A backflow prevention sealing type one-way shut-off device

Abstract

This utility model relates to the field of downhole tools technology for oilfield operations, and discloses an anti-backflow sealing one-way shut-off device, including a shell, a ball seat, a fixed cylinder, a spring seat, a steel ball, a preload spring, and a preload force adjustment mechanism. The ball seat is installed on the inner wall of the flow channel, the fixed cylinder is fixed to the bottom of the flow channel, the spring seat is slidably installed in the fixed cylinder, the steel ball is installed on the top of the spring seat and cooperates with the through groove of the ball seat, the preload spring is placed in the second inner cavity of the spring seat and its top end abuts against it, and the preload force adjustment mechanism is located in the fixed cylinder and abuts against the bottom end of the spring. In the above solution, by embedding the preload spring inside the spring seat, the spring is shielded by the side wall, avoiding erosion by sand-containing media, enhancing the erosion resistance, and significantly improving the service life of the device. The preload force adjustment mechanism can steplessly adjust the initial preload force to meet different opening pressure requirements and can compensate for spring attenuation, extending the service life. The device has a compact structure and reliable sealing.

Description

Technical Field

[0001] This utility model relates to the field of downhole tools technology for oil well operations, and more specifically, to an anti-backflow sealing one-way shut-off device. Background Technology

[0002] In well workover operations in the petroleum industry, processes such as well washing, sand flushing, and water injection all require the media in the downhole tubing to flow in one direction to prevent backflow of formation fluids, kill fluids, or sand-containing fluids when the pump stops or pressure fluctuates, thus avoiding damage to surface equipment, tubing, and reservoirs. Therefore, the anti-backflow sealing one-way shut-off device is a key control component in the downhole tubing, and its sealing reliability and service life directly affect operational safety and construction efficiency.

[0003] Currently, commonly used one-way shut-off devices generally consist of a main body, a ball seat, a steel ball, and a spring. When the fluid flows in the forward direction, the fluid pressure pushes the steel ball away from the ball seat, overcoming the spring force, creating a flow gap that allows the medium to pass through. When reverse flow occurs, the steel ball, under the combined action of the spring force and the reverse fluid pressure, presses against the sealing surface of the ball seat, preventing backflow of the medium. In addition, there are also downhole check valve solutions in the existing technology that do not require springs, such as using the valve core's own weight to achieve reset, or using a hemispherical valve structure with a centralizing rod to achieve one-way shut-off; and check valve designs with spring isolation structures, which reduce fluid contact by placing the spring in a specific cavity.

[0004] However, in the aforementioned traditional spring-type structures, the springs are constantly exposed to high-speed flowing mud or kill fluids that often contain solid particles, subjecting them to direct erosion and making them highly susceptible to wear, corrosion, and even breakage. Simultaneously, the sealing surfaces of the steel ball and the ball seat gradually wear down due to continuous erosion, leading to seal failure and backflow of the medium. While spring-free check valve solutions avoid spring erosion, their reliance on gravity or specific flow patterns for reset results in insufficient closure reliability in complex well conditions such as inclined and horizontal wells, limiting their applicability. For existing solutions with spring-isolated structures, the initial preload of the spring is typically set at the factory and cannot be adjusted on-site according to changes in downhole conditions, making it difficult to meet the differentiated opening pressure requirements of various operational processes (such as well washing, sand flushing, and water injection). Furthermore, when the spring's performance deteriorates after long-term use, it cannot be compensated for through adjustment, leading to a shortened effective service life of the device and necessitating complete replacement, increasing operating costs. Utility Model Content

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides an anti-backflow sealing one-way shut-off device to solve the problems in the prior art where the spring is directly exposed to the fluid and is easily eroded and damaged, and the sealing surface fails due to erosion and wear.

[0006] To solve the above technical problems, this utility model provides the following technical solution: a backflow prevention sealing type one-way shut-off device, including a housing, a flow channel is provided through the housing along the axial direction, and a one-way shut-off mechanism is provided in the flow channel; The one-way shut-off mechanism includes a ball seat installed on the inner wall of the flow channel. A through groove is provided axially through the ball seat. A fixed cylinder is fixedly installed on the inner wall at the bottom of the flow channel. A first inner cavity with an upward opening is provided in the fixed cylinder. A spring seat is slidably installed axially on the top of the first inner cavity. A steel ball is installed on the top of the spring seat. The top of the steel ball is in contact with the bottom of the through groove. The bottom of the spring seat is provided with a second inner cavity with the opening facing downward. A pre-tension spring is provided inside the second inner cavity, and the top end of the pre-tension spring abuts against the top end of the second inner cavity. The fixed cylinder is equipped with a preload adjustment mechanism that abuts against the bottom end of the preload spring, which is used to adjust the initial preload of the preload spring.

[0007] The shell and the fixed cylinder are provided with several flow channels along the axial direction for fluid to pass through.

[0008] A sealing ring is provided between the outer wall of the ball seat and the inner wall of the flow channel, and a conical sealing surface that mates with the steel ball is provided at the bottom end of the through groove.

[0009] The preload adjustment mechanism includes a threaded column rotatably mounted at the bottom of the fixed cylinder. The outer wall of the top of the threaded column is provided with external threads. A lifting plate is threaded onto the threaded column through the external threads. The top of the lifting plate abuts against the bottom of the preload spring.

[0010] A limiting ring is fixedly installed on the outer wall of the threaded column, and the bottom of the limiting ring is rotatably connected to the bottom of the first inner cavity.

[0011] The outer edge of the lifting plate is fixedly equipped with an anti-rotation protrusion, and the inner wall of the first inner cavity is provided with a guide groove that slides with the anti-rotation protrusion along the axial direction.

[0012] The inner wall of the flow channel and the outer surface of the spring seat are both provided with a chrome-plated wear-resistant layer.

[0013] The beneficial effects of the above-mentioned technical solution of this utility model are as follows: In the above scheme, by embedding the pre-tightening spring in the second inner cavity of the spring seat, the spring is shielded by the side wall of the spring seat throughout its entire working stroke, effectively isolating the spring from direct erosion by the sand-containing medium, significantly improving the erosion resistance and service life of the device. Compared with the one-way valve scheme that does not require a spring, this device provides a reliable closing force through the spring, ensuring reliable reset of the steel ball even in complex well conditions such as inclined wells and horizontal wells, and the closing sealing performance is not affected by the well inclination.

[0014] The preload adjustment mechanism enables stepless adjustment of the initial preload of the preload spring. It can flexibly adjust the opening pressure according to different downhole processes and compensate for the spring performance decay. It overcomes the defects of existing one-way valves with spring isolation structures, which have fixed preload and cannot be adjusted on-site. This effectively extends the service life of the device and reduces operating costs.

[0015] In addition, the chrome-plated wear-resistant layer on the inner wall of the flow channel and the outer surface of the spring seat further improves the erosion resistance and reduces the sliding friction resistance, ensuring the long-term stable operation of the device in harsh downhole environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the internal structure of the shell of this utility model; Figure 3 This is a schematic diagram of the unidirectional cut-off mechanism of this utility model; Figure 4 This is a schematic diagram of the spring seat structure of this utility model; Figure 5 This is a schematic diagram of the internal structure of the fixed cylinder of this utility model.

[0017] Attached Figure

[0018] 1. Housing; 11. Flow channel; 12. Flow passage; 2. One-way shut-off mechanism; 21. Ball seat; 211. Through groove; 212. Sealing ring; 213. Conical sealing surface; 22. Fixed cylinder; 221. First inner cavity; 222. Guide groove; 23. Spring seat; 231. Second inner cavity; 24. Steel ball; 25. Preload spring; 3. Preload force adjustment mechanism; 31. Threaded column; 311. External thread; 312. Limiting ring; 32. Lifting plate; 321. Anti-rotation protrusion. Detailed Implementation

[0019] To make the technical problems, technical solutions and advantages of this utility model clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0020] As attached Figure 1 To be continued Figure 5As shown, an embodiment of this utility model provides a backflow-proof sealing one-way shut-off device, including a housing 1. A flow channel 11 is axially disposed inside the housing 1. A one-way shut-off mechanism 2 is disposed inside the flow channel 11. The one-way shut-off mechanism 2 opens under positive fluid pressure to open the flow channel 11, and automatically closes under reverse fluid pressure or when the pump stops to cut off the flow channel 11, thereby realizing the one-way shut-off function and preventing backflow of the medium. The one-way shut-off mechanism 2 includes a ball seat 21 installed on the inner wall of the flow channel 11. A through groove 211 is provided axially through the ball seat 21. A fixed cylinder 22 is fixedly installed on the inner wall of the bottom of the flow channel 11. A first inner cavity 221 with an upward opening is provided in the fixed cylinder 22. A spring seat 23 is slidably installed axially on the top of the first inner cavity 221. A steel ball 24 is installed on the top of the spring seat 23. The top of the steel ball 24 is in contact with the bottom of the through groove 211. In the initial state, the preload spring 25 pushes the spring seat 23 upward, so that the steel ball 24 on the top of the spring seat 23 is pressed against the bottom of the through groove 211 of the ball seat 21, forming a normally closed seal state, preventing fluid from passing through when there is no positive pressure. The bottom of the spring seat 23 is provided with a second inner cavity 231 with the opening facing downward. A preload spring 25 is provided inside the second inner cavity 231. The top of the preload spring 25 abuts against the top of the second inner cavity 231. The preload spring 25 is accommodated in the second inner cavity 231, and its upper part is surrounded and shielded by the side wall of the spring seat 23. During the compression and reset process of the preload spring 25, its side is always protected by the spring seat 23, which effectively avoids the direct scouring of the preload spring 25 by the fluid medium. The fixed cylinder 22 is equipped with a preload adjustment mechanism 3 that abuts against the bottom end of the preload spring 25. This mechanism is used to adjust the initial preload of the preload spring 25. By adjusting the initial compression of the preload spring 25, the sealing pressure of the steel ball 24 pressed against the conical sealing surface 213 can be changed, thereby adjusting the opening pressure of the device to adapt to the operational requirements of different well conditions. Furthermore, the effective service life of the preload spring 25 can be extended by compensation adjustment after fatigue occurs.

[0021] See Figures 1 to 2 A plurality of flow channels 12 for fluid passage are provided axially between the housing 1 and the fixed cylinder 22. These flow channels 12 are evenly arranged circumferentially between the outer wall of the fixed cylinder 22 and the inner wall of the housing 1. When the flow is forward, after the steel ball 24 leaves the ball seat 21, the fluid enters the inner cavity of the housing 1 through the gap between the steel ball 24 and the ball seat 21, and then flows to the downstream outlet of the housing 1 through the flow channels 12, providing the fluid with an outlet channel that bypasses the internal components of the fixed cylinder 22, ensuring smooth flow.

[0022] See Figure 3A sealing ring 212 is provided between the outer wall of the ball seat 21 and the inner wall of the flow channel 11. The bottom end of the through groove 211 is provided with a conical sealing surface 213 that cooperates with the steel ball 24. The sealing ring 212 is used to prevent fluid from leaking from the assembly gap between the ball seat 21 and the inner wall of the flow channel 11, ensuring that all fluid must flow through the control channel of the through groove 211 and the steel ball 24. The conical sealing surface 213 and the spherical surface of the steel ball 24 form an annular line contact, and a reliable metal-to-metal seal is achieved under the elastic force of the preload spring 25.

[0023] See Figure 5 The preload adjustment mechanism 3 includes a threaded column 31 rotatably mounted at the bottom of the fixed cylinder 22. The outer wall of the top of the threaded column 31 is provided with an external thread 311. A lifting plate 32 is threaded onto the threaded column 31 through the external thread 311. The top of the lifting plate 32 abuts against the bottom of the preload spring 25. When the threaded column 31 is rotated, due to the anti-rotation limit of the lifting plate 32, the lifting plate 32 will move up and down along the axial direction of the threaded column 31. When moving upward, the preload spring 25 is compressed to increase the preload force. When moving downward, the preload spring 25 is released to decrease the preload force, thereby realizing stepless adjustment of the opening pressure of the steel ball 24, which is flexible and convenient to operate.

[0024] See Figure 5 A limiting ring 312 is fixedly installed on the outer wall of the threaded column 31. The bottom of the limiting ring 312 is rotatably connected to the bottom of the first inner cavity 221. The limiting ring 312 abuts against the bottom of the first inner cavity 221 and maintains a stable position when subjected to the axial force transmitted by the preload spring 25. This allows the threaded column 31 to rotate freely around its axis to achieve the adjustment function, while restricting its axial movement, thus ensuring the axial positioning accuracy and working reliability of the adjustment mechanism.

[0025] See Figure 5 An anti-rotation protrusion 321 is fixedly installed on the outer edge of the lifting plate 32. The inner wall of the first inner cavity 221 is provided with a guide groove 222 that slides with the anti-rotation protrusion 321 along the axial direction. The anti-rotation protrusion 321 is embedded in the guide groove 222. The sliding cooperation between the two restricts the circumferential rotational freedom of the lifting plate 32, so that the lifting plate 32 can only move along the axial direction. This accurately converts the rotational motion of the threaded column 31 into the linear displacement of the lifting plate 32, ensuring the accuracy and stability of the preload adjustment.

[0026] The inner wall of the flow channel 11 and the outer surface of the spring seat 23 are both provided with a chrome-plated wear-resistant layer. This chrome-plated layer has the characteristics of high hardness and low coefficient of friction, which can effectively reduce the erosion and wear of the mating surface when the sand-containing medium flows at high speed, and also reduce the frictional resistance when the spring seat 23 slides back and forth. At the same time, the sliding stroke of the spring seat 23 in the first inner cavity 221 is short and the relative movement range between the mating surfaces is limited. During this reciprocating motion, even if a very small amount of solid particles enter the mating area, it is difficult to form effective embedding or accumulation with the assistance of the smooth surface of the chrome-plated layer. This ensures that the spring seat 23 always slides smoothly in the long-term sand-containing environment and will not affect the normal opening and closing of the device due to particle jamming.

[0027] The working process of this utility model is as follows: During forward flow, the well workover fluid or mud enters the through groove 211 of the ball seat 21 from the upper end of the shell 1, and the fluid pressure acts downward on the top spherical surface of the steel ball 24; when the fluid pressure overcomes the initial preload of the preload spring 25, the steel ball 24 and the spring seat 23 move downward as a whole, and the preload spring 25 is further compressed and contracted in the second inner cavity 231; the steel ball 24 separates from the conical sealing surface 213 of the ball seat 21, and an annular flow gap is formed between the two. The fluid enters the inner cavity of the shell 1 through this gap, and then flows to the lower outlet of the shell 1 through the flow channel 12 between the shell 1 and the fixed cylinder 22, realizing forward conduction.

[0028] When the pump stops or reverse pressure fluctuations occur, the fluid attempts to flow backward from the lower end of the housing 1 through the flow channel 12. At this time, the steel ball 24 quickly returns to its original position under the elastic force of the preload spring 25 and presses against the conical sealing surface 213 of the ball seat 21, cutting off the flow path between the through groove 211 and the flow channel 12. The sealing ring 212 ensures that there is no leakage on the outer wall of the ball seat 21, and the line contact seal between the conical sealing surface 213 and the steel ball 24 forms a reliable one-way seal to prevent the medium from flowing back upstream.

[0029] When it is necessary to adjust the opening pressure or compensate for the fatigue of the preload spring 25, the operator can rotate the threaded column 31, and the lifting plate 32 moves axially under the restriction of the anti-rotation protrusion 321 and the guide groove 222. When the lifting plate 32 moves upward, it compresses the preload spring 25 to increase the preload force, and when it moves downward, it releases the preload spring 25 to decrease the preload force, thereby changing the opening pressure of the steel ball 24. This adjustment process does not require disassembly of the device and can be conveniently completed on-site, improving the device's adaptability to operating conditions and maintenance efficiency.

[0030] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change. Secondly: The accompanying drawings of the embodiments disclosed in this utility model only involve the structures involved in the embodiments disclosed in this utility model. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this utility model can be combined with each other. In conclusion, the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A backflow-preventing, sealing, one-way shut-off device, comprising a housing (1), wherein a flow channel (11) is axially permeated within the housing (1), characterized in that, A one-way shut-off mechanism (2) is provided inside the flow channel (11); The one-way shut-off mechanism (2) includes a ball seat (21) installed on the inner wall of the flow channel (11). A through groove (211) is provided through the ball seat (21) along the axial direction. A fixed cylinder (22) is fixedly installed on the inner wall of the bottom of the flow channel (11). A first inner cavity (221) with the opening facing upward is provided in the fixed cylinder (22). A spring seat (23) is slidably installed on the top of the first inner cavity (221) along the axial direction. A steel ball (24) is installed on the top of the spring seat (23). The top of the steel ball (24) is in contact with the bottom of the through groove (211). The bottom of the spring seat (23) is provided with a second inner cavity (231) with the opening facing downward. A pre-tension spring (25) is provided inside the second inner cavity (231). The top of the pre-tension spring (25) abuts against the top of the second inner cavity (231). The fixed cylinder (22) is provided with a preload adjustment mechanism (3) that abuts against the bottom end of the preload spring (25) to adjust the initial preload of the preload spring (25); The preload adjustment mechanism (3) includes a threaded column (31) rotatably mounted at the bottom of the fixed cylinder (22). The outer wall of the top of the threaded column (31) is provided with an external thread (311). The threaded column (31) is threaded with a lifting plate (32) through the external thread (311). The top of the lifting plate (32) abuts against the bottom of the preload spring (25).

2. The anti-backflow sealing one-way shut-off device according to claim 1, characterized in that, A plurality of flow channels (12) for fluid to pass through are provided axially between the housing (1) and the fixed cylinder (22).

3. The anti-backflow sealing one-way shut-off device according to claim 1, characterized in that, A sealing ring (212) is provided between the outer wall of the ball seat (21) and the inner wall of the flow channel (11), and a conical sealing surface (213) that cooperates with the steel ball (24) is provided at the bottom of the through groove (211).

4. The anti-backflow sealing one-way shut-off device according to claim 1, characterized in that, A limiting ring (312) is fixedly installed on the outer wall of the threaded column (31), and the bottom of the limiting ring (312) is rotatably connected to the bottom of the first inner cavity (221).

5. The anti-backflow sealing one-way shut-off device according to claim 1, characterized in that, The outer edge of the lifting plate (32) is fixedly installed with an anti-rotation protrusion (321), and the inner wall of the first inner cavity (221) is provided with a guide groove (222) that slides with the anti-rotation protrusion (321) along the axial direction.

6. The anti-backflow sealing one-way shut-off device according to claim 1, characterized in that, The inner wall of the flow channel (11) and the outer surface of the spring seat (23) are both provided with a chrome-plated wear-resistant layer.

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