Investigation On Super Pressure Treatment Of Integrated Multi-layer Clamping High Pressure Vessel

Integrated multi-layer clamping structure is common in high pressure vessel. Due to the influence of laminate gaps, in working condition, the stress of inwall increases, while the stress of outerwall decreases. A super pressure treatment (SPT) is needed to be carried after manufacture, which can reduces the laminate gaps by generating certain plastic deformation in the inwall of multi-layer cylinder.A elastic-plastic finite element model of multi-layer vessel with uniform gaps was established, based on ideal plastic material and Mises yield criteria, using ANSYS software. The value of each gap in finite element model was discussed according to the manufacture process. Initial yield pressure of monolayered cylinder with the same size was considered as the SPT pressure, based on the analysis among pressure test, plastic fault theory and self enhancement treatment.Stress distribution in the condition of SPT loading, unloading and design pressure reloading was simulated using elastic-plastic finite element model. Stress test and explosion test of an integrated multi-layer clamping vessel were taken. The results were as followed:1. The building range of laminates after SPT was related to the yield condition in the cylinder's wall. The largest building range would be from the innerwall to the laminate No.i+1 next to the laminate No.i when the elastic-plastic interface radius was in laminate No.i. The smallest building range would be from the innerwall to the elastic-plastic interface2. Increase of the size of gap, ranged≤0.25mm, would decrease the initial yield pressure, so cylinder with larger gap size received better effect under the same SPT pressure. And the integral yield pressure was not affected by the gap's size, so it was safe to use the initial yield pressure of monolayered cylinder with the same size as the SPT pressure.3. According to the stress test and finite element analysis results, the gap size could reference at the range of 0.055~0.13 mm, under present manufacture condition.4. Explosion test verified the reliability of stucture and safty of SPT.