An exhaust valve and monitoring method suitable for monitoring gas pressure in an annulus of a marine pipeline

Abstract

The application discloses a kind of exhaust valve and monitoring method suitable for the gas pressure monitoring of marine pipeline annular area, a kind of exhaust valve suitable for the gas pressure monitoring of marine pipeline annular area, including valve core, valve body, guide cone structure, fixed shoe, arc elastic steel strip fixed in fixed shoe, optical fiber buried in valve body and first grating, second grating and third grating connected with optical fiber, by connecting optical fiber grating with armored cable, demodulator and computer, in the state that marine flexible pipeline inner annular area gas is discharged, by for different grating strain causes its transmission wavelength change and then monitors exhaust valve in situ state and internal annular area gas pressure, provide guidance for the maintenance of marine flexible pipeline pressure relief valve, avoid the damage of pipeline structure caused by the fact that annular area gas pressure exceeds design value due to pressure relief valve blockage etc., improve the safety and reliability of marine flexible pipeline operation.

Description

Technical Field

[0001] This invention relates to an exhaust valve and monitoring method for gas pressure monitoring in annular zones, and particularly to an exhaust valve and monitoring method suitable for gas pressure monitoring in annular zones of subsea pipelines, belonging to the field of marine flexible composite pipeline testing technology. Background Technology

[0002] Offshore oil pipelines are divided into steel pipes and flexible pipes. Currently, flexible pipes suitable for transporting media on the seabed are mostly flexible composite pipelines. Flexible composite pipelines are made of polymer materials and metal materials, and compared with steel pipes, they have significant advantages such as easy bending, easy laying, long service life, and low total investment. As the technology of flexible composite pipelines in China becomes more and more mature, flexible composite pipelines have been put into use in more and more oil and gas fields in my country.

[0003] During the service life of subsea flexible pipelines, gas in the transported medium can slowly seep into the annular region of the pipeline. To relieve pressure within this annular region, at least one vent valve is typically installed at the pipeline joint. When the pressure within the annular region rises to the vent valve's opening pressure, the valve automatically opens, releasing the pressure. Due to the complex subsea environment, vent valves may be subject to accidental damage during operation, such as marine organism cover or mud blockage, leading to valve failure. Vent valve failure poses a significant safety hazard to the normal operation of the pipeline. If gas cannot be released from the annular region, the pressure will rise, potentially causing the outer sheath to rupture and the internal pressure seal to collapse, damaging the pipeline structure and affecting its normal service life and overall lifespan.

[0004] Currently, the commonly used air release valves installed on flexible subsea pipeline joints automatically open when the pressure within the pipeline annular zone exceeds the sum of the spring pressure and the seawater pressure, releasing the pressure; and automatically close when the pressure within the annular zone does not exceed the sum of the spring pressure and the seawater pressure. The problem with this type of air release valve is that the actual opening pressure and functional status of the valve cannot be directly monitored. If the valve fails, it may not be detected and repaired in a timely manner, posing a significant safety risk to the pipeline.

[0005] Meanwhile, current gas pressure monitoring in the annular zone of submarine flexible pipelines is conducted by installing a flexible bypass hose at the starting section of the pipeline and installing a pressure sensor on the bypass hose to monitor the gas pressure in the annular zone. However, due to the different ambient temperatures and pressures of the bypass hose and the pipeline, the gas permeation rate varies, and the pipeline may be damaged due to unexpected operating conditions, causing seawater to enter the annular zone. Therefore, this method cannot accurately reflect the actual situation of the annular zone of the pipeline.

[0006] This patent application proposes an exhaust valve and monitoring method suitable for gas pressure monitoring in the annular zone of a subsea pipeline, against this background. Summary of the Invention

[0007] The main objective of this invention is to overcome the aforementioned shortcomings of the prior art and to provide an exhaust valve and monitoring method suitable for gas pressure monitoring in the annular zone of a subsea pipeline.

[0008] This invention is achieved through the following technical solutions:

[0009] An exhaust valve suitable for gas pressure monitoring in the annular zone of a subsea pipeline includes a valve core, a guide cone structure, a fixing shoe, an elastic steel strip, an optical fiber, a first grating, a second grating, a third grating, and a valve body;

[0010] The valve body is fixedly connected to the guide cone structure by threads. A valve bottom cover is installed at the bottom of the valve body. Air inlet holes are provided on both sides of the valve bottom cover. The optical fiber is embedded in the groove pre-set on the inner wall of the valve body by colloid.

[0011] A valve core spring is provided on a portion of the outer wall of the hollow cavity of the valve body. A limit block is installed on the side of the valve core near the exhaust hole. A second sealing ring is installed on the upper part of the limit block. A pressure cap is installed on the upper part of the second sealing ring by a fastening nut.

[0012] The guide cone structure is coaxial with the cone nut and has notches symmetrically arranged about the axis along the diameter direction. The inner walls of the notches in the guide cone structure are each fitted with a fixing shoe symmetrically arranged along the valve core axis. There are two sets of fixing shoes, and each fixing shoe contains a fixing shoe spring.

[0013] Each of the fixed boots is internally provided with an arc-shaped elastic steel strip, which is fixedly connected to the inner sidewall of the fixed boot by guide circular plates at both ends.

[0014] The inner curved surface of the elastic steel strip is evenly provided with the first gratings, which are fixedly connected to the optical fiber through a colloid. Two sets of the first gratings are connected in series with the optical fiber.

[0015] The lower end of the valve core is connected to a tapered nut, which is threaded to a diaphragm cover. Both ends of the diaphragm cover are threaded with a first sealing ring, and each of the first sealing rings is provided with a sealing interface that meets the requirements for the optical fiber to exit.

[0016] A diaphragm is disposed inside the membrane cover cavity. The second grating and the third grating are evenly distributed on the inner surface of the membrane cover. One end of the second grating is fixed in the radial direction of the diaphragm, and the third grating is fixed to the center of the diaphragm by an adhesive. The second grating and the third grating are connected in series with the optical fiber through the sealing interface.

[0017] Preferably, the taper of the conical nut matches the taper of the guide conical structure, and there is an equidistant gap between the conical surface of the conical nut and the conical surface of the guide conical structure to allow the conical nut to move up and down.

[0018] Preferably, the colloid used to embed the optical fiber is a flexible colloid; the colloid used to fix the first grating, the second grating, and the third grating is a rigid colloid.

[0019] This invention also relates to a method for monitoring gas pressure in a subsea pipeline annulus, the monitoring method comprising the following steps:

[0020] Step S1: Install the connector to the end of the marine flexible pipeline, install at least one set of vent valves inside the connector, connect the optical fiber in series with two of the first gratings, the second grating and the third grating to form a fiber optic grating, connect the fiber optic grating to the armored optical cable through an underwater connector, and connect the demodulator to the demodulator through the armored optical cable, and connect the demodulator to the computer through the armored optical cable.

[0021] Step S2: Gas in the annular region of the marine flexible pipeline enters the exhaust valve through the air inlet and then enters the cavity formed by the valve core and the valve body through the notch of the guide cone structure. When the gas pressure is greater than the sum of the valve core spring pressure and the seawater pressure, the valve core moves upward and the exhaust valve opens; when the gas pressure is less than the sum of the valve core spring tension and the seawater pressure, the valve core moves downward and the exhaust valve closes. The opening / closing action of the valve core causes the conical nut to move up and down. During the up and down movement of the conical nut, the elastic steel strip is compressed and deformed. The first grating, which is evenly distributed on the inner surface of the bent elastic steel strip, undergoes synchronous strain with the elastic steel strip. The strain of the first grating causes a change in its transmission wavelength, which is demodulated by the demodulator to monitor the position status of the exhaust valve.

[0022] Step S3: The gas pressure inside the exhaust valve causes strain in the diaphragm within the membrane cover cavity, positioning the second grating at the center of the diaphragm and fixing it with colloid. The third grating is arranged radially in the diaphragm, with one end fixed. Its strain is only related to the ambient temperature, thus providing temperature compensation for the strain of the first, second, and third gratings. Changes in the gas pressure inside the exhaust valve cause deformation of the diaphragm within the membrane cover cavity, resulting in strain in the second grating and a change in the transmission wavelength. This is demodulated by the demodulator, thereby monitoring the gas pressure inside the exhaust valve.

[0023] The beneficial effects of this invention are:

[0024] This invention discloses an exhaust valve and monitoring method suitable for monitoring gas pressure in the annular zone of subsea pipelines. It can monitor the position status of the exhaust valve and the gas pressure in the annular zone in real time, providing guidance for the maintenance of exhaust valves in flexible marine pipelines. This avoids damage to the pipeline structure caused by gas pressure exceeding design values ​​in the annular zone due to blockage of the exhaust valve, thus improving the safety and reliability of flexible marine pipeline operation. The guide cone structure, matched with a cone nut, prevents valve core tilting, improving testing accuracy. Fiber optic grating sensing technology effectively enhances the monitoring accuracy of the exhaust valve's position status and the gas pressure in the annular zone, while also exhibiting high corrosion resistance and electromagnetic interference resistance.

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the exhaust valve structure according to a preferred embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the connection of a gas pressure monitoring system for a subsea pipeline annular zone, according to a preferred embodiment of the present invention.

[0028] The components in the attached diagram are labeled as follows: 1. Valve core; 2. Conical nut; 3. Guide conical structure; 4. Fixing shoe; 5. Fixing shoe spring; 6. Guide circular plate; 7. Elastic steel strip; 8. First grating; 9. Optical fiber; 10. Valve body; 11. Diaphragm cover; 12. Sealing interface; 13. First sealing ring; 14. Second grating; 15. Third grating; 16. Second sealing ring; 17. Valve bottom cover; 18. Valve core spring; 19. Pressure cap; 20. Air inlet; 21. Exhaust port; 22. Limiting block; 23. Computer; 24. Demodulator; 25. Armored optical cable; 26. Underwater connector; 27. Exhaust valve; 28. Joint; 29. ​​Marine flexible pipeline. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figure 1As shown, an exhaust valve suitable for gas pressure monitoring in a subsea pipeline annular zone includes a valve core 1, a guide cone structure 3, a fixing shoe 4, an elastic steel strip 7, an optical fiber 9, a first grating 8, a second grating 14, a third grating 15, and a valve body 10. The valve body 10 is fixedly connected to the guide cone structure 3 by threads. A valve bottom cover 17 is installed at the bottom of the valve body 10, and air inlets 20 are provided on both sides of the valve bottom cover 17. An optical fiber 9 is embedded in a groove pre-set on the inner wall of the valve body 10 through a colloid. A valve core spring 1 is provided on the outer wall of a portion of the hollow cavity of the valve core 1 within the valve body 10. 8. A limiting block 22 is installed on the side of the valve core 1 near the exhaust port 21. A second sealing ring 16 is installed on the upper part of the limiting block 22. A pressure cap 19 is installed on the second sealing ring 16 through a fastening nut. The taper of the conical nut 2 matches the taper of the guide conical structure 3. There is an equidistant gap between the conical surface of the conical nut 2 and the conical surface of the guide conical structure 3 to allow the conical nut 2 to move up and down. The guide conical structure 3 is coaxial with the conical nut 2 and has a notch symmetrically arranged along the diameter direction at the axis. The inner wall of the notch of the guide conical structure 3 is embedded with a symmetrically arranged notch along the axis of the valve core 1. The system includes two sets of fixed boots 4, each containing a fixed boot spring 5 and an arc-shaped elastic steel strip 7. The elastic steel strip 7 is fixedly connected to the inner wall of the fixed boot 4 via guide plates 6 at both ends. The curved inner surface of the elastic steel strip 7 is evenly distributed with first gratings 8, which are fixedly connected to the optical fiber 9 via an adhesive. The adhesive used to embed the optical fiber 9 is a flexible adhesive. The two sets of first gratings 8 are connected in series with the optical fiber 9. A conical nut 2 is connected to the lower end of the valve core 1, and the conical nut 2 is connected to the diaphragm cover 11 via threads. The diaphragm cover 11... Each end is threaded with a first sealing ring 13, and each first sealing ring 13 is provided with a sealing interface 12 to facilitate the exit of the optical fiber 9. A diaphragm is disposed inside the cavity of the membrane cover 11, and a second grating 14 and a third grating 15 are evenly distributed on the inner surface of the membrane cover 11. One end of the second grating 14 is fixed to the radial direction of the diaphragm, and the third grating 15 is fixed to the center of the diaphragm by an adhesive. The adhesive used to fix the first grating 8, the second grating 14, and the third grating 15 is a rigid adhesive. The second grating 14 and the third grating 15 are connected in series with the optical fiber 9 through the sealing interface 12.

[0031] like Figure 2 As shown, the method for monitoring gas pressure in the annular zone of a subsea pipeline includes the following steps:

[0032] The connector 28 is installed at the end of the marine flexible pipeline 29. At least one set of exhaust valves 27 is installed inside the connector 28. The optical fiber 9 is connected in series with two first gratings 8, a second grating 14 and a third grating 15 to form a fiber optic grating. The fiber optic grating is connected to the armored optical cable 25 through the underwater connector 26 and to the demodulator 24 through the armored optical cable 25. The demodulator 24 is connected to the computer 23 through the armored optical cable 25.

[0033] Gas in the annular region of the marine flexible pipeline 29 enters the exhaust valve 27 through the air inlet 20 and enters the cavity formed by the valve core 1 and the valve body 10 through the notch of the guide cone structure 3. When the gas pressure is greater than the sum of the valve core spring pressure and the seawater pressure, the valve core 1 moves upward and the exhaust valve 27 opens; when the gas pressure is less than the sum of the valve core spring tension and the seawater pressure, the valve core 1 moves downward and the exhaust valve 27 closes. The opening / closing action of the valve core 1 causes the cone nut 2 to move up and down. During the up and down movement of the cone nut 2, it squeezes the elastic steel strip 7, causing it to deform. The first grating 8, which is evenly distributed on the inner surface of the bent elastic steel strip 7, undergoes synchronous strain with the elastic steel strip 7. The strain of the first grating 8 causes its transmission wavelength to change, which is demodulated by the demodulator 24 to monitor the position status of the exhaust valve 27.

[0034] The gas pressure inside the exhaust valve 27 causes strain in the diaphragm inside the membrane cover 11 cavity, positioning the second grating 14 at the center of the diaphragm and fixing it with colloid. The third grating 15 is arranged in the radial direction of the diaphragm and is fixed at one end. Its strain is only related to the ambient temperature, thus providing temperature compensation for the strain of the first grating 8, the second grating 14, and the third grating 15. When the gas pressure inside the exhaust valve 27 changes, the diaphragm inside the membrane cover 11 cavity deforms, causing strain in the second grating 14 and a change in the transmission wavelength. This change is demodulated by the demodulator 24, thereby monitoring the gas pressure inside the exhaust valve 27.

[0035] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An exhaust valve suitable for gas pressure monitoring in the annular zone of a subsea pipeline, characterized in that, The valve body includes a valve core (1), a guide cone structure (3), a fixing shoe (4), an elastic steel strip (7), an optical fiber (9), a first grating (8), a second grating (14), a third grating (15), and a valve body (10). The valve body (10) is fixedly connected to the guide cone structure (3) by threads. A valve bottom cover (17) is installed at the bottom of the valve body (10). Air inlets (20) are provided on both sides of the valve bottom cover (17). The optical fiber (9) is embedded in a groove pre-set in the inner wall of the valve body (10) by colloid. A valve core spring (18) is provided on the outer side of the valve core (1) located in the hollow cavity of the valve body (10). A limit block (22) is installed on the side of the valve core (1) near the exhaust hole (21). A second sealing ring (16) is installed on the upper part of the limit block (22). A pressure cap (19) is installed on the upper part of the second sealing ring (16) by fastening nuts. The guide cone structure (3) is coaxial with the cone nut (2) and has a notch symmetrically arranged about the axis along the diameter direction. The inner wall of the notch of the guide cone structure (3) is embedded with the fixing shoe (4) symmetrically arranged about the axis of the valve core (1). There are two sets of fixing shoes (4). Each fixing shoe (4) is provided with a fixing shoe spring (5). Each fixing shoe (4) is provided with an arc-shaped elastic steel strip (7). The elastic steel strip (7) is fixedly connected to the inner wall of the fixing shoe (4) by the guide circular plates (6) provided at both ends. The curved inner surface of the elastic steel strip (7) is evenly provided with the first grating (8) fixedly connected to the optical fiber (9) by the colloid. The two sets of first gratings (8) are connected in series with the optical fiber (9). The lower end of the valve core (1) is connected to a conical nut (2), which is connected to the diaphragm cover (11) by threads. Both ends of the diaphragm cover (11) are fitted with first sealing rings (13) by threads. Each of the first sealing rings (13) is provided with a sealing interface (12) that satisfies the output of the optical fiber (9). A diaphragm is provided in the cavity of the diaphragm cover (11). The second grating (14) and the third grating (15) are evenly distributed on the inner surface of the diaphragm cover (11). One end of the second grating (14) is fixed in the radial direction of the diaphragm, and the third grating (15) is fixed to the center of the diaphragm by colloid. The second grating (14) and the third grating (15) are connected in series with the optical fiber (9) by passing through the sealing interface (12).

2. The exhaust valve for gas pressure monitoring in the annular zone of a subsea pipeline according to claim 1, characterized in that, The taper of the conical nut (2) matches the taper of the guide conical structure (3), and there is an equidistant gap between the conical surface of the conical nut (2) and the conical surface of the guide conical structure (3) to satisfy the up-and-down movement of the conical nut (2).

3. The exhaust valve for gas pressure monitoring in the annular zone of a subsea pipeline according to claim 1, characterized in that, The colloid used to embed the optical fiber (9) is a flexible colloid; the colloid used to fix the first grating (8), the second grating (14), and the third grating (15) is a rigid colloid.

4. A method for monitoring gas pressure in a subsea pipeline annular zone, employing an exhaust valve as described in claims 1-3, characterized in that: The method for monitoring gas pressure in a subsea pipeline annular zone includes the following steps: Step S1: Install the connector (28) to the end of the marine flexible pipeline (29), install at least one set of exhaust valves (27) inside the connector (28), connect the optical fiber (9) in series with the two first gratings (8), the second grating (14) and the third grating (15) to form a fiber optic grating, connect the fiber optic grating to the armored optical cable (25) through the underwater connector (26), and connect it to the demodulator (24) through the armored optical cable (25). The demodulator (24) is connected to the computer (23) through the armored optical cable (25). Step S2: Gas in the annular region of the marine flexible pipeline (29) enters the interior of the exhaust valve (27) through the air inlet (20) and enters the cavity formed by the valve core (1) and the valve body (10) through the notch of the guide cone structure (3). When the gas pressure is greater than the sum of the valve core spring pressure and the seawater pressure, the valve core (1) moves upward and the exhaust valve (27) opens; when the gas pressure is less than the sum of the valve core spring tension and the seawater pressure, the valve core (1) moves downward and the exhaust valve (27) opens. 27) Close; the opening / closing action of the valve core (1) is linked to the up-and-down movement of the conical nut (2). During the up-and-down movement of the conical nut (2), the elastic steel strip (7) is squeezed and deformed; the first grating (8) evenly distributed on the inner surface of the bent elastic steel strip (7) undergoes synchronous strain with the elastic steel strip (7); the strain of the first grating (8) causes its transmission wavelength to change, which is demodulated by the demodulator (24) to monitor the position status of the exhaust valve (27); Step S3: The gas pressure inside the exhaust valve (27) causes the diaphragm in the cavity of the membrane cover (11) to strain, so that the second grating (14) is located at the center of the diaphragm and fixed by the colloid. The third grating (15) is arranged in the radial direction of the diaphragm. The third grating (15) is fixed at one end, and its strain is only related to the ambient temperature. Therefore, temperature compensation is performed on the strain of the first grating (8), the second grating (14) and the third grating (15). The gas pressure inside the exhaust valve (27) changes, and the diaphragm in the cavity of the membrane cover (11) deforms, causing the second grating (14) to strain. The transmission wavelength changes, and demodulation is performed by the demodulator (24) to monitor the gas pressure inside the exhaust valve (27).

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