Strain gauge measurements of rotating parts with telemetry

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1 Strain gauge measurements of rotating parts with telemetry IGHEM 2012 Trondheim, /29 Presentation name place or presenter YYYY-MM-DD 1

2 Strain gauge measurements of rotating parts with telemetry 1. Introduction 2. Functionality of telemetry system 3. Configuration of data transmission 4. Strain gauge application 5. Measurement 6. Data Evaluation 7. Summary 8. References 2

3 Introduction Modern design of hydraulic turbines aims to achieve very high levels of efficiency and structural integrity in the environment of highly variable loading conditions. To combine those requirements, a profound knowledge of static and dynamic loads acting on hydraulic components is necessary. The knowledge of dynamic loads is often derived from strain gauge measurements using telemetry systems. With this technology it is possible to measure signals from the rotating (e.g. runner strains) and stationary (e.g. presure pulsations) system time synchronous. 3

Functionality of telemetry system Contact less data

gauges) from the rotating system to a stationary

signals (voltage to frequency) to a subcarrier

frequency Subcarrier mix modulated to main carrier

inside receiver to subcarrier mix Conversion from

4 Functionality of telemetry system Contact less data transmission of sensor signals (generally strain gauges) from the rotating system to a stationary receiver Amplification and conversion of sensor signals (voltage to frequency) to a subcarrier frequency Merging the channel specific subcarrier frequency Subcarrier mix modulated to main carrier frequency by HFmodulator Demodulation of HF-signal inside receiver to subcarrier mix Conversion from frequency to voltage signal Analog signal provided by analog amplifier 4

5 Configuration of data transmission Data transmission through air stationary antenna rotating antenna batteries and remote system telemetry system strain gauges 5

6 Configuration of data transmission Data transmission through water batteries and remote system telemetry system strain gauges rotating antenna stationary antenna 6

For exact position of the strain gauge sensor, steel templates

7 Application steel patterns In order to get the exact position for the strain gauge application, special tools are used. For exact position of the strain gauge sensor, steel templates are used. These are derived from the CAD-model of the Francis runner. 7

8 Application FARO-Arm Another possibility to locate exact strain gauge positions is the usage of the FARO-Arm. This method of defining strain gauge positions on the prototype is used specially for Kaplan runners, where the usage of steel templates is not practicable. 8

9 Application strain gauge application Strain gauge are bond to the surface by using a modified alkyl cyanoacrylate compound 9

Application protection layer Application of epoxy layer in order to protect the strain gauge wires against water irruption Special surface treatment necessary in order to improve adhesion of the

10 Application protection layer Application of epoxy layer in order to protect the strain gauge wires against water irruption Special surface treatment necessary in order to improve adhesion of the epoxy Epoxy is shaped to minimize effects on hydraulic For layouts working under high pressure (p > 3 bar) or special circumstances (e.g. high sand content), an additional local coating layer is applied 10

11 Data Evaluation Start up procedure Performing a strain gauge measurement by using a telemetry system offers the possibility of online assessment of recorded strain gauge data. Especially for transient load conditions, a fast and reliable online assessment of these load conditions is possible. They could be optimized in matters of time, dynamic loading and partial damage. Start up 2 Start up 4 Start up 1 Start up 3 11

12 Data Evaluation Load rejection Besides the start up procedure also the behaviour during load rejection can be observed and, if necessary, be adapted Highest dynamic strain occur during load rejection By adapting the distributor opening, significant improvements can be achieved 12

13 Data Evaluation Mean stress Measured mean stresses are normed to stresses at speed no load Plotted lines indicate the characteristic for crown (gray) and band (blue) Dots represent the calculated values from the Finite Element Analysis Deviations caused by: geometrical deviations deviations in loading condition strain gauge position flow disturbances 13

14 Data Evaluation Dynamic stress Measured dynamic stresses are normed to stresses at speed no load Plotted lines indicate the characteristic for crown (gray) and band (blue) Characteristic peak-to-peak appr. 3% of highest peaks neglected 14

15 Data Evaluation Waterfall Load ramp with continous opening from 0-100% power This enables you to get a fast a clear overview of unit behaviour over the complete operating range and where deeper investigation is necessary. 15

Data Evaluation Partial Damage Partial damage calculation based on measured strain signals, load universe, material parameters and rainflow counting

16 Data Evaluation Partial Damage Partial damage calculation based on measured strain signals, load universe, material parameters and rainflow counting Partial damage is standardized to partial damage for Pmax transient load conditions are the main fatigue contributor higher partial damage at runner band 16

17 Summary Performing strain gauge measurements using telemetry systems is state of the art Realization with almost no limitations of unit application and kind of runners Based on database of already performed strain gauge measurements, a calibrated procedure for predicting static and dynamic stresses has been developed and optimized This enables you to optimize runners with regard to static and dynamic stress as well as to fatigue behaviour 17

18 References No. of realized and projected strain gauge measurements Francis runner Kaplan runner Pelton runner Data transmission through air 6-2 Data transmission through water 3 projected n.a. 18

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Underground M3 progress meeting 16 th month --- Strain sensors development IMM Bologna

Underground M3 progress meeting 16 th month --- Strain sensors development IMM Bologna Matteo Ferri, Alberto Roncaglia Institute of Microelectronics and Microsystems (IMM) Bologna Unit OUTLINE MEMS Action