As a key connecting component of the pipeline system, the annular disc structure of pipe flange realizes sealing surface compression through bolt preload. Effective maintenance strategies need to be formulated based on material properties and service environment, and the core is to control the risk of seal failure and structural damage.
The sealing surface of pipe flange needs to maintain a specific surface finish, and the indentation and dirt should be removed periodically to prevent gasket collapse. The axial stress of the bolts should implement a graded tightening strategy, and the diagonal tightening sequence should be followed to offset the eccentric load. The stress relaxation of the bolts needs to be monitored under high temperature conditions, and the re-tightening operation after thermal cycling should compensate for creep deformation. For flanges in corrosive environments, apply corrosion inhibitor paste to the bolt threads to block the electrochemical pathway.
The pipeline support system should be calibrated regularly to avoid external loads from being transmitted to the flange neck. Damping bushings are added to the flanges near the vibration source to reduce the risk of fatigue cracks caused by alternating stress. In low temperature environments, pay attention to the tendency of material embrittlement, and control the temperature change rate of the medium during the shutdown and start-up phase. Key inspections are carried out in the root area of the sealing groove, where stress concentration is prone to induce cracks.
For pipe flange sealing surface, if the depth of through-scratches reaches the critical value, machining is required to repair the flatness. If stress corrosion cracks appear on the flange neck or the wall thickness is reduced beyond the limit, it is recommended to replace the whole flange. After the high-pressure working flange has undergone a specific period of thermal cycling, it should be retired even if the non-destructive testing is qualified.
