Abstract:
A system and method for the installation and removal of monitoring equipment is disclosed. In some embodiments, the monitoring equipment may be installed or removed using a remotely operated vehicle. In certain implementations, the monitoring system includes a sensor assembly connectable to a tubular member, an alignment tool for installing or removing the sensor assembly to and from the tubular member, and an alignment cage for facilitating access of the alignment tool to the sensor assembly. In some embodiments, the alignment tool may be aligned with the sensor assembly for installation or removal as a result of the alignment tool being inserted through the alignment cage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/416,711, filed Nov. 23, 2010, titled “REMOTELY ACCESSIBLE SUBSEA STRAIN SENSOR ASSEMBLY,” the entirety of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present developments relate to the repair and/or replacement of monitoring equipment, for example, equipment for monitoring the strain on a section of underwater pipe. 
     2. Description of the Related Art 
     Gas and oil drilling is performed in many different ways, on land and at sea. In marine drilling operations, large sections of steel pipe (which are typically referred to as “risers” or “flowlines”) are connected to stretch deep into the ocean and along the seabed. The length of this piping required to reach the sea floor, motion of the platform, station, rig, or vessel the piping stretches from, ocean currents, self-weight of the piping, buoyancy, the pressure extremes, and the temperature extremes to which such piping is subjected to often result in undesirable strain, tension, and/or bending in the pipe. 
     The resulting bending and tension induce strains in the pipe. Unanticipated failure of such pipes can result in severe pollution and heavy economic loss. Thus, in some cases, sensors, sensor assemblies, or systems for monitoring strain in submerged pipes are coupled to the pipe in order to enable a continuous assessment of the integrity of the pipe. When a sensor needs repair or replacement, it is often desirable to remove or replace the sensor in place at or near the seabed. However, in some cases due to the extreme pressures and prohibitive costs, sending human divers to conduct the repair or replacement is not efficient or even possible. In such cases, a submarine robot, such as a remotely operated vehicle (ROV), may be required to reach the sensor assembly. However, heretofore due to, e.g., complexity in the mounting system of the sensor assembly and/or difficulty in maintaining the position of the ROV relative to the sensor, such removal, replacement, and/or repair has had little success. Accordingly, previous sensor systems have largely been non-serviceable and have relied on redundant sensors to increase the chance of continued operation in the event of a sensor failure. Such redundant sensor systems, however, can be larger in size, require additional time to install and test, and be more costly. Further, such systems yet may not provide continued operation in the event of multiple sensor failures. 
     SUMMARY 
     An aspect of at least one of the embodiments disclosed herein is the realization that a monitoring system for a tubular member can be configured to have a first mounting point and a second mounting point disposed at fixed locations on the tubular member. The monitoring system can further include a sensor assembly having a first end configured to couple and decouple to the first mounting point and a second end configured to couple and decouple to the second mounting point. Some embodiments provide an alignment tool that is connectable to the sensor assembly and configured to mate with the first and second ends of the sensor assembly to facilitate the coupling and decoupling of the first end with the first mounting point and the second end with the second mounting point. The monitoring system can further include an alignment cage configured to guide the alignment tool into a mating configuration with the first and second ends of the sensor assembly. 
     In some embodiments, a monitoring system for an underwater tubular member includes a sensor assembly that is configured to measure strain on the tubular member. The sensor assembly can include a first end configured to couple and decouple with a first mounting point of the tubular member and a second end configured to couple and decouple with a second mounting point of the tubular member. The system can also include an alignment cage coupled with the tubular member. Further, some implementations of the system include an alignment tool. Some embodiments of the alignment tool are configured to be manipulated by a remotely operated vehicle. Some implementations of the alignment tool are configured to be received in the alignment cage. Some embodiments of the alignment tool are configured to couple with the sensor assembly. In certain implementations, the alignment tool has a first opening and a second opening. The first opening can be configured to receive the first end of the sensor assembly and the second opening can be configured to receive the second end of the sensor assembly. 
     In certain embodiments, when the alignment tool is received in the alignment cage, the first opening of the alignment tool, the first end of the sensor assembly, and the first mounting point of the tubular member are substantially aligned and the second opening of the alignment tool, the second end of the sensor assembly, and the second mounting point of the tubular member are substantially aligned. Such a configuration can, for example, facilitate coupling and decoupling of the first end of the sensor assembly with the first mounting point of the tubular member and coupling and decoupling of the second end of the sensor assembly with the second mounting point of the tubular member. 
     In some embodiments, the alignment tool includes a channel and the alignment cage includes a rib. The channel can be configured to receive the rib, thereby guiding the alignment tool into the alignment cage. In certain implementations, the channel further includes a first positioning feature and the rib further includes a second positioning feature. The first positioning feature and the second positioning feature can be configured to inhibit removal of the alignment tool from the alignment cage. 
     In certain implementations, the sensor assembly further includes a notch. In some such variants, at least the first opening of the alignment tool includes a latch element. The latch element can be movable between an extended position and a retracted position. In certain arrangements, the latch can be moved from the retracted position to the extended position, and be received in the notch, when the alignment cage is received in the alignment tool. In certain instances, the alignment tool further includes a lever configured to move the latch element between the extended and retracted positions. 
     In some embodiments, the first mounting point also includes an alignment post mounted to the tubular member. Further, the first end of the sensor assembly can include a mounting block configured to engage the alignment post. In some implementations, the alignment post also has a base, conduit, and spool. The spool can be configured to receive the conduit. The mounting block can be configured to receive the spool. 
     In certain embodiments, the first and second ends of the sensor assembly and the first and second mounting points include corresponding positioning features configured to facilitate alignment of the sensor assembly and the first and second mounting points. In certain implementations, at least the first end of the sensor assembly further has a fastener. The fastener can be configured to couple the first end with first mounting point. In some embodiments, the alignment tool includes an upper section and a lower section with a middle section therebetween. In some configurations, the middle section is narrower than the upper and lower sections. In certain implementations, the alignment tool further comprises a handle for positioning the alignment tool. In some variants, monitoring system also includes the remotely operated vehicle. 
     In some embodiments, a method of remotely removing a monitoring system from a tubular member includes engaging an alignment tool and an alignment cage with a remotely operated vehicle. The method can also include inserting a portion of the sensor assembly in an opening of the alignment tool. The sensor assembly can have a fastener that secures the sensor assembly with an alignment post of the tubular member. The method can further include coupling the alignment tool and the sensor assembly. Additionally, the method can include loosening the fastener. Also, the method can include removing the alignment tool and the sensor assembly as a unit (e.g., a single assembly) from the alignment cage and the alignment post with the remotely operated vehicle. For example, in certain embodiments, the ROV moves the alignment tool and the sensor assembly radially (in relation to the tubular member), thereby moving the alignment tool and the sensor assembly out of and away from the alignment cage and the alignment post. 
     In certain implementations, the method removing a monitoring system from a tubular member also includes holding the alignment tool in the alignment cage with a first positioning feature on the alignment tool and a second positioning feature on the alignment cage. The first positioning feature and the second positioning feature can be configured to releasably mate. In some embodiments, the method further includes turning a lever. The lever can be coupled with a latch element on the alignment tool. In some embodiments, the method further includes moving the latch element from a retracted position to an extended position. Moreover, the method can include receiving the latch element in a slot in the sensor assembly. In certain variants, the method also includes inserting a wrench into a head portion of the fastener and turning the wrench. 
     In some embodiments, a method of remotely installing a monitoring system with a tubular member includes engaging an alignment tool and an alignment cage with a remotely operated vehicle. The alignment tool can be coupled with a sensor assembly. In some implementations, the method also includes mating a portion of the sensor assembly with an alignment post coupled with the tubular member. The method can also include securing the sensor assembly with the alignment post. Further, the method can include decoupling the alignment tool and the sensor assembly. Some variants of the method also include disengaging the alignment tool from the alignment cage. Moreover, the method can include separating the alignment tool from the alignment cage and the sensor assembly. In certain such instances, the sensor assembly remains connected with the alignment post. 
     In some embodiments, the method also includes holding the alignment tool in the alignment cage with a first positioning feature on the alignment tool and a second positioning feature on the alignment cage. The first positioning feature and the second positioning feature can be configured to releasably mate. In certain implementations, the method further includes inserting a wrench into a head portion of a fastener of the sensor assembly and turning the wrench. The method can additionally include turning a lever. The lever can be coupled, for example, with a latch element on the alignment tool. Some embodiments of the method include moving the latch element from an extended position to a retracted position. Moreover, some implementations of the method include removing the latch element from a slot in the sensor assembly. 
     In accordance with certain implementations, a system for mounting a sensor on an underwater tubular member having at least one sensor mounting location thereon includes an alignment cage having a guide section. The alignment cage can be configured to couple with the tubular member. The system can further include an alignment tool, which can be configured to be manipulated by a remotely operated vehicle. Certain embodiments of the alignment tool have at least one opening and a guide channel. In some implementations, the alignment tool is configured to be received in the alignment cage such that the guide channel of the alignment tool and the guide section of the alignment cage slidably engage. In certain such arrangements, the alignment tool is thereby substantially aligned along a longitudinal axis of the tubular member. In some embodiments, when the alignment tool is received in the alignment cage, the at least one opening in the alignment tool is substantially coaxial with the at least one sensor mounting location of the tubular member. For example, a fastener passed through the at least one opening can be received in an aperture in the at least one sensor mounting location. 
     In certain implementations, the system further includes a sensor assembly. The sensor assembly can be configured to couple with the at least one mounting location of the tubular member. In some embodiments, the alignment tool is configured to releasably connect with a sensor assembly. In certain embodiments, the guide section also has a rib and the guide channel is configured to receive the rib. In some instances, the alignment tool has a figure-eight shape (e.g., a wider upper and lower section and a narrower middle section). In certain embodiments, the guide section and the guide channel are configured to be releasably connected with a detent (e.g., a spring detent). In some such cases, the detent is configured to inhibit or prevent the alignment tool from separating from the alignment cage. For example, the detent can be configured to retain the alignment tool in the alignment cage until the alignment tool is pulled from the alignment cage by the remotely operated vehicle. In some cases, the detent includes a spring-loaded projection on the alignment tool and a corresponding recess in the alignment cage (e.g., in the guide section). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  illustrate isometric, top, front, and bottom views, respectively, of an embodiment of a sensor assembly. 
         FIG. 2  illustrates an isometric view of an embodiment of a mount block. 
         FIG. 3  illustrates an isometric view of an embodiment of an alignment post. 
         FIG. 4  illustrates a longitudinal cross-sectional view of the sensor assembly of  FIG. 1  installed with the alignment post of  FIG. 3  and an embodiment of a spool, wherein the fastener is in the “full out” position. 
         FIG. 5  illustrates a longitudinal cross-sectional view of the sensor assembly of  FIG. 1  installed with the alignment post of  FIG. 3  and an embodiment of a spool, wherein the fastener is in the “full in” position. 
         FIGS. 6A-6B  illustrate front and back isometric views of an embodiment of an alignment tool. 
         FIG. 7  illustrates a partial longitudinal cross-sectional view of the alignment tool of  FIGS. 6A-6B  installed with the sensor assembly of  FIG. 1 . 
         FIGS. 8A-8B  illustrate an embodiment of a wrench. 
         FIG. 9  illustrates an isometric view of an embodiment of a tubular member coupled with the sensor assembly of  FIG. 1 , an embodiment of an alignment cage, and an embodiment of a protection cage, and also illustrates the alignment tool of  FIGS. 6A-6B  in a disengaged position. 
         FIG. 9A  illustrates an axial cross-sectional view of the tubular member of  FIG. 9  wherein the tubular member is coupled with multiple sensor assemblies, alignment cages, and protection cages. 
         FIG. 9B  illustrates a perspective view of the tubular member of  FIG. 9A  and including protective doors. 
         FIG. 10  illustrates an isometric view of an embodiment of the sensor assembly of  FIG. 1  installed on a tubular member, with the alignment tool of  FIGS. 6A-6B  in an engaged position. 
         FIG. 11  illustrates an embodiment of a method of removing a sensor. 
         FIG. 12  illustrates an embodiment of a method of installing a sensor. 
         FIG. 13  illustrates a chart of three non-limiting embodiments of empirical strain testing values. 
         FIG. 14  illustrates a graphical representation of an embodiment of a strain plane in a portion of a tubular member. 
     
    
    
     DETAILED DESCRIPTION 
     A variety of examples of subsea strain sensor assemblies, protection, fastening, and alignment devices, as well as systems and methods thereof, are described below to illustrate various examples that may be employed to achieve the desired improvements, such as but not limited to improvements in the remote positioning of subsea sensors with a high degree of precision and accuracy. These examples are only illustrative and not intended in any way to restrict the inventions presented and the various aspects and features of these inventions. For example, although embodiments and examples are provided herein in the marine field, the inventions are not confined exclusively to the marine field and can be used in other fields. Furthermore, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. No feature, structure, or step disclosed herein is essential or indispensible. 
     As will be discussed in further detail below, in some embodiments, a subsea strain sensor assembly  5  includes a sensor assembly  10 , an alignment tool  110 , and an alignment cage  210 . In some embodiments, the sensor assembly  10  can be coupled with a tubular member  202  (e.g., a portion of an undersea pipeline) either directly or indirectly. In certain implementations, the alignment cage  210  couples with the tubular member  202 . For example, the alignment cage  210  can partially surround and/or protect the sensor assembly  10 . In some embodiments, the alignment cage  210  is configured to receive and/or couple with the alignment tool  110 . In certain such instances, the alignment tool  110  is configured to the receive sensor assembly  10 . In some arrangements, some or all of the sensor assembly  10  can be decoupled from the tubular member  202 , thereby allowing the sensor assembly  10  to be removed from the tubular member  202 . 
     With regard to  FIGS. 1A-1D , an embodiment of the sensor assembly  10  is illustrated. The illustrated embodiment includes a first mount block  12  coupled to an elongate spacer bar  14 . In some arrangements, the spacer bar  14  includes a radially expanded section  16 . The spacer bar  14  can be connected to an armature  17 , which in turn can be interfaced with a sensor body  18  having a sensor  19 , such as a displacement sensor, configured to measure displacement of the armature  17  relative to the sensor body  18 . In some embodiments, the armature  17 , sensor body  18 , and sensor  19  are configured to form a linear variable differential transformer (LVDT). In some embodiments, a flexible bellows  20  protects the armature  17  and/or the sensor body  18 . The bellows  20  can be filled with oil, for example, to facilitate pressure-balancing. The sensor body  18  can also be coupled to a second mount block  22 . In some cases, one or more of the mount blocks  12 ,  22  include one or more ports  30 . As illustrated, the first mount block  12  and the second mount block  22  need not be the same size or shape. Generally, the components of the sensor assembly  10  are constructed of long life corrosion resistant materials, such as but not limited to Monel 400, Monel 500, Inconel 625, Super Duplex Steels, stainless steel, aluminum, or otherwise. 
     In some embodiments, the first mount block  12  is rigidly connected to a first location of a tubular member (not shown) and the second mount block  22  is rigidly mounted to a second location of the tubular member, e.g., on opposing sides of a weld in the tubular member. As discussed above, the first mount block  12  connects to one end of the armature  17  (via the spacer bar  14 ); the second mount block  22  connects to the sensor body  18 , which in turn interfaces with a second end of the armature  17 . Thus, by measuring the displacement of the armature  17  relative to the sensor body  18 , the sensor  19  can measure the relative displacement of the mount blocks  12 ,  22  and/or the relative displacement of the first and second locations of the tubular member. Such relative displacements can be used to determine, for example, strain in the tubular member. In some instances, the strain that is measured, read, or determined is at least partly non-linear and can include other factors, such as uncertainty, hysteresis, and repeatability. For example,  FIG. 13  shows three trials illustrating deviation from linear fit as a function of applied strain. 
     In certain embodiments, one or more of the mount blocks  12 ,  22  can be coupled to a vertically extending member  24 , also called a “top hat.” Each vertically extending member  24  can include a cylindrical portion  23  connected to a radially inwardly-extending shoulder  27 , which in turn connects to an axial passage  25  (not shown) that is configured to receive a fastener  26  (only the top of the fastener is shown), such as a screw. As illustrated, one or more of the vertically extending members  24  can include a notch  28 . 
     Turning to  FIG. 2 , an embodiment of the first mount block  12  is illustrated. Generally, the second mount block  22  can include similar or the same features and aspects as the first mount block  12 . As shown in  FIG. 2 , the first mount block  12  is rectangular, but it can be most any other shape. As shown, one or more surfaces of the first mount block  12  can include a recessed portion  36 , which in turn can include a wall portion  37  and a radially-inwardly extending first positioning face  38 . An aperture  34  through the first mount block  12  can connect with the recessed portion  36 . As shown, the aperture  34  and recessed portion  36  are each about circular in cross-section, though many other shapes are possible. 
     In some embodiments, the first positioning face  38  includes one or more first locating features  39 , e.g., grooves or recesses of various shapes and sizes, for receiving one or more positioning elements  40  of various shapes and sizes (e.g., press-fit, slip-fit, snap-fit, detent, threads, or the like). For instance, the embodiment shown includes three cylindrically-shaped first locating features  39  configured to receive three substantially spherical or hemispherical positioning elements  40 . The first locating features  39  can be the same shape or different shapes. Likewise, the positioning elements can be the same shape or different shapes to correspond or align with the shapes of the first locating features  39 . As shown, the first locating features  39  and positioning elements  40  are positioned about equidistant from each other in a circumferential axis about the aperture  34  and about radially equidistant from a longitudinal axis of the aperture  34 , though many alternate arrangements of the first locating features and elements  39 ,  40  are possible. One or more surfaces of the first mount block  12  can also include one or more fastening features  42  for, e.g., coupling to other components of the sensor assembly. The fastening features  42  can be of different sizes and shapes. For instance, the illustrated embodiment includes five fastening features: four small fastening features spaced around a large central fastening feature. 
     An embodiment of a portion of an alignment post  44  is illustrated in  FIG. 3 . Typically, the alignment post  44  is joined with the tubular member in specific locations on the tubular member. For example, the alignment post  44  can be joined with the tubular member with extension portions that project radially outward from the tubular member (see, e.g.,  FIG. 9 ). In other instances, the alignment is post  44  is radially adjacent, or flush with, the outer surface of the tubular member (see, e.g.,  FIG. 9B ). 
     As shown in  FIG. 3 , the alignment post  44  can include a base  46  with a tubular section  48  extending therefrom. The base  46  can be sized and shaped to mate with the recessed portion  36  of the mount block  12  and the tubular section can be sized and shaped to be received by the aperture  34 . Generally, to facilitate mating and positioning, the tubular section  48  is tapered and the bottom edge of the aperture  34  is correspondingly tapered. A conduit  52  can extend through at least some of the tubular section  48 . In certain embodiments, the conduit  52  is threaded. In some arrangements, the tubular section  48  includes one or more slots  54  (e.g., holes, recesses, notches, grooves, or cut-out areas), as will be discussed in further detail below. The base  46  can include a second positioning face  51 , which can have one or more second locating features  50  of various shapes and/or sizes. The second locating features  50  can be the same shape or can be of different shapes. For example, the embodiment illustrated includes second locating features  50  that are a cylindrical recess, a conical recess, and an elongated valley. 
     Generally, the second locating features  50  are positioned in a manner similar to the first locating features  39  of the first mount block  12 . In some embodiments, when the alignment post  44  and the first mount block  12  are mated, the first positioning element  40  and the second locating feature  50  (and/or the first and second locating features  39 ,  50 ) are aligned. Thus, in certain such embodiments, the first positioning element  40  can be received in the second locating feature  50 . 
     In some implementations, the alignment post  44  is installed at a predetermined point on a tubular member prior to the tubular member being submerged. Thus, as will be discussed in further detail below, the alignment post  44  can facilitate locating the sensor assembly  10  (via the mount blocks  12 ,  22 ) at the predetermined points on the tubular member, even when the tubular member is positioned at or near the sea floor. Many ways can be employed to connect the alignment post  44  to the tubular member, including, without limitation, welding, fasteners, glue, epoxy, clamps, straps, or the like. In some embodiments, the alignment post  44  connects to insulation on the tubular member, such as is disclosed in U.S. Patent Application Publication No. 2008/0303382, the entirety of which is incorporated by reference herein. Further, some embodiments of the alignment post  44  include an extension member to distance the alignment post  44  from the surface of the tubular member. 
     With regard to  FIG. 4 , a cross-section of an embodiment of the sensor assembly  10  with the fastener  26  in the “full out” position is depicted. The alignment post  44  is received by a spool  56 , which in turn is received by the first mount block  12 . In some embodiments, the alignment post  44  is received by the first or second mount  12 ,  22  without a spool  56 . As shown, the spool  56  can include slot, recesses, gaps, apertures or holes  32  that are positioned to correspond to the slots  54  in the alignment post  44 . In some cases, set screws are used to connect the spool  56  and the alignment post  44  via the holes  32  and slots  54 . In some embodiments, the alignment post  44  and/or the spool  56  are tapered to facilitate precise alignment with one of the mount blocks  12 ,  22 . 
     In certain implementations, the first and second mount blocks  12 ,  22  each are configured to couple with of the alignment posts  44 . For example, the first positioning face  38  of the first mount block  12  can abut or otherwise engage with the second positioning face  51  of the base  46  of the alignment post  44 . In the embodiment shown, the positioning element  40  is located between the first and second locating features  39 ,  50 . In some embodiments, when the mount block  12  and the base  46  are engaged, the alignment post  44  is configured to engage the fastener  26 . For example, the conduit  52  of the alignment post  44  can be configured to be coaxial with, or about coaxial with, the axial passage  25  of the vertically extending member  24 . 
     In some embodiments, the fastener  26  includes a proximal end  58 , a threaded portion  59 , and a distal end  60 . The proximal end  58  generally includes a radially-outwardly extending head portion  62 . Most any type of configuration for the head portion  62  can be employed, such as slotted, Phillips, square, Torx, hex, or the like. In some embodiments, the head portion  62  includes a socket-head with six, eight, ten, or more lobes. The fastener  26  can include a flare or cone configured to facilitate guiding an implement into the head portion  62 . The fastener  26  can include indicia  64 , such as a reduced-diameter section or indelible marking, spaced along the fastener  26  such that the indicia  64  is visible between the head portion  62  and the inwardly-extending shoulder  27  when the fastener  26  is not received by the alignment post  44 . In some embodiments, the fastener  26  includes a radially-outwardly extending flange  66 . A retaining ring  68  can be connected to the fastener  26  and abut the flange  66 . In other cases, the fastener  26  includes a groove, slot, or recess (not shown) configured to receive the retaining ring  68 . As shown in  FIG. 4 , in some embodiments, a biasing member  70  (e.g., a spring or belleville washer) generally biases the fastener  26  away from the inwardly-extending shoulder  27 , which can facilitate threading the fastener  26  into the alignment post  44 . As shown, the fastener  26 , biasing member  70 , retaining ring  68 , and flange  66  are at least partly contained within an axial chamber  72  of the vertically extending member  24 . 
     With regard to  FIG. 5 , a cross-section of an embodiment of the sensor assembly with the fastener  26  in the “full in” position is depicted. In this position at least a portion of the threaded portion  59  of the fastener  26  is received in the alignment post  44 . As shown, the head portion  62  is in contact or about in contact with the inwardly-extending shoulder  27  of the vertically extending member  24 , the biasing member  70  has been extended, and the flange  66  and the retaining ring  68  are in contact or about in contact with an upper end of the alignment post  44  and/or the spool  56 . 
     Turning now to  FIGS. 6A-6B , illustrated is an embodiment of the alignment tool  110 . The alignment tool  110  includes a deck  111  connecting a first wall  113  and a second wall  115 . As shown, in some embodiments, in plan view the alignment tool  110  is about hourglass in shape: having wider upper and lower sections  112 ,  114  and a narrower guide channel  116  therebetween. The alignment tool  110  can be of various shapes and sizes such as angular, rectangular, square, or round Likewise, the walls  113 ,  115  and the deck  111  can be of various sizes and shapes. Low friction pads  117  can be connected to at least a portion of some of the walls  113 ,  115  and/or the guide channel  116 . 
     Some embodiments of the alignment tool  110  include a first positioning feature  118 . The first positioning feature  118  can be located in the guide channel  116 . For example, some embodiments include a spring within a hollow tube  135  disposed between the sides  113 ,  115 , the spring biasing hemispherical detents projecting into the first positioning feature  118 . The first positioning feature  118  can be of various shapes, such as ball, sphere, cylindrical, or wedge-shaped. The first positioning feature  118  can include a feature, such as a visual or an electrical signal, to indicate that the first positioning feature  118  has been engaged. 
     Certain implementations of the alignment tool  110  include a handle  120  to facilitate, e.g., manipulation, alignment, positioning, installation and/or placement of the alignment tool  110 . As shown, the handle  120  is positioned generally centered on the alignment tool  110 . In other embodiments, the handle  120  is positioned in alternate locations on the alignment tool  110 . The upper and/or lower sections  112 ,  114  can include openings  119 ,  121  configured to receive the vertically extending member  24  of each respective mounting block  12 ,  22  of the sensor assembly  10 . In some embodiments, one or both of the openings  119 ,  121  include one or more latch elements  122 , as will be discussed in further detail below. In certain arrangements, the alignment tool  110  includes one or more grips  123  to facilitate, for example, transporting the alignment tool  100  and/or tethering the alignment tool to a desired location. 
     With regard to  FIG. 7 , an example of the engagement between the sensor assembly  10  and the alignment tool  110  is illustrated. In some embodiments, a lever  124  connects to the deck  111  and/or one or more of the walls  113 ,  115  by a mount  126 . The lever  124  can pass through a gap  130 , aperture, recess, opening or the like in the deck  111 . In certain embodiments, the lever  124  is coupled with a cam  132  by, e.g., a screw, snap ring, or the like. The cam  132  can contact one or more tappets  134 , which in turn are connected to a translation member  136 . The translation member  136  can extend a portion of the distance between the openings  119 ,  121 . In certain embodiments, the translation member  136  connects to one or more of the latch elements  122 , e.g., the ends of the translation member  136  each connect to one of the latch elements  122 . As shown, when the sensor assembly  10  and alignment tool  110  are engaged (e.g., assembled, mated, mounted, installed or the like), the notch  28  of the vertically extending member  24  can be axially aligned, substantially axially aligned, or about axially aligned with the latch element  122 . 
     In certain embodiments, when the sensor assembly  10  and alignment tool  110  are engaged, a locked position of the alignment tool  110  and sensor assembly  10  can be achieved by rotating the lever  124  (e.g., about 90° clockwise). Such movement of the lever  124  can in turn rotate the cam  132  by a similar amount. The rotational movement of the cam  132  can be transformed to linear movement of the tappets  134 , as well as linear movement of the translation member  136 . Such movement of the translation member thereby encourages the one or more latch elements  122  toward the openings  119 ,  121 . Indeed, as discussed above, when the sensor assembly  10  and alignment tool  110  are engaged, the latch elements  122  and the notch  28  are aligned. Thus, rotation of the cam  132  can move the one or more latch elements  122  into an extended position, e.g., into the notch  28 . In some embodiments, the latch element  122  and/or the notch  28  is radiused, beveled, or the like, to facilitate guiding the latch element  122  into the notch  28 . As illustrated, in a mode in which the openings  119 ,  121  receive the vertically extending member  24  of the sensor assembly  10 , the extended position of the latch element  122  can place the latch element  122  in engagement with the notch  28  and thereby secure, lock, or hold together the sensor assembly  10  with the alignment tool  110 . 
     With continued reference to the embodiment of  FIG. 7 , the alignment tool  110  can be placed in an unlocked or retracted position by rotating the lever  124  in the opposite direction from that used to achieve the locked or extended position (e.g., about 90° clockwise). Such rotation rotates the cam  132  by a similar amount, thereby translating the tappets  134  and translation member  136  and moving the latch element  122  to a retracted position, in which the latch element  122  is disengaged from the notch  28 . Generally, the one or more latch elements  122  are biased to return to the retracted position. In some such embodiments, the disengagement of the latch element  122  from the notch  28  facilitates the disengagement or removal of the mounting alignment tool  110  from the sensor assembly  10  by de-mating the alignment tool  110  from the sensor assembly  10 . 
     Turning to  FIGS. 8A-8B , an embodiment of a wrench  140  can include a handle section  142 , an elongate section  144 , and a head section  146 . The wrench  140  can be configured to be coupled to the head portion  62  of the fastener  26 . Accordingly, the head section  146  can be configured to be matingly-received by the head portion  62 . As shown, the head section  146  can be a hexagonally-faceted generally spherical element, which can allow insertion of the wrench into the head portion  62  at multiple angles. The wrench  140  can include an aperture, hook, or the like configured to receive a tether (such as a lanyard) that can be coupled to the sensor assembly  10 , ROV, tubular member or alignment tool  110  to inhibit the wrench  140  from falling to the sea floor should the wrench  140  be dropped. In some embodiments, the wrench  140  is stored within a storage feature (not shown) on the alignment tool  110 . For example, the alignment tool  110  can include a hook, clamp, basket, magnet or the like, for storage of the wrench  140 . 
     With reference to  FIG. 9 , an embodiment of the subsea strain sensor assembly  5  in a pre-assembled state on a tubular member  202  is illustrated. As shown, the subsea strain sensor assembly  5  can connect to a tubular member  202 . In certain embodiments, the subsea strain sensor assembly  5  includes the sensor assembly  10 , alignment tool  110 , and the alignment cage  210 . In some arrangements, the subsea strain sensor assembly  5  also includes a protection cage  230 . 
     In some instances, one or more alignment posts  44  couple the sensor assembly  10  with the tubular member prior  202 . For example, the alignment posts  44  can be installed on (e.g., via welding or bonding technique) the tubular member  202  prior to the tubular member being submerged. As discussed above, the alignment posts  44  can also be installed on an insulation member on the tubular member or include an extension member that is installed on the tubular member. 
     In certain implementations, the protection cage  230  and alignment cage  210  connect to the outside of the tubular member  202 , such as by a bracket  212 . In some arrangements, the protection cage  230  and alignment cage  210  connect to a common bracket  212 . In other arrangements, the protection cage  230  and alignment cage  210  connect to different brackets (see  FIG. 9B ). In some implementations, the bracket  212  is configured to connect to the outside of the tubular member  202  with sufficient force to inhibit the protection cage  230  and the alignment cage  210  from moving relative to the tubular member  202  when the tubular member  202  is in an upright position. Various methods can be used to connect the bracket  212  to the tubular member, such as by welding, clamps, flanges, fasteners, press-fit, or the like. The bracket  212  can include a cut-out portion (see  FIG. 9B ) configured to mate to a boss (not shown) on the tubular member, thus inhibiting the bracket  212 , protection cage  230  and/or alignment cage  210  from rotating relative to the tubular member  202 . Thus, the position of the bracket  212 , protection cage  230 , and alignment cage  210  relative to the tubular member  202  can be maintained, even in instances in which a force is applied to the protection cage  230  and/or alignment cage  210 , such as can occur during ROV operations in the vicinity of the subsea strain sensor assembly  5 . 
     In some embodiments, the protection cage  230  and/or alignment cage  210  are rigidly connected to the tubular member  202  at only one end. Among other advantages, such a configuration can avoid transferring tubular member loads (e.g., bending and/or tension) through the protection cage  230  or alignment cage  210 . For example, in the embodiment shown, the bracket at the upper end of the alignment cage  210  is rigidly connected to the tubular member  202  and the bracket at the lower end of the alignment cage  210  is non-rigidly connected to the tubular member  202 . In some arrangements, the transfer of tubular member loads to the alignment and/or protection cage(s)  210 ,  230  is inhibited by an isolator (e.g., a material with a low Modulus of Elasticity) disposed at the interface of the tubular member  202  with the alignment and/or protection cage  210 ,  230 . For example, in some embodiments, both ends of the protection cage  230  and/or alignment cage  210  are clamped to the tubular member  202  with a bracket having a rubber surface, so that load in the tubular member deforms the rubber rather than being transferred to the cage(s). 
     As shown, the alignment cage  210  includes first and second alignment cage arms  214 ,  216 , which can be disposed at an angle α with respect to each other around the longitudinal axis L of the tubular member  202 . As shown, angle α is about 90°, though most any angle is possible. Generally, the first and second alignment cage arms  214 ,  216  are about equally spaced from the sensor assembly  10  mounted to the tubular member  202 . 
     As illustrated, one or more of the first and second alignment cage arms  214 ,  216  can include an alignment guide section  218 , which can include an alignment rib  220 . The alignment rib  220  can be disposed generally parallel to the longitudinal axis S of the vertically extending members  24  of the sensor assembly  10 . The alignment rib  220  can include low friction pads or coatings to facilitate assembly, mounting, or installation of the alignment tool  110  with the alignment cage  210  and/or sensor assembly  10 , as discussed below. In some embodiments, the alignment rib  220  includes a second positioning feature  222 , e.g., a recess, to mate with the first positioning feature  118  of the alignment tool  110 . The alignment guide section  218  is disposed along the axis L so as to receive the guide channel  116  of the alignment tool  110 . The alignment guide section  218  is generally equally spaced between the first and second mount blocks  12 ,  22  of the sensor assembly  10 . In some embodiments, by virtue of the alignment guide section  218  being received in the guide channel  116 , results in the extending members  24  of the sensor assembly  10  being automatically aligned with the respective openings  119 ,  121  of the alignment tool  110  to facilitate removal and installation of the sensor assembly  10 . 
     With regard to  FIG. 9A , the protection cage  230  can include first and second protection cage arms  234 ,  236  which can be disposed at an angle  13  with respect to each other around the longitudinal axis L of the tubular member  202 . As shown, the first protection cage arm  234  can be external to and about radially in-line with the first alignment cage arm  214 , and the second protection cage arm  236  can be external to and about radially in-line with the second alignment cage arm  216 . As such, the protection cage arms  234 ,  236 , can protect the alignment cage arms  214 ,  216  (as well and the sensor assembly  10  and alignment posts  44 ) from damage. In certain implementations, the protection cage  230  includes a casing, such as a door, that can be moved (e.g., swung radially and/or translated longitudinally) or removed to permit access to the sensor assembly  10 . For example, as shown in  FIG. 9B , the protection cage  230  can include at least one door  250  or other type of outer protective barrier. In some embodiments, a plurality of doors  250  can also be arrayed or arranged on the tubular member  202  for each of the protection cages  230  arrayed on the tubular member  202 . The plurality of doors  250  can be disposed around the circumference of the tubular member  202 , for example, to align with the protection cage arms  234 - 237  and permit access to the sensor assemblies  10 ,  10 ′,  10 ″, and  10 ″′, respectively. The door can include a window, latch, handle, and/or signaling indicia. 
     A plurality of alignment posts  44 , sensor assemblies  10 , protection cages  230 , and alignment cages  210  can be arrayed on the tubular member  202 . For example,  FIG. 9A  illustrates a tubular member with four sets of alignment posts  44  and sensor assemblies  10 , which are disposed about 90° from each other around the circumference of the tubular member  202 . Many other arrangements of alignment posts  44  and sensor assemblies  10  around the circumference of the tubular member are possible, such as two, three, five, six, or more alignment posts  44  and sensor assemblies  10 . Generally, the sensor assemblies  10  are equally spaced-apart around the circumference of the tubular member  202 ; however non-equal spacing is employed in certain embodiments. Further, alignment posts  44  and sensor assemblies  10  can be arrayed along the longitudinal axis L of the tubular member  202 . 
     Each sensor assembly  10  can be flanked by a protection cage  230  and alignment cage  210 . In some cases, such as in the embodiment of  FIG. 9A , the protection cages  230  share protection cage arms  234 - 237  and the alignment cages  210  share alignment cage arms  214 - 217 . As illustrated, sensor  10  is flanked by protection cage arms  234 ,  236  and alignment cage arms  214 ,  216 ; sensor  10 ′ is flanked by protection cage arms  234 ,  235  and alignment cage arms  214 ,  215 ; sensor  10 ″ is flanked by protection cage arms  235 ,  237  and alignment cage arms  215 ,  217 ; and sensor  10 ″′ is flanked by protection cage arms  236 ,  237  and alignment cage arms  216 ,  217 . Such sharing of alignment and/or cage arms can, for example, reduce the size, weight, and/or expense of the subsea strain sensor assembly  5 . In certain implementations, the alignment cage arms  214 ,  216  and the protection cage arms  234 ,  236  are separate (e.g., not connected to each other and/or include a dampener therebetween). Such a configuration can, for example, inhibit or prevent an impact to the protection cage  230  from displacing or damaging the sensor assembly  10  and/or the alignment cage  230 . Such damage or displacement could, for example, disturb the relative positioning of the alignment cage  230  and the sensor assembly  10 , which in turn could inhibit mating with the alignment tool  110  and/or could inhibit the sensor assembly  10  from being accessed and serviced (e.g., removed and replaced). 
     In some embodiments, portions of the subsea strain sensor assembly  5  are configured to be brought to the surface when not in use. For instance, some arrangements of the alignment tool  110  are configured to be lowered to desired depth and returned to the sea surface when an alignment operation is completed. In other embodiments, one or more components of the subsea strain sensor assembly  5  are maintained at a desired location along the tubular member  202 . For instance, in some cases, an alignment tool  110  is maintained underwater at or near the subsea strain sensor assembly  5 , so as to be conveniently located if needed. In some cases, the alignment tool is tethered to the protection cage  230 , alignment cage  210 , and/or the tubular member  202 . The alignment tool  110  can include various sensors (e.g., depth sensor, pressure sensor, temperature sensor) and can be configured to communicate, via a wired or wireless connection, with another device, such as an ROV, a ship, the sensor  10 , the alignment cage  210 , etc. 
     In certain configurations, such as the configuration shown in  FIG. 10 , the alignment cage  210  receives the alignment tool  110 , which in turn receives the sensor assembly  10 . In some such instances, the alignment tool  110  receives both ends of the sensor assembly  10  about concurrently, thus inhibiting displacement of the sensor  19  and/or kink in the mating of the alignment tool  110  with the sensor assembly  10 . 
     As shown, the alignment rib  220  can be received in the guide channel  116 , thereby mating the first positioning feature  118  with the second positioning feature  222 . Generally, the mating of the first positioning feature  118  and second positioning feature  222  includes sufficient mating force so that the force of the weight of the alignment tool  110  does not separate the alignment tool  110  from the alignment cage  210 . Thus, in some embodiments, the alignment tool  110  is held in the alignment cage  210  by the mating of the first and second positioning features  118 ,  222 . Among other advantages, maintaining the alignment tool  110  in the alignment cage  210  by such mating can allow an ROV to release one feature (such as the handle  120 ) in order to grasp another feature (such as the wrench  140 ). Some arrangements of the alignment tool  110  can be latched to the sensor assembly  10  by, for example, the latching mechanism discussed above. As shown, the head portion  62  of the fastener  26  can protrude through the opening  119  and/or  121  thus permitting manipulation of the fastener  26 , e.g., by the wrench  140 . 
     With regard to  FIG. 11 , an embodiment of a method of removing the sensor assembly  10  from a tubular member  202  is schematically illustrated. Such removal may be desirable when, for example, the sensor assembly  10 , has failed or is in need of repair. The method can include inserting the alignment tool  110  into the alignment cage  210 . In certain such embodiment, the alignment tool  110  receives the sensor assembly  10 . In some embodiments, the alignment tool  110  can be aligned and inserted into the alignment cage  210  by using alignment features on the cage. For example, in some embodiments of the method, the guide channel  116  receives the alignment rib  220  of the alignment cage  210 , thereby facilitating mating the alignment tool  110  with the sensor assembly  10 . 
     In some embodiments, the method further includes locking, holding, latching, or otherwise securing the alignment tool  110  in the alignment cage  210  with positioning features on one or both of the alignment tool  110  and alignment cage  210 , e.g., first and second positioning features  118 ,  222 . In some embodiments, the method further includes mating a detent on the alignment tool  110  with a recess on the alignment rib  220 . 
     Certain embodiments of the method of removing the sensor assembly include locking, holding, latching, or otherwise securing the alignment tool  110  to the sensor assembly  10 . For example, in certain implementations, the alignment tool  110  is coupled with the sensor assembly  10  by one or more latches  122 . In certain embodiments, the latches  122  are engaged by turning or rotating a locking handle or lever  124  (e.g., by 1/16, ⅛, ¼, ⅜, ½, ⅝ ¾, ⅞, 1, 1¼, 1½, 1¾, 2, 3, 4, 5, 6, 7, 8, 9, 10 turns, values in between, and otherwise). In some embodiments, as discussed above, the lever  124  can be coupled to a cam  132  which can contact one or more tappets  134  that are connected to a translation member  136 . The translation member, in turn, can be connected to one or more latch elements  122 . Thus, in some embodiments, the method can include rotating the lever  124  and translating the latch elements  122  into an extended position to be received by the notch  28  of the sensor assembly  10  and securing the alignment tool  110  to the sensor assembly  10 . 
     Some embodiments of the method further include decoupling the sensor assembly  10  from the tubular member  202 . For example, the method can include loosening the fasteners  26  (e.g., by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 turns, values in between, and otherwise). In some embodiments, the decoupling (e.g., loosening the fastener  26 ) is accomplished with the wrench  140  and/or with an electric or hydraulic motor. In some embodiments, the wrench is manipulated by an ROV. 
     Some implementations of the method include removing the alignment tool  110  and sensor assembly  10  from the alignment cage  210 , spool  56 , and/or alignment post  44 . For example, the alignment tool  110  and sensor assembly  10  can be separated from the alignment cage  210 . In some such embodiments, the alignment tool  110  and sensor assembly  10  are brought to the sea surface. Certain embodiments can include removing the sensor assembly  10  from the alignment tool  110 . Further implementations include removing the sensor  19  from the sensor assembly  10 . 
     In some embodiments, all or certain portions of the method are accomplished with an ROV. For example, in some embodiments, the ROV inserts the alignment tool  110  into the alignment cage  210 . In certain implementations, the ROV turns the locking handle or lever  124 . In some variants, an ROV loosens the fastener  26 . In some embodiments, an ROV removes the alignment tool  110  and sensor assembly  10 . 
     As shown in  FIG. 12 , in some embodiments, a method of installing the sensor assembly  10  on the tubular member  202  includes coupling the sensor assembly  10  with the alignment tool  110 . The method of installing the sensor assembly  10  can include any or all of the portions of the method of removing the sensor assembly  10 , as described above, though the portions may be in a different order or sequence. In certain instances, the sensor assembly  10  and the alignment tool  110  are positioned in the vicinity of the alignment cage  210  and the alignment posts  44 , e.g., underwater. 
     In some embodiments, the method also includes engaging, inserting, or mating the alignment tool  110  with the alignment cage  210 . For example, the alignment tool  110  can be held in the alignment cage  210  with positioning features on one or both of the alignment tool  110  and alignment cage  210 , e.g., first and second positioning features  118 ,  222 . In some such instances, the guide channel  116  of the alignment tool  110  can receive the alignment rib  220  of the alignment cage  210 , thereby facilitating alignment of the alignment tool  110  and the alignment cage  210 . In some embodiments, the method further includes mating a detent on the alignment tool  110  with a recess on the alignment rib  220 . In certain implementations, such alignment and mating of the alignment tool  110  and the alignment cage  210  results in the sensor assembly  10  being aligned with the alignment posts  44 . Indeed, certain arrangements include receiving the alignment posts  44  into the sensor assembly  10 . 
     Certain embodiments of the method of installing the sensor assembly  10  on the tubular member  202  include locking, holding, latching, or otherwise securing the alignment tool  110  to the alignment cage  210 . For example, some embodiments include tightening (e.g., by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 turns, values in between, and otherwise) the fastener  26  of the sensor assembly  10 . In some embodiments, tightening the fastener  26  is accomplished with a wrench  140  and/or with an electric or hydraulic motor. In some embodiments, the tightening of the fastener  26  occurs by turning twice in the counter-clockwise direction and about ten times in the clockwise direction. Various other combinations and number of turns can be used to tighten the fasteners  26 . As discussed above, in some embodiments, the method or at least one portion of the method can be accomplished using an ROV. Some arrangements include connecting the sensor assembly  10  to the alignment post  44 . 
     In some embodiments, the method includes disengaging, unlocking, decoupling, or otherwise releasing the alignment tool  110  from the sensor assembly  10 . For example, in certain implementations the sensor assembly  10  is released from the alignment tool  110  by turning or rotating the locking handle or lever  124  (e.g., by 1/16, ⅛, ¼, ⅜, ½, ⅝, ¾, ⅞, 1, 1¼, 1½, 1¾, 2, 3, 4, 5, 6, 7, 8, 9, 10 turns, values in between, and otherwise). 
     In some embodiments, the method also includes disengaging, unlocking, decoupling, or otherwise releasing the alignment tool  110  from the alignment cage  210 . Certain embodiments include separating the alignment tool  110  from the sensor assembly  10 . Some implementations also include separating the alignment tool  110  from alignment cage  210  and the alignment posts  44 . For example, in certain cases, the alignment tool  110  is brought to the sea surface and the sensor assembly  10  remains coupled with the tubular member  202  underwater. 
     In certain implementations it can be desirable to calibrate the sensor  19 . In some embodiments, a method of calibrating a sensor includes providing a sensor so as to measure a condition (e.g., strain) on a tubular member in an unloaded or unstrained condition (e.g., at sea level, prior to operation), measuring a first output from the sensor in the unloaded condition, measuring a second output from the sensor when the sensor and/or tubular member is in a loaded or strained condition (e.g., subsea, during operation), and comparing the first and second outputs to determine a measured value. In some embodiments, the comparison is accomplished according to the following formula:
 
Measured Value=Second Output−First Output
 
     For example, in some embodiments, a strain sensor is installed on a tubular member and the output of the sensor is measured in an un-strained condition as 2 microstrain; the sensor and the tubular member are then lowered to the sea floor, and loaded, and the second output of the sensor is 350 microstrain; the microstrains are compared to determine a measured value of 348 microstrain (e.g., 350 microstrain−2 microstrain=348 micro strain). 
     In scenarios in which a sensor fails or needs replacement, it is generally desirable to replace the sensor while the tubular member is at the loaded or strained condition (e.g., subsea, during operation). However, as there may have never been an opportunity to measure the first output in the unstrained condition, and also because sensors are generally not perfectly repeatable, the replacement sensor may not exhibit the same measured value as the replaced sensor, thus the measured value of the replacement sensor may deviate from the measured values of other sensors (e.g., sensors that have not been replaced). Further, as it may not be not practicable to raise the tubular member to the surface, determining a first output value for the replacement sensor using the procedure discussed above may be undesirable. Accordingly, the subsea strain sensor assembly  5  and methods of use thereof can be configured to determine a calibration value of a replacement sensor without the need to raise the tubular member to the surface. 
     For example, in some embodiments, at least three sensors are non-collinearly disposed on the tubular member and a calibration value determined for each of the at least three sensors. The calibration value for each of the at least three sensors can be considered collectively to determine a strain distribution plane (for example, by the method of least-squares), which can describe the net effect of both tensile strain and bending strain. In some embodiments, the strain plane is defined according to the following formula:
 
 z=Ax+By+C  
 
     Where A is the slope of the strain plane in the x-axis (orthogonal to the longitudinal axis L), B is the slope of the strain plane in the y-axis (orthogonal to the x-axis and to the longitudinal axis L), C is an offset of the strain plane, and x, y, and z are coordinates on the strain plane. In particular, z is generally the strain at a point on the strain plane.  FIG. 14  provides a graphical representation of an embodiment of a strain plane in a portion of a tubular member. 
     Given that a replacement sensor is generally installed at about the same location as a replaced sensor, which has a known position on the circumference of the tubular member (and thus has known x and y coordinates), the x and y coordinates of the replacement sensor are also generally known. Accordingly, the measured strain (z on the strain plane corresponding to the known x and y coordinates) can be compared to the second output of the replacement sensor in order to determine a theoretical first output value for the replacement sensor. Thus, in some embodiments, the comparison is done according to the following formula:
 
First Output Value=Second Output−Measured Value
 
     The first output value for the replacement sensor can be subtracted from the second output of the replacement sensor thereby fitting the measured output of the replacement sensor to the strain plane. 
     Although the foregoing has been described in terms of certain specific embodiments, other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. Moreover, the described embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. For instance, embodiments of the subsea strain sensor assembly have been described for use with a tubular member; however many other applications are possible, such as but not limited to use with solid members, I-beam members, flat members, flanged members, plate members, dome members, spherical members, or the like. Indeed, the novel methods and systems described herein can be embodied in a variety of other forms without departing from the spirit thereof. For example, components can be constructed from materials other than those disclosed herein. Similarly, components can be differently shaped and/or oriented than illustrated or described herein. Further, various ways of assembly and/or fastening are contemplated, including screws, nuts, bolts, adhesives, press-fit, slip-fit, clamps and the like. For example, in some cases, the sensor assembly fastens to the alignment posts by one or more clasps rather than by the threaded fastener described above. In yet a further combination, the sensor assembly clamps directly to the tubular member. In still a further arrangement, one or more components can be configured to have and/or be provided with desired buoyancy, e.g., neutral buoyancy, such as by coupling to a float. Other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Thus, the present disclosure is not limited by the embodiments described above.