Index Terms Cracks, Corrosion, Failure, Fatigue, Generator, Nut Guard, Overhaul, Rehabilitation, Turbine, Shaft, Standardization, Vibrations

Transcription

1 Standardization as Prevention of Fatigue Cracking of Hydraulic Turbine-Generator Shaft T. Maricic, Asset Management Dept. Niagara Plant Group, OPG D. Haber, Asset Management Dept. Niagara Plant Group, OPG S Pejovic, Dept. of Civil Engineering, Univ. of Toronto 1 Abstract - Design, construction and operation of Hydropower plants are complex tasks. A large number of details must be carefully considered, coordinated and executed in order that the projects achieve safe and economical operation. Corrosion fatigue cracking of horizontal turbine-generator shafts has been thoroughly examined and discussed in the last twenty years. As a result of corrosion fatigue cracking, in most cases, catastrophic failures occurred. Excessive damages of vertical shaft couplings, discovered during turbine rehabilitation, have raised concerns regarding the value of nut guard application, as well those of corrosion damage rectification and repair techniques. Because of the consequences of shaft failure the following paper will provide the rationale for contribution to the respective standard. Index Terms Cracks, Corrosion, Failure, Fatigue, Generator, Nut Guard, Overhaul, Rehabilitation, Turbine, Shaft, Standardization, Vibrations T I. INTRODUCTION he growth of electricity demand and subsequent supply, and particularly the heightened interest in hydropower, is being experienced worldwide. It is a growth and interest that shows no sign of letting up [16], [17]. Design, construction and operation of Hydropower plants are complex tasks. Thousands of details must be accurate, well thought out, carefully coordinated and executed in order that a project achieves safe and economical operation. If only a few of these myriad details are overlooked, under-estimated or improperly linked, significant complications may quickly arise [8], [13], [22]. Increasing demand for "clean" energy is the momentum behind the construction of small low head hydroelectric plants. Water quality in rivers tends to deteriorate materials and corrosion becomes of growing importance. Corrosion and longlife fatigue are important factors in the design of low head hydraulic turbines and their components particularly in salt water pumped storage plants, tidal, and direct-from-ocean-wave power [22]. Areas with scratches, fillets, and weldments are critical areas in the This work was supported in part by Ontario Power Generation and University of Toronto T. Maricic, Asset Management Dept. Niagara Plant Group, OPG( tim.maricic@opg.com) D. Haber, Asset Management Dept. Niagara Plant Group, OPG( don.haber@opg.com) S. Pejovic is with the Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4, Canada,( pejovics@asme.org). fatigue performance of turbine shafts, particularly if they are exposed to water. Bending stresses in the rotating shaft are the primary cause of fatigue. Low head S-type turbines, due to their special design, are most vulnerable to cracking. In bulb turbines, the runner is located on an overhang of the shaft. Bending stresses however can be kept low if vibrations are controlled to be low. This paper deals with introduction of guidelines for standardization of shaft to runner flange coupling design features. These features include: shaft weldment design, heat treatment, corrosion protection and technology of application, additional fixture (coupling guard) design, and preventive and scheduled maintenance. The paper also deals with shaft failures explicitly linking elevated vibrations with diminishing life expectancy. II. CORROSION FATIGUE Corrosion fatigue aspects on low and medium strength structural steels of different qualities in wet environments, ranging from clean water to seawater introduce damaging processes in metals consisting of fatigue crack initiation and propagation.. In some instances, one of these components may be much more important than the other, but in general, they are both critical. Therefore, maintenance and inspections are of paramount importance. With high cycle fatigue, the total number of cycles and their amplitudes lead to failure in a short period of time. The frequency effect is related to the time dependence of corrosion. Effects of geometrical stress concentration and corrosion add to this. The corrosive medium will further reduce the notched specimen's cyclic life below that observed in air. Therefore, corrosion does not simply produce a sharp notch that acts as a stress concentrator, it also adds to the detrimental effect of the geometric stress concentration on fatigue life. The vast amount of data that has been reported shows the effect of environment, and stress ratio (minimum to maximum stress) has effects on crack growth in water. III. VIBRATION SEVERITY Excited forces in the hydro generator unit include those from hydraulic, mechanical and electrical sources. The test value is compared with standard or permitted values. Some nations and organizations suggest standards based upon the test material. When the unit vibration satisfies these standards, normal operation and safety are usually ensured [10], [14]. At the present time international vibration standards do not exist. Although vibration standards for rotating machinery include the vibration severity for various kinds of machines, the vibration severity for hydraulic turbines should also consider the following characteristics:

2 2 (i) low speed operation (general standard are for speeds greater than 600 rpm), (ii) vertical shaft configuration (standards for general machines are given based on horizontal shafts), (iii) turbines/pumps with low speed and large diameter, (iv) uneven or pulsating vibrations (hydraulic excitations) A. Vibration and hydro unit lifetime Hydro units should provide a service life of at least 4 years and/or hours before requiring a general overhaul. The average service life before requiring a major rehabilitation should be not less than 30 years. Actual lifetime will depend upon the maintenance performed and mode of operation (e.g. a unit start may be considered equivalent to 8-15 operating hours; a runaway event could be much higher depending on the duration of the event). Investigations on many units have shown that vibrations experienced by hydro units increase with operating hours. This may be caused by gradual erosion and corrosion of the unit and its bearings (generator supports, spider, bearing inserts, etc.), and also by abrasive and cavitation destruction of the runner and associated turbine components, which disturbs runner balance. As the result vibration of the unit reaches boundary "trip values", and the unit must be removed from service and overhauled. Several methods and formulae for the calculation (estimation) of average lifetime between overhauls [4] [10], [14], [18], [28] are based on measured vibration of the unit The vibration standards should take into account vibration severity as the main source of crack s propagation. Severity of vibrations directly influences the rate of crack propagation which in turn correlates to increased maintenance requirements and operational risk. B. Hydraulic transients Transients and associated vibrations result in the highest pressures experienced in the waterways and associated conduits. They cause critical stresses in the overall hydraulic and mechanical structures and therefore must be carefully considered during design [1], [4], [5], [6], [7],[8], [9], [10], [11], [12], [13], [14], [15]. C. Runaway protection In designing a hydraulic machine runaway operating conditions must be carefully considered in order to achieve a balance between safety and costs of manufacturing and maintenance [4], [13], [22]. By way of example, a bulb turbine unit has protective devices which receive the control impulse only after a significant time lag, acting only when the runner rotates already at high runaway speed. Devices such as plain sliding gates are only activated when the runner has reached full runaway speed. Runaway speed of this turbine is a multiple (2 to 3.3) of the rated speed, depending on the design. These turbines experience frequent runaway conditions and associated severe vibrations. As a result shaft crack propagation is a significant issue. D. Reliability The value of energy produced depends on the mode of production. Of course, the goal is to achieve high rate of production with low cost of operation and maintenance for as long as possible. On the other hand, life of the unit is dependent upon the operating conditions. There are some ranges and conditions which reduce the life of the unit. Characteristics of theses zones are higher levels of vibrations, cavitation, and flow speed. It is well known that oscillations of the unit are indicators for operating qualities (cavitation characteristic of turbine, resonance in any component). During unit commissioning the characteristics of oscillation may be used to determine the degree of success for the installation or overhaul. Finally, this data may be used to determine the best technical /economical operating strategy for the unit [1], [10], [11], [13], [14], [18], [24], [25], [28]. Every unit problem may be predicted. Proper investigation and analyses of the results provide information about those. Developing systems for diagnosing potential problems is the most effective method for increasing reliability and maximizing time between overhauls. The guidelines for determination of vibration conditions have been developed based upon numerous experiments [8], [10], [14]. There have also been some international attempts for standardization of allowable vibration. E. Fatigue Fatigue is the progressive and localised structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that lead to structural failure. The maximum values of stress that result in fatigue failure are often significantly less than the ultimate tensile stress, and may be below the yield stress of the material. The problems associated with cavitation erosion, transient states and vibrations may arise in operational installations, sometimes after several years of seemingly normal operation. These problems usually relate to emergency or catastrophic cases, damage to the plant due to breakdown of equipment, excessive vibrations or other similar situations. To determine the root cause of the problem and develop an effective remedy, a very detailed and precise study must be undertaken. F. Reconstruction Enlargement of Units The reconstruction or enlarging of an existing plant should begin with a feasibility study and follow the same steps outlined previously. Frequently cavitation, vibrations and transient regimes are more dangerous in reconstructed or enlarged facilities than in existing ones. To preclude these problems a very detailed design study must be undertaken. Extrapolation of the information from existing design documentation is insufficient. IV. TURBINE SHAFT FAILURE CASE STUDIES To illustrate the possible causes and origins of specific shaft failures, several cases studies will be introduced. The goal is to illustrate the issues, and is not intended to apportion fault or blame on any party or plant owner. In all cases, the role of the design process, its connection to operation, maintenance and the specific role of vibration will be illustrated, and comments will be made about the possible value and role of the standardization. Two cases are described where certain

3 3 similarity can be recognized. A. Horizontal Kaplan bulb unit 28 MW rated output After approximately twenty years of service, a horizontal Kaplan bulb unit failed due to catastrophic shaft failure. Fatigue fractures were found along the shaft perimeter in the transition radius from shaft to coupling flange. A combination of factors have induced and influenced the fatigue cracking. (Figure 1). Iron Gate 2 Specific speed of this turbines should have been higher in order to reduce the vibration Figure 1 Sixteen units each 28 MW 16 Bulb units Power 28 MW each Head 7.45 m Flow 452 m3/s Speed 62.7 rpm Rated head 7.5 m Zone of intolerable bearing vibration Accident has repeated frequently 1) Design and Technological factors The turbine shaft assembly was designed as a weldment of shaft flanges and shaft body. Due to significant flange and shaft sizes, length and diameter, the transition from shaft body to flange body was designed as a conical transition with a relatively small transition radius. Forged shaft flanges and body were welded into an assembly by large full penetration welds. Welds during the manufacturing process connecting shaft and flange, created a heat affected zone overlapping the transition radius. Residual stresses were induced on the outside surface of the transition from shaft into flange. Anticorrosion protection of the shaft coupling area exposed to water, was found delaminated from the metal surface, resulting in corrosion in those areas. (Figure 6b). 2) Operational factors The horizontal shaft, beside experiencing constant cyclic loads, also experienced elevated vibration levels. These vibrations considerably reduced the longevity of the turbine shaft and the entire unit, See paragraph III. Vibration Severity and [4], [10], [14], [24], [26] for more information. Periodic inspection of the turbine shaft coupling wet zone, (visual inspection of corrosion protection and magnetic particle inspection), was not performed since the first commissioning of the unit. 3) Consequential damages Preliminary stress analysis, determined that stress levels in the critical transition area (fillet radius area) were above the admissible ultimate strength of the material. 14 Shaft coupling was in a wet environment, and due to exposure to water, its mechanical abilities were significantly diminished. Amplitude 2A (mm) Bulb turbine measured vibrations at 50, 75 and 100% and extrapolated to 110% 0.5 Head Power output (%) Equivalent time of operation (%) Figure 2 Vibrations sizably reduce the longevity of unit. Based on measured vibrations amplitude 2A equivalent time of operation has been calculated According to stress corrosion theory and empirical findings, bending stresses above 25 MPa (3625 psi) for couplings exposed to water, and above 40 MPa (5800 psi) for shaft couplings exposed to corrosive water, are detrimental and will produce surface material cracking and subsequently lead to the corrosion fatigue. For more information see [22]. Figure 3 Horizontal shaft; Cracks appearance Since stress levels in the affected coupling area were above the recommended values, classical stress corrosion fatigue cracking occurred (Figure 3, Figure 6). 4) Remedial actions Shaft replacement was the viable solution. B. Vertical Francis unit 57.5 MW rated output A 60 year old (25 years since last unit rehabilitation) vertical Francis unit originally rated at 57.5 MW has had two ubsequent power output upgrades and experienced excessive corrosion at turbine coupling side and fatigue cracking.

4 4 a b Figure 6 a Horizontal shaft crack; b. Shaft to flange transition radius; damaged protective coating and shaft material crack along the perimeter The last overhaul that was performed in 1982, included a runner replacement which increased the power output from 57.5 MW to 72 MW. After extensive economical and technical analysis, the Owner decided to increase the power output to 74 MW. Results of the analysis of unit power output increase to 74MW versus 72MW combined with actual findings after dismantling could be outlined as follows: 1) Cavitation and cavitational damage Cavitation and cavitational unit constraints were analyzed. Runner model test results were reviewed and potential cavitational damage was been estimated based on similarity rule. Cavitation and cavitational damages of prototype do not have similarity with the turbine model, but potential increase in damage may be determined by analyzing site testing results [1], [25]. In order to determine the increased amount of cavitation damage, an annual inspection was recommended, with subsequent repair work to be carried out every three years. These kind of repairs are not, unfortunately, permanent fixes as they are limited by the materials ability to maintain structural integrity after being compromised by repeated welding. 2) Transient analysis and vibration The existence of increased pressure pulsation was presumed, and should be addressed by direct monitoring, due to dissimilarity with model test data. Vibration levels imposed by pressure pulsation changes cannot be predicted, since pressure pulsation measurements obtained during modeling are similar to the prototype in frequency of occurrence but not in magnitude. Careful monitoring and recording of the pressure pulsation shall be recommended, if not immediately pursued, pending first annual runner and draft tube inspection (See III. Vibration Severity). 3) As found damages Turbine Shaft flange and Shaft body were subjected to Machine shop dimensional check. Dimensional check on lathe was performed and results noted as per IEEE (R2001). Heavy corrosion was found at the turbine flange end in the wet zone below the shaft seal journal, as well as a variety of physical damages on the flange imposed by tack welding of nut keeper plates, along with at least two consecutive rehabilitations carried out in the past. Figure 5 Vertical Francis shaft with Nut Guard dismantled The bolt cover, as found designed and installed, at its internal edge, has created a permanent corroded groove along the shaft s diameter. This groove was located in the radius transition area (Figure 7). Figure 7 Vertical Francis shaft with groove damage Figure 8 Vertical Francis Shaft flange crack Figure 4 Vertical Francis shaft under Magnetic particle testing

5 5 4) Shaft crack and fatigue Along with the machine shop dimensional check magnetic particle inspection discovered a crack in the shaft flange. Analysis of the crack led to the stress level calculation check of turbine shaft. Multiple calculations were performed according to various standards and norms. All calculation results showed stresses above the maxim design loads power outputs above 60 MW. The length and depth of the crack, its position and preliminary calculations, led towards the conclusion that the longevity of shaft is impaired. Analysis of the shaft fracture failure considered the coupling bolt stud body sizes. Measured and recorded as found coupling bolt stud sizes were mm ( ) to mm ( ) smaller than the respective bolt holes. Originally designed as a fitted bolt shear coupling, respective gaps have turned this shaft coupling into friction coupling. Therefore, flange calculations performed were considered as two cases describing the moments of shearing forces acting at the flange section in each case. In the first case the bolts were not fully tightened. The axial load caused the section of the flange to turn through an angle without warping. In the second case the bolts were assumed to be fully tightened, causing considerable pre stressing. The axial load on the shaft will therefore result in the deformation of the flange section, and stresses in the flange should be calculated for bending as an annular plate with the outer edge rigidly fixed by bolts and the inner edge connected to a shell. Resulting calculated stresses were higher than permissible values for radial and tangential stresses for the flange shaft. This specific unit has already been running above 60 MW for a long period of time. Shaft overstress and shaft flange over stress was confirmed and defined as the limiting factor of unit's operation from the perspective of potential total shaft failure. 5) Remedial action, Opinion and Recommendation Existing shaft and shaft flange were subjected to machining process in two steps, removing mm (0.025 ) then mm (0.050 ), resulting in the elimination of the crack. Along with crack removal, the remaining excessive corrosion and other physical damages found on the flange body were removed. New technological developments and significant improvements in Computerized Fluid Dynamic Analysis have influenced and enhanced turbine runner design to new technical and quality levels. The market is offering turbine runners with higher efficiencies and sizable power output increases. The shaft and runner of the specific unit were found to be at their technological limits. In order to trigger appropriate planning for a shaft and runner replacement, cavitation damage monitoring and a comprehensive Finite Element Analysis and Fracture Mechanic calculations of the turbine shaft were suggested. V. GUIDELINES FOR STANDARDIZATION A. General According to the general layout of the specific unit, units may be designed as two body or three body shafts. Two body shaft units have one generator and one turbine shaft. Three body units have these two shafts as well as an intermediate shaft. An intermediate shaft enables runner removal without dismantling the generator assembly. Small and medium size turbines may be built with vertical or horizontal shafts. Shafts are connected to the runner hub with flanges or keys. B. Horizontal shafts Shafts of small horizontal units are connected to the generator shaft by an elastic coupling. Horizontal shafts are subjected to the weight of the rotating parts causing bending, and to the torque transmitted from turbine to the generator and to the water flow resulting in an axial tensile load (hydraulic thrust load). Horizontal shafts are usually installed on two axial bearings and one thrust bearing as one of these is typically combined with the thrust bearing. C. Vertical shafts Vertical shafts are subjected to axial and torque loads. Tensile stresses exerted on the shafts transmit hydraulic thrust and the entire weight of moving parts of turbine unit. Torque loads transmitted from turbine to generator, exerted on the shaft, create combined shear and tensile stresses. Torsional vibrations imposed by regulation of the unit or by runner run out must also be considered (See paragraph III. Vibration Severity). Finally, lateral loads due to hydraulic or mechanical imbalance need to be taken in account as well. Shaft materials Hydraulic turbine shaft materials are generally high carbon steel forgings. As a cost effective alternative steel piping and flange weldments are used in specific lower cost turbine products. D. Shaft Design Turbine shaft is a cylindrical forged and/or welded part equipped with cone or flange at the turbine end and a flange at generator end. Large turbine shafts are usually designed with large central bore in order to permit material inspection all along the shaft length. The bore is used as air admission pipe for draft tube vortex core instability rectification, or as oil conduit in Kaplan units. Flange coupling design, could be friction coupling with pre tensioned bolts and shear coupling with fitted bolts. Friction coupling design requires precise bolt preload definition combined with exact pre tensioning scheme. Fitted bolt design, or shear coupling design, requires precise bolt to hole gap tolerance. For horizontal shafts and for unit power upgrades, coupling bolt studs shall be fitted with minimal clearance of 0.02 mm ( ) but not larger than 0.04 mm ( ).These tolerances have been proven in application on new installation and on retrofit of hydro turbine units worldwide.

6 6 For horizontal shaft couplings avoid nominal bending stress, including stress concentration factors, above 25 MPa (3625 psi) (equal to 1/10 of yield stress) for corrosive water and above 40 MPa (5800 psi) (equal to 1/6 of yield stress) for shaft couplings exposed to corrosive water, protected with fiber reinforced epoxy, compatible anticorrosive coating, or cladding with Inconel 625 [1]. For vertical shafts, simultaneously subjected to tension and torsion, permissible torsional stress shall be 40 to 44 MPa (5700 to 6400 psi), (equal to 1/6 of yield stress) which including the tensile stresses amounts to a combined stress of about 83 to 84 MPa (12100 to psi) (equal to 1/3 of yield stress) [8], [19]. Avoid design of welded joints in proximity of transition radiuses with assurance that heat affected zone is outside of the coupling area. Avoid stress raisers, notches, sharp corners, shoulder fillets with small radiuses, partial protrusion welds or abrupt changes of shaft geometry. Do not specify high alloy steel as shaft material due to possible appearance of galvanic corrosion. Specify technological procedures improving and increasing corrosion fatigue resistance. Shot peening, surface cold working and cladding. Specify the appropriate coating of the shaft to runner coupling, resistant to respective water quality. Perform corrosion protection coating as well as filler application with excessive care performing those in clean and non humid environment per technical specification. Design adequate Coupling guard (Split cover) (Figure 8.) in order to protect shaft to flange transition zone including bolts and nuts from water and to eliminate stud and nut pumping effect. Figure 9 Coupling guard, final solution to protect from fatigue corrosion Use adequate filler medium for filling the Coupling guard volume in order to eliminate any access of the moisture into coupling area. Design and apply cathodic protection for the entire shaft submerged into seawater, or in waters containing aggressive chemicals. Combine cathodic protection with anticorrosion coating and Coupling guard. Include shaft vibration monitoring devices and use probes as an element of the comprehensive vibration monitoring system. E. Shaft Manufacturing Perform full penetration welds. Perform stress relief or other adequate post welding treatment required for specific material and adopted designed specification. Perform rigorous Quality Control Program and nondestructive testing (Ultrasound, Magnetic Particle and Liquid Penetrant Testing) as required to provide the assurance of proper product quality. F. Assembly procedures Coupling bolts installation and pre stressing to be performed as per specification and in accordance to valid drawings, schematics and art of trade. Alignment of bearings to be performed within prescribed tolerances. Rectification of geometry of the turbine shaft and its integral parts, must not be performed by using any preheating devices or methods. Shaft handling to be performed with extra care particularly during installation, dismantling or handling prior or after transportation. Preparing shafts for turning from horizontal to vertical position has to be according to separate drawing and / or procedure for engineered lift. G. Operational and maintenance procedures Shaft vibration monitoring shall be implemented at all times of unit operation. Periodic inspections of shaft to runner coupling by dismantling of the Coupling Guard shall be performed for horizontal and vertical units after the first year of operation after first commissioning and every major overhaul. Further inspections are required every four years for horizontal shafts and every ten years for vertical shafts. Along with inspections adequate repairs of protective coating and refilling of filler material shall be performed. Monitor and record the history of unit loading, specifically record every load rejection and start up sequence. Finite Element Analysis and Fracture Mechanics Analysis results may be used to predict shaft longevity. Based on carefully collected data, economic analysis may be used to determine allocation of sufficient funds for major unit rehabilitation and shaft replacement. The methodical approach outlined will extend the life expectancy of turbine shafts and will provide a safe operating environment with low residual risk. This approach will minimize unexpected, long and expensive outages due to shaft failures. Safety and health risks shall be minimized as well.

7 7 VI. REFERENCES Periodicals: [1] Denys A., Plunkett T., Ozark-Webbers Falls Turbine Repairs, Waterpower 65 pp [2] Lee T. S., Pejovic S., Air Influence on Similarity of Hydraulic Transients and Vibrations, Transaction of the ASME, Journal of Fluids Engineering, Vol. 118, December 1996, pp << [3] Pejovic S., Understanding the Effects of Draft Tube Vortex Core Resonance, Hydro Review Worldwide, HCI Publications, September 2000, p [4] Pejovic S., Gajic A., Profit Management and Control in Transient and Steady Operation of Hydroelectric Plants, No , Serbian Scientific Society, Belgrade , pp <Profit Management NDS 2002> Books: [5] G.C. Andrews, J.D, Kemper, Canadian Professional Engineering Practice and Ethics, Harcourt, 1999 [6] Guidelines for Analysis of Regulation of Hydroelectric Power Plants,Rusian, Moskva [7] The Guide to Hydropower Mechanical Design, ASME Hydro Power Technical Committee, HCI Publications, 1996 [8] Kovalev, N.N., Hydroturbines, Design and Construction, Translated from Russian, Israel Program for Scientific Translation, Jerusalem, [9] Pejovic, S., and A.P. Boldy, Guidelines to Hydraulic Transient Analysis of Pumping Systems, P&B Press, [10] Ohashi, H., 1991, Editor, Vibration and Oscillation of Hydraulic Machinery, Avebury Technical. [11] Pejovic, S., A.P. Boldy, and D. Obradovic, Guidelines to Hydraulic Transient Analysis, Gower Technical Press Limited, Aldershot, Hampshire GU11 3HR United Kingdom, [12] Pejovic, S., Guidelines to Hydraulic Transients Calculations in Hydra Power Installations, Serbian, Beograd, 1984 [13] Raabe J., Hydro Power: The Design, Use and Function of Hydromechanical, Hydraulic and Electrical Equipment, VDI-Verlag, 1985 [14] Vladislavlev, L.A., 1972, Machine Vibration of Hydroelectric Plant, (in Russian), Moskva. Books (Unpublished): [15] The Guide to Hydropower Mechanical Design, ASME Hydro Power Technical Committee, HCI Publications, New edition planned 2009 Technical Reports: [16] BC Hydro and Power Authority, Inventory of Undeveloped Opportunities at Potential Micro Hydro Sites in British Columbia, E5967, March 2000, [Online]. Available: [17] Energy Information Administration, International Energy Outlook 2007, DOE/EIA-0484(2007), May 2007 [Online]. Available: Karney B.,, Pejovic S., Colombo A., UofT - Supply Mix Submission OPA, August , [18] Pejovic S., in cooperation with Electronic Design, Hydropowerplant Profit On-Line Management and Control, 1996, pp. 4. <Click here for more information> [19] EPRI Norms: Hydro Life Extension Modernization Guidelines; Volume 2, Hydromechanical Equipment, TR V2, Final Report August 2000 [20] T. Maricic Unit 2 Overhaul Report Internal unpublished report of OPG, July 2007 Papers Presented at Conference (Unpublished)s: [21] Pejovic S. Karney W.B. Zhang Q., and G. Kumar G., Smaller Hydro, Higher Risk, IEEE Electrical Power Conference 2007 "Renewable and Alternative Energy Resources" October 25-26, 2007 Montreal, Quebec, Canada Papers Presented at Conferences: [22] Angehrn, R., Eckert R.,, 1990, Service Life of Horizontal Shafts in Low Head Turbines under Corrosion FatigueIAHR 15 th Symposiym, Balgrade [23] Pejovic S., Pressure Surges and Vibrations in Hydropower Plants - Experiences in Yugoslavia, The Current State of Technology in Hydraulic Machinery, Gower Technical,1989, pp [24] Pejovic S., Profit Management and Control of Hydropower and Pump Plants, Proceeding of the International Joint Power Generation Conference, Denver, Colorado, 1997, pp [25] Pejovic S., Similarity in Hydraulic Vibrations of Power Plants, Joint ASCE/ASME Mechanics, Fluids Engineering, and Biomechanics Conference, San Diego, USA 1989, American Society of Mechanical Engineers, Paper 89-FE-4, pp. 5. [26] Pejovic S., Profit On-Line Management and Control of Hydroplants, IAHR Work Group on the Behaviour of Hydraulic Machinery under Steady Oscillatory Conditions, Chatou, France, 1997, Paper G2, pp. 10. <Click here for more information> [27] Pejovic S., Troubleshooting of Turbine Vortex Core Resonance and Air Introduction into the Draft Tube, IAHR Symposium, Lausanne, Switzerland, [28] Pejovic S., Vukosavic D., Vibrations and Economy of Hydropowerplant Operation, IAHR Work Group on the Behaviour of Hydraulic Machinery under Steady Oscillatory Conditions, Milano, 1991, Paper 1, pp. 11. [29] Karney B., Gajic A., Pejovic S., Case Studies Our Experience in Hydraulic Transients and Vibrations, Proceedings of the International Conference on CSHS03,,Belgrade, [30] Sallaberger M., Haas M., Michaud C., Maricic T., 2005, Advanced Design of Francis Runner for Refurbishment Projects, Waterpower Conference CD. Standards: [31] IEEE Standard for Hydraulic Turbine and Generator Integrally Forged Shaft Couplings and Shaft Runout Tolerances, 2001, IEEE Std (R2001) VII. BIOGRAPHIES Dr. Stanislav Pejovic was born in Belgrade, Serbia and received his Ph.D. Degree from University of Belgrade. At the Department of Mechanical Engineering he served various positions, and was full professor until Since 2002 he is teaching at the University of Toronto and Ryerson University, Toronto. He has also lectured on specialized subjects related to energy, thermodynamics, physics, fluid mechanics, design of power plants and hydraulic transient analysis (waterhammer, vibrations, hydraulic vibrations, stability, resonance in technical systems and human blood vessels) as the visiting Professor at the University of Singapore, Hong Kong, Sarajevo and Skoplje, Nis, to name a few. He specializes in design, construction, commissioning, maintenance, troubleshooting and review of electric plants, hydraulic systems, pumps and turbines as well as the complex systems of thermal and nuclear plants. He has designed 27 power plants, 3 test rigs, a number of pumped storage plants and pumping systems; successfully completed hydraulic transient and vibration analysis for 31 large hydraulic machines and systems; developed model acceptance tests of 11 rotating (turbo) machines, field tests of 12, and acceptance tests of 7 power plants an has led numerous final field tests as Chief Engineer. He published 20 textbooks and monographs, as well as over 140 technical papers. He is the author of several books on vibrations, hydraulic transients, and a co-author of: The Guide to Hydropower Mechanical Design, prepared by ASME Hydro Power Technical Committee, 1996 (new edition is under review), as well as Guidelines to Hydraulic Transient Analysis, 1992; and He has acted as consulting engineer on design, construction, on-site and model tests of power plants and computer simulation of transient and hydraulic vibration of many systems. At Energoprojekt, Belgrade, he designed and tested the highest, at the time, (600 m) head Pumped-Storage Power Plant Bajina Basta, and a number of other electric power plants and pumping systems; designed the second phase for four small plants Vlasina having five units rated at 13 to 16 MW and the pump plant Lisina pumping into Vlasina storage. He has been involved in

8 8 troubleshooting in US, Canada, and Iran, and is a is licensed Professional Engineer in the Province of Ontario Tihomir Maricic graduated in Mechanical Engineering from University of Nis, Yugoslavia, in After the graduation he joined the crew of the builders of Iron Gates 2 Hydroelectric Development Project. For more than 10 years, through the variety of positions he has gained substantial and wide experience in hydro equipment design, manufacturing and installation. After moving to Canada, he has used this experience in international and domestic hydro projects as a design engineer, consultant and project engineer for service and rehabilitation Tim has joined Ontario Power Generation as a Senior Plant Engineer with Asset Management Department of Niagara Plant Group Tihomir (Tim) Maricic is licensed Professional Engineer in the Province of Ontario. Don Haber is a licensed Professional Engineer in the Province of Ontario, Canada and has 29 years of experience with Ontario Power Generation and its predecessor company, Ontario Hydro. He has held various operating, maintenance and technical roles in the organization. He is currently the Technical Support Manager in the Niagara Plant Group responsible for engineering issues in OPGs hydroelectric generating stations in Niagara Falls and surrounding area. Don may be reached at (905)