Rotary flange underwater sealing butt joint method for deepwater large-diameter composite pipeline

Abstract

The invention discloses a rotary flange underwater sealing butt joint method for a deepwater large-diameter composite pipeline, and belongs to the technical field of submarine pipeline engineering. According to the method, aiming at the problems that a traditional flange joint is insufficient in sealing reliability in a deepwater dynamic environment and lacks a long-term monitoring means, a pressure self-adaptive sealing cavity is formed in a rotating flange disc surface, internal pressure is utilized to enhance sealing specific pressure, and a pressure sensor is integrated to monitor a sealing state in real time; and meanwhile, a pressure sensor interface is reserved to realize long-term data acquisition. The device is mainly used for installation, operation and maintenance of submarine water and oil gas pipelines, and long-term sealing safety of pipeline connectors can be effectively guaranteed.

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 deepwater environment, because the traditional static sealing cannot adapt to long-term water pressure fluctuation, bolt stress relaxation and foundation settlement, and there is a lack of effective means to monitor the sealing state of the underwater joint for a long time.

[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 it will be 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 it is unreliable, signal interruption and sealing failure due to reasons such as plug wear, marine organism corrosion and cable pulling during long-term use.

[0011] The technical problem of solving the wet plug 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 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: 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; 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 conducting air tightness test; Step three, laying of positioning and supporting system: using positioning piles and supporting water bags to assist the underwater positioning of the prefabricated pipe section; Step four, underwater pull together and intelligent fastening of prefabricated pipe segments: the rotating flanges of two prefabricated pipe segments are pulled together by a hand chain block, so that the rotating flange plates are aligned; a hydraulic stretching device is used to synchronously stretch the stud bolts, so that the pre-tightening force is uniformly ensured to reach the set value; Step five, activation and pressure test of the pressure 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 adaptive sealing cavity through the micro one-way valve to establish back pressure; a staged water pressure test is performed to check the sealing performance of the rotating flange joint; Step six, joint wrapping with concrete and integration of the monitoring system: steel bars are bound, forms are installed, and concrete is poured at the rotating flange joint; the signal line of the pressure sensor is led into the embedded conduit and connected to the permanent underwater connector; Step seven, system handover and long-term monitoring: after the pipeline system is put into use, the permanent underwater connector is connected by an underwater robot to collect and monitor the pressure data of the pressure adaptive sealing cavity of the rotating flange joint for a long time.

[0014] 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, the self-checking circuit can periodically excite the pressure sensor to generate a standard signal to verify the integrity of its measurement channel, and realize 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.

[0015] 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 by laser etching process to inhibit marine larvae attachment, and a low-power pulsed electrolytic antifouling circuit with platinum-iridium alloy electrodes is integrated in its shell, the antifouling circuit 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, realizing pressure transmission while completely isolating seawater corrosion.

[0016] Preferably, in the deepwater large-diameter composite pipeline rotating flange underwater sealing butt joint method of the present application, the electrode system of the low-power pulsed electrolytic antifouling circuit consists of a platinum-iridium alloy cathode and a magnesium alloy sacrificial anode; the cathode is connected to the negative electrode of the pulse power supply, and the sacrificial anode is connected to the positive electrode 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, and the voltage regulation module compares I actual with the preset current threshold I setThe comparison is made, and based on the deviation value, the output voltage V of the pulse power supply is dynamically adjusted by a closed-loop feedback control algorithm out , so that I actual is stabilized at I set .

[0017] Preferably, in the deepwater large-diameter composite pipeline rotary flange underwater sealed butt joint method of the present application, in step six, the permanent underwater connector is a wet-pluggable multi-core conductive connector, the plug-in core of which 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.

[0018] Preferably, in the deepwater large-diameter composite pipeline rotary flank underwater sealed butt joint method of the present application, the male connector of the wet-pluggable 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 group of pre-compressed silicone rubber damping elements, and the active ranges of its translational freedom [delta x , delta y ] in X and Y axis directions and rotational freedom [theta x , theta y ] around X and Y axes are not less than 2mm and 2° respectively; 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 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 self-adaptive movement enables the male connector to compensate for the final butt joint deviation.

[0019] Preferably, in the deepwater large-diameter composite pipeline rotary flange underwater sealed butt joint method of the present application, in step seven, long-term collection 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; 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.

[0020] The present application at least includes the following beneficial effects: 1、The method of the present application brings fundamental improvement by setting pressure self-adaptive sealing cavity and integrating 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. It changes the interface from an invisible black box to a perceptible transparent system, providing a solid data foundation for evaluating its health status and developing maintenance strategies, and realizing the transition from passive maintenance to active prevention.

[0021] 2、The method of the present application greatly improves the robustness and data reliability of the monitoring system by using 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 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.

[0022] 3、The method of the present application provides long-term and effective protection for underwater sensors by using a dual protection strategy combining bionic microstructure antifouling and electrolytic antifouling. The shark skin rib microstructure changes the surface properties through physical means, greatly increasing the difficulty of attachment of marine larvae and reducing pollution from the source. The low-power pulse 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 effect. Encapsulating the sensor interface in a pressure-resistant oil-filled cabin is a complete physical isolation method that completely isolates the core sensitive elements 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.

[0023] 4. The method of the present application ingeniously solves the core contradiction of electrolytic electrode loss by introducing a sacrificial anode and an intelligent control circuit. The use of expensive platinum-iridium alloy as the cathode makes it almost not lost during the electrolysis process, while the easy-to-wear function is transferred to the low-cost and replaceable magnesium alloy sacrificial anode. This design simplifies the maintenance operation from replacing the entire expensive electrode to replacing the standardized anode block, greatly reducing the maintenance cost throughout the life cycle. The current monitoring and voltage regulation module constitutes a closed-loop control system, which can sense the change of electrolytic current in real time and maintain the set current value by automatically adjusting the output voltage, which ensures the stability and consistency of the antifouling effect under different water conductivity and anode consumption, and ensures long-term reliable antifouling performance.

[0024] 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. The wet plug technology and inert grease filling ensure the electrical continuity and sealing of the connector when it is directly plugged underwater, avoiding the trouble of drainage operation required by traditional connection methods. The double sleeve stress release structure scientifically disperses the pulling force of the cable. The inner sleeve fixes the armored layer resistant to tension, and the outer sleeve protects the waterproof sheath layer. This design effectively prevents the joint from loosening, signal interruption or sealing 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 environment, and providing a solid physical foundation for long-term stable data transmission.

[0025] 6. The method of the present application uses a passive self-adaptive alignment mechanism, which converts the extremely high precision required for docking from relying on external operation to being absorbed by the internal mechanical structure. The mechanism composed of universal joints and flexible hinges allows the male connector to make slight translation and deflection 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 accuracy 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.

[0026] 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 tiny abnormal trend indicating performance degradation, thus giving an early warning long before the sealing performance substantially declines or failure occurs. Instead of outputting disordered data, it outputs analyzed health scores, specific fault location and maintenance suggestions, enabling the maintenance personnel to change from "after-the-fact remedy" to "before-the-fact prevention", plan maintenance window period with pertinence, effectively avoid unplanned shutdown, greatly improve the safety and economy of pipeline operation, and fully exploit the potential value of long-term monitoring data.

[0027] Other advantages, objects, and features of the present application will be understood by those skilled in the art from the following specification in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0028] The present application is further described in detail by making reference to the accompanying drawings in conjunction with the following specification.

[0029] 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.

[0030] According to one embodiment of the present application, a method for underwater sealing butt joint of a deepwater large-diameter composite pipeline rotary flange is provided. The first step of the method is to prepare a prefabricated pipe section and an intelligent flange. The rotary flanges welded at both ends of the prefabricated pipe section can be forged steel flanges meeting the 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 in communication with 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 drill hole on the side surface of the rotary flange by screw connection. A double-headed stud is arranged in the bolt hole of the rotary flange. The material of the double-headed stud can be 42CrMo alloy steel, and threads conforming to ISO 4014 standard are machined at both ends of the double-headed stud. 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.

[0031] The second step is to seal and inspect the end of the prefabricated pipe section. A water-blocking bladder is installed at 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-blocking bladder can be a cylindrical air bladder made of butyl rubber, with a nominal diameter slightly smaller than the inner diameter of the pipe. During installation, compressed air is filled into the bladder through an inflation device to a working pressure of 0.5 MPa. A blind plate is installed at the 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, and is fastened with 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.

[0032] 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 bladder can be a product of the same specification as the blocking bladder. Four support bladders are arranged for each prefabricated pipe section, symmetrically arranged along the axis of the prefabricated pipe section. When laying out, the positioning pile and support bladder are lifted to the designed position using a crane, and the installation accuracy is adjusted underwater by divers.

[0033] The fourth step is to underwater pull together and intelligent fasten the prefabricated pipe section. The two prefabricated pipe sections are pulled together using a hand-operated hoist to align the rotating flanges, with a gap between the flanges controlled within 2 mm. The double-headed studs are simultaneously stretched using a hydraulic stretching device. The target pre-tightening force can be set to 70% of the yield strength of the bolt material, ensuring uniform distribution of the pre-tightening force.

[0034] The fifth step is to activate the pressure self-adaptive sealing system and perform pressure testing. After fastening, water is injected into the underwater pipe connected by multiple prefabricated pipe sections, and the internal pressure is gradually increased to 1.5 MPa using a plunger pump. The internal pressure water enters the pressure self-adaptive sealing cavity through a micro one-way valve, and when the cavity pressure reaches 0.1 MPa, the micro one-way valve opens, establishing back pressure. The water pressure test is performed in stages. First, pressurize to 0.75 MPa and maintain for 15 minutes, then pressurize to 1.5 MPa and maintain for 30 minutes, and finally pressurize to 2.5 MPa and maintain for 24 hours.

[0035] The sixth step is to integrate the joint outer concrete with the monitoring system. Steel bars can be selected for the joint at the rotating flange joint, with a diameter of 16 mm and a spacing of 200 mm. The installation template can be selected as a 6 mm thick steel template, which is 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, and the outer diameter of the conduit can be set to 25 mm and the wall thickness is 1.5 mm. The signal line is connected to the permanent underwater connector, and the connector can be selected as a six-core titanium alloy wet plug-in electrical connector.

[0036] The seventh step is system handover and long-term monitoring. After the pipeline system is put into use, the permanent underwater connector is connected by the underwater robot, and the underwater robot can be selected as a remote control unmanned submersible with a manipulator. The pressure data of the pressure self-adaptive sealing cavity of the rotating flange joint are collected and monitored for a long time, and the data collection frequency can be set to once an hour, and the monitoring period is the design service life of the pipeline.

[0037] Compared with the prior art, the method can realize 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 pressure in the pipeline, which solves the problem of sealing performance attenuation of the traditional flange joint due to bolt stress relaxation in deep water environment. The whole system realizes direct and long-term monitoring of the sealing state, and provides reliable technical support for the deep water pipeline interface.

[0038] According to another embodiment of the application, a deep water large diameter composite pipeline rotating flange underwater sealing butt joint method is provided, and the pressure sensor connected to the pressure sensor interface of the pressure self-adaptive sealing cavity can be selected as a piezoresistive pressure sensor. The built-in self-checking circuit of the pressure sensor includes a micro electromagnetic actuator and a reference piezoresistive element. The self-checking circuit is activated automatically 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.

[0039] All the transmission of sensor data is encoded with Hamming code error checking and correction algorithm, which is implemented in the signal processing unit. Hamming code uses 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, and each data packet contains 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.

[0040] The scheme has built-in self-checking and calibration functions as well as error correction encoding transmission, effectively overcoming the interference of complex underwater environments and providing more stable and reliable data basis than traditional systems.

[0041] According to another embodiment of the application, a method for underwater sealing and butt joint of a deepwater large-diameter composite pipe rotating flange is provided. A nanosecond pulse 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.

[0042] The plug surface of the permanent underwater connector is treated with the same microstructure antifouling treatment, 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 millimeters, and the circuit is controlled by a programmable timer to generate a 10-millisecond pulse current every 6 hours, with a pulse amplitude of 100 milliamperes 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.

[0043] The pressure sensor interface of the pressure self-adaptive sealed cavity is connected with the pressure sensor through a pressure-resistant stainless steel cabin filled with silicone oil, so that the pressure transmission is realized while the seawater corrosion is completely isolated. 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 degree Celsius. One end of the cabin is connected with the pressure sensor interface (1 / 4NPT inner threaded hole) on the rotary flange through a threaded connection, and the other end is provided with a pressure sensor (which can be a piezoresistive pressure transmitter or a silicon resonant pressure sensor). Double O-rings are used to seal between the pressure sensor and the cabin, and the O-ring material can be selected from fluororubber with a cross-sectional diameter of 2.6 mm. When the pressure in the pressure self-adaptive sealed cavity changes, the pressure is transmitted to the pressure sensor in the cabin through the silicone oil medium without damage, and the electrical elements of the pressure sensor are completely located in the cabin and isolated from the corrosive seawater environment.

[0044] A stainless steel bellows is arranged 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 caused by temperature change, while maintaining the balance of internal and external pressure. After the assembly of the oil-filled cabin is completed, pressure test needs to be carried out, and the test pressure is 1.5 times the design working pressure, and the pressure is maintained for 30 minutes without leakage.

[0045] Compared with a single antifouling technology, the bionic microstructure and the pulse electrolysis combined antifouling strategy in the scheme provide more durable and more comprehensive protection effect, and effectively solve the problem that the key parts such as sensor probes are rapidly degraded in function due to marine organism attachment and corrosion. The physical isolation design of the pressure-resistant oil-filled cabin fundamentally avoids the corrosion of seawater to sensitive elements, and significantly improves the long-term reliability compared with the direct exposure packaging mode.

[0046] According to another embodiment of the application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, wherein the electrode system of the low-power pulse electrolysis antifouling circuit adopts a combination of platinum-iridium alloy cathode and magnesium alloy sacrificial anode. The platinum-iridium alloy cathode can be made of platinum-iridium alloy material containing 10% iridium, 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, 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 an electrode spacing of 5 mm, and the electrode top end protrudes from the sleeve by 10 mm.

[0047] The cathode is connected to the negative terminal of the pulse power supply via a 0.5 mm² corrosion-resistant Teflon wire, with the wire connectors securely soldered to the electrodes. The sacrificial anode is connected to the positive terminal of the pulse power supply via a wire of the same specification, and all wire connectors are sealed with epoxy resin for waterproofing. A 10-watt DC pulse power supply with a maximum output voltage of 12 volts and a maximum output current of 1 ampere can be selected.

[0048] The integrated current monitoring module in the circuit uses a 0.01-ohm precision sampling resistor connected in series in the electrolysis circuit. The voltage signal across the sampling resistor is acquired by a 16-bit analog-to-digital converter at a sampling frequency of 1000Hz. The current monitoring module measures the current value of the electrolysis circuit in real time with a measurement accuracy of ±1 mA.

[0049] The voltage regulation module is implemented using a 32-bit microcontroller, which incorporates a digital filter to smooth the current sampling signal. The current monitoring module then processes the measured current value I. actual With preset current threshold I set Comparison, preset current threshold I set It can be set to 100 mA. When a current deviation is detected, the voltage regulation module uses a proportional-integral (PI) control algorithm to dynamically adjust the output voltage V of the pulse power supply according to the current deviation value. out The control algorithm is implemented by the following formula: Among them, V out (t): Control output voltage at time t (unit: V, volt), I actual e(t): Real-time actual monitored current at time t (unit: mA, milliampere), e(t) = I set -I actua l(t) is the current deviation value; K p This is the proportionality coefficient, which can be set to 100 volts / ampere; K i The integral coefficient can be set to 20 volts / (ampere-second), and this coefficient is stored in the microcontroller's non-volatile memory.

[0050] The microcontroller connects to a digital potentiometer via an I2C interface. The digital potentiometer has 128 adjustment levels with an adjustment accuracy of 10 millivolts. Based on the calculation results of the control algorithm, the microcontroller precisely controls the output voltage of the pulse power supply by setting the resistance value of the digital potentiometer.

[0051] The response time of the entire control process is less than 100 milliseconds, ensuring the stability of the electrolytic current. The circuit board adopts a 4-layer PCB design, all components are surface-mounted, and the entire circuit board is encapsulated with polyurethane potting compound for waterproofing.

[0052] Unlike all electrodes in the traditional direct electrolysis antifouling scheme, the cathode protection and sacrificial anode design of the present scheme shifts the consumption to replaceable and inexpensive components, solving the problem of high maintenance costs caused by the need to replace the entire electrode due to electrochemical corrosion of the noble metal electrode.

[0053] According to yet another embodiment of the present application, a method for underwater sealing and butt joint of a deepwater large-diameter composite pipeline rotary flange is provided, wherein a permanent underwater connector is selected as a wet-plug type multi-core conductive 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, the diameter of each contact body is 1.5 mm, and the plug-in service 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 as a perfluoropolyether oil with a viscosity of 250 centistokes, a density of 1.8 g / cm3, and a flash point of 260℃.

[0054] The stainless steel mechanical guide funnel device outside the connector is made of 316L stainless steel and has three levels of guide taper. The first level of guide taper is 45 degrees, the length is 50 mm, and is used for preliminary centering; the second level of guide taper is 30 degrees, the length is 30 mm, and is used for fine guiding; and the third level of 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.

[0055] The conduit introducing the signal line adopts a double-hoop fixing method at the connector end to form a stress release structure. The inner hoop can be made of 316 stainless steel, the hoop width is 15 mm, the thickness is 2 mm, and it is fastened by two M4 stainless steel screws. The inner hoop tightly fixes the armored layer of the cable, and the armored layer is a 316 stainless steel wire braid with a diameter of 0.2 mm and a weaving density of not less than 85%. The outer hoop is made of the same stainless steel material, the hoop width is 20 mm, the thickness is 2.5 mm, and it is fastened by three M5 stainless steel screws. The outer hoop fixes the outer sheath of the cable, and the outer sheath material can be polyurethane with a thickness of 1.5 mm and a Shore hardness of 85A.

[0056] The connection between the cable and the connector adopts double-seal protection. The first seal is epoxy resin pouring, the pouring depth is 20 mm, and the pouring glue can be selected as two-component epoxy resin with a hardness of Shore D 80 after curing. The second seal is protected by a heat shrink tube, the heat shrink tube material can be selected as a glue-containing polyolefin with a shrinkage ratio of 3:1 and a wall thickness of 1.2 mm, and a uniform sealing layer is formed after shrinkage. The entire connector assembly needs to be pressure tested after installation, the test pressure is 10 MPa, the pressure holding time is 30 minutes, and the leakage rate is not greater than 1×10 -9Pascal per second is qualified.

[0057] Compared with the traditional underwater direct wiring or ordinary connector, the wet plug-in design and the double stress release structure effectively solve the long-term pain points of unreliable underwater connector connection, sealing failure and signal interruption caused by marine organism corrosion, plug-in wear or cable pulling, and provide more durable and stable physical connection guarantee for data channel.

[0058] According to another embodiment of the application, a deepwater large-diameter composite pipeline rotary flange underwater sealing butt joint method is provided, wherein the male connector of the wet plug-in multi-core conductive connector is installed through a passive adaptive alignment mechanism composed of a spherical universal joint and a flexible hinge. The spherical universal joint can be made of 440C stainless steel, 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 grease 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.

[0059] 3 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 set of pre-compressed silicone rubber damping elements in the initial position, with a damping element diameter of 8 mm, a height of 5 mm, a pre-compression amount of 30%, and a pre-pressure F pre of 5 Newtons.

[0060] The translational freedom δ x , δ y of the male connector in the X, Y axis direction is not less than ±2 mm, and the rotational freedom θ x , θ y around the X, Y axis is not less than ±2 degrees. In a preferred embodiment, the translational freedom is ±2 mm and the rotational freedom is ±2 degrees. When the lateral contact force F generated during the plug-in process is greater than 5 Newtons, the male connector will produce a displacement d in the same direction as the contact force, and the displacement is proportional to the size of the contact force, with a relationship of d=0.05×(F-5). The adaptive motion is achieved through elastic deformation of the flexible hinge, and the maximum allowed contact force is 100 Newtons, corresponding to a maximum compensation displacement of 5 mm.

[0061] Compared with the rigidly connected connector, the passive adaptive alignment mechanism allows the male connector to be fine-tuned at the moment of plug-in, effectively solving the technical problems of pin damage and connection failure caused by small misalignment due to underwater flow field disturbance or operation deviation, reducing the stringent requirements on the operation precision of underwater robots, and improving the success rate of butt joint and equipment safety.

[0062] According to another embodiment of the present application, a method for underwater sealing butt joint of 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, the network input layer contains 4 feature parameters, including 1 sealing cavity pressure data, 2 pipeline internal operating pressure data and 1 flow data. The sampling frequency of pressure data is 0.1 Hz, and the sampling frequency of flow data is 0.1 Hz. All input data are standardized, subtracted by mean and divided by standard deviation, so that the mean of each feature is 0 and the standard deviation is 1.

[0063] The deep neural network contains 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 is 1 neuron, which outputs a health 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.

[0064] The system can automatically identify the slow degradation trend of sealing performance, generate a blue observation warning when the health score is lower than 0.8, generate a yellow warning signal when the score is lower than 0.6, and generate a red alarm signal when the score is lower than 0.4. The maintenance decision suggestion outputs the maintenance urgency level, which is divided into 3 levels: recommended observation, planned repair and emergency treatment. The retraining task of this machine learning model is automatically executed once every 24 hours by a remote cloud server or a high-performance computing platform, and the data of the last 30 days is used for model retraining. The updated model parameters after training are downloaded 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 system state changes.

[0065] Compared with the traditional monitoring system which can only provide real-time state 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, realizing the transition from "after-the-fact maintenance" to "predictive maintenance", and improving the operational safety and economy.

[0066] Implementation case: applied to Hong Kong Victoria Harbour submarine water supply pipeline installation project. The project needs to lay 2 steel pipes with a diameter of 1000 mm, the outer package is 200 mm thick concrete, the length of a single pipe is about 1167 meters, the maximum construction water depth is 27 meters, and the submarine silt is silt clay.

[0067] The construction first completed the 12-meter long pipe segment concrete work in the onshore precast yard. The pipe segment reserved 450mm long welding section at both ends, using API 5L X52 steel grade straight seam welded pipe, wall thickness 12.7mm. In the special assembly site, using 500-ton floating crane to hoist the pipe segment to the semi-submersible barge deck jig for assembly and welding. After the welding is completed, 100% radiographic inspection is carried out on each weld, and after passing the inspection, the concrete construction at the interface is carried out.

[0068] The pipeline installation adopts the segment sinking method. First, the foundation trench is treated, and the multi-beam sounding system is used to scan the foundation trench to confirm that the elevation meets the design requirements, and then the gravel cushion is laid at the precast pipe segment installation position. The gravel cushion uses 10 to 30mm particle size granite gravel, with a laying thickness of 500mm, a width of 5m, and a flatness error control within ±50mm.

[0069] The first precast pipe segment is 64 meters long and weighs about 137 tons. The precast pipe segment is welded with a specially designed rotating flange 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 micro one-way valve.

[0070] 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 980mm, a length of 1500mm, and a working pressure of 0.5MPa. A pressure test blind plate is installed at the south end, with a thickness of 30mm and fastened by 24 M27 bolts. The air tightness test is carried out by pressurizing to 0.6MPa and maintaining for 30 minutes, with a pressure drop of less than 3%. After passing the test, the launching is prepared.

[0071] A 500-ton full-rotation crane is used to hoist the precast pipe segment. The hoisting uses a 72-meter long special hoisting beam, with 4 hoisting points, and the hoisting point spacing is 15 meters. The crane 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. Through the RTK positioning system, the precast pipe segment is accurately sunk to the designed position, and the precast pipe segment is supported at both ends on the pre-laid gravel cushion.

[0072] After the diver inspects the precast pipe segment in place, the rotating flange connection operation begins. The hydraulic stretching equipment is used to stretch the double-end studs synchronously, with a pre-tightening force of 210kN, equivalent to 70% of the yield strength of the bolt material.

[0073] After the fastening is completed, the pressure self-adaptive sealing system is activated. Water is injected into the pipeline 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 pipeline enters the pressure self-adaptive sealing cavity to establish back pressure. Step-by-step pressure test is carried out: first, pressurize to 0.75 MPa, and keep pressure for 15 minutes; then, pressurize to 1.5 MPa, and keep pressure for 30 minutes; finally, pressurize to 2.25 MPa, and keep pressure for 24 hours. The pressure drop is less than 0.05 MPa, and the pressure test is qualified.

[0074] Next, the joint treatment is carried out. The diver binds the steel bars underwater, and the steel bars have 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 slump of the concrete is controlled to be 180±20 mm. After pouring is completed, curing is carried out for 28 days, and during this period, the joint state is monitored through the pre-embedded sensor.

[0075] Finally, the monitoring system is installed. The signal line of the pressure sensor is led to the permanent underwater connector, and the connector is installed in the special protection box at the top of the pipeline. After the system is put into use, the underwater robot is regularly connected to the connector to collect the pressure data of the pressure self-adaptive sealing cavity. The data is analyzed through the machine learning model, the health state score reaches 0.92, and the system operates normally.

[0076] During the implementation of the project, all materials are commercial products, and the construction process 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.

[0077] The number of devices and the scale of processing described here 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.

[0078] Although the embodiments of the application have been disclosed as above, they are not limited to the applications and embodiments listed in the specification, and can be fully applied to various fields suitable for the application, and additional modifications can be easily realized by those skilled in the art, therefore, the application is not limited to specific details and the examples shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for underwater sealing and connection of rotating flanges for deep-water large-diameter composite pipelines, characterized in that, Includes the following steps: Step 1: Preparation of prefabricated pipe sections and smart flanges: Weld rotating flanges to both ends of the prefabricated pipe sections; The mating plate of the rotating flange is pre-machined with an annular pressure adaptive sealing cavity, which is connected to the inner cavity of the prefabricated pipe section through a pre-embedded miniature check valve; Double-ended studs are installed in the bolt holes of the rotating flange, and a pressure sensor interface is reserved in the pressure adaptive sealing cavity. Step 2, sealing and inspection of prefabricated pipe section ends: Install sealing water bags at the joint ends of the prefabricated pipe sections and blind flanges at the other ends, and conduct airtightness inspection; Step 3, Positioning and Support System Deployment: Use positioning piles and support water bags to assist in the underwater positioning of prefabricated pipe sections; Step 4: Underwater connection and intelligent fastening of precast pipe sections: The rotating flanges of the two precast pipe sections are connected by hand-operated hoists to align the rotating flange faces; the double-ended studs are stretched synchronously using hydraulic tensioning equipment to ensure that the pre-tightening force is uniformly reached to the set value. Step 5: Activation and pressure test of the pressure adaptive sealing system: After tightening, water is injected into the underwater pipeline assembled from multiple prefabricated pipe sections to pressurize it; the internal pressurized water enters the pressure adaptive sealing cavity through a miniature one-way valve to establish back pressure; a graded water pressure test is conducted to check the sealing performance of the rotary flange joint. Step Six: Integration of the Joint with Concrete Encasing and Monitoring System: Tie reinforcing bars, 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 7: System handover and long-term monitoring: After the pipeline system is put into use, a permanent underwater connector is connected via an underwater robot to collect and monitor the pressure data of the pressure adaptive sealing cavity of the rotary flange joint over a long period of time.

2. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 1, characterized in that, The pressure sensor interface of the pressure adaptive sealed cavity is connected to a pressure sensor with a built-in self-test circuit. The self-test circuit can periodically excite 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 algorithms to ensure the integrity of the data during transmission.

3. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 2, characterized in that, The mating surface of the permanent underwater connector is made with a 50-micrometer-wide sharkskin-like rib-like microstructure using laser etching to inhibit the attachment of marine larvae. A low-power pulse electrolytic antifouling circuit with platinum-iridium alloy electrodes is integrated into its shell. The antifouling circuit 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 tank filled with silicone oil, so as to achieve pressure transmission while completely isolating seawater corrosion.

4. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 3, 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 .

5. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 1, characterized in that, In step six, the permanent underwater connector is a wet-pluggable multi-core conductive connector, whose core is made of gold-plated beryllium copper and pre-filled with seawater-resistant fluorinated ether inert grease; the permanent underwater connector is externally fitted with a stainless steel mechanical guide funnel device with three-stage guide taper; the conduit for introducing the signal line is fixed at the end of the permanent underwater connector with a double-hoop method to form a stress-relieving structure, wherein the inner hoop fixes the cable armor layer and the outer hoop fixes the cable outer sheath.

6. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 5, characterized in that, The male connector of the wet-plug multi-core conductive connector is mounted inside its housing via a passive adaptive alignment mechanism. This mechanism consists 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 mating center of the male connector. In its initial position, the male connector's spatial position is constrained by a set of pre-compressed silicone rubber damping elements, and its translational degrees of freedom in the X and Y axes [δ]... x ,δ y And rotational degrees of freedom about the X and Y axes [θ] x ,θ y The range of motion is not less than 2mm and 2° respectively; When the lateral contact force F generated during the mating process is greater than the preload F of the damping element pre When the male connector is in contact with the contact force, it will generate a displacement d. The direction of the displacement is the same as the direction of the contact force, and the magnitude of the displacement is proportional to the magnitude of the contact force, satisfying the relationship d = k × (FF). pre ), where k is the flexibility coefficient of the flexible hinge; this adaptive motion enables the male connector to compensate for the final mating deviation.

7. The underwater sealing and docking method for deep-water large-diameter composite pipeline rotating flanges as described in claim 1, characterized in that, In step seven, long-term data acquisition and monitoring are achieved based on a machine learning model. This model takes the pressure data of the pressure adaptive sealing cavity and the internal pressure and flow operation parameters of the pipeline as input features, and calculates the health status score of the sealing system through a trained deep neural network model. The sealing system can automatically identify the slow degradation trend of sealing performance. When the health score is lower than the preset threshold, it automatically generates a graded early warning signal and outputs specific maintenance decision suggestions, including the maintenance urgency level.

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