Shape memory alloy self-sealing gasket

Abstract

This invention discloses a shape memory alloy self-sealing gasket, belonging to the field of sealing technology. It includes an annular corrugated upper skeleton, a flexible graphite covering layer, multiple support gaskets of different diameters, and an annular corrugated lower skeleton. The annular corrugated upper and lower skeletons are stacked vertically to form a gap. The support gaskets are fixed between the two skeletons and have circumferentially misaligned openings. The outer circumferences of both skeletons are welded closed and connected to positioning rings. The flexible graphite covering layer covers the outer surfaces of both skeletons and has a smooth surface. A wired pressure sensing module is embedded within the flexible graphite covering layer and is connected to an external power supply and signal receiving module via a high-temperature resistant insulated lead. This invention maintains gap stability through the support gaskets, ensuring that the medium pressure is converted into axial compensating stress to compensate for preload attenuation. The pressure sensing module is adapted to high-temperature and high-pressure sealing conditions, accurately collecting gasket compressive stress data, achieving real-time monitoring of the sealing status, and improving overall sealing reliability and adaptability to operating conditions.

Description

Technical Field

[0001] This invention relates to the field of sealing technology, and in particular to a shape memory alloy self-sealing gasket. Background Technology

[0002] Complex operating conditions such as high pressure (nominal pressure ≥ PN40), high-temperature cycling (-40℃~550℃), load fluctuations, and media corrosion place comprehensive demands on gaskets, requiring them to "resist extreme conditions, resist preload decay, prevent media leakage, and enable condition monitoring." Existing gaskets have the following problems: Firstly, the preload reduction compensation capability is insufficient, and the corrugated gaps are prone to closure and failure. Most existing corrugated gaskets use a single-piece skeleton structure, with gaps between adjacent corrugations intended to enhance elasticity. However, under bolt preload, these gaps are easily squeezed shut, preventing the flow of medium pressure to be converted into axial compensating stress. This forces the gasket to rely solely on the initial preload for sealing. When the system experiences thermal expansion and contraction, or long-term load creep, the preload continuously decreases, and the gasket lacks an effective compensation mechanism, leading to micron-level gaps on the sealing surface and causing leakage. Some gaskets attempt to add support structures, but these are mostly external designs, compromising the integrity of the corrugated structure and failing to reliably fit with the skeleton, still making it difficult to stably maintain the gap width.

[0003] Secondly, they lack intelligent monitoring capabilities adapted to complex operating conditions, making it impossible to predict the sealing status. Most existing gaskets are passive sealing structures, unable to detect real-time changes in sealing surface pressure, preload decay, and gap blockage. Maintenance personnel can only maintain them through periodic shutdowns for inspection or remedial measures after leaks occur, increasing maintenance costs and potentially causing system shutdowns due to sudden leaks. Some gaskets with integrated sensing functions have large sensing elements that require external power supply wiring, easily interfering with the sealing structure and unable to withstand high-temperature and high-pressure conditions.

[0004] Third, the material and structure have poor compatibility and are not suitable for extreme working conditions. Traditional gasket materials either have poor temperature resistance (such as high-temperature aging and low-temperature brittleness of rubber gaskets) or insufficient elasticity (such as graphite gaskets that rely on preload and have no active compensation capability). Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a shape memory alloy self-sealing gasket that solves the problems of insufficient preload attenuation compensation and easy closure failure of corrugated gaps. At the same time, it integrates a wired power supply pressure sensing module to achieve accurate and real-time monitoring of the pressure stress on the sealing surface under high temperature and high pressure conditions, thereby improving the operational safety of the sealing system.

[0006] The technical solution of this invention is as follows: A shape memory alloy self-sealing gasket includes an annular corrugated upper skeleton, multiple support washers of different diameters, an annular corrugated lower skeleton, and a flexible graphite covering layer. The annular corrugated upper skeleton and the annular corrugated lower skeleton are stacked vertically and form a gap. The support washers are fixedly connected between the annular corrugated upper skeleton and the annular corrugated lower skeleton. The support washers have openings for the working fluid to pass through between the annular corrugated upper skeleton and the annular corrugated lower skeleton. The outer periphery of the annular corrugated upper skeleton and the annular corrugated lower skeleton are welded closed. The annular corrugated upper skeleton, the support washers, and the annular corrugated lower skeleton are made of the same shape memory alloy material. The flexible graphite covering layer covers the outer surface of the annular corrugated upper skeleton and the annular corrugated lower skeleton and has a smooth surface. A pressure sensing module is embedded in the flexible graphite covering layer. The pressure sensing module is connected to an external power supply and signal receiving module through a high-temperature resistant insulated lead wire.

[0007] Furthermore, the corrugations of the upper and lower annular corrugated skeletons are arranged correspondingly, and the support washer is disposed at the crest or trough of the corrugations.

[0008] Furthermore, the support washer is bonded and fixed to the upper annular corrugated skeleton and the lower annular corrugated skeleton.

[0009] Furthermore, the support washer is axially pre-compressed, and its thickness increases as the temperature rises.

[0010] Furthermore, the openings of the plurality of support washers are located at different positions in the circumferential direction.

[0011] Furthermore, the gap width between the upper annular corrugated skeleton and the lower annular corrugated skeleton is 0.3 to 0.8 mm.

[0012] Furthermore, positioning rings are fixedly connected to the outer periphery of the upper and lower annular corrugated skeletons. These positioning rings are used for precise matching with the flange sealing groove, ensuring accurate installation and positioning of the gasket at the flange and preventing sealing failure due to assembly misalignment.

[0013] Furthermore, the pressure sensing module includes a high-temperature SOI stress chip, a high-temperature resistant buffer filler, and a fully encapsulated high-temperature insulating layer. The high-temperature resistant buffer filler fills the outer periphery of the high-temperature SOI stress chip, and the fully encapsulated high-temperature insulating layer covers the high-temperature resistant buffer filler and the high-temperature SOI stress chip. One end of the high-temperature resistant insulating lead is electrically connected to the high-temperature SOI stress chip, and the other end extends out to a flexible graphite cover layer to connect to the power supply and signal receiving module.

[0014] Furthermore, pressure sensing modules are provided within the flexible graphite covering layer on the outer surface of both the annular corrugated upper skeleton and the annular corrugated lower skeleton.

[0015] Furthermore, the shape memory alloy is a Ni-Ti based shape memory alloy.

[0016] Compared with the prior art, the advantages of the technical solution provided by the present invention are as follows: The support gasket ensures a stable gap between the upper and lower annular corrugated skeletons, preventing the gap opening (inner circumferential side) from closing after the sealing gasket is pre-tightened. This ensures that the medium pressure is stably converted into axial compensating stress, effectively compensating for pre-tightening force attenuation. It is suitable for high-temperature cycling and load fluctuation conditions, significantly improving sealing reliability. The pressure sensing module is adapted to high-temperature and high-pressure sealing conditions, accurately collecting gasket compressive stress data for real-time monitoring of the sealing status, enhancing overall sealing reliability and adaptability to operating conditions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a single-side cross-sectional structure of the shape memory alloy self-sealing gasket used in this embodiment.

[0018] Figure 2 This is a top view schematic diagram of the support ring configuration of the shape memory alloy self-sealing gasket in an embodiment.

[0019] Figure 3 for Figure 1 A partial structural diagram at point A. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments.

[0021] This invention provides a shape memory alloy self-sealing gasket adapted to DN100 PN40 flanges and used in high-temperature heat transfer oil pipelines for concentrated solar power generation. Please refer to... Figure 1 and Figure 2 As shown, its structure includes an annular corrugated upper skeleton 1, a support washer 3, an annular corrugated lower skeleton 4, a flexible graphite covering layer 2, and a pressure sensing module 5.

[0022] Both the upper annular corrugated skeleton 1 and the lower annular corrugated skeleton 4 are made of Ni-Ti based shape memory alloy. The corrugations of the two are arranged correspondingly, and a corrugated gap channel is formed between the upper annular corrugated skeleton 1 and the lower annular corrugated skeleton 4. The design width of the corrugated gap channel is W=0.5mm (suitable for DN100 PN40 flange specifications).

[0023] After being joined, the outer periphery of the upper annular corrugated frame 1 and the lower annular corrugated frame 4 are welded together to form the upper and lower frame welding parts 6. The upper and lower frame welding parts 6 seal the outer periphery of the corrugated gap channel to prevent the medium from leaking from the outer periphery.

[0024] Positioning rings 7 are welded to the outer periphery of the upper annular corrugated frame 1 and the lower annular corrugated frame 4. The positioning rings 7 are made of 304 stainless steel by stamping. Their outer diameter is precisely matched with the flange sealing groove. The coaxiality error between the positioning rings 7 and the upper annular corrugated frame 1 and the lower annular corrugated frame 4 is ≤0.02mm, which realizes the precise installation and positioning of the gasket at the flange and avoids sealing failure caused by assembly misalignment.

[0025] The support washer 3 is made of Ni-Ti based shape memory alloy, using the same material as the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 4. The support washer 3 has an axial thickness of 0.5 mm and an opening 3a width of 0.5 mm. The support washer 3 is positioned between the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 4, specifically bonded and fixed to them using high-temperature ceramic adhesive dots. Multiple support washers 3 are located at the crests and troughs of the corrugated shape of the annular corrugated upper skeleton 1. Each support washer 3 has an opening 3a, meaning the support washer 3 is not a complete ring, and the openings 3a of each support washer 3 are distributed at different circumferential positions. The medium can enter the corrugated gap channel between the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 4 through the openings 3a. The medium is evenly distributed in the corrugated gap channel, providing a stable and uniform medium pressure basis for self-sealing compensation. The support washer 3 can offset the compression of the double corrugated structure by the bolt preload, prevent the corrugated gap channel from failing to close, and always maintain space for medium pressure conversion, ensuring the continuous realization of the self-sealing compensation function. The support washer 3 is made of the same material as the upper annular corrugated skeleton 1 and the lower annular corrugated skeleton 4, and the coefficient of thermal expansion is perfectly matched, avoiding gap loosening or corrugated structure cracking caused by deformation differences under high and low temperature cycling.

[0026] A flexible graphite coating layer 2 is applied to the outer surfaces of the upper annular corrugated frame 1 and the lower annular corrugated frame 4. The flexible graphite coating layer 2 is made of high-purity flexible graphite and is tightly wrapped around the upper annular corrugated frame 1 and the lower annular corrugated frame 4 through a molding process to form the outer surface of the gasket. The flexible graphite coating layer 2 has a flat surface to fit tightly with the flange sealing surface to achieve the initial seal between the gasket and the flange.

[0027] A pressure sensing module 5 is provided within the flexible graphite covering layer 2, and pressure sensing modules 5 are arranged on the outer surfaces of the flexible graphite covering layer 2 of the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 4. As a preferred embodiment, multiple pressure sensing modules 5 can be evenly distributed around the circumference of the gasket to achieve full-area coverage monitoring of the gasket's compressive stress.

[0028] like Figure 3 As shown, the pressure sensing module 5 includes a high-temperature SOI compressive stress chip 5a, a high-temperature resistant buffer filler 5b, a fully encapsulated high-temperature insulation layer 5c, and a high-temperature resistant insulated lead wire 5d. The functions of each component are as follows: High-Temperature SOI Stress Chip 5a: Utilizing the CETC-SOI-P100 industrial-grade mature sheet-like SOI stress chip from the 13th Research Institute of China Electronics Technology Group Corporation (CETC), this chip serves as the core element for stress sensing. It employs a sheet-like structure fabricated using a sputtering thin-film process, with a chip thickness of only 0.2mm. This allows for compact sandwich embedding with a flexible graphite coating, measuring stress from 0 to 100 MPa with an accuracy of 0.5 grade. It withstands a wide temperature range of -40℃ to 550℃. The metallurgically bonded thin-film structure ensures long-term stability. It directly senses the stress on the gasket, capturing changes in stress values ​​and localized stress distribution during flange pre-tightening and operational processes. This accurately reflects the attenuation of axial pre-tightening force and uneven stress distribution, providing direct and reliable stress data for sealing condition assessment. The chip is compatible with high-temperature heat transfer oil, steam, and other industrial media, perfectly matching the operating environment of the gasket in this invention.

[0029] High-temperature resistant buffer filler 5b: Filled around the high-temperature SOI compressive stress chip 5a, it is made of high-temperature corrosion resistant inorganic adhesive. It can buffer the mechanical stress caused by flange pre-tightening and working condition deformation, avoid chip damage by compression, and improve the chip's resistance to media corrosion. Fully encapsulated high-temperature insulation layer 5c: Made of high-temperature resistant ceramic insulating material, it covers the outside of high-temperature resistant buffer filler 5b and high-temperature SOI compressive stress chip 5a. It has good insulation properties, avoids signal interference caused by contact with the graphite layer, and improves the sensing module's high temperature resistance, high pressure resistance and corrosion resistance. High-temperature resistant insulated lead 5d: It adopts a high-temperature resistant polyimide insulated wire, one end of which is electrically connected to the signal end and power supply end of the high-temperature SOI compressive stress chip 5a, and the other end extends out to the flexible graphite cover layer 2, which connects to the external matching power supply and signal receiving module to realize stable wired power supply and compressive stress data transmission, with an effective transmission distance ≥10m and a response time ≤2s.

[0030] The pressure sensing module 5 is fixed within the flexible graphite cover layer 2 using high-temperature corrosion-resistant adhesive. This accommodates the micro-deformation of the structure caused by flange pre-tightening and thermal expansion and contraction, ensuring the continuity and accuracy of compressive stress acquisition. The flexible graphite cover layer 2 serves as the medium for transmitting the compressive stress of the gasket, transferring the stress without loss to the high-temperature SOI compressive stress chip 5a within the cover layer, ensuring the accuracy of compressive stress monitoring.

[0031] The processing method for shape memory alloy self-sealing gaskets is as follows: Ni-Ti based shape memory alloy sheet is cut and corrugated to obtain annular corrugated upper skeleton 1 and annular corrugated lower skeleton 4. Ni-Ti based shape memory alloy bar is precision turned and wire cut to form annular structure with opening 3a. The inner and outer diameters and end faces are polished to ensure axial thickness tolerance of ±0.005mm and opening 3a width tolerance of ±0.01mm, thus obtaining support washer 3.

[0032] The support washer 3 is fixed to the corrugated gap channel between the upper annular corrugated frame 1 and the lower annular corrugated frame 4 using high-temperature ceramic adhesive spot bonding. The support washer 3 forms multiple fixed connection points with both the upper and lower annular corrugated frames 1 and 4, rather than a complete circumferential seal. The upper and lower annular corrugated frames 1 and 4 are aligned to ensure corresponding corrugations. After alignment, the outer edges are processed using laser welding to form the upper and lower frame welded parts 6. Weld inspection is performed to ensure the weld is free of defects such as porosity and cracks. A positioning ring 7, made of 304 stainless steel sheet, is stamped into an annular structure. The welding end face is ground to ensure a flatness ≤0.01mm. The positioning ring 7 is fitted onto the outer periphery of the upper and lower annular corrugated frames 1 and 4, and fixed using laser spot welding. After welding, coaxiality is checked to ensure that flange assembly requirements are met. The high-temperature SOI compressive stress chip 5a, high-temperature resistant buffer filler 5b, fully encapsulated high-temperature insulation layer 5c, and high-temperature resistant insulated lead wire 5d are assembled into an integrated pressure sensing module 5. The debugging module 5 ensures stable power supply and signal transmission. The flexible graphite roll is pre-molded in three layers, with a reserved interlayer for the sensing module 5 in the middle layer. The assembled sensing module 5 is embedded in the designated position of the interlayer, fixed with high-temperature corrosion resistant adhesive, and the electrical connection parts are sealed and protected.

[0033] The prefabricated and integrated pressure sensing module 5 flexible graphite cover layer 2 is tightly covered on the outer surface of the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 4 through a molding process, and the molding pressure is controlled at 5MPa.

[0034] The flexible graphite cover layer 2, which is prefabricated and integrates the wireless pressure sensing module 4, is tightly covered on the outer surface of the annular corrugated upper skeleton 1 and the annular corrugated lower skeleton 5 through a molding process, with the molding pressure controlled at 5MPa.

[0035] After the gasket of the present invention is assembled at the DN100 PN40 flange and the bolts are pre-tightened, the support washer 3 effectively counteracts the bolt pre-tightening force, maintains the stability of the double corrugated gap width, and evenly disperses the initial compressive stress on the gasket to avoid local stress concentration. The flexible graphite covering layer 2 is tightly attached to the flange sealing surface to achieve initial sealing, and transmits the compressive stress on the gasket to the interlayer pressure sensing module 5 without loss.

[0036] After the gasket of the present invention is assembled at the DN100 PN40 flange and the bolts are pre-tightened, the support washer 3 effectively counteracts the bolt pre-tightening force, maintains the stability of the double corrugated gap width, and evenly disperses the initial compressive stress on the gasket to avoid local stress concentration. The flexible graphite covering layer 2 is tightly fitted to the flange sealing surface to achieve initial sealing, and the compressive stress on the gasket is transferred without loss to the high-temperature SOI compressive stress chip 5a of the pressure sensing module 5 in the interlayer. The high-temperature resistant insulated lead 5d is connected to the external matching power supply and signal receiving module 8 to provide a stable wired power supply for the pressure sensing module 5.

[0037] Under normal operating conditions, the high-temperature heat transfer oil medium enters the double corrugated gap along the corrugated trough channel and fills the entire gap channel through the opening 3a of the support gasket 3. The medium pressure is converted into axial compensation stress, which dynamically compensates for the attenuation of the bolt preload and ensures that the compressive stress on the gasket is always maintained within the reasonable range required for sealing. The pressure sensing module 5, integrated in the interlayer of the flexible graphite covering layer 2, directly and in real time collects the compressive stress data on the gasket through the high-temperature SOI compressive stress chip 5a, and transmits the compressive stress value and distribution status to the external receiving signal module 8 through the high-temperature resistant insulating lead 5d.

[0038] When the system experiences thermal expansion and contraction, and load creep leading to a decrease in bolt preload, the compressive stress on the gasket will decrease synchronously. When the compressive stress is detected to be lower than the sealing threshold, or when there is significant unevenness in local compressive stress (difference ≥ 5 MPa), the background system will quickly issue an early warning, and maintenance personnel can take timely countermeasures to avoid media leakage caused by insufficient or uneven distribution of compressive stress, effectively improving the safety and long-term stability of the solar thermal power generation pipeline system.

[0039] The present invention can be adapted to other working conditions in the following ways: Adaptable to different flange specifications: For flanges of different specifications such as DN50 and DN200, the dimensions of the upper annular corrugated skeleton 1 and the lower annular corrugated skeleton 4, the number and spacing of the support gaskets 3 can be flexibly adjusted. At the same time, the number of pressure sensing modules 5 in the flexible graphite covering layer 2 can be adjusted accordingly to maintain the pressure monitoring effect.

[0040] Adaptable to highly corrosive media scenarios: For highly corrosive scenarios such as acid and alkali media, hydrocracking process media, Hastelloy plating can be applied to the surfaces of the upper skeleton 1, the lower skeleton 4, and the support washer 3 of the annular corrugated wire, with a plating thickness of 0.02 to 0.05 mm; at the same time, the exposed end of the high-temperature resistant insulated lead 5d is treated with anti-corrosion sealing.

[0041] Ultra-high temperature operating conditions: For ultra-high temperature operating conditions of ≥500℃, the flexible graphite cover layer 2 is made of high-purity molded graphite material, and the high-temperature insulation layer 5c of the pressure sensing module 5 is fully encapsulated with high temperature reinforcement to ensure the monitoring accuracy and stability of the high-temperature SOI compressive stress chip 5a under extreme high temperature conditions.

Claims

1. A shape memory alloy self-sealing gasket, characterized in that, The device includes an annular corrugated upper skeleton, multiple support washers of different diameters, an annular corrugated lower skeleton, and a flexible graphite covering layer. The annular corrugated upper skeleton and the annular corrugated lower skeleton are stacked one on top of the other, forming a gap. The support washers are fixedly connected between the annular corrugated upper skeleton and the annular corrugated lower skeleton, and each support washer has an opening for the medium to pass through between the annular corrugated upper skeleton and the annular corrugated lower skeleton. The outer peripheries of the annular corrugated upper skeleton and the annular corrugated lower skeleton are welded to form upper and lower skeleton welded parts and then closed. The annular corrugated upper skeleton, the support washers, and the annular corrugated lower skeleton are all made of the same shape memory alloy material. The flexible graphite covering layer covers the outer surfaces of the annular corrugated upper skeleton and the annular corrugated lower skeleton and has a smooth surface. A pressure sensing module is embedded in the flexible graphite covering layer, and the pressure sensing module is connected to an external power supply and signal receiving module through a high-temperature resistant insulated lead wire.

2. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The upper and lower annular corrugated skeletons are arranged with their corrugations corresponding to each other, and the support washer is located at the crest or trough of the corrugations.

3. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The support washer is bonded and fixed to the upper annular corrugated skeleton and the lower annular corrugated skeleton.

4. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The support washer is axially pre-compressed, and its thickness increases as the temperature rises.

5. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The openings of the multiple support washers are located at different positions in the circumference.

6. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The gap width between the upper and lower annular corrugated skeletons is 0.3 to 0.8 mm.

7. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, Positioning rings are fixedly connected to the outer periphery of the upper and lower annular corrugated skeletons.

8. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The pressure sensing module includes a high-temperature SOI stress chip, a high-temperature resistant buffer filler, and a fully encapsulated high-temperature insulating layer. The high-temperature resistant buffer filler fills the outer periphery of the high-temperature SOI stress chip, and the fully encapsulated high-temperature insulating layer covers the high-temperature resistant buffer filler and the high-temperature SOI stress chip. One end of the high-temperature resistant insulating lead is electrically connected to the high-temperature SOI stress chip, and the other end extends out to a flexible graphite cover layer to connect to the power supply and signal receiving module.

9. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, Pressure sensing modules are provided within the flexible graphite covering layer on the outer surface of both the annular corrugated upper skeleton and the annular corrugated lower skeleton.

10. The shape memory alloy self-sealing gasket according to claim 1, characterized in that, The shape memory alloy is a Ni-Ti based shape memory alloy.

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