Releasing hydraulic compensation device

Abstract

The utility model belongs to the field of oil extraction operation downhole tools, and particularly relates to a releasing hydraulic compensation device. The releasing hydraulic compensation device comprises an upper connector, a lower connector and an outer cylinder, the upper connector comprises an upper large-diameter section and a lower small-diameter section, the lower connector is in threaded connection with the small-diameter section of the upper connector, the upper end of the outer cylinder is in threaded connection with the large-diameter section of the upper connector, the lower end of the outer cylinder and the lower connector are assembled in a sealing fit mode, and the upper connector, the lower connector and the outer cylinder define an annular cavity. A liquid inlet hole which is communicated with the annular cavity and an inner cavity of the upper connector and provides hydraulic pressure for the lower end face of the piston is formed in the lower portion of the upper connector, and a liquid outlet hole which is communicated with the annular cavity and the oil sleeve annulus is formed in the upper portion of the outer cylinder. When a tubular column with the device is used for setting, liquid in the inner cavity of the upper connector is introduced into the annular cavity through the liquid inlet hole to push the piston to move, liquid in the annular cavity is discharged to an oil sleeve annulus through the liquid outlet hole, and pressure accumulation in the annular cavity is avoided, so that the resistance of axial movement of the piston is effectively reduced, and the piston can move more smoothly.

Description

Technical Field

[0001] This utility model belongs to the field of downhole tools for oil production operations, and specifically relates to a hydraulic compensation device for hand release. Background Technology

[0002] Drop operations are common in oil drilling and well completion. After downhole tools such as packers and tubing are deployed and installed in the predetermined position, specific operations such as ball dropping, pressurizing, and rotating are used to set and fix the packer to the wellbore. After setting, specific operations such as pressurizing and rotating are used to separate the packer from the deployed tubing, thereby achieving drop operations and enabling specific downhole operations or engineering objectives.

[0003] The common main combination of current intelligent sampling tubing is "hydraulic release mechanism + packer + intelligent switch + packer + ... + plug". The structure of the hydraulic release mechanism, as disclosed in Chinese Utility Model Patent No. CN210217671U, authorized on March 31, 2020, includes an upper connector, a separation claw threadedly connected to the upper connector inside the retrieval neck, a mandrel fixedly connected to the separation claw by a pin, a piston section threadedly connected to the mandrel, and a lower connector threadedly connected to the retrieval neck. During the release operation, after the steel ball completes its seat sealing in the piston section, hydraulic pressure pushes the piston section and mandrel downwards, shearing the pin and unlocking the separation claw. This allows the upper connector, separation claw, piston section, mandrel, and other components to separate from the lower connector and its lower connecting parts. When the hydraulic release mechanism is applied in the aforementioned tubular structure, the intelligent switch has a one-way valve channel, allowing liquid to enter the tubular structure only; the plug is a solid structure, preventing liquid from entering or leaving the tubular structure; during use, due to the incompressibility of the liquid inside the tubular structure, the piston section and spindle of the hydraulic release mechanism cannot move to the designed position, thus preventing the release mechanism from being unlocked and disengaged.

[0004] Chinese utility model patent with authorization announcement number CN216617475U and authorization announcement date of May 27, 2022 discloses an oil pipe pressure compensation device, including an upper connector and a lower connector threadedly connected to the upper connector. The upper connector includes a large-diameter section and a small-diameter section. The lower connector is screwed to the lower end of the small-diameter section. A piston is fitted on the upper outer periphery of the small-diameter section. The outer wall of the piston extends to the upper and lower sides to form a piston sleeve. The upper part of the piston sleeve extends to the outer wall of the large-diameter section and seals against it. The lower part of the piston sleeve extends to the outer wall of the lower connector. A closed annular cavity is formed between the top surface of the piston and the bottom step of the large-diameter section. A compensation radial hole communicating with the annular cavity is provided at the root of the small-diameter section. A spring is provided between the bottom of the piston and the top of the lower connector. This tubing pressure compensation device is installed at the lower end of the tubing string during use. A one-way valve is installed below it, and above it are a water injector, packer, and acid injection sliding sleeve valve. When the tubing string reaches the designed downhole position, surface pressurization sets the packer. When the sliding sleeve of the acid injection sliding sleeve valve becomes pressurized, the piston of this pressure compensation device descends and compresses the spring, allowing some space for the liquid column below the sliding sleeve, preventing pressure buildup below the sleeve. When the wellhead pressure reaches the predetermined level, the acid injection sliding sleeve valve can be opened smoothly. However, during use, when the piston descends under pressure, the air in the spring mounting cavity formed by the small-diameter section of the upper connector, the piston bottom surface, and the upper end face of the lower connector is compressed, creating a reaction force on the piston's axial movement and increasing the piston's axial movement resistance. Simultaneously, the spring compression affects the piston's axial displacement. Furthermore, if the mating area between the lower connector and the piston sleeve accumulates downhole sediment, scale, or corrosion products, it may increase the piston's axial movement resistance or even cause jamming, preventing it from responding to pressure changes. Utility Model Content

[0005] The purpose of this invention is to provide a hydraulic compensation device for releasing the piston, so as to solve the problem that the piston axial movement resistance is large due to the structural defects of the spring mounting cavity in the existing oil pipe pressure compensation device.

[0006] To achieve the above objectives, the hydraulic compensation device for hand loss in this utility model adopts the following technical solution: A hydraulic compensation device for hand loss includes an upper connector and a lower connector. The upper connector includes an upper large-diameter section and a lower small-diameter section. The lower connector is threadedly connected to the small-diameter section of the upper connector. The hydraulic compensation device for hand loss also includes an outer cylinder. The upper end of the outer cylinder is threadedly connected to the large-diameter section of the upper connector. The lower end of the outer cylinder is sealed and fitted with the lower connector. The upper connector, the lower connector, and the outer cylinder form an annular cavity. A piston is disposed in the annular cavity. The lower part of the upper connector is provided with an inlet hole that connects the annular cavity and the inner cavity of the upper connector and provides hydraulic pressure to the lower end face of the piston. The upper part of the outer cylinder is provided with an outlet hole that connects the annular cavity and the annular space of the oil sleeve.

[0007] Furthermore, it also includes a spring for resetting the piston, the spring being disposed between the upper end face of the piston and the stepped surface at the connection between the large-diameter section and the small-diameter section of the upper connector.

[0008] Furthermore, the outer wall of the upper connector is provided with a limiting structure for restricting the upward stroke position of the piston.

[0009] Furthermore, the small diameter section of the upper connector includes a first diameter section connected to the large diameter section of the upper connector and a second diameter section connected to the first diameter section. The outer diameter of the first diameter section is larger than the outer diameter of the second diameter section, and the limiting structure is a tapered surface at the connection between the first diameter section and the second diameter section.

[0010] Furthermore, the bottom end face of the piston near the inlet hole, together with the upper connector, the lower connector, and the outer cylinder, forms an inlet annular cavity that communicates with the inlet hole.

[0011] Furthermore, a boss is provided at the middle of the bottom end of the piston or at the middle of the top surface of the lower connector.

[0012] Furthermore, sealing structures are provided between the piston and the outer cylinder and between the piston and the upper connector, respectively.

[0013] Furthermore, a sealing structure is provided between the outer cylinder and the lower connector.

[0014] Furthermore, the upper connector is fixed to the outer cylinder by connecting pins.

[0015] The beneficial effects of this utility model are as follows: the hydraulic compensation device for hand loss provided by this utility model is based on the improvement of the existing technology. This hydraulic release device works in conjunction with existing hydraulic release tools. The outer sleeve is fitted onto the outside of the upper and lower connectors, forming an annular cavity together with the small-diameter section of the upper connector and the upper end face of the lower connector. This utilizes the spatial relationship between the components to create a relatively independent and enclosed space for piston movement. Simultaneously, the outer sleeve protects the piston and other components located inside the annular cavity, preventing damage from external impurities and extending the service life of the hydraulic release device. When the tubing of this hydraulic release device is set, liquid from the upper connector's inner cavity is introduced into the annular cavity through the inlet port. The liquid pressure drives the piston, and the liquid in the annular cavity is discharged to the annulus through the outlet port, preventing pressure buildup and "pressure buildup" within the annular cavity. This effectively reduces the resistance to axial piston movement, allowing for smoother piston movement. Furthermore, during the piston's upward movement, the upper connector's inner cavity "makes room" due to piston movement, providing necessary displacement margin for unlocking the hydraulic release tool, ensuring a smooth unlocking action and successful release operation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the hydraulic compensation device for hand loss according to this utility model.

[0017] In the diagram: 1. Upper connector; 2. Connecting pin; 3. Outer cylinder; 4. Spring; 5. Piston; 6. Lower connector; 7. Annular cavity; 11. Large diameter section; 12. Small diameter section; 13. Liquid inlet hole; 14. Inner cavity of upper connector; 111. Stepped surface; 121. First diameter section; 122. Second diameter section; 123. Conical surface; 31. Liquid outlet hole; 51. First seal; 52. Second seal; 53. Boss; 61. Third seal; 71. Liquid inlet annular cavity. Detailed Implementation

[0018] The features and performance of this utility model will be further described in detail below with reference to the embodiments.

[0019] The hydraulic compensation device for releasing the piston provided by this utility model is used in conjunction with existing hydraulic release tools. It utilizes the spatial relationship between the upper connector, lower connector, and outer cylinder to form a relatively independent annular cavity. The annular cavity is equipped with an inlet port connecting to the inner cavity of the upper connector and an outlet port connecting to the annulus of the oil sleeve. The piston is positioned within the annular cavity. During setting, the liquid in the inner cavity of the upper connector enters the annular cavity through the inlet port, pushing the piston to move. The liquid in the annular cavity is discharged to the annulus of the oil sleeve through the outlet port, preventing pressure buildup in the annular cavity and thus effectively reducing the resistance to axial movement of the piston.

[0020] An embodiment of the hydraulic compensation device for hand loss in this utility model:

[0021] like Figure 1 As shown, the hydraulic compensation device for hand loss provided by this utility model includes a tubular upper connector 1 and a lower connector 6. The upper connector 1 includes an upper large-diameter section 11 and a lower small-diameter section 12. The lower connector 6 is threadedly connected to the small-diameter section 12 of the upper connector 1. The hydraulic compensation device for hand loss also includes an outer cylinder 3. The upper end of the outer cylinder 3 is threadedly connected to the large-diameter section 11 of the upper connector 1. The lower end of the outer cylinder 3 is sealed with the lower connector 6. The upper connector 1, the lower connector 6 and the outer cylinder 3 form an annular cavity 7. A piston 5 is provided in the annular cavity 7. The annular cavity 7 is provided with inlet holes 13 on both sides of the piston 5 in the direction of movement for connecting to the inner cavity 14 of the upper connector and providing hydraulic pressure to the lower end face of the piston 5, and outlet holes 31 for connecting to the annulus of the oil jacket.

[0022] Specifically, the upper connector 1 is used to connect with the hydraulic release mechanism. The upper connector 1 includes an upper large-diameter section 11 and a lower small-diameter section 12, with the outer diameter decreasing sequentially. The large-diameter section 11 of the upper connector 1 includes an internal threaded portion for connection with the hydraulic release mechanism and an external threaded portion for installation of the outer cylinder 3. The lower end of the small-diameter section 12 of the upper connector 1 is provided with an external thread for threaded connection with the lower connector 6. A stepped surface 111 is formed at the connection between the large-diameter section 11 and the small-diameter section 12 of the upper connector 1. The outer cylinder 3 is connected to the upper connector 1 through the external thread of the large-diameter section 11. The inner circumferential surface of the outer cylinder 3 is sealed and fitted with the outer circumferential surface of the lower connector 6; the outer wall of the small diameter section 12 of the upper connector 1, the upper end face of the lower connector 6, and the inner wall of the outer cylinder 3 together form an annular cavity 7; the piston 5 is disposed in the annular cavity 7 and sleeved on the outside of the small diameter section 12 of the upper connector 1; the lower part of the upper connector 1 (the end near the lower connector 6) is provided with an inlet hole 13 for connecting the inner cavity 14 of the upper connector and the annular cavity 7, and the upper part of the outer cylinder 3 (the end away from the lower connector 6) is provided with an outlet hole 31 for connecting the annular cavity 7 and the annular space of the oil sleeve.

[0023] In the above embodiments, this hydraulic release compensation device is used in conjunction with existing hydraulic release tools. When the tubing of this hydraulic release compensation device is set, the liquid in the inner cavity 14 of the upper connector is introduced into the annular cavity 7 through the inlet hole 13. The pressure of the liquid pushes the piston 5 to move, and the liquid in the annular cavity 7 is discharged to the oil sleeve annulus through the outlet hole 31 to avoid pressure accumulation in the annular cavity 7 and avoid the "pressure buildup" phenomenon. This effectively reduces the resistance to the axial movement of the piston 5, allowing the piston 5 to move more smoothly. At the same time, the inner cavity 14 of the upper connector "makes room" due to the movement of the piston 5. The "makes room" provides the necessary displacement margin for the unlocking of the hydraulic release tool, ensuring that the unlocking action can be completed smoothly and the release operation can be carried out smoothly. The upper connector 1 and the lower connector 6 are connected by threads, and the outer cylinder 3 is connected to the upper connector 1 by threads and sealed with the lower connector 6, which can ensure the stable connection between the components and ensure the structural stability under complex downhole conditions.

[0024] In other embodiments, a convex ring is provided on the lower outer wall of the small-diameter section of the upper connector or on the inner wall of the outer cylinder. The liquid inlet is located on the side of the small-diameter section close to the convex ring and away from the lower connector. Correspondingly, the lower part of the outer cylinder is sealed with the upper connector through the convex ring. At this time, the outer wall of the small-diameter section of the upper connector and the inner wall of the outer cylinder together form an annular cavity.

[0025] As a further embodiment, a spring 4 for resetting the piston 5 is provided between the upper end face of the piston 5 and the stepped surface 111 at the connection between the large-diameter section 11 and the small-diameter section 12. Specifically, the spring 4 is disposed in the annular cavity 7 and sleeved on the small-diameter section 12 of the upper connector 1; one end of the spring 4 abuts against the upper end face of the piston 5, and the other end abuts against the stepped surface 111 at the connection between the large-diameter section 11 and the small-diameter section 12. When the spring 4 is in its natural state, it supports the piston 5 and can provide a resetting force to the piston 5 after the hydraulic pressure disappears, allowing it to return to its initial position, ensuring that this hydraulic compensation device can be reused. At the same time, the spring 4 can play a certain buffering role during the movement of the piston 5.

[0026] In this embodiment, the outer wall of the upper connector 1 is provided with a limiting structure for restricting the upward stroke position of the piston 5. Specifically, the small diameter section 12 includes a first diameter section 121 connected to the large diameter section 11, and a second diameter section 122 connected to the first diameter section 121. The second diameter section 122 is provided with an external thread for threaded connection with the lower connector 6. The outer diameter of the first diameter section 121 is larger than that of the second diameter section 122. A conical surface 123 is formed at the connection between the first diameter section 121 and the second diameter section 122. This conical surface 123 constitutes the limiting structure when the piston 5 moves upward. When the piston 5 is pressed upward (the piston 5 moves from the inlet hole 13 to the outlet hole 31), the displacement stops when the inner wall of the piston 5 abuts against the conical surface 123. This limiting structure restricts the maximum upward stroke of piston 5, precisely controlling the range of movement of piston 5 within the annular cavity 7. This ensures consistency in the space required for unlocking the hydraulic release tool (i.e., the displacement of piston 5), improving operational reliability. Simultaneously, it prevents damage to components such as spring 4 due to excessive upward movement of piston 5, avoiding operational risks caused by tool malfunctions and guaranteeing the reliability of the hydraulic release compensation device. The conical surface 123 guides piston 5 to automatically align itself during upward movement, reducing radial offset and dispersing the impact force of piston 5 to prevent localized stress concentration. Utilizing the conical surface 123 naturally formed by the connection of the first diameter segment 121 and the second diameter segment 122 as a limiting structure eliminates the need for additional axial space, making the device structure more compact.

[0027] In this embodiment, the limiting structure and the spring 4 together constitute the double limiting structure of the piston 5. The limiting structure provides the limit to the displacement endpoint of the piston 5, and the spring 4 provides the reset force. The two work together to fix the movement trajectory of the piston 5.

[0028] In other embodiments, the connection between the first diameter segment 121 and the second diameter segment 122 of the upper connector 1 is a stepped surface 111; or, it is an annular boss that is evenly distributed along the circumference of the outer wall of the upper connector 1, forming a surface contact limit with the upper end surface of the piston 5.

[0029] In this embodiment, a boss 53 is provided in the middle of the bottom end of the piston 5. Specifically, the boss 53 is provided in the middle of the end face of the piston 5 close to the liquid inlet hole 13. That is to say, the overall cross-section of the piston 5 is in a "convex" shape structure. At one end close to the liquid inlet hole 13, a liquid inlet ring cavity 71 communicating with the liquid inlet hole 13 is jointly enclosed by the outer wall of the boss 53, the inner wall of the upper joint 1, the upper end face of the lower joint 6 and the inner wall of the outer cylinder 3. The liquid inlet ring cavity 71 receives high-pressure liquid from the inner cavity 14 of the upper joint through the liquid inlet hole 13, and diffuses along the outer wall of the boss 53, and then is guided to the lower end face of the piston 5, providing uniform liquid pressure for the piston 5 to ensure the force balance during the movement of the piston 5.

[0030] In other embodiments, a boss is provided in the middle of the upper end face of the lower joint. Correspondingly, a boss may not be provided in the middle of the bottom end of the piston; or, only a stepped surface or a tapered surface on the inner circumference may be provided at one end of the piston 5 close to the liquid inlet hole 13, so that the liquid inlet ring cavity is jointly enclosed by the inner wall of the upper joint, the upper end face of the lower joint and the stepped surface or tapered surface of the piston; of course, it may also be other structures that are easy to form the liquid inlet ring cavity 71 or liquid inlet gap with the upper joint 1, the lower joint 6 and / or the outer cylinder 3.

[0031] In this embodiment, the end face of the piston 5 in contact with the spring 4 has a chamfer. When the piston 5 cooperates with the tapered surface 123, it is easy to form a surface contact, thereby effectively buffering the impact of the piston 5 and providing stable limit through the surface contact.

[0032] Sealing structures are respectively provided between the piston 5 and the outer cylinder 3 and between the piston 5 and the second diameter section 122 of the upper joint 1. Specifically, two first sealing grooves are arranged at intervals along the axial direction on the outer peripheral surface of the piston 5, and first sealing members 51 are installed in the first sealing grooves. The sealing between the piston 5 and the outer cylinder 3 is achieved through the first sealing members 51; two second sealing grooves are arranged at intervals along the axial direction on the inner peripheral surface of the piston 5, and second sealing members 52 are embedded in the second sealing grooves. The sealing between the piston 5 and the upper joint 1 is achieved through the second sealing members 52. In other embodiments, only one sealing member or more than two sealing members may be provided between the piston 5 and the outer cylinder 3 and between the piston 5 and the second diameter section 122 of the upper joint 1. It should be understood that the number of sealing members is reasonably set according to actual needs, and this is not limited in this embodiment. The sealing structures between the piston 5 and the upper joint 1 and between the piston 5 and the outer cylinder 3 can prevent liquid from leaking from the gap between the two, ensure the stability of the liquid pressure in the liquid inlet ring cavity 71, so as to ensure that the device can accurately operate according to the design requirements and achieve the release operation; at the same time, the sealing structure can prevent external impurities from entering the space between the piston 5 and the outer cylinder 3 and between the piston 5 and the upper joint 1, avoiding wear or blockage caused by impurities.

[0033] In this embodiment, the lower connector 6 has a first outer diameter section and a second outer diameter section connected in sequence with decreasing outer diameters. The first outer diameter section has an internal thread for connecting with the external thread of the second diameter section 122 of the upper connector 1; the second outer diameter section has an external thread for connecting with downhole tools.

[0034] In this embodiment, a sealing structure is provided between the inner circumferential surface of the outer cylinder 3 and the outer circumferential surface of the lower connector 6. Specifically, the inner diameter of the outer cylinder 3 matches the outer diameter of the first outer diameter section of the lower connector 6, and two third sealing elements 61 are axially spaced between them. Two third sealing grooves are axially spaced on the first outer diameter section, and the third sealing elements 61 are respectively embedded in the third sealing grooves. The third sealing elements 61 and the third sealing grooves constitute the sealing structure between the outer cylinder 3 and the lower connector 6. In other embodiments, the third sealing grooves can be provided on the outer cylinder 3, which can also achieve sealing between the contact surfaces of the outer cylinder 3 and the lower connector 6. Of course, only one sealing structure or two or more sealing structures can be provided between the outer cylinder 3 and the lower connector 6. It should be understood that the number of sealing elements is reasonably set according to needs, and this embodiment does not limit this. The outer cylinder 3 and the lower connector 6 are tightly connected through the sealing structure to prevent hydraulic leakage in the annular cavity 7 and ensure stable liquid pressure in the annular cavity 7; at the same time, it prevents impurities in the annular space of the oil sleeve from entering the annular cavity 7.

[0035] In this embodiment, the first sealing element 51, the second sealing element 52, and the third sealing element 61 are all O-rings.

[0036] In a further embodiment, the outer cylinder 3 is fixed to the upper connector 1 by at least one connecting pin 2. It should be understood that the number of connecting pins 2 is reasonably selected according to actual conditions, and this embodiment does not limit this. The connecting pins 2 can restrict the relative rotation between the outer cylinder 3 and the upper connector 1, ensuring the stability of the long-term connection, and can effectively share the force borne by the threaded connection between the outer cylinder 3 and the upper connector 1, increasing the connection strength between the upper connector 1 and the outer cylinder 3; when the device is subjected to shear force or lateral force, the connecting pins 2 can provide additional shear resistance, preventing relative displacement or separation between the upper connector 1 and the outer cylinder 3.

[0037] When using the hydraulic compensation device for releasing the hydraulic handle provided by this utility model, it is connected to the lower part of the hydraulic release handle during well entry. After the tubing is lowered to the designed position, a ball is dropped to pressurize it. After the designed pressure of the hydraulic release handle is reached, the mandrel of the hydraulic release handle descends and squeezes the liquid in the tubing. The liquid enters the inlet annular cavity 71 through the inlet hole 13 of the upper connector 1. Under the continuous downward compression of the mandrel of the hydraulic release handle, the liquid pushes the piston 5 upward. The piston 5 squeezes the liquid in the annular cavity 7 and discharges it from the outlet hole 31, thereby making room for the mandrel of the hydraulic release handle to descend, ensuring that the mandrel of the hydraulic release handle descends to the correct position, and then unlocks and releases the hydraulic release handle.

[0038] It should be noted that the hydraulic release tool provided by this utility model can be the hydraulic release tool in CN210217671U.

[0039] Finally, it should be noted that the above are merely preferred embodiments of this utility model and are not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some technical features, or organically combine different specific implementation methods to create the specific implementation methods shown in the accompanying drawings. Of course, those skilled in the art can also create other specific implementation methods not shown in the accompanying drawings. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A hydraulic compensation device for hand release, comprising an upper connector and a lower connector, the upper connector comprising an upper large-diameter section and a lower small-diameter section, the lower connector being threadedly connected to the small-diameter section of the upper connector, characterized in that: The hydraulic compensation device for releasing the device also includes an outer cylinder. The upper end of the outer cylinder is threaded to the large diameter section of the upper connector. The lower end of the outer cylinder is sealed and fitted with the lower connector. The upper connector, the lower connector, and the outer cylinder form an annular cavity. A piston is provided in the annular cavity. The lower part of the upper connector is provided with an inlet hole that connects the annular cavity and the inner cavity of the upper connector and provides hydraulic pressure to the lower end face of the piston. The upper part of the outer cylinder is provided with an outlet hole that connects the annular cavity and the annular space of the oil sleeve.

2. The hydraulic compensation device for hand release according to claim 1, characterized in that: It also includes a spring for resetting the piston, the spring being disposed between the upper end face of the piston and the stepped surface at the connection between the large-diameter section and the small-diameter section of the upper connector.

3. The hydraulic compensation device for hand release according to claim 1 or 2, characterized in that: The outer wall of the upper connector is provided with a limiting structure for restricting the upward stroke position of the piston.

4. The hydraulic compensation device for hand release according to claim 3, characterized in that: The small diameter section of the upper connector includes a first diameter section connected to the large diameter section of the upper connector and a second diameter section connected to the first diameter section. The outer diameter of the first diameter section is larger than the outer diameter of the second diameter section. The limiting structure is a tapered surface at the connection between the first diameter section and the second diameter section.

5. The hydraulic compensation device for hand release according to claim 1 or 2, characterized in that: The bottom end face of the piston near the inlet hole, together with the upper connector, lower connector and outer cylinder, forms an inlet annular cavity that communicates with the inlet hole.

6. The hydraulic compensation device for hand release according to claim 5, characterized in that: A boss is provided at the middle of the bottom end of the piston or at the middle of the top surface of the lower connector.

7. The hydraulic compensation device for hand release according to claim 1 or 2, characterized in that: A sealing structure is provided between the piston and the outer cylinder and between the piston and the upper connector.

8. The hydraulic compensation device for hand release according to claim 1 or 2, characterized in that: A sealing structure is provided between the outer cylinder and the lower connector.

9. The hydraulic compensation device for hand release according to claim 1 or 2, characterized in that: The upper connector is fixed to the outer cylinder by connecting pins.

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