Sealing connection device for combined load experiment of high-steel-grade special thread oil casing

Abstract

A high-steel-grade special thread oil casing combined load experiment sealing connection device comprises a solid end plug and a gland, and the gland is in threaded connection with the end of the end plug. A blind hole is axially formed in the center of the end plug, a T-shaped internal thread is arranged at the root of the blind hole, and the T-shaped internal thread is connected with the external thread of the sample tube body; the side, facing the gland, of the blind hole extends outwards to form a sealing groove, a plurality of sets of combined sliding ring sealing structures are arranged in the sealing groove, each set of combined sliding ring sealing structure is composed of an O-shaped sealing ring and a J-shaped sliding ring, and the gland makes contact with the combined sliding ring sealing structure on the outermost side. And after the sample tube body is inserted into the combined slip ring sealing structure, the end part of the sample tube body is not contacted with the gland. A connection mode provided by the sealing connection device for the combined load experiment of the high-steel-grade special threaded oil casing can replace a traditional welding mode, and the technical problem that the experiment fails due to the fact that the welding performance of the high-steel-grade special threaded oil casing cannot be guaranteed at present is solved.

Description

Technical Field

[0001] The present invention relates to a connecting device for full-size experimental pipes of oil casings and tubing, and more particularly to a sealed connecting device for composite load experiments of high-grade special-thread oil casings and tubing.

Background Art

[0002] During the development of special threads, it is necessary to test the processed thread profiles under composite loads of tension, compression, bending and high temperature. Currently, domestic and foreign laboratories both use the method of end plug welding to connect steel pipes with equipment. In order to reduce the experimental cost and ensure that the end plugs can be reused repeatedly, the laboratory uses 42CrMo ultra-high strength steel, which has high strength and toughness, good hardenability, and has a relatively high fatigue limit and anti-multiple impact ability after quenching and tempering treatment, and is very suitable for composite load tests and ultimate load tests.

[0003] However, with the continuous improvement of the strength of oil casing steel pipes, high-strength special-thread casing products such as Q125 and V140 have become increasingly mature. Using the welding method for this type of high-strength casing can no longer meet the composite load experiment. Since the Ceq value of 42CrMo steel is as high as 0.893%, its weldability is poor. After welding, heat treatment is required. The ideal heat treatment process is to heat up to 600 - 650°C at a heating rate of 80°C / h, and keep it at the required temperature for 4 hours. Under this process, the weldability of 42CrMo steel can be achieved. However, during heat treatment, since the end plug is welded to the experimental steel pipe, the material properties of the steel pipe will decline and softening will occur under long-term heating, resulting in a significant decrease in the yield strength and tensile strength of the experimental steel pipe. Therefore, in order to truly reflect the material properties of the steel pipe, the heating time should be reduced. However, after reducing the heating time, the welding performance of 42CrMo steel becomes poor, and martensite will be generated in the heat-affected zone of the weld, resulting in cracks during the experiment and thus causing the experiment to fail. At the same time, the highest yield strength of current manual high-strength welding electrodes is 890 Mpa, while the average yield strength of high-strength steel pipes such as Q125 and V140 is higher than 900 Mpa. Therefore, during the ultimate load experiment, it is easy to break and cause the experiment to be unable to proceed.

[0004] In view of this, the present invention provides a sealed connecting device for composite load experiments of high-grade special-thread oil casings and tubing to solve the above problems.

Summary of the Invention

[0005] To solve the above problems, the present invention provides a sealed connecting device for composite load experiments of high-grade special-thread oil casings and tubing. This connection method can replace the traditional welding method and solve the technical problem that the current high-grade special-thread casings fail in experiments due to the inability to guarantee welding performance.

[0006] The present invention is realized through the following technical solutions. A sealing connection device for a composite load experiment of high-grade special threaded oil casing pipes is provided, including: a solid end plug and a gland, and the gland is threadedly connected to the end of the end plug;

[0007] A blind hole is axially opened at the central position of the end plug, and a T-shaped internal thread is provided at the root of the blind hole, and the T-shaped internal thread is connected to the external thread of the sample pipe body;

[0008] One side of the blind hole facing the gland extends outward to form a sealing groove, and several groups of combined slip ring sealing structures are provided in the sealing groove. Each group of combined slip ring sealing structures consists of an O-ring and a J-shaped slip ring, and the gland is in contact with the outermost combined slip ring sealing structure;

[0009] After the sample pipe body is inserted into the combined slip ring sealing structure, there is no contact between its end and the gland.

[0010] Particularly, the tooth profile of the T-shaped internal thread is a coupling partial trapezoidal thread, which includes: tooth top, tooth bottom, guiding surface, load-bearing surface, internal thread tooth height, internal thread tooth groove, internal thread tooth thickness (A2); wherein the tooth top and the tooth bottom are parallel to the central axis of the coupling; the guiding surface is a double-angle combined guiding surface, the first guiding surface angle is 10°-13°, the second guiding surface angle is 30°-40°, and the height of the second guiding surface is 1 / 3-1 / 2 of the internal thread tooth height; the negative angle of the internal thread load-bearing surface is 1°-3°; the internal thread tooth height ranges from 1.0 mm to 1.2 mm; the difference between the internal thread tooth groove and the internal thread tooth thickness is 0.05 mm to 0.15 mm.

[0011] Particularly, the tooth profile of the external thread of the sample pipe body is a partial trapezoid, which includes: tooth top, tooth bottom, guiding surface, load-bearing surface, external thread tooth height, external thread tooth groove, external thread tooth thickness; wherein the tooth top and the tooth bottom are parallel to the central axis of the pipe body; the external thread guiding surface angle is 10°-13°; the negative angle of the external thread load-bearing surface is 1°-3°; the external thread tooth height ranges from 0.9 mm to 1.1 mm; the difference between the external thread tooth groove and the external thread tooth thickness is 0.05 m to 0.15 mm.

[0012] Particularly, both the T-shaped internal thread and the external thread of the sample pipe body are small taper taper threads, with a taper of 1:18 and 5 threads per inch.

[0013] Particularly, there are four groups of the combined slip ring sealing structures.

[0014] Particularly, after the gland and the end plug are threadedly connected, the compression rate of the O-ring reaches 10-15%.

[0015] Particularly, a sealing spacer ring is provided between adjacent two groups of combined slip ring sealing structures, so as to further ensure that the compression rate of the O-ring reaches 10-15%.

[0016] Specifically, since the sample pipe fitting will have radial displacement during the experiment, a gap of 3-5 mm is reserved between the gland and the end of the sample pipe body to ensure that there is no interference between the two.

[0017] Specifically, after the sample pipe body is connected to the end plug through a T-shaped thread, the external leakage size of the sample pipe fitting can be determined by the length of the inner hole of the end plug to ensure a more secure connection between the two. The external leakage size of the external thread of the sample pipe body is ±1.5 mm, and thus the connection firmness between the two can be inspected through the external leakage size.

[0018] The present invention also provides a sealing connection method for a composite load experiment of a high-grade special thread oil casing, comprising the following steps:

[0019] S1 Connect the sample pipe body and the end plug through a T-shaped thread;

[0020] S2 Arrange the combined slip ring sealing structure in the sealing groove according to the connection relationship between the sealing groove at the end plug, the sample pipe body and the gland, and arrange a sealing spacer ring between two adjacent groups of combined slip ring sealing structures;

[0021] S3 Set the gland at the end of the end plug through a thread to achieve the compaction of the O-ring. This connection method can replace the traditional welding method to solve the technical problem that the welding performance of the current high-grade special thread casing cannot be guaranteed, resulting in experimental failure. After the connection is completed, the compression rate of the O-ring reaches 10-15%.

[0022] Compared with the prior art, the present invention provides a sealing connection device for a composite load experiment of a high-grade special thread oil casing, having the following beneficial effects:

[0023] 1. This connection device solves the problem that the welding is prone to breakage during the composite load experiment of the current high-grade special thread oil casing, thus ensuring the smooth progress of the experiment;

[0024] 2. This connection device is simpler to operate than the welding method, has fewer processes, does not require long-term heat preservation and heating, reduces the preparation time of the sample, and improves the experimental efficiency;

[0025] 3. This connection device uses a mechanical connection method to replace the traditional welding method, does not require professional welding personnel, and has low requirements for personnel;

[0026] 4. This connection device also does not require the processing of a metal interference sealing structure on the internal and external threads, reduces the thread processing difficulty, and is convenient for actual operation.

Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a sealing connection device for a composite load experiment of a high-grade special thread oil casing according to the present invention;

[0028] Figure 2 This is the thread profile diagram of the T-shaped internal thread of the present invention;

[0029] Figure 3 This is the thread profile diagram of the T-shaped external thread of the present invention;

[0030] Figure 4 This is the schematic diagram of the combined slip ring seal structure of the present invention.

[0031] In the attached drawings, 1 is the end plug, 2 is the combined slip ring seal structure, 3 is the gland, 4 is the T-shaped internal thread, 5 is the sample tube body, 6 is the O-ring, 7 is the J-shaped slip ring, 8 is the lower support plate, 9 is the blind hole, 10 is the seal groove, 11 is the drain pipe, 12 is the water-cooled tank, H is the internal thread tooth height, A1 is the internal thread tooth groove, A2 is the internal thread tooth thickness, γ1 is the first guide surface angle, γ2 is the second guide surface angle, h is the second guide surface height, θ1 is the negative angle of the internal thread load-bearing surface, H1 is the external thread tooth height, C2 is the external thread tooth groove, C1 is the external thread tooth thickness, γ3 is the external thread guide surface angle, θ2 is the negative angle of the external thread load-bearing surface.

Detailed implementation manner

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with the attached drawings.

[0033] Example 1

[0034] Please refer to Figure 1 , the present invention provides a sealing connection device for a high-grade special threaded oil casing under combined loads, which includes: a solid end plug 1, a combined slip ring seal structure 2, and a gland 3, and the gland 3 is threadedly connected to the end of the end plug 1;

[0035] A blind hole 9 is axially provided at the central position of the end plug 1. A T-shaped internal thread 4 is provided at the root of the blind hole 9, and the blind hole 9 extends outward on the side facing the gland 3 to form a seal groove 10. A plurality of groups of combined slip ring seal structures 2 are provided in the seal groove 10. Each group of combined slip ring seal structures 2 is composed of an O-ring 6 and a J-shaped slip ring 7, and the gland 3 is in contact with the outermost combined slip ring seal structure 2;

[0036] The sample tube body 5 is threadedly connected to the end plug 1 through the T-shaped internal thread 4;

[0037] The combined slip ring seal structure 2 is arranged in the seal groove 10. The sample tube body 5 extends into the combined slip ring seal structure 2, and there is no contact between the end of the sample tube body 5 and the gland 3.

[0038] In the actual installation process, first, the sample tube body 5 is threadedly connected through the T-shaped internal thread 4 and the T-shaped external thread on its outer wall. At this time, the external leakage size of the sample tube body 5 can be determined by the inner hole length of the end plug 1 of the solid body to ensure a more secure threaded connection between the two. After the sample tube body 5 is connected to the end plug 1, the four sets of combined slip ring sealing structures 2 are respectively placed into the environmental control sealing groove 10. Next, the gland 3 is threadedly connected to the end plug 1, and at the same time, the sealing is compacted through the combined slip ring sealing structure 2. This connection method can replace the traditional welding method to solve the technical problem that the welding performance of high-grade special threaded casing cannot be guaranteed at present, resulting in experimental failure. At the same time, this structure also does not require a metal interference sealing structure for internal and external thread processing, reducing the difficulty of thread processing and facilitating actual operation.

[0039] Embodiment 2

[0040] Please refer to Figures 2 - 3 , in the connecting device provided by the present invention, the tooth profile of the T-shaped internal thread 4 is a coupling partial trapezoidal thread, which includes: tooth top, tooth bottom, guiding surface, bearing surface, internal thread tooth height H, internal thread tooth groove A1, internal thread tooth thickness A2; wherein the tooth top and the tooth bottom are parallel to the central axis of the coupling; the guiding surface is a double-angle combined guiding surface, the first guiding surface angle γ1 is 10° - 13°, the second guiding surface angle γ2 is 30° - 40°, and the height h of the second guiding surface is 1 / 3 - 1 / 2 of the internal thread tooth height (H); the negative angle θ1 of the internal thread bearing surface is 1° - 3°; the range of the internal thread tooth height H is 1.0 mm - 1.2 mm; the difference between the internal thread tooth groove A1 and the internal thread tooth thickness A2 is 0.05 mm - 0.15 mm.

[0041] The external thread tooth profile of the sample tube body 5 is a partial trapezoid, which includes: tooth top, tooth bottom, guiding surface, bearing surface, external thread tooth height H1, external thread tooth groove C2, external thread tooth thickness C1; wherein the tooth top and the tooth bottom are parallel to the central axis of the tube body; the external thread guiding surface angle γ3 is 10° - 13°; the negative angle θ2 of the external thread bearing surface is 1° - 3°; the range of the external thread tooth height H1 is 0.9 mm - 1.1 mm; the difference between the external thread tooth groove C2 and the external thread tooth thickness C1 is 0.05 m - 0.15 mm.

[0042] Specifically, both the T-shaped internal thread 4 and the external thread of the sample tube body 5 are small taper cone threads, with a taper of 1:18 and 5 threads per inch.

[0043] In the structure provided by this Embodiment 2, the T-shaped thread guiding surface is a double-angle combined guiding surface, which has an automatic alignment function during threading, is easy to thread on-site, the internal thread uses a combined guiding surface that matches the external thread guiding surface, which is beneficial to increasing the internal clearance of the thread, and at the same time has an easy lead-in thread and is relatively convenient for on-site operation; at the same time, the internal thread bearing surface uses a negative angle, greatly enhancing the connection strength of the thread.

[0044] Example 3

[0045] That reference Figure 4 In the connecting device provided by the present invention, the gland 3 is connected to the end plug 1 by threads. During actual use, the operator only needs to install the gland 3 in place, and the effective length of the threads can be determined according to the material of the O-ring 6 to ensure that the compression rate of each combined slip ring seal structure 2 after installation reaches 10%-15%. At the same time, since the steel pipe will generate radial displacement during the experiment, the inner diameter of the gland 3 should maintain a gap of 3-5 mm from the experimental steel pipe.

[0046] Example 4

[0047] In the connecting device provided by the present invention, a sealing spacer ring 8 is provided between two adjacent combined slip ring seal structures 2 to further ensure that the compression rate of each combined slip ring seal structure 2 after installation reaches 10%-15%, thereby making the sealing performance better.

[0048] In summary, the high-grade steel special thread oil casing composite load experiment sealing connection device provided by the present invention is composed of a solid end plug, a combined seal ring, a sealing spacer ring, and a gland. This connection method can replace the traditional welding method to solve the technical problem that the welding performance of the current high-grade steel special thread casing cannot be guaranteed, resulting in experimental failure. At the same time, this structure also does not require an internal and external thread processing metal interference seal structure, reducing the thread processing difficulty and facilitating actual operation.

Claims

1. A sealing connection device for the combined load experiment of high-grade special threaded oil casing pipes, characterized in that Comprising: A end plug (1) and a gland (3) of a solid body, the gland (3) being threadedly connected to the end of the end plug (1); A blind hole (9) is axially provided at the central position of the end plug (1), and a T-shaped internal thread (4) is provided at the root of the blind hole (9), and the T-shaped internal thread (4) is threadedly connected to the external thread of the sample tube body (5); One side of the blind hole (9) facing the gland (3) extends outward to form a sealing groove (10), and a plurality of sets of combined slip ring sealing structures (2) are provided in the sealing groove (10). Each set of combined slip ring sealing structures (2) is composed of an O-ring (6) and a J-shaped slip ring (7), and the gland (3) is in contact with the outermost combined slip ring sealing structure (2); After the sample tube body (5) is inserted into the combined slip ring sealing structure (2), there is no contact between its end and the gland (3).

2. The composite load experimental sealing connection device for high-grade special threaded oil casing according to claim 1, wherein, The tooth profile of the T-shaped internal thread (4) is a coupling partial trapezoidal thread, which includes: tooth top, tooth bottom, guiding surface, bearing surface, internal thread tooth height (H), internal thread tooth groove (A1), internal thread tooth thickness (A2); wherein the tooth top and the tooth bottom are parallel to the central axis of the coupling; the guiding surface is a double-angle combined guiding surface, the first guiding surface angle (γ1) is 10° - 13°, the second guiding surface angle (γ2) is 30° - 40°, and the height (h) of the second guiding surface is 1 / 3 - 1 / 2 of the internal thread tooth height (H); the internal thread bearing surface negative angle (θ1) is 1° - 3°; the internal thread tooth height (H) ranges from 1.0 mm to 1.2 mm; the difference between the internal thread tooth groove (A1) and the internal thread tooth thickness (A2) is 0.05 mm - 0.15 mm.

3. A sealing connection device for a composite load experiment of a high-grade special threaded oil casing according to claim 1, characterized in that, The external thread tooth profile of the sample tube body (5) is a partial trapezoid, which includes: tooth top, tooth bottom, guiding surface, bearing surface, external thread tooth height (H1), external thread tooth groove (C2), external thread tooth thickness (C1); wherein the tooth top and the tooth bottom are parallel to the central axis of the tube body; the external thread guiding surface angle (γ3) is 10° - 13°; the external thread bearing surface negative angle (θ2) is 1° - 3°; the external thread tooth height (H1) ranges from 0.9 mm to 1.1 mm; the difference between the external thread tooth groove (C2) and the external thread tooth thickness (C1) is 0.05 m - 0.15 mm.

4. A composite load test sealing connection device for high-grade special threaded oil casing according to claim 1, characterized in that, Both the T-shaped internal thread (4) and the external thread of the sample tube body (5) are small taper taper threads, with a taper of 1:18 and 5 threads per inch.

5. The composite load experimental sealing connection device for high-grade special threaded oil casing according to claim 1, characterized in that, There are four sets of the combined slip ring sealing structures (2).

6. The composite load test sealing connection device for high-grade special threaded oil casing according to claim 1, characterized in that, After the threaded connection between the gland (3) and the end plug (1) is completed, the compression ratio of the O-ring (6) reaches 10 - 15%.

7. A sealing connection device for a composite load experiment of a high-grade special threaded oil casing according to claim 6, characterized in that, A sealing spacer ring (8) is provided between adjacent two sets of combined slip ring sealing structures (2).

8. A composite load test sealing connection device for high-grade special threaded oil casing according to claim 1, characterized in that, The distance between the gland (3) and the end of the sample tube body (5) is 3 - 5 mm.

9. A composite load test sealing connection device for high-grade special threaded oil casing according to claim 1, characterized in that, After the sample tube body (5) is threadedly connected to the end plug (1), the external leakage dimension of the external thread of the sample tube body (5) is ±1.5 mm.

10. A method for sealing connection in a combined load experiment of high-grade special threaded oil casing pipes, characterized in that, Including the following steps: S1 Threadedly connect the sample tube body and the end plug through the T-shaped thread; S2 According to the connection relationship between the sealing groove at the end plug, the sample tube body and the gland, arrange the combined slip ring sealing structures in the sealing groove, and set a sealing spacer ring between adjacent two sets of combined slip ring sealing structures; S3 sets the gland on the end of the end plug through threads to achieve the compaction of the O-ring seal. After the connection is completed, the compression ratio of the O-ring seal reaches 10-15%.

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