1 Introduction
OCTG casing is an essential product for petroleum production. It connects two casing pipes with threaded couplings to form a casing string of several thousand meters. For casing couplings, thread processing is one of the key points. Therefore, the quality of the coupling is related to whether the entire casing is safe and reliable. Therefore, proper control of deformation and roundness during the processing of oil and casing couplings can make threads more reliable and fundamentally solve thread quality problems.
2 Overview and questions
Currently, there are still some problems in the processing of steel casing couplings. If these problems cannot be solved well, they will affect the safety of casing use. Therefore, it is necessary to carry out specific research and analysis on it and find the key core issues, so that we can find the best solution to the problem.
2.1 Overview
Due to its unique sealing structure and thread profile design, special threads can well ensure the connection strength and sealing performance of the pipe string. In recent years, special threaded oil casing products have been widely used in major oil fields and have achieved good results.
Special threads are different from API threads. While ensuring high connection strength and sealing performance, special threads also impose high precision requirements on thread parameters, especially thread roundness. The roundness requirement for general API threads is 0.2mm, while the roundness requirement for special threads is 0.1mm. Recently, imported precision lathes can meet the processing requirements for special thread tooth height, pitch, taper and some conventional sizes. Since steel casing pipe is a typical thin-walled workpiece, elastic-plastic deformation occurs easily in the processing of internal threads and sealing surfaces, causing elliptical problems. If the control is improper, it is easy to have out-of-roundness problems, making it difficult to achieve its unique connection performance and sealing performance, so that it cannot meet the use requirements, resulting in a decrease in the product qualification rate of special threaded couplings, a decrease in processing efficiency, and an increase in costs, which has become a problem for many Coupling manufacturers have technical difficulties in processing special threaded couplings.
2.2 Questions
When processing couplings, it is easy to cause ellipse problems due to deformation. If the control and operation are improper, serious roundness out-of-tolerance problems will also occur. In this case, it will not be able to meet normal construction needs and subsequent use requirements, which will have an adverse impact on production. Therefore, it is necessary to strengthen research and analysis in this area and find the best solutions. Roundness error problem is one of the common problems in the petroleum industry. From the analysis of its parts, we can know that its structure is very complex. The requirements for surface and size are very high. Especially in terms of thread pitch diameter and sealing, strict control is required. If the vibration occurs too fast during processing, resulting in tool marks, it can also have a great impact on it. During processing, it is best to use imported precision CNC lathes to process this special thread.
In the actual operation process, the processing technology mainly includes the following aspects:
The first aspect is rough turning of the end face, the second aspect is rough turning of the inner hole, the third aspect is fine turning of the end face and the inner hole, and the fourth aspect is fine turning of the thread and the fine turning of the sealing surface. The coupling is best clamped using a three-point flat jaw method. Under the action of cutting force, it is necessary to ensure that the working components do not change and ensure that the clamping force remains below 0.4 PSI. After the fine threading and sealing work is completed, attention should be paid to the testing work. Moreover, the goals must be clear when testing. Roundness needs to be kept within 0.02 mm. If the claw is released, an out-of-tolerance situation may occur. It is necessary to analyze and study these situations and analyze the roundness out-of-tolerance situation. You can extract a full specification coupling to process the internal thread, and use manual measurement to measure and detect the inner diameter and size of the coupling seal. Of course, the measuring tool should be a relatively high-precision or professional thread diameter gauge, so that the test results will be more accurate and reliable. Through the above methods, the relevant data of the internal thread can be measured and the problem can be found.
3 reasons and solutions
The production and use of steel casing is an important link in the production of petroleum resources. Therefore, it is necessary to control the processing conditions of oil and casing couplings, study the causes of problems and find the best solution to solve them. The purpose of this is to prevent major safety hazards in oil and casing pipes, which will affect overall production.
3.1 Reasons
During the processing process, octg casing pipe is very prone to deformation problems, especially when processing internal threads and sealing surfaces, the probability of deformation is very high. If not properly controlled, it can have a huge impact on the entire casing construction. This is why we need to pay attention to roundness control. Couplings are classic thin-walled components that react very strongly to clamping force. When processing coupling threads, it is easy to cause the inner wall roundness to be out of tolerance due to excessive clamping force. For example, the coupling blank has an ideal roundness in its natural state. However, when the claw clamps the coupling, under the influence and action of the clamping force, the coupling blank will experience uneven elastic deformation. Therefore, before thread turning, the inner hole should be turned into a perfect round hole first, so as to solve the effect of deformation caused by the holding force. When the clamping claw is released after the coupling is processed, the clamping force disappears and the coupling will return to its original elasticity. In this way, the inner hole will undergo a second change, and it may become a regular triangular prism. With this change, the inner wall of the coupling will cause a larger roundness error problem.
3.2 Solutions
In fact, the factor that has a significant impact on thread roundness is the elastic deformation of clamping. Therefore, as long as this problem is controlled well, the thread ovality situation can be solved well. To reduce the clamping elasticity of the coupling, when the force is maintained within a certain range, the contact area between the coupling and the claw can be appropriately increased. In this way, deformation problems can be reduced very effectively. In this process, you can also properly use fan-shaped arc contact soft claws to operate, and the effect will be more ideal. The clamping pressure must be ensured to increase the concentrated stress on the coupling. Only in this way will deformation problems not easily occur.
Finally, it can also be ensured that the internal roundness of the coupling does not exceed tolerances. At the same time, in order to ensure the maximum effect, you can adopt a test method to experiment first. To ensure the fan-shaped clamping function, four groups of blanks from the same batch can be extracted and tested using the same clamping strength. During the experiment, relevant parameters should be recorded, such as thread pitch diameter and sealing surface level.
4 Conclusion
Now, oil has become an important resource for social development. It can have a significant impact on my country's energy structure. Therefore, attention should be paid to the processing of steel casing pipe couplings. However, there are still some technical problems encountered during the processing that restrict the development of the petroleum industry, which also deserve everyone's attention and attention. However, as technological strength continues to increase, these problems will gradually be solved.
OCTG casing is an essential product for petroleum production. It connects two casing pipes with threaded couplings to form a casing string of several thousand meters. For casing couplings, thread processing is one of the key points. Therefore, the quality of the coupling is related to whether the entire casing is safe and reliable. Therefore, proper control of deformation and roundness during the processing of oil and casing couplings can make threads more reliable and fundamentally solve thread quality problems.
2 Overview and questions
Currently, there are still some problems in the processing of steel casing couplings. If these problems cannot be solved well, they will affect the safety of casing use. Therefore, it is necessary to carry out specific research and analysis on it and find the key core issues, so that we can find the best solution to the problem.
2.1 Overview
Due to its unique sealing structure and thread profile design, special threads can well ensure the connection strength and sealing performance of the pipe string. In recent years, special threaded oil casing products have been widely used in major oil fields and have achieved good results.
Special threads are different from API threads. While ensuring high connection strength and sealing performance, special threads also impose high precision requirements on thread parameters, especially thread roundness. The roundness requirement for general API threads is 0.2mm, while the roundness requirement for special threads is 0.1mm. Recently, imported precision lathes can meet the processing requirements for special thread tooth height, pitch, taper and some conventional sizes. Since steel casing pipe is a typical thin-walled workpiece, elastic-plastic deformation occurs easily in the processing of internal threads and sealing surfaces, causing elliptical problems. If the control is improper, it is easy to have out-of-roundness problems, making it difficult to achieve its unique connection performance and sealing performance, so that it cannot meet the use requirements, resulting in a decrease in the product qualification rate of special threaded couplings, a decrease in processing efficiency, and an increase in costs, which has become a problem for many Coupling manufacturers have technical difficulties in processing special threaded couplings.
2.2 Questions
When processing couplings, it is easy to cause ellipse problems due to deformation. If the control and operation are improper, serious roundness out-of-tolerance problems will also occur. In this case, it will not be able to meet normal construction needs and subsequent use requirements, which will have an adverse impact on production. Therefore, it is necessary to strengthen research and analysis in this area and find the best solutions. Roundness error problem is one of the common problems in the petroleum industry. From the analysis of its parts, we can know that its structure is very complex. The requirements for surface and size are very high. Especially in terms of thread pitch diameter and sealing, strict control is required. If the vibration occurs too fast during processing, resulting in tool marks, it can also have a great impact on it. During processing, it is best to use imported precision CNC lathes to process this special thread.
In the actual operation process, the processing technology mainly includes the following aspects:
The first aspect is rough turning of the end face, the second aspect is rough turning of the inner hole, the third aspect is fine turning of the end face and the inner hole, and the fourth aspect is fine turning of the thread and the fine turning of the sealing surface. The coupling is best clamped using a three-point flat jaw method. Under the action of cutting force, it is necessary to ensure that the working components do not change and ensure that the clamping force remains below 0.4 PSI. After the fine threading and sealing work is completed, attention should be paid to the testing work. Moreover, the goals must be clear when testing. Roundness needs to be kept within 0.02 mm. If the claw is released, an out-of-tolerance situation may occur. It is necessary to analyze and study these situations and analyze the roundness out-of-tolerance situation. You can extract a full specification coupling to process the internal thread, and use manual measurement to measure and detect the inner diameter and size of the coupling seal. Of course, the measuring tool should be a relatively high-precision or professional thread diameter gauge, so that the test results will be more accurate and reliable. Through the above methods, the relevant data of the internal thread can be measured and the problem can be found.
3 reasons and solutions
The production and use of steel casing is an important link in the production of petroleum resources. Therefore, it is necessary to control the processing conditions of oil and casing couplings, study the causes of problems and find the best solution to solve them. The purpose of this is to prevent major safety hazards in oil and casing pipes, which will affect overall production.
3.1 Reasons
During the processing process, octg casing pipe is very prone to deformation problems, especially when processing internal threads and sealing surfaces, the probability of deformation is very high. If not properly controlled, it can have a huge impact on the entire casing construction. This is why we need to pay attention to roundness control. Couplings are classic thin-walled components that react very strongly to clamping force. When processing coupling threads, it is easy to cause the inner wall roundness to be out of tolerance due to excessive clamping force. For example, the coupling blank has an ideal roundness in its natural state. However, when the claw clamps the coupling, under the influence and action of the clamping force, the coupling blank will experience uneven elastic deformation. Therefore, before thread turning, the inner hole should be turned into a perfect round hole first, so as to solve the effect of deformation caused by the holding force. When the clamping claw is released after the coupling is processed, the clamping force disappears and the coupling will return to its original elasticity. In this way, the inner hole will undergo a second change, and it may become a regular triangular prism. With this change, the inner wall of the coupling will cause a larger roundness error problem.
3.2 Solutions
In fact, the factor that has a significant impact on thread roundness is the elastic deformation of clamping. Therefore, as long as this problem is controlled well, the thread ovality situation can be solved well. To reduce the clamping elasticity of the coupling, when the force is maintained within a certain range, the contact area between the coupling and the claw can be appropriately increased. In this way, deformation problems can be reduced very effectively. In this process, you can also properly use fan-shaped arc contact soft claws to operate, and the effect will be more ideal. The clamping pressure must be ensured to increase the concentrated stress on the coupling. Only in this way will deformation problems not easily occur.
Finally, it can also be ensured that the internal roundness of the coupling does not exceed tolerances. At the same time, in order to ensure the maximum effect, you can adopt a test method to experiment first. To ensure the fan-shaped clamping function, four groups of blanks from the same batch can be extracted and tested using the same clamping strength. During the experiment, relevant parameters should be recorded, such as thread pitch diameter and sealing surface level.
4 Conclusion
Now, oil has become an important resource for social development. It can have a significant impact on my country's energy structure. Therefore, attention should be paid to the processing of steel casing pipe couplings. However, there are still some technical problems encountered during the processing that restrict the development of the petroleum industry, which also deserve everyone's attention and attention. However, as technological strength continues to increase, these problems will gradually be solved.
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