LIFETIME ASSESSMENT OF HYDROPOWER UNITS

Report, 2025

Lifetime evaluation is an essential analysis to secure high availability
and reliability of any machine, to reach its expected service life
associated with a particular damage mechanism. Hydropower units are
normally unique machines of different size, geometry and mechanical
properties, which makes it even more difficult and challenging to define
general turbine loads and how these loads are distributed through the
machine.

One example is the blade setting mechanism for Kaplan machines where the load
distribution between individual links, lever arms and bearings etc. are
unknown. The load distribution may depend on variations in external and internal
loads, bearing friction, manufacturing tolerances and how the runner is
assembled. In addition, the rotors are normally vertical and hence the bearing
models becomes nonlinear.

In this report, the senior researchers of the SVC work package “Hydropower
Technology” have summarized the state of the art together with own experience
from SVC research projects. The report is limited to the hydropower unit and the
research areas fluid dynamics, rotordynamics, solid mechanics and machine
elements. Possible damage mechanisms and loads are listed together with different
instabilities that may be applicable to hydropower units. To make the research
efficient and to prioritize and direct its resources where it creates most value, it is
important to define which are the critical components depending on damage
mechanism.

One main result and conclusion is that measurement technology needs to be
evaluated and developed, to get the forces that excite the unit during different
operating conditions as well as developing condition monitoring systems and tools
for diagnose and prognosis. Knowledge of the forces on the system, operation
pattern and damage mechanism is essential to be able to determine the expected
life of different components. The report also suggests needed research to get closer
to a methodology for lifetime assessment of hydropower units. One problem is that
lifetime assessment needs a holistic approach while research is on a detailed level.
Therefore, if lifetime assessment becomes a prioritized area there is a need of a
project leader that guides and concludes research results towards a common goal.

The highlighted text discusses the importance of lifetime evaluation for ensuring the
high availability and reliability of hydropower units. It highlights the unique
challenges posed by the different sizes, geometries, and mechanical properties of these
units. The text also underscores the need for advanced measurement technology and
condition monitoring systems to understand the loads and damage mechanisms
affecting these systems. Furthermore, it suggests that future research should aim to
develop a comprehensive methodology for lifetime assessment and emphasizes the
necessity of having a project leader to guide and unify the research efforts towards a
common goal.