Standards Development

Scope

This International Standard applies to runners of reaction turbines, regardless of their size and capacity.
These may include radial turbines such as Francis turbines, as well axial turbines such as Kaplan and
propeller turbines, including diagonal turbines, in all possible configurations. In the case of turbine runners with adjustable blades, the internal mechanical components of the blades’ adjustment mechanism are excluded from this document.
This document outlines the recommended methodologies for conducting a fatigue assessment of turbine runners. It encompasses several key aspects, such as defining the load events to be considered during the assessment, determining stresses for each of these load events, as well as the detailed approaches for assessing fatigue for new and existing runners. Additionally, it includes manufacturing and quality assurance requirements that must be complied with to achieve the desired material fatigue properties and effectively apply the proposed fatigue assessment methodologies. This document also covers best practices for analyzing on-site strain gauge measurements performed on existing runners to evaluate their fatigue life.
The purpose of this document is to provide guidelines to assess fatigue in new and existing turbine
runners. It does not specify if a fatigue assessment must be performed or not for a given runner. However, it includes an annex that provides guidance to evaluate the necessity of realizing a fatigue assessment or not for a given runner. The methods described in this document can also be used for remaining life assessments of in-service runners. However, caution should be exercised as the assessed runner materials’ fatigue properties and quality level could differ from the prescriptions found in the manufacturing and quality assurance section of this standard which have been defined for new runners.

Purpose

The deregulation of the energy market coupled with the arrival on the electricity market of intermittent and decentralized forms of production, such as wind and solar power, change the way the hydraulic turbine are operated over the world. The need for flexibility that comes with this new paradigm induces more frequent transients (e.g. start-ups, shutdowns) and more frequent operation at non-optimal conditions (e.g. part loads, no-load). This, in turn, directly increases the damage due to fatigue on the tur bines, particularly on the runners.

However, there is presently no standardized approach to deal with fatigue of turbine runners in the industry. This variability causes discrepancy when different methodologies are used to evaluate the residual life or the risk of cracking of an existing runner. It also renders difficult – if not impossible – the comparison of different runners between them if different methodologies have been used to evaluate their behaviour in fatigue. Similarly, the comparison between different runner designs are biased by the methodology that is used to analyse fatigue.

It is hence proposed to write a standard that would cover the way fatigue of hydraulic turbine runners is dealt with from the design stage to the quality assurance of the manufactured runner. This standard will help gather the information of different CEI and non-CEI standards that already exists (ASTM, ASME, DIN, CSA, etc.) on manufacturing and quality assurance and address the particularities of the hydraulic turbine dynamic behaviour. It will help the industry adopt fitness-for-service approaches that it will, in turn, help to better evaluate what should trigger a runner rehabilitation and help to better evaluate the fatigue life of newly designed runners in view of the anticipated operating conditions.