Patent Publication Number: US-2015059903-A1

Title: Methods and apparatus for arresting failures in submerged pipelines

Description:
BACKGROUND 
     This disclosure relates generally to offshore pipelines, and more specifically to methods and apparatus for responding to failures in offshore submerged pipelines. 
     In offshore pipeline installations, as the pipeline is laid on the sea floor the pipeline is subjected to significant forces and moments that can compromise the integrity of the pipeline and, in some cases, cause failures. In the event the submerged pipeline is compromised to the point of failure, water rushes into the pipeline. Such failures are commonly referred to as wet buckles. Once a wet buckle occurs the flooded pipeline is too heavy to retrieve for repair and re-installation. 
     Companies that lay the pipeline keep a fleet of compressor ships on standby while the pipeline is being laid on the sea floor in case of a failure like a wet buckle. The compressor ships are present to pump the water out of the pipeline to facilitate repair of the buckled section, by allowing the pipeline to be pulled back to the surface, to the pipelay vessel, for removal of the damaged section. After the water has been removed, sections of the damaged pipeline can be retrieved and brought to the surface and the pipelay vessel can continue laying pipe onto the sea floor. 
     Pipeline failures like wet buckles are relatively rare. As such, during installation, the fleet of compressor ships hired by the pipeline installation company is generally inactive and serves no function for the installation process unless the rare failure occurs. The cost of the compressor ships and the associated service the ships and crew provide can reach the millions of dollars. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  schematically depicts a submerged pipeline installation system including wet buckle packers in accordance with this disclosure. 
         FIG. 2  depicts an elevation view of an example wet buckle packer in accordance with this disclosure. 
         FIG. 3A  depicts a section view of the example packer of  FIG. 2  in an unengaged state within a pipeline. 
         FIG. 3B  depicts a section view of the example packer of  FIG. 2  in an engaged state within a pipeline. 
         FIG. 4  depicts an elevation view of another example wet buckle packer in accordance with this disclosure. 
         FIG. 5  depicts an example method of arresting a failure in a submerged pipeline. 
     
    
    
     DETAILED DESCRIPTION 
     In view of the foregoing costs and other inefficiencies associated with recovering from an offshore pipeline failure, examples according to this disclosure are directed to methods and apparatus for automatically responding to water invasion into the inner diameter of pipe in an offshore pipeline and rapidly deploying a sealing system that will prevent or inhibit the laid pipeline from being flooded with water. 
     A packer apparatus in accordance with this disclosure is configured to be arranged within and arrest a failure of a submerged pipeline. In one example, the packer apparatus includes first, second and third mandrels, a brake, and first and second elastomeric expansion boots. The first and second mandrels are in axial moveable relation with the third mandrel, which is arranged between the first and second mandrels. The brake is arranged between the first and second mandrels. The first elastomeric expansion boot is arranged between a radially extending flange of the first mandrel and a first radially extending flange of the third mandrel. The second elastomeric expansion boot is arranged between a radially extending flange of the second mandrel and a second radially extending flange of the third mandrel. The first mandrel is configured to move axially toward the third mandrel from a first position to a second position. The second mandrel is configured to move axially toward the third mandrel from a first position to a second position. 
     In the second position of the first mandrel, the radially extending flange of the first mandrel is closer to the first radial extending flange of the third mandrel than in the first position, and the first expansion boot is compressed axially between the radially extending flange of the first mandrel and the first radially extending flange of the third mandrel and is expanded radially into engagement with an inner surface of the pipeline. In the second position of the second mandrel, the radially extending flange of the second mandrel is closer to the second radial extending flange of the third mandrel than in the first position, and the second expansion boot is compressed axially between the radially extending flange of the second mandrel and the second radially extending flange of the third mandrel and is expanded radially into engagement with an inner surface of the pipeline. Additionally, in the second position of the first and second mandrels, the brake moves radially outward into engagement with the inner surface of the pipeline. 
     In the following examples, the apparatus for arresting pipeline wet buckles (and other pipeline failures) is referred to as a wet buckle packer. However, the apparatus could also be referred to as a plug, a shutoff pig, a baffle, or other terms connoting a device that restricts, and ideally prevents fluid flow through an annular pipeline. 
     Wet buckle packers in accordance with this disclosure provide a number of functions once actuated. Packer apparatus in accordance with this disclosure are sometimes referred to as configured to arrest a failure like a wet buckle in a submerged pipeline. Arresting a failure in a pipeline includes a number of different functions. In both dry and wet buckles, for example, the pipeline failure can include a structural failure including a buckle that causes the pipeline to at least partially collapse on itself. The structural buckle can run along the length of the pipeline unless it is arrested. In wet buckles, water also invades the inner diameter of the pipe causing the pipeline to become flooded. Packer apparatus in accordance with this disclosure can function to arrest both a structural buckle in a submerged pipeline, whether from a dry or wet buckle, and deploy a sealing system that will prevent or inhibit the laid pipeline from being flooded with water in the event of a wet buckle. The packer seals the inner diameter of the pipeline to prevent or significantly inhibit water from flooding the submerged pipeline. Additionally, the packer deploys a braking mechanism to prevent or inhibit the packer from moving within the pipeline under the significant pressures introduced by the sea (or fresh) water entering the pipe from the wet buckle. 
     As noted above, wet buckle packers in accordance with this disclosure are configured to be automatically actuated to seal the pipeline from ingress of water. The mechanisms for sealing and braking employed in a wet buckle packer can be actuated in a variety of ways. For example, electrical, hydraulic, or pneumatic supply lines can be run from the pipelay vessel on the surface to the packer. The wet buckle packer could also include a power source, e.g., a battery that could be used to actuate the seal and brake mechanisms. The packers or the systems in which they are employed can be configured to be actuated automatically using a variety of different sensors configured to detect water invasion into the pipeline. 
     Wet buckle packers in accordance with this disclosure provide a new approach to seal and anchor a packer-type plug in place within a pipeline in the event of a wet buckle. The packers are designed to provide increased durability and to include component parts that protect against external variances. Example wet buckle packers can provide a number of advantages including, e.g., removing the high cost of air compressor standby in submerged pipeline installations and providing a simple and cost effective device for arresting failures in the pipeline. 
       FIG. 1  depicts a submerged pipeline installation system  10 . Offshore submerged pipelines can be installed in a number of ways. In general, individual pipes are transported by a cargo ship to a pipelay vessel at the pipeline installation location. The individual pipes are processed and connected to one another on the pipelay vessel and laid onto the sea floor. The pipelay vessel progressively welds individual pipes or welded pipe sections to one another to assemble the pipeline. As the pipeline is assembled the pipelay vessel moves across the surface of the water and the assembled pipeline is pulled off of the ship by the weight of the pipeline. As the pipeline is progressively pulled off of the back of the pipelay vessel it descends to the sea floor. 
     Two methods that are employed to install submerged pipelines are the “J” lay and the “S” lay. The moniker of each method represents the shape of the pipeline as it is pulled off of the pipelay vessel onto the sea floor. In a “J” lay, the pipeline is pulled off of the pipelay vessel substantially vertically to near the sea floor, where the pipeline bends to run horizontally along the floor. In an “S” lay, the pipeline is pulled off of the pipelay vessel substantially horizontally, bends vertically down toward the sea floor and then bends back horizontally away from the vessel to run along the sea floor. Although the following examples are described in the context of an “S” lay installation, wet buckle packers in accordance with this disclosure can also be employed in a “J” lay installation system or other pipeline installation methods not covered here. 
       FIG. 1  depicts a submerged pipeline installation system  10  for an “S” lay installation. In  FIG. 1 , system  10  includes pipelay vessel  12  and pipeline  14 . Pipelay vessel  12  includes production factory  16 , tensioners  18 , crane  20 , and stinger  22 . As described in more detail below, after individual pipes are transported to and loaded on pipelay vessel  12 , the pipes are conveyed into production factory  16 . Production factory  16  includes a variety of processing stations for preparing pipes and coupling individual pipes into pipe sections and ultimately assembling pipeline  14 , as will be known to persons skilled in the art. 
     Pipelay vessel  12  is shown floating in a body of water  24 . Pipelay vessel  12  utilizes crane  20  to perform heavy lifting operations, including loading pipes from a cargo ship onto the vessel. In general, individual pipes on board pipelay vessel  12  are placed on an assembly line within production factory  16  and joints of the pipes are welded into pipeline  14 . Pipeline  14  is held in tension between sea floor  26  and pipelay vessel  12  by pipeline tensioners  18  as the pipeline is lowered. As pipelay vessel  12  moves forward by pulling on a mooring system off of the bow, pipeline  14  is lowered from pipelay vessel  12  over stinger  22 . Stinger  22  is attached to and extends from the stern of pipelay vessel  12 , and provides support for pipeline  14  as it leaves pipelay vessel  12 . 
     In practice, a cargo ship transports pipe sections (sometimes referred to as stands) to pipelay vessel  12 . Crane  20  moves pipe sections from the cargo ship to pipelay vessel  12  onto cradles that form a conveyor system for moving pipe into production factory  16 . Within production factory  16 , a number of different operations are carried out to prepare and join pipe sections. For example, the pipe ends are beveled (and bevels are deburred). The pipe ends are preheated within production factory  16  and moved through a number of welding stations to join different sections with weld beads applied both to the outer and inner diameters of the sections at the joints. In some cases, a final welding station within production factory  16  applies a welded cap to the joints of pipe sections. 
     The joints of the welded pipe sections can also be tested within production factory  16 . For example, the welded joints can pass through ultrasonic testing stations that apply water to the joints as the medium to transmit the ultrasonic signals. The ultrasonic signals can be processed by a computing system and graphically displayed for inspection by an operator. 
     After testing, the joints of the welded pipe sections can be grit blasted and a field joint coating can be applied. In some installation systems, each individual pipe is subjected to this process as it is welded to pipeline  14 . In other cases, multiple pipes, e.g. two pipes in a double stand facility, are first welded together and then welded to the pipeline in the firing line onboard pipelay vessel  12 . At any rate, the assembled pipeline  14  is ultimately conveyed through tensioners  18  and over stinger to be dropped off of the stern of pipelay vessel  12  to sea floor  26 . 
     As pipeline  14  is laid on sea floor  26 , suspended pipe span  28  forms a shallow “S” shape between sea floor  26  and pipelay vessel  12 . The “S” shape of suspended pipe  28  is sometimes referred to as the S-curve. Second curve  30  or the tail of the S-curve just before suspended pipe span  28  meets sea floor  26  is sometimes referred as the “sagbend.” The S-curve of pipeline  14  is controlled by stinger  22  and pipeline tensioners  18 . Increases in the curvature of pipeline  14  cause increases in the bending moment on the pipeline, and, as a result, higher stresses. High stresses on pipeline  14  and, in particular, on suspended pipe span  28  can result in buckling of the pipeline  14 . For example, a loss of tension in pipeline  14  during the pipe lay will normally cause pipeline  14  to buckle at a point along the suspended pipe span  28 . A buckle in pipeline  14  is called a wet buckle if pipeline  14  has cracked or becomes damaged in such a manner that water is allowed to enter the inner diameter of the pipeline. The influx of water into the pipeline  14  greatly increases the weight of suspended pipe span  28  such that the pipe can become over stressed at a location along suspended pipe span  28 , generally near stinger  22 . In such circumstances, flooded pipeline  14  can break and drop from pipelay vessel  12  to sea floor  26 . Regardless of whether pipeline  14  breaks in the event of a wet buckle, the increased weight can prevent recovery of and repair to pipeline  14  before the water is pumped out of the pipeline. 
     Examples according to this disclosure are directed to a wet buckle packer that can be deployed within the inner diameter of pipeline  14  as it is laid on sea floor  26 . In  FIG. 1 , installation system  10  includes two wet buckle packers  32  and  34  deployed within pipeline  14 . Packer  32  is deployed along suspended pipe span  28 , while packer  34  is deployed downpipe where pipeline  14  meets sea floor  26 . Wet buckle packers  32  and  34  are deployed within pipeline  14  with a hoist line or cable (not shown). In cases where multiple wet buckle packers are deployed in series, a hoist line may be coupled between the packers. In the example of  FIG. 1 , a hoist line may be coupled to a hoist on pipelay vessel  12  to packer  32  and another line can be coupled between packers  32  and  34 . As will be apparent to persons skilled in the art, substantial benefits can be realized through an alternative configuration using only a single wet buckle packer, located generally in the position of depicted packer  34 , positioned to prevent substantial inflow of water into the already-laid portion of pipeline  14  on sea floor  26 . 
     Wet buckle packers  32  and  34  are configured to automatically respond to water invasion into the inner diameter of pipeline  14  and rapidly deploy a sealing system that will prevent the laid pipeline and pipeline above packer  32  from being flooded with sea water. For example, wet buckle packers  32  and  34  seal the inner diameter of pipeline  14  to prevent or significantly inhibit water from flooding the submerged pipeline. Additionally, wet buckle packers  32  and  34  deploy a braking mechanism to prevent or inhibit the packers from moving within pipeline  14  as a result of the pressures introduced by the sea water entering the pipe from the wet buckle. 
     In some cases one or more “piggy-back” lines may be laid from pipelay vessel  12  along with main pipeline  14 . Piggy-back lines are generally constructed from smaller diameter pipes that are assembled in a similar manner as described above with reference to pipeline  14 . The piggy-back lines are assembled in parallel with and are then coupled to pipeline  14 , e.g., with a sleeve connected to top of the main pipeline  14  in which the piggy-back lines are received. 
       FIG. 2  depicts example wet buckle packer  100 . Packer  100  includes a hoist ring  102 , end caps  104  and  106 , bearings  108  and  110 , first and second mandrels  112  and  114 , expansion boots  116  and  118 , a third mandrel  120 , and a brake assembly  122 . Packer  100  is configured such that similarly configured components are arranged axially on both ends of a central assembly including third mandrel  120  and brake assembly  112 , disposed generally in the middle of packer  100 . End caps  104  and  106  generally define either end of packer  100 . Caps  104  and  106 , bearings  108  and  110 , and first and second mandrels  112  and  114  are connected to one another via fasteners (not shown), such as bolts, received within apertures  124 . Expansion boot  116  is disposed between first mandrel  112  and third mandrel  120 . Similarly, expansion boot  118  is disposed between second mandrel  114  and third mandrel  120 . Packer is coupled to hoist line  113  by hoist ring  102 , which is connected to cap  104 . 
     Packer  100  is configured to be connected to hoist line  113  and deployed from a pipelay vessel down a submerged pipeline. Packer  100  can be lowered into an already submerged pipeline or can be lowered along with a particular section of the pipeline as it is lowered to the sea floor. Bearings  108  and  110  each include a number of freely rotating wheels  126  distributed around the outer circumference of the bearings. Wheels  126  facilitate travel of packer  100  through the submerged pipeline as packer  100  is lowered from the pipelay vessel and as otherwise may be needed during the pipe laying process. 
     Packer  100  can be deployed at a number of locations within the submerged pipeline to arrest pipeline failures like wet buckles. For example, packer  100  can be deployed along a suspended pipe span of the pipeline or further downpipe where the pipeline meets the sea floor. Wet buckle packer  100  is configured to automatically respond to water invasion into the inner diameter of the pipeline and rapidly deploy a sealing system that will prevent the laid pipeline and pipeline above packer  32  from being flooded with sea water, which is described in more detail with reference to  FIGS. 3A and 3B . 
       FIGS. 3A and 3B  depict section views of wet buckle packer  100  within pipeline  128 . In  FIG. 3A , packer  100  is unengaged with pipeline  128 . In  FIG. 3B , packer  100  is engaged with pipeline  128  to substantially seal the inner diameter of pipeline  128  from water invasion. As illustrated in the section views of  FIGS. 3A and 3B , packer  100  includes actuator  129  in addition to hoist ring  102 , end caps  104  and  106 , bearings  108  and  110 , first and second mandrels  112  and  114 , expansion boots  116  and  118 , third mandrel  120 , and brake assembly  122 . Actuator  129  and brake assembly  122  are connected to both first and second mandrels  112  and  114 . Supply line  131  is coupled to actuator  129 . Supply line  131  is schematically illustrated in  FIGS. 3A and 3B  in a dashed line format. 
     Caps  104  and  106 , bearings  108  and  110 , and first and second mandrels  112  and  114  can be connected to one another in a variety of ways. In the example of  FIGS. 3A and 3B , caps  104  and  106 , bearings  108  and  110 , and first and second mandrels  112  and  114  are connected to one another via fasteners (not shown) received within apertures  124 . In another example, however, caps  104  and  106 , bearings  108  and  110 , and first and second mandrels  112  and  114  could be welded to one another. 
     First and second mandrels  112  and  114  are configured to move axially relative to third mandrel  120 . Third mandrel  120  includes an “I” shaped cross-section with two end plates  130  and  132  connected by a central shaft  134 . First and second mandrels  112  and  114  each include a “T” shaped cross-sectional shape. First mandrel  112  includes end plate  136  and central shaft  138 . Second mandrel  114  includes end plate  140  and central shaft  142 . Shaft  138  of first mandrel  112  is received within a bore in shaft  134  at one end of third mandrel  120 . Shaft  142  of second mandrel  114  is received within the bore of shaft  134  at the other end of third mandrel  120 . Each of first and second mandrels  112  and  114  are configured to move axially relative to third mandrel  120  from the ends toward the middle of packer  100 . 
     Actuator  129  is connected to both first and second mandrels  112  and  114  and is disposed within the bore of central shaft  134  of third mandrel  120 . Actuator  129  is depicted schematically in  FIGS. 3A and 3B , but generally includes housing  144  and shaft  146  movably connected to housing  144 . Shaft  146  is configured to slide in and out of housing  144 . Housing  144  is connected to second mandrel  114 . Shaft  146  is pivotally connected to first mandrel  112  via clevis  148  connected to the end of shaft  146 . 
     Actuator  129  can be a variety of mechanical and electromechanical devices that are configured to be actuated to cause shaft  146  to move axially relative to housing  144 . For example, actuator  129  can include a pneumatically or hydraulically actuated piston that drives shaft  146  with air or a hydraulic fluid supplied by supply line  131 . In another example, actuator  129  includes an electrically activated solenoid that drives shaft  146 . In another example, actuator  129  includes an electromagnetic piston that drives shaft  146  based on controlled electricity transmitted to packer  100  via supply line  131 . In another example, actuator  129  includes an electric motor and screwjack, which can drive shaft  146  using electricity transmitted to packer  100  via supply line  131 . In some cases, actuator  129  can be powered by a power source like a battery deployed with packer  100 . 
     Actuator  129  is configured to cause the distal end of shaft  146  (i.e., the end coupled to first mandrel  112  via clevis  148 ) to move axially relative to housing  144 . As the distal end of shaft  146  changes axial position with respect to housing  130 , first and second mandrels  112  and  114  move relative to one another and to third mandrel  120  arranged between the two first and second mandrels. 
     Expansion boots  116  and  118  are annular elastomeric boots that surround shaft  138  of first mandrel  112  and shaft  142  of second mandrel  114 , respectively. Expansion boot  116  is arranged between end plate  136  of first mandrel  112  and end plate  130  of third mandrel  120 . Similarly, expansion boot  118  is arranged between end plate  140  of second mandrel  114  and end plate  132  of third mandrel  120 . 
     As first mandrel  112  moves axially toward third mandrel  120 , expansion boot  116  is compressed axially as plates  136  and  130  move closer to one another. As expansion boot  116  is compressed axially, boot  116  also radially expands into engagement with an inner surface of pipeline  128 . Similarly, as second mandrel  114  moves axially toward third mandrel  120 , expansion boot  118  is compressed axially as plates  140  and  132  move closer to one another. As expansion boot  118  is compressed axially, boot  118  also radially expands into engagement with the inner surface of pipeline  128 . 
     Brake assembly  122  includes a number of brake arms  150 , which are distributed at different angularly disposed, circumferential positions around a longitudinal axis of packer  100 . In the example of  FIGS. 3A and 3B , brake assembly  122  includes four brake arms  150  offset from one another at approximately 90 degrees about the longitudinal axis of packer  100 . However, in other examples, packer  100  or other wet buckle packers in accordance with this disclosure could include more or fewer brake arms. For example, packer  100  could include a brake with three brake arms offset from one another at approximately 120 degrees about the longitudinal axis of packer  100 . In another example, packer  100  could include a brake with five brake arms offset from one another at approximately 72 degrees about the longitudinal axis of packer  100 . Additionally, the brake arms of the wet buckle packer could be unevenly distributed about the longitudinal axis of packer  100  such that the angular offset between different sets of brake arms is different. 
     Brake arms  150  each include two links  152 ,  154  and pad  156  at the radially outward end of link  154 . For each brake arm  150 , link  152  is pivotally coupled to first mandrel  112  at pivot  158 . Link  154  is pivotally coupled to second mandrel  114  at pivot  160 . Links  152  and  154  project toward each other and are pivotally coupled to one another at pivot  162  between first and second mandrels  112  and  114 . Brake pad  156  is pivotally coupled to link  154  at pivot  164  near the end of link  154  opposite the end connected to second mandrel  114 . 
     As first and second mandrels  112  and  114  moves axially toward third mandrel  120 , pivots  158  and  160  are drawn closer together generally axially. Link  152  rotates about pivot  158  and link  154  rotates about pivot  160  and links  152  and  154  pivot relative to one another about pivot  162 . The end of links  152  and  154  adjacent pivot  162  and brake pad  156  are moved radially outward, which pushes brake pad  156  radially outward into engagement with the inner surface of pipeline  128 . As brake pad  156  engages pipeline  128 , pad  156  rotates about pivot  164  to generally align the radially outer face of pad  156  with the inner surface of pipeline  128 . Additionally, the outer surface of brake pad  156  includes a saw-tooth profile defined by a series of circumferentially extending ridges, which are configured to engage the inner surface of pipeline  128  without slipping. In many examples, the ridges will not be symmetrical, but will be configured particularly to prevent movement in the direction toward end cap  106  (i.e., away from the likely location of water influx due to a wet buckle). In one example, pad  156  is manufactured from steel and, in some cases, can include carbide buttons that form the saw-tooth profile of pad  156 . 
     Packer  100  can be actuated from the pipelay vessel on the surface of the sea in the event of a wet buckle in a submerged portion of pipeline  128 , e.g., in the sag bend of the “S” curve formed by the suspended span of pipeline  128  as it descends to the sea floor. Packer  100  can include a sensor system that detects the invasion of water into the inner diameter of pipeline  128 . In another example, the sensor system can be associated with a separate component and be communicatively coupled to packer  100 . In one example, the sensor system includes a water sensor including two spaced electrodes arranged within pipeline  128  such that water invading the pipeline would complete an electrical circuit of the sensor. In another example, a pressure sensor could be used to detect the invasion of water into the inner diameter of pipeline  128 . 
     The sensor system communicatively coupled to packer  100  can provide a signal directly to control electronics included in actuator  129  or can transmit signals to a surface system, which, in turn, transmits control signals to actuator  129  via supply line  131 . In the event water invasion is detected, actuator  129  causes the distal end of shaft  146  to move axially closer to housing  144 . As the distal end of shaft  146  changes axial position with respect to housing  144 , first and second mandrels  112  and  114  are drawn axially toward third mandrel  120 , which functions to axially compress and radially expand expansion boots  116  and  118 . In the radially expanded state illustrated in  FIG. 3B , expansion boots  116  and  118  are configured to substantially seal the inner diameter of pipeline  128  and thereby arrest or mitigate the wet buckle in pipeline  128 . 
     Actuator  129  also deploys brake assembly  122  to prevent or substantially inhibit movement of packer  100  within pipeline  128 . For example, actuator  129  causes the distal end of shaft  146  to move axially closer to housing  144 . As the distal end of shaft  146  changes axial position with respect to housing  144 , first and second mandrels  112  and  114  are drawn axially toward third mandrel  120 . Movement of first and second mandrels  112  and  114  relative to third mandrel  120  causes links  152  and  154  to rotate and push brake pad  156  radially outward into engagement with the inner surface of pipeline  128  to prevent or inhibit packer  100  from moving within the pipeline. 
     Although it is not illustrated in  FIGS. 3A and 3B , packer  100  can include a locking mechanism that is configured to lock brake assembly  122  once it has been engaged. In one example, the locking mechanism includes a ratchet mechanism that is configured to allow first and second mandrels  112  and  114  to move toward third mandrel  120 , while preventing first and second mandrels  112  and  114  from moving away from third mandrel  120  after brake assembly  122  has been engaged. An example ratchet mechanism that could be configured for use with packer  100  is disclosed and described in described in U.S. application Ser. No. ______ (Atty. Docket No. 1880.517US1), filed Jul. ______, 2013 and entitled “METHODS AND APPARATUS FOR ARRESTING FAILURES IN SUBMERGED PIPELINES,” the entire contents of which are incorporated herein by reference. 
     Packer  100  is configured such that in the unengaged state illustrated in  FIG. 3A  the outer boundaries of packer  100  are offset from the inner surface of pipeline  128 . The offset distance between packer  100  and the inner surface of pipeline  128  may differ at different points along the axial length of packer  100 . For example, offset  166  between expansion boots  116  and  118  and the inner surface of the pipeline  128  is different than offset  168  between brake pads  156  and the inner surface of pipeline  128 . In one example, packer  100  is designed such that offset  166  is less than or equal to approximately ⅛ inch and offset  168  is greater than ⅛ inch. However, in other examples, offsets  166  and  168  can be larger or smaller depending on the clearance between packer  100  and pipeline  128  necessary to allow packer  100  to be deployed through pipeline  128  and the amount of radial expansion of expansion boots  116  and  118  and brake pads  156  that is provided when actuator  129  moves first and second mandrels  112  and  114  relative to third mandrel  120 . 
     Although particular offset distances are described with reference to example packer  100 , a packer in accordance with this disclosure will be constructed with a desired dimensional relationship with the dimensions of the pipeline in which the device is to be used. In one example configuration, a radial clearance of approximately ⅛ inch will separate the sealing element of the packer and the pipeline inner surface and a radial clearance of approximately ¼ inch will separate the braking element of the packer and the pipeline inner surface. However, as will be apparent to persons skilled in the art, difference radial dimensions may be used for any size pipe, and in some cases such dimensions may be determined by other factors, such as the designed radius of bends the pipeline will experience while being installed on the sea floor, and/or the intended characteristic of the internal welds used to join the pipeline sections. 
     In some cases, it may be desirable to configure packer  100  such that offset  166  between expansion boots  116  and  118  and the inner surface of the pipeline  128  is as small as possible while still allowing packer  100  to be deployed downpipe within pipeline  128 . In the example of  FIG. 3A , the outer peripheries of end caps  104  and  106 , bearings  108  and  110 , and expansion boots  116  and  118  are configured to fit closely with the inner surface of pipeline  128  even when packer  100  is in an unengaged state. In practice, there may be a delay between the occurrence of a wet buckle to pipeline  128  and the resulting detection of the invasion of water caused by the wet buckle (depending in part on the location of a water sensor, if used), and activation of actuator  129  to cause expansion boots  116  and  118  and brake assembly  122  to engage the inner surface of pipeline  128 . During the delay in actuation of packer  100  some water may pass through packer  100 . Reducing offset  166  between expansion boots  116  and  118  and the inner surface of the pipeline  128  will reduce the amount of water that floods pipeline  128  before packer  100  is engaged and the boots substantially seal the pipeline. 
     As is illustrated in  FIG. 3A , end caps  104  and  106 , bearings  108  and  110 , first and second mandrels  112  and  114 , and third mandrel  120  are hollow components. It may be desirable to design the components of packer  100  and other wet buckle packers in accordance with this disclosure as such in order to reduce the weight of the device. Packer  100  may be employed in relatively large pipelines. In one example, pipeline  128  has an inner diameter that is approximately equal to 40 inches. The large size of pipeline  128  necessitates a relatively large packer to seal the inner diameter of the pipeline. As such, in one example, packer  100  may weigh on the order of the thousands of pounds. In such situations, removing as much material from end caps  104  and  106 , bearings  108  and  110 , first and second mandrels  112  and  114 , third mandrel  120 , and other components of packer  100  can have a significant impact on the weight of the device. 
     The overall weight of packer  100  also affects the amount of load on hoist line  113  and, as such, the amount of work required by the hoist machine operating hoist line  113 . As such, reducing the weight of packer  100  can also reduce the cost and complexity of deploying packer  100  via hoist line  113 . 
     The forces encountered by packer  100  in the event of a wet buckle of pipeline  128  may be significant. For example, at a relatively shallow depth of approximately 1500 feet below sea level, the pressures generated by a wet buckle can reach approximately 660 pounds per square inch (psi). At a depth of approximately 12,000 feet, the pressures generated by a wet buckle can reach approximately 5280 psi. In view of the range of forces potentially encountered by wet buckle packer  100 , the wall thicknesses of the components of packer  100  may need to be adjusted to withstand large forces/pressures. 
     It is also noted that the forces encountered by different portions of packer  100  may differ significantly. For example, portions of packer  100  may be partially or substantially pressure balanced because water introduced into pipeline  128  is allowed to enter parts of packer  100 . In such situations, the pressure of the water is balanced on particular portions of packer  100 . For example, water may be allowed to enter portions of packer  100  such that the pressure is balanced on either side of a wall of one or more of end caps  104  and  106 , bearings  108  and  110 , second mandrel  114 , and third mandrel  120 . In one example, most or all of the components of packer  100  except first mandrel  112  will be substantially pressure balanced if seals are provided between clevis  148  and second mandrel  114  and between bearing  108  and second mandrel  114 . In some examples, therefore, packer  100  may be designed to allow pressure balancing of some portions of the device such that the wall thicknesses of different portions of end caps  104  and  106 , bearings  108  and  110 , first and second mandrels  112  and  114 , third mandrel  120 , and other components of packer  100  may differ significantly depending on the amount of pressure/force encountered in the event of a wet buckle. 
     In order to engage packer  100  including radially expanding expansion boots  116  and  118  and setting brake assembly  122 , actuator  129  is configured to generate a range of setting forces. In one example, actuator  129  is configured to generate a setting force approximately equal to 60,000 pounds to substantially seal pipeline  128  with expansion boots  116  and  118  and prevent or inhibit movement of packer  100  with brake assembly  122 . In other examples, actuator  129  is configured to generate a setting force that is less or greater than 60,000 pounds. For example, in a smaller diameter pipe approximately equal to 7 inches, actuator  129  is configured to generate a setting force approximately equal to 12,000 pounds. 
     A variety of materials can be used to fabricate the components of packer  100  including, e.g., metals, plastics, elastomers, and composites. For example, bearings  108  and  110 , first and second mandrels  112  and  114 , and third mandrel  120  can be fabricated from a variety of different types of steel or aluminum. Expansion boots  116  and  118  can be fabricated from a variety of elastomeric materials including rubber. Additionally, end caps  104  and  106  and/or brake pads  156  can be fabricated from a variety of elastomers. In the example of  FIGS. 3A and 3B , end caps  104  and  16  are illustrated as fabricated from an elastomer. In such cases, end cap  104  may need to be structurally reinforced to withstand the pressures caused by the invasion of water into pipeline  128 . As such, packer  100  includes scaffold cone  170 , which is configured to limit the amount end cap  104  can collapse inward in the event of a wet buckle. Scaffold cone  170  can be fabricated from a strong, rigid material such as steel or aluminum. 
     In one example, end caps  104  and  106 , expansion boots  116  and  118 , and/or brake pads  156  are fabricated from a nitrile rubber. At the sea floor, packer  100  may encounter temperatures as low as 32 degrees Fahrenheit (0 degrees Celsius). As such, end caps  104  and  106 , expansion boots  116  and  118 , and/or brake pads  156  may need to be fabricated from elastomers that can withstand relatively low temperatures without significantly affecting the material properties of the components. For example, expansion boots  116  and  118  may need to be fabricated from elastomers that can withstand relatively low temperatures without causing the expansion boots to become too hard, stiff and/or brittle such that the boots are incapable of sufficiently sealing the inner diameter of pipeline  128 . The components of packer  100  can be fabricated using a variety of techniques including, e.g., machining, injection molding, casting, and other appropriate techniques for manufacturing such parts. 
       FIG. 4  depicts another example wet buckle packer  200  in accordance with this disclosure. Packer  200  is substantially similar to packer  100  in function and structure, except with respect to the configuration of the pads of brake  202  of packer  200 . Referring again to  FIG. 2 , packer  100  includes brake assembly  122  including brake pads  156 . Each brake pad  156  associated with each brake arm of brake assembly  122  is larger in the axial direction than in the circumferential direction. In  FIG. 4 , however, packer  200  includes brake  202  including brake pad  204 , which is larger in the circumferential direction than in the axial direction. Additionally, brake pad  204  includes axial grooves  206 . Grooves  206  can have a “V” shaped cross-sectional profile and can function to clear debris accumulated on brake pad  204 , which, in turn, can improve braking performance. 
     In the examples of packer  100  and packer  200 , both pads  156  and pads  204  are single, unitary components. In other examples, however, the packers can include brakes including a number of brake arms, each of which includes a plurality of separate brake pads. For example, each brake arm of the brake can include two, three, or more brake pads. In such cases, providing a small offset between the separate brake pads could also function to clear debris accumulated on the pads to potentially improve braking performance. 
       FIG. 5  is a flowchart depicting an example method of arresting a wet buckle of a submerged pipeline. The method includes deploying a packer apparatus within the pipeline ( 300 ), detecting water ingress into the pipeline ( 302 ), and actuating the packer apparatus in response to the detection of the water ingress into the pipeline ( 304 ). In one example, the packer includes first, second, and third mandrels, a brake, and first and second elastomeric expansion boots. The first and second mandrels are in axial moveable relation with the third mandrel, which is arranged between the first and second mandrels. The brake is arranged between the first and second mandrels. The first elastomeric expansion boot is arranged between a radially extending flange of the first mandrel and a first radially extending flange of the third mandrel. The second elastomeric expansion boot is arranged between a radially extending flange of the second mandrel and a second radially extending flange of the third mandrel. 
     The packer apparatus can be deployed into the pipeline via a hoist line connected to a hoist machine on a pipelay vessel. Detection of water ingress into the pipeline can include sensing water invasion into the inner diameter of the pipeline with a sensor included in or separate from the packer apparatus. In one example, the packer can include a sensor system that detects the invasion of water into the inner diameter of the pipeline. The sensor system communicatively coupled to the packer can provide a signal directly to control electronics included in an actuator of the packer or can transmit signals to a surface system, which, in turn, transmits control signals to the actuator via a supply line. In the event water invasion is detected, the actuator of the packer can trigger actuation of the device. 
     Actuating the packer apparatus can include transmitting signals from the pipelay vessel on the surface to the packer via the supply line connected to the actuator of the packer. The actuator can be configured to move the first mandrel axially toward the third mandrel from a first position to a second position. The actuator can also be configured to move the second mandrel axially toward the third mandrel from a first position to a second position. In one example, the actuator is configured is configured to cause the first and second mandrels to move toward the third mandrel substantially simultaneously. 
     In the second position of the first mandrel, the radially extending flange of the first mandrel is closer to the first radial extending flange of the third mandrel than in the first position, and the first expansion boot is compressed axially between the radially extending flange of the first mandrel and the first radially extending flange of the third mandrel and is expanded radially into engagement with an inner surface of the pipeline. In the second position of the second mandrel, the radially extending flange of the second mandrel is closer to the second radial extending flange of the third mandrel than in the first position, and the second expansion boot is compressed axially between the radially extending flange of the second mandrel and the second radially extending flange of the third mandrel and is expanded radially into engagement with an inner surface of the pipeline. Additionally, in the second position of the first and second mandrels, the brake moves radially outward into engagement with the inner surface of the pipeline. 
     As described above, methods of arresting failures of a submerged pipeline can include deploying multiple packers within the submerged pipeline. In one example, the packers are deployed on either side (e.g. one closer to the surface and one farther from the surface and closer to the sea floor) of the location of the wet buckle (or other failure). In such examples, both packers can be actuated to seal the region of the pipeline between the packers and including the location of the failure. 
     Various examples have been described. These and other examples are within the scope of the following claims.