Research on stress analysis and support plant optimization of natural gas pipeline with ball valve structure in compressor station

The ball valves in natural-gas pipelines at compressor stations have a relatively large self-weight, which can lead to pipeline stress, deformation, and subsidence at the buried ends. Here, the natural-gas pipeline with ball valves at a compressor station in the northwest collapsible loess area was studied. A full-scale finite element model is established. First, the stress and deformation of the pipeline without support plant were analyzed, and the reasons for the subsidence of the buried ends were explored. The results showed that due to the large self-weight of the two ball valves in the middle of the pipeline, a large bending moment was generated at the buried ends of the pipeline under the action of gravity, resulting in significant stress and deformation in the elbow areas, especially on the side closer to the heavier ball valve, which made the pipeline prone to subsidence at the buried ends. Second, the influence of the location and number of support plants as well as the settlement conditions on the stress and deformation of the pipeline was discussed. It was found that the optimal location for building support plants is at the bottom of the ball valves. When the number of support plants is the same as that of the ball valves and they are all placed at the bottom of the ball valves, the control effect on stress and deformation is the best one. However, considering the construction cost of the support plants, it is sufficient to build a support only at the end of the ball valve with the largest mass. Based on these findings, an optimized support plants layout plan is proposed and applied to the engineering site. To verify the effectiveness of the proposed plan, X-ray stress testing was used. The error of the stress test values and the finite-element analysis results is within 20%. The stress linearization calibration was carried out in accordance with the JB 4732-1995(R2005) “Steel Pressure Vessels-Analytical Design Criteria”, and the results showed that the on-site process optimization scheme can pass the verification. This research provides an in-depth analysis of the stress and deformation problems of natural-gas pipelines with ball valves, and the proposed optimization scheme offers an effective reference for improving the stress distribution of pipelines and ensuring the safe operation of natural-gas pipelines. It was believed this study can contribute to the development of the natural-gas pipeline engineering field and provide valuable guidance for future engineering practices and further research in this area.