Discussion on the Strength Calculation Method for Connecting Bolts between Head Cover and Stay Ring of Pumped Storage Power Station in Unit Runaway

Abstract The units of pumped storage power plants are frequently started and operate under complex modes. There have been many fracture accidents of connecting bolts between head cover and stay ring in China and abroad, resulting in flooding of the plants, affecting the safety of personnel and property. The unit runaway mode is one of the controlling modes in the calculation of head cover bolts. Due to the unstable flow in this mode, it is difficult to accurately obtain the head cover load, which affects the accuracy of bolt strength calculation. This article explores the relevant calculation methods through an example of the strength review calculation of the head cover and stay ring connecting bolts of a pumped storage power station. A method was proposed to perform CFD steady state calculations on several characteristic points of the runaway mode using one-dimensional transient calculation dates as boundary conditions, and then correct the result of head cover load calculation. The method in this article takes into account both the calculation time and accuracy, and has certain engineering practicality, which can be used as a reference for the industry.