System for direct sensing of mooring lines and installation and calibration method for direct sensing of mooring line

Abstract

System based on the installation of extensometers (1), equipped with means to compensate for temperature variations, in the first link (4) under mooring tension of the FPSO, configured in rosette (2), connected through optical fiber (3), measuring the tension on the axes for three-dimensional deformation analysis, and sensors can further be installed in more than one link (4') loaded from the mooring, and in links not subjected to load, complemented with inertial units and / or accelerometers to create advanced mathematical models for integration with digital twins (digital twin). The installation method observes the alignment of the sensors with the main generators of the loading, and with the surface of the link where it is installed, and can occur with the loaded link, to measure the variations in tension from previous loading; with temporary relief of the load on the link, to measure the tension of the assembly from zero loading, or in the factory or assembly yard, before the release of the moorings, for absolute measurement of the tension, whereby during periodic recalibration possible offsets and / or drifts can be identified in the fixing of the sensors.

Description

“SYSTEM FOR DIRECT SENSING OF MOORING LINES AND INSTALLATION AND CALIBRATION METHOD FOR DIRECT SENSING OF MOORING LINES”FIELD OF APPLICATION

[0001] This specification is related to a patent of invention of a system for direct sensing of stresses in mooring lines, and an installation and calibration method for direct sensing of stresses in mooring lines, correlated with FPSO movements (Floating Production, Storage, and Offloading), which can be adapted to other analogous applications.SUMMARY OF THE INVENTION

[0002] The FPSO's operating scenario involves extreme maritime environments, continuously subject to humidity and environmental forces, such as waves, currents, and winds.

[0003] These factors cause constant movements and repetitive loading and unloading cycles on the mooring lines that secure the vessel to the ocean floor.

[0004] The ties that make up these lines are typically formed by steel links that undergo repeated stresses, which leads to the fatigue phenomenon, which is a progressive and localized process of structural damage, and which accumulates over time, and can culminate in catastrophic failures.

[0005] Monitoring the loads on the FPSO's moorings is important to ensure the integrity of the anchorage throughout the unit's useful life, since the anchorage is fundamental to maintaining the stable position of the FPSO, avoiding displacements that could compromise the safety of the risers, which connect the platform to the ocean floor for oil and gas transportation.

[0006] Failure of a mooring link due to fatigue can lead to the rupture of an anchor line, which not only increases the load on the remaining lines, but also increases the risk of cascading failure.

[0007] In extreme cases, multiple failures in the anchor lines can lead to a loss of FPSO positioning, resulting in production interruption and, in some cases, severe environmental damage due to riser rupture and hydrocarbon leakage.

[0008] Continuous monitoring of ties becomes, therefore, essential to identify early signs of wear and fatigue in their links and components.BACKGROUND OF THE TECHNOLOGY

[0009] Modern technology allows the use of tension and angle measurement systems, which capture real-time data on the state of each anchor line.

[0010] These systems assist in detecting load variations that indicate accumulated fatigue, allowing for preventative interventions before a total failure occurs.

[0011] Indirect monitoring techniques correlate the movements of the FPSO with the stresses on the mooring lines and are used to predict and evaluate the condition of the links, without the need for direct instrumentation in the moorings.

[0012] In short, monitoring the conditions of moorings is crucial for risk management and operational safety on platforms and FPSOs, providing data that guides predictive maintenance and ensures the continuity of operations with integrity and safety.

[0013] The current state of the art is already known regarding the development proposed by means of patent document CN104132687, which discloses the use of a wave and current instrument, used to measure the flow direction, velocity, wave height, wave direction, period, and wave spectrum parameters; an anemometer, to obtain wind speed and direction data; an integrated temperature, humidity, and air pressure machine to obtain temperature, humidity, and air pressure parameters; independent GPS systems, arranged along the longitudinal direction of the FPSO, to obtain the orientation of the FPSO; GPS station, base and mobile, installed on the FPSO, to measure the distance between the FPSO and the single-point conductor structure by differential processing using the positioning information between the two; inertial measurement unit (IMU), for measuring the six-degrees-of-freedom motion of the FPSO, where the translation of the FPSO in three directions is measured by the accelerometer in the IMU, and the rotation in three directions is measured by three gyroscopes; fiber Bragg grating deformation sensors to measure the magnitude of the mooring force, and mooring current attitude measurement sensors, to measure the angle of the mooring force, with the fiber Bragg grating deformation sensors and resistive sensors used to measure the torque and deformation of the torque cylinder of the underwater part of the single-point conductor structure; acceleration sensor, to measure the vibration of the single-point coating structure; single-point status monitoring application, which uses all sensors to access the backup channel of the central control system to measure, collect, transmit, display, and process all data.

[0014] The development proposed by means of patent document CN111241740 is also known, which discloses a method to quickly and accurately calculate the tension of a rigid and soft arm of the FPSO, first through the establishment of a numerical finite element model of the FPSO, based on the responses obtained from the time history of movement of a ship body and a soft rigid arm, and the variables that influence the tension of all the mooring legs of the soft rigid arm, and secondly, by an LSTM neural network, built to perform the dynamic response calculation, the determination of the effective accuracy interval of a single LSTM neural network, the verification of the effect of the LSTM neural network calculation under different working conditions, and a complete library of LSTM neural network models built according to thesea working conditions, whereby, finally, the tension of each mooring leg of the soft rigid arm calculated under each environmental load based on the complete library of LSTM neural network models, in order to overcome the difficulty of monitoring for a long period of time the tension of each mooring leg of the soft rigid arm of the FPSO in deep waters, makes it possible for the tension of each mooring leg of the soft rigid arm to be calculated quickly and accurately by means of six degrees of freedom of the FPSO body.BACKGROUND OF THE INVENTION

[0015] The direct stress monitoring system in the mooring lines of this invention is based on the installation of strain gauges (strain gauge), for example, optical Bragg grating sensors, in a specific link, preferably the first loaded link of an FPSO mooring, located in an emerged area and accessible from the deck of the vessel, which receives the tension from the set formed by the remaining links, becoming a point for monitoring fatigue and structural integrity.

[0016] The sensor should preferably be configured in a rosette arrangement, but it can, however, be configured in another topology to measure the tension on the shafts, providing three-dimensional analysis of the deformation of the link.

[0017] The present system also considers the possibility of installing sensors in more links loaded with the mooring, to create a redundant system.

[0018] Additionally, it is also recommended to install sensors in links that are not under load, serving to compare the collected data, to eliminate possible sources of error such as alignment, gluing, and other conditions that may impact the reliability of the signal received from the sensors.

[0019] In addition to the possibility of detecting rupture of the moorings, the system of the present invention can further be complemented with inertial units and / or accelerometers, to collect additional information on the load dynamics, enabling an even more robust analysis of structural fatigue.

[0020] Obtaining tension data on mooring lines also allows the creation of advanced mathematical models and their integration with digital twins (digital twin), from which it is possible to predict the behavior and useful life of the moorings.

[0021] The system proposed herein offers advanced functionalities for link monitoring, among which the following stand out:

[0022] . identification of static and dynamic loads: the technology used is capable of distinguishing between static and dynamic loads, adjusting monitoring according to operational needs and sea conditions;

[0023] . rupture detection: in the event of structural failure of the mooring, the system detects a sudden drop in tension in the monitored link, which indicates the rupture, and allows rapid response in emergency situations;

[0024] Multi-sensor data analysis: the combination of stress, accelerometry, and georeferencing data allows for the improvement of detailed mathematical models and the integration of the system with a digital twin of the FPSO, through which the simulation of wear scenarios and the prediction of the useful life of the components is facilitated, enabling preventive and effective management.

[0025] The installation method of this invention must observe the alignment of the sensors with respect to the main generators of the loading, and must also be correctly aligned with the surface of the link in which it is installed, unless the sensor used allows installation in any orientation.

[0026] The installation method of the present invention can occur directly with the loaded link, without the need for load relief from the same; in other words, the sensors are installed on the mooring link already installed on the vessel, and can thus measure tension variations, positive or negative, from this prior loading point.

[0027] The installation method of the present invention may also occur with the temporary relief of the load on the link to be instrumented; in which condition the sensors are installed and calibrated with the unloaded link, which, after installation, once again receives operational load, allowing the measurement of the assembly tension starting from zero link load in an operational environment.

[0028] The installation method of this invention can also be carried out in the factory or in the assembly yard, before the launch of the moorings, to facilitate access to the link, and must provide for the pre-calibration of the sensor before the installation of the mooring in the field, to perform absolute measurement of the tension.

[0029] During periodic recalibration, possible offsets and / or drifts in the sensor fixation are identified, due to the glue, weld or adhesive used, allowing fine adjustments and deviation corrections over time.

[0030] This invention covers a wide scope of stress and / or fatigue monitoring applications related to anchoring elements, and can be adapted for other types of anchoring on floating units and offshore platforms, and includes the use of different types of sensors, arrangements and varied topologies, including those that do not require alignment, and at different points on the anchor line, to increase the scope of structural monitoring.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] For a better understanding of this system for direct sensing of stresses in anchor lines, reference is made to the attached figures, to characterize its functionality, these being, however, merely illustrative, and may vary, as long as they do not deviate from the functional principle thereof, and where:

[0032] Figure 1 illustrates a schematic view of sensor installation on amooring link, and

[0033] Figure 2 illustrates a schematic view of the sensor installation in two mooring links.PREFERRED DESCRIPTION OF THE INVENTION

[0034] In accordance with what is illustrated in the attached figures, the system for direct sensing of stresses in the anchor lines of the present invention is based on the installation of extensometers (1), duly equipped with means to compensate for possible temperature variations, in a rosette arrangement (2), and connection through optical fiber (3), preferably on the first loaded link (4), supported by a retention lock (5), located in an emerged area and with access from the deck of the vessel, which receives the tension from the set formed by the remaining links, becoming a monitoring point for fatigue and structural integrity, as illustrated in Figure 1 , to measure the tension on the axes for three-dimensional analysis of the deformation of the link.

[0035] The system of this invention further considers the possibility of installing sensors in one more link (4') loaded from the mooring, as illustrated in figure 2, to create a redundant system.

[0036] Additionally, it is also recommended to install sensors in links that are not under load (not illustrated), serving as a comparison of the collected data, to eliminate possible sources of error such as alignment, bonding, and other conditions that may impact the reliability of the signal received from the sensors.

[0037] In addition to the possibility of detecting rupture of the moorings, the system of the present invention can also be complemented with inertial units and / or accelerometers (not illustrated), to collect additional information about load dynamics, enabling even more robust analysis of structural fatigue.

[0038] Obtaining tension data on mooring lines also allows the creation of advanced mathematical models and their integration with digital twins (digital twin), from which it is possible to predict the behavior and useful life of the moorings.

[0039] The installation method of this invention must observe the alignment of the sensors with respect to the main generators of the loading, and must also be correctly aligned with the surface of the link in which it is installed, if such orientation is required.

[0040] The installation method of the present invention can occur directly with the loaded link, without the need for load relief from the same; in other words, the sensors are installed on the mooring link already installed on the vessel, and can thus measure tension variations, positive or negative, from this prior loading point.

[0041] The installation method of the present invention may also occur with the temporary relief of the load on the link to be instrumented; in which condition thesensors are installed and calibrated with the unloaded link, which, after installation, once again receives operational load, allowing the measurement of the assembly tension starting from zero link load in an operational environment.

[0042] The installation method of this invention can also be carried out in the factory or in the assembly yard, before the launch of the moorings, to facilitate access to the link, and must provide for the pre-calibration of the sensor before the installation of the mooring in the field, to perform absolute measurement of the tension.

[0043] During periodic recalibration, possible offsets and / or drifts in the sensor fixation are identified, due to the glue, weld or adhesive used, allowing fine adjustments and deviation corrections over time.

Claims

AMENDED CLAIMSreceived by the International Bureau on 07 MAY 2026 (07.05.2026)1. A SYSTEM FOR DIRECT SENSING OF ANCHOR LINES, comprising extensometers (1) installed in a mooring link, characterized in that said extensometers (1) are configured in rosette (2) of three extensometers oriented at 0s, 45sand 90srelative to the longitudinal axis of the link, installed on the first loaded link (4)) of a mooring line, located in an emerged area accessible from the deck of the vessel, comprising a retention lock (5) for fixing the instrumented link, so as to enable the three-dimensional analysis of link deformation tensor with lower error of 0.2% and MTTR reduction between 50-70%.

2. The SYSTEM according to claim 1 , characterized in that the error of the three-dimensional analysis of the link deformation tensor is less than 0.2%.

3. The SYSTEM according to claim 1 , characterized in that the MMTR reduction is between 50-70%.

4. The SYSTEM according to claim 1 , characterized in that the extensometers (1) are of the FBG (Fiber Bragg Grating) type connected through optical fiber.

5. The SYSTEM according to claim 1 , characterized by comprising a thermal offset module.

6. The SYSTEM according to claim 1 , characterized by comprising sensor redundancy (7) in adjacent loaded and unloaded links.

7. The SYSTEM, according to claim 1 , characterized by comprising inertial sensors (8) for measuring local movement of the link.

8. The SYSTEM according to claim 1 , characterized in that the deformation data are utilized to create a digital twin of the mooring line.

9. The SYSTEM according to claim 1 , characterized in that the three-dimensional analysis of the deformation enables the detection of non-axial fatigue.

10. A METHOD OF INSTALLATION AND CALIBRATION FOR DIRECT SENSING OF MOORING LINES, comprising the step of installing extensometers on a mooring link, characterized by further comprising the steps of:- exact alignment of the extensometers to the main generators of loading and to the surface of the link;- realization of initial calibration on a zero-load baseline link to establish a reference point free of mechanical tensions and to offset thermal and hydrostatic effects, assuring the stability of the data for decades;- synchronization of the time information between the data of the extensometers and the movement data of the FPSO utilizing Precision Time Protocol (PTP) with submillisecond precision, for precise correlation of load transients without time aliasing;- realization of factory pre-calibration of the extensometers, and- realization of periodic recalibration of the system to correct offsets and drifts.

11. The METHOD according to claim 10, characterized in that the installation of the extensometers occurs in the first loaded link of the mooring line, in an emerged area accessible by the deck.

12. The METHOD according to claim 10, characterized in that the initial calibration is realized after the temporary relief of the load on the mooring link.

13. The METHOD according to claim 10, characterized in that the periodic recalibration is triggered by the detection of drifts or by a predefined schedule.

14. The METHOD according to claim 10, characterized in that the PTP synchronization enables the correlation of the deformation data with the 6-DOF movements of the FPSO.

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