Underwater sealing butt joint method of deepwater large-diameter composite pipe rotary flange

Abstract

The application discloses a kind of deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint methods, belong to submarine pipeline engineering technical field.The method is aimed at the problems that traditional flange joint is insufficient in sealing reliability under deepwater dynamic environment and lacks long-term monitoring means, by setting pressure self-adaptive sealing cavity on rotary flange disc surface, the sealing specific pressure is enhanced by internal pressure, and the sealing state is monitored in real time by integrating pressure sensor, and the pressure sensor interface is reserved to realize long-term data acquisition.The method is mainly used for the installation and operation of submarine water, oil and gas pipelines, and can effectively guarantee the long-term sealing safety of pipeline interface.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of submarine pipeline engineering, and particularly relates to a method for underwater sealing butt joint of a deepwater large-diameter composite pipeline rotary flange. BACKGROUND

[0002] In the field of submarine pipeline engineering, especially in cross-sea water supply and gas transmission projects, the structure of a large-diameter steel pipe wrapped with concrete is a common choice. Such a pipeline usually needs to be connected by flanges to be butt jointed and installed underwater on site. Rotary flanges are applied in such projects because they can compensate for certain installation errors.

[0003] However, the traditional flange connection method faces several inherent problems in a deepwater environment. First, the sealing reliability of the flange joint is at risk in the long term. After the underwater pipeline is installed, it will continue to be affected by dynamic factors such as internal water pressure fluctuations, water hammer effect, uneven settlement of the foundation, and sea current load. These factors can cause the pre-tightening force of the flange connection bolts to relax, thereby reducing the compression force of the flange sealing surface. The traditional static sealing design cannot effectively adapt to this long-term changing working condition, which may cause interface leakage and affect the normal operation of the pipeline system.

[0004] Second, there are significant difficulties in monitoring and evaluating the state of the underwater flange joint. Once the pipeline is installed in place and backfilled, the interface is permanently buried under the seabed mud surface, making it difficult to directly observe and access. Currently, there is a lack of economic and effective technical means to continuously monitor the sealing performance of such key interfaces hidden inside the structure in situ, and dynamic data reflecting the compression state of the sealing surface cannot be directly obtained. Its operating state is actually an unknown "black box". Operation and maintenance often rely on regular overall water pressure tests during operation, which is a verification test after the problem may have occurred, and cannot detect potential risks in advance, let alone locate specific fault points.

[0005] The main reason for these problems is the particularity of the underwater environment and the limitations of technology. The high pressure, strong corrosion, low visibility, and poor accessibility of the deepwater environment pose great challenges to the long-term stability of the sealing structure and the implementation of monitoring means. In the past, when trying to solve these problems, the difficulties encountered mainly include: how to integrate a dynamic adaptation mechanism into the sealing structure itself, so that it can respond to pressure changes without significantly changing the standard structure and size of the flange; and how to establish a stable and durable data transmission channel to reliably transmit the signals of the underwater sensor to the water surface monitoring station. The traditional method cannot directly monitor the effective compression force of the sealing surface, and cannot provide direct data support for sealing reliability.

[0006] These difficulties have long restricted the development of underwater pipeline interface technology reliability and operation level, making many important submarine pipeline projects face potential risks in long-term safe operation. SUMMARY

[0007] The application provides a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method, aiming to solve the comprehensive technical problems that the interface sealing reliability is insufficient when the large-diameter composite pipeline adopts rotary flange butt joint in a deepwater environment, and there is a lack of effective means to monitor the sealing state of the underwater joint for a long time, because the traditional static sealing cannot adapt to long-term water pressure fluctuation, bolt stress relaxation and foundation settlement.

[0008] The technical problem of solving the key components such as sensor probe and connector is that they are easily attached and covered by marine organisms in the marine environment, and are corroded by seawater, which leads to rapid degradation or permanent damage of their functions.

[0009] The technical problem of solving the electrode of the electrolytic antifouling circuit is that the electrode is continuously consumed due to electrochemical corrosion during the electrolysis process, which leads to the decay of the antifouling effect over time, and frequent replacement or maintenance is required.

[0010] The technical problem of solving the underwater connector of the monitoring system is that due to plug-in wear, marine organism corrosion, cable pulling and other reasons, there is a risk of unreliable connection, signal interruption and sealing failure.

[0011] The technical problem of solving the wet plug-in connector is that a small misalignment may occur at the moment of final butt joint due to underwater flow field disturbance or ROV operation deviation, which may cause the pin of the plug-in core to bend and damage, resulting in connection failure.

[0012] The technical problem of solving the large amount of monitoring data collected is that it can only reflect the real-time state, and cannot effectively identify potential fault modes, predict the degradation trend of sealing performance, and support preventive maintenance decisions.

[0013] In order to achieve the purposes and other advantages according to the application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, comprising the following steps:

[0014] Step one, preparation of prefabricated pipe section and intelligent flange: welding rotary flanges at both ends of the prefabricated pipe section; the butt joint disc surface of the rotary flange is pre-processed with an annular pressure self-adaptive sealing cavity, which is communicated with the inner cavity of the prefabricated pipe section through a pre-embedded micro one-way valve; the bolt hole of the rotary flange is equipped with a double-headed stud, and the pressure self-adaptive sealing cavity is reserved with a pressure sensor interface;

[0015] Step two, end sealing and inspection of prefabricated pipe section: installing a plugging water bag at the butt joint end of the prefabricated pipe section and a blind plate at the other end, and performing air tightness test;

[0016] Step three, positioning and support system layout: use positioning pile and support water bag to assist the underwater positioning of prefabricated pipe section;

[0017] Step four, underwater pull and intelligent fastening of prefabricated pipe section: align the rotating flanges of two prefabricated pipe sections by pulling them together with a hand-operated hoist; use hydraulic stretching equipment to simultaneously stretch the stud bolts, ensuring that the pre-tightening force is evenly reached to the set value;

[0018] Step five, activation and pressure test of pressure adaptive sealing system: after fastening, water is injected into the underwater pipeline composed of multiple prefabricated pipe sections to pressurize; the internal pressure water enters the pressure adaptive sealing cavity through a miniature one-way valve to establish back pressure; perform a staged water pressure test to check the sealing performance of the rotating flange joint;

[0019] Step six, joint wrapping with concrete and integration of monitoring system: bind steel bars, install formwork, and pour concrete at the rotating flange joint; introduce the signal line of the pressure sensor into the embedded conduit and connect it to the permanent underwater connector;

[0020] Step seven, system handover and long-term monitoring: after the pipeline system is put into use, connect the permanent underwater connector through an underwater robot to collect and monitor the pressure data of the pressure adaptive sealing cavity of the rotating flange joint for a long period.

[0021] Preferably, in the deepwater large-diameter composite pipeline rotating flange underwater sealing butt joint method of the present application, the pressure sensor interface of the pressure adaptive sealing cavity is connected to a built-in self-checking circuit of the pressure sensor, which can periodically stimulate the pressure sensor to generate a standard signal to verify the integrity of its measurement channel and achieve on-site calibration through a built-in reference pressure source; all sensor data transmission is encoded using Hamming code error checking and correction algorithm to ensure data integrity during transmission.

[0022] Preferably, in the deepwater large-diameter composite pipeline rotating flange underwater sealing butt joint method of the present application, the plug surface of the permanent underwater connector is prepared with a sharkskin rib-shaped microstructure with a width of 50 microns using laser etching process to inhibit marine larvae attachment, and a low-power pulse electrolytic antifouling circuit with platinum-iridium alloy electrodes is integrated in its shell, which releases a pulse current with a duration of 10 milliseconds every 6 hours; the pressure sensor interface of the pressure adaptive sealing cavity is connected to the pressure sensor through a pressure-resistant stainless steel cabin filled with silicone oil, which completely isolates seawater corrosion while transmitting pressure.

[0023] Preferably, in the underwater sealing butt joint method of the deepwater large-diameter composite pipeline rotary flange of the application, the electrode system of the low-power pulse electrolytic anti-fouling circuit is composed of a platinum-iridium alloy cathode and a magnesium alloy sacrificial anode; the cathode is connected to the negative pole of the pulse power supply, and the sacrificial anode is connected to the positive pole of the pulse power supply; the circuit is integrated with a current monitoring module and a voltage regulation module, the current monitoring module measures the electrolysis loop current value I actual in real time actual , the voltage regulation module compares I set with the preset current threshold I out , and based on the deviation value, dynamically adjusts the output voltage V actual of the pulse power supply through a closed-loop feedback control algorithm, so that I set is stabilized at I x .

[0024] Preferably, in the underwater sealing butt joint method of the deepwater large-diameter composite pipeline rotary flange of the application, in step six, the permanent underwater connector is a wet-plug multi-core conductive connector, the plug-in core is made of gold-plated beryllium copper material, and the plug-in cavity is pre-filled with seawater corrosion-resistant fluorinated ether inert grease; the permanent underwater connector is externally sleeved with a stainless steel mechanical guide funnel device with three-stage guide taper; the stress release structure is formed by using double hoop fixing method at the end of the permanent underwater connector, in which the inner hoop fixes the cable armor layer, and the outer hoop fixes the cable outer sheath.

[0025] Preferably, in the underwater sealing butt joint method of the deepwater large-diameter composite pipeline rotary flange of the application, the male connector of the wet-plug multi-core conductive connector is installed inside its shell through a passive self-adaptive alignment mechanism; the passive self-adaptive alignment mechanism is composed of a spherical universal joint providing two degrees of rotational freedom and three flexible hinges providing degrees of translational freedom; the center point O of the universal joint coincides with the theoretical plug-in center of the male connector; in the initial position, the spatial position of the male connector is constrained by a set of pre-compressed silicone rubber damping elements, and the activity ranges of its translational freedom δ x ,δ y and rotational freedom θ x ,θ y around the X and Y axes are not less than 2mm and 2° respectively.

[0026] When the lateral contact force F generated during the plug-in process is greater than the pre-pressure F pre of the damping element, the male connector will produce displacement d, the displacement direction is the same as the contact force direction, and the displacement size is proportional to the contact force size, the relationship satisfies d=k×(F−F pre ), wherein k is the flexibility coefficient of the flexible hinge; the adaptive motion enables the male connector to compensate for the final butt joint deviation.

[0027] Preferably, in the underwater sealing butt joint method of the deepwater large-diameter composite pipeline rotary flange of the application, in step seven, the long-term acquisition and monitoring is realized based on a machine learning model, the model takes the pressure self-adaptive sealing cavity pressure data and the pipeline internal pressure, flow operation parameters as input features, and the health state score of the sealing system is calculated through a trained deep neural network model; the sealing system can automatically identify the slow degradation trend of the sealing performance, generate a graded early warning signal when the health score is lower than the preset threshold, and output specific maintenance decision suggestions, including maintenance urgency level.

[0028] The present application at least includes the following beneficial effects:

[0029] 1、The method of the present application improves the sealing reliability and safety of the interface under long-term dynamic load by setting a pressure self-adaptive sealing cavity and integrating a long-term monitoring system. The pressure self-adaptive sealing cavity uses the internal pressure of the pipeline as a power source and automatically increases the sealing specific pressure when the internal pressure rises. This dynamic sealing mechanism effectively compensates for the loss of sealing surface pressure caused by bolt stress relaxation, pipeline settlement or water hammer effect, thereby significantly improving the sealing reliability and safety of the interface under long-term dynamic load. The integrated pressure sensor interface establishes a monitoring nervous system for the joint, making real-time, remote and online monitoring of the state of the pressure self-adaptive sealing cavity possible, and transforming the interface from an invisible black box to a perceptible transparent system, providing a solid data foundation for evaluating its health state and developing maintenance strategies, and realizing the transition from passive maintenance to active prevention.

[0030] 2、The method of the present application greatly improves the robustness and data reliability of the monitoring system by using an advanced data verification mechanism. The built-in self-checking and self-calibration circuit can automatically verify the integrity of the sensor measurement channel regularly, and can be traced back to the standard pressure source on site, eliminating measurement errors caused by sensor drift or damage, and ensuring the long-term accuracy of the data. Using Hamming code for data transmission can automatically detect and correct single-bit errors generated during transmission, and can detect multiple-bit errors, fundamentally avoiding the problem of data distortion caused by signal interference or attenuation, and providing highly reliable data protection for subsequent data analysis and decision-making.

[0031] 3、The method of the present application provides long-term effective protection for underwater sensors by adopting a dual protection strategy combining biomimetic microstructure antifouling and electrolytic antifouling. The sharkskin rib microstructure changes the surface properties through physical means, greatly increasing the difficulty of attachment of marine larvae and reducing fouling from the source. The low-power pulsed electrolytic antifouling technology generates a small amount of sodium hypochlorite and other bactericidal substances around the electrode, further inhibiting the formation of microbial membranes. The two work together to achieve efficient and environmentally friendly antifouling results. Encapsulating the sensor interface in a pressure-resistant oil-filled cabin is a complete physical isolation method that completely isolates the core sensitive components from the corrosive seawater environment, avoiding chemical corrosion and pressure penetration problems. This combined method significantly extends the service life and reliability of the sensor interface in harsh marine environments, reducing maintenance frequency and cost.

[0032] 4、The method of the present application ingeniously solves the core contradiction of electrolytic electrode wear by introducing a sacrificial anode and intelligent control circuit. The use of expensive platinum-iridium alloy as the cathode makes it almost not wear during electrolysis, while the wear is transferred to the low-cost, replaceable magnesium alloy sacrificial anode. This design simplifies maintenance operations from replacing the entire expensive electrode to replacing standardized anode blocks, significantly reducing the maintenance cost throughout the life cycle. The current monitoring and voltage regulation module forms a closed-loop control system that can sense changes in electrolytic current in real time and maintain the set current value by automatically adjusting the output voltage, ensuring the stability and consistency of the antifouling effect under different water conductivity and anode consumption levels, and ensuring long-term reliable antifouling performance.

[0033] 5、The method of the present application ensures the long-term connection reliability and physical security of the data channel of the monitoring system by using wet plug connectors and double stress release structures. Wet plug technology and inert grease filling ensure the electrical continuity and sealing of the connector when it is directly plugged underwater, avoiding the inconvenience of draining operations required by traditional connection methods. The double-jacket stress release structure scientifically disperses the pulling force of the cable. The inner jacket fixes the tensile armored layer, and the outer jacket protects the waterproof sheath layer. This design effectively prevents the joint from loosening, signal interruption or seal damage caused by the direct transmission of external pulling force to the internal fragile electrical connection point, greatly improving the durability and reliability of the connector in dynamic marine environments, and providing a solid physical foundation for long-term stable data transmission.

[0034] 6、The method of the present application uses a passive self-adaptive alignment mechanism, which transforms the extremely high precision required for docking from relying on external operations to being absorbed by the internal mechanical structure. The mechanism composed of universal joints and flexible hinges allows the male connector to make slight translations and deflections within a certain range. When there is a slight deviation in docking, the contact force will automatically adjust the connector to the centered position, thereby eliminating the lateral force at the moment of insertion and achieving true "zero damage" blind insertion. This design significantly reduces the stringent requirements for the operation precision of underwater robots, improves the success rate and efficiency of insertion operations, avoids the damage of expensive connectors caused by repeated attempts to insert or insertion deviation, and improves the engineering practicability and economy of the entire system.

[0035] 7、The method of the present application uses a health prediction model based on machine learning, which upgrades the monitoring data from simple status display to predictive decision support. The model can learn the normal operation mode from massive historical data and sensitively identify the small abnormal trend indicating performance degradation, thereby issuing an early warning long before the sealing performance substantially decreases or failure occurs. Instead of outputting disordered data, it outputs analyzed health scores, specific fault location and maintenance suggestions, enabling maintenance personnel to change from "after-the-fact remediation" to "pre-emptive prevention" and plan maintenance window periods with pertinence, effectively avoiding unplanned downtime, greatly improving the safety and economy of pipeline operation, and fully exploiting the potential value of long-term monitoring data.

[0036] Other advantages, objects, and features of the present application will be apparent to those skilled in the art from the following specification. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below, so that those skilled in the art can implement it according to the description.

[0038] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0039] According to one embodiment of the present application, a method for underwater sealing and butt joint of deepwater large-diameter composite pipeline rotary flange is provided. The first step of the method is to prepare the prefabricated pipe section and the intelligent flange. The rotary flange welded at both ends of the prefabricated pipe section can be a forged steel flange conforming to ASTM A105 standard. A rectangular cross-section annular pressure self-adaptive sealing cavity is machined on the butt joint disc surface of the rotary flange. The width of the pressure self-adaptive sealing cavity can be set to 8 mm, and the depth can be set to 5 mm. The pressure self-adaptive sealing cavity is connected to the inner cavity of the prefabricated pipe section through a micro one-way valve. The micro one-way valve can be a titanium alloy micro one-way valve with an opening pressure of 0.1 MPa, which is installed in the drilled hole on the side surface of the rotary flange by screw connection. A double-headed stud is provided in the bolt hole of the rotary flange. The double-headed stud can be made of 42CrMo alloy steel, and both ends are machined with threads conforming to ISO 4014 standard. The pressure sensor interface reserved for the pressure self-adaptive sealing cavity can be designed as a 1 / 4NPT internal thread hole for installing a pressure sensor.

[0040] The second step is to seal and inspect the end of the prefabricated pipe section. A plugging water bag is installed on the underwater butt joint end of the prefabricated pipe section, i.e., the end planned to be connected to the installed prefabricated pipe section. The water bag can be a cylindrical air bag made of butyl rubber with a nominal diameter slightly smaller than the pipe inner diameter. During installation, compressed air is filled into the air bag through an inflation device to a working pressure of 0.5 MPa. A blind plate is installed on the other end of the prefabricated pipe section opposite the butt joint end. The blind plate can be a ribbed circular plate made of Q235B steel with a thickness of 30 mm, which is fastened by ISO 4014 grade 10.9 bolts. The air tightness test is performed using compressed air. The internal pressure of the prefabricated pipe section is increased to 0.6 MPa and maintained for 30 minutes. If the pressure drop is not more than 5%, it is considered qualified.

[0041] The third step is to lay out the positioning and support system. The positioning pile can be a C45 reinforced concrete prefabricated structure with a cross-sectional size of 2.5 meters by 2.5 meters, a height of 2.5 meters, and a weight of about 22.5 tons. The support water bag can be the same size as the plugging water bag. Four support water bags are arranged for each prefabricated pipe section symmetrically along the prefabricated pipe section axis. The positioning pile and support water bags are lifted to the designed position using a crane ship during the layout, and the installation accuracy is ensured by underwater adjustment by divers.

[0042] The fourth step is to underwater pull together and intelligent fasten the prefabricated pipe section. The rotary flanges of the two prefabricated pipe sections are pulled together using a hand-operated hoist to align the rotary flange discs, with a disc surface gap controlled within 2 mm. The double-headed studs are simultaneously stretched using a hydraulic stretching device. The pre-tightening force control target can be set to 70% of the yield strength of the bolt material to ensure uniform distribution of the pre-tightening force.

[0043] The fifth step is the pressure self-adaptive sealing system activation and pressure test. After the fastening is completed, water is injected into the pipeline that has been connected by multiple prefabricated pipe sections underwater, and a plunger pump is used to gradually increase the internal pressure of the pipeline to the working pressure of 1.5 MPa. The internal pressure water enters the pressure self-adaptive sealing cavity through a micro one-way valve, and when the pressure in the cavity reaches 0.1 MPa, the micro one-way valve opens to establish back pressure. The staged water pressure test is carried out, first pressurized to 0.75 MPa, pressure maintained for 15 minutes, then pressurized to 1.5 MPa, pressure maintained for 30 minutes, and finally pressurized to 2.5 MPa, pressure maintained for 24 hours.

[0044] The sixth step is the joint outer concrete and monitoring system integration. Steel reinforcement can be selected at the rotary flange joint, with HRB400 threaded steel, 16 mm in diameter, and 200 mm in spacing. The installation template can be selected as a 6 mm thick steel template, fixed by bolt connection. The pouring concrete can be selected as C45 non-shrinkage concrete, with a slump of 180±20 mm. The signal line of the pressure sensor is introduced into the embedded stainless steel conduit, which can be set to 25 mm in outer diameter and 1.5 mm in wall thickness. The signal line is connected to the permanent underwater connector, which can be selected as a six-core titanium alloy wet plug-in electrical connector.

[0045] The seventh step is system handover and long-term monitoring. After the pipeline system is put into use, the permanent underwater connector is connected through an underwater robot, which can be selected as a remote-controlled unmanned submersible with a manipulator. The pressure data of the pressure self-adaptive sealing cavity of the rotary flange joint are collected and monitored for a long time, with a data collection frequency of once an hour and a monitoring period of the design service life of the pipeline.

[0046] Compared with the prior art, the method can achieve better sealing reliability and longer service life. Through the design of the pressure self-adaptive sealing cavity, the sealing specific pressure is automatically enhanced by the internal pressure of the pipeline, solving the problem of sealing performance degradation of traditional flange joints due to bolt stress relaxation in deep water environment. The whole system realizes direct and long-term monitoring of the sealing state, providing reliable technical support for deep water pipeline interfaces.

[0047] According to still another embodiment of the present application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, the pressure sensor connected to the pressure sensor interface of the pressure self-adaptive sealing cavity can be a piezoresistive pressure sensor, the built-in self-checking circuit of which comprises a miniature electromagnetic actuator and a reference piezoresistive element. The self-checking circuit is activated automatically once every 24 hours, and when activated, the electromagnetic actuator generates a mechanical displacement corresponding to a pressure of 0.5 MPa applied to the reference piezoresistive element, with a duration of 5 seconds. If the deviation of the sensor output value from the expected standard value exceeds 2%, it is determined that the measurement channel is abnormal and a warning signal is issued. The pressure sensor also integrates a reference pressure source based on a quartz resonator, with a reference pressure of 0.1 MPa, which can be used as a reference for on-site calibration.

[0048] All transmission of sensing data is encoded using Hamming code error checking and correction algorithm, which is implemented in the signal processing unit. Hamming code uses a 74-bit encoding format, of which 64 bits are data bits and 10 bits are check bits. Data transmission is carried out at a rate of 1000 data packets per second, each data packet containing a complete Hamming code word. At the receiving end, the decoder detects and corrects single-bit errors while detecting double-bit errors. When an uncorrectable error is detected, the system automatically requests retransmission of the data packet, ensuring the integrity of data transmission. The signal processing unit can use an industrial-grade embedded processor to implement these algorithm functions.

[0049] The built-in self-checking and calibration functions and error correction encoding transmission in the present scheme effectively overcome the interference of the complex underwater environment and provide a more stable and reliable data basis than traditional systems.

[0050] According to still another embodiment of the present application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, a nanosecond pulsed fiber laser with a wavelength of 1064 nm is used to process a parallel rib structure with a period of 50 microns and a depth of 5 microns on the outer surface of the pressure sensor external packaging sleeve. The packaging sleeve is made of 316L stainless steel, and laser processing and subsequent electrolytic polishing treatment ensure the formation of the microstructure without affecting the sensing performance of the internal fiber grating. The laser processing parameters can be set as pulse energy 0.1 millijoule, repetition frequency 50 kHz, and scanning speed 200 millimeters per second. After processing, electrolytic polishing treatment is used to make the surface roughness reach Ra 0.2 microns or less.

[0051] The plug-in surface of the permanent underwater connector is treated with the same microstructure antifouling process, and the connector shell material can be selected from Ti-6Al-4V titanium alloy. The low-power pulse electrolytic antifouling circuit integrated in the shell uses platinum-iridium alloy electrodes with a composition of 90% platinum and 10% iridium. The electrode spacing is set to 5 mm, and the circuit is controlled by a programmable timer, which generates a 10-millisecond pulse current every 6 hours, with a pulse amplitude of 100 milliamps and a voltage of 12 volts direct current. The circuit uses a constant current source design to ensure stable current under different water quality conditions.

[0052] The pressure sensor interface of the pressure adaptive sealed cavity is connected to the pressure sensor through a pressure-resistant stainless steel cabin filled with silicone oil, which completely isolates seawater corrosion while transmitting pressure. The cabin can be made of zero-level Ti-6Al-4V titanium alloy with an inner diameter of 20 mm and a wall thickness of 3 mm. The cabin is filled with phenylmethyl silicone oil with a viscosity of 1000 centistokes and a thermal expansion coefficient of 0.0009 per °C. One end of the cabin is connected to the pressure sensor interface (1 / 4 NPT internal threaded hole) on the rotating flange through a threaded connection, and the other end is installed with a pressure sensor (which can be a piezoresistive pressure transmitter or a silicon resonant pressure sensor). Double O-ring seals are used between the pressure sensor and the cabin, and the O-ring material can be selected from fluorine rubber with a cross-sectional diameter of 2.6 mm. When the pressure in the pressure adaptive sealed cavity changes, the pressure is transmitted to the pressure sensor in the cabin through the silicone oil medium without loss, and the electrical elements of the pressure sensor are completely located in the cabin and isolated from the corrosive seawater environment.

[0053] A stainless steel bellows is installed inside the oil-filled cabin as a pressure compensation element, with an effective area of 3 square centimeters, a stroke of 10 mm, and a pre-compression amount of 50%. This structure can compensate for the volume change of silicone oil due to temperature changes while maintaining internal and external pressure balance. After the oil-filled cabin is assembled, it needs to be pressure tested at 1.5 times the design working pressure for 30 minutes without leakage to be qualified.

[0054] Compared to single antifouling technology, the bionic microstructure and pulse electrolysis composite antifouling strategy of this scheme provides more durable and comprehensive protection, effectively solving the problem of rapid degradation of sensor probes and other key parts due to marine biofouling and corrosion. The physical isolation design of the pressure-resistant oil-filled cabin fundamentally avoids the corrosion of seawater on sensitive elements, significantly improving long-term reliability compared to direct exposure packaging.

[0055] According to still another embodiment of the present application, there is provided a method for underwater sealing butt joint of a deepwater large-diameter composite pipeline rotary flange, wherein the electrode system of the low-power pulsed electrolytic anti-fouling circuit adopts a combination of a platinum-iridium alloy cathode and a magnesium alloy sacrificial anode. The platinum-iridium alloy cathode can be made of a platinum-iridium alloy material containing 10% iridium and processed into a round rod electrode with a diameter of 3 mm. The magnesium alloy sacrificial anode can be made of AZ63 magnesium-aluminum alloy and processed into a round rod electrode with the same size as the cathode. The two electrodes are installed in parallel in the insulating sleeve of the shell, with a spacing of 5 mm and a length of 10 mm of the electrode top exposed to the sleeve.

[0056] The cathode is connected to the negative pole of the pulse power source through a 0.5 square millimeter corrosion-resistant Teflon wire, and the wire joint is reliably connected to the electrode by silver brazing. The sacrificial anode is connected to the positive pole of the pulse power source through a wire of the same specification, and all wire joint parts are waterproofly sealed by epoxy resin sealant. The pulse power source can be a direct current pulse power source with an output power of 10 watts, a maximum output voltage of 12 volts, and a maximum output current of 1 ampere.

[0057] The current monitoring module integrated in the circuit adopts a 0.01-ohm precision sampling resistor connected in series in the electrolysis circuit. The voltage signal at both ends of the sampling resistor is collected by a 16-bit analog-to-digital converter with a sampling frequency of 1000 Hz. The current monitoring module measures the current value of the electrolysis circuit in real time, with a measurement accuracy of ±1 milliampere.

[0058] The voltage regulation module is realized by a 32-bit microcontroller, which has a built-in digital filter to smooth the current sampling signal. The current monitoring module measures the current value I actual (t) of the electrolysis circuit at any time t, and compares it with the preset current threshold I set . The preset current threshold I set can be set to 100 milliampere. When a current deviation is detected, the voltage regulation module uses a proportional-integral (PI) control algorithm to dynamically adjust the output voltage V out of the pulse power source according to the current deviation value. The control algorithm is realized by the following formula:

[0059]

[0060] wherein V out (t) is the control output voltage at time t (unit: V, volt), I actual (t) is the real-time actual monitoring current at time t (unit: mA, milliampere), e(t)=I set (t)-I actua l(t) is the current deviation value; K p is the proportional coefficient, which can be set to 100 volts / ampere; K iFor the integral coefficient, 20 volts / (ampere-second) can be set, and the coefficient is stored in the nonvolatile memory of the microcontroller.

[0061] The microcontroller is connected with the digital potentiometer through an I2C interface, the digital potentiometer adopts 128 adjustment gears, and the adjustment accuracy is 10 millivolts. The microcontroller accurately controls the output voltage of the pulse power by setting the resistance value of the digital potentiometer according to the calculation result of the control algorithm.

[0062] The response time of the whole regulation process is less than 100 milliseconds, ensuring the stability of the electrolysis current. The circuit board adopts a 4-layer PCB design, all components are surface-mounted, and the overall circuit board is waterproofly packaged with polyurethane potting glue.

[0063] Unlike the traditional direct electrolysis antifouling scheme in which all electrodes are consumed, the cathode protection and sacrificial anode design of the present scheme shifts the consumption to replaceable inexpensive components, solving the problem of high maintenance costs caused by the consumption of noble metal electrodes due to electrochemical corrosion and the need for overall replacement. The intelligent current closed-loop regulation ensures the stability of the antifouling effect and overcomes the problem of effect decay caused by electrode consumption or water quality changes.

[0064] According to another embodiment of the application, a method for underwater sealing and butt joint of a deepwater large-diameter composite pipe rotary flange is provided, wherein a wet-plug type multi-core conductive connector is selected as the permanent underwater connector, the plug core material is gold-plated beryllium copper alloy, the plating thickness is 1.5 microns, the beryllium content is 2%, and the copper content is 98%. The plug core contact body adopts a hyperboloid spring hole structure, each contact body has a diameter of 1.5 mm, and the plug-in and plug-out life can reach more than 500 times. The plug-in cavity is pre-filled with seawater corrosion-resistant fluorinated ether inert grease, and the grease can be selected from perfluoropolyether oil with a viscosity of 250 centistokes, a density of 1.8 grams per cubic centimeter, and a flash point of 260 DEG C.

[0065] The stainless steel mechanical guide funnel device outside the connector is made of 316L stainless steel and has three-stage guide taper. The first-stage guide taper is 45 degrees, the length is 50 mm, and is used for preliminary centering; the second-stage guide taper is 30 degrees, the length is 30 mm, and is used for fine guiding; and the third-stage guide taper is 15 degrees, the length is 20 mm, and is used for final positioning. The inner surface of the guide funnel is polished, and the surface roughness Ra is not greater than 0.8 microns.

[0066] The cable of the signal line is fixed by double clamps at the end of the connector to form a stress release structure. The inner clamp can be made of 316 stainless steel, with a width of 15 mm and a thickness of 2 mm, and is fastened by two M4 stainless steel screws. The inner clamp tightly fixes the armored layer of the cable, which is a 316 stainless steel wire mesh with a diameter of 0.2 mm and a weaving density of not less than 85%. The outer clamp is made of the same stainless steel material, with a width of 20 mm and a thickness of 2.5 mm, and is fastened by three M5 stainless steel screws. The outer clamp fixes the outer sheath of the cable, which can be made of polyurethane with a thickness of 1.5 mm and a Shore hardness of 85A.

[0067] The connection between the cable and the connector is protected by double sealing. The first sealing is epoxy resin pouring, with a pouring depth of 20 mm. The pouring glue can be selected from two-component epoxy resin, with a hardness of Shore D 80 after curing. The second sealing is protected by a heat shrink tube, which can be made of a glue-containing polyolefin with a shrinkage ratio of 3:1, a wall thickness of 1.2 mm, and a uniform sealing layer after shrinkage. The entire connector assembly needs to be pressure tested after installation, with a test pressure of 10 MPa, a pressure holding time of 30 minutes, and a leakage rate of not more than 1x10 -9 The qualified value is 1x10

[0068] Compared with the traditional underwater direct wiring or ordinary connector, the wet plug design and double stress release structure of the present solution effectively solve the long-term pain points of unreliable underwater connector connection, sealing failure and signal interruption caused by marine biological corrosion, plug wear or cable pulling, providing more durable and stable physical connection protection for data channels.

[0069] According to another embodiment of the present application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, wherein the male connector of the wet plug type multi-core conductive connector is installed through a passive self-adaptive alignment mechanism composed of a spherical universal joint and a flexible hinge. The spherical universal joint can be made of 440C stainless steel material, with a ball head diameter of 12 mm, a ball seat inner diameter of 12.02 mm, and a fitting gap of 20 microns. Molybdenum disulfide grease is filled between the ball head and the ball seat, with a thickness of 10 microns. The center point of the universal joint coincides with the theoretical plug-in center of the male connector, with a position deviation of not more than 50 microns.

[0070] The three flexible hinges are made of beryllium bronze material, with a thickness of 0.5 mm, a width of 5 mm, and a length of 8 mm. The hinges are evenly distributed in a 120-degree circumferential direction, and the flexibility coefficient k of each hinge is 0.05 mm per Newton. The male connector is constrained by a group of pre-compressed silicone rubber damping elements in the initial position, with a diameter of 8 mm, a height of 5 mm, a pre-compression amount of 30%, and a pre-pressure F pre The pre-pressure F

[0071] Translation freedom δ of the male connector in the X, Y axis direction x δ y Rotation freedom θ around the X, Y axis x θ y The range of motion is not less than ±2 degrees. In a preferred embodiment, the translation freedom is ±2 mm and the rotation freedom is ±2 degrees. When the lateral contact force F generated during the insertion process is greater than 5 Newton, the male connector will generate a displacement d in the same direction as the contact force, and the displacement is proportional to the size of the contact force, the relationship satisfies d = 0.05 × (F-5). The adaptive motion is achieved through the elastic deformation of the flexible hinge, and the maximum allowed contact force is 100 Newton, corresponding to the maximum compensation displacement of 5 mm.

[0072] Compared with the rigidly connected connector, the passive adaptive alignment mechanism allows the male connector to make fine adjustments at the moment of insertion, effectively solving the technical problem of pin damage and connection failure caused by small misalignment due to underwater flow field disturbance or operation deviation, reducing the harsh requirements on the operation precision of underwater robots, and improving the success rate of docking and equipment safety.

[0073] According to another embodiment of the application, a method for underwater sealing and docking of a deepwater large-diameter composite pipeline rotary flange is provided, wherein the machine learning model used for long-term collection and monitoring is based on a deep neural network architecture, and the network input layer includes 4 feature parameters, including 1 sealing cavity pressure data, 2 pipeline internal operating pressure data and 1 flow data. The sampling frequency of the pressure data is 0.1 Hz, and the sampling frequency of the flow data is 0.1 Hz. All input data are standardized, subtracted by the mean and divided by the standard deviation, so that the mean of each feature is 0 and the standard deviation is 1.

[0074] The deep neural network includes 3 hidden layers, the first hidden layer has 64 neurons and uses ReLU activation function; the second hidden layer has 32 neurons and uses ReLU activation function; the third hidden layer has 16 neurons and uses Sigmoid activation function. The output layer has 1 neuron, which outputs a health status score, and the score range is 0 to 1. The network uses Adam optimizer for training, the learning rate is set to 0.001, the batch size is 32, and the training period is 100.

[0075] The system can automatically identify the slow degradation trend of the sealing performance, generate a blue observation warning when the health score is below 0.8, a yellow warning signal when the score is below 0.6, and a red alarm signal when the score is below 0.4. The maintenance decision suggestion outputs the maintenance urgency level, which is divided into three levels: recommended observation, planned maintenance, and emergency treatment. The retraining task of the machine learning model is automatically performed by a remote cloud server or high-performance computing platform every 24 hours. The latest 30 days of data are used to retrain the model. The updated model parameters are transmitted to the local processing unit of the pipeline monitoring system through a secure network channel for loading and subsequent inference application, ensuring that the model adapts to changes in system state.

[0076] Compared with traditional monitoring systems that only provide real-time status display, the machine learning model can learn and identify performance degradation trends from historical data, solving the problem of massive monitoring data that cannot be effectively converted into predictive maintenance decisions, and achieving a transition from "after-the-fact maintenance" to "predictive maintenance", improving operational safety and economic efficiency.

[0077] Implementation case: applied to a certain submarine water supply pipeline installation project. The project requires laying two 1000mm diameter steel pipes, with a 200mm thick concrete coating, a single pipe length of about 1167 meters, a maximum construction water depth of 27 meters, and a submarine mud of silt clay.

[0078] The construction first completes the outer concrete work of the 12-meter-long pipe joint in the onshore precast yard. The pipe joint has a 450mm long welding section at both ends, uses API 5L X52 steel grade straight seam welded pipe, and has a wall thickness of 12.7mm. In a special assembly site, a 500-ton floating crane is used to hoist the pipe joint to the semi-submersible barge deck cradle for assembly and welding. After welding, 100% radiographic inspection is performed on each weld to ensure that the interface concrete construction is qualified.

[0079] The pipeline installation adopts the segmental sinking method. First, the base trench is treated, and a multi-beam sounding system is used to scan the base trench to confirm that the elevation meets the design requirements, and then a gravel cushion is laid at the precast pipe segment installation position. The gravel cushion uses 10 to 30mm diameter granite gravel, with a laying thickness of 500mm and a width of 5m, and the flatness error is controlled within ±50mm.

[0080] The first precast pipe segment is 64 meters long and weighs about 137 tons. The precast pipe segment has a specially designed rotating flange welded at both ends. The rotating flange has an outer diameter of 1200mm, a thickness of 100mm, 24 bolt holes, and is connected by M27 bolts. The sealing surface of the rotating flange is processed with an annular pressure self-adaptive sealing cavity with a width of 8mm and a depth of 5mm, which is connected to the pipe cavity through a miniature one-way valve.

[0081] Before the precast pipe segment is launched, a water-blocking bag is installed in the north end of the pipe. The water-blocking bag has a diameter of 980 mm, a length of 1500 mm, and a working pressure of 0.5 MPa. A pressure test blind plate is installed in the south end. The blind plate has a thickness of 30 mm and is fastened by 24 M27 bolts. The air tightness test is performed by pressurizing to 0.6 MPa and maintaining the pressure for 30 minutes. After the pressure drop is less than 3%, the precast pipe segment is ready for launching.

[0082] A 500-ton full-rotation crane ship is used to hoist the precast pipe segment. A 72-meter-long special hoisting beam is used, and four hoisting points are set with a spacing of 15 meters. The crane ship slowly sinks the precast pipe segment into the water, and at this time the underwater weight of the precast pipe segment is about 34 tons. The precast pipe segment is accurately sunk to the designed position by the RTK positioning system. The precast pipe segment is supported at both ends on the pre-laid gravel cushion.

[0083] After the diver inspects the precast pipe segment in place, the flange connection operation is started. Hydraulic tensioning equipment is used to simultaneously stretch the double-headed studs, and the pre-tightening force is controlled at 210 kN, which is equivalent to 70% of the yield strength of the bolt material.

[0084] After the fastening is completed, the pressure self-adaptive sealing system is activated. Water is injected into the pipe to pressurize, and when the pressure reaches 0.1 MPa, the micro one-way valve in the pressure self-adaptive sealing cavity opens, and the pressure water in the pipe enters the pressure self-adaptive sealing cavity to establish back pressure. The pressure test is carried out in stages: first, pressurize to 0.75 MPa and maintain for 15 minutes; then pressurize to 1.5 MPa and maintain for 30 minutes; finally, pressurize to 2.25 MPa and maintain for 24 hours. The pressure drop is less than 0.05 MPa, and the pressure test is qualified.

[0085] Next, the joint treatment is carried out. The diver binds the steel reinforcement underwater, and the steel reinforcement has a diameter of 16 mm and a spacing of 200 mm. After installing the steel formwork, C45 non-shrinkage concrete is used for pouring, and the concrete slump is controlled at 180±20 mm. After pouring is completed, the joint is cured for 28 days, and during this period, the joint status is monitored through the embedded sensor.

[0086] Finally, the monitoring system is installed. The signal line of the pressure sensor is led to the permanent underwater connector, which is installed in the special protection box on the top of the pipe. After the system is put into use, the underwater robot is regularly connected to the connector to collect pressure data of the pressure self-adaptive sealing cavity. The data is analyzed by a machine learning model, and the health status score reaches 0.92, and the system operates normally.

[0087] During the implementation of the project, all materials are commercial products, and the construction technology strictly follows the specification requirements, ensuring the quality and safety of the project. The entire system has been monitored for 12 months, and all indicators meet the design requirements, proving the reliability and practicality of the method.

[0088] The number of devices and processing stages described herein are used to simplify the description of the application. Applications, modifications and variations of the application will be apparent to those skilled in the art without departing from the general concept of the application.

[0089] While the embodiments of the application have been disclosed in connection with the specification and examples herein, it should be understood that they are not limited to the particular details so far set forth, but instead are entitled to modification and variations offering many applications thereof. It is therefore contemplated to cover any and all modifications, variations or equivalents that fall within the scope of the present application as defined in the following claims and their equivalents.

Claims

1. A method for underwater sealing butt joint of deepwater large-diameter composite pipe rotary flange, characterized in that, Comprising the following steps: Step one, preparation of prefabricated pipe segment and intelligent flange: welding rotary flange on both ends of prefabricated pipe segment; the rotary flange has an annular pressure self-adaptive sealing cavity pre-processed on the butt joint disc surface, the pressure self-adaptive sealing cavity is communicated with the inner cavity of the prefabricated pipe segment through the pre-embedded micro one-way valve; the rotary flange is equipped with a double-headed stud in the bolt hole, and the pressure self-adaptive sealing cavity is reserved with a pressure sensor interface; Step two, end sealing and inspection of prefabricated pipe segment: install a water bladder on the butt joint end of the prefabricated pipe segment and install a blind plate on the other end, and conduct air tightness test; Step three, positioning and support system layout: use positioning pile and support water bladder to assist the underwater positioning of prefabricated pipe segment; Step four, underwater pulling and intelligent fastening of prefabricated pipe segment: pull the rotary flanges of the two prefabricated pipe segments by hand-operated hoist to align the rotary flange disc surfaces; use hydraulic stretching equipment to stretch the double-headed stud synchronously to ensure that the pre-tightening force is uniform and reaches the set value; Step five, activation and pressure test of pressure self-adaptive sealing system: after fastening, water is injected into the pipeline composed of multiple prefabricated pipe segments underwater to pressurize; the internal pressure water enters the pressure self-adaptive sealing cavity through the micro one-way valve to establish back pressure; conduct staged water pressure test to inspect the sealing performance of the rotary flange joint; Step six, joint wrapping with concrete and integration of monitoring system: bind reinforcement, install formwork and pour concrete at the rotary flange joint; introduce the signal line of the pressure sensor into the pre-embedded conduit and connect it to the permanent underwater connector; Step seven, system handover and long-term monitoring: after the pipeline system is put into use, connect the permanent underwater connector through underwater robot to collect and monitor the pressure data of the pressure self-adaptive sealing cavity of the rotary flange joint for a long time; The pressure sensor interface of the pressure self-adaptive sealing cavity is connected to the pressure sensor with a built-in self-checking circuit, which can periodically stimulate the pressure sensor to generate a standard signal to verify the integrity of its measurement channel, and realize field calibration through the built-in reference pressure source; all transmission of sensing data is encoded using Hamming code error checking and correction algorithm to ensure the integrity of the data during transmission.

2. The method of underwater seal butt joining of deepwater large diameter composite pipe rotary flanges as claimed in claim 1, wherein, The plug-in surface of the permanent underwater connector is prepared with sharkskin rib-shaped microstructure with a width of 50 microns by laser etching process to inhibit the attachment of marine larvae, and a low-power pulse electrolytic antifouling circuit with platinum-iridium alloy electrodes is integrated in its shell, which releases a pulse current with a duration of 10 milliseconds every 6 hours; the pressure sensor interface of the pressure self-adaptive sealing cavity is connected to the pressure sensor through a pressure-resistant stainless steel cabin filled with silicone oil, which completely isolates seawater corrosion while transmitting pressure.

3. The method of underwater seal butt joining of deepwater large diameter composite pipe rotary flanges according to claim 2, characterized in that, The electrode system of the low-power pulse electrolysis anti-fouling circuit consists of a platinum-iridium alloy cathode and a magnesium alloy sacrificial anode; the cathode is connected to the negative terminal of the pulse power supply, and the sacrificial anode is connected to the positive terminal of the pulse power supply; the circuit integrates a current monitoring module and a voltage regulation module, and the current monitoring module measures the electrolysis circuit current value I in real time. actual The voltage regulation module will I actual With preset current threshold I set The values ​​are compared, and based on the deviation, the output voltage V of the pulse power supply is dynamically adjusted through a closed-loop feedback control algorithm. out So that I actual Stable at I set .

4. The method of underwater seal butt joining of deepwater large diameter composite pipe rotary flanges as claimed in claim 1, wherein, In step six, the permanent underwater connector is a wet-pluggable multi-core conductive connector, the plug core is made of gold-plated beryllium copper material, and the plug-in cavity is pre-filled with seawater corrosion-resistant fluorinated ether inert grease; the permanent underwater connector is externally equipped with a stainless steel mechanical guide funnel device with three-stage guide taper; the conduit introducing the signal line forms a stress release structure at the end of the permanent underwater connector using a double-jacket fixing method, in which the inner jacket fixes the cable armor layer and the outer jacket fixes the cable outer sheath.

5. The method of underwater seal butt joining of deepwater large diameter composite pipe rotary flanges as claimed in claim 4, wherein, The male connector of the wet-pluggable multi-core conductive connector is installed inside the shell through a passive self-adaptive alignment mechanism; the passive self-adaptive alignment mechanism is composed of a spherical universal joint providing two rotational degrees of freedom and three flexible hinges providing translational degrees of freedom; the center point O of the universal joint coincides with the theoretical plug-in center of the male connector; when the male connector is in the initial position, the spatial position thereof is constrained by a set of pre-compressed silicone rubber damping elements, the translational degrees of freedom δ x ,δ y of the male connector in the X and Y axis directions and the rotational degrees of freedom θ x ,θ y of the male connector around the X and Y axes respectively have a range of motion not less than 2 mm and 2° respectively; When the lateral contact force F generated during the insertion process is greater than the pre-pressing force F pre of the damping element, the male connector will produce displacement d, the displacement direction of which is the same as the contact force direction, and the displacement size is proportional to the contact force size, and the relationship satisfies d=k×(F−F pre ), wherein k is the flexibility coefficient of the flexible hinge; the adaptive movement enables the male connector to compensate for the final docking deviation.

6. The method of underwater seal butt joining of deepwater large diameter composite pipe rotary flanges as claimed in claim 1, wherein, In step seven, long-term acquisition and monitoring is realized based on a machine learning model, which takes pressure self-adaptive sealing cavity pressure data and pipeline internal pressure and flow operation parameters as input features, calculates the health status score of the sealing system through a trained deep neural network model, and automatically identifies the slow degradation trend of the sealing performance. When the health score is lower than the preset threshold, a graded early warning signal is automatically generated, and specific maintenance decision suggestions, including maintenance urgency level, are output.