Thermo-Mechanical Analysis and Structural Improvements for Mitigating Branch Displacement and Pipe Failure in a Gas Processing Unity Ground Flare

Abstract During the inspection at the maintenance shutdown of a Gas Processing Unity ground flare, a large displacement was observed in one of the branches of the sixth stage, leading to catastrophic failure of its main pipe in two points. The main hypotheses for the cause of this displacement and failures are the presence of a circumferential thermal gradient combined with the support being locked at the end of the main pipe and the lack of guides along the straight section. To assess the effects and validate the hypothesis, a comprehensive thermo-mechanical analysis was conducted using numerical simulation. The simulation model was developed based on the observed behavior in the field and aimed to reproduce the interactions between thermal and mechanical factors to identify its contribution to the failure. The results of the simulation confirmed the initial hypothesis, indicating that the presence of a circumferential thermal gradient, combined with the locked support and lack of guides, led to the significant displacement and subsequent failures in the sixth stage branch. This finding highlights the importance of considering both thermal and mechanical factors in the design of ground flares. Based on the validated simulation model, several structural improvements were proposed to improve the integrity and reliability of the ground flare system. These improvements include the inclusion of additional guides along the sixth stage section to prevent excessive displacement, as well as a redesign of the support mechanism to ensure proper movement and prevent locking. Furthermore, the thermal simulation results indicated that the implementation of thermal insulation above the heat shield could effectively reduce temperature levels and mitigate the circumferential thermal gradient. This additional insulation layer proved to be instrumental in attenuating the stresses that led to branch failure, enhancing the overall safety and performance of the ground flare system. In addition to the failure in the main pipeline, excessive displacement was also detected in small-bore lines that accompany the main line. To address this issue, new measures were proposed to protect these lines from incident radiation, based on the results from the numerical simulation. By relocation of small-bore lines, we expect to minimize the impact of thermal gradients and ensure the integrity of the entire system. By implementing the recommended structural improvements and protective measures, the integrity of the ground flare system can be significantly enhanced. This is crucial as the ground flare serves as a safety system for the operation of the plant. The proposed enhancements will help prevent failures during operation, ensuring the safe and efficient functioning of the facility. The findings of this study contribute to the understanding of thermal and mechanical interactions in ground flare systems and provide valuable insights for the design and maintenance of similar systems in the future.