# Application of Digital Twin in the Industry of Axial Hollow-Wall Pipes
## 4 Testing and Maintenance of Axial Hollow Pipe Products
### Analyze Defects and Optimize the Design
However, on the offset angle outside, the pressure between the straight pipe and the sealing ring decreases as the offset angle increases, leading to a reduction in the sealing performance offered by the sealing ring. To improve the offset angle sealing performance of the pipeline, one approach is to increase the thickness of the raised section of the sealing ring. By doing so, the sealing performance can be enhanced. However, there is a limit to how much the thickness of the sealing ring can be increased. Excessively thick sealing rings may pose difficulties during pipe connection. In the offset angle test, increasing the thickness of the raised section of the sealing ring from 13 mm to 16 mm, while maintaining the same material, resulted in only a modest increase in maximum pressure to 0.289 MPa during the socket joint connection. However, the pipe joint sealing integrity remained intact under the observed 12\({}^{\circ}\) offset angle in the test. Figure 18: Simulated cloud map of pipe joint: (**a**) Stress during straight pipe insertion, (**b**) An 8\({}^{\circ}\) deviation angle, (**c**) A 12\({}^{\circ}\) deviation angle, (**d**) Stress diagram of the outer side, (**e**) PEEQ diagram of the socket end, (**f**) Stress diagram of the outer side. In contrast to normal interface static hydraulic tests, where sealing integrity relies on the sealing ring's performance, the leak tightness test under internal pressure and angular deviation emphasizes the structural mechanical strength of the socket end of the pipe to ensure leak resistance under offset angle pressure. The structural mechanical performance of the socket end determines the strain magnitude caused by the offset angle displacement, which, in turn, affects the pressure experienced by the sealing ring. Appropriate processing temperature plays a vital role in preventing excessive stretching during end-forming. It ensures the wall thickness and material compactness of the expanded section, which ultimately impacts the pipeline's resistance to risks. The fit of the socket joint should also be considered. In the offset angle test, noticeable curling and flanging occurred at the chamfered end of the straight pipe (Figure 18c5). This was attributed to extrusion between the chamfered end of the straight pipe and the diameter changed area of the inner wall at the end of the socket. The wall thickness of the hollow pipe was smaller than that of the solid wall pipe, leading to reduced stiffness at the chamfered end of the straight pipe, due to the decreased wall thickness. Therefore, control of the length at the chamfered end of the straight pipe also affects the pipeline's performance during engineering use. To address this issue, without altering the chamfer slope, the chamfer length could be modified from the original design of 30 mm to 20 mm. This increased the wall thickness at the end of the straight pipe and created an additional 10 mm of reserved space between the pipe end and the diameter changed area of the inner wall at the end of the socket. This modification effectively resolved the problem of curling and flanging at the pipe end. After providing the optimized design to the production side and testing the newly designed and produced products, the results met expectations. After that, further optimization and verification of product operation and maintenance are conducted through actual use and long-term monitoring. Specifically, the optimized product is deployed in practical operation, where the utilization of various data collection devices enables the monitoring of operational data. During the actual operation and maintenance phases, if any issues arise, the corresponding digital twin model is modified, based on the collected data. The optimized model is then reintegrated into the production process, establishing a closed-loop cycle of continuous improvement. This intelligent closed-loop system ensures the long-term operation of the pipeline by incorporating real-time data monitoring and feedback.