Failures due to ingested bodies in hydraulic turbines

The ingestion of large bodies in turbines can produce blockage in the runner that generates large, unbalanced forces. Blockage in the distributor can change the amplitude and uniformity of the pressure pulsations. Mechanical damage may also be generated.In all cases, the efficiency of the turbine is reduced and the forces on the runner and the vibration levels in the machine are greatly amplified, which reduces the expected life of bearings and seals and even produces considerable damage.In this paper, we present an overview of the damage caused by the ingestion of external bodies in hydraulic turbines. We describe some examples found during 20 years of monitoring. These types of failure have never been studied (except the typical sand erosion), as the grille of the trash rack should prevent the entrance of large bodies to the turbine. However, the trash rack is often partially broken and bodies may detach from the pipe lining.Some cases of damage due to the ingestion of small bodies and particles are also discussed.