The prediction of the residual life of critical components has important uses. Such estimates are not only needed in the management and decisions making process regarding inspection, maintenance and repair, but above all evaluating rehabilitation, upgrading or replacement capabilities of existing machines. Estimates of residual fatigue life are of importance in assessing the effects of higher permitted loads and the remaining capacity. Methods include computational analyses like FEM, BEM and CFD but also experimental tools like NDT, strain gage and model analysis. Applications have to be optimally adapted to the special situation and parameters of a hydro power plant.
Safety is a most decisive factor not only in nuclear but also in hydro power stations. Among the possible risks of:
- Mechanical failure
- Flood
- Electric failure
- Fire
- Pollution
the mechanical failure due to cracking of fracture of critical components can represent grave danger of the personnel and also cause damage in view of the availability of a machine.
Therefore, engineering efforts with regard to safety have to be concentrated on three targets: providing, preventing and reducing risks. The special situation of upgrading is that new and old machine components are to be combined in order to operate on trouble free and changed conditions. Depending on the upgrading level, the inherent risks are of different significance and the highest if "old and new is fifty-fifty mixed". The way to success fully manage these problems is to define and follow a General Upgrading Safety Concept which has to be concentrated on the following steps:
- Evaluation of mechanical safety of components remaining in the upgraded machine
- Redesign of replaced components optimally compatible with remaining parts
- Manufacturing and reinstallation of the unit
- Re-commissioning, service and operation on modified conditions
The evaluation of the safety of components which should remain in the upgraded unit is the principal task of a Residual (or Remaining) Life Analysis(RLA). ANDRITZ HYDRO is providing you RLA for all major components using finite elements (FEM), computational flow analysis (CFD) and other computer programs using our experience as generator and turbine manufacturer.
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