HYDROPOWER IN NORWAY Mechanical Equipment A survey prepared by Arne Kjølle Professor Emeritus Norwegian University of Science and Technology Trondheim, December 2001 I CONTENTS Preface Page VIII CHAPTER 1 Hydropower Machinery Page Introduction 1.1 1.1 Brief review of hydropower machines 1.2 1.1.1 The eldest hydropower machines 1.2 1.1.2 Turbines 1.3 1.2 Arrangement of hydropower plants 1.5 References 1.7 CHAPTER 2 Energy Conversion Page Introduction 2.1 2.1 Fundamentals and definitions 2.1 2.2 Transforming hydraulic energy into mechanical energy 2.2 2.2.1 General considerations 2.2 2.2.2 Impulse turbine - Pelton 2.3 2.2.3 Reaction turbines 2.6 2.2.4 The main equation of turbines 2.12 2.3 A brief outline of the hydraulic design of turbines 2.13 2.4 Efficiency 2.16 References 2.17 Bibliography 2.17 CHAPTER 3 Classification of Turbines - Main Characteristics Page Introduction 3.1 3.1 Fundamental similarity considerations 3.1 3.1.1 Similarity relations 3.1 3.1.2 Speed number 3.3 3.1.3 Classification of turbines 3.4 3.1.4 Performance characteristics 3.5 3.1.5 Cavitation and suction head 3.8 3.2 Pelton turbines 3.9 3.2.1 Main hydraulic dimensions 3.9 3.2.2 Pelton bucket dimensions 3.10 3.2.3 Performance diagram 3.10 3.3 Francis turbines 3.11 3.3.1 Main hydraulic dimensions 3.11 3.3.2 Performance diagrams 3.11 3.3.3 Cavitation, suction head and reaction ratio 3.13 3.4 Kaplan turbines 3.14 3.4.1 Main hydraulic dimensions 3.14 II Classification of turbines - Main Characteristics Page (Cont.) 3.4.2 Performance diagram 3.15 3.4.3 Cavitation, suction head and reaction ratio 3.16 3.5 Choice of turbine 3.16 3.5.1 Choice between Pelton and Francis turbines 3.16 3.5.2 Choice between Francis and Kaplan turbines 3.20 References 3.20 Bibliography 3.21 CHAPTER 4 Governing Principles Page Introduction 4.1 4.1 Feedback control system 4.2 4.2 Governor adjustment facilities 4.4 4.2.1 Proporsjonal-integral-derivative funtions (PID) 4.4 4.2.2 Permanent speed droop 4.4 4.3 Turbine governing demands 4.5 4.3.1 Frequency and load regulation 4.5 4.3.2 Start and stop sequence control 4.5 4.3.3 Disconnection, load rejection 4.6 4.3.4 Load limiting 4.6 4.4 Regulation requirements of water power plants 4.6 4.4.1 Mass oscillation 4.6 4.4.2 Water hammer pressure rise versus closure time and speed 4.8 4.5 Governing stability 4.13 4.5.1 Modes of operation 4.13 4.5.2 Rules of thumb 4.14 References 4.15 Bibliography 4.15 CHAPTER 5 Performance Tests Page Introduction 5.1 5.1 Tests on prototype 5.1 5.1.1 Principles for test 5.1 5.1.2 Measurement of the turbine power 5.2 5.1.3 Methods for determination of discharge 5.2 5.1.3.1 Current meter method 5.2 5.1.3.2 Pitot tube gauging 5.3 5.1.3.3 The pressure-time method (Gibson method) 5.4 5.1.3.4 Tracer methods 5.5 5.1.3.5 Ultrasonic method 5.7 5.1.3.6 Weirs 5.9 5.1.3.7 Standardised differential pressure devices 5.10 5.1.3.8 Volumetric gauging method 5.11 5.1.3.9 Relative discharge measurement 5.11 III Performance Tests (Cont.) Page 5.1.4 Thermodynamic measurement of flow losses 5.12 5.1.4.1 Measurement of power losses 5.12 5.1.4.2 Efficiency and specific energies 5.13 5.1.4.3 Measuring technique 5.14 5.1.4.4 Corrections for leakage and friction 5.16 5.1.5 Dynamic properties of the turbines 5.16 5.1.6 Cavitation behaviour of prototype 5.16 5.1.7 Governor test - Rejection tests 5.17 5.2 Model tests and scale effect of effiency from model to prototype 5.17 5.2.1 Laboratory qualifications 5.17 5.2.2 Model tests 5.18 5.2.3 Scale effect on efficiency from model to prototype 5.20 References 5.21 Bibliography 5.22 CHAPTER 6 Page Pelton Turbines Introduction 6.1 6.1 Horizontal Pelton turbine arrangement 6.1 6.2 Vertical Pelton turbine arrangement 6.2 6.3 Main components and their functions 6.4 6.3.1 Runner 6.4 6.2.2 The turbine shaft 6.6 6.2.3 Turbine radial bearing 6.6 6.2.4 Bend and distributor 6.7 6.2.5 Straight flow injector 6.8 6.2.6 Deflector mechanism 6.9 6.2.7 Turbine housing 6.10 6.3 Condition control 6.10 6.3.1 Turbine guide bearing 6.10 6.3.2 Runner 6.11 6.3.3 Main injector with needle servomotor 6.11 6.3.4 Seal ring in deflector bearing 6.11 6.3.5 Filter 6.11 6.4 Monitoring instruments 6.11 6.5 Assembly and dismantling 6.12 Reference 6.12 Bibliography 6.12 CHAPTER 7 Page Francis Turbines Introduction 7.1 7.1 Horizontal Francis turbine 7.1 7.2 Vertical Francis turbine 7.2 7.3 Main components and their functions 7.4 7.3.1 Scroll casing 7.4 IV Francis Turbines (Cont.) Page 7.3.2 Guide vane cascade 7.4 7.3.3 Turbine covers 7.5 7.3.4 Runner 7.5 7.3.5 Turbine shaft and bearing 7.6 7.3.6 Shaft seal 7.7 7.3.7 Regulating mechanism 7.8 7.3.8 Draft tube 7.9 7.4 Drainage and filling system 7.9 7.5 Contition control 7.10 7.6 Monitoring instruments 7.11 7.7 Assembly and dismantling 7.11 References 7.12 Bibliography 7.12 CHAPTER 8 Page Kaplan Turbines Introduction 8.1 8.1 Kaplan turbine construction 8.1 8.1.1 Arrangement 8.1 8.1.2 Kaplan turbine construction 8.2 8.2 Main components and their functions 8.3 8.2.1 Scroll casing 8.3 8.2.2 The guide vane cascade 8.4 8.2.3 Covers 8.4 8.2.4 Runner 8.4 8.2.5 Runner blade servomotor 8.5 8.2.6 Regulating mechanism of the runner blades 8.5 8.2.7 Cooperation of the regulation of the guide vanes and the 8.6 runner blades 8.2.8 Runner chamber 8.6 8.2.9 Turbine shaft 8.7 8.2.10 Turbine bearing 8.7 8.2.11 Shaft seal box 8.7 8.2.12 Draft tube 8.8 8.3 Drainage and filling arrangement 8.9 8.4 Condition control 8.9 8.4.1 Runner 8.9 8.4.2 Runner chamber 8.9 8.4.3 Guide vane mechanism 8.9 8.4.4 Shaft seal box 8.9 8.5 Monitoring instruments 8.9 8.6 Assembly and dismantling 8.10 References 8.10 Bibliography 8.10 V CHAPTER 9 Page Bulb Turbines Introduction 9.1 9.1 General arrangement 9.1 9.2 Main components 9.1 9.2.1 Stay cone 9.2 9.2.2 Runner chamber and draft tube cone 9.2 9.2.3 Generator hatch 9.3 9.2.4 Stay shield 9.3 9.2.5 Rotating parts 9.3 9.2.5.1 The runner 9.4 9.2.5.2 The turbine shaft 9.4 9.2.6 Shaft seal box 9.4 9.2.7 Turbine shaft bearing 9.6 9.2.8 The feedback mechanism and oil piping 9.7 9.2.8.1 The oil transfer unit 9.7 9.2.9 The guide vane mechanism 9.7 9.3 Condition control 9.8 9.3.1 Runner 9.9 9.3.2 Runner chamber 9.9 9.3.3 Guide vane mechanism 9.9 9.3.4 Shaft seal box 9.9 9.3.5 Generally for Bulb turbines 9.9 9.4 Monitoring instruments 9.9 9.5 Assembly and dismantling 9.10 References 9.10 Bibliography 9.10 CHAPTER 10 Page Governors 10.1 Governor system structure 10.1 10.2 Electrohydraulic controllers 10.2 10.2.1 Analogous controller 10.2 10.2.2 Digital computer based controller 10.3 10.3 Servo system 10.4 10.3.1 Governor desk 10.4 10.3.2 Main control servomoter 10.6 10.4 Specific turbine governing equipement 10.6 10.4.1 Dual control of Pelton turbines 10.6 10.4.2 By-pass control for Francis turbines 10.7 10.4.2.1 Function and general arrangement 10.7 10.4.2.2 The valve control system 10.8 10.4.3 Dual control of Kaplan/Bulb turbines 10.9 References 10.10 Bibliography 10.10 VI CHAPTER 11 Page Valves Introduction 11.1 11.1 Spherical valves 11.1 11.1.1 Valve housing and valve rotor 11.1 11.1.2 Valve rotor trunnions and bearings 11.2 11.1.3 Seals for closed valve 11.2 11.1.3.1 Main seal 11.3 11.1.3.2 Auxilliary seal 11.4 11.1.4 Operation mechanism 11.4 11.1.5 Control system 11.5 11.2 Butterfly valves 11.6 11.2.1 Valve housing 11.6 11.2.2 Valve disc 11.6 11.2.3 Bearing 11.7 11.2.4 Seal 11.7 11.2.5 Operating mechanism 11.8 11.3 Gate valves 11.8 11.5 Ring valves 11.9 11.6 The bypass valve 11.10 11.7 Guidelines for inspection of valves 11.11 References 11.12 Bibliography 11.12 CHAPTER 12 Page Auxilliary Equipment Introduction 12.1 12.1 Oil pressure system 12.1 12.1.1 System construction 12.2 12.1.2 System operation 12.7 12.2 Air supply system 12.8 References 12.10 CHAPTER 13 Page Forces transferred to the foundations Introduction 13.1 13.1 Horizontal turbines 13.1 13.2 Vertical turbines 13.2 References 13.4 VII CHAPTER 14 Page Causes to damages Introduction 14.1 14.1 Cavitation 14.1 14.2 Sand erosion 14.2 14.3 Material defects 14.3 14.4 Fatigue 14.5 References 14.6 CHAPTER 15 Page Condition Control Introduction 15.1 15.1 Activities for Pelton turbine 15.1 15.2 Activities for Francis turbines 15.2 15.3 Activities for Kaplan and Bulb turbines 15.3 References 15.4 CHAPTER 16 Page Quality Assurance (QA) Quality assurance 16.1 References 16.3 VIII Preface This book was originally aimed to constitute a section called Mechanical Equipment, in a series of books that in total describe the THE DEVELOPMENT OF HYDRO POWER IN NORWAY. In fact much of the literary work during the preparation of this book, was however, evaluated to be a more suitable presentation of the material for a textbook than for the above mentioned series of books. Therefore it was preferred to edit this book separatly with the intention that it may partly serve as a supplementary textbook for students on hydro power machinery. The subjects being mentioned comprise all main components of a hydro power plant from the upstream end with the basin for water intake to the downstream end of the water flow outlet. Those parts of the plant which are not specifically of the mechanical equipment category, are simply mentioned to inform about their function and position in the system structure. For the the mechanical equipment it is given basic theory for the hydraulic design of turbines, theory and description of methods for tests of models and prototypes of turbines, theory for the dynamics in water conduits and governing of turbines. Further descriptions are given of the design structure of all actual turbines, valves, governors and auxilliary equipment. In addition a touch on forces transferred to the foundations, causes to damages on the machines, condition control and quality assurance is given. The preparation of this book has been effected through comparisons and reflections on the material in the references, which are listet at the end of each chapter. However, my colleague Professor Dr.techn. Hermod Brekke, has earlier prepared a manuscript of a book which is containing much of the same subjects as in this case. With allowance from him, I have adopted from his manus quite a lot of the material about the design of the modern turbines and turbine governing. For this important support, I thank Professor Brekke. For the skillful scanning in of the figures, I thank head clerk Rundi Aukan. Trondheim, December 2001 Arne Kjølle Hydropower Machinery 1.1 CHAPTER 1 Hydropower Machinery Introduction Hydropower machine is the designation used for a machine that directly convert the hydraulic power in a water fall to mechanical power on the machine shaft. This power conversion involves losses that arise partly in the machine itself and partly in the water conduits to and from the machine. The utilization of the power in the waterfall is evaluated by the so-called power plant efficency η , a which is the ratio between the mechanical power output from the machine shaft and the gross hydraulic power of the power plant. The plant efficiency η is a variabel quantity that depends on a the design of the water conduits to and from the hydropower machine and the operating conditions. The conduits are normally made with flow cross sections according to optimal design criteria. In practise that means conduit cross section areas are as small as possible to get low investment costs. However, the smaller the cross sections are, the higher the losses become. Similar consequenzies are resulting from increasing lengths of the conduits. Both these effects means a correspondingly lower plant efficiency η . a The hydropower machine may be operated with different flow rates Q from time to time according to the variable grid load, the alternating heads and flow discharges in the plant. These circumstances means that the hydropower machines necessarily are equipped with facilities for regulation of the power input and output. In practise this is carried out by regulation of the flow discharge. The input power to the hydropower machine is however, not efficiently similar utilized at all operating conditions. The fact is that the machine performs the optimal efficiency for only one single combination of flow discharge, water head and rotational speed. This means a characteristic, which is denoted as the efficiency of the machine and generally expressed by mechanical output power η= (1.1) net input power where net input power means the gross hydraulic power of the power plant minus power losses in the conduits to and from the hydropower machine. According to the regulation means another quantity is defined as the admission κ and expressed as operating discharge κ= (1.2) discharge at max. efficiency