Procedures on Fracture Toughness Estimation Safety Assessment and Life Extension for In-Service High Pressure Vessels

Abstract

Based on the typical in-service high pressure vessels made of PCrNi3MoVA for producing synthetic crystal, a systematic technology of material fracture toughness estimation, structural integrity assessment, and life extension is carried out for the in-service equipment with the following aspects: macroscopically and microscopically analyzing, the tests including KIC, AKV, FATT (50%), the predicting method of fracture, system safety assessment, and the life extension technology. Some practical conclusions can be obtained from the test and analysis as follows: The main failure factors for this kind of high pressure vessels include heat treatment processes, temper brittleness, and stress corrosion; It is found that the value of FATT (50%) increased very significantly; The comparison between the test results and the predicted results of the value of KIC is also performed, and it is shown that the value of KIC of in-service equipment can be estimated by the formula presented by Barsom-Rolfe or in API 579 with the value of AKV, The test temperature is recommended at least to reach 25 C (or room temperature) for the repaired vessels; The life extension technologies are put forward for this kind of in-service super-high pressure vessels.