Bearing Load Measurement in a Hydropower Unit Using Strain Gauges Installed Inside Pivot Pin
- 286 Downloads
To determine a machine’s mechanical condition it is of importance to know the radial bearing forces in the machine. Radial forces are caused by magnetic pull forces in the generator, clamped shafts, mass unbalance and flow properties around the turbine. Measuring the shaft displacement in the bearing or the bearing housing acceleration is not sufficient for status determination of a vertical hydropower unit. It is the magnitude and frequencies of the radial forces in combination with structure properties which give information as to whether a measured value is harmful or not. This paper presents an alternative method for measurement of radial bearing load in a hydropower unit. The method presented in this paper is based on strain measurements on pivot pins. The pivot pins are placed behind the bearing pad and the radial loads acting on the pad propagate through the pivot pin. New pivot pins were purchased and equipped with strain gauges. The new pivot pins were calibrated and a transfer function between applied load and measured output voltage was identified for each pivot pin. After calibration the pivot pins were installed in a vertical hydropower unit. Measurements were performed for several different operating modes of the hydropower unit. To verify that the measured load levels were of right order of magnitude, the radial bearing loads were calculated from numerical simulations of bearing properties and shaft eccentricity measurements. The two methods for determining bearing load showed almost the same results. This indicates that either method can be used to determine bearing load.
KeywordsBearing load Hydropower Strain gauge Shaft displacement Pivot pin
The research presented was carried out as a part of “Swedish Hydropower Centre - SVC”. SVC has been established by the Swedish Energy Agency, Elforsk and Svenska Kraftnät together with Luleå University of Technology, the Royal Institute of Technology, Chalmers University of Technology and Uppsala University. www.svc.nu. We would like to thank VG-Power and Waplans Mekaniska Verkstads AB for manufacturing the modified pivot pins. We would also like to express our appreciation to staff at Vattenfall R&D who helped us in this project and at Vattenfall Service Nord who performed an excellent installation of the modified pivot pins in the hydropower unit.
- 4.International Organization for Standardization (2000) ISO 10816–5: mechanical vibration – Evaluation of machine vibration by measurements on non-rotating parts – Part 5: machine sets in hydraulic power generating and pumping plants. GenevaGoogle Scholar
- 5.International Organization for Standardization (2005) ISO 7919–5: mechanical vibration – Evaluation of machine vibration by measurements on rotating shafts –Part 5: machine sets in hydraulic power generating and pumping plants. GenevaGoogle Scholar
- 6.Gustavsson R, K., Andanpää J-O (2004) The influence of magnetic pull on the stability of generator rotors. Paper presented at the The 10th international symposium on transport phenomena and dynamics of rotating machinery, Honolulu, HawaiiGoogle Scholar
- 9.Peng G, Qin L, Wang Z, Tian H, Luo Y (2009) Structure vibration of hydropower house induced by Francis turbine based on CFD. In: 2008 Proceedings of the ASME Fluids Engineering Division Summer Conference, FEDSM 2008, Jacksonville, FL, 2008 ASME Fluids Engineering Division Summer Conference, FEDSM 2008, pp 1173–1178Google Scholar
- 10.Someya T (1989) Journal-bearing databook. Springer, BerlinGoogle Scholar
- 11.Grant R (1980) Shaft alignment methods with strain gauges and load cells. SNAME Marine Technology 17:8–15Google Scholar
- 12.Cervantes M, Jansson I, Jourak A, Glavatskih S, Aidanpää J-O (2008) Porjus U9A full-scale hydropower research facility. In: Proceedings of the 24th Symposium on Hydraulic Machinery and Systems, Foz do Iguassu, Brazil, p 9Google Scholar
- 13.Gustavsson R, Aidanpää J-O (2003) Using strain gauges to measure load on hydro generator guide bearings. Hydro Review WorldwideGoogle Scholar
- 14.San Andrés L, De Santiago O (2005) Identification of bearing force coefficients in flexible rotors-extensions to a field method. In: Proceedings of the World Tribology Congress III - 2005, Washington, D.C., 2005 World Tribology Congress III. pp 47–48Google Scholar
- 15.Gustavsson RK, Lundström ML, Aidanpää JO (2005) Determination of journal bearing stiffness and damping at hydropower generators using strain gauges. In: Proceedings of the ASME Power Conference, 2005, Chicago, IL, 2005 ASME Power Conference, pp 933–940Google Scholar