A special thread joint with air-tightness

Abstract

The application discloses a special thread joint capable of being repeatedly disassembled and sealed, and belongs to the technical field of threaded connection of drilling and completion tools, and comprises an outer thread joint, an inner thread joint, a secondary sealing structure, a connecting mechanism and a primary sealing structure. Under the action of the connecting mechanism, the secondary sealing structure and the primary sealing structure are sealed. The secondary sealing structure is located at the left side of the connecting mechanism, and the primary sealing structure is located at the right side of the connecting mechanism. In the application, the thread is improved in the form of a trapezoidal thread, and the thread has the characteristics of high tensile strength and easy make-up. The primary and secondary sealing surfaces adopt a conical surface-to-conical surface structure, and have the advantages of easy processing and measurement, low processing cost and high controllability of quality. The primary and secondary double sealing structure is adopted, and the sealing reliability is good. The primary sealing adopts a self-tightening sealing form, and the higher the pressure is, the better the sealing reliability is. The thread is positioned by a positioning step, and the make-up torque does not need to be controlled, so that the thread can be repeatedly used and is convenient to use.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of threaded connections for drilling and completion tools, and particularly relates to a special gas seal threaded joint capable of being repeatedly disassembled and assembled. BACKGROUND

[0002] With the vigorous development of clean energy such as natural gas, the application of gas seal threads in gas wells is becoming more and more widespread, especially in underground gas storage and high-sulfur natural gas wells. The sealing performance requirements for threaded connection parts of pipe string joints are becoming higher and higher, and the threaded connection part is the weakest link in the sealing of the entire pipe string.

[0003] The sealing forms of the commonly used threaded connections mainly include the following two types: the first type is to realize sealing through non-metallic sealing elements, such as rubber O-shaped sealing rings and non-elastic sealing polytetrafluoroethylene pads. The second type is a metal threaded sealing joint. The non-metallic sealing elements can be manufactured to a high degree, but their service life cannot be effectively controlled, especially in harsh conditions such as high temperature, high pressure and high corrosion in the downhole, which has the characteristics of poor reliability and easy failure, and cannot meet the existing demand. The metal threaded sealing joint often adopts the API gas seal threaded joint type. This thread conforms to the API (American Petroleum Institute) standard. The make-up torque needs to be strictly controlled when the thread is tightened. The sealing failure caused by insufficient or excessive make-up torque often occurs on site, and the joint form is easy to stick, which makes it only be used once. At the same time, the design concept of the completion tool is gradually changing to large inner diameter and small outer diameter to meet the requirements of good running and large inner diameter. Due to the structural characteristics of the API gas seal thread, it is mainly used for the connection between the upper and lower ends of the tool and the oil casing, and cannot be applied to the connection of the parts in the tool, so it is necessary to independently develop a suitable gas seal threaded joint to meet the on-site use requirements.

[0004] US 7988205 B2 discloses a wedge-shaped threaded joint with a torque shoulder, which is provided with a metal sealing structure in the form of a conical surface / conical surface. At the same time, the male joint and the female joint are processed with wedge-shaped threads. The thread tooth width of the male joint gradually increases from front to back, and the thread tooth width of the female joint gradually decreases from front to back. After the joint is tightened, the threads on both sides are in close contact to form a sealing effect. The advantages of this invention are that the sealing effect of the metal sealing structure is enhanced. The disadvantages are that the thread cannot be processed with a forming tool, the processing speed is very slow, and the processing cost is high.

[0005] Patent CN 108952595 A discloses a gas seal threaded joint, which adopts a three-seal structure form, the sealing structure adopts a conical surface-conical surface and spherical surface-spherical surface sealing form, the sealing surfaces are tightly attached after the threaded joint is tightened, and the sealing effect is formed.

[0006] Based on the above-mentioned defects 1: the thread cannot be machined using a forming tool, the machining speed is very slow, and the machining cost is high; defect 2: the machining is complex, the position and profile of the three sealing surfaces are required to be high, if deviation occurs, the three seals cannot simultaneously produce a sealing effect, and a negative effect may occur; at the same time, there are still some defects based on the secondary sealing technology, only relying on the inclined positioning shoulder to support the sealing, gaps are still easy to appear, and the gas sealing effect is poor after long time use, therefore, a repeatedly dismountable gas sealing special threaded joint is needed to solve the above-mentioned problems. SUMMARY

[0007] (I) Technical problems solved

[0008] In order to overcome the above-mentioned defects of the prior art, the present application provides a repeatedly dismountable gas sealing special threaded joint, which solves the problems that the thread cannot be machined using a forming tool, the machining speed is very slow, the machining cost is high, the joint machining is complex, the position and profile of the three sealing surfaces are required to be high, if deviation occurs, the three seals cannot simultaneously produce a sealing effect, a negative effect may occur, and only relying on the inclined positioning shoulder to support the sealing, gaps are still easy to appear, and the gas sealing effect is poor after long time use.

[0009] The purpose of the present application is to provide a repeatedly dismountable gas sealing special threaded joint to solve the technical problems in the prior art that the sealing reliability is poor, the machining and detection are difficult, and the large inner diameter and small outer diameter requirements cannot be met.

[0010] (II) Technical solutions

[0011] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: a repeatedly dismountable gas sealing special threaded joint, comprising an outer threaded joint, an inner threaded joint, a secondary sealing structure, a connecting mechanism and a primary sealing structure, under the action of the connecting mechanism, the secondary sealing structure and the primary sealing structure realize sealing, the secondary sealing structure is located on the left side of the connecting mechanism, and the primary sealing structure is located on the right side of the connecting mechanism.

[0012] The auxiliary sealing structure comprises a positioning mechanism and a supporting mechanism, the positioning mechanism is arranged between the outer threaded joint and the inner threaded joint, the right side of the positioning mechanism is fixed to the left side of the inner threaded joint, the positioning mechanism is designed in a circular truncated cone shape and the diameter of the left side is larger than the diameter of the right side, and the supporting mechanism is fixed to the right side surface of the outer threaded joint, and the positioning mechanism is located on the inner side of the supporting mechanism.

[0013] As a further scheme of the present application, the connecting mechanism adopts a threaded connection form, and the thread is a modified trapezoidal straight thread structure.

[0014] As a further scheme of the present application, the modified trapezoidal outer thread comprises an outer thread guide surface and an outer thread bearing surface, the outer thread guide surface is connected to the tooth top through a secondary transition arc I, and the radius R3 thereof is 0.45-0.55 mm.

[0015] The outer thread bearing surface is connected to the tooth top through a secondary transition arc II, and the radius R1 thereof is 0.10-0.20 mm.

[0016] The outer thread guide surface and the outer thread bearing surface are connected to the tooth bottom through a secondary transition arc III, and the radius R2 thereof is 0.10-0.20 mm.

[0017] The outer thread guide surface forms an angle α of 20-25° with the vertical direction, the outer thread bearing surface forms an angle β of 1-5° with the vertical direction, and the outer thread tooth height h1 is 1.05-1.10 mm.

[0018] As a further scheme of the present application, the outer thread guide surface corresponds to the inner thread guide surface and is located on the inner threaded joint, the inner thread guide surface is connected to the tooth bottom through a secondary transition arc V, and the radius thereof is the same as R3.

[0019] The inner thread bearing surface is connected to the tooth bottom through a secondary transition arc IV, and the radius thereof is the same as R1.

[0020] The inner thread guide surface and the inner thread bearing surface are connected to the tooth top through a secondary transition arc VI, and the radius thereof is the same as R2.

[0021] The inner thread guide surface forms an angle equal to α with the vertical direction, the inner thread bearing surface forms an angle equal to β with the vertical direction, and the inner thread tooth height h2 is 1.05-1.10 mm and is equal to h1.

[0022] As a further scheme of the present application, the main sealing structure is composed of an inner thread main sealing surface located on the left inner side of the inner threaded joint and an outer tapered surface at the right end of the outer threaded joint.

[0023] The internal thread main sealing surface is conical, the axial center line of the internal thread joint is collinear with the axial center line, the included angle θ5 between the axial center line and the horizontal direction is 14°, and the horizontal direction length L4 is 11.00 mm;

[0024] The outer sealing conical surface at the right end of the external thread joint is composed of three sections, namely the main sealing first conical surface at the left side, the main sealing second conical surface at the middle, and the main sealing third conical surface at the right side, the axial center lines of the three sections are collinear, and the axial center line of the external thread joint is collinear with the axial center lines of the three sections;

[0025] The horizontal direction length of the main sealing first conical surface is 2.50 mm, the horizontal direction length of the main sealing second conical surface is 2.00 mm, the horizontal direction length of the main sealing third conical surface is 3.50 mm, the included angle between the main sealing first conical surface and the horizontal direction is θ1, the included angle between the main sealing second conical surface and the horizontal direction is θ2, the included angle between the main sealing third conical surface and the horizontal direction is θ3, and the values satisfy θ1< θ2< θ3, θ2= θ3-1, preferably θ1= 8°, θ2= 14°, and θ2= 15°;

[0026] A gap L5 of 2-3 mm is required between the right inner end surface of the internal thread main sealing surface and the right end surface of the outer sealing conical surface, and a chamfer is arranged between the main sealing third conical surface and the right end surface thereof.

[0027] As a further scheme of the application, the right inner side of the external thread joint is provided with an elastic groove in a cylindrical shape, the horizontal direction length L7 is 17.00-18.00 mm, and the thickness L6 is 4.50-4.60 mm;

[0028] The internal thread joint is hollow, the left inner cavity diameter is L8, the right elastic groove diameter is L9, and the values satisfy L8< L9-1.00 mm;

[0029] The main sealing mechanism and the connecting mechanism are provided with a grease storage cavity I, which is used for storing excess thread sealing grease;

[0030] The right side surface of the external thread joint is fixed with the left side surface of the conical surface embedding ring, the conical surface embedding ring is embedded in the conical surface embedding groove, and the conical surface embedding groove is arranged at the right side of the inner wall of the internal thread joint.

[0031] As a further scheme of the application, the auxiliary sealing structure is composed of an auxiliary sealing surface I, an auxiliary sealing surface II, an auxiliary transition arc I, an auxiliary transition arc II, a positioning mechanism, and a supporting mechanism;

[0032] The auxiliary transition arc I is tangent to the auxiliary sealing surface I, the auxiliary transition arc II is tangent to the auxiliary sealing surface II, the auxiliary sealing surface I is an inverted inner taper, the angle θ4 between the auxiliary sealing surface I and the horizontal direction is 45° or 30°, the auxiliary sealing surface II is an outer taper, the angle θ4 between the auxiliary sealing surface II and the horizontal direction is 45° or 30°, and the horizontal angle of the auxiliary sealing surface I is equal to that of the auxiliary sealing surface II.

[0033] The inner side of the auxiliary sealing structure is provided with a grease storage cavity II for storing excess thread sealing grease.

[0034] As a further scheme of the present application, the positioning mechanism comprises an embedded ring, the right side surface of the embedded ring is fixed to the left side surface of the internal thread structure, and the embedded ring is designed to be inclined and has an angle of 20°-30° with the horizontal direction, the embedded ring is embedded in an embedded groove, the embedded groove is arranged on the inner side of the external thread joint, a rubber pad is arranged on the inner bottom of the embedded groove, the rubber pad is overlapped with the left side of the embedded ring, and a gasket is arranged on the outer wall of the embedded groove.

[0035] The outer wall of the embedded ring is provided with a first spherical sealing surface and a second spherical sealing surface, the first spherical sealing surface is located on the left side of the second spherical sealing surface, and the spherical cap height of the first spherical sealing surface is greater than that of the second spherical sealing surface.

[0036] As a further scheme of the present application, the supporting mechanism comprises a supporting ring, the left side surface of the supporting ring is fixed to the right side of the external thread joint, the supporting ring is embedded in a rubber ring groove, and the inner circle and the outer circle of the supporting ring are all provided with five groups of sealing rubber rings, the five groups of sealing rubber rings are embedded in five groups of blocking grooves, and the five groups of blocking grooves are arranged on the inner circle and the outer circle of the rubber ring groove.

[0037] As a further scheme of the present application, the axial interference amount of the sealing surface of the main sealing structure is 0.40-0.50 mm, and the positioning shoulder I and the positioning shoulder II constitute an extrusion sealing surface.

[0038] (Three) beneficial effects

[0039] Compared with the prior art, the present application has the beneficial effects that:

[0040] 1. In the present application, the thread adopts a modified trapezoidal type, the normal angle of the bearing surface is 1-5°, the normal angle of the guide surface is 20-25°, the thread has the characteristics of strong tensile capacity and easy make-up, the main and auxiliary sealing surfaces adopt a conical surface to conical surface structure, which is easy to process and measure, has low processing cost and high quality controllability, adopts a main and auxiliary double sealing structure, has good sealing reliability, adopts a self-tightening sealing form, the higher the pressure, the better the sealing reliability, and the thread meets the on-site use requirements, adopts positioning steps for positioning, does not need to control the make-up torque, can be repeatedly used for many times, and is convenient to use.

[0041] 2、In the application, through the cooperation between the positioning mechanism and the supporting structure, the positioning shoulder I and the positioning shoulder II are close to each other, the supporting ring is embedded into the rubber ring groove, the sealing rubber ring is embedded into the blocking groove and the rubber ring groove, the connection air tightness is further increased through the arrangement of multiple sealing rubber rings and blocking grooves, the embedded ring is designed to be inclined, the first spherical sealing surface and the second spherical sealing surface are arranged on the outer ring, the first spherical sealing surface is located on the left side of the second spherical sealing surface, the spherical cap height of the first spherical sealing surface is greater than that of the second spherical sealing surface, the first spherical sealing surface is deformed in the embedded groove in the outer threaded joint, the second spherical sealing surface does not deform, and the contact pressure borne by the second spherical sealing surface is greater than that of the first spherical sealing surface, when the special threaded joint bears excessive load and the first spherical sealing surface yields and loses sealing capacity, the second spherical sealing surface remains in the elastic deformation range, so that the special threaded joint does not leak, and the sealing capacity and reliability of the special threaded joint are greatly improved through the cooperation between the first spherical sealing surface and the second spherical sealing surface. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is the assembly profile view of the outer threaded joint and the inner threaded joint of the application;

[0043] Figure 2 It is the schematic view of the outer threaded joint of the application;

[0044] Figure 3 It is the schematic view of the inner threaded joint of the application;

[0045] Figure 4 It is the schematic view of the local structure of the connecting mechanism of the application;

[0046] Figure 5 It is the schematic view of the section structure of the connecting mechanism of the application;

[0047] Figure 6 It is the local schematic view of the main sealing structure of the application;

[0048] Figure 7 It is the schematic view of the section structure of the outer threaded joint of the application;

[0049] Figure 8 It is the contact stress distribution diagram at the main sealing structure of the application;

[0050] Figure 9 It is the equivalent stress distribution diagram at the main sealing structure of the application;

[0051] In the diagram: 1. External threaded connector; 2. Internal threaded connector; 3. Secondary sealing structure; 4. Connecting mechanism; 5. Main sealing structure; 301. Secondary sealing surface I; 302. Secondary transition arc I; 303. Grease cavity II; 304. Positioning shoulder I; 305. Positioning shoulder II; 306. Secondary sealing surface II; 307. Secondary transition arc II; 308. Positioning mechanism; 3081. Embedded ring; 3082. First spherical sealing surface; 3083. Secondary spherical sealing surface; 3084. Rubber gasket; 3085. Embedded groove; 309. Support mechanism; 3091. Support ring; 3092. Sealing rubber ring; 3093. Rubber ring groove 3094, retaining groove; 401, secondary transition arc I; 402, external thread guide surface; 403, secondary transition arc II; 404, external thread bearing surface; 405, secondary transition arc III; 406, internal thread bearing surface; 407, secondary transition arc IV; 408, secondary transition arc V; 409, internal thread guide surface; 410, secondary transition arc VI; 501, first conical surface of main seal; 502, second conical surface of main seal; 503, third conical surface of main seal; 504, chamfer; 505, main sealing surface of internal thread; 506, grease cavity I; 507, elastic groove; 508, conical insert ring; 509, conical groove. Detailed Implementation

[0052] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0053] like Figures 1-9 As shown, the present invention provides a technical solution: a reusable and detachable gas-tight special threaded joint, including an external threaded joint 1, an internal threaded joint 2, a secondary sealing structure 3, a connecting mechanism 4, and a main sealing structure 5. Under the action of the connecting mechanism 4, the secondary sealing structure 3 and the main sealing structure 5 achieve sealing. The secondary sealing structure 3 is located on the left side of the connecting mechanism 4, and the main sealing structure 5 is located on the right side of the connecting mechanism 4.

[0054] The secondary sealing structure 3 includes a positioning mechanism 308 and a support mechanism 309. The positioning mechanism 308 is located between the external threaded joint 1 and the internal threaded joint 2, and the right side of the positioning mechanism 308 is fixed to the left side of the internal threaded joint 2. The positioning mechanism 308 is a frustum-shaped design with the left diameter being larger than the right diameter. The support mechanism 309 is fixed to the right side of the external threaded joint 1, and the positioning mechanism 308 is located inside the support mechanism 309.

[0055] Specifically, such as Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, the connecting mechanism 4 adopts a threaded connection, and the thread is a modified trapezoidal straight thread structure.

[0056] The modified buttress external thread comprises an external thread guide surface 402 and an external thread load bearing surface 404, the external thread guide surface 402 is connected with the tooth top through a secondary transition arc I 401, and the radius R3 thereof is 0.45-0.55 mm.

[0057] The external thread load bearing surface 404 is connected with the tooth top through a secondary transition arc II 403, and the radius R1 thereof is 0.10-0.20 mm.

[0058] The external thread guide surface 402 and the external thread load bearing surface 404 are connected with the tooth root through a secondary transition arc III 405, and the radius R2 thereof is 0.10-0.20 mm.

[0059] The angle α between the external thread guide surface 402 and the vertical direction is 20-25°, so as to improve the thread connection performance, the angle β between the external thread load bearing surface 404 and the vertical direction is 1-5°, so as to improve the thread tensile strength, avoid the decrease of the interference amount of the sealing surface under the action of the axial tension load, and cause the leakage, and the external thread tooth height h1 is 1.05-1.10 mm.

[0060] The external thread guide surface 402 corresponds to the internal thread guide surface 409, and is located on the internal thread joint 2, the internal thread guide surface 409 is connected with the tooth root through a secondary transition arc V 408, so as to avoid the stress concentration of the thread root and damage, and the radius thereof is the same as R3.

[0061] The internal thread load bearing surface 406 is connected with the tooth root through a secondary transition arc IV 407, so as to avoid the stress concentration of the thread root and damage, and the radius thereof is the same as R1.

[0062] The internal thread guide surface 409 and the internal thread load bearing surface 406 are connected with the tooth top through a secondary transition arc VI 410, and the radius thereof is the same as R2.

[0063] The angle between the internal thread guide surface 409 and the vertical direction is equal to α, the angle between the internal thread load bearing surface 406 and the vertical direction is equal to β, and the internal thread tooth height h2 is 1.05-1.10 mm and is equal to h1, so as to minimize the tooth height under the premise of meeting the thread tensile strength, avoid the decrease of the effective residual wall thickness of the joint, and thus reduce the overall tensile strength of the joint.

[0064] The main sealing structure 5 is composed of an internal thread main sealing surface 505 located inside the left side of the internal thread joint 2 and an external taper surface of the right end of the external thread joint 1.

[0065] The internal thread main sealing surface 505 is conical, the axial center line thereof is collinear with the axial center line of the internal thread joint 2, and the angle θ5 between the horizontal direction center axis thereof and the horizontal direction is 14°, and the horizontal direction length L4 thereof is 11.00 mm.

[0066] Specifically, as Figure 1 , Figure 2 ,Figure 6 and Figure 7 As shown in the figure, the outer sealing cone surface at the right end of the external thread joint 1 is composed of three sections, namely the main sealing first cone surface 501 at the left side, the main sealing second cone surface 502 at the middle, and the main sealing third cone surface 503 at the right side. The axial lines of the three sections are collinear, and the axial line of the external thread joint 1 is collinear.

[0067] The horizontal length of the main sealing first cone surface 501 is 2.50 mm, the horizontal length of the main sealing second cone surface 502 is 2.00 mm, the horizontal length of the main sealing third cone surface 503 is 3.50 mm, the angle between the main sealing first cone surface 501 and the horizontal direction is θ1, the angle between the main sealing second cone surface 502 and the horizontal direction is θ2, the angle between the main sealing third cone surface 503 and the horizontal direction is θ3, and the values satisfy θ1 < θ2 < θ3, θ2 = θ3 - 1. Preferably, θ1 = 8°, θ2 = 14°, and θ3 = 15°. This structure can effectively ensure that the main sealing second cone surface and the internal thread main sealing surface 505 are tightly fitted in the tightened state, accurately control the contact length of the contact surface, uniformly distribute the contact stress, and have high sealing reliability.

[0068] A gap L5 of 2-3 mm is required between the right inner end surface of the internal thread main sealing surface 505 and the right end surface of the outer sealing cone surface, so that the main sealing cone surface can deform freely and ensure the axial interference amount. A chamfer 504 is provided between the main sealing third cone surface 503 and the right end surface thereof to avoid damage to the internal thread main sealing surface 505 during assembly.

[0069] An elastic groove 507 is provided on the inner side of the right end of the external thread joint 1, which is in a cylindrical shape, with a horizontal length L7 of 17.00-18.00 mm and a thickness L6 of 4.50-4.60 mm. The elastic groove 507 can cause the main sealing first cone surface 501, the main sealing second cone surface 502, and the main sealing third cone surface 503 to elastically bend and deform rather than plastically deform under a given axial interference amount, so as to achieve a set initial sealing specific pressure. During operation, the internal high-pressure fluid extrudes the inner wall of the elastic groove 507, so that the main sealing second cone surface 502 and the internal thread main sealing surface 505 are more tightly fitted, thereby further increasing the contact pressure to achieve a self-tightening sealing effect.

[0070] The internal thread joint 1 is hollow, with a left inner cavity diameter L8 and a right elastic groove 507 diameter L9, and the values satisfy L8 < L9 - 1.00 mm, so as to ensure that the internal thread main sealing surface 505 can elastically bend and deform under a given axial interference amount and achieve a set initial sealing specific pressure.

[0071] The main sealing mechanism is provided with a grease storage cavity 1506 between the main sealing mechanism and the connecting mechanism 4, which is used to store excess thread sealing grease. After the joint is tightened, the excess thread sealing grease on the sealing surface of the main sealing mechanism can enter the grease storage cavity 1506, so as to avoid affecting the contact pressure of the main sealing surface due to the excessively high pressure of the thread sealing grease, and also to play an auxiliary sealing role.

[0072] The right side surface of the external thread joint 1 is fixed with the left side surface of the conical surface insert ring 508, and the conical surface insert ring 508 is embedded in the conical surface insert groove 509 which is arranged on the right side of the inner wall of the internal thread joint 2.

[0073] The auxiliary sealing structure 3 is composed of an auxiliary sealing surface I 301, an auxiliary sealing surface II 306, an auxiliary transition arc I 302, an auxiliary transition arc II 307, a positioning mechanism 308 and a supporting mechanism 309.

[0074] The auxiliary transition arc I 302 is tangent to the auxiliary sealing surface I 301, so as to avoid stress concentration. The auxiliary transition arc II 307 is tangent to the auxiliary sealing surface II 306, so as to avoid stress concentration, and also to avoid damaging the auxiliary sealing surface I 301 during assembly. The auxiliary sealing surface I 301 is an inverted inner cone, and the included angle θ4 between the auxiliary sealing surface I 301 and the horizontal direction is 45° or 30°. The auxiliary sealing surface II 306 is an outer cone, and the included angle θ4 between the auxiliary sealing surface II 306 and the horizontal direction is 45° or 30°, which is equal to the horizontal inclination angle of the auxiliary sealing surface I 301. The sealing structure has high reliability.

[0075] The inner side of the auxiliary sealing structure 3 is provided with a grease storage cavity II 303 which is used to store excess thread sealing grease. After the joint is tightened, the excess thread sealing grease on the sealing surface of the auxiliary sealing structure 3 can enter the grease storage cavity II 303, so as to avoid affecting the contact pressure of the auxiliary sealing surface due to the excessively high pressure of the thread sealing grease, and also to play an auxiliary sealing role.

[0076] Specifically, as shown in Figs. Figure 1 , Figure 2 and Figure 3 , the positioning mechanism 308 includes an embedded ring 3081, the right side surface of the embedded ring 3081 is fixed with the left side surface of the internal thread structure, and the embedded ring 3081 is designed to be inclined, and the included angle with the horizontal direction is 20°-30°. The embedded ring 3081 is embedded in the embedded groove 3085, and the embedded groove 3085 is arranged on the inner side of the external thread joint 1. The inner bottom of the embedded groove 3085 is provided with a rubber pad 3084, and the rubber pad 3084 is overlapped with the left side of the embedded ring 3081. The inner wall of the embedded groove 3085 is provided with a gasket.

[0077] The outer wall of the embedding ring 3081 is provided with a first spherical sealing surface 3082 and a second spherical sealing surface 3083, the first spherical sealing surface 3082 is located at the left side of the second spherical sealing surface 3083, and the spherical cap height of the first spherical sealing surface 3082 is greater than that of the second spherical sealing surface 3083.

[0078] The support mechanism 309 comprises a support ring 3091, the left side surface of the support ring 3091 is fixed with the right side of the external thread joint 1, the support ring 3091 is embedded in a rubber ring groove 3093, the inner ring and the outer ring of the support ring 3091 are provided with five groups of sealing rubber rings 3092, and the five groups of sealing rubber rings 3092 are embedded in five groups of blocking grooves 3094 respectively, and the five groups of blocking grooves 3094 are arranged at the inner ring and the outer ring of the rubber ring groove 3093 respectively.

[0079] The sealing surface axial interference amount of the main sealing structure 5 is 0.40-0.50mm, under the interference amount, the main sealing structure 5 can realize sealing and does not occur plastic deformation, so as to realize the characteristics of repeated disassembly and use, the positioning shoulder I 304 and the positioning shoulder II 305 constitute an extrusion sealing surface, ensure the contact stress distribution of the sealing surface and the strength of the sealing surface structure, and do not need to control the make-up torque, the operation is very convenient, and the reliability is high.

[0080] Embodiment:

[0081] In order to clearly show the effect of the application, the joint of Φ138.7x16.41mm P110 steel grade is taken as an example for description, and finite element simulation analysis is carried out.

[0082] The outer thread major diameter is Φ119.06mm, the inner thread minor diameter is 117.21mm, the main sealing surface interference amount is 0.40mm, the material is P110 steel grade, the yield strength is 756MPa, the tensile strength is 862MPa, the elastic modulus is 2.1e5MPa, and the sealing medium pressure is 105MPa.

[0083] When assembling, the external thread joint 1 is sleeved in the internal thread joint 2, and is guided, introduced and fastened through the connecting mechanism 4, so that the positioning shoulder I 304 and the positioning shoulder II 305 are tightly attached, so as to ensure that the main sealing structure 5 sealing surface axial interference amount is 0.40mm, at this time, the main sealing surface second taper surface is tightly attached with the internal thread main sealing surface 505, and is extruded with each other, contact stress is generated, at the same time, the excess thread grease on the main sealing structure 5 sealing surface can enter the grease cavity I 506, so as to avoid that the contact pressure of the internal thread main sealing surface 505 is affected due to the too high thread grease pressure, and also can play an auxiliary sealing role.

[0084] When the main sealing structure 5 is tightened, the secondary sealing surface I 301 and the secondary sealing surface II 306 of the secondary sealing structure 3 are tightly attached, sealing is achieved, and the excess thread sealant on the sealing surface of the secondary sealing structure 3 can enter the sealant cavity II 303, avoiding the influence of the contact pressure of the secondary sealing surface due to the excessive pressure of the thread sealant, and also playing an auxiliary sealing role.

[0085] After the external thread joint 1 and the internal thread joint 2 are tightened, the equivalent stress nephogram of the main sealing structure 5 is shown in Figure 9 , the maximum equivalent stress of the internal thread main sealing surface 505 is 559 MPa, which is less than the yield strength of the material, and the sealing surface structure only undergoes elastic deformation and does not undergo plastic deformation, thereby verifying the repeatable disassembly performance of the joint, and the joint does not stick after being disassembled and assembled multiple times. The contact stress distribution of the internal thread main sealing surface 505 is shown in Figure 8 , and the maximum contact stress is 771 MPa, which is greater than the sealing medium pressure, and can meet the sealing requirements.

[0086] In summary:

[0087] By using the modified trapezoidal thread, the normal angle of the bearing surface is 1-5°, and the normal angle of the guide surface is 20-25°. The thread has the characteristics of strong tensile capacity and easy make-up. The main and secondary sealing surfaces adopt a conical surface to conical surface structure, which is easy to process and measure, has low processing cost, and high quality controllability. The double sealing structure is adopted, and the sealing reliability is good. The main sealing adopts a self-tightening sealing form, and the higher the pressure, the better the sealing reliability. The thread adopts a positioning step for positioning, does not need to control the make-up torque, can be used repeatedly, and is easy to use.

[0088] Through the cooperation between the positioning mechanism 308 and the support structure, the positioning shoulder I 304 and the positioning shoulder II 305 are close to each other, the support ring 3091 is embedded in the rubber ring groove 3093, and the sealing rubber ring 3092 is embedded in the blocking groove 3094 and the rubber ring groove 3093, respectively. Through the arrangement of multiple sets of sealing rubber rings 3092 and blocking grooves 3094, the air tightness of the connection is further increased. At the same time, the embedded ring 3081 is designed to be inclined, and the outer ring is provided with a first spherical sealing surface 3082 and a second spherical sealing surface 3083. The first spherical sealing surface 3082 is located to the left of the second spherical sealing surface 3083, and the spherical cap height of the first spherical sealing surface 3082 is greater than that of the second spherical sealing surface 3083. The first spherical sealing surface 3082 is deformed by being tightly attached to the embedded groove 3085 in the outer threaded joint 1, and the second spherical sealing surface 3083 does not deform and bears a greater contact pressure than the second spherical sealing surface 3083. When the special threaded joint bears excessive load and the first spherical sealing surface 3082 yields and loses sealing ability, the second spherical sealing surface 3083 remains in the elastic deformation range, thereby ensuring that the special threaded joint does not leak. Through the cooperation between the first spherical sealing surface 3082 and the second spherical sealing surface 3083, the sealing ability and reliability of the special threaded joint are greatly enhanced.

[0089] The preferred embodiments of the present patent have been described in detail above, but the present patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the purpose of the present patent.

Claims

1. A detachable and reassemblable airtight premium thread joint, comprising an external thread joint (1), an internal thread joint (2), a secondary sealing structure (3), a connecting mechanism (4) and a primary sealing structure (5), characterized in that: Under the action of the connecting mechanism (4), the auxiliary sealing structure (3) and the main sealing structure (5) realize sealing, the auxiliary sealing structure (3) is located on the left side of the connecting mechanism (4), and the main sealing structure (5) is located on the right side of the connecting mechanism (4); The auxiliary sealing structure (3) comprises a positioning mechanism (308) and a supporting mechanism (309), the positioning mechanism (308) is arranged between the outer threaded joint (1) and the inner threaded joint (2), and the right side of the positioning mechanism (308) is fixed to the left side of the inner threaded joint (2); the positioning mechanism (308) is designed in a circular truncated cone shape and has a larger diameter on the left side than on the right side; and the supporting mechanism (309) is fixed to the right side surface of the outer threaded joint (1); and the positioning mechanism (308) is located on the inner side of the supporting mechanism (309). The supporting mechanism (309) comprises a supporting ring (3091), the left side surface of the supporting ring (3091) is fixed to the right side of the outer threaded joint (1), the supporting ring (3091) is embedded in a rubber ring groove (3093), and the inner and outer circles of the supporting ring (3091) are each provided with five groups of sealing rubber rings (3092), and the five groups of sealing rubber rings (3092) are respectively embedded in a blocking groove (3094), and the five groups of blocking grooves (3094) are respectively arranged on the inner and outer circles of the rubber ring groove (3093). The connecting mechanism (4) adopts a threaded connection form, and the thread is a modified trapezoidal straight thread structure. The modified trapezoidal straight thread structure comprises an outer thread guide surface (402) and an outer thread bearing surface (404), the outer thread guide surface (402) is connected to the tooth top through a secondary transition circular arc I (401), and the radius R3 thereof is 0.45-0.55 mm; The outer thread bearing surface (404) is connected to the tooth top through a secondary transition circular arc II (403), and the radius R1 thereof is 0.10-0.20 mm; The outer thread guide surface (402) and the outer thread bearing surface (404) are transitionally connected to the tooth root through a secondary transition circular arc III (405), and the radius R2 thereof is 0.10-0.20 mm; The outer thread guide surface (402) and the vertical direction form an angle α of 20-25°, the outer thread bearing surface (404) and the vertical direction form an angle β of 1-5°, and the outer thread height h1 is 1.05-1.10 mm; The outer thread guide surface (402) corresponds to the inner thread guide surface (409) and is located on the inner threaded joint (2), the inner thread guide surface (409) is connected to the tooth root through a secondary transition circular arc V (408), and the radius thereof is the same as R3; The inner thread bearing surface (406) is connected to the tooth root through a secondary transition circular arc IV (407), and the radius thereof is the same as R1; The inner thread guide surface (409) and the inner thread bearing surface (406) are transitionally connected to the tooth top through a secondary transition circular arc VI (410), and the radius thereof is the same as R2; The inner thread guide surface (409) and the vertical direction form an angle equal to α, the inner thread bearing surface (406) and the vertical direction form an angle equal to β, and the inner thread height h2 is 1.05-1.10 mm and is equal to h1.

2. A special threaded connection with a removable seal according to claim 1, characterized in that: The main sealing structure (5) is composed of the internal thread main sealing surface (505) located inside the left side of the internal thread joint (2) and the outer sealing cone surface of the right end of the external thread joint (1); The internal thread main sealing surface (505) is conical, the axial line of which is collinear with the axial line of the internal thread joint (2), and the included angle θ5 between the horizontal direction and the axial line is 14°, and the horizontal direction length L4 is 11.00 mm; The outer sealing cone surface of the right end of the external thread joint (1) is composed of three sections, which are the main sealing first cone surface (501) located on the left side, the main sealing second cone surface (502) located in the middle and the main sealing third cone surface (503) located on the right side, the axial lines of the three sections are collinear, and the axial lines of the three sections are collinear with the axial line of the external thread joint (1); Wherein, the horizontal direction length of the main sealing first cone surface (501) is 2.50 mm, the horizontal direction length of the main sealing second cone surface (502) is 2.00 mm, the horizontal direction length of the main sealing third cone surface (503) is 3.50 mm, the included angle between the main sealing first cone surface (501) and the horizontal direction is θ1, the included angle between the main sealing second cone surface (502) and the horizontal direction is θ2, the included angle between the main sealing third cone surface (503) and the horizontal direction is θ3, θ1=8°, θ2=14° and θ3=15° are taken; A gap L5 of 2-3 mm is required between the right side inner end surface of the internal thread main sealing surface (505) and the right side end surface of the outer sealing cone surface, and a chamfer (504) is arranged between the main sealing third cone surface (503) and the right side end surface thereof.

3. A special threaded connection with a removable gas seal according to claim 2, characterized in that: A cylindrical elastic groove (507) is arranged on the right end inside of the external thread joint (1), the horizontal direction length L7 of the elastic groove (507) is 17.00-18.00 mm, and the thickness L6 is 4.50-4.60 mm; The internal thread joint (2) is hollow, the left side inner cavity diameter of the internal thread joint (2) is L8, and the diameter of the right side elastic groove (507) is L9, and the value satisfies L8L9-1.00 mm; A grease storage cavity I (506) is arranged between the main sealing mechanism and the connecting mechanism (4), and the grease storage cavity I (506) is used for storing excess thread sealing grease; The right side surface of the external thread joint (1) is fixed with the left side surface of the cone surface embedding ring (508), the cone surface embedding ring (508) is embedded into the cone surface embedding groove (509), and the cone surface embedding groove (509) is arranged on the right side of the inner wall of the internal thread joint (2).

4. A special threaded connection with a removable seal according to claim 1, characterized in that: The auxiliary sealing structure (3) is composed of an auxiliary sealing surface I (301), an auxiliary sealing surface II (306), an auxiliary transition arc I (302), an auxiliary transition arc II (307), a positioning mechanism (308) and a supporting mechanism (309); The auxiliary transition arc I (302) and the auxiliary sealing surface I (301) are tangent, the auxiliary transition arc II (307) and the auxiliary sealing surface II (306) are tangent, the auxiliary sealing surface I (301) is inverted inner conical, the included angle θ4 between the auxiliary sealing surface I (301) and the horizontal direction is 45° or 30°, the auxiliary sealing surface II (306) is outer conical, the included angle θ4 between the auxiliary sealing surface II (306) and the horizontal direction is 45° or 30°, and the horizontal inclination angle of the auxiliary sealing surface I (301) is equal to that of the auxiliary sealing surface II (306). The inner side of the auxiliary sealing structure (3) is provided with a grease storage cavity II (303) for storing excess thread sealing grease.

5. A special threaded joint with a removable gasket according to claim 4, characterized in that: The positioning mechanism (308) comprises an embedded ring (3081), the right side surface of the embedded ring (3081) is fixed with the left side surface of the internal thread structure, the embedded ring (3081) is designed to be inclined, and the included angle with the horizontal direction is 20-30°, the embedded ring (3081) is embedded in an embedded groove (3085), the embedded groove (3085) is arranged on the inner side of the external thread joint (1), a rubber pad (3084) is arranged on the inner bottom of the embedded groove (3085), the rubber pad (3084) is overlapped with the left side of the embedded ring (3081), and a gasket is arranged on the outer circle of the inner wall of the embedded groove (3085). The outer wall of the embedded ring (3081) is provided with a first spherical sealing surface (3082) and a second spherical sealing surface (3083), the first spherical sealing surface (3082) is located on the left side of the second spherical sealing surface (3083), and the spherical cap height of the first spherical sealing surface (3082) is greater than that of the second spherical sealing surface (3083).

6. A special threaded connection with a removable seal according to claim 1, characterized in that: The axial interference amount of the sealing surface of the main sealing structure (5) is 0.40-0.50 mm, and the positioning shoulder I (304) and the positioning shoulder II (305) constitute an extrusion sealing surface.

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