Control valve for oil fields

Abstract

The control valve used in oilfields features a valve seat guide sleeve at the valve seat location. This sleeve is pushed higher than the valve seat sealing surface by the medium after the valve is opened, preventing the medium from eroding the valve seat sealing surface. When closed, the guide sleeve is moved by the bottom step of the valve disc, exposing the valve seat sealing surface and achieving a zero-leakage seal with the valve disc sealing surface. A valve disc guide sleeve is also installed on the valve disc. Driven by the disc spring force and the downstream medium force, the guide sleeve remains lower than the valve disc sealing surface at the moment of opening, at a certain opening height, and when fully open, ensuring the sealing surface is hidden within the guide sleeve and not eroded by the medium. The valve's regulating and throttling functions are achieved through the relative position between the throttling orifice on the side of the hollow tube at the lower end of the valve disc and the valve seat guide sleeve. When the valve is in the initial regulating position, the regulating position, or the fully open position, the upper end of the valve seat guide sleeve is always higher than the valve seat sealing surface, and the lower end of the valve disc guide sleeve is always lower than the valve disc sealing surface, preventing the medium from eroding and damaging the valve disc sealing surface through cavitation.

Description

Technical Field

[0001] This invention relates to the field of valve technology, and specifically to a control and regulating valve for oil fields. Background Technology

[0002] High-pressure throttling regulating valves are mainly used in oilfield water injection operations. The characteristics of oilfield water injection operations include: high pressure (16MPa, 25MPa, 42MPa), large pressure differential throttling, media containing silt, rust, corrosive ions, long-term small-opening regulation, and continuous 24-hour operation. Ordinary throttling regulating valves can be damaged by the fluid, suffer sealing failure, uncontrolled regulation, and structural damage. The main reasons are: First, cavitation damage. The pressure difference across the water injection valve is generally 10~30MPa. When the medium flows through the narrow throttling gap of the valve core, the flow velocity increases sharply, and the local pressure is lower than the saturated vapor pressure of water, causing water vaporization and forming a large number of bubbles. These bubbles collapse instantly in the downstream high-pressure area, generating a 2000MPa shock wave that creates honeycomb-like pits on the valve core and valve seat sealing surfaces. This manifests as severe valve vibration and a sharp whistling noise; pitting corrosion on the sealing surface quickly leads to internal leakage; long-term cavitation can penetrate the valve core and erode the valve body flow channel. In addition, there are issues such as prolonged small-opening regulation, pressure difference across the valve exceeding 10 MPa, and high dissolved gas content in the water. Secondly, there is erosion and wear from solid particles. Oilfield reinjection water carries silt, pipeline rust, and corrosive scale. High-pressure, high-speed water flow carries hard particles that continuously cut into the metal surface of the throttling zone, causing streamlined deep grooves to carve out of the throttling groove and valve seat sealing surface, resulting in loss of sealing pressure. Cavitation first creates pits, and then particles further intensify the cutting, resulting in double damage that significantly shortens the valve's service life. Therefore, under these conditions, most throttling control valves only last two to three months before exhibiting significant internal leakage, and their regulating function is essentially destroyed. Summary of the Invention

[0003] In response to the harsh conditions described above, ordinary throttling valves have extremely short lifespans, affecting normal production operations and resulting in low production efficiency. This invention provides a control and regulating valve for oil fields. In the initial opening, regulating, and fully open states, the valve seat and valve disc sealing surfaces are hidden and protected from media erosion, keeping them away from the high-speed flow area of ​​the media and located in a region where the media is essentially not flowing.

[0004] The technical solution adopted in this invention is: an oilfield control and regulating valve, including a valve body, a valve stem provided inside the valve body, a valve disc at the end of the valve stem, a lower flow channel for medium entry and an upper flow channel for medium exit within the valve body, the lower and upper flow channels being connected by a valve seat flow channel opening, an upward-facing valve seat sealing surface provided on the valve seat flow channel opening, a valve seat guide sleeve provided below the valve seat flow channel opening, and a limiting sleeve provided at the bottom of the valve seat guide sleeve, the valve seat guide sleeve being floatingly installed between the valve seat flow channel opening and the limiting sleeve, the valve seat guide sleeve including a fully open position where it is pushed higher than the valve seat sealing surface by the upstream medium after the valve is opened, preventing the medium from scouring the valve seat sealing surface, and a closed position where the valve seat guide sleeve is pushed down by the bottom step of the valve disc when closed, so that the valve seat sealing surface is exposed and seals with the valve disc sealing surface.

[0005] The valve seat has an inner hole formed on the flow channel opening, and a step is provided on the inner hole. The valve seat guide sleeve is limited and fitted with the step and sealed by an O-ring. Under the thrust of the medium, the valve seat guide sleeve is tightly pushed onto the step surface, making the valve seat guide sleeve higher than the valve seat sealing surface H. This ensures that the valve seat guide sleeve is higher than the valve seat sealing surface H at the moment of valve opening, during the opening process, and in the fully open state, thus preventing medium erosion or cavitation from occurring on the valve seat sealing surface.

[0006] The valve body has a bottom cover, and the limiting sleeve is installed on the bottom cover.

[0007] The valve disc is provided with a valve disc guide sleeve on its outer side, and the valve disc guide sleeve is installed on the step in the middle of the valve disc.

[0008] The valve disc is also provided with a disc spring seat on the outside. The disc spring seat is threadedly connected to the valve disc and sealed with an O-ring. The disc spring seat, the valve disc and the O-ring between them form a sealed and fixed rigid body that moves up and down together with the valve disc. A disc spring is also provided between the disc spring assembly seat and the valve disc guide sleeve. The valve disc and the valve disc guide sleeve are sealed by an O-ring. The disc spring, the valve disc guide sleeve and the O-ring are combined to form a movable body that moves axially within the rigid annular groove between the disc spring assembly seat and the middle step of the valve disc.

[0009] The lower end of the valve disc is also configured as a hollow tube, and the side of the hollow tube is provided with a throttling hole. The lower cylindrical side of the valve seat guide sleeve is provided with a medium flow hole, and the upper part of the limiting sleeve is provided with a guide hole. When the valve disc sealing surface and the valve seat sealing surface are about to close with a stroke of E, the medium flow hole and the guide hole on the limiting sleeve are mutually blocked. The upstream medium flows through the gap between the mating surface 1 of the valve seat guide sleeve and the limiting sleeve, and then enters the mating surface 4 of the hollow tube and the valve seat guide sleeve.

[0010] The labyrinth structure formed by the mating surface 1 of the limiting sleeve and the valve seat guide sleeve, the mating surface 2 of the bottom plane of the valve disc and the valve seat guide sleeve, the mating surface 3 of the lower end face of the valve disc guide sleeve and the outer surface of the valve seat, and the mating surface 4 of the hollow tube at the bottom of the valve disc and the inner hole of the valve seat guide sleeve, allows the medium flowing between the valve disc and the valve seat metal sealing surface to be depressurized through the labyrinth structure during the final stroke E of the switch.

[0011] The valve disc includes an open position where the valve disc sealing surface is located inside the valve disc guide sleeve, and a closed position where the valve disc sealing surface extends out of the lower end face of the valve disc guide sleeve and mates with the valve seat sealing surface as the valve disc moves downward.

[0012] The bottom step of the valve disc and the upper plane of the valve seat guide sleeve form a mating surface 2, which is ground to greatly improve its smoothness and achieve a high sealing level when they are fitted together.

[0013] An actuator is also provided at the top of the valve stem.

[0014] The beneficial effects of this invention are as follows: This invention provides a control and regulating valve for oil fields. By setting a valve seat guide sleeve at the valve seat location, the guide sleeve utilizes hydraulic principles to be pushed higher than the valve seat sealing surface by the medium after the valve is opened, ensuring sufficient protection against medium erosion of the valve seat sealing surface. When closed, the guide sleeve is moved by the bottom plane of the valve disc, exposing the valve seat sealing surface for a zero-leakage metal-to-metal seal with the valve disc sealing surface. A valve disc guide sleeve is also provided on the valve disc. Pushed by a disc spring, the guide sleeve remains lower than the valve disc sealing surface at the moment of opening, at a certain opening height, and in the fully open state, ensuring that the sealing surface is hidden within the guide sleeve and not eroded by the medium. The valve disc guide sleeve and valve seat guide sleeve are the main components subject to erosion; therefore, only the adjustment parts of these two parts need to be hardened. Martensitic quenching can be used to obtain high hardness, resulting in good performance and low cost. These two parts are very convenient to replace and can be used as spare parts. The valve's regulation and throttling functions are achieved by the relative position between the throttling orifice on the side of the hollow tube at the lower end of the valve disc and the valve seat guide sleeve. When the valve is in the initial regulation start position, regulation position, and fully open position, the upper end of the valve seat guide sleeve is always higher than the valve seat sealing surface position H, and the lower end of the valve disc guide sleeve is also lower than the valve disc sealing surface height H. The position of the valve disc throttling orifice is even lower by a height G. When the actual medium comes out of the valve disc throttling orifice, the distance from the valve disc sealing height is H+G, which effectively avoids the medium from scouring and cavitation damage to the valve disc sealing surface. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the structure for opening and closing the final E-stroke stage of the present invention.

[0017] Figure 3 This is a schematic diagram of the structure of the valve seat guide sleeve being pressed down during the final F-stroke stage when the valve is closed according to the present invention.

[0018] Figure 4 This is a schematic diagram of the structure of the present invention at the moment of entering the minimum flow rate adjustment state.

[0019] Figure 5 This is a schematic diagram of the adjustable state structure of the present invention.

[0020] Figure 6 This is a schematic diagram of the fully open state structure of the present invention.

[0021] Figure 7 This is a schematic diagram of the closed state structure of the present invention.

[0022] Figure 8 This is a schematic diagram of the limiting sleeve structure of the present invention.

[0023] Figure 9 This is a schematic diagram of the valve disc structure of the present invention.

[0024] Figure 10 This is a schematic diagram of the valve seat guide sleeve structure of the present invention.

[0025] Wherein: 1-valve body; 2-valve stem; 3-valve disc; 4-valve seat guide sleeve; 5-limiting sleeve; 6-mating surface 1; 7-mating surface 4; 8-mating surface 2; 9-mating surface 3; 10-valve disc guide sleeve; 11-valve seat flow passage; 12-lower cover; 2-actuator; 31-disc spring assembly seat; 32-disc spring; 33-hollow tube; 34-throttle hole; 41-medium flow hole; 51-guide hole. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] An oilfield control valve includes a valve body 1, a valve stem 2 inside the valve body 1, a valve disc 3 at the end of the valve stem 2, a lower flow channel for medium entry and an upper flow channel for medium exit inside the valve body 1, the lower flow channel and the upper flow channel are connected by a valve seat flow channel port 11, the medium enters from the lower end and exits from the upper end, the pressure in the lower chamber is balanced and connected with the pressure in the middle chamber, and the huge medium thrust when the valve disc is closed is balanced. The valve seat flow passage 11 has an upward-facing valve seat sealing surface. A valve seat guide sleeve 4 is located below the valve seat flow passage 11, and a limiting sleeve 5 is located at the bottom of the valve seat guide sleeve 4. The valve seat guide sleeve 4 is floatingly installed between the valve seat flow passage 11 and the limiting sleeve 5. The valve seat guide sleeve 4 includes a fully open position where it is pushed higher than the valve seat sealing surface by the upstream medium after the valve is opened, preventing the medium from scouring the valve seat sealing surface; and a closed position where it is pushed down by the bottom step of the valve disc 3 when the valve is closed, exposing the valve seat sealing surface and sealing it with the valve disc 3 sealing surface. An actuator 21 is also provided at the top of the valve stem 2.

[0028] The valve seat flow passage 11 has a valve seat inner hole, and the valve seat inner hole has a step with diameters A and B. The valve seat guide sleeve 4 is limited and fitted with the step and sealed by an O-ring. Under the thrust of the upstream medium (the thrust of the pressure ring formed by A and B), the valve seat guide sleeve 4 is tightly pushed onto the step surface, so that the valve seat guide sleeve 4 is higher than the valve seat sealing surface H. This ensures that the valve seat guide sleeve 4 is higher than the valve seat sealing surface H at the moment of valve opening or during the opening process, in the regulating state, and in the fully open state, so as to avoid medium erosion or cavitation on the valve seat sealing surface.

[0029] The valve body 1 has a lower cover 12 at its bottom, and the limiting sleeve is installed on the lower cover 12.

[0030] A valve disc guide sleeve 10 is provided on the outer side of the valve disc 3. The valve disc guide sleeve 10 is installed on the step at the middle end of the valve disc 3 by means of an O-ring. Since the downstream medium cannot enter the closed space formed by the step and the two O-rings due to the sealing of the O-ring, when there is medium downstream, the medium pressure (the pressure on the annular surface formed by C and D) presses the valve disc guide sleeve onto the middle step of the valve disc and effectively resists the thrust of the medium force on the bottom of the guide sleeve, ensuring that the lower end face of the valve disc guide sleeve is always lower than the valve disc sealing height H.

[0031] The outer side of the valve disc 3 is also provided with a disc spring seat 31. The disc spring seat 31 is threadedly connected to the valve disc 3 and equipped with an O-ring seal. The disc spring seat, the valve disc and the O-ring seal between them form a sealed and fixed rigid body that moves up and down together with the valve disc. A disc spring is also provided between the disc spring assembly seat and the valve disc guide sleeve. The valve disc and the valve disc guide sleeve are sealed by an O-ring. The disc spring, valve disc guide sleeve, and O-ring combine to form a movable body that moves axially within the rigid annular groove between the disc spring assembly seat and the middle step of the valve disc. When the valve disc is in a small-opening throttling state or a fully open state, the downstream medium pressure will press on the ring formed by the two O-rings of the valve disc guide sleeve (the ring formed by C and D), pressing the valve disc guide sleeve onto the step of the valve disc. This ensures that when the valve disc is open or in a small-opening state, the guide sleeve will not be pushed upward by the medium force to compress the disc spring, thus failing to protect the valve disc sealing surface. The downstream medium pressure and the preload of the disc spring assembly can ensure that the valve disc protection sleeve is in the optimal protection position regardless of the operating pressure. This is because the higher the medium pressure, the higher the downstream medium pressure, and the greater the medium force pressing on the valve disc guide sleeve.

[0032] The lower end of the valve disc 3 is also configured as a hollow tube 33. The side of the hollow tube 33 is provided with a throttling hole 34 to precisely adjust the flow rate and change the flow direction of the medium, making it flow horizontally to avoid the metal sealing cone surfaces of the valve seat and valve disc, and also to avoid a certain distance G between the upper end face of the valve seat guide sleeve and the lower end face of the valve disc guide sleeve. This slows down or avoids scouring of the two guide sleeves when fully open, reducing the frequency of parts replacement. The lower cylindrical side of the valve seat guide sleeve 4 is provided with a medium flow hole 41, which then cooperates with the limiting sleeve on the lower cover. The upper part of the limiting sleeve 5 is provided with a guide hole 51. When the valve disc sealing surface and the valve seat sealing surface are about to close with a stroke of E, the medium flow hole 41 and the guide hole 51 on the limiting sleeve 5 are mutually blocked. The upstream medium flows through the gap between the mating surface 16 of the valve seat guide sleeve 4 and the limiting sleeve 5, and then enters the mating surface 47 of the hollow tube 33 and the valve seat guide sleeve 4. However, the gaps at these two points are very small, so the flow rate of the medium entering between the valve seat and the valve disc sealing surface is very slow at this time, and it will not cause erosion and cavitation on the metal sealing conical surface seal at the moment of closure. Because when the valve disc and the valve seat metal sealing conical surface seal closes at the end of the E stroke, the limiting sleeve and the valve seat guide sleeve have already cylindrically fitted, and the guide hole is closed; the lower tubular outer circle of the valve disc and the inner hole of the valve seat guide sleeve also fit tightly against the mating surface 4. After the medium passes through these two tiny gaps, no large flow of medium enters. The bottom step of the valve disc contacts the upper plane of the valve seat guide sleeve, and only a small amount of medium can enter the periphery of the metal sealing conical surface seal. The bottom plane of the valve disc guide sleeve at the outlet end is also firmly pressed onto the plane outside the valve body and valve seat, forming a certain sealing level III. Therefore, during the final stroke E of the valve disc sealing surface and the valve seat sealing surface, very little medium flows between the conical seal of the valve disc and the valve seat metal sealing pair. This flow is also limited by the four tightly fitting surfaces: the labyrinth formed by the mating surface 1 of the limiting sleeve and the valve seat guide sleeve, the mating surface 2 of the bottom plane of the valve disc and the upper end face of the valve seat guide sleeve, the mating surface 3 of the lower end face of the valve disc guide sleeve and the outer surface of the valve seat, and the mating surface 4 of the lower tubular outer circle of the valve disc and the inner hole of the valve seat guide sleeve. Before the valve disc sealing surface is fully sealed with the valve seat, its gap is always larger than the other four tightly fitting surfaces, resulting in a very low flow velocity and providing excellent protection for the sealing surface. Furthermore, the stroke E, or even the larger stroke H, is relatively short, enabling closure in a very short time and effectively protecting the valve metal sealing pair.After the valve enters the minimum flow regulation state, when the valve disc opens further, the mating surface 3 of the valve disc guide sleeve with the outer circular plane of the valve seat and the mating surface 2 of the upper end face of the valve seat guide sleeve with the bottom face of the valve disc simultaneously separate to regulate and control the flow. At this time, during the process of full opening or the entire working process, the end face of the valve seat guide sleeve is always higher than the valve seat sealing surface H, and the lower end face of the valve disc guide sleeve is always lower than the bottom face H of the valve disc. This situation forms that the sealing surfaces of the valve disc and the valve seat are hidden outside the high-speed flowing medium during the entire working process, and are not eroded or worn, which greatly improves the service life of the valve.

[0033] The valve disc 3 includes an open position where the valve disc sealing surface is located inside the valve disc guide sleeve 10, and a closed position where the valve disc sealing surface extends out of the lower end face of the valve disc guide sleeve 10 and cooperates with the valve seat sealing surface as the valve disc 3 moves downward.

[0034] The bottom plane of the valve disc 3 and the upper plane of the valve seat guide sleeve 4 form a mating surface 28, which is ground to greatly improve its smoothness. When they are fitted together, they will also have a high sealing level of IV. In particular, the annular surface formed by the valve seat guide sleeves A and B is subjected to a large medium thrust. The greater the valve pressure, the greater this pressure is, which is more conducive to improving the sealing specific pressure of this mating surface to improve the sealing level. After it is basically sealed, the amount of medium entering the valve main sealing cone sealing pair is very small and the pressure is also very low.

[0035] The valve's stroke before closing or opening is F+L, with H and E included within F. When the valve closes and enters stroke F, mating surfaces 2, 3, and 4 are all simultaneously engaged, and the flow rate no longer changes. Further into the final stroke E, mating surface 1 engages, further weakening the inlet medium's velocity and pressure. Therefore, the medium velocity is relatively low and the closing time is very fast when the valve's metal seal finally engages. If the valve opens, the valve's metal seal surfaces disengage. When the disengagement stroke is less than E, the medium entering the metal seal area passes through mating surfaces 1, 2, and 4. The flow rate is small, and the labyrinth effect significantly reduces pressure. The very small gap at the outlet mating surface 3 also provides excellent resistance and pressure reduction. With such a small gap, very little medium can flow out, resulting in a very low velocity between the valve's metal seal surfaces. Throughout the entire opening stroke F, the mating surfaces maintain their resistance and pressure-reducing function. When the valve is within the L stroke range, only mating surface 4 is in contact, and the flow rate is very small, so it is not considered part of the flow rate regulation range. At this point, the metal conical seal is fully open and protected by the upper and lower guide sleeves, preventing erosion. The flow rate of this L+F stroke is very small and is not considered part of the valve's flow rate regulation range. Therefore, the F+L stroke represents the zero-point dry stroke of this control valve and is not used as the working area for flow rate regulation. This ingenious design of the zero-point dry stroke effectively protects the valve's metal sealing surfaces from erosion and damage by the high-speed medium at the moment of opening, thus effectively extending its service life.

[0036] When fully closed, this valve actually has five layers of sealing function. The sealing level at mating surface 1 is Class II, at mating surface 2 it is Class IV, at mating surface 3 it is Class III, and at mating surface 4 it is Class II. The main valve sealing cone surface has zero leakage. Furthermore, the four other seals provide beneficial protection for the main seal, extending its service life. During the E stroke of the valve, mating surfaces 1, 2, 3, and 4 simultaneously protect the main seal. During the FE stroke, mating surfaces 2, 3, and 4 provide protection. When the valve disc stroke is greater than or equal to F, the lower end face of the valve disc guide is lower than the bottom surface H of the valve disc, and the upper end face of the valve seat guide sleeve is higher than the valve seat sealing surface H, effectively protecting the valve disc and valve seat sealing surfaces from erosion and cavitation. Therefore, throughout the entire valve's opening and closing stroke, the main sealing pair is effectively protected from direct erosion.

[0037] Please note to all technical personnel: Although the present invention has been described according to the specific embodiments above, the inventive concept of the present invention is not limited to this invention. Any modifications that utilize the inventive concept will be included within the scope of patent protection of this patent.

[0038] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A control and regulating valve for oilfield use, comprising a valve body (1), wherein a valve stem (2) is provided inside the valve body (1), and a valve disc (3) is provided at the end of the valve stem (2), characterized in that, The valve body (1) is provided with a lower flow channel for medium entry and an upper flow channel for medium exit. The lower flow channel and the upper flow channel are connected by a valve seat flow channel port (11). An upward valve seat sealing surface is provided on the valve seat flow channel port (11). A valve seat guide sleeve (4) is provided below the valve seat flow channel port (11). A limiting sleeve (5) is also provided at the bottom of the valve seat guide sleeve (4). The valve seat guide sleeve (4) is floating between the valve seat flow channel port (11) and the limiting sleeve (5). The valve seat guide sleeve (4) includes a fully open position where the valve is pushed up above the valve seat sealing surface by the medium after the valve is opened, so as to avoid the medium from scouring the valve seat sealing surface, and a closed position where the valve seat guide sleeve (4) is pushed downward by the bottom step of the valve disc (3) when the valve is closed, so that the valve seat sealing surface is exposed and seals with the valve disc (3) sealing surface.

2. The control and regulating valve for oilfield use according to claim 1, characterized in that, The valve seat flow passage (11) has a valve seat inner hole, and the valve seat inner hole has a step. The valve seat guide sleeve (4) is limited and matched with the step and sealed by an O-ring. Under the thrust of the upstream medium, the valve seat guide sleeve (4) is tightly pushed onto the step surface, so that the valve seat guide sleeve (4) is higher than the valve seat sealing surface H. This ensures that the valve seat guide sleeve (4) is higher than the valve seat sealing surface H at the moment of valve opening or during the opening process, or in the fully open state, so as to avoid medium erosion or cavitation on the valve seat sealing surface.

3. The control and regulating valve for oilfield use according to claim 1, characterized in that, The valve body (1) has a lower cover (12) at its bottom, and the limiting sleeve is installed on the lower cover (12).

4. The control and regulating valve for oilfield use according to claim 1, characterized in that, The valve disc (3) is provided with a valve disc guide sleeve (10) on its outer side, and the valve disc guide sleeve (10) is installed on the step in the middle of the valve disc (3).

5. The control and regulating valve for oilfields according to claim 4, characterized in that, The valve disc (3) is also provided with a disc spring seat (31) on the outside. The disc spring seat (31) is threadedly connected to the valve disc (3) and sealed with an O-ring. The disc spring seat (31), the valve disc (3) and the O-ring between them form a sealed and fixed rigid body that moves up and down together with the valve disc (3).

6. The control and regulating valve for oilfield use according to claim 1, characterized in that... A disc spring (32) is provided between the disc spring assembly seat (31) and the valve disc guide sleeve (10). The valve disc (3) and the valve disc guide sleeve (10) are sealed by an O-ring. The disc spring (32), the valve disc guide sleeve (10) and the O-ring are combined to form a movable body that moves axially within the rigid annular groove between the disc spring assembly seat (31) and the middle step of the valve disc (3).

7. The control and regulating valve for oilfield use according to claim 4, characterized in that, The lower end of the valve disc (3) is also provided as a hollow tube (33), and the side of the hollow tube (33) is provided with a throttling hole (34). The lower cylindrical side of the valve seat guide sleeve (4) is provided with a medium flow hole (41), and the upper part of the limiting sleeve (5) is provided with a guide hole (51). When the valve disc sealing surface and the valve seat sealing surface are about to close and there is still a stroke of E, the medium flow hole (41) and the guide hole (51) on the limiting sleeve (5) are mutually shielded. The upstream medium flows through the gap between the mating surface 1 (6) of the valve seat guide sleeve (4) and the limiting sleeve (5), and then enters the mating surface 4 (7) of the hollow tube (33) and the valve seat guide sleeve (4).

8. The control and regulating valve for oilfield use according to claim 7, characterized in that, The limiting sleeve (5) and the valve seat guide sleeve (4) have a mating surface 1 (6), the bottom plane of the valve disc (3) and the valve seat guide sleeve (4) have a mating surface 2 (8), the lower end face of the valve disc guide sleeve (10) and the outer surface of the valve seat have a mating surface 3 (9), and the hollow tube (33) at the bottom of the valve disc (3) and the inner hole of the valve seat guide sleeve (4) form a labyrinth structure. During the final stroke E of the switch, the medium flowing between the valve disc (3) and the metal sealing surface of the valve seat is depressurized through the labyrinth structure.

9. The control and regulating valve for oilfield use according to claim 4, characterized in that, The valve disc (3) includes an open position where the valve disc sealing surface is located inside the valve disc guide sleeve (10) and a closed position where the valve disc sealing surface extends out of the lower end face of the valve disc guide sleeve (10) and mates with the valve seat sealing surface as the valve disc (3) moves downward.

10. The control and regulating valve for oilfield use according to claim 2, characterized in that, The bottom step of the valve disc (3) and the upper plane of the valve seat guide sleeve (4) form a mating surface 2 (8). The surface is ground to greatly improve its smoothness and also to achieve a high sealing level when they are fitted together.

11. The control and regulating valve for oilfield use according to claim 1, characterized in that, An actuator (21) is also provided at the top of the valve stem (2).

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