Determination of the dominant failure mechanism of P92 steam piping subjected to daily operational cycle using finite element (FE) technique

Abstract

In a bid to minimise the cost of electrical energy production through the reduction in the quantity of coal usage, the power generation companies resolved to operate different daily cycles characterized by peak and off-peak energy demand periods. These daily operational cycles have left the power plant components operating in a possible creep-fatigue regime. As such, earlier failure of the plant’s components such as the steam pipes due to creep, fatigue, or the combination of both failure modes became inevitable. This study employed finite element (FE) technique to determine the dominant failure mechanism and useful life of P92 power generation steam piping subjected to one of the daily operational cycles. The outcome of the study showed that the failure of the piping when subjected to the daily cycle is creep dominated, and failure due to fatigue or possible creep-fatigue interaction was impossible since the daily cycle was insufficient to induce the extensive plastic strain required for the initiation and propagation of fatigue failure. Hence, the best form of operating steam pipe/piping is steady-state, since subjecting them to daily cycles significantly reduce their useful life.