Failure analysis in a steam turbine stop valve of a thermal power plant

Abstract

In the current study, the problem of cracking on the stop valve body in a steam turbine related to a thermal power plant is assessed. The problem usually occurs consecutively and almost in identical locations for the power plant's stop valves. To do so, the steam flow path from the developed area at the boiler output to the turbine input is divided into three separate computational domains and numerically simulated. The obtained results of the simulation have been successfully verified using the actual data of the thermal power plant. The common factors affecting the formation of crack consist of contacting shell with cooled steam, expansion and contraction movement of a turbine, insufficient insulation, stop valve spring force, internal pressure, and fluid flow momentum are assessed. The von Mises stresses caused by each factor have been determined. It has been attempted to identify the main cause of cracking by comparing the obtained stress concentration points with the real coordinates of the crack. The results of the simulation revealed that the expansion and contraction movements of the turbine were the main cause of fatigue and crack in the stop valve body. Given the key role of the stop valve in generating power of turbines, the findings of this simulation can help to design sensitive equipment more accurately.