| Popis: |
The main steam isolation valves are safety valves installed in nuclear power plants designed for high energy line break of the steam pipeline, the main steam collector or the steam generator feedwater pipeline. During the regular shutdowns, the radial cracks regularly situated around the circumference in hardfacings of wedges were observed some of which were assessed as non-permissible. The primary objective of the solution is to develop and verify a suitable methodology, based on which it will be possible to decide on the operability of wedges. However, the solution aims at the potential risk prediction of brittle fracture or fatigue cracks growth under the operational loading during the period between regular diagnostics or until the end of the planned service life of the valves. The paper deals with the computational analysis of cracks focused mainly on the abovementioned fracture failures. It is also dedicated to comparing the acquired results from the analyses computed by finite element method (ANSYS) with classical analytical models and experimental testing, respectively. |
