Vibratory detection system of cavitation erosion historic and

Vibratory detection system of cavitation erosion: historic and algorithm validation François Lafleur, IREQ: Research Institute of Hydro-Québec, Varennes, QC, Canada lafleur. francois@ireq. ca Date: August 14 th 2012 CAV 2012, Singapore

Agenda > > INTRODUCTION HISTORICAL REVIEW NEW HARDWARE IMPLEMENTATION PRESENT WORK CAVITATION INSPECTION RESULTS • TRANMISSIBILITY FUNCTION • CAVITATION MODEL VALIDATION • > CONCLUSION Groupe – Technologie

INTRODUCTION > Cavitationerosion which results from repeated collapse of transient vapor cavities on solid surfaces is a constant problematic in hydraulic turbine runners and continues to enforce costly repair and loss of revenues. > One way to gain information about the erosion status is to implement acavitationdetection system. Vibratory detection ofcavitationin hydraulic turbine runners is a long time activity at Hydro-Québec (several power plants). > The advancement in this field that will be described in this paper was pioneered by Paul Bourdon (researcher at IREQ) Groupe – Technologie

Why to studycavitationerosion? > Slow evolution process > The utility ignores its aggressiveness according to operating conditions > The machine downtime for inspections is required, therefore ($) > Costly repairs, loss of revenue (4 -6 weeks or more) so its effect have to be minimized Groupe – Technologie

HISTORICAL REVIEW > Several types of intervention were performed at different power plants and on prototypes for the characterization of cavitationto develop a vibratory algorithm of cavitations detection. > Over the years, the system has been used in two principle ways : • The evaluation of the cavitation signature vs. of operating conditions at several power plants (MSV (Mean Square Value in m 2/s 4)). • The continuous monitoring of the absolute cavitation erosion rate (in kg/10 000 h) of 4 groups in a power plant. Groupe – Technologie

Software modules and mathematical treatments > The expertise and methodology were implemented in the form of a completecavitationdetection system including multichannel high speed acquisition hardware and used in conjunction with specific software modules. > There are three mathematical treatments in the processes that are programmed within the various software modules • Datamax (data acquisition) • Cavimax (calculations of the aggressiveness) • Caviciel (continuous monitoring) Groupe – Technologie

Algoritmof cavitationdetection > This system is based on vibration measurements analysis a the lower guide bearing and the algorithm is described in details in the work of Bourdon [1, 4]. > The measurement and analysis of the Mean Square Value (MSV) and its modulation at high frequency (generally 5 to 15 k. Hz) is the base of the cavitationerosion algorithm. > There is three types of data analysis: • • • Data analysis I is basically the high speed data acquisition. Data analysis II is the calculation of the relative aggressiveness of cavitation vs. the operating conditions (cavitation signature) using the pertinent fraction of the modulated MSV (Mean Square Value in m 2/s 4) of acceleration. Data analysis III is use to evaluate the absolute cavitation erosion, by continuous monitoring, the knowledge of a vibratory transmissibility function between the blade and the guide bearing is necessary. Groupe – Technologie

System configuration Detection system of the aggressiveness of cavitation 1) Measure the vibration signal at the lower guide bearing plus tachometer • 3) Data analysis • 2) mathematical treatments Two methods of measuring the aggressiveness of cavitation: • Signatures of cavitation: measures (m/s 2)2 • Continuous measurements: absolute measurements kg or kg/10, 000 h Groupe – Technologie Optimize the operating procedure of hydraulic turbines Allow maintenance just in time

Cavitationsignature detection vs. operating conditions > Cavitationsignature refers to relative aggressiveness of cavitationvs. the operating conditions. > One or more accelerometers with mounting frequencies of 45 k. Hz or higher are installed at the lower guide bearing. > The data acquisition procedure includes several steps from 0% to 100% of guide vane opening. At every step there are 30 blocks of 6 seconds time data recording at a rate of 100 ksample/seconds. A sensors verification step at 200 ksample/seconds is also performed. Groupe – Technologie

Continuous monitoring of the absolute cavitation erosion Groupe Working Instantaneous erosion (Kg/10 000 hours) Vibration Érosion cumulative (Kg) Groupe – Technologie

Continuous monitoring of the absolute cavitationerosion > The continuous monitoring of absolute cavitationerosion is performed using the CAVICIEL software module. > This monitoring requires similar instrumentation than relativecavitationdetection and the same information about the runner characteristics as well as the knowledge of a vibratory transmissibility function between the blade and the guide bearing. > A series of 32 blocks of time at a sampling rate of 65536 samples/second are performed sequentially on the monitored group of the power plant. > Continuous monitoring of 4 groups of high-power hydrogenerators (> 300 MW) at the Robert Bourassa power plant since year 2000. Groupe – Technologie

IMPROVEMENT TO THE CAVITATION DECTECTION SYSTEM > In 2009, a new hardware version of the system was developed and installed. > Optimization of the availability of the cavitation system. > The reliability of the computer and the development of a fail proof reboot procedure and remote control of the system improved the availability of the system. > Robert Bourassa power plant is approximately 1400 km from the IREQ research : remote contro and access is one of the key parameter in the success on the monitoring. Groupe – Technologie

PRESENT WORK > The follow up of reliability of the new system > Updating and documenting the methodology of cavitationdamage inspection for the purpose of modeling thecavitationerosion. > Perform the evaluation of damage on a regular basis (2 years) to be able to make adjustments t the model parameters. > Evaluation of the transmissibility function > Validation of thecavitationerosion model Groupe – Technologie

CAVITATION INSPECTION RESULTS Ø Ø Filling method : A filling method was developed over the year at IREQ using standard water based latex caulking tube. A period of less than 4 hours is required to perform this inspection and the metal loss is available automatically using an analysis template. Groupe – Technologie

Normalized IEC 60609 method : > For this evaluation, the cavitation defects volume are evaluated by an approximation of the overall dimensions of the defect. A correction factor (usually 0. 5 is applied) to the results. > The time period to perform the IEC 60609 measurements is similar to the filling method but the analysis is longer. > The over evaluation of the IEC method is of 1. 70 in average from real cavitationdefect volume from the filling method. Groupe – Technologie

CAVITATION INSPECTION RESULTS COMPARISON OF CAVITATION INSPECTION RESULTS Filling method Blade no. Volume of latex caulk (cm 3) IEC 60609 method equivalent weight of inox steel (kg) Blade no. equivalent weight of inox stell (kg) 1 147, 9 1, 18 1 1, 66 2 66, 5 0, 53 2 1, 14 3 88, 1 0, 71 3 1, 25 4 88, 1 0, 71 4 1, 30 5 327, 4 2, 62 5 5, 07 6 44, 9 0, 36 6 0, 47 7 147, 9 1, 18 7 2, 69 8 236 1, 89 8 3, 32 9 307, 5 2, 46 9 2, 64 10 41, 5 0, 33 10 0, 46 11 58, 2 0, 47 11 1, 21 Total 1553, 9 12, 45 Total 21, 20 Estimated time since last repair (2007) of cavitation erosion damage: 18335 hours Calculated Erosion rate (Filling method) 6. 79 kg/10000 hours Groupe – Technologie Calculated Erosion rate (IEC 60609 method) 11. 56 kg/10000 hours

TRANMISSIBILITY FUNCTION > Evaluation of the transmissibility function results between the blades and the lower guide bearing in different conditions were performed. > The discrepancies of the between the use of the transmissibility function in water or in air are presently in evaluation. Groupe – Technologie

CAVITATION MODEL VALIDATION > The cavitationmodel validation is based on the results of the next cavitationerosion visual inspection planned in 2013. > Theses information will give the erosion rate in this period and will be compared with thecavitationsystem result. > The enhanced reliability of the new system will allow having complete results over th same period. Groupe – Technologie

CAVITATION MODEL VALIDATION > A statistical model will also be study to find a relation between the operating conditions and the cavitationerosion. Groupe – Technologie

CONCLUSION (1) > A detection system gives more frequently update information about the cavitationerosion of blades. This information can be used to optimize the power plant exploitation. > A vibratorycavitationsystem was developed at Hydro-Québec. This system allows performing relative and absolute measurement cavitation of damage. > The reliability of the initial system was not optimum due to computer and exploitation syste failures. The new hardware version of the system is proven to be more reliable. Groupe – Technologie

CONCLUSION (2) > The validation of the cavitationerosion algorithm is based on visual inspection performed every 2 years. > This work showed the efficiency of a filling method developed over the year at IREQ using standard water based latex caulking tube. > This method is rapid and gives the exact volume of eroded material needed to validate the cavitationmodel over the time. > Future work will focus on model validation, new approache of absolutecavitationerosion estimation based on the used of the air transmissibility function and the uses of a statistical model. Groupe – Technologie

REFERENCES (in the paper) > > > > > [1] Bourdon, Paul, D “ étection. Vibratoirede l’érosionde cavitationdes turbines Francis”, Ph. D. thesis, École Polytechniquede Lausanne, thesis no 2295 (2000), 406 pages. [2] Bourdon, P. , Simoneau, R. , Lavigne, P. , “A vibratory. Approchto the Detection of Erosive Cavitation”, ASME International Symposium on Cavitationand Erosion in fluid system, San Francisco, California, December 1989. [3] Bourdon, P. , Simoneau, R. , Avellan, F. , “Hydraulic Turbine Cavitation. Pitting Detection by Monitoring Runner Vibration”, Canadian Electrical Reseasch. Projet 307 G 657 Report, June 1993, Montréal, Canada. (Available from CATI International). [4] IREQ internal reports, IREQ: 99 -191 C, 99 -197 C, 2000 -129 C, 2000 -132 C, 2001 -039 C, 2001078 C, 2011 -0067. [5] Mossoba, Y. , “Centrale Sept-Chutes: Expertisesur la Cavitationdu Groupe 2 par la Detection Vibratoire”, Hydro-Québec internal report (APP 2010 1065), 2010. [6] Mossoba, Y. , “On-Line. Cavitation. Monitoring”, Hydraulic Plant Interest Life Group (HPLIG), CEATI Report No. T 062700 -339, January 2009. [7] Tôn-Thât, L. , “Experimental comparison of cavitationerosion rates of different steels used in hydraulic turbines”, 2010 IOP Conf. Ser. : Earth Environ. Sci. 12 012052. [8] Tôn-Thât, L. , “Cavitationerosion behavior of high strength steels”, 2012 International Symposium on. Cavitation, Singapore. [9] Simoneau, R. , "Austenitic stainless steel with high cavitationerosion resistance, " USA Patent US 4, 751, 046, 1988. [10] CEI/IEC 60609 -1: 2004, Internal Standard, Hydraulic turbines, storage pumpsandpumpturbines –Cavitationpitting evaluation –Part 1: Evaluation in reaction turbines, storage pumps and pump-turbines. Groupe – Technologie