Patent Publication Number: US-2015063915-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. 
         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  FIGS. 2  in an engaged state within a pipeline. 
         FIG. 4  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 and second mandrels in axially moveable relation to one another, a brake connected to the second mandrel, and an elastomeric expansion boot circumferentially disposed around a portion of the first and second mandrels. The first mandrel is configured to move axially toward the second mandrel from a first position to a second position. In the second position, the first mandrel is configured to cause the expansion boot to be compressed axially between the first and second mandrels and expanded radially into engagement with an inner surface of the pipeline, and to cause the brake to move radially outward to engage 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. 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 packer or the system in which the device is 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  22  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 a manner such 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 , a cap  104 , a first mandrel  106 , an expansion boot  108 , and second mandrel  110 . Packer  100  is coupled to hoist line  112  by hoist ring  102 , which is connected to cap  104 ; and cap  104  is connected to first mandrel  106 . First mandrel  106  is moveably connected to second mandrel  110 . Expansion boot  108  is disposed circumferentially around a portion of first mandrel  106  and second mandrel  110 . 
     Packer  100  is configured to be deployed from a pipelay vessel down a submerged pipeline via hoist line  112 . 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 dropped to the sea floor. First mandrel  106  includes a number of freely rotating wheels  114  distributed around the outer circumference of mandrel  106 . Additionally, second mandrel  110  includes a number of freely rotating wheels  116  distributed around the outer circumference of mandrel  110 . Wheels  114  and  116  facilitate travel of packer  100  through the inner diameter of 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 from being flooded with sea water, which is described in more detail with reference to  FIGS. 3A and 3B . 
     Hoist line  112  extends from hoist ring  102  up to, for example, a hoist machine on a pipelay vessel. In some examples, packer  100  can include hoist rings on both ends of the device to deploy multiple packers within a pipeline in spaced, series relation within the pipeline. Packer  100  is configured to be arranged within the pipeline such that the end including cap  104  faces the region of the pipeline that is at risk of a wet buckle (or other failure). Thus, in the example of  FIG. 1 , one packer could be deployed within suspended pipe span  28  closer to the surface than the likely location of the wet buckle in the sagbend of the “S” curve and another packer could be deployed within pipeline  14  on the other side of the possible wet buckle location, e.g., somewhere along sea floor  26 . 
     In this example, the packer deployed closer to the surface would be arranged within suspended pipe span  28  such that cap  104  faces down toward the likely location of the wet buckle in the sagbend. This upper packer could include a hoist line running from the end of the device including the second mandrel and another line running from the cap to the lower packer. The lower packer closer to sea floor  26  would be arranged within the pipeline such that the cap faces up toward the likely location of the wet buckle in the sagbend and the lower packer would be connected to the upper packer by the line coupled to the caps of each device. 
       FIGS. 3A and 3B  depict section views of wet buckle packer  100  within pipeline  118 . In  FIG. 3A , packer  100  is unengaged with pipeline  118 . In  FIG. 3B , packer  100  is engaged with pipeline  118  to substantially seal the inner diameter of pipeline  118  from water invasion. As illustrated in the section views of  FIGS. 3A and 3B , packer  100  includes actuator  120  and brake assembly  122  in addition to hoist ring  102 , cap  104 , first mandrel  106 , expansion boot  108 , and second mandrel  110 . Actuator  120  and brake assembly  122  are connected to both first mandrel  106  and second mandrel  110 . Supply line  124  is coupled to actuator  120 . 
     Cap  104  and first mandrel  106  can be connected to one another in a variety of ways. In one example, cap  104  and first mandrel  106  are welded to one another. In another example, cap  104  and first mandrel  106  are connected to one another with a threaded connection including threading cap  104  into first mandrel  106  or threading first mandrel  106  into cap  104 . 
     First mandrel  106  is configured to move axially relative to second mandrel  110 . First mandrel  106  includes a number of posts  126  extending from one end of first mandrel  106  toward second mandrel  110 . Posts  126  pass through holes in second mandrel  110 . A ring-shaped plate  128  is connected to the end of posts  126  to connect first mandrel  106  to second mandrel  110 . In this way, first mandrel  106  is able to move axially toward and away from second mandrel  110  as posts  126  pass through the respective holes in second mandrel  110 . Plate  128  limits the axial distance first mandrel  106  can move away from second mandrel  110 . 
     Actuator  120  is depicted schematically in  FIGS. 3A and 3B , but generally includes housing  130  and shaft  132  movably connected to housing  130 . Shaft  132  is configured to slide in and out of housing  130 . Actuator  120  can be a variety of mechanical and electromechanical devices that are configured to be actuated to cause shaft  132  to move axially relative to housing  130 . For example, actuator  120  can include a pneumatically or hydraulically actuated piston that drives shaft  132  with air or a hydraulic fluid supplied by supply line  124 . In another example, actuator  120  includes an electrically activated solenoid that drives shaft  132 . In another example, actuator  120  includes an electromagnetic piston that drives shaft  132  based on controlled electricity transmitted to packer  100  via supply line  124 . In another example, actuator  120  includes an electric motor and screwjack, which can drive shaft  132  using electricity transmitted to packer  100  via supply line  124 . In some cases, actuator  120  can be powered by a power source like a battery deployed with packer  100 . 
     Housing  130  of actuator  120  is arranged within first mandrel  106 . Shaft  132  extends axially from housing  130  through hole  134  in first mandrel  106  and hole  136  in second mandrel  110 . The distal end of shaft  132  is connected to second mandrel  110 . In one example, a nut and two washers are employed to fix the distal end of shaft  132  to second mandrel  110 . However, shaft  132  could also be attached by other mechanisms, e.g., welded to second mandrel  110 . In another example, second mandrel  110  could be fabricated with an integral shaft protruding axially toward first mandrel  106  and housing  130  of actuator  120 . 
     Actuator  120  is configured to cause the distal end of shaft  132  to move axially relative to housing  130 . As the distal end of shaft  132  changes axial position with respect to housing  130 , first mandrel  106  is moved axially with respect to second mandrel  106 . 
     Expansion boot  108  is an annular elastomeric boot that surrounds a portion of first mandrel  106  and second mandrel  110 . First end  138  of expansion boot  108  is coupled to first mandrel  106 . Second end  140  of expansion boot  108  is coupled to second mandrel  110 . In particular, first end  138  is received within slot  142  extending circumferentially and axially in first mandrel  106  and second end  140  is received within slot  144  extending circumferentially and axially in second mandrel  110 . In this manner, expansion boot  108  is sandwiched between first mandrel  106  and second mandrel  110 . 
     As first mandrel  106  moves axially toward second mandrel  110 , expansion boot  108  is compressed axially as slots  142  and  144  move closer to one another. As expansion boot  108  is compressed axially, boot  108  also radially expands into engagement with an inner surface of pipeline  118 . As can be seen in  FIG. 3A  in which packer  100  is unengaged, inner surface  146  of expansion boot  108  is concave with a flattened “V” cross-sectional shape. The shape of inner surface  146  biases expansion boot  108  to move radially outward, instead of inward, when boot  108  is compressed axially between first mandrel  106  and second mandrel  110 . 
     Brake assembly  122  includes a number of brake arms  148 , which are distributed at different angularly disposed, circumferential positions around a longitudinal axis of packer  100 . Brake arms  148  each include a respective link portion  150  and a respective pad  152  at the radially outward end of link  150 . Link  150  is coupled to first mandrel  106  at moving pivot  154  and to second mandrel  110  at fixed pivot  156 . In particular, the radially inward end of link  150  is pivotally connected to clevis  158  at moving pivot  154 . Clevis  158  is connected to plate  128  of first mandrel  106 . Link  150  is pivotally connected to clevis  160  between the radially inward end of the link and pad  152 . Clevis  160  is connected to second mandrel  110 . 
     As first mandrel  106  moves axially toward second mandrel  110 , moving pivot  154  moves axially as the radially inward end of links  150  of brake arms  148  rotate relative to clevises  158 . Axial movement of the radially inward end of links  150  cause the links to rotate about fixed pivot  156  at clevises  160 . As links  150  rotate about fixed pivot  156 , pads  152  move radially outward to engage the inner surface of pipeline  118 , and set brake assembly  122 . Pads  152  are illustrated with a relatively smooth surface finish. However, in other examples, pads  152  can include a texturized or otherwise contoured surface to improve braking performance. For example, pads  152  can include a saw-tooth profile or can be fabricated with a relatively rough surface finish. 
     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  118 , e.g., in the sagbend of the “S” curve formed by the suspended span of pipeline  118  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  118 . In another example, the sensor system can be associated with a separate component and be communicatively coupled to packer  100 . 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  118  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  118 . 
     The sensor system communicatively coupled to packer  100  can provide a signal directly to control electronics included in actuator  120  or can transmit signals to a surface system, which, in turn, transmits control signals to actuator  120  via supply line  124 . In the event water invasion is detected, actuator  120  causes the distal end of shaft  132  to move axially closer to housing  130 . As the distal end of shaft  132  changes axial position with respect to housing  130 , first mandrel  106  is moved axially toward second mandrel  110 , which functions to axially compress and radially expand expansion boot  108 . In the radially expanded state illustrated in  FIG. 3B , expansion boot  108  is configured to substantially seal the inner diameter of pipeline  118  and thereby prevent or inhibit the laid pipeline from being flooded with water. 
     Actuator  120 , in conjunction with radially expanding boot  108 , also deploys brake assembly  122  to prevent or substantially inhibit movement of packer  100  within pipeline  118 . For example, actuator  120  causes the distal end of shaft  132  to move axially closer to housing  130 . As the distal end of shaft  132  changes axial position with respect to housing  130 , first mandrel  106  is moved axially toward second mandrel  110 . Movement of first mandrel  106  relative to second mandrel  110  translate moving pivots  154  axially as the radially inward end of links  150  of brake arms  148  rotate relative to clevises  158 . Axial movement of the radially inward end of links  150  cause the links to rotate about fixed pivots  156  at clevises  160 . As links  150  rotate about fixed pivots  156 , pads  152  move radially outward into engagement with the inner surface of pipeline  118  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 including one or more spring loaded pawls connected to second mandrel  110  and ratchet teeth inscribed in the outer surface of one or more of posts  126  of first mandrel  106 . The ratchet mechanism can be configured to allow first mandrel  106  to move toward second mandrel  110 , while preventing first mandrel  106  from moving axially away from second mandrel  110  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  118 . The offset distance between packer  100  and the inner surface of pipeline  118  may differ at different points along the axial length of packer  100 . For example, offset  162  between expansion boot  108  and the inner surface of the pipeline  118  is different than offset  164  between brake pads  152  and the inner surface of pipeline  118 . In one example, packer  100  is designed such that offset  162  is approximately equal to 1/8 inch and offset  164  is greater than 1/8 inch. However, in other examples, offsets  162  and  164  can be larger or smaller depending on the clearance between packer  100  and pipeline  118  necessary to allow packer  100  to be deployed through pipeline  118  and the amount of radial expansion of expansion boot  108  and brake pads  152  that is provided when actuator  120  moves first mandrel  106  relative to second mandrel  110 . 
     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 1/8 inch will separate the sealing element of the packer and the pipeline inner surface and a radial clearance of approximately 1/4 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 configured packer  100  such that offset  162  between expansion boot  108  and the inner surface of the pipeline  118  is as small as possible while still allowing packer  100  to be deployed downpipe within pipeline  118 . In practice, there may be a delay between the occurrence of a wet buckle to pipeline  118  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  120  to cause expansion boot  108  and brake assembly  122  to engage the inner surface of pipeline  118 . During the delay in actuation of packer  100  some water may pass through packer  100 . Reducing offset  162  between expansion boot  108  and the inner surface of the pipeline  118  will reduce the amount of water that floods pipeline  118  before packer  100  is engaged and expansion boot  108  substantially seals the annulus of the pipeline. 
     As is illustrated in  FIG. 3A , cap  104 , first mandrel  106 , and second mandrel  110  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  118  has an inner diameter that is approximately equal to  40  inches. The large size of pipeline  118  necessitates a relatively large packer to seal the annulus of the pipeline. As such, in one example, packer  100  may weigh on the order of approximately 10,000 pounds. In such situations, removing as much material from cap  104 , first mandrel  106 , second mandrel  110 , 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  112  and, as such, the amount of work required by the hoist machine operating hoist line  112 . As such, reducing the weight of packer  100  can also reduce the cost and complexity of deploying packer  100  via hoist line  112 . 
     The forces encountered by packer  100  in the event of a wet buckle of pipeline  118  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  118  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 water pressure is balanced on either side of a wall of one or more of cap  104 , first mandrel  106 , and second mandrel  110 . In one example, pressure balancing of packer  100  could include providing flow port holes in cap  104  and/or first mandrel  106 , in which case it may be necessary to seal hole  134 . 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 cap  104 , first mandrel  106 , second mandrel  110 , 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 boot  108  and setting brake assembly  122 , actuator  120  is configured to generate a range of setting forces. In one example, actuator  120  is configured to generate a setting force approximately equal to 60,000 pounds to substantially seal pipeline  118  with expansion boot  108  and prevent or inhibit movement of packer  100  with brake assembly  122 . In other examples, actuator  120  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  120  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, cap  104 , first mandrel  106 , expansion boot  108 , and second mandrel  110  can be fabricated from a variety of different types of steel or aluminum. Expansion boot  108  can be fabricated from a variety of elastomeric materials including rubber. In one example, expansion boot  108  is 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, expansion boot  108  may need to be fabricated from elastomers that can withstand relatively low temperatures without significantly affecting the material properties of boot  108 . For example, expansion boot  108  may need to be fabricated from elastomers that can withstand relatively low temperatures without causing boot  108  to become too hard, stiff and/or brittle such that boot  108  is incapable of sufficiently sealing the annulus of pipeline  118 . 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  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 ( 200 ), detecting water ingress into the pipeline ( 202 ), and actuating the packer apparatus in response to the detection of the water ingress into the pipeline ( 204 ). In one example, the packer includes first and second mandrels in axially moveable relation to one another, a brake connected to the second mandrel, and an elastomeric expansion boot circumferentially disposed around a portion of the first and second mandrels. 
     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 annulus 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 annulus 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 second mandrel from a first position to a second position. In the second position, the first mandrel causes the expansion boot to be compressed axially between the first and second mandrels and expanded radially into engagement with an inner surface of the pipeline and the first mandrel causes the brake to move radially outward to engage 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.