Progress of Cryogenics and Isotopes Separation

A FINITE-ELEMENT BASED INVESTIGATION FOR TURBINE BY-PASS LINE SNUBBER FAILURE 

Radu M. Bilegan, Stefan Nicolici, Alexandru Gheorghita*

Subsidiary of Technology and Engineering for Nuclear Projects (CITON), 409, Atomistilor Street, Magurele, Judet Ilfov, Romania

ABSTRACT

The studies presented in this paper were prepared based on Cernavoda NPP engineering division request, having the objective to identify the causes that led to the appearance of cracks at the supports level for the turbine bypass piping system. The applied procedure in our work for root cause analysis consisted in stress evaluation at the cracked areas level for different types of loadings arising in normal operation of the turbine bypass line. Subsequently, the classification of the loads by the stresses produced has allowed identifying a common cause of the encountered problems.

The analyses performed in this paper aimed to evaluate the stresses in the clamping systems of the snubber support type found defective subjected to two types of loading, namely: external static and thermal transitory loads. The calculations were performed using the finite element models developed in Ansys Mechanical. It was concluded that the major contributor to the cracks initiation and propagation is the thermal shock producing differential thermal dilatations in the clamping devices of the supports.

Keywords: Supports failure, Root-cause analysis, FEA, Ansys