Safety circulation valve with nitrogen chamber

Abstract

The application provides a safety circulation valve with a nitrogen chamber, which comprises a circulation outer cylinder, a shearing mandrel, an upper air chamber, a lower air chamber, a nitrogen chamber, a rupture disc and a ball valve; when the annulus pressure outside the rupture disc is greater than the sum of the critical burst pressure of the rupture disc and the nitrogen pressure of the upper air chamber, the rupture disc bursts, the annulus pressure enters the upper air chamber and pushes the shearing mandrel to move from top to bottom to a circulation working position, so as to drive the ball valve to be closed and open a circulation hole on the circulation outer cylinder. The nitrogen chamber is arranged, so that the ball valve is closed and the circulation hole is opened when the annulus pressure is greater than the sum of the rupture disc pressure and the nitrogen pressure, the strength of the tool air chamber is increased, the larger hydraulic area on the shearing mandrel is maintained while the tool can use the rupture disc with a high burst pressure value, the pressure generated due to the friction resistance in the movement process of the shearing mandrel is reduced, and the reliability of the tool is improved.

Description

Technical Field

[0001] This invention belongs to the field of oil well exploration and extraction, and specifically relates to a safety circulation valve with a nitrogen chamber. Background Technology

[0002] Traditional safety circulation valves have the following problems: those with low air chamber strength cannot meet the operational requirements of high-pressure wells; those with high air chamber strength have small hydraulic area, large error, insufficient power, and the risk of being difficult to drive with logging tools; the high bursting value rupture discs used on safety circulation valves mainly rely on imports, which are expensive, difficult to procure, and have high operating costs. Summary of the Invention

[0003] The purpose of this invention is to provide a safety circulation valve with a nitrogen chamber, which solves the problems of low strength of the air chamber, small hydraulic area, and high price and difficulty in procurement of high-explosive-value fracture discs in existing logging tools.

[0004] To address the above problems, the present invention provides a safety circulation valve with a nitrogen chamber, comprising:

[0005] Circulating outer cylinder;

[0006] The shear mandrel is axially movably disposed inside the circulating outer cylinder;

[0007] The upper air chamber is located near the upper end of the shear mandrel;

[0008] The lower air chamber is located near the lower end of the shear mandrel;

[0009] The nitrogen chamber is connected to the upper air chamber and the lower air chamber by a first pressure transmission channel and a second pressure transmission channel, respectively.

[0010] The rupture disc is installed in a radial hole on the outer circumference of the circulating outer cylinder via a pressure cap, and is located outside the upper air chamber; and

[0011] A ball valve is located on the underside of the shear mandrel;

[0012] Specifically, when the annular pressure outside the rupture disc is greater than the sum of the critical rupture pressure of the rupture disc and the nitrogen pressure in the upper air chamber, the rupture disc ruptures, causing the annular pressure to enter the upper air chamber and push the shear mandrel to move from top to bottom to the circulating working position, thereby driving the ball valve to close and opening the circulation hole on the circulating outer cylinder.

[0013] Preferably, the safety circulation valve further includes:

[0014] A shear ring is disposed on the outer circle of the shear mandrel; and

[0015] The shear pin is set in the radial hole on the outer circle of the shear ring and inserted into the outer annular groove of the shear mandrel;

[0016] Specifically, when the pushing force on the shear mandrel is sufficient to cut the shear pin, the shear mandrel is pushed relative to the circulating outer cylinder.

[0017] Preferably, the safety circulation valve further includes:

[0018] A one-way valve is installed in a radial hole on the outer circumference of the circulating outer cylinder. The one-way valve includes a valve stem and a spring.

[0019] Specifically, when the pressure in the upper air chamber increases, the valve stem can close the second pressure transmission channel on the check valve under the elastic force of the spring, so as to prevent the annular pressure from being transmitted from the upper air chamber to the lower air chamber.

[0020] Preferably, the safety circulation valve further includes:

[0021] The locking ring is set on the outer circle of the shearing mandrel;

[0022] The shearing mandrel and the locking ring are designed with one-way sawtooths on their opposite surfaces. When the shearing mandrel moves to the cyclic working position, the locking ring and the one-way sawtooths on the shearing mandrel mesh with each other to lock the axial position of the shearing mandrel and prevent the shearing mandrel from moving in the opposite direction under the nitrogen pressure in the lower air chamber.

[0023] Preferably, the safety circulation valve further includes:

[0024] The connecting claw is located in the outer annular groove at the lower end of the shearing mandrel;

[0025] The connecting short section is threaded onto the lower end of the connecting claw; and

[0026] An operating pin, located at the lower end of the connecting section, is used to push the ball valve to rotate in a preset direction;

[0027] During the process of the shearing mandrel moving from top to bottom to the cyclic working position, the shearing mandrel sequentially pushes the connecting claw, connecting section and operating pin from top to bottom, thereby closing the ball valve.

[0028] Preferably, the safety circulation valve further includes:

[0029] The outer cylinder of the ball valve is threadedly connected to the lower end of the outer cylinder of the spindle;

[0030] The lower connector is threaded to the lower end of the outer cylinder of the ball valve;

[0031] The ball cage is installed in the inner hole of the connecting section; and

[0032] The ball seat sub-section is located inside the outer cylinder of the ball valve and is threaded to the upper inner hole of the lower connector;

[0033] The ball cage is threadedly connected to the ball seat short section, and the ball valve is positioned between the ball cage and the ball seat short section.

[0034] Preferably, the safety circulation valve further includes:

[0035] A seat spring, located inside the ball cage near the ball valve, provides elastic support between the ball cage and the ball valve; and

[0036] The support ring is located in an annular groove on the side of the ball cage near the connecting short section, and is used to isolate large particles of impurities in the mud.

[0037] Preferably, the safety circulation valve further includes:

[0038] The nitrogen chamber outer cylinder is threadedly connected to the upper side of the circulation outer cylinder;

[0039] The upper connector is threaded to the upper side of the outer cylinder of the nitrogen chamber;

[0040] A nitrogen-filled mandrel is installed inside the upper connector bore; and

[0041] Mandrel outer cylinder; threaded connection to the lower side of the circulating outer cylinder;

[0042] The upper connector, nitrogen chamber outer cylinder, nitrogen chamber mandrel, and circulation outer cylinder form a nitrogen chamber; the circulation outer cylinder, shear mandrel, and mandrel outer cylinder form an upper air chamber; and the shear mandrel and mandrel outer cylinder form a lower air chamber.

[0043] Preferably, the safety circulation valve further includes:

[0044] The shock-absorbing pad is placed between the shear mandrel and the outer cylinder of the mandrel, and is located on the upper side of the lower air chamber. It is used to form axial buffer and shock absorption between the shear mandrel and the outer cylinder during the process of the shear mandrel moving from top to bottom to the cyclic working position.

[0045] Preferably, the safety circulation valve further includes:

[0046] A nitrogen-filling protection plug is installed in a radial hole on the outer circumference of the circulating outer cylinder to fill the nitrogen chamber with nitrogen.

[0047] A nitrogen-filling needle valve, installed in a radial hole on the outer circumference of the circulating outer cylinder and positioned relative to the direction in which the nitrogen-filling protective plug extends into the circulating outer cylinder, is used to control the nitrogen-filling rate; and

[0048] The safety limit screw is installed in the radial hole on the outer circumference of the outer cylinder and is set perpendicular to the direction in which the nitrogen charging needle valve extends into the outer cylinder, so that the part of the safety limit screw protruding from the outer cylinder is blocked from the outside of the nitrogen charging needle valve.

[0049] Based on the above embodiments, the present invention has at least one of the following beneficial effects:

[0050] (1) Due to the presence of nitrogen pressure, the ball valve will be closed and the circulation hole will be opened only after the annular pressure is greater than the sum of the rupture disc pressure and the nitrogen pressure, thus increasing the strength of the tool air chamber;

[0051] (2) Under the same operating environment, the present invention can use a rupture disc with a low critical burst pressure value, which is low in cost and easy to procure.

[0052] (3) While ensuring that the tool can use a high burst pressure value rupture disc, it maintains a large hydraulic area on the shearing mandrel, reduces the pressure generated by frictional resistance during the movement of the shearing mandrel, and improves the reliability of the tool.

[0053] (4) By incorporating unidirectional saw teeth on the surface of the locking ring and the shearing mandrel, a shearing mandrel locking mechanism is added, which makes the shearing mandrel move only in one direction. This can prevent the shearing mandrel from springing back after tool operation, causing the cutting method to open and the circulation hole to close.

[0054] (5) A one-way pressure transmission structure is adopted between the nitrogen chamber and the upper air chamber. The nitrogen pressure can only be transmitted from the nitrogen chamber to the upper air chamber and not from the upper air chamber to the nitrogen chamber, thus avoiding communication between the pressure of the upper air chamber and the lower air chamber and the nitrogen chamber during tool operation.

[0055] (6) The nitrogen chamber and the lower air chamber are connected by bidirectional pressure transmission, and the nitrogen pressure can be transferred between them. During tool operation, the pressure in the lower air chamber can be transferred to the nitrogen chamber. The nitrogen pressure in the lower air chamber slows down the movement speed of the shearing mandrel, reducing tool wear and damage.

[0056] (7) Before the tool is operated, the pressure in the upper and lower air chambers is balanced to avoid the possibility of the tool moving prematurely. Attached Figure Description

[0057] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application, but do not constitute a limitation on the technical solutions of this application.

[0058] Figure 1 This is a schematic diagram of the upper part of the safety circulation valve with a nitrogen chamber of the present invention.

[0059] Figure 2 This is a schematic diagram of the lower half of the safety circulation valve with a nitrogen chamber of the present invention;

[0060] Figure 3 This is a schematic diagram of the upper half (AA section) of the safety circulation valve with a nitrogen chamber of the present invention.

[0061] Figure 4 This is a schematic diagram of the upper half (BB section) of the safety circulation valve with a nitrogen chamber of the present invention.

[0062] In the figure, the components are: upper connector (1), nitrogen chamber outer cylinder (2), nitrogen chamber mandrel (3), circulation outer cylinder (4), shear mandrel (5), mandrel outer cylinder (6), ball valve outer cylinder (7), connecting claw (8), connecting short section (9), operating pin (10), ball cage (11), ball valve (12), ball seat short section (13), lower connector (14), safety limit screw (15), nitrogen filling needle valve (16), one-way valve (17), valve stem (18), spring (19), nitrogen filling protection plug (20), pressure cap (21), rupture disc (22), locking ring (23), shear ring (25), shear pin (24), seat spring (26), shock absorber (27), support ring (28), sealing ring (29-41, different specifications), and nitrogen (42).

[0063] Nitrogen chamber (a), upper air chamber (b), lower air chamber (c), first pressure transmission channel (d), second pressure transmission channel (e). Detailed Implementation

[0064] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are not intended to limit the invention or its application or use in any way. The invention can be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the invention clear and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0065] In general, this invention designs a safety circulation valve with a nitrogen chamber. Before the tool is lowered into the well, the nitrogen chamber is filled with nitrogen at a certain pressure. The nitrogen pressure is transmitted to the upper air chamber and the lower air chamber through the pressure transmission pipeline. The nitrogen pressure in the air chamber creates a reverse pressure difference on the air chamber, thereby improving the strength of the air chamber.

[0066] The pre-charged nitrogen pressure in the air chamber increases the strength of the tool's air chamber. The tool's structural design allows for a larger hydraulic area, improving the tool's operating force and reducing the risk of tool use. The pre-charged nitrogen pressure in the air chamber acts below the rupture disc, increasing the rupture disc's burst pressure. For the same applicable environment, this tool allows for the selection of a rupture disc with a lower burst pressure, resulting in a lower rupture disc cost and easier procurement.

[0067] The technical solution adopted in this invention is,

[0068] See Figures 1-4This is a schematic diagram of the structure of a safety circulation valve with a nitrogen chamber according to the present invention, including an upper connector 1, a nitrogen chamber outer cylinder 2, a nitrogen chamber mandrel 3, a circulation outer cylinder 4, a shear mandrel 5, a mandrel outer cylinder 6, a ball valve outer cylinder 7, a connecting claw 8, a connecting short section 9, an operating pin 10, a ball cage 11, a ball valve 12, a ball seat short section 13, a lower connector 14, a safety limit screw 15, a nitrogen filling needle valve 16, a one-way valve 17, a valve stem 18, a spring 19, a nitrogen filling protective plug 20, a pressure cap 21, a rupture disc 22, a locking ring 23, a shear pin 24, a shear ring 25, a seat spring 26, a shock-absorbing pad 27, a support ring 28, sealing rings of different specifications 29-41, and nitrogen gas 42.

[0069] The sealing ring 29 is set in the inner annular groove of the upper connector 1, and the sealing ring 30 is set in the outer annular groove of the upper connector 1; the nitrogen chamber mandrel 3 is set in the inner hole of the upper connector 1; the nitrogen chamber outer cylinder 2 is threadedly connected to the upper connector 1.

[0070] Sealing ring 29 is set in the inner annular groove of the circulating outer cylinder 4, and sealing ring 30 is set in the outer annular groove; the circulating outer cylinder 4 is threadedly connected to the nitrogen chamber outer cylinder 2; safety limit screw 15, nitrogen filling needle valve 16, one-way valve 17, valve stem 18, spring 19, nitrogen filling protection plug 20, pressure cap 21, and rupture disc 22 are respectively installed in the radial holes of the outer circle of the circulating outer cylinder 4, sealing ring 38 is set in the outer annular groove of the nitrogen filling needle valve 16; sealing ring 39 is set in the annular groove on the end face of the nitrogen filling protection plug 20; sealing ring 40 is set in the outer annular groove of the one-way valve 17; and sealing ring 41 is set in the annular groove on the end face of the rupture disc 22.

[0071] Sealing rings 31 and 34, shock-absorbing pads 27, and support rings 28 are set in the outer annular groove of shearing mandrel 5; locking ring 23 and shearing ring 25 are set on the outer circle of shearing mandrel 5; sealing ring 33 is set in the outer annular groove of locking ring 23; shear pin 24 is set in the radial hole on the outer circle of shearing ring 25 and inserted into the outer annular groove of shearing mandrel 5; locking ring 23 and shearing ring 25 are set on the outer circle of shearing mandrel 5; shearing mandrel 5 is set in the inner hole of circulating outer cylinder 4;

[0072] The sealing ring 32 is set in the inner annular groove of the outer cylinder 6 of the mandrel; the sealing ring 35 is set in the outer annular groove of the outer cylinder 6 of the mandrel; the outer cylinder 6 of the mandrel is threadedly connected to the circulating outer cylinder 4.

[0073] Connecting claw 8 is located in the outer annular groove of shearing mandrel 5; connecting stub 9 is threaded to connecting claw 8; ball valve 12 is located between ball cage 11 and ball seat stub 13, and ball cage 11 is threaded to ball seat stub 13; ball cage 11 is located in the inner hole of connecting stub 9; support ring 28 is located in the outer annular groove of ball cage 11; sealing ring 29 is located in the annular groove of the inner hole of ball seat stub 13; ball valve outer cylinder 7 is threaded to mandrel outer cylinder 6; ball seat stub 13 is threaded to lower connector 14; sealing ring 36 is located in the annular groove of the inner hole of lower connector 14; sealing rings 32 and 37 are located in the outer annular groove of lower connector 14. Nitrogen gas 42 is injected from nitrogen-filled protective plug 20 and trapped in the gap between upper connector 1 and mandrel outer cylinder 6.

[0074] Based on the above structure of the present invention, the space enclosed by the upper connector 1, the nitrogen chamber outer cylinder 2, the nitrogen chamber mandrel 3, and the circulation outer cylinder 4 is called the nitrogen chamber. Before the present invention is lowered into the well, the nitrogen chamber is filled with nitrogen 42. The pressure of the nitrogen 42 in the nitrogen chamber is transmitted in two ways through the pressure transmission channel on the circulation outer cylinder 4: one way is transmitted to the space enclosed by the circulation outer cylinder 4, the shear mandrel 5, and the mandrel outer cylinder 6, i.e., the upper air chamber, which communicates with the lower part of the fracture disk 22, making the pressure of the fracture disk 22 higher; the other way is transmitted to the space enclosed by the shear mandrel 5 and the mandrel outer cylinder 6, i.e., the lower air chamber.

[0075] Before tool operation, the nitrogen pressure in the upper and lower air chambers is equal, and the pressure on both sides of the shear mandrel 5 is balanced, preventing premature shearing of the shear pin. Due to the nitrogen pressure in the lower air chamber, the external pressure resistance of the mandrel outer cylinder 6 is increased, and the internal pressure resistance of the shear mandrel 5 is increased.

[0076] When this invention is used in a well, when the annular pressure is greater than or equal to the burst value of the rupture disc 22 plus the pressure of nitrogen 42, the rupture disc 22 bursts, and the annular pressure enters the upper air chamber to push the shear mandrel 5, shear the shear pin 24, push the connecting claw 8, the connecting short section 9 and the operating pin 10, so that the ball valve 12 is closed, and at the same time the circulation hole on the outer circulation cylinder 4 is opened.

[0077] When the annular pressure enters the upper air chamber, the pressure in the upper air chamber increases. Under the force of the spring 19, the valve stem 18 closes the pressure transmission channel on the one-way valve 17, preventing the annular pressure from being transmitted from the upper air chamber to the lower air chamber. When the annular pressure drives the shear mandrel 5 to move, the nitrogen pressure in the lower air chamber is compressed and transmitted to the nitrogen chamber through the pressure transmission channel, causing the shear mandrel 5 to move into position.

[0078] The shearing mandrel 5 and the locking ring 23 are designed with one-way sawtooths. After the shearing mandrel 5 moves to its position, the locking ring 23 engages with the one-way sawtooths on the shearing mandrel 5 to lock it and prevent the shearing mandrel 5 from moving in the opposite direction under the nitrogen pressure in the lower air chamber.

[0079] Based on the above embodiments, the present invention has at least one of the following beneficial effects:

[0080] (1) Due to the presence of nitrogen pressure, the ball valve will be closed and the circulation hole will be opened only after the annular pressure is greater than the sum of the rupture disc pressure and the nitrogen pressure, thus increasing the strength of the tool air chamber; (2) Under the same operating environment, the present invention can use a rupture disc with a low critical burst pressure value, which is low in cost and easy to procure; (3) The tool hydraulic area is increased, the driving force is increased, and the reliability is improved; (4) By involving unidirectional sawtooth on the surface opposite to the locking ring and the shear mandrel, a shear mandrel locking mechanism is added, so that the shear mandrel can only move in one direction, which can prevent the shear mandrel from springing back after the tool is operated, causing the cutting method to open and the circulation hole to close; (5) A unidirectional pressure transmission structure is adopted between the nitrogen chamber and the upper air chamber, and the nitrogen pressure can only be transmitted from the nitrogen chamber to the upper air chamber, and cannot be transmitted from the upper air chamber to the nitrogen chamber, thus avoiding communication between the upper air chamber pressure and the lower air chamber and the nitrogen chamber during tool operation; (6) A bidirectional pressure transmission is adopted between the nitrogen chamber and the lower air chamber, and the nitrogen pressure can be transmitted to each other. During tool operation, the pressure in the lower air chamber can be transmitted to the nitrogen chamber. The nitrogen pressure in the lower air chamber slows down the movement speed of the shear mandrel, reducing tool wear and damage. (7) A nitrogen chamber is added to pre-charge the upper and lower air chambers with nitrogen. The nitrogen is transmitted to the upper and lower air chambers in two separate paths, so that the pressure in the upper and lower air chambers is balanced before tool operation, avoiding the possibility of the tool moving prematurely.

[0081] In this summary, specific embodiments of the present invention have been described in detail through examples. However, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. It should be understood that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A safety circulation valve with a nitrogen chamber, characterized in that, include: Circulating outer cylinder (4); The shear mandrel (5) is axially movably disposed inside the circulating outer cylinder (4); An upper air chamber is provided near the upper end of the shear mandrel (5); The lower air chamber is located near the lower end of the shear mandrel (5); The nitrogen chamber is connected to the upper air chamber and the lower air chamber by a first pressure transmission channel and a second pressure transmission channel, respectively. A rupture disc (22) is disposed in a radial hole on the outer circumference of the circulating outer cylinder (4) via a pressure cap (21) and is located outside the upper air chamber; and A ball valve (12) is located on the lower side of the shear mandrel (5); When the annular pressure outside the rupture disc (22) is greater than the sum of the critical burst pressure of the rupture disc (22) and the nitrogen (42) pressure in the upper air chamber, the rupture disc (22) bursts, causing the annular pressure to enter the upper air chamber and push the shear mandrel (5) to move from top to bottom to the circulating working position, thereby driving the ball valve (12) to close and opening the circulation hole on the circulating outer cylinder (4); Also includes: A one-way valve (17) is installed in a radial hole on the outer circle of the outer cylinder (4). The one-way valve (17) includes a valve stem (18) and a spring (19). When the pressure in the upper air chamber increases, the valve stem (18) can close the second pressure transmission channel on the one-way valve (17) under the elastic force of the spring (19) to prevent the annular pressure from being transmitted from the upper air chamber to the lower air chamber. Also includes: A locking ring (23) is disposed on the outer circle of the shear mandrel (5); The shearing mandrel (5) and the locking ring (23) are designed with one-way saw teeth on their opposite surfaces. When the shearing mandrel (5) moves to the cyclic working position, the locking ring (23) and the one-way saw teeth on the shearing mandrel (5) mesh with each other to lock the axial position of the shearing mandrel (5) and prevent the shearing mandrel (5) from moving in the opposite direction under the nitrogen pressure in the lower air chamber. Also includes: The nitrogen chamber outer cylinder (2) is threadedly connected to the upper side of the circulating outer cylinder (4); The upper connector (1) is threadedly connected to the upper side of the outer cylinder (2) of the nitrogen chamber; Nitrogen chamber mandrel (3) is installed in the inner hole of the upper connector (1); and Mandrel outer cylinder (6); threaded connection to the lower side of the circulating outer cylinder (4); The upper connector (1), the nitrogen chamber outer cylinder (2), the nitrogen chamber mandrel (3), and the circulation outer cylinder (4) form the nitrogen chamber; the circulation outer cylinder (4), the shear mandrel (5), and the mandrel outer cylinder (6) form the upper air chamber; and the shear mandrel (5) and the mandrel outer cylinder (6) form the lower air chamber.

2. The safety circulation valve according to claim 1, characterized in that, Also includes: The connecting claw (8) is located in the outer annular groove at the lower end of the shearing mandrel (5); A connecting short section (9) is threaded to the lower end of the connecting claw (8); and An operating pin (10) is located at the lower end of the connecting section (9) to push the ball valve (12) to rotate in a preset direction; During the process of the shearing mandrel (5) moving from top to bottom to the cyclic working position, the shearing mandrel (5) sequentially pushes the connecting claw (8), the connecting short section (9) and the operating pin (10) from top to bottom, thereby closing the ball valve (12).

3. The safety circulation valve according to claim 2, characterized in that, Also includes: The ball valve outer cylinder (7) is threadedly connected to the lower end of the spindle outer cylinder (6); The lower connector (14) is threaded to the lower end of the outer cylinder (7) of the ball valve; The ball cage (11) is disposed in the inner hole of the connecting section (9); and The ball seat short section (13) is located inside the outer cylinder (7) of the ball valve and is threaded to the upper inner hole of the lower connector (14); The ball cage (11) is threadedly connected to the ball seat section (13), and the ball valve (12) is located between the ball cage (11) and the ball seat section (13).

4. The safety circulation valve according to claim 3, characterized in that, Also includes: A seat spring (26) is disposed inside the ball cage (11) on the side near the ball valve (12) to provide elastic support between the ball cage (11) and the ball valve (12); and A support ring (28) is provided in an annular groove on the side of the ball cage (11) near the connecting section (9) to isolate large particles of impurities in the mud.

5. The safety circulation valve according to claim 1, characterized in that, Also includes: A shock-absorbing pad (27) is disposed between the shear mandrel (5) and the outer cylinder of the mandrel (6) and located on the upper side of the lower air chamber. It is used to form an axial buffer and shock absorption between the shear mandrel (5) and the outer cylinder of the mandrel (6) during the process of the shear mandrel (5) moving from top to bottom to the cyclic working position.

6. The safety circulation valve according to claim 5, characterized in that, Also includes: A nitrogen-filling protection plug (20) is installed in a radial hole on the outer circle of the circulating outer cylinder (4) to fill the nitrogen chamber with nitrogen (42). A nitrogen-filling needle valve (16) is installed in a radial hole on the outer circumference of the circulating outer cylinder (4) and is positioned relative to the direction in which the nitrogen-filling protective plug (20) extends into the circulating outer cylinder (4) to control the inrush speed of the nitrogen gas (42); and A safety limit screw (15) is installed in a radial hole on the outer circle of the circulation outer cylinder (4) and is set perpendicular to the direction in which the nitrogen filling needle valve (16) extends into the circulation outer cylinder (4) so ​​that the portion of the safety limit screw (15) protruding from the circulation outer cylinder (4) is blocked from the outside of the nitrogen filling needle valve (16).

Images