Floating platform top connector

A segmented ring forms a set of latches for a tendon top connector on a floating platform. The latches reside in a housing and have either a groove or thread profile on an upper internal surface. The grooves interface with a mating groove profile on the tendon. The latches rotationally pivot backward and forward from the outer portion of the bottom surface. When the latches are forward, the profile in the internal surface engages the mating profile of the tendon top joint. When the latches are swung out, these profiles clear and permit the top joint to pass through the connector. Retraction of the latches is provided by application of force on the inside surface of an annular extension on the outer portion of the latches. This force can be provided by a variety of actuators. This top connector allows for passive dynamic engagement of the connector to the tendon top joint. When the latches are permitted to move inward, contact is made with the mating profile on the tendon top joint. Downward movement of the tendon relative to the connector causes the passing profile of the top joint to engage the profile of the latches and engage the latches into the top joint. Upward movement of the tendon relative to the connector causes the latches to be pivoted out of the way, allowing the top joint to pass through the connector unrestricted.

TECHNICAL FIELD 
This invention relates in general to top connectors for floating platforms 
and in particular to an improved tendon and riser top connector for a 
tension leg platform. 
BACKGROUND ART 
The concept described in this disclosure is primarily used for connection 
of a mooring tendon to the hull of a tension leg platform. However, this 
concept also has use for attachment of drilling or production risers of 
any type of floating platform (TLP, Spar, etc.) to the riser tensioning or 
support system on the platform. Both of these systems must make an 
attachment of a top tubular member to the platform support structure and 
provide for adjustment in overall length of the tendon or riser. 
Previous systems have typically made use of some form of slip segments that 
had a threaded or grooved interface to the top joint of the tendon. These 
slip segments typically slide down the taper, or slide and rotate in 
combination to engage the tendon top section. These systems have used 
either elaborate internal drive systems and/or actuation tools to engage 
and disengage the connector on and off of the tendon top joint. In 
addition, these systems have either required the tendon to be statically 
restrained or substantially over-tensioned and then relieved for 
engagement. 
DISCLOSURE OF INVENTION 
The concept described in this disclosure is based on a segmented ring that 
forms a set of latches. These latches reside in a housing and have either 
a thread or groove profile on the upper internal surface. The grooves 
interface with a mating groove profile in the tendon top joint. These 
latches rotationally pivot backward and forward from the outer portion of 
the bottom surface. When the latches are forward, the profile in the 
internal surface engages the mating profile of the tendon top joint. When 
the latches are swung out, these profiles clear and permit the top joint 
to pass through the connector. The latches utilize either weight, spring 
force or a combination thereof to move the latches inward. Retraction of 
the latches is provided by application of force on the inside surface of 
an annular extension on the outer portion of the latches. This force can 
be provided by a variety of actuators which may be hydraulically or 
mechanically operated. 
The concept described in this disclosure allows for passive dynamic 
engagement of the connector to the tendon top joint. When the latch 
segments are permitted to move inward, contact is made with the mating 
profile on the tendon top joint. Downward movement of the tendon top joint 
relative to the connector (or hull of the TLP) causes the passing profile 
of the top joint to engage the profile of the latches and engage the 
latches into the top joint. Upward movement of the tendon top joint, 
relative to the connector, causes the latches to be pivoted out of the 
way, allowing the top joint to pass through the connector unrestricted. 
Release of the latches to allow downward movement of the top joint 
relative to the connector is once again accomplished by pulling the 
latches back out of position.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring to FIG. 1, a top connector 11 for attachment to a top joint or 
upper termination of a tendon riser or tubular member 13 is shown. Top 
connector 11 is provided for adjusting the length of tendon 13. Tendon 13 
contains a section of continuous external threads or grooves 15 at an 
upper termination of tendon 13. Top connector 11 is the upper end joint of 
the entire tendon 13 and provides the load transfer from a supporting 
structure into tendon 13. Top connector 11 resides in a receptacle 35 
located on the platform. 
Top connector 11 utilizes a cylindrical connector housing 21 to transfer 
loads back into the supporting structure. Housing 21 is supported at an 
outer lower surface by a flexible element 25 having a central elastomer 
27. Flexible element 25 is secured to housing 21 with a flexible retainer 
29. Housing 21 has a central cavity or bore 23 which receives tendon 13. 
In the embodiment shown, flexible element 25 is secured to a load flange 
31 with a plurality of bolts 33. Load flange 31 is landed on receptacle 35 
which is on the platform. In an alternate embodiment, housing 21 may be 
connected directly to a load bearing surface on the platform or tensioning 
device. 
Referring to FIG. 2, a plurality of latches 41 are carried in bowl 21a of 
housing 21. Latches 41 contain a thread or groove profile 43 on their 
upper inner surface which interfaces with grooves 15 on tendon 13. Grooves 
43 are tapered generally in a convex profile with larger, deeper grooves 
43a at the top and smaller, shallower grooves 43b on a lower side (FIG. 
3). Grooves 15, however, are of uniform depth. When top connector 11 is 
engaged into the thread or groove profile 15 of tendon 13, the loads pass 
from tendon 13 into latches 41, through housing 21, and into the support 
structure. 
Latches 41 rotationally pivot in housing 21 on their outer bottom surfaces. 
Latches 41 engage grooves 15 when latches 41 pivot inward as shown in FIG. 
2, and disengage when they pivot or rock outward as shown in FIG. 3. The 
lower surface of latches 41 engage a mating load surface or bowl 21a in 
housing 21 when latches 41 are in the engaged position. A protruding rib 
69 on the bottom of each of latches 41 engages a recess or mating pivot 
member groove 21b at an outer edge of bowl 21a. The lower side of rib 69 
forms a pivot point for each latch 41. Latches 41 are forced inward by 
weight, a spring force or a combination of the two. 
Latches 41 have a vertically extending outer arm or rim 45 on an outer 
portion. When sufficient force is exerted on an inner surface or taper 47 
of rim 45, latches 41 are pivoted back about ribs 69, thereby retracting 
latches 41 and disengaging them from tendon 13. The preferred 
configuration of taper 47 of rim 45 is to have an upward facing surface at 
the top and a slightly reversed, downward facing tapered surface 49 just 
below. 
This configuration allows an actuation device 51 to use a lower profile 51a 
that is reversed from that of tapers 47, 49. A variety of actuation 
devices may be used to apply a force for this purpose. When the force is 
removed, latches 41 are again forced into contact with grooves 15 of 
tendon 13. Actuation tool 51 cams-back the extended rim 45 of latches 41, 
thereby retracting them. When actuation tool 51 engages far enough such 
that cam or profile 51a and tapers 47, 49 engage (FIG. 3), the closing 
force of latches 41 holds the two mating profiles together, thus keeping 
latches 41 in the retracted position. 
In the embodiment shown, actuation tool 51 comprises a main body 53, an 
upper body 55 and seals 54 therebetween. A cavity 55a is defined between 
main body 53 and upper body 55. An annular piston 57 slidingly 
reciprocates within cavity 55a and is sealed to main body 53 with seals 56 
and to upper body 55 with seals 58. Actuating tool 51 has a split latch 
ring 59 which is radially moveable relative to actuating tool 51. Latch 
ring 59 is mounted in an outer lower surface or recess 53a in main body 
53. Actuating tool 51 is latched to a recess 63 in housing 21 by a set of 
pins 61. Pins 61 are vertically or axially moveable within bodies 53, 55 
to engage latch ring 59. 
When latches 41 are first engaged into tendon 13, it is very unlikely that 
the mating grooves of each piece will align. However, as top connector 11 
moves downward relative to tendon 13, grooves 43 will gradually engage 
grooves 15 until the load surfaces of the two profiles come into contact. 
The angle of the load surface is shallower than the angle at which grooves 
43 are approaching grooves 15. This causes grooves 15 to first capture 
grooves 43b before grooves 43a (FIG. 3). As tension load is applied to 
tendon 13, grooves 43a are set deeper than grooves 43b so that a small gap 
remains between grooves 43b and grooves 15 (FIG. 2). Therefore, latches 41 
pivot inward until the stab flanks of grooves 43 come into contact and 
provide a balancing force. This configuration ensures that latches 41 will 
always set themselves under load. 
The stab flanks of grooves 43 are of a sufficiently steep angle that tendon 
13 will pivot latches 41 back out of the way as tendon 13 moves upward 
relative to top connector 11. In this manner, tendon 13 is passively 
restrained from passing down through connector 11, but is unrestrained 
from passing up through connector 11. This permits dynamic lock-offs of 
connector 11 relative to tendon 13. 
Latches 41 are held in place by an annular retainer 65 that attaches to an 
inner surface of housing 21 just above rib 69 of latches 41. The bottom of 
retainer 65 has a spherical surface 67 which mates with an upward facing 
shoulder 70 above rib 69. Shoulder 70 and rib 69 are curved and generally 
convex, thereby allowing the lower portion of rib 69 to act as an arcuate 
pivot point. An inward-biased split ring 71 is housed in an inner portion 
of retainer 65 and is used to provide supplemental engagement force to 
latches 41. Split ring 71 contacts an outer wall 41a of each latch 41 to 
urge them inward. A set of keeper pins 73 are installed between retainer 
65 and housing 21. Keeper pins 73 also pass through slots in latches 41 
and prevent each latch 41 from rotating about the axis of tendon 13. 
In an alternate configuration (not shown), pins 73 do not engage or extend 
into these slots. Instead, actuation tool 51 contains pins that engage 
these slots. In this latter configuration, actuation tool 51 is provided 
as a means for rotating latches 41 relative to the longitudinal axis of 
tendon 13. With threaded latches 41, this provides the ability to make 
continuous adjustment of the position of connector 11 relative to tendon 
13. 
A synchronizer 74 having a guidance sleeve 75 is attached to tendon 13 at 
bore 23 of housing 21. The bore of sleeve 75 is only slightly larger in 
diameter than the outside of tendon 13. This allows sleeve 75 to provide 
close-centered, angular alignment with tendon 13. In FIG. 3, connector 11 
is shown prior to alignment with tendon 13. A lower inner surface 77 of 
latches 41 is partially spherical and concave and engaged by a convex 
mating profile 81 on a synchronizer ring 79. Ring 79 is free to slide up 
and down on the upper outside surface of sleeve 75. Synchronizer 74 
ensures that the movement of each latch 41 is timed with the others as 
they engage tendon 13. A retainer ring 83 at the base of housing bowl 21a 
provides a lower stop for ring 79. 
Top connector 11 is assembled by resting flexible element 25 on housing 21 
with housing 21 upside down, and attaching flexible element 25 by 
installing flexible element retainer 29. Guide sleeve 75 is then passed 
through housing 21. Split retainer ring 71 is then expanded and slid into 
place over the top of sleeve 75 and into the groove of the outside of 
sleeve 75. 
To install latches 41, a lifting clamp (not shown) is attached to rims 45 
around latches 41. Latches 41 are then lifted and synchronizer 74 is slid 
into the bottom of latches 41 and placed into position. The 
latches/synchronizer combination is then lowered into housing 21 (that is 
not uprighted), and the lifting clamp is removed. Split ring 71 is 
collapsed and then inserted into its groove in retainer 65. Retainer 65 
and spring 71 are then inserted to housing 21 and attached in place by 
installing keeper pins 73. The assembly is then lowered into load flange 
31 and attached to it by installing bolts 33. 
In operation, actuation tool 51 is installed and hydraulic pressure is 
applied to it to move piston 57 downward. The downward movement of piston 
57 causes latches 41 to pivot or rock outward. Latches 41 are held in a 
retracted position by actuation tool 51 as shown in FIG. 3. Ballast is 
added to the vessel which moves top connector 11 downward relative to 
tendon 13. When connector 11 is at its generally desired elevation 
relative to tendon 13, the hydraulic pressure is relieved. Spring 71 then 
forces latches 41 to rock forward. Latches 41 are held from engagement by 
crest-to-crest contact of grooves 15 and 43. This condition can occur when 
tendon 13 is either moving downward relative to the connector 11 and 
engaging latches 41, or moving upward relative to latches 41 and pivoting 
them out of engagement. FIG. 4 shows latches 41 fully engaged to tendon 
13. After installation, pin 61 is lifted to retract latch ring 59 back 
into recess 53a so that actuation tool 51 can be removed from connector 
11. Latches 41 keep top connector 11 from moving upward relative to tendon 
13. 
The invention has several advantages. Rocking latches and a simple 
actuation tool are used to engage and disengage the connector on and off 
of the tendon top joint; an elaborate internal drive system is not 
required. This invention also eliminates the need to statically restrain 
or substantially overtension the tendon for engagement. 
While the invention has been shown in only some of its forms, it should be 
apparent to those skilled in the art that it is not so limited, but is 
susceptible to various changes without departing from the scope of the 
invention.