System for measurement and analysis of mooring line conditions

Abstract

A system for measurement and analysis of mooring line conditions has a mooring line link with a single piece main body, the main body having multiple cavities. The cavities may be machined cavities. The cavities may contain a strain sensor element, a pressure sensor, an electronics assembly, and a battery assembly providing electric power to the electronics assembly. A cover over the cavities seals the cavities from water intrusion, and has an access port for electrical connection and data transfer.

Description

[0001] System for Measurement and Analysis of Mooring Line Conditions

[0002] Cross reference to related applications

[0003] This United States non-provisional patent application claims priority to and benefit of United States provisional patent application SN 63 / 636751, filed April 20, 2024, for all purposes. That provisional patent application is incorporated herein by reference, to the extent not inconsistent with this application.

[0004] Background - field of the invention

[0005] This invention relates to systems, including apparatus and methods, used in connection with mooring of floating structures in offshore and marine environments.

[0006] Summary of the Invention

[0007] The system, comprising apparatus and associated methods of use of the apparatus and processing of data gathered, comprises a mooring line link adapted to be incorporated into a mooring line assembly, such as that used to moor floating structures in an offshore environment. The mooring line link comprises multiple data acquisition and storage elements, including but not limited to strain gauges, a pressure sensor, an inclinometer or tilt sensor, time measurement to enable coordination of all data, and a temperature sensor, measuring and recording temperature, enabling calculation and correction of other sensor measurements.

[0008] The mooring line link has a main body which is preferably a single piece steel forging or casting. The particular size and shape of the main body may vary depending on tensile loads, measurement range and the types of physical connections made with the mooring line. Cavities, which may be as-cast, as-forged, or machined cavities, are fabricated and finished in the main body to accommodate particular sensors and assemblies incorporating electronics and batteries. Shapes and relative sizes may vary widely to accommodate multiple link body configurations, regulatory requirements, sensor types, and various pressure case dimensions.

[0009] The cavities are covered by sealed covers, preferably with access ports for electrical connections to facilitate pre-deployment configuration, calibrations, and maintenance.

[0010] Fabrication of the mooring line link in this manner results in an apparatus capable of withstanding high tension and shock loads and general rugged treatment, permitting its incorporation into a mooring line assembly, handling from service vessels, passage over stem rollers, etc. without damage.

[0011] The measured data is stored in digital media storage carried in the mooring line link.

[0012] The system comprises digital processors and software which permit tracking of global stationkeeping performance, as well as tracking of accumulated damage and / or failed components for mooring lines, risers and umbilicals. Further, the system utilizes the mooring line link to capture nonlinearities that only direct line tension measurement can capture (i.e. nonlinear EA (elastic stiffness, namely elastic modulus x cross section area) properties of fiber ropes, drag anchor movements, etc.). The system may comprise multiple measurement capabilities as hereafter described.

[0013] Brief description of the drawings

[0014] Fig. 1 is a general environmental view of the mooring line link forming a component of the overall system, in place in a mooring line assembly connecting a floating structure to an anchor.

[0015] Fig. 2 is a diagram of the mooring line link in a mooring line assembly, illustrating direction of tensile load and angle of deployment of the mooring line link. Figs. 3 - 5 are top, side, and isometric views of one embodiment of the mooring line link. Fig. 5A is a schematic illustrating certain aspects of one embodiment of the system.

[0016] Fig. 6 is a schematic of an exemplary, general layout of the mooring line link body and arrangement of the principal functional elements incorporated therein.

[0017] Fig. 7 is an internal cross sectional view of an as-cast, as-forged, or machined cavity within the mooring line link body, containing resistive strain sensing elements.

[0018] Fig. 8 is a schematic of a functional block diagram showing the electrical wiring and cables connecting the sensors, electronics unit, and battery.

[0019] Description of the presently preferred embodiment(s)

[0020] Fig. 1 illustrates an exemplary placement of the mooring line link 100 in a mooring line assembly. A mooring line assembly (only a single one shown for illustration) connects a floating structure to an anchor, typically in an ocean or marine setting. As is known in the art, the mooring line assembly, and consequently mooring line link 100 is subjected to tensile loads, and will move into different angular positions, as well as global positions, as forces on the floating structure change. The mooring line assembly may comprise combinations of flexible members (steel or synthetic cables) and chain.

[0021] Fig. 2 is a diagram of mooring line link 100 in a mooring line assembly, including main body 10, illustrating direction of tensile load and angle of deployment of the mooring line link. As noted above, as forces on the floating structure change, the angle of the position of mooring line link 100 will change. Tensile loads also change. Further, movement of the mooring line assembly in both the vertical and horizontal planes, and other planes, necessarily results in movement of mooring line link 100. Other conditions of mooring line link 100 may include depth (as noted in Fig. 1), and angle of mooring line link 100 within the mooring line assembly, with respect to a datum, as noted in Fig. 2.

[0022] The apparatus embodying the principles of the present invention may comprise a combination of sensors, data storage media, and data transmitters for direct and indirect monitoring of tension in mooring lines, umbilicals, and risers. One such sensor in the system is mooring line link 100, inserted into the mooring line assembly, as noted in Fig. 1.

[0023] Figs. 3 - 5 are top, side, and isometric views of one embodiment of mooring line link 100.

[0024] Fig. 5 A is a schematic showing the general components of mooring line link 100 with its internal components and capabilities.

[0025] Further detail of mooring line link 100 may be described with reference to Figs. 6 — 8.

[0026] Fig. 6 depicts a general, exemplary layout of mooring line link main body 10, and arrangement of the principal functional elements incorporated within an exemplary embodiment.

[0027] Mooring line link main body 10, in a preferred embodiment, is a single piece forged or cast steel (or other suitable material) unit of appropriate size and shape as required for direct connection to existing proprietary and / or commercial mooring line components and accessories. The forging or casting is machined and finished to accommodate additional elements as described herein. Material type (steel alloy), overall size, and shape may vary with loading and measurements determined by specific (local) regulations, operating conditions, and standards of safety.

[0028] A plurality of cavities within mooring line link main body 10 are fabricated and finished to accommodate particular sensors and assemblies incorporating electronics and batteries. The cavities may be machined or formed in other manners known in the art. Shapes and relative sizes indicated are typical and may vary widely to accommodate multiple link body configurations, regulatory requirements, sensor types, and various pressure case dimensions.

[0029] A properly sealed cover or covers 110, preferably with an access port for electrical connections to facilitate pre-deployment configuration, calibrations, and maintenance, is provided over the cavities. Exemplary covers are shown in Figures 3, 4, and 5 which also depict an exemplary mooring line link body 10.

[0030] With continued reference to Fig. 6:

[0031] Cavity 11 in mooring line link main body 10 is of a size and shape determined by practices known in the art, including advanced simulations and analysis, for fixing and securing multiple resistive strain sensor elements (element 15, described in more detail below) and for incorporating sensitive electronic circuits (amplifier) in close proximity thereto. Multiple such cavities may be incorporated into the link body at appropriate locations as determined by advanced simulation and analysis methods. Fig. 6 shows two cavities 11.

[0032] Cavity 12 in mooring line link main body 10 is of a size and shape determined by practices known in the art, including but not limited to advanced simulations and analysis, for fixing and securing a proprietary and / or commercial pressure sensor (element 16, described in more detail below). The size and shape of cavity 12 may also be determined to incorporate an oil filled chamber with an appropriate flexible element for coupling external hydrostatic pressure to the sensitive surface of a commercial sensor.

[0033] Cavity 13 in mooring line link main body 10 may be provided for installing and securing an electronics assembly (element 17, described in more detail below) incorporating a depth rated pressure case with suitable electrical connectors.

[0034] Cavity 14 in mooring line link main body 10 may be provided for installing and securing a battery assembly (element 18, described in more detail below) incorporating a depth rated pressure case with suitable electrical connectors.

[0035] Fig. 7 is a cross section of main body 10, and shows an internal cross sectional view of cavity 11 containing typical resistive strain sensing elements 15. The typical resistance bridge circuits are fixed with adhesive to the bottom surface of the cavity with electrical wiring connecting directly to the input of an electronic amplifier assembly. An electrical connector is fixed to a cover plate 110 with electrical wiring connecting directly to the output of the electronic amplifier. It is understood that resistive strain sensing elements 15 are adapted to measure tensile loads on said main body 10.

[0036] The electrical connector also provides external power from the electronics unit for the amplifier and excitation voltage for the strain sensing elements.

[0037] Resistive strain sensing elements 15 may take various forms, but one preferred embodiment comprises multiple Wheatstone bridge circuits fixed directly to an appropriately finished inside surface of cavity 11 and directionally aligned with tensile loads applied to the link body when installed in a mooring line.

[0038] Fig. 8 is a functional block diagram showing the electrical wiring and cables connecting the sensors 15, 16, electronics unit 17, and battery 18. Specific values for the operating ranges of the sensors may vary widely in actual practice.

[0039] Removable storage media indicated for recorded data are two identical commercial SD card devices but may vary in actual practice. The microcomputer and embedded software accommodate multiple proprietary or commercial device types and data formats.

[0040] With more detail, in reference to Fig. 8:

[0041] Pressure sensing element 16 may comprise a stainless steel pressure case, resistive or ceramic sensor, and depth rated electrical connector and wiring. The sensor is fixed within cavity 12. The maximum or full scale measurement range of the sensor may vary and is determined by specific (local) regulations and operating conditions. It is understood that pressure sensing element 16 is adapted to measure pressure on main body 10.

[0042] Electronics assembly 17, preferably comprising a depth rated pressure case, electrical connectors and wiring, is fixed and secured within cavity 13 and aligned to ensure proper three axis tilt measurements with respect to the principal axis of mooring line link main body 10. Electronics assembly 17 preferably incorporates the following functional units inside the pressure case, which are represented schematically in Fig. 8:

[0043] 17a Three axis tilt sensor - measures orientation and relative position of the link body and its principal axis.

[0044] 17b Temperature sensor - measures link body temperature and may be used to calculate or correct measurements from other sensors.

[0045] 17c Electronic amplifiers and signal conditioning circuitry implement best practice signal to noise characteristic, and scaling of output signals received from resistive strain sensing elements.

[0046] 17d Analog to digital signal conversion circuitry transforms conditioned signals received from resistive strain sensing elements and other sensors into high resolution digital representations at a controlled predetermined sample rate. 17 e A precision voltage reference provides required basis signals for accurate excitation of the resistive strain sensing elements (Wheatstone bridge circuits) and for accurate analog to digital signal conversion.

[0047] 17f A precision timing reference provides accurate sample rates and proper sequence of sampling (time tag) for data recorded from the various sensors.

[0048] 17g A microcomputer with embedded software controls the autonomous real time measurement and recording processes required to record sensor data onto the removable storage media. The microcomputer is also capable of external connections that may be required for configuration for specific deployments or operating environments, specific activities related to calibration of the strain sensors, uploading or downloading data including embedded software, and / or other essential or non-essential functions.

[0049] 17h Battery voltage regulator and power control (power management) circuitry implements conversion and control of all internally required voltages as required to ensure best practice signal to noise performance and stability over the full operating range of the selected battery type. Additional controls are implemented to insure efficient switching of internal power at appropriate points within the internal circuitry and at appropriate times so as to maximize battery life and extend the duration of field deployments.

[0050] 17i Multiple removable storage media devices are incorporated for indefinite retention of sensor data. Commercial SD card media may be used, however, multiple commercial data formats and media types are accommodated by the microcomputer and embedded software.

[0051] A battery assembly 18, preferably comprising a depth rated pressure case, electrical connectors and wiring, is fixed and secured within cavity 14. Battery assembly 18 may comprise any suitable type of battery, by way of example a lithium battery, either rechargeable or non-rechargeable. Battery assembly 18 preferably incorporates the following functional units inside the pressure case, which are represented schematically in Fig. 8:

[0052] 18a Multiple individual cells of a specified rechargeable or non-rechargeable type.

[0053] 18b Electronic support circuitry required to ensure safety for all battery types.

[0054] 18c Charge control circuitry for rechargeable battery types.

[0055] As noted, in the preferred embodiment mooring line link 100 may comprise multiple data acquisition and storage elements. For example, mooring line link 100 may comprise:

[0056] - a plurality, for example four, strain gauges which permit tensile load measurement (calculation) and storage of that data; the strain gauges may be redundant and independent of one another

[0057] - a pressure sensor, measuring and recording hydrostatic pressure, enabling calculation of depth of the link

[0058] - inclinometer or tilt sensor, measuring and recording angle of link 10 within the mooring line assembly with respect to a datum

[0059] - time measurement to enable coordination of all data

[0060] - a temperature sensor, measuring and recording temperature, enabling calculation and correction of other sensor measurements The measured data may be stored in digital media storage carried in the link, and / or transmitted via acoustic and / or radio signal or hard wired connection.

[0061] The stored data (strain gauge, pressure sensor, inclinometer, time, and any other data) may be downloaded upon retrieval of mooring line link 100 after some period of deployment and link 10 is retrieved to the surface.

[0062] One important attribute of mooring line link 100 is that tensile loads may be both directly measured and indirectly measured, through sensors such as depth and inclination gauges, and then calculated. For example, directly measured tensile loads from some of the strain gauges may be checked against calculated tensile loads through a combination of catenary calculations and the line angle or link depth.

[0063] Various methods of analyzing and utilizing the data, post deployment of the apparatus, can be employed. The data tracks the tensile load history of the various elements of the mooring line assembly. The data also tracks measurements of other sensors. From the load history and sensor measurements, accumulated fatigue life, and potential fatigue damage, can be estimated. Such data can assist in determining whether equipment is still serviceable, or must be repaired.

[0064] Reports usable by regulatory and other bodies may be generated by analysis and processing of the acquired data.

[0065] Data may be recovered and post processed or transmitted directly to another location for processing and analysis. It is understood that the system comprises digital processors and accompanying software, as necessary, to carry out such tasks.

[0066] Further, embodiments of the system may comprise multiple mooring line links, apparatus for interaction (e.g. data retrieval, battery recharging, etc.) with remotely operated vehicles, and cable connections to elements on the floating structure and / or sea floor.

[0067] Conclusion

[0068] While the preceding description contains many specificities, it is to be understood that same are presented only to describe some of the presently preferred embodiments of the invention, and not by way of limitation. Changes can be made to various aspects of the invention, without departing from the scope thereof.

[0069] Therefore, the scope of the invention is to be determined not by the illustrative examples set forth above, but by the appended claims and their legal equivalents.

Claims

We claim:

1. A system for mooring line assembly monitoring, comprising: a mooring line link adapted for placement within a mooring line assembly, said mooring line link comprising: a main body comprising a plurality of cavities therein, each of said cavities comprising a sealed cover; a plurality of strain gauges permitting tensile load measurement (calculation) and storage of said measurements; a pressure sensor adapted to measure and record hydrostatic pressure; an inclinometer or tilt sensor, measuring and recording an angle of said mooring line link within said mooring line assembly with respect to a datum; a time measurement system; a temperature sensor; wherein the measured tensile, pressure, inclination, time, and temperature data is stored in digital media storage carried in the link; and a digital processor and accompanying software enabling calculations using said measured data.

2. A mooring line link, comprising: a single piece main body comprising a plurality of cavities therein, said cavities comprising: a strain sensor element, adapted to measure tension on said main body; a pressure sensor, adapted to measure pressure on said main body;an electronics assembly, adapted to receive and process data from said strain sensor and said pressure sensor; a battery assembly providing electric power to said electronics assembly; and a cover over said cavities, said cover sealing said cavities from water intrusion therein, said cover comprising an access port for electrical connection thereto.

3. The mooring link of claim 2, wherein: said strain sensor element comprises multiple strain sensor elements, and said pressure sensor comprises an oil filled chamber and flexible element coupling hydrostatic pressure to said pressure sensor.

4. The mooring line link of claim 3, wherein: said strain sensor comprises multiple Wheatstone bridge circuits fixed to an inner surface of said cavity containing said strain sensor, and directionally aligned with tensile loads applied to said mooring line link.

5. The mooring line link of claim 4, wherein said electronics assembly comprises: a three axis tilt sensor; a temperature sensor; electronic amplifiers and signal conditioning circuitry; analog to digital conversion circuitry; a precision voltage reference; a precision timing reference; a digital processor or microcomputer;batery voltage regulation and power control circuitry; and a removable storage media device.

6. The mooring line link of claim 2, wherein said electronics assembly comprises: a three axis tilt sensor; a temperature sensor; electronic amplifiers and signal conditioning circuitry; analog to digital conversion circuitry; a precision voltage reference; a precision timing reference; a digital processor or microcomputer; batery voltage regulation and power control circuitry; and a removable storage media device.

7. The mooring line link of claim 2, wherein said battery assembly comprises: multiple individual cells; electronic support circuitry; and charge control circuitry.

8. A mooring line link, comprising: a single piece main body comprising a plurality of cavities therein, said cavities comprising: a strain sensor element, adapted to measure tension on said main body, said strain sensor element comprising multiple Wheatstone bridge circuits fixed to an inner surface of said cavity containing said strain sensor, and directionally aligned with tensile loads applied to said mooring line link;a pressure sensor, adapted to measure pressure on said main body and comprising an oil filled chamber and flexible element coupling hydrostatic pressure to said pressure sensor; an electronics assembly, comprising: a three axis tilt sensor; a temperature sensor; electronic amplifiers and signal conditioning circuitry; analog to digital conversion circuitry; a precision voltage reference; a precision timing reference; a digital processor or microcomputer; battery voltage regulation and power control circuitry; and a removable storage media device;; a battery assembly providing electric power to said electronics assembly, comprising multiple individual cells, electronic support circuitry, and charge control circuitry; and a cover over said cavities, said cover sealing said cavities from water intrusion therein, said cover comprising an access port for electrical connection thereto.

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