . 
     Furthermore, the principles of this disclosure could be utilized in well operations other than drilling operations. Thus, it should be appreciated that the scope of this disclosure is not limited to any of the details of the tubular string  20  or wellbore  22  as depicted in the drawings or as described herein. 
     The riser string  12  depicted in  FIG. 1  includes a riser housing  26  connected in the riser string  12  below a tensioner ring  28  suspended from the rig  14 . In other examples, the riser housing  26  could be connected above the tensioner ring  28 , or could be otherwise positioned (such as, in the wellhead installation  18  in a riser-less configuration). Thus, the scope of this disclosure is not limited to any particular details of the riser string  12  or riser housing  26  as described herein or depicted in the drawings. 
     The riser housing  26  includes a side port  30  that provides for fluid communication between a conduit  32  and an annulus  34  formed radially between the riser string  12  and the tubular string  20 . In a typical drilling operation, drilling fluid can be circulated from the rig  14  downward through the tubular string  20 , outward from the drill bit  24 , upward through the annulus  34 , and return to the rig  14  via the conduit  32 . 
     As depicted in  FIG. 1 , a releasable assembly  40  is installed in the riser housing  26 . The releasable assembly  40  in this example is of the type known to those skilled in the art as a rotating control device. 
     However, the scope of this disclosure is not limited to installation or retrieval of any particular type of releasable assembly in the riser housing  26 . In other examples, the releasable assembly  40  could comprise a protective sleeve (e.g., having no annular seal for engagement with the tubular string  20 ), or a non-rotating pressure control device (e.g., having one or more non-rotating annular seals for engagement with the tubular string  20 ). 
     In the  FIG. 1  example, the releasable assembly  40  includes one or more annular seals  42  that seal off the annulus  34  above the side port  30 . In this example, the annular seals  42  are configured to sealingly engage an exterior of the tubular string  20 . The annular seals  42  may be of a type known to those skilled in the art as “passive,” “active” or a combination of passive and active. The scope of this disclosure is not limited to use of any particular type of annular seal. 
     Rotation of the annular seals  42  relative to the riser housing  26  is provided for by a bearing assembly  44  of the releasable assembly  40 . The annular seals  42  and bearing assembly  44  are releasably secured in the riser housing  26  by a latch  46  of the releasable assembly  40 . The latch  46  permits the annular seals  42  and/or the bearing assembly  44  to be installed in, or retrieved from, the riser housing  26  when desired, for example, to service or replace the seals  42  and/or bearing assembly  44 . 
     The tubular string  20  can include running and retrieval tools, examples of which are described more fully below and depicted in  FIGS. 2, 3, 6-10, 18, 19 and 22-25 , for installing and retrieving the releasable assembly  40 . However, it should be clearly understood that the scope of this disclosure is not limited to these particular examples of running and retrieval tools, and is not limited to use of a running or retrieval tool as part of the tubular string  20  of  FIG. 1 . 
     Referring additionally now to  FIG. 2 , an example of a pressure control device  50  that may be used in the system  10  and method of  FIG. 1  is representatively illustrated. In other examples, the pressure control device  50  could be used with other systems and methods. 
       FIG. 2  depicts a representative cross-sectional view of an example of the replaceable assembly  40  being installed in an outer housing  52  of the pressure control device  50 . When used in the system  10  of  FIG. 1 , the outer housing  52  could comprise the riser housing  26 . In other examples, the outer housing  52  may not be connected in a riser string, or may be in another arrangement with respect to other well equipment. 
     In the  FIG. 2  example, the outer housing  52  comprises multiple sections, a lower one of which has the side port  30  formed therein, and an upper one of which encloses the latch  46  for releasably securing the releasable assembly  40 . In other examples, the outer housing  52  could comprise other sections or other numbers of sections (including one), and the outer housing  52  could be positioned within one or more other housings. Thus, the scope of this disclosure is not limited to any particular details of the outer housing  52  as described herein or depicted in the drawings. 
     The replaceable assembly  40  as depicted in  FIG. 2  includes two of the annular seals  42  for sealing engagement with an exterior of the tubular string  20  when it is positioned in a passage  54  formed longitudinally through the pressure control device  50 . The annular seals  42  are rotatably supported relative to the outer housing  52  by the bearing assembly  44 . 
     A running tool  56  is connected in the tubular string  20  for conveying the releasable assembly  40  through the riser string  12 , and into and out of the outer housing  52 . The running tool  56  is used in this example both for installing the releasable assembly  40  in the outer housing  52 , and for retrieving the releasable assembly  40  from the outer housing  52  and riser string  12 . 
     As described more fully below, the releasable assembly  40  can be releasably secured in the outer housing  52  by conveying the releasable assembly  40  on the running tool  56  connected in the tubular string  20 , engaging the latch  46  to limit further downward displacement of the releasable assembly  40  relative to the outer housing  52 , and applying a downwardly directed force to the releasable assembly  40  via the running tool  56  (e.g., by slacking off weight of the tubular string  20  at the rig  14 ). 
     When a predetermined downwardly directed force is achieved, the latch  46  is “set,” so that the releasable assembly  40  is releasably secured against longitudinal and rotational displacement relative to the outer housing  52 . In addition, the running tool  56  is released from the releasable assembly  40 , so that the running tool  56  and the remainder of the tubular string  20  can be retrieved from the riser string  12 . 
     When it is desired to retrieve the releasable assembly  40  from the riser string  12  (for example to perform maintenance on or replace the annular seals  42 , bearing assembly  44 , or the entire releasable assembly  40 ), the running tool  40  can again be connected in the tubular string  20  and conveyed into the releasable assembly  40 . The releasable assembly  40  is then retrieved by applying a predetermined downwardly directed force to the releasable assembly  40  via the running tool  56  (e.g., by slacking off weight of the tubular string  20  at the rig  14 ), and then applying pressure to the latch  46  (e.g., hydraulic pressure applied via ports  58 ,  60  formed through the outer housing  52 ). The predetermined downwardly directed force applied in this retrieval operation may be the same as, or different from, the predetermined downwardly directed force applied in the above-described installation operation. 
     When a sufficient pressure is applied to the latch  46 , the latch  46  disengages and the releasable assembly  40  can be displaced upward relative to the outer housing  52 , thereby relieving the previously applied downwardly directed force. This relieving of the downwardly directed force causes an inner dimension of the releasable assembly  40  to decrease, so that an outer dimension of the running tool  56  is prevented from displacing upward through the inner dimension, thereby enabling the releasable assembly  40  to be conveyed upward through the riser string  12  on the running tool  56 . 
     Although the running tool  56  is described herein as being used to both install and retrieve the releasable assembly  40 , in other examples different running tools may be used for respectively installing and retrieving the releasable assembly  40 , the releasable assembly  40  may not be both installed and retrieved (e.g., the releasable assembly  40  could be only installed or only retrieved), or the releasable assembly  40  may not be retrieved after it is installed. Thus, the scope of this disclosure is not limited to any particular steps performed in any particular order or combination, or to any particular purpose or configuration of the running tool  56 . 
     Referring additionally now to  FIG. 3 , a cross-sectional view of the replaceable assembly  40  in a run-in configuration suspended on the running tool  56  is representatively illustrated. In this configuration, the releasable assembly  40  may be either installed in or retrieved from the outer housing  52  of  FIG. 2 . 
     As depicted in  FIG. 3 , the releasable assembly  40  includes an iris mechanism  62  for varying the inner dimension of the releasable assembly  40 . In the  FIG. 3  configuration, an external shoulder  64  formed on the running tool  56 , and having an outer dimension larger than a reduced inner dimension of the releasable assembly  40 , engages the iris mechanism  62  and thereby prevents the running tool  56  from displacing upward relative to the releasable assembly  40 . 
     Thus, the replaceable assembly  40  can be conveyed into or out of the outer housing  52  on the running tool  56 . In addition, the running tool  56  has another external shoulder  66  formed thereon. The external shoulder  66  can engage an internal shoulder  68  formed in the releasable assembly  40 , to enable the downwardly directed force to be applied from the running tool  56  to the releasable assembly  40  during the installation and retrieval operations. 
     Referring additionally now to  FIGS. 4 &amp; 5 , representative elevational and cross-sectional views of the replaceable assembly  40  are representatively illustrated. In these views, it may be seen that the annular seals  42  are connected to a generally tubular inner mandrel  70 , which is rotatably supported in an outer housing  72  by the bearing assembly  44 . 
     The outer housing  72  may include any number of sections (including one) and may be otherwise configured. Thus, the scope of this disclosure is not limited to any particular details of the outer housing  72  or any other components of the releasable assembly  40  as described herein or depicted in the drawings. 
     The annular seals  42  are conveniently accessible for installation or replacement by means of circumferentially distributed “J” locks  74 . Each of the J locks  74  includes lugs  76  and “J” or “L”-shaped slots  78  for providing access to the annular seals  42  in the releasable assembly  40 . Fasteners  80  (such as, screws or bolts) can be used to retain the J locks  74  in locked configurations. 
     In  FIGS. 4 &amp; 5 , it may also be seen that the releasable assembly  40  includes a collet mechanism  82  comprising multiple circumferentially distributed flexible collets  84 . Each of the collets  84  has an external profile  86  formed thereon for cooperative engagement in the latch  46  (see  FIG. 2 ). 
     As described more fully below, the collet mechanism  82  is configured to initiate setting of the latch  46 , and to actuate the iris mechanism  62 . The collets  84  are biased downward relative to the outer housing  72 , so that the iris mechanism  62  is in an expanded configuration (e.g., in which its inner dimension ID is increased or at a maximum) only when the outer housing  72  and most of the remainder of the releasable assembly  40  is displaced downward relative to the collets  84 . Such downward displacement relative to the collets  84  occurs during the installation operation, when the predetermined downwardly directed force is applied to the releasable assembly  40  to set the latch  46 . 
     Referring additionally now to  FIG. 6 , a cross-sectional view of a section of the replaceable assembly  40  is representatively illustrated, with the running tool  56  therein. In this view, further details of the bearing assembly  44 , iris mechanism  62  and collet mechanism  82  may be seen. 
     A radially enlarged annular structure  88  formed on the inner mandrel  70  is axially or longitudinally supported between two thrust bearings  90  of the bearing assembly  44 . The inner mandrel  70  is also radially supported by radial bearings  92 . Thus, the inner mandrel  70  (and the connected annular seals  42 ) can rotate freely within the outer housing  72 , but the inner mandrel  70  is prevented from displacing substantially axially relative to the outer housing  72  (although very limited axial displacement may be possible, e.g., with springs (such as Bellville springs)  94  positioned between the annular structure  88  and each of the bearings  90  to compensate for manufacturing tolerances and nominal clearances). 
     Rotary seals  96  seal off opposite ends of a lubricant-filled lubricant flow path  98  exposed to the bearings  90 ,  92 . In this example, the rotary seals  96  may be of the type known to those skilled in the art as “controlled leakage” rotary seals that provide for a limited amount of leakage, so that the sealing contact between the seals and the seal surfaces they engage is continuously flushed of debris and lubricated, although other types of rotary seals may be used in other examples. 
     The lubricant flow path  98  is in communication with a pressurized lubricant chamber  100 , so that the lubricant flow path  98  is continuously supplied with lubricant from the lubricant chamber  100 . The lubricant chamber  100  is pressurized by means of an annular piston  102  that is biased toward the chamber  100  by a biasing force exerted by a spring  104 . 
     Opposite the chamber  100 , the piston  102  is exposed to pressure in the passage  54  below the lower annular seal  42 . In this manner, during drilling or other operations, when the annular seal  42  is sealingly engaged with the tubular string  20  (see  FIG. 1 ), the lubricant chamber  100  will be pressurized to a level equal to the pressure in the passage  54  below the lower annular seal  42  (which in the  FIG. 1  system  10  is also the pressure in the annulus  34 ) exposed to the piston  102 , plus a pressure due to the biasing force exerted on the piston  102  by the spring  104 . Thus, there is always a positive pressure differential from the lubricant flow path  98  and chamber  100  to the passage  54 . 
     As the inner mandrel  70  rotates (due, for example, to rotation of the tubular string  20  in the passage  54  while engaged by the annular seals  42 ), a flow inductive profile  108  formed on the annular structure  88  induces the lubricant to flow through the flow path  98 . In this manner, the lubricant is continuously circulated about the bearings  90 ,  92  as the inner mandrel  70  rotates. 
     The flow inductive profile  108  could in some examples be provided as a relatively coarse helical thread on the annular structure  88 . In other examples, the profile  108  could comprise multiple vanes or a flow inducing rotor. Any type of flow inductive profile may be used in keeping with the scope of this disclosure. 
     Note that, in the  FIG. 6  example, the inner dimension ID of the iris mechanism  62  is less than the outer dimension OD of the running tool  56 . The shoulder  64  will, thus, engage iris segments  106  of the iris mechanism  62  and thereby prevent downward displacement of the releasable assembly  40  relative to the running tool  56 . 
     As described more fully below, the iris segments  106  displace radially inward and radially outward to thereby decrease and increase, respectively, the inner dimension ID. As viewed in  FIG. 6 , the iris segments  106  are in a retracted configuration, in which the inner dimension ID is at a minimum, and less than the outer dimension OD. In an expanded configuration, the inner dimension ID can be at a maximum, and greater than the outer dimension OD, so that the running tool  56  can displace upwardly through the passage  54  and out of the replaceable assembly  40 . 
     Referring additionally now to  FIGS. 7A  &amp; B, cross-sectional views of the replaceable assembly  40  as landed and set, respectively, in the outer housing  52  are representatively illustrated. These landed and set configurations occur during installation of the replaceable assembly  40  in the outer housing  52 . 
     In  FIG. 7A , the replaceable assembly  40  has been conveyed into the outer housing  52  on the running tool  56  (with the iris mechanism  62  in its retracted configuration as depicted in  FIG. 6 ). The collet mechanism  82  has engaged the latch  46 . As described more fully below, the profiles  86  (see  FIG. 6 ) of the collet mechanism  82  engage a complementarily shaped internal profile in the latch  46 , and this engagement substantially limits further downward displacement of the replaceable assembly  40  relative to the outer housing  52 . 
     In  FIG. 7B , a predetermined downwardly directed force has been applied to the replaceable assembly  40 , so that the latch  46  is set, thereby releasably securing the replaceable assembly  40  against longitudinal and rotational displacement relative to the outer housing  52 . In addition, the iris mechanism  62  is actuated to its expanded configuration, thereby allowing the running tool  56  to be retrieved from the releasable assembly  40  and riser string  12 . 
     Referring additionally now to  FIGS. 8A  &amp; B, cross-sectional views of a section of the replaceable assembly  40  in the respective landed and set configurations are representatively illustrated. In these views, the manner in which the replaceable assembly  40  engages the latch  46  and the latch is set in response to the downwardly directed force may be more clearly seen. 
     In  FIG. 8A , it may be seen that, when the replaceable assembly  40  is conveyed downwardly into the outer housing  52 , the external profiles  86  on the collets  84  cooperatively engage an internal profile  110  in the latch  46 . This engagement between the profiles  86 ,  110  enables further downward displacement of the releasable assembly  40  to be used to set the latch  46  and actuate the iris mechanism  62  to its expanded configuration. 
     In  FIG. 8B , it may be seen that the replaceable assembly  40  has been displaced downward somewhat (relative to the  FIG. 8A  landed configuration) relative to the outer housing  52 , due to the predetermined downwardly directed force being applied to the replaceable assembly  40 . The latch  46  is now set, releasably securing the releasable assembly  40  in the outer housing  52 . The iris mechanism  62  is also actuated to its expanded configuration, so that the running tool  56  may now be retrieved from the releasable assembly  40  and the riser string  12 . 
     Note that, when the latch  46  is set, helical flutes  112  formed externally on the running tool  56  are positioned within each of the annular seals  42 . The helical flutes  112  prevent the annular seals  42  from fully sealingly engaging the exterior of the running tool  56 , thereby preventing a pressure differential from building up across the annular seals  42  during the installation and retrieval operations. 
     Referring additionally now to  FIG. 9 , a representative cross-sectional view of a lower latch section of the pressure control device  50  is representatively illustrated in the landed configuration. In this view, the engagement between the profiles  86 ,  110  can be more clearly seen. 
     Note that the profiles  86 ,  110  are configured such that the profile  86  will engage the profile  110  as the collet mechanism  82  displaces downward through the latch  46 . After the profiles  86 ,  110  are engaged in this manner, further downward displacement of the collet mechanism  82  and the remainder of the releasable assembly  40  will cause a setting sleeve  114  (in which the profile  110  is formed) to displace downward also, in order to set the latch  46 . 
     The collets  84  are biased downward by a spring  116 , and the setting sleeve  114  is biased upward by a spring  118 . After the profiles  86 ,  110  are engaged with each other and the downwardly directed force is applied to the releasable assembly  40 , the spring  116  is compressed (due to downward displacement of the releasable assembly  40  relative to the collets  84 ), and the spring  118  is compressed (due to downward displacement of the setting sleeve  114  with the collets  84 ). 
     The downward displacement of the releasable assembly  40  relative to the collets  84  actuates the iris mechanism  62  to its expanded configuration in which the iris segments  106  are displaced radially outward. In addition, upper ends of the collets  84  are now positioned between the internal profile  110  and a radially enlarged portion  72   a  of the outer housing  72 , so that the external profiles  86  are prevented from disengaging from the internal profiles  110 . 
     Referring additionally now to  FIG. 10 , a representative partial cross-sectional view of the replaceable assembly  40  and running tool  56  in the landed configuration is representatively illustrated. In this view, the manner in which the flutes  112  on the running tool  56  prevent a pressure differential from being formed across each of the annular seals  42  can be more clearly seen. 
     Referring additionally now to  FIGS. 11A-C , representative elevational, longitudinal cross-sectional and lateral cross-sectional views, respectively, of the iris and collet mechanisms  62 ,  82  of the releasable assembly  40  are representatively illustrated. In these views, the manner in which the iris and collet mechanisms  62 ,  82  operate together can be more clearly seen. 
     As mentioned above, the collets  84  are biased downward relative to the housing  72  by the spring  116 . The collets  84  are prevented from rotating relative to the housing  72  by keys  120  slidingly received in longitudinally elongated slots  122 . Keepers  124  secure the keys  120  to the collets  84 . Thus, the collets  84  can displace longitudinally somewhat relative to the housing  72 , but cannot rotate relative to the housing  72 . 
     A drive plate  126  and a guide sleeve  128  of the iris mechanism  62  are also prevented from rotating relative to the housing  72 , and are retained in the housing  72  by a retainer sleeve  130 . A drive sleeve  132  positioned between the guide sleeve  128  and a drive hub  134  has keys  136  formed thereon which slidingly engage longitudinally extending slots  138  in the guide sleeve  128 . Thus, the drive sleeve  132  can displace longitudinally somewhat relative to the housing  72  and guide sleeve  128 , but is prevented from rotating relative to the housing  72  and guide sleeve  128 . 
     The drive sleeve  132  is biased downwardly by a biasing force exerted by a spring  140 . Each of the keys  120  is secured to the drive sleeve  132  by a fastener  142  that extends through the key  120  and into a corresponding one of the keys  136 . Thus, the collets  84  and drive sleeve  132  displace longitudinally together, and are biased downward by the springs  116 ,  140 . 
     Fasteners  144  are secured to the drive sleeve  132  and extend radially inward into sliding engagement with helical slots  146  formed in the drive hub  134 . As the drive sleeve  132  displaces longitudinally, the engagement between the fasteners  144  and the helical slots  146  causes the drive hub  134  to rotate. As described more fully below, rotation of the drive hub  134  causes the iris segments  106  to radially extend or retract, depending on the direction of the rotation. 
     Note that each of the iris segments  106  has upper and lower pins  106   a,b  projecting longitudinally therefrom. The upper pins  106   a  are slidingly received in slots  148  formed in the housing  72 . The lower pins  106   b  are slidingly received in slots  150  formed in the drive plate  126 . The lower pins  106   b  are also received in slots  152  formed in the drive hub  134 . 
     Because the lower pins  106   b  are received in the slots  152  of the drive hub  134 , the iris segments  106  will rotate with the drive hub  134 . Thus, the iris segments  106  rotate in response to relative longitudinal displacement between the housing  72  and the collets  84 , and the resulting rotation of the drive hub  134 . 
     The slots  148 ,  150  in the housing  72  and drive plate  126  are configured so that, in response to relative rotation between the iris segments  106  and the housing  72 , the iris segments  106  are displaced radially inward or outward, depending on the direction of the rotation. The manner in which the iris segments  106  are radially displaced due to their engagement with the slots  148 ,  150  can be more clearly seen in  FIGS. 12A-C . 
       FIGS. 12A-C  are representative cross-sectional views of the iris mechanism  62  in respective retracted, partially extended and fully extended configurations, taken along line  12 - 12  of  FIG. 11B . The slots  150  in the drive plate  126  are visible in  FIGS. 12A-C . The slots  148  in the housing  72  are similarly configured. 
     Note that the slots  150  are inclined radially and circumferentially so that, as the iris segments  106  rotate relative to the housing  72  and drive plate  126 , the iris segments  106  are displaced radially inward or outward, depending on the direction of rotation. Thus, the iris segments  106  displace both rotationally and radially relative to the housing  72  and drive plate  126  in changing between the retracted, partially extended and fully extended configurations of the iris mechanism  62 . 
     In  FIG. 12A , the iris mechanism  62  is in its retracted configuration. This retracted configuration is used when the replaceable assembly  40  is being conveyed on the running tool  56  during the installation and retrieval operations. The collets  84  are in their fully downward longitudinal position relative to the housing  72  in this retracted configuration. 
     In  FIG. 12B , the iris mechanism  62  is in a partially extended configuration. This configuration occurs when the collets  84  have engaged the latch  46  (see  FIG. 9 ) and the replaceable assembly  40  is then displaced further downward, so that the collets  84  are displaced longitudinally upward relative to the housing  72  against the biasing forces exerted by the springs  116 ,  140  (see  FIG. 11B ). 
     In  FIG. 12A , the iris mechanism  62  is in its fully extended configuration, in which the iris segments  106  are radially outwardly extended (the iris segments  106  are only visible in  FIG. 12C  through the slots  150 ). In this extended configuration, the iris segments  106  do not inhibit displacement of the running tool  56  (or any of the remainder of the tubular string  20 ) longitudinally through the passage  54 . The iris mechanism  62  is in this extended configuration when the latch  46  is set, as described more fully below. 
       FIG. 13  is a representative exploded perspective view of the iris and collet mechanisms  62 ,  82 . In this view, the manner in which the various components of these mechanisms  62 ,  82  are arranged together can be more clearly seen. 
       FIG. 14  is a representative exploded perspective view of the iris mechanism  62 . In this view, the arrangement of the slots  148  in the housing  72  can be seen. 
       FIG. 15  is a representative exploded perspective view of certain components of the iris mechanism  62 . It will be appreciated from this view that the lower pins  106   b  on the iris segments  106  are free to displace radially in the slots  152  of the drive hub  134 . As the drive hub  134  rotates, the iris segments  106  rotate with the drive hub  134 , and the configurations of the slots  150  (and slots  148  in the housing  72  (see  FIG. 14 )) cause the iris segments  106  to displace radially inward or outward, depending on the direction of the rotation. 
     Referring additionally now to  FIG. 16 , a perspective view of an individual iris segment  106  of the iris mechanism  62  is representatively illustrated. The iris segment  106  has a body  106   c  from which the pins  106   a,b  extend longitudinally in opposite directions. 
     A “T”-shaped slider  106   d  is formed on one side of the body  106   c , and a complementarily-shaped slot  106   e  is formed on another side of the body  106   c . The slider  106   d  of each iris segment  106  slidingly engages the slot  106   e  of a next adjacent iris segment  106 , so that all of the iris segments cooperate in displacing between the retracted and extended configurations. 
     In other examples, the slider  106   d  and slot  106   e  may be dovetail, trapezoidal or otherwise-shaped. The scope of this disclosure is not limited to any particular shapes of the iris segment  106  or any of its components. 
     Note that the slider  106   d  and the slot  106   e  are not arranged in parallel. Instead, the slider  106   d  and slot  106   e  are angularly offset, in order to accommodate rotation of the iris segments  106  about the pins  106   a,b  as the iris segments displace radially inward and outward. 
     The pins  106   a,b  define an axis  154  about which each iris segment  106  rotates as it displaces radially. Note that the axes  154  of the iris segments  106  are parallel to an axis  156  (see  FIG. 18 ) of the passage  54  that extends longitudinally through the releasable assembly  40 . 
     Referring additionally now to  FIG. 17 , a representative exploded perspective view of the collet mechanism  82  and associated components of the iris mechanism  62  is representatively illustrated. The keys  136  on the drive sleeve  132  are slidingly received in the longitudinal slots  138  of the guide sleeve  128 , and the drive sleeve  132  is downwardly biased by the spring  140 . The keys  120  and fasteners  142 ,  144  ensure that the collets  84  displace longitudinally with the drive sleeve  132 . 
     Referring additionally now to  FIG. 18 , a cross-sectional view of the replaceable assembly  40  set in the outer housing  52  is representatively illustrated. In this set configuration, the latch  46  prevents relative longitudinal and rotational displacement between the replaceable assembly  40  and the outer housing  52 . 
     The set configuration occurs in response to the predetermined downwardly directed force being applied to the replaceable assembly  40  after the collet assembly  82  has engaged the latch  46 . Thus, the application of the predetermined downwardly directed force to the replaceable assembly  40  both sets the latch  46  and actuates the iris mechanism  62  to its fully expanded configuration. 
     Referring additionally now to  FIG. 19 , a representative cross-sectional view of the latch  46  releasably securing the replaceable assembly  40  in the outer housing  52  is representatively illustrated. The latch  46  is set as depicted in  FIG. 19 , and so relative longitudinal and rotational displacement between the outer housing  52  and the replaceable assembly  40  is prevented (although the annular seals  42  and inner mandrel  70  can still rotate in the releasable assembly  40 ). Note that the replaceable assembly  40  is also sealingly received in the latch  46 , due to an annular seal  158  carried on the housing  72  being sealingly engaged in the setting sleeve  114 . 
     The latch  46  includes circumferentially distributed and radially displaceable grip members or slips  160  received in the setting sleeve  114 . The slips  160  displace longitudinally with the setting sleeve  114 . 
     The slips  160  are biased radially outward by springs  162 . However, when the setting sleeve  114  and slips  160  displace downward as viewed in  FIG. 19 , the slips  160  are also displaced radially inward due to cooperation between inclined surfaces formed on the slips  160  and in a slip housing  164  of the latch  46 . 
     As depicted in  FIG. 19 , the setting sleeve  114  has been displaced downward along with the releasable assembly  40  after the collet profiles  86  have engaged the internal profile  110  in the setting sleeve  114 . The slips  160  have displaced downward with the setting sleeve  114 , and have displaced radially inward as a result of the inclined surfaces on the slips  160  and in the slip housing  164 . 
     A radially reduced gripping surface  160   a  in each of the slips  160  now grippingly engages a radially recessed external surface  72   b  on the housing  72 . The gripping surfaces  160   a  may be provided with inner serrations, teeth, roughness, embedded particles or other structures suitable for grippingly engaging the external surface  72   b.    
     The engagement of the slips  160  with the external surface  72   b  prevents relative rotation and longitudinal displacement between the housing  72  of the replaceable assembly  40 , and the latch  46  and outer housing  52  of the pressure control device  50 . Note that prevention of relative longitudinal displacement is provided by the reception of the slips  160  in the radially recessed portion of the housing  72 , whether or not the surfaces  160   a  grippingly engage the external surface  72   b.    
     An upper end of the setting sleeve  114  is externally tapered. When the setting sleeve  114  displaces downward, a radially extendable and retractable setting ring  166  is permitted to radially retract. The setting ring  166  has internal and external tapered surfaces. 
     A piston  168  sealingly and reciprocably positioned in the outer housing  52  has a tapered internal surface that engages the tapered external surface of the setting ring  166 . The piston  168  is biased upward by one or more springs  170 . 
     As the setting sleeve  114  displaces downward, the setting ring  166  radially retracts and the piston  168  displaces upward somewhat, due to the biasing force exerted by the springs  170  and the inclined surfaces engaged between the setting ring  166  and the piston  168 . Because the setting ring  166  has been radially retracted and the piston  168  now radially outwardly supports the setting ring  166  in its radially retracted configuration, the setting sleeve  114  cannot now displace upward to unset the latch  46 . Thus, the setting ring  166 , the springs  170 , and the tapered surfaces on and in the setting sleeve  114  and piston  168  function as a locking mechanism to prevent unsetting of the latch  46  after it has been set. 
     Referring additionally now to  FIGS. 20A-C , cross-sectional and perspective views of components of the latch  46  are representatively illustrated. Specifically, the slip housing  164  is depicted in  FIG. 20A , the setting sleeve  114  is depicted in  FIG. 20B  and one of the slips  160  is depicted in  FIG. 20C . 
     In  FIG. 20A  it may be seen that the slip housing  164  includes multiple circumferentially spaced apart sets of internal inclined surfaces  164   a . The sets of inclined surfaces  164   a  are rotationally aligned with longitudinally elongated slots  164   b  formed in the slip housing  164 . 
     In  FIG. 20B  it may be seen that the setting sleeve  114  includes multiple circumferentially spaced apart grooved openings  114   a  for receiving the slips  160  therein. The setting sleeve  114  also includes an upper tapered external surface  114   b  for cooperative engagement with the setting ring  166 . 
     Fasteners  172  (see  FIG. 19 ) are threaded into circumferentially spaced apart holes  114   c  in the setting sleeve  114  and are slidingly received in the slots  164   b  in the slip housing  164  to prevent relative rotation between the setting sleeve  114  and the slip housing  164 . This maintains rotational alignment between the internal inclined surfaces  164   a  and the slips  160  disposed in the openings  114   a.    
     In  FIG. 20C  it may be seen that the slips  160  have external inclined surfaces  160   b  formed thereon for cooperative engagement with the inclined surfaces  164   a  of the slip housing  164 . When the setting sleeve  114  and slips  160  are displaced downward relative to the slip housing  164  to set the latch  46 , the cooperative engagement between the inclined surfaces  160   b ,  164   a  will cause the slips  160  to displace radially inward. Conversely, when the setting sleeve  114  and slips  160  are displaced upward relative to the slip housing  164  to unset the latch  46 , separation between the inclined surfaces  160   b ,  164   a  will allow the slips  160  to be displaced radially outward by the springs  162  (see  FIG. 19 ). 
     Referring additionally now to  FIG. 21 , a representative cross-sectional view of the pressure control device  50  during drilling operations is representatively illustrated. The pressure control device  50  is in the set configuration of  FIG. 18 , and the tubular string  20  is received in the passage  54  and sealingly engaged by the annular seals  42 . 
     When the tubular string  20  is rotated (for example, to rotate the drill bit  24  of  FIG. 1 ), friction between the annular seals  42  and the tubular string  20  will cause the annular seals to rotate with the tubular string. Such rotation is provided for by the bearing assembly  44 . 
     The iris mechanism  62  is in its fully expanded configuration. The iris segments  106  do not inhibit displacement of the tubular string  20  through the passage  54 , and even allow radially enlarged tool joints  20   a  to pass through the iris mechanism  62 . 
     The latch  46  remains set throughout the drilling operation or other operations. The cooperative engagement between the tapered setting ring  166  and each of the setting sleeve  114  and piston  168 , assisted by the springs  170 , ensures that the latch  46  will not inadvertently become unset during drilling or other operations. 
     When it is desired to unset the latch  46  and thereby allow retrieval of the releasable assembly  40  from the outer housing  52 , the running tool  56  (or another running tool) can again be connected in the tubular string  20  (or another tubular string) and run into the replaceable assembly  40 .  FIG. 22  representatively illustrates a cross-sectional view of the pressure control device  52  during such a retrieval operation. 
     The flutes  112  on the running tool  56  are in the annular seals  42 , so that no pressure differential is allowed to build up across the annular seals  42 . The external shoulder  66  on the running tool  56  is engaged with the internal shoulder  68  in the releasable assembly  40 , as depicted in  FIG. 22 . 
     A downwardly directed force can now be applied from the running tool  56  to the replaceable assembly  40  (e.g., by slacking off on the tubular string  20  at the rig  14  (see  FIG. 1 )). This downwardly directed force ensures that the running tool  56  is properly positioned relative to the releasable assembly  40 , prior to unsetting the latch  46 . 
     Referring additionally now to  FIG. 23 , a representative cross-sectional view of a section of the pressure control device  50  as the latch is being unset is representatively illustrated.  FIG. 23  depicts the latch  46  as pressure is applied to the release port  58  to thereby downwardly displace the piston  168 , compressing the spring  170 . 
     If the application of increased pressure to the release port  58  is unsuccessful in downwardly displacing the piston  168 , increased pressure can be applied to the backup release port  60  to cause a backup piston  174  to displace the piston  168  downward and compress the spring  170 . 
     The setting ring  166  can now radially enlarge to permit the setting sleeve  114  to upwardly displace. The setting sleeve  114  is not yet displaced upward as viewed in  FIG. 23 , because the slips  160  remain engaged with the radially reduced outer surface  72   b  on the housing  72 . 
     Referring additionally now to  FIG. 24 , a representative cross-sectional view of the latch  46  in its unset configuration is representatively illustrated. The previously applied downwardly directed force has been removed, and the releasable assembly  40  has been displaced upward somewhat relative to the outer housing  52 , while pressure remains applied to the release port  58 . 
     As the downwardly directed force applied to the releasable assembly  40  is reduced, the springs  116 ,  140  cause the iris mechanism  62  to be actuated to its radially retracted configuration. Thus, the iris segments  106  are displaced radially inward to prevent the external shoulder  64  on the running tool  56  from displacing upward through the iris mechanism  62 . 
     The spring  118  causes the setting sleeve  114  and slips  160  to displace upward. The setting sleeve  114  can displace upward due to the setting ring  166  having previously been allowed to radially expand (when the piston  168  is displaced downward in response to the pressure applied to the release port  58 ). 
     Such upward displacement of the slips  160  relative to the slip housing  164 , assisted by the springs  162 , causes the slips  160  to displace radially outward and out of engagement with the housing  72 . At this point, the releasable assembly  40  can be conveyed upwardly out of the outer housing  52  and retrieved from the riser string  12 . 
     Referring additionally now to  FIG. 25 , a representative cross-sectional view of the replaceable assembly  40  and running tool  56  as retrieved from the outer housing  52  is representatively illustrated. The releasable assembly  40  and running tool  56  are in substantially the same configuration as depicted in  FIG. 24 , but are retrieved from the riser string  12 . Maintenance or replacement of the releasable assembly  40  can now be performed. 
     It may now be fully appreciated that the above disclosure provides significant advancements to the art of constructing and operating pressure control devices and running tools therefor. The above examples provide for convenient and reliable installation, operation and retrieval of components of pressure control devices. 
     In one respect, the above disclosure provides to the art a method of conveying a replaceable assembly  40  between latched and unlatched configurations with an outer housing  52 . In one example, the method comprises connecting the replaceable assembly  40  to a running tool  56 , the replaceable assembly  40  being thereby conveyed with the running tool  56 ; disconnecting the replaceable assembly  40  from the running tool  56 ; and at least one of the connecting and the disconnecting steps comprising actuating an iris mechanism  62  between extended and retracted configurations. 
     The actuating step may comprise rotating each of multiple segments  106  of the iris mechanism  62  about a respective first axis  154  that is parallel to a second axis  156  of a longitudinal passage  54  formed through the replaceable assembly  40 . The segments  106  may rotate as the segments  106  displace radially relative to the longitudinal passage  54 . 
     The replaceable assembly  40  may comprise at least one annular seal  42  that seals about a tubular (such as tubular string  20 ) positioned in a passage  54  formed longitudinally through the replaceable assembly  40 . The replaceable assembly  40  may further comprise a bearing  90 ,  92  that permits relative rotation between the annular seal  42  and the outer housing  52 . 
     The connecting step may comprise the iris mechanism  62  in the retracted configuration limiting relative displacement between the replaceable assembly  40  and the running tool  56 . 
     A pressure control device  50  is also provided to the art by the above disclosure. In one example, the pressure control device  50  can comprise at least one annular seal  42  configured to seal about a tubular (such as tubular string  20 ) disposed in a longitudinal passage  54  formed through an outer housing  52  of the pressure control device  50 ; and a latch  46  that releasably secures the annular seal  42  relative to the outer housing  52 , the latch  46  comprising at least one grip member (such as slips  160 ) that grips a surface  72   b  and prevents relative rotation when the grip member  160  engages the surface  72   b.    
     The annular seal  42  may be connected to an outer housing  72  of a replaceable assembly  40 , and the grip member  160  may grippingly engage the surface  72   b  on the replaceable assembly outer housing  72 . 
     The replaceable assembly  40  may include at least one bearing  90 ,  92  that permits relative rotation between the annular seal  42  and the replaceable assembly outer housing  72 . 
     The grip member  160  may displace between engaged and disengaged positions in response to relative displacement between the grip member  160  and the pressure control device outer housing  52 . 
     The grip member  160  in the engaged position may prevent relative longitudinal displacement between the annular seal  42  and the pressure control device outer housing  52 . 
     The grip member  160  may be displaceable with a setting sleeve  114  between engaged and disengaged positions, and a biasing device (such as spring  118 ) may prevent the setting sleeve  114  from displacing from the engaged position to the disengaged position. A biasing force exerted by the biasing device (such as spring  118 ) may be overcome by a predetermined pressure applied to the latch  46 , which application of pressure permits the grip member  160  and setting sleeve  114  to displace to the disengaged position. 
     Also described above is a pressure control device  50  example that can include at least one annular seal  42  configured to seal about a tubular (such as tubular string  20 ) disposed in a longitudinal passage  54  formed through an outer housing  52  of the pressure control device  50 , the annular seal  42  being connected to and rotatable with an inner mandrel  70 , and at least one bearing  90 ,  92  that permits relative rotation between the annular seal  42  and the outer housing  52 . At least one structure  88  rotates with the inner mandrel  70 , the structure  88  including a flow inductive profile  108  exposed to a lubricant flow path  98  in communication with the bearing  90 ,  92 . 
     The flow inductive profile  108  may comprise vanes on the inner mandrel  70 , or a helical profile disposed in an annular section of the lubricant flow path  98 . 
     The lubricant flow path  98  may be in communication with a lubricant chamber  100  in which pressure is maintained greater than pressure in the longitudinal passage  54 . 
     The pressure control device  50  may include an iris mechanism  62  that selectively permits and prevents relative longitudinal displacement in at least one direction between the annular seal  42  and a running tool  56 . 
     The pressure control device  50  may include a latch  46  that releasably secures the annular seal  42  relative to the outer housing  52 , the latch  46  comprising at least one grip member  160  that grips a surface  72   b  and prevents relative rotation when the grip member  160  engages the surface  72   b.    
     The pressure control device  50  may include a setting sleeve  114  displaceable between engaged and disengaged positions, and a biasing device (such as spring  170 ) that prevents the setting sleeve  114  from displacing from the engaged position to the disengaged position. A predetermined pressure applied to the latch  46  may overcome a biasing force exerted by the biasing device (such as spring  170 ) and permit the setting sleeve  114  to displace to the disengaged position. 
     Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example&#39;s features are not mutually exclusive to another example&#39;s features. Instead, the scope of this disclosure encompasses any combination of any of the features. 
     Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used. 
     It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments. 
     In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein. 
     The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.” 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, 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 invention being limited solely by the appended claims and their equivalents.