Patent Publication Number: US-11644371-B1

Title: Systems, devices and methods for monitoring support platform structural conditions

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This continuation patent application claims priority from co-pending United States Non-Provisional Patent Application having Ser. No. 17/571,472, filed 8 Jan. 2022, entitled “SYSTEMS, DEVICES AND METHODS FOR MONITORING SUPPORT PLATFORM STRUCTURAL CONDITIONS”, having a common applicant herewith and being incorporated herein in its entirety by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosures made herein relate generally to monitoring of operating conditions of structural members and, more particularly, to systems, devices and methods for monitoring support (e.g., offshore) platform structural conditions. 
     BACKGROUND 
     Structural bodies for which it is necessary to monitor structural conditions thereof are well-known and are used in many industries and applications. Elongated tubular bodies (e.g., pipes) and enclosed tubular bodies (e.g., hulls and pontoons) are examples of structural bodies having with an interior space. Pipes, hulls and pontoons used in offshore drilling and production systems in the oil and gas industry are a prime example of structural bodies for which it is necessary to monitor structural conditions thereof. It is desirable if not essential to monitor parameters such as, for example, stress, strain and temperature of structural bodies, particularly in structural bodies of offshore drilling and production systems. 
     Offshore drilling and production systems include a work platform at a sea surface (i.e., an offshore platform) that is in communication with a subsurface exploration and/or production site. The offshore platform includes a floatation structure for allowing it to float at the sea surface. Such a floatation structure is well known to often include a hull comprising an enclosed main body (e.g., a columnar shaped body) and a plurality of buoyancy tanks (e.g., pontoons) attached thereto in typically an equally-spaced manner. 
     A tendon leg platform (TLP) is a specific example of offshore platform having a platform structure for which operating conditions need to be monitored. A TLP, which is typically a permanently positioned structure used for the production of oil and gas in offshore environments, uses a platform structure comprising tendons (i.e., also referred to as tension legs) to support platform elements above the sea surface. TLPs have recently been implemented for use as a base for offshore wind turbines. 
     TLPs are moored to the seabed by a plurality of tendons each connected to a respective piling that has been driven into the seabed at one end and connected to a respective location of a respective buoyancy tank at the other end (e.g., respective location of a respective pontoon). The tendons of a TLP, which are typically made of tubular steel, maintain the TLP in a generally static position thanks to the balance between thrust forces due to flotation and fastening forces generated by the anchoring elements (tendons and seabed pilings). The tendons restrict vertical motion of the platform that would otherwise occur due to tides and wave action. A major advantage results for TLP structures is that an associated wellhead can be placed on the TLP platform rather than on the sea floor thereby providing better access to the wellhead and more simple production control. 
     As is well-known, it is desirable to operate drilling and production systems in a safe, reliable, predictable and efficient manner. It is thus beneficial to monitor operating condition information of elongated tubular members of drilling and production systems, such as a TLP. To this end, in a typical TLP installation, a plurality of load cells (i.e., load sensors) are installed into a tendon top connector assembly, which is on a sub-platform or bridge for each tendon. Data from these load cells is used to monitor operating conditions in support bodies of the TLP—e.g., tendons, pontoons, hull or a combination thereof. Specific examples of operating conditions include, but are not limited to, strain and/or stress within one or more walls of a support member, pressure within an interior space of a support member, torsion applied to a support member, temperature of a wall or surface of a support member and the like. In this regard, tendon tensions provide data that enables assessment of loading condition of the TLP; measurement of horizontal center-of-gravity (“COG”) and platform weight; determination of platform location (e.g., in a “load triangle”; management of tendon fatigue and the like. 
     Historically, load cells in offshore applications are becoming less unreliable and often fail during later phases in their service life due to age and possible exposure to seawater and other harsh environmental conditions. Additionally, the load cells offer only limited precision and accuracy in regard to their acquired data. Therefore, systems, devices and methods for enabling generation and monitoring of support platform structural conditions in a manner that overcomes drawbacks associated with conventional approaches for generating and monitoring similar operating condition information would be advantageous, desirable and useful. 
     SUMMARY OF THE DISCLOSURE 
     Embodiments of the disclosures made herein are directed to systems, devices and methods for enabling generation and monitoring of support platform structural conditions in a manner that overcomes drawbacks associated with conventional approaches (e.g., load cells) for generating and monitoring similar operating condition of tendon loads and riser strain information. In preferred embodiments, these systems, devices and methods for enabling generation and monitoring of support platform structural conditions utilize fiber optic strain gauges (i.e., fiber optic sensors) in place of (e.g., retrofit/data replacement) or in combination with conventional load cells. The fiber optic sensors are strategically placed at a plurality of locations on one or more support bodies of a support platform. In preferred embodiments, the fiber optic sensors are placed in positions within one or more interior locations such as buoyancy tanks of an offshore platform (e.g., a hull and/or one or more pontoons). Such positions are selected whereby resulting operating condition data generated by the fiber optic strain gauges suitably, if not beneficially, replaces or augments data received by conventionally constructed and located load cells of an offshore platform (e.g., a TLP). 
     In one or more embodiment of the disclosures made herein, a method of instrumenting an offshore platform for enabling monitoring of structural loadings exerted within elongated bodies mooring the offshore platform to a seabed is provided. The method includes accessing a support member that is within an interior space of a pontoon of the offshore platform and that is fixedly attached to wall portions thereof and attaching a plurality of fiber optic strain gauges to a respective surface of the support member. 
     In one or more embodiments of the disclosures made herein, a method of enabling instrumentation of a TLP to enable monitoring of structural loadings exerted within tendon legs mooring the TLP to a seabed is provided. The method comprises selecting a support member within an interior space of a pontoon of the TLP for being instrumented to monitor strain therein, performing a structural analysis of the support member and determining strain gauge placement information for each of a plurality of fiber optic strain gauges to be attached to the support member. The structural analysis is performed to determine a strain field profile within the support member resulting from loadings exerted on the pontoon by one or more tendon legs attached thereto. Determining the strain gauge placement information is performed at least partially as a function of the strain field profile. The placement information includes a location of the support member at which a particular one of the fiber optic strain gauges is to be attached. 
     In one or more embodiments of the disclosures made herein, a TLP comprises a hull and plurality of sets of fiber optic strain gauges. The hull has a main body and a plurality pontoons attached to a lower portion of the main body. Each of the pontoons has a plurality of support members within an interior space thereof that are each fixedly attached to wall portions thereof. Each fiber optic strain gauge of a set is attached to a surface of one of the support members of a respective one of the pontoons. Each fiber optic strain gauge of a set is attached to the surface with a sensing axis thereof oriented one of parallel to, perpendicular to and at an acute angle to a vertical reference axis of the hull. 
     In one or more embodiments, all of the fiber optic strain gauges are attached to a common surface of the support member and the common surface is a contiguously extending surface. 
     In one or more embodiments, the contiguously extending surface is a planar surface or a curved surface. 
     In one or more embodiments, a method further includes performing a structural analysis of the support member to determine a strain field profile within the support member resulting from the support member being subjected to loadings at points of attachment thereof with the wall portions of the pontoon. 
     In one or more embodiments, a location of the respective surface on which each fiber optic strain gauge is attached and an angular orientation of a sensing axis thereof are both at least partially determined as a function of the strain field profile. 
     In one or more embodiments, the strain field profile identifies a plurality of strain field regions each exhibiting strain in a respective generalized strain direction relative to a vertical reference axis laying within a planar surface. 
     In one or more embodiments, attaching each fiber optic strain gauge to a respective surface of the support member includes attaching each of the fiber optic strain gauges to the respective surface within a respective one of the strain field regions with a sensing axis thereof at least approximately aligned with the generalized strain direction of the respective one of the strain field regions. 
     In one or more embodiments, each fiber optic strain gauge of a first portion of the plurality has a sensing axis thereof extending approximately parallel to the vertical reference axis that lays within a planar surface of the support member, each fiber optic strain gauge of a second portion of the plurality different than the first portion has a sensing axis thereof extending approximately perpendicular to the vertical reference axis and each fiber optic strain gauge of a third portion of the plurality different than the first and second portions has a sensing axis thereof extending at an acute angle relative to the vertical reference axis. 
     In one or more embodiments, the support member is one of webframe and a bulkhead. 
     In one or more embodiments, the support member is a webframe located adjacent to a tip tank of the pontoon. 
     In one or more embodiments, the support member is a webframe located within a water-fillable tip tank of a pontoon. 
     In one or more embodiments, placement information derived from a structural analysis comprises a planar surface of the support member to which all of the fiber optic strain gauge are attached. 
     In one or more embodiments, placement information derived from a structural analysis comprises a plurality of strain field regions each exhibiting strain in a respective generalized strain direction relative to a vertical reference axis laying within a planar surface. 
     In one or more embodiments, the strain field profile identifies a plurality of strain field regions each exhibiting strain in a respective generalized direction relative to a vertical reference axis laying within the planar surface. 
     In one or more embodiments, each fiber optic strain gauge of each set is positioned at a location of the support members of a respective one of the pontoons in accordance with a strain field profile within the support member resulting from loadings exerted on the pontoon by one or more tendon legs attached thereto. 
     In one or more embodiment, fiber optic temperature compensation is provided with a separate fiber optic sensor that is isolated from the strain field and only reacts to temperature or is placed at an off angle orientation such as a conventional strain rosette. 
     These and other objects, embodiments, advantages and/or distinctions of the present invention will become readily apparent upon further review of the following specification, associated drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a prior art single column tension-leg mooring system; 
         FIG.  2    is a cross-sectional view taken along the line  2 - 2  in  FIG.  1   ; 
         FIG.  3    is a block diagram view of a TLP configured in accordance with one or more embodiment of the inventive disclosures made herein; 
         FIG.  4    is a diagrammatic view of a tendon tension monitoring system configured in accordance with one or more embodiment of the inventive disclosures made herein; 
         FIG.  5    is a plan view showing a support member instrumented with a plurality of fiber optic strain gauges; 
         FIG.  6    is a cross-sectional view of a prior art dual core fiber optic cable; 
         FIG.  7    is a plan view of an isolation device configured in accordance with one or more embodiments of the disclosures made herein; and 
         FIG.  8    is a cross-sectional view taken along the line  8 - 8  in  FIG.  7   . 
     
    
    
     DETAILED DESCRIPTION 
     A discussion regarding a prior art tendon leg platform (TLP  10 ) is now set forth in reference to  FIGS.  1  and  2   , which is generally identified by the reference numeral  10 . A SeaStar brand TLP is an example of the TLP  10  shown in  FIGS.  1  and  2   . Aspects of the SeaStar brand TLP hull design are disclosed in U.S. Pat. No. 5,964,550, which is incorporated herein in its entirety by reference. 
     The TLP  10  includes a hull  12  which provides positive buoyancy and vertical support for the TLP  10 , including a platform deck structure  14 . The platform deck structure  14  may be sized and arranged in accordance with an intended use of the TLP  10 —e.g., oil and gas production, oil and gas exploration, wind turbine placement, and the like. The hull  12  may comprise a single column  16  extending upward from a base formed by a plurality of radially extending pontoons  18 . In the preferred embodiment of  FIG.  1   , three pontoons  18  form a base of the hull  12 . It is understood however that fewer than or greater three pontoons may be incorporated in the design of a TLP. The pontoons  18  extend radially outward from the longitudinal axis of the hull  12  and are preferably equally spaced from each other. The hull  12  is fabricated in a welded manner from plates, stiffened shell constructions and the like. 
     The TLP  10  is anchored to a seabed  21  by tendons  17  which are secured to the pontoons  18  at the upper ends thereof and to foundation piles  19  embedded in the seabed  21  at the lower ends thereof. The hull  12  provides sufficient buoyancy to support the platform deck structure  14  as well as equipment/infrastructure thereon and/or attached thereto. Crucially, the hull  12  has sufficient excess buoyancy to develop pre-tension within the tendons  17 . 
     The hull  12  may include a plurality of stacked buoyancy tanks  20 . The tanks  20 , as best shown in  FIG.  2   , include an outer wall  21  and an inner wall  23  defining a ballast chamber therebetween. The walls  21  and  23  have top and bottom edges. A top horizontal plate  25  welded to the top edges of the walls  21  and  23  completes the substantially cylindrical structure of the buoyancy tanks  20  which, prior to assembly of the hull  12 , are open at the bottom end. Additional structural integrity for the tanks  20  may be provided by stiffener flanges  15  welded to the inner surface of the tank walls  21  and  23 . The stiffener flanges  15  may be about three inches in width and one inch thick substantially equally spaced along the walls  21  and  23  of the tanks  20 . The buoyancy tanks  20  further include an axial passage extending therethrough, which axial passage is open at each end. 
     The ballast tanks  20  are stacked one on the other and welded to form the single column of the hull  12 . Upon welding one tank  20  on another, the top plate  25  of the lower tank  20  forms the bottom of the tank  20  directly above it. The axial passages extending through the ballast tanks  20  are aligned to form a central axial chamber  22  closed at its lower and upper ends. The chamber  22  is empty and provides internal access to the hull  12 . The upper end of the chamber  22  is defined by a cylindrical extension  33  welded to the top of the uppermost tank  20 . The extension  33  projects above the uppermost tank  13 , providing access to the axial chamber  22  from topside. The chamber  22  and extension  33  additionally house the internal plumbing and valving for the ballast system of the platform  10  which permits the operator to selectively flood or empty the tanks  20  and the pontoons  18 . 
     As shown in  FIG.  2   , each pontoon  18  includes top and bottom horizontal plates  32  and  34  spaced from each other and connected by opposing sidewalls  36 , an internal cylindrical wall  38  and an end wall  39 . To optimize the base structure for carrying tendon induced bending moments, the pontoons  18  preferably taper slightly inwardly toward their distal ends. The structural integrity of the pontoons  18 , which are the primary load bearing members of the hull  12 , is further enhanced by webframes  40  and one or more bulkheads  40 ′. The webframes  40  and bulkheads  40 ′ are internally welded to the top and bottom plates  32  and  34  and to the sidewalls  36 , and are typically equally-spaced internally along the length of a respective one of the pontoons  18 . The perimeter of the webframes  40  and bulkheads  40 ′ may have receptacles  43  (e.g., slots) to receive stiffener flanges  41  for reinforcing walls of the pontoons  18 . 
     Turning now to disclosures characterizing the inventive subject matter set forth herein, pontoons of a floating platform are instrumented with fiber optic strain gauges to enable monitoring of loads applied to the pontoons during such floatation. This instrumentation may be implemented during new construction of a platform, refurbishment or repair of a platform, or during use of the platform while at sea. A first benefit to instrumentation in accordance with embodiments of the inventive subject matter is improved measurement attributes (e.g., sensitivity, accuracy and repeatability and the like) relative to convention load cells. A second benefit is improved durability relative to convention load cells (e.g., lifespan of several decades as opposed to several years.) 
     Referring now to  FIG.  3   , a TLP configured in accordance with one or more embodiments of the inventive disclosures made herein (TLP  100 ) is described. The TLP  100  includes a hull  105  including a plurality of pontoons  110 . In this regard, the TLP  100  may have a design substantially the same as the TLP  10  discussed above in reference to  FIGS.  1  and  2   . Each pontoon  110  includes a plurality of support members  115  (e.g., a plurality of webframes  40  and one or more bulkheads  40 ′). In one particular implementation, each pontoon  110  has a bulkhead located adjacent a tip portion thereof to create a tip tank at the terminal end portion of the respective pontoon. As is well known in the art, the tip tank is a sealable space in which desired amounts of ballast water may be selectively stored and evacuated. 
     As shown in  FIG.  3   , the TLP  100  includes a tendon tension monitoring system (TTMS)  120 . The TMMS  120 , as shown in  FIGS.  3  and  4   , comprising a plurality of optical fiber strain gauges  125 , a signal processor  130  and a computer  132 . In some embodiments, the signal processor  130  and the computer  132  are the only electrical components of the TTMS  120 . Each optical fiber strain gauges  125  is in-line spliced with a respective optical fiber  138   a - 138   m  of a respective one of a plurality of optical fiber cables  135   a - 135   n  (where m=9 (i.e.,  138   a - 135   i ) and n=9 (i.e.,  135   a - 135   i ) in  FIG.  4   ). Each optical fiber strain gauges  125  is operatively coupled to the signal processor  130  via the corresponding optical fiber  138   a - 138   m  of the respective one of the optical fiber cables  135   a - 135   n . Such operable coupling enables a signals (light) from the signal processor  130  to be provided to each of the optical fiber strain gauges  125  and for a return signal to be provided from each optical fiber strain gauge  125  to the signal processor  130 . These signals are provided over a respective optical fiber  138   a - 138   m  of the respective one of optical fiber cables  135   a - 135   n.    
     Each optical fiber strain gauge  125  is attached to a surface of a support member  115  of a respective one of the pontoons  110 . In preferred embodiments, each optical fiber strain gauge  125  is attached to a planar surface of a particular support member  115  (e.g., a webframe). The optical fiber strain gauges  125  are each fixedly attached preferably via a rigid bonding technique (e.g., bonding via epoxy) to a support member  115  of a respective one of the pontoons  110 . Such fixed attachment of an optical fiber strain gauge  125  to the respective one of the support members  115  enables a strain within a respective one of a plurality of regions R 1 -R 7  of the support member  115  where a particular one of the optical fiber strain gauges  125  is attached to cause a corresponding and proportional elongation of the optical fiber strain gauge  125 . 
     Preferably, the optical fiber strain gauges  125  are arranged as a set, where each optical fiber strain gauge  125  of a set is in-line spliced with a respective one of the optical fibers  138   a - 138   i  of a respective one of the optical fiber cables  135   a - 135   n . It is well known that each of the optical fiber cables may include a plurality of optical fibers  138   a - 138   m  and that each optical fiber  138   a - 138   m  may exit from within an inner and outer jacket of the respective one of the optical fiber cables  135   a - 135   n  to permit individual attachment to a strain gauge or a length of optical fiber. For example, in the context of the TLP  100 , a particular one of the pontoons  110  may be served by one or more of the optical fiber cables  135   a - 135   n  and each support member of the particular one of the pontoons  110  may be served by one or more optical fibers of the one or more optical fiber cables  135   a - 135   n  serving the particular pontoon. 
     In addition to the fiber optic strain gauges  125 , one or more temperature sensor may be implemented for providing operating condition information through which temperature of a space within which fiber optic strain gauges are located (e.g., space within a pontoon  110 ) can be determined. Preferably, the temperature sensor may be in the form of a fiber optic strain gauge that remains unbonded from a support member (i.e., fiber optic temperature gauge). A strain gauge serving as the temperature sensor may be encapsulated in a rigid material (i.e., an epoxy or the like) to protect and rigidize the strain gauge. The temperature compensation may also consist of additional off axis gauges relative to the strain gauge orientation. 
     Bragg grating, which are well-known to a person of ordinary skill in the art of optical fibers, is a preferred implementation of the strain and temperature gauges disclosed herein. Wavelength for the Bragg gratings may range from about 1200 to about 1700 nanometers with reflectively thereon being generally greater than about 10% and preferably near 70-90%. 
     In one or more embodiments, the signal processor  130  may comprise an optical sensing module (OSM)  150  and a multiplexing unit (MUX)  155 . The OSM  150  is preferably a fiber Bragg grating (FBG) optical interrogator. At least a portion of the optical fibers  138   a - 138   m  may be connected directly to a respective signal channel  165  of the OSM  150  or may attached to a signal channel  165  of the OSM  150  through a Time Division Multiplexing (TDM) module  170  of the MUX  155 . As is well known in the art, the MUX  155  and TDM module  1  enables a plurality of optical fibers to be selectively connected to a single signal input of the OSM  150 , thereby extending optical fiber signaling capacity of the OSM  150 . 
     The OSM  150  sends an emitted light signal along a particular optical fiber connected thereto and thereafter analyzes reflectance (i.e., operating condition) signal generated by each optical fiber strain or temperature gauges of the optical fiber. Each optical fiber strain gauge is configured to interact with a respective different wavelength of the emitted light that is transmitted (i.e., transmitted signal) along the optical fiber. Such interaction generates a corresponding reflectance (i.e., detected) signal that characterizes a changes in the load exhibited within at the respective location of a support member to which an associated strain gauge is attached or temperature of an environment within which an associated strain gauge is located. The OSM  150  converts the detected optical signal to a corresponding (e.g., proportional) electrical signal and provides the electrical signal to the computer  132  via a suitable connection. 
     As best shown in  FIG.  4   , the computer  132 , which is preferably a server, has a software program  175  (i.e., a computer-readable non-transitory medium) that is accessible from memory  180  of the computer  132  and is executable by one or more processors  185  of the computer  132  thereof. Through analytic assessment of the electrical signals provided to the computer  132  from the OSM  150  (i.e., corresponding to detected optical signals) by the software  175 , highly accurate estimates of load levels within one or more tendon legs attached to the respective one of the pontoons  110  and temperature in a particular location thereon can be determined via the software program  175  as a function of strain sensed by one or more associated strain gauges  125 . The software program  175  is preferably a custom application developed to perform the functions of the TTMS  120 . The computer  132  is preferably remotely accessible through a suitable connection from an integrated marine management system (IMMS) computer  187  through which overall buoyance control of the TLP  100  may be managed. 
     Still referring to  FIG.  4   , each of the optical fibers  138   a - 138   m  preferably and advantageously include opposing end portions configured for being operably connected to any one of the signal channels  165  of the OSM  150 . Additionally, the OSM  120  preferably includes a suitable number of channels to accommodate connection of each optical fiber optical fibers  138   a - 138   m  (including via the MUX  155 ) while at least one of the signal channels  165  remains unused such that it may serve as a spare signal channel  166 . In this manner, if a particular one of the optical fibers  138  experiences a break between the end thereof connected to the assigned one of the signal channels  165  (connected end  168 ) and any of the fiber optic strain gauges thereof, an unconnected end  169  of the particular one of the optical fibers  138  may be connected to the spare signal channel  166  to enable signal transmission for fiber optic strain gauges on the otherwise inaccessible side of the break. To this end, each of the optical fibers  138   a - 138   m  is preferably in the form of a loop comprising two optical fibers of a respective optical fiber cable having adjacent end portions thereof at a distal end portion of the respective optic fiber cable thereof (i.e., end remotely located relative to the OSM  150 ) connected together via a connection  171  (e.g., via a physical connector, fusion splicing or the like). 
     TTMS functionality as disclosed herein is exceptionally valuable in the case of a TLP having optical fiber strain gauges as an original equipment installation or optical fiber strain gauges as a retro-fitted installation. For example, in the case of a TLP with one or more failed originally-installed load cells, an optical fiber strain gauge implementation as disclosed herein can be installed for enabling monitoring of tendon leg loadings. Where one or more originally-installed load cells remain operational, load information therefrom may be used for establishing and validating a correlation function and/or calibration function (i.e., stress as a function of measured strain) for the installed optical fiber strain gauges. 
       FIG.  5    shows a support member  115  instrumented with a plurality of which fiber optic strain gauges  125  (for clarity, associated optical fiber is not shown). Each of the fiber optic strain gauges  125  is fixedly attached (e.g., bonded with an adhesive such as epoxy) to the support member  115  at a respective location on a face F of the support member  115  and with a sensing axis SA thereof oriented in a manner that are at least partially defined as a function of a strain field profile of the support member  115 . The respective location of each fiber optic strain gauge  125  is within a particular region R of the support member  115 . The sensing axis SA of each fiber optic strain gauge  125  is at least approximately aligned with a generalized strain direction of the respective strain field region R relative to a centerline vertical reference axis V. 
     The strain field profile is influenced by characteristics of the particular support member such as shape, thickness, openings extending therethrough, perimeter attachment locations, and the like. For example, in the case of the support member  115  shown in FIG.  5 , the strain field profile thereof at least partially results from the particular support member  115  being subjected to loadings exerted at points of attachment of the particular support member  115  with wall portions of the respective one of the pontoons  110 —e.g., perimeter edges  115 A and/or receptacles  115 B which are each typically welded to a mating portion of a respective pontoon  110 . 
     In one or more preferred embodiments, structural analysis of a particular support member (e.g., the support member  115 ) may be performed to determine a strain field profile within the particular support member. Finite element analysis is an example of such structural analysis, where numeric data indicating both a level of strain (e.g., at nodes of a computational mesh applied to a structural element being analyzed) and strain direction (e.g., derived from patterns within the numeric data) is generated. Aspects of structural analysis for determining strain and strain direction within a structural element are disclosed in U.S. Pat. Nos. 7,447,614 and 8,612,186, which are incorporated herein in their entirety by reference. 
     In preferred embodiments, the face F of the support member  115  is a planar surface and the planar surface is defined by a solid body of material. The planar surface may be that of a plurality of discrete pieces of material that are permanently attached to each other (e.g., via welding) or may be that of a single piece of material. In one or more embodiments, the generalized strain direction of each strain field region R extends one of approximately parallel to the centerline vertical reference axis V that lays within the planar surface of the support member (i.e., SD 1 ), approximately perpendicular to the vertical reference axis V (i.e., SD 2 ) and at an acute angle relative to the vertical reference axis V (i.e., SD 3 ′ or SD 3 ″). The fiber optic strain gauges  125  are preferably positioned in a mirror image arrangement relative to the centerline vertical reference axis V. 
     As discussed above, all or a portion of the optical fiber strain gauges may be located within a water-filled containment space (e.g., tip tank) of a buoyancy tank (e.g., a pontoon). It is preferred, if not required, for an optical cable extending from the water-filled containment space to an adjacent dry space within the buoyancy tank to not enable water from within the water-filled containment space to flow into the adjacent dry space. For example, an optical fiber cable may extend through a water-tight separating wall (e.g., bulkhead) between the water-filled containment space and the adjacent dry space in the case (e.g., via a Brattberg penetration arrangement) in the case where a support member within the water-filled containment space is instrumented with fiber optic strain gauges. 
     Referring to  FIG.  6   , the inventor discovered that water may flow internally along a length of a multi-fiber optical cable  200  due to a space between spaced-apart optical fibers  205  of the cable  200  being inadequately (e.g., incompletely) filled by a polymeric material from which an over-molded outer jacket  210  of the cable  205  is formed. Specifically, a fluid flow passage  215  is sometimes formed between the spaced-apart optical fibers  205  within the over-molded outer jacket  210 . Although this fluid flow passage  215  may be minute in overall cross-sectional size and have non-uniform shape, head pressure of the water in the water-filled containment space may be sufficient to cause water within water-filled containment space to flow into the fluid flow passage  215  via an exposed end portion of the outer jacket  210  that is located within the water-filled containment space and flow out of the fluid flow passage  215  into the adjacent dry space via an exposed end portion of the outer jacket  210  that is located within the adjacent dry space on the opposing side of the water-tight separating wall. 
     As a solution to this unacceptable problem, the inventor devised an isolation device  300 , shown in  FIGS.  7  and  8   , to inhibit this undesirable fluid flow consideration. The isolation device  300  includes main body  303  and opposing end caps  307 . The main body  303 , which may be in the form of a hollow body (e.g., a tube that may be cylindrically shaped), is at least long enough to contain therein all fibers of a fusion splice of one or more fibers of optical fiber cables  200  at the fusion splice location thereof and the end portions  201  of to-be-adjoined pieces of the optical fiber cables  200 . Each of the end caps  307  has a first end portion  307 A and a second end portion  307 B that jointly define a central passage of a respective one of the end caps  307  through which an end portion  201  of a respective one of the to-be-adjoined pieces of the optical fiber cables  200  may pass. The first end portion  307 A of each end cap  307  is configured for providing a water-tight circumferential seal around respective piece of the cable  200 —e.g., via an integral or discrete resilient sealing member. The second end portion  307 B of each end cap  307  is suitably configured for providing a water-tight seal with the interior and/or exterior surface of the main body  303 —e.g., in a similar or different manner as the first end portion  307 A. 
     In use, where the cable  200  is being used in the aforementioned pass-through application between a tip tank and adjacent dry space of a buoyancy tank (i.e., an egress cable), the isolation device  300  is utilized in combination with an inline fusion operation performed on the one or more optical fibers  205  of the to-be-adjoined pieces of the cable  200 . Prior to the fusion splice operation, the main body  303 , with a first one of the end caps  307  engaged therewith, is placed over the end portion  201  of a first one of the to-be-adjoined pieces of the cable  200  (end-capped end first) and a second one of the end caps  307  is placed over the end portion  201  of a second one of the to-be-adjoined pieces of the cable  200 . Next, the one of more optical fibers  205  of the first and second to-be-adjoined pieces of the cable  200  are subjected to a fusion splice operation for adjoining mating glass cores  205 A of the optical fibers  205  of the first and second to-be-adjoined pieces of the cable  200 . The main body  303  (with the first one of the end caps  307  attached) is then positioned such that the fusion splices and end portions  201  of the to-be-adjoined pieces of the cable  200  are within a central passage  309  of the main body  303 . The main body  303  is then oriented vertically with the attached end cap  307  firmly engaged and the other endcap positioned to allow access to the central passage  309  of the main body  303  through the upper end of the main body  303 . A sealing material  311  is then deposited through the upper end of the main body  303  to fill the central passage  309  of the main body  303  and associated volume of the attached end cap  307  (i.e., an internal sealing material). Subsequently, the end cap  307  adjacent to the upper end of the main body  303  is moved into secure engagement with the adjacent end of the main body  303 . A volume of the end cap  307  that is engaged with the upper end of the main body  303  may be filled with a suitable volume of the sealing material  311  such as, for example, through a small hole therein. The entire apparatus is held in place where the polyurethane is allowed to cure. The isolation device  300  may be covered with a suitable sealing material (i.e., external sealing material) for further protection to water ingress. 
     The isolation device  300  is not limited to particular sealing materials. Preferred internal sealing materials will bond to the sheath  210  of the optical fiber cables  200  and to the glass cores  205 A of the optical fibers  205  and any polymeric coating on the glass cores  205 A. Preferred external sealing materials will bond to the sheath  210  of the optical fiber cables  200  and to main body  303 . Two-part liquid polyurethane is an example of a preferred internal sealing material. Polysulfide is an example of a preferred external sealing material. From the disclosures made herein, a skilled person will identify other suitable sealing materials. 
     The previous descriptions of the disclosed embodiments is provided to enable any person skilled in the art to make or use the inventive subject matter. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the inventive subject matter. Thus, the inventive subject matter is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
     Although the invention has been described with reference to several exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in all its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent technologies, structures, methods and uses such as are within the scope of the appended claims.