Open Access Journal Journal of Power Technologies 97 (5) (2017) 366–372 Analysis of erosion hazards in turbines due to power units operating in low load conditions Andrzej Rusin ∗ , Henryk Lukowicz, Michal Bieniek Institute of Power Engineering and Turbomachinery, Silesian University of Technology, Konarskiego 18, 44-100 Gliwice, Poland Abstract Coal fired power units are having to operate with higher operational flexibility due to changes in the structure of energy systems brought about by the increased production of electric energy from renewable sources. The flexibility at issue relates to frequent changes of generated power and long-running operation at minimum load. By operating in this mode coal fired power units compensate for the stochastic character of energy generated from renewable sources and ensure a desirable reliability level for energy systems, but at the same time it has various impacts on the durability and failure frequency of their component parts. One of the problems which can arise during the operation of turbines working at low loads is increased erosion of the last stage blades of the LP part. This paper presents an analysis of turbine operation conditions which may lead to increased erosion hazards for the blades of the LP part. We address the problem of temperature drop of the re-superheated steam during low load operation of the unit and investigate the impact of erosion losses on the change of dynamic state of the turbine’s last stage blades. Keywords: Erosion hazards; turbine blades erosion; erosion; low load conditions 1. Introduction The development of renewable energy sources is becom- ing a key factor triggering changes in the energy systems of many countries. The impact of increased energy produc- tion from renewable sources is particularly visible in systems dominated by coal fired power plants [1], which are typically designed to operate in a continuous mode. Now, they are having to operate more flexibly [2]. Flexibility refers to among others such factors as: wide range changes of generated power, capability to quickly change loads, ability to oper- ate long term at maximum or minimum power output, abil- ity to execute frequent shutdowns and restarts of the power unit, and fast change of load, shutdowns and restarts. Flex- ible operation of coal fired units can ensure stable and reli- able production of the required amount of energy, but on the other hand it can cause a number of system operation prob- lems and can influence the durability of major components of the units. Flexible operation also brings about significant changes of heat and affects the strength conditions of boiler and turbine components, which in turn impacts the safety ∗ Corresponding author Email addresses: (Andrzej Rusin), (Henryk Lukowicz), (Michal Bieniek) of their operation. The scheduling of maintenance and re- pair works is also affected. Operational experience to date shows that changes to the operational mode of a power unit generally increases operational risk and operational costs, and can lead to the early replacement of components. The problems of increased operational cyclicality of coal fired units have been the subject of many works to date. In the paper [3] issues involving damage done to power unit components caused by the cyclicality of thermal and me- chanical stresses were discussed. The impact of thermo- mechanical fatigue of boiler tubes on their residual durability and on the durability of the whole unit was estimated as were the economic and ecological profits obtained due to higher operational flexibility. The change of operational conditions of coal fired power generating units imposed by the devel- opment of renewable energy sources and the liberalization of energy production market was also discussed in [4]. The papers demonstrated that the increased number of restarts and the changes in power output at the units necessitate the introduction of a wider range and higher frequency of repair works. The economic effects of various operational strate- gies of power units and their impact on the durability of boiler components were discussed in [5]. The increased technical risk involving the operation of turbines due to the intensifica- tion of fatigue processes was discussed in [6]. The conclu-