3B2 E2.5 C2 Review
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Questions and Answers

What determines the complexity of a turbine's lubrication system?

  • The type of driven machine
  • The type of governor mechanism
  • The type of oil used
  • The size of the turbine (correct)

    • What is the primary function of the oil cooler in a lube oil system?

  • To filter the oil
  • To increase oil pressure
  • To cool the oil (correct)
  • To reduce oil pressure

    • In a small turbine, what type of bearings are typically used?

  • Gear-driven bearings
  • Circulating oil bearings
  • Ring-oiled bearings (correct)
  • Hydraulic bearings

    • What is the purpose of the header in a lube oil system?

    <p>To distribute oil to various parts</p> Signup and view all the answers

    What is the typical pressure range of oil supplied to the bearings and other parts in a lube oil system?

    <p>55 to 103 kPa</p> Signup and view all the answers

    Where does the oil drain back into after passing through the bearings and governor mechanism?

    <p>The reservoir</p> Signup and view all the answers

    What is the primary purpose of oil coolers in a turbine-generator set?

    <p>To cool the oil before it flows through the bearings and prevent increased viscosity</p> Signup and view all the answers

    What is the function of the small fan shown in Figure 1?

    <p>To draw off water vapor from the oil tank and improve evaporation</p> Signup and view all the answers

    Which pump is the main source of lube oil when the turbine is running?

    <p>The main oil pump directly driven by gears from the turbine shaft</p> Signup and view all the answers

    What is the range of typical outlet temperature from the oil coolers?

    <p>43° to 49°C</p> Signup and view all the answers

    What is the purpose of the pressure-reducing valve in the lubrication system?

    <p>To provide the oil at a lower pressure for the lubrication system</p> Signup and view all the answers

    What is the primary purpose of the vapor extractor?

    <p>To draw off water vapor from the oil tank and improve evaporation</p> Signup and view all the answers

    What is a common characteristic of lubrication systems in small turbines?

    <p>They have a simple lubrication system</p> Signup and view all the answers

    What is the primary function of the header in Figure 1?

    <p>To supply oil to the governing and control mechanisms</p> Signup and view all the answers

    Which part of the turbine-generator set receives hydraulic operating oil?

    <p>The governor mechanisms and steam throttle valves</p> Signup and view all the answers

    What is the typical range of pressure at which oil is supplied to the governing and control mechanisms?

    <p>350 to 500 kPa</p> Signup and view all the answers

    What determines the type of lubrication system used in a turbine?

    <p>The size of the turbine</p> Signup and view all the answers

    Which components receive oil from the second header in Figure 1?

    <p>The bearings and governor mechanism</p> Signup and view all the answers

    What is the primary reason for not cooling the lube oil below 43° to 49°C?

    <p>To prevent an increase in viscosity and affected flow</p> Signup and view all the answers

    What is the function of the two standby pumps driven by electric motors?

    <p>To act as a backup during main pump failure or startup/shutdown</p> Signup and view all the answers

    What is the purpose of the return header in the lube oil system?

    <p>To return cooled oil to the oil tank</p> Signup and view all the answers

    How does the centrifuge purify the oil?

    <p>Through high speed rotation, separating water from oil</p> Signup and view all the answers

    What is the main purpose of the thermometer in the return oil line?

    <p>To monitor the temperature of the bearings</p> Signup and view all the answers

    What is the primary function of the small stream of oil drawn from the bottom of the oil tank?

    <p>To purify the oil through a purifier filter</p> Signup and view all the answers

    What does the jacking oil pump specifically do in a large turbine system?

    <p>Supplies oil to lift the turbine shaft during start-up</p> Signup and view all the answers

    Why is it important to apply jacking oil before start-up of the barring gear in a turbine?

    <p>To prevent metal-to-metal contact during initial start-up</p> Signup and view all the answers

    Where is the location of the barring gear in relation to the turbine shaft in a large turbine?

    <p>At the side of the bearing below the turbine center line</p> Signup and view all the answers

    How does the jacking oil system contribute to reducing the starting load on the electric motor?

    <p>By lifting the shaft and reducing metal-to-metal contact</p> Signup and view all the answers

    When is the jacking oil pump typically shut down in relation to the barring gear in a turbine system?

    <p>When the barring gear disengages</p> Signup and view all the answers

    What purpose does the side-mounted barring gear serve in a large turbine?

    <p>To engage the shaft below the turbine center line</p> Signup and view all the answers

    What happens to the rotor of a turbine when it is left cold and at a standstill?

    <p>It bends slightly downwards between the support bearings</p> Signup and view all the answers

    What is the purpose of the barring gear in a turbine?

    <p>To ensure even warming and avoid startup vibration</p> Signup and view all the answers

    Why is it important to keep a hydrogen cooled generator on barring gear while shut down?

    <p>To prevent excessive loss of hydrogen</p> Signup and view all the answers

    What happens to the lower half of the rotor when a turbine is left at a standstill while it is still hot?

    <p>It cools faster than the upper half</p> Signup and view all the answers

    What is the typical speed of the barring gear in a turbine?

    <p>Around 1% of operating speed</p> Signup and view all the answers

    How long should a turbine be kept on barring gear after shutdown to ensure even cooling?

    <p>Up to 24 hours</p> Signup and view all the answers

    What is the primary cause of the 'hogging' phenomenon in a turbine rotor?

    <p>The rotor cooling at an uneven rate due to the lower half cooling faster than the upper half</p> Signup and view all the answers

    What is the main purpose of the disengaging gear wheel in the barring gear illustrated in Figure 3?

    <p>To disconnect the motor from the turbine shaft</p> Signup and view all the answers

    Why is it necessary to ensure even warming of a cold turbine before starting it?

    <p>To avoid startup vibration</p> Signup and view all the answers

    What is the primary function of the barring gear when a turbine is shut down?

    <p>To ensure the rotor and casing cool evenly</p> Signup and view all the answers

    Why is it necessary to keep a hydrogen cooled generator on barring gear while shut down?

    <p>To prevent excessive loss of hydrogen</p> Signup and view all the answers

    What is the primary reason for not cooling the lube oil below 43° to 49°C?

    <p>To maintain the viscosity of the oil</p> Signup and view all the answers

    What is the primary function of the jacking oil system in relation to the initial start-up of the barring gear?

    <p>To lift the shaft and provide lubricating oil, preventing metal-to-metal contact</p> Signup and view all the answers

    Which of the following accurately describes the mounting position of the barring gear for a large turbine?

    <p>Mounted at the side of the bearing, engaging the shaft below the turbine center line</p> Signup and view all the answers

    What is the main purpose of the typical pressure range of around 10,000 kPa applied by the jacking oil pump to the lower part of the bearings?

    <p>To lift the shaft and provide lubrication, preventing metal-to-metal contact</p> Signup and view all the answers

    What occurs when the turbine is left at a standstill while still hot, and how does this relate to the use of the barring gear?

    <p>The rotor expands unevenly, and the barring gear is used to manually turn the shaft during cooling</p> Signup and view all the answers

    Why is it crucial to keep a hydrogen-cooled generator on barring gear while shut down?

    <p>To prevent the generator's core from shifting during cool-down</p> Signup and view all the answers

    What is the primary purpose of using the side-mounted barring gear in a large turbine?

    <p>To engage the shaft below the turbine center line</p> Signup and view all the answers

    What is the primary purpose of the steam in a power plant?

    <p>To supply the turbine with heat energy to produce mechanical power</p> Signup and view all the answers

    What happens to the main steam after expanding in the high-pressure turbine?

    <p>It is sent to the reheater section of the boiler</p> Signup and view all the answers

    What is the purpose of the low-pressure feed heaters?

    <p>To heat the feedwater going to the boiler</p> Signup and view all the answers

    What is the purpose of the deaerator?

    <p>To remove air from the feedwater</p> Signup and view all the answers

    What is the purpose of the economizer?

    <p>To further heat the feedwater going to the boiler</p> Signup and view all the answers

    What happens to the exhaust steam in the surface condenser?

    <p>It is condensed</p> Signup and view all the answers

    What is the main source of heat energy in a nuclear plant steam power cycle?

    <p>The reaction of a nuclear fuel</p> Signup and view all the answers

    What is the working fluid in the steam power cycle of a nuclear plant?

    <p>The steam flowing through the turbine</p> Signup and view all the answers

    What is the purpose of the condenser in a steam power plant?

    <p>To convert steam to water</p> Signup and view all the answers

    What is the role of the heat exchanger in a nuclear plant?

    <p>To transfer heat from the reactor coolant to the working fluid</p> Signup and view all the answers

    What is the exhaust pressure of the steam in a condensing steam plant?

    <p>Well below atmospheric pressure</p> Signup and view all the answers

    What collects in the bottom, hotwell section of the condenser?

    <p>The condensate</p> Signup and view all the answers

    In a nuclear plant, what transfers the heat produced by the nuclear reaction to the heat exchanger?

    <p>The circulating reactor coolant</p> Signup and view all the answers

    What determines the exhaust pressure in a condensing steam plant?

    <p>The amount of cooling in the condenser</p> Signup and view all the answers

    What is the working fluid in the steam power cycle of a nuclear plant?

    <p>Steam flowing through the turbine</p> Signup and view all the answers

    What collects in the bottom, hotwell section of the condenser in a simple steam power plant?

    <p>Condensate</p> Signup and view all the answers

    What is the main purpose of the heat exchanger in a nuclear plant?

    <p>To transfer the heat produced by the nuclear reaction to the working fluid in the cycle</p> Signup and view all the answers

    What is the main source of heat energy in a nuclear plant steam power cycle?

    <p>Heat energy produced by the reaction of a nuclear fuel</p> Signup and view all the answers

    What happens to the steam after it leaves the reheater section and expands in the low-pressure turbine?

    <p>It enters the surface condenser and heat exchange with the circulating cooling water removes the latent heat, causing the steam to condense.</p> Signup and view all the answers

    What is the purpose of the deaerator in a steam power plant?

    <p>To remove dissolved gases from the condensate before it enters the boiler.</p> Signup and view all the answers

    What is the primary function of the flue gases in the economizer?

    <p>To preheat the feedwater going to the boiler.</p> Signup and view all the answers

    What is the purpose of the low-pressure feed heaters in a steam power plant?

    <p>To preheat the feedwater using heat from the exhaust or extraction steam from the HP turbine.</p> Signup and view all the answers

    What is the role of the high-pressure feed heaters in a steam power plant?

    <p>To preheat the feedwater using heat from the exhaust or extraction steam from the HP turbine.</p> Signup and view all the answers

    What is the function of the condenser in a steam power plant?

    <p>To provide a low-pressure sink for the exhaust steam, allowing it to condense and be pumped back to the boiler.</p> Signup and view all the answers

    What do steam turbine governors control?

    <p>Steam flow</p> Signup and view all the answers

    In an extraction turbine, the governor controls the steam flow to keep which two parameters reasonably constant?

    <p>Turbine speed and pressure at extraction point</p> Signup and view all the answers

    Which method is specifically used in impulse turbines to maintain a set turbine speed?

    <p>Nozzle governing</p> Signup and view all the answers

    What is the primary function of nozzle governing in steam turbines?

    <p>Directing steam to inlet nozzles</p> Signup and view all the answers

    What is the purpose of backpressure control in a backpressure steam turbine?

    <p>Maintain constant backpressure</p> Signup and view all the answers

    Which parameter do turbine governors fall into two classes based on being responsive to?

    <p>Speed or pressure changes</p> Signup and view all the answers

    What is the primary function of a pressure sensitive governor for a backpressure turbine?

    <p>Controlling the turbine exhaust pressure</p> Signup and view all the answers

    In extraction governing, what happens when the extraction steam demand increases?

    <p>More steam is admitted through the extraction valve</p> Signup and view all the answers

    What is the primary advantage of an isochronous governor over other governors?

    <p>It maintains constant speed regardless of load</p> Signup and view all the answers

    What is the change in speed that results from an increase in load on a turbine?

    <p>Speed droop</p> Signup and view all the answers

    In extraction governing, how does the system respond when the load on the turbine increases?

    <p>More steam flows through the extraction valve</p> Signup and view all the answers

    What is the name given to the difference in speed between no-load and full-load operation of a turbine?

    <p>Speed droop</p> Signup and view all the answers

    What characteristic makes governors with low droop more preferable than those with high droop?

    <p>Better sensitivity to load changes</p> Signup and view all the answers

    Which type of governing adjusts the position of the inlet steam throttle valve based on the exhaust steam pressure?

    <p>Backpressure governing</p> Signup and view all the answers

    What forces the pressure regulator piston downwards when the extraction steam demand increases in a turbine?

    <p>Decreased extraction pressure</p> Signup and view all the answers

    What determines the speed droop of a turbine's governor?

    <p>No-load speed change</p> Signup and view all the answers

    What is the purpose of the nozzle valves in the bar-lift system?

    <p>To regulate the sequence of nozzle openings</p> Signup and view all the answers

    What is the difference between throttle governing and bypass or overload governing?

    <p>Throttle governing controls the steam flow into the turbine, while bypass governing allows extra power during high load conditions</p> Signup and view all the answers

    What determines the sequence of nozzle openings in the cam-lift system?

    <p>The length of the valve stems</p> Signup and view all the answers

    What is the purpose of the servo motor in Figure 12?

    <p>To apply more force to the valve rod</p> Signup and view all the answers

    What happens to the flyweights when the turbine speed increases?

    <p>They move outward due to increased centrifugal force</p> Signup and view all the answers

    What is the advantage of using a servo motor in throttle governing?

    <p>It makes the governor's action smoother</p> Signup and view all the answers

    What is the purpose of the speed changer (speeder gear) shown in Figure 12?

    <p>To adjust the turbine's speed within a certain range</p> Signup and view all the answers

    What is the limitation of mechanical governors?

    <p>They do not maintain a constant speed except between maximum and minimum values</p> Signup and view all the answers

    What is the purpose of the bypass throttle valve in bypass or overload governing?

    <p>To allow extra power during high load conditions</p> Signup and view all the answers

    What is the primary role of steam turbine governors?

    <p>Controlling the flow of steam to regulate turbine speed</p> Signup and view all the answers

    In which type of turbine is nozzle governing typically utilized?

    <p>Impulse turbine</p> Signup and view all the answers

    Which method of speed-sensitive governing is employed in backpressure turbines?

    <p>Bypass or overload governing</p> Signup and view all the answers

    What does the governor of an extraction turbine aim to keep constant?

    <p>Steam flow and extracted steam pressure</p> Signup and view all the answers

    How many classes of turbine governors are mentioned in the text based on their responsivity?

    <p>Two</p> Signup and view all the answers

    What is the purpose of nozzle governing in steam turbines?

    <p>Controlling the flow of steam to inlet nozzles</p> Signup and view all the answers

    What is the primary function of the nozzle valves in the bar-lift system?

    <p>To control the sequence of nozzle openings</p> Signup and view all the answers

    What is the main advantage of using servo motors in throttle governing?

    <p>They provide a smoother action and apply more force to the valve rod</p> Signup and view all the answers

    What is the purpose of the second inlet point in bypass governing?

    <p>To allow for overload conditions</p> Signup and view all the answers

    What type of turbines always use throttle governing?

    <p>Reaction turbines</p> Signup and view all the answers

    What movement does the governor rod undergo when the turbine speed increases?

    <p>It moves in and out</p> Signup and view all the answers

    What determines the sequence of nozzle openings in the bar-lift system?

    <p>The length of the valve stems</p> Signup and view all the answers

    What type of governing does not maintain a constant speed except between a maximum and minimum value, dependent on load?

    <p>Mechanical governing</p> Signup and view all the answers

    What is the purpose of the speed changer in Figure 12?

    <p>To adjust the governed speed</p> Signup and view all the answers

    What movement occurs in the flyweights when the turbine speed decreases?

    <p>They move in due to reduced centrifugal force</p> Signup and view all the answers

    What is the primary function of the linkage system in throttle governing?

    <p>To adjust the position of the throttling valve</p> Signup and view all the answers

    What is the primary purpose of pressure sensitive governors in turbines?

    <p>To maintain a steady backpressure at the turbine exhaust</p> Signup and view all the answers

    What is the advantage of backpressure governed turbines?

    <p>No exhaust steam losses</p> Signup and view all the answers

    What happens when the load on a turbine increases in an extraction governed turbine?

    <p>More high-pressure steam is admitted to the turbine</p> Signup and view all the answers

    What is the term for the change in speed that results from an increase in load?

    <p>Speed droop</p> Signup and view all the answers

    What is the purpose of an isochronous governor?

    <p>To maintain a constant speed regardless of load</p> Signup and view all the answers

    What is the disadvantage of backpressure governing?

    <p>Dependence on process steam demand</p> Signup and view all the answers

    What happens to the extraction valve when the extraction steam demand increases in an extraction governed turbine?

    <p>It closes further</p> Signup and view all the answers

    What is the purpose of the pressure regulator piston in an extraction governed turbine?

    <p>To control the extraction pressure</p> Signup and view all the answers

    What is the term for the difference between the no-load and full-load speed of a turbine, expressed as a percentage of the set speed?

    <p>Speed droop</p> Signup and view all the answers

    What type of governing adjusts the position of the inlet steam throttle valve based on the exhaust steam pressure?

    <p>Backpressure governing</p> Signup and view all the answers

    What type of controller is the speed governor mentioned in the text?

    <p>Proportional-action</p> Signup and view all the answers

    What is the term used in the text to refer to the loss in speed of the generator due to increased load?

    <p>Speed droop</p> Signup and view all the answers

    Which of the following is not a type of speed sensitive governor mentioned in the text?

    <p>Hydraulic-electric</p> Signup and view all the answers

    What are the components attached to the turbine shaft called in the mechanical governor described?

    <p>Flyweights</p> Signup and view all the answers

    In a mechanical governor, what are the ends of the flyweights connected to?

    <p>Governor</p> Signup and view all the answers

    What part is mounted at the inlet of the turbine in the mechanical governor described in the text?

    <p>Governor valve</p> Signup and view all the answers

    What causes the flyweights to pivot outwards in a mechanical governor?

    <p>Centrifugal force</p> Signup and view all the answers

    How does the governor rod move in a mechanical governor?

    <p>Flyweight extension</p> Signup and view all the answers

    In a mechanical-hydraulic governor, what is used to move the governor valve?

    <p>Pilot valve</p> Signup and view all the answers

    How does the mechanical-hydraulic governor reduce mechanical losses?

    <p>By reducing force needed to position the pilot valve</p> Signup and view all the answers

    What is one disadvantage of simple mechanical governors mentioned in the text?

    <p>High-speed droop</p> Signup and view all the answers

    What is the purpose of the counterspring in the mechanical governor?

    <p>To balance the flyweights</p> Signup and view all the answers

    Which component determines the steam valve position in the mechanical-hydraulic governor?

    <p>Hydraulic piston</p> Signup and view all the answers

    How does changing the pivot point at the fulcrum affect the mechanical governor?

    <p>Affects governor rod movement</p> Signup and view all the answers

    What is the primary role of the oil relay in the mechanical-hydraulic governor system?

    <p>Assisting pilot valve operation</p> Signup and view all the answers

    What effect does increasing turbine load have on the governors in the mechanical-hydraulic system?

    <p>Forces steam valve to close further</p> Signup and view all the answers

    What directly regulates the oil pressure below the throttle valve cylinder to increase pressure if the speed is high?

    <p>Pilot valve</p> Signup and view all the answers

    In the Mechanical-Hydraulic Governor System, what causes the speed of the turbine to change by affecting the pressure to cylinder “H”?

    <p>Handwheel 'L'</p> Signup and view all the answers

    What is mainly responsible for moving the steam valves and controlling the steam flow in the Electro-Hydraulic Governor System?

    <p>Servo-rams</p> Signup and view all the answers

    Which component is held open by the pressure under the operating piston in cylinder 'C'?

    <p>Turbine stop valve</p> Signup and view all the answers

    In the Mechanical-Hydraulic Governor System, what specifically causes all oil pressure to be lost, leading to the turbine's immediate stop?

    <p>Overspeed trip assembly</p> Signup and view all the answers

    What provides oil pressure during the start-up of the turbine until the main oil pump can provide sufficient operating oil pressure?

    <p>Auxiliary oil pump</p> Signup and view all the answers

    Which part determines the opening of the oil ports in the servo by controlling the position of the plunger sliding within sleeve 'G'?

    <p>Flyweights</p> Signup and view all the answers

    What affects the droop, proportionality, and speed control of the governor based on its positioning?

    <p>Piston in cylinder 'H'</p> Signup and view all the answers

    In an Electro-Hydraulic Governor System, what specifically amplifies and applies the difference between the electrical output signal and the reference signal?

    <p>Computer</p> Signup and view all the answers

    What is responsible for providing high-pressure hydraulic oil to operate the servo-rams in Electro-Hydraulic Governor Systems?

    <p>Fluid power unit</p> Signup and view all the answers

    What movement in the turbine speed causes the speed governor to control the opening of control valves?

    <p>Increase in load</p> Signup and view all the answers

    In a mechanical governor system, what allows movement in the governor rod to be transmitted to the valve stem?

    <p>Fulcrum</p> Signup and view all the answers

    What governor system may result in non-constant frequency over the full range of load without external adjustment when driving an electric generator?

    <p>Mechanical</p> Signup and view all the answers

    What is the purpose of the counterspring in a mechanical governor system?

    <p>To act upon the governor to balance the movement of flyweights</p> Signup and view all the answers

    What adjustment is required to maintain a constant frequency over the full range of load when using a speed sensitive governor for an electric generator?

    <p>External adjustment</p> Signup and view all the answers

    What is the function of the governor valve in a mechanical governor system?

    <p>To control steam inlet to the turbine</p> Signup and view all the answers

    What causes the flyweights to move outwards in a mechanical governor?

    <p>Increased centrifugal force</p> Signup and view all the answers

    How does the movement of the flyweights impact the governor rod in a mechanical governor?

    <p>It causes the governor rod to move to the left</p> Signup and view all the answers

    Why are simple mechanical governors not suitable for large machines or where control must be extremely accurate?

    <p>They have a droop around 10%</p> Signup and view all the answers

    What is the primary advantage of a mechanical-hydraulic governor over a simple mechanical governor?

    <p>Reduced mechanical losses</p> Signup and view all the answers

    How is the droop of a mechanical-hydraulic governor typically compared to that of a simple mechanical governor?

    <p>Lower</p> Signup and view all the answers

    In a mechanical-hydraulic governor, what positions the oil pilot valve to move the governor valve?

    <p>Flyweights</p> Signup and view all the answers

    What effect does turbine load increase have on the movement of the pilot valve in a mechanical-hydraulic governor?

    <p>Moves the pilot valve upwards</p> Signup and view all the answers

    What component controls the positioning of the steam valve in a mechanical-hydraulic governor?

    <p>Servo piston</p> Signup and view all the answers

    What is a feature of the hydraulic cylinder and piston in a mechanical-hydraulic governor?

    <p>It directly links to the governor valve</p> Signup and view all the answers

    What action causes the steam valve to open further in a mechanical-hydraulic governor?

    <p>Turbine load decrease</p> Signup and view all the answers

    What happens to the turbine during an overspeed situation?

    <p>The turbine stops immediately due to loss of oil pressure beneath the throttle valve.</p> Signup and view all the answers

    What controls the opening of the oil ports in the servo of the mechanical-hydraulic governor system?

    <p>Relative position of the plunger and sleeve</p> Signup and view all the answers

    In an Electro-Hydraulic Governor System, what provides the electrical output signal that is amplified and compared to a reference signal?

    <p>Permanent magnet generator</p> Signup and view all the answers

    What is the function of the servo-valve in an Electro-Hydraulic Governor System?

    <p>Positions the servo-rams</p> Signup and view all the answers

    How is the speed of the turbine changed in a mechanical-hydraulic governor system by adjusting handwheel 'L'?

    <p>By changing the servo-ports openings</p> Signup and view all the answers

    What determines the position of the throttle valve in the mechanical-hydraulic governor system?

    <p>Pilot valve</p> Signup and view all the answers

    What provides oil pressure during start-up of the turbine in the mechanical-hydraulic governor system until the main oil pump can supply sufficient operating oil pressure?

    <p>Auxiliary oil pump driven by electric motor</p> Signup and view all the answers

    In a mechanical-hydraulic governor, what is the primary function of the spinning flyweights?

    <p>To balance the counterspring</p> Signup and view all the answers

    What component regulates the oil pressure below the throttle valve cylinder and increases pressure if the speed is high in the mechanical-hydraulic governor system?

    <p>Pilot valve</p> Signup and view all the answers

    What type of controls are used in an electro-hydraulic governor system?

    <p>Electronic and hydraulic controls</p> Signup and view all the answers

    What is the primary function of the mechanical overspeed trip system on a steam turbine?

    <p>To prevent steam from entering the turbine if the speed becomes excessively high</p> Signup and view all the answers

    What happens to the trip bolt during normal operating conditions?

    <p>It is held inside the shaft by a spring in compression</p> Signup and view all the answers

    What is the typical percentage above normal operating speed at which the trip speed is set?

    <p>10 to 12%</p> Signup and view all the answers

    What happens to the spring compression during an overspeed situation?

    <p>It is overcome</p> Signup and view all the answers

    What is the purpose of the trip valve arm in Figure 24?

    <p>To pivot at one end and connect to the casing by the trip valve spring</p> Signup and view all the answers

    What is the function of the mechanical linkage in Figure 24?

    <p>To operate the steam inlet trip valve</p> Signup and view all the answers

    What causes the trip valve to close during an overspeed condition in a turbine with a hydraulic governor system?

    <p>Hydraulic oil pressure in the stop valve cylinder</p> Signup and view all the answers

    What triggers the trip block to shut off the supply of hydraulic oil to the stop valve in an electronic overspeed trip system for turbines?

    <p>Action initiated by reaching the overspeed set point</p> Signup and view all the answers

    What redirects the oil outlet port to the drain in a bolt-type overspeed trip when the turbine speed exceeds the set point?

    <p>Relay rod unlatching</p> Signup and view all the answers

    In an electronic overspeed trip system, why are multiple magnetic sensors used in conjunction to determine the trip speed?

    <p>To minimize the occurrence of nuisance trips</p> Signup and view all the answers

    In a bolt-type mechanical overspeed trip system, what initiates the tripped position of the relay rod?

    <p>Trip bolt striking the tripping lever</p> Signup and view all the answers

    Which component in a hydraulic governor system is slightly off the center of the turbine shaft in preparation for an overspeed trip?

    <p>Nut at the end of the trip bolt</p> Signup and view all the answers

    What is the function of the piston 'B' in the overspeed trip system of a turbine with a hydraulic governor?

    <p>To close off the high-pressure oil inlet port</p> Signup and view all the answers

    What causes the main spring to move the relay rod to the tripped position in a mechanical overspeed trip?

    <p>The trip bolt striking the tripping lever</p> Signup and view all the answers

    In an electronic overspeed trip system for turbines, besides monitoring speed, what is another function of the Electronic Control Module (ECM)?

    <p>Shutting off the supply of oil to the stop valve</p> Signup and view all the answers

    What initiates the closing of the steam inlet control valve in an electronic overspeed trip system for turbines?

    <p>An action from the Electronic Control Module (ECM)</p> Signup and view all the answers

    What is the primary function of the mechanical linkage in Figure 24?

    <p>To provide a path for the steam inlet trip valve to close during overspeed conditions</p> Signup and view all the answers

    What happens to the turbine shaft when the trip bolt is thrown out by centrifugal force in an overspeed condition?

    <p>The shaft continues to rotate, but experiences an increase in rotational inertia</p> Signup and view all the answers

    What is the purpose of the trip latch in Figure 24?

    <p>To raise the trip valve to the open position during normal operation</p> Signup and view all the answers

    What is the significance of the spring's compression in the basic trip bolt mechanism described in the text?

    <p>To apply force to the bolt during normal operation and overcome centrifugal force</p> Signup and view all the answers

    How does the casing contribute to the operation of the mechanical overspeed trip system in Figure 24?

    <p>By acting as a fulcrum for the trip valve arm</p> Signup and view all the answers

    What is the role of the trip valve spring in the mechanical overspeed trip system described in the text?

    <p>To exert tension on the trip valve arm, keeping it tightly against the trip latch</p> Signup and view all the answers

    In Figure 24, what causes the trip valve to close?

    <p>The tension in the spring increases</p> Signup and view all the answers

    In Figure 25, what is the function of piston 'A'?

    <p>To cover the oil drain opening</p> Signup and view all the answers

    What is the purpose of the nut at the end of the bolt in Figure 25?

    <p>To provide a stop for the bolt in the tripped position</p> Signup and view all the answers

    In Figure 26, what happens to the oil outlet port when the turbine speed reaches the overspeed setting?

    <p>It becomes open to the drain</p> Signup and view all the answers

    In an electronic overspeed trip system, what is the purpose of the three magnetic pickups?

    <p>To avoid nuisance trips by requiring at least two sensors to agree on trip speed</p> Signup and view all the answers

    What is the function of the Electronic Control Module (ECM) in an electronic overspeed trip system?

    <p>To convert electronic pulse signals to revolutions per minute</p> Signup and view all the answers

    What happens to the steam valve when the turbine speed reaches the overspeed setting in an electronic overspeed trip system?

    <p>It closes to shut off the supply of steam</p> Signup and view all the answers

    What is the purpose of the trip relay piston in Figure 26?

    <p>To trip the latch, allowing the trip relay spring to pull the piston upwards</p> Signup and view all the answers

    What is the purpose of the spring-loaded trip bolt in Figure 25?

    <p>To overcome the main spring tension at overspeed</p> Signup and view all the answers

    What is an essential step in the starting procedure for a non-condensing turbine with a pressure lubrication system?

    <p>Checking the oil level in the main oil reservoir</p> Signup and view all the answers

    What should be done to ensure there is no condensate in steam and exhaust lines before starting a non-condensing turbine?

    <p>Drain the bypass lines around the traps</p> Signup and view all the answers

    What is a precaution related to the oiler rings that should be checked during the start-up of a non-condensing turbine?

    <p>Verifying that the rings are operating</p> Signup and view all the answers

    When starting a non-condensing turbine, why is it important to check that the governor linkages are well lubricated?

    <p>To ensure proper operation of the turbine governor</p> Signup and view all the answers

    At what point is the throttle valve partially opened when starting a non-condensing turbine?

    <p>To start the turbine rotor turning</p> Signup and view all the answers

    What action should be taken if any unusual noises or problems are detected during the start-up of a non-condensing turbine?

    <p>Close the shutoff valve to the exhaust line</p> Signup and view all the answers

    What is the next step after closing the exhaust line valve when stopping a non-condensing turbine?

    <p>Keep the oil pumps running until the bearings have cooled.</p> Signup and view all the answers

    In a non-condensing turbine, when should the cooling water to the oil coolers be reduced or shut off?

    <p>When the oil temperature has dropped significantly.</p> Signup and view all the answers

    What should be done after warming up a small turbine for less time compared to a large turbine?

    <p>Reset the stop valve and trip gear when the turbine speed decreases.</p> Signup and view all the answers

    What should be done when the governor takes control of the turbine speed during the warm-up phase?

    <p>Open the stop valve until the governor takes over.</p> Signup and view all the answers

    When closing a non-condensing turbine's exhaust line valve, what is the function of reducing or shutting off the cooling water to the oil coolers?

    <p>Maintain the oil pump's efficiency.</p> Signup and view all the answers

    What is the appropriate sequence of steps to follow while stopping a non-condensing turbine?

    <p>Reduce load, close exhaust line valve, close steam supply, start auxiliary oil pump.</p> Signup and view all the answers

    What should be done to the turbine speed immediately after the warm-up is complete?

    <p>Rapidly increase the speed until the turbine trips on overspeed</p> Signup and view all the answers

    What should be done when the turbine speed has decreased to about 20% below normal operating speed?

    <p>Reset the stop valve and the trip gear quickly</p> Signup and view all the answers

    What is the next step after gradually increasing the load on the turbine?

    <p>Check and adjust the governor to maintain speed</p> Signup and view all the answers

    What action should be taken to stop a non-condensing turbine?

    <p>Manually close the exhaust line valve first</p> Signup and view all the answers

    After closing the exhaust line valve, what should be done next to complete the stopping of a non-condensing turbine?

    <p>Start the separately driven auxiliary oil pump</p> Signup and view all the answers

    Why should the cooling water to the oil coolers be reduced or shut off when the oil temperature begins to drop?

    <p>To avoid thermal shocks to the hot bearings</p> Signup and view all the answers

    What is the recommended procedure to start a large turbine equipped with a pressure lubricating system operated by a separately driven oil pump?

    <p>Start the oil pump and verify sufficient oil pressures and flows are established before beginning to roll the turbine</p> Signup and view all the answers

    What is the purpose of opening the bypass lines around the traps when draining condensate from steam and exhaust lines?

    <p>To facilitate the complete drainage of condensate</p> Signup and view all the answers

    What is the significance of checking that the governor linkages are well lubricated before starting the turbine?

    <p>To prevent wear and tear on the governor linkages</p> Signup and view all the answers

    Why is it important to listen carefully for any noise indicating that the rotor is rubbing against the casing when starting the turbine?

    <p>To prevent damage to the rotor and casing</p> Signup and view all the answers

    What happens to the rotor if oiler rings are not operating correctly when starting the turbine?

    <p>The rotor may rub against the casing causing damage</p> Signup and view all the answers

    What is the purpose of increasing the turbine speed to 200-300 r/min after starting the turbine?

    <p>To check for any unusual noises or problems</p> Signup and view all the answers

    What should be done to the lubricating oil before starting the turbine?

    <p>Cool it to around 35°C to 40°C</p> Signup and view all the answers

    Why is it important to warm up the main supply and extraction steam lines to the turbine?

    <p>To prevent damage to the rotor due to slugs of water</p> Signup and view all the answers

    What should be checked during the start-up of the turbine to ensure each bearing is receiving a good supply of oil?

    <p>Lube oil return sight glasses</p> Signup and view all the answers

    What is the purpose of establishing a level in the surface condenser?

    <p>To allow the turbine to operate and produce steam condensate</p> Signup and view all the answers

    What is circulated through the surface and gland steam condensers?

    <p>Condensate</p> Signup and view all the answers

    What is the purpose of starting the lubricating oil pump two to three hours before steam is admitted to the turbine?

    <p>To supply lubricating oil to the bearings</p> Signup and view all the answers

    What is the purpose of admitting sealing steam to the turbine glands during startup?

    <p>To create a tight seal to prevent steam leakage</p> Signup and view all the answers

    What is the next step after verifying that all turbine trips have been satisfied and resetting the governor?

    <p>Watch to make sure the extraction valves go wide open</p> Signup and view all the answers

    Why is it essential to ensure the turning gear is disengaged and locked out during startup?

    <p>To prevent injury to personnel</p> Signup and view all the answers

    What should be done when the governor takes over during the warm-up phase?

    <p>Open the throttle valve completely</p> Signup and view all the answers

    What is the purpose of starting the jacking oil pump during startup?

    <p>To float and lift the turbine shaft</p> Signup and view all the answers

    What should be done when stopping a condensing and extraction turbine?

    <p>Gradually reduce the turbine load to zero</p> Signup and view all the answers

    Why is it important to maintain a maximum vacuum in the condenser during startup?

    <p>To increase turbine efficiency</p> Signup and view all the answers

    What should be done after the barring time has been completed during shutdown?

    <p>Shut down the barring gear</p> Signup and view all the answers

    What is the purpose of shutting off the supply of demineralized water during startup?

    <p>To maintain a normal level in the surface condenser</p> Signup and view all the answers

    What should be done to the turbine speed immediately after the warm-up is complete?

    <p>Maintain the turbine speed</p> Signup and view all the answers

    What is the purpose of warming up the main supply and extraction steam lines to the turbine before starting?

    <p>To reduce the risk of slugs of water damaging the rotor</p> Signup and view all the answers

    What is the purpose of establishing a level in the surface condenser before operating the turbine?

    <p>To ensure proper production of steam condensate</p> Signup and view all the answers

    Why should the lube oil pump supply lubricating oil to the turbine bearings for two to three hours before steam is admitted?

    <p>To confirm proper lubrication to prevent bearing damage</p> Signup and view all the answers

    What role does the external heating system play in the turbine startup process?

    <p>Warming the lube oil supply tank</p> Signup and view all the answers

    Why is it important for the lube oil return sight glasses to show each bearing receiving a good supply of oil?

    <p>To ensure proper lubrication and prevent bearing damage</p> Signup and view all the answers

    What is the significance of circulating condensate through the surface and gland steam condensers?

    <p>To prevent water from entering the cooling water system</p> Signup and view all the answers

    What is the recommended procedure to ensure the turbine vibration panel is functioning properly during turbine startup?

    <p>Monitor the turbine vibration panel while maintaining a turbine speed of 200 to 300 r/min.</p> Signup and view all the answers

    Which of the following actions is performed to ensure maximum vacuum in a condensing turbine during the warm-up phase?

    <p>Start the mechanical vacuum pump to draw a partial vacuum on the condenser.</p> Signup and view all the answers

    When stopping an extraction turbine, what mechanism automatically disengages after the shaft has fully stopped rotating?

    <p>The turning (barring) gear</p> Signup and view all the answers

    Which of the following is an essential step in the required warm-through timing prescribed by the manufacturer during turbine startup?

    <p>Monitoring sliding ft movement and rotor expansion rate to stator clearance.</p> Signup and view all the answers

    During which phase should gland steam be adjusted, if used, in a turbine startup procedure?

    <p>When the governor takes over.</p> Signup and view all the answers

    When exactly is the jacking oil pump stopped during the turbine shutdown procedure?

    <p>When the shaft has fully stopped rotating.</p> Signup and view all the answers

    Which valve should be opened first during turbine startup to start the turbine rotating before the barring gear disengages?

    <p>The throttle or steam admission valve</p> Signup and view all the answers

    Which component is responsible for providing high-pressure hydraulic oil to operate servo-rams in an Electro-Hydraulic Governor System?

    <p>The hydraulic accumulator</p> Signup and view all the answers

    During the warm-up phase of a turbine startup, which event denotes that the governor has taken over control?

    <p>The throttle valve is opened completely.</p> Signup and view all the answers

    Study Notes

    Starting a Condensing and Extraction Turbine

    • Ensure the main oil tank has sufficient high-quality turbine lubricating oil.
    • Commission the external heating system for the lubricating oil supply tank, if equipped, to reach the minimum temperature recommended by the manufacturer (usually 35°C to 40°C).
    • Start the lubricating oil pump 2-3 hours before steam is admitted to the turbine, supplying oil to the bearings at 140-150 kPa.
    • Warm up the main supply and extraction steam lines to the turbine by opening drain valves to prevent water slugs from causing damage to the rotor.
    • Establish a level in the surface condenser by adding demineralized water and commission the surface condenser level control system.
    • Start the cooling water pump and establish cooling water flow through the surface condenser, gland steam condenser, and air ejector condenser.
    • Start the extraction (condensate) pump and circulate condensate through the surface and gland steam condensers.
    • Start the jacking oil pump, which supplies lubricating oil at 8000-10 000 kPa to the bottom of the bearings to float and lift the turbine shaft.
    • Commission the turning or barring gear and the unit that the turbine is driving.
    • Admit sealing steam to the turbine glands and put the air ejector into operation to draw a partial vacuum of 50 kPa absolute of mercury on the condenser.
    • Verify that all turbine trips have been satisfied and reset the governor.
    • Unblock the extraction steam block valve and open the throttle or steam admission valve to start the turbine rotating.
    • Increase the turbine speed to 200-300 r/min, checking for unusual noises or vibrations, and follow the manufacturer's recommended startup procedure.

    Stopping a Condensing and Extraction Turbine

    • Gradually reduce the turbine load to zero.
    • Shut off the supply of steam to the turbine by manually closing the main inlet and extraction block valves.
    • Shut off the air ejectors and break the condenser vacuum.
    • Shut off the gland condenser steam.
    • Open the demineralized water supply and verify that a normal level is being maintained in the surface condenser.
    • Open the steam drain valves and start the jacking oil pump.
    • Start the turning (barring) gear and, when the machine has cooled sufficiently, stop the cooling water pump.
    • After the required barring time, shut down the barring gear and, when the shaft has fully stopped rotating, shut down the jacking oil pump.
    • Shut off the lubricating oil pump.

    Lube Oil Systems

    • Turbines require lubricating systems to ensure a reliable supply of lubricating oil to all moving parts.
    • Small turbines (less than 150 kW) use ring-oiled bearings, while medium-sized turbines use both ring-oiled bearings and circulating oil systems.
    • Large turbines have oil-circulating systems that supply lube oil to the turbine bearings, the bearings of the driven machine (e.g., the generator), and the reducing gear, as well as provide hydraulic operating oil to the governor mechanisms and steam throttle valves.
    • The lubrication system size is determined by the turbine size.
    • Figure 1 shows a typical lube oil system for a small turbine and generator set.
    • The main oil pump is directly driven by gears from the turbine shaft, and two standby pumps are driven by electric motors.
    • The oil pumps take suction from the oil tank through strainers and discharge the oil at high pressure (552-827 kPa).
    • The oil flows in two directions: to the power oil and governor relay oil systems, and to the oil coolers and then to the turbine generator bearings.
    • The power oil and governor relay oil must be at high pressure, while the oil used for lubrication is supplied at a lower pressure (69-138 kPa).

    Barring Gear

    • Figure 3 shows an oil-operated piston arranged to rotate the yoke about the worm shaft and engage or disengage the turning gear from the turbine shaft.
    • Figure 4 shows the location of the barring gear on a very large turbine.
    • The barring gear is positioned at the side of the bearing, enabling the gear to engage the shaft below the turbine center line.
    • Figure 5 shows the installation of the barring or turning gear in a Low Pressure end of a turbine.

    Jacking Oil Systems

    • Large turbines with heavy rotors are equipped with a jacking oil pump, which supplies the lower part of the bearings with oil at approximately 10 000 kPa, lifting the shaft and supplying lubricating oil.
    • The high oil pressure lifts the shaft a fraction of a millimeter, ensuring no metal-to-metal contact during initial start-up of the barring gear and reducing the starting load on the electric motor.
    • The jacking oil is applied before start-up of the barring gear and maintained while the turbine is at slow speed.
    • The jacking oil pump is shut down when the barring gear disengages, but it is also used when the turbine is shut down and is on barring gear for the cooldown period.### Barring Gear (Turning Gear)
    • Purpose: to prevent sagging and hogging of the turbine rotor when it's cold and at a standstill
    • Consists of an electric motor, reduction gears, and a turbine shaft
    • Operates at a slow speed (around 1% of operating speed, or as low as 1 rpm)
    • Warms up the turbine before startup and cools it down after shutdown to prevent vibration and ensure even cooling

    Jacking Oil System

    • Used in large turbines with heavy rotors to lift the shaft and supply lubricating oil
    • Supplied to the lower part of the bearings at a pressure of around 10,000 kPa
    • Applied before startup and maintained during slow speed operation
    • Shut down when the barring gear disengages

    Condensing Turbine Circuits

    • Two types: condensing units (exhaust at pressures below atmosphere) and non-condensing units (exhaust at or above atmospheric pressure)
    • Condensing units: exhaust steam from the turbine enters the condenser, where heat is exchanged with cooling water, causing the steam to condense
    • Examples of condensing turbine circuits: simple steam power plant, nuclear power plant

    Steam Turbine Governors

    • Control the steam flow to maintain a constant speed or pressure
    • Two types: speed-sensitive governors and pressure-sensitive governors
    • Speed-sensitive governors: responsive to speed changes, used in impulse turbines
    • Pressure-sensitive governors: responsive to pressure changes, used in backpressure and extraction turbines

    Speed-Sensitive Governors

    • Three types: nozzle governing, throttle governing, and bypass or overload governing
    • Nozzle governing: regulates the flow of steam to inlet nozzles
    • Throttle governing: throttles the steam flow into the turbine casing
    • Bypass or overload governing: uses two throttling valves to allow the turbine to maintain speed while producing extra power during high load or overload conditions

    Pressure-Sensitive Governors

    • Two types: backpressure governing and extraction governing
    • Backpressure governing: controls the exhaust pressure at the turbine outlet
    • Extraction governing: controls the steam pressure at the point of extraction

    Governor Droop

    • The change in speed that results from an increase in load
    • Expressed as a percentage of the set speed
    • Ideal governor: maintains a constant speed at any load, but mechanical losses prevent achievement of this speed control

    Isochronous Control

    • Regulates the turbine at a constant speed regardless of load
    • Two common arrangements: bar-lift and cam-lift systems
    • Bar-lift system: uses a row of inlet nozzles and a set of nozzle valves, or plugs, that are held in a horizontal lifting beam
    • Cam-lift system: uses a cam-like device to control the sequence and opening of each nozzle, individually operating the nozzle valves### Steam Turbine Governors
    • Steam turbine governors control the steam flow to maintain a constant speed with varying loads or constant pressure with varying demands for process steam.
    • There are two types of turbine governors: speed-sensitive governors and pressure-sensitive governors.

    Speed-Sensitive Governors

    • Three methods of speed-sensitive governing are used in steam turbines:
      • Nozzle governing
      • Throttle governing
      • Bypass or overload governing
    • Nozzle governing:
      • Used in impulse turbines
      • Regulates the flow of steam to inlet nozzles
      • Two common arrangements: bar-lift and cam-lift systems
    • Throttle governing:
      • Used in reaction turbines
      • A single valve at the inlet to the turbine throttles the steam flow
      • One or two control valves control the load from 0% to 100%
    • Bypass or overload governing:
      • Used on both impulse and reaction turbines
      • Consists of two throttling valves, one at the inlet of the first stage and the other at an inlet downstream of the first few stages
      • Allows the turbine to maintain speed while producing extra power during high load or overload conditions

    Pressure-Sensitive Governors

    • Pressure-sensitive governors control a steady backpressure at the turbine exhaust or extract steam from part way through the turbine and discharge it at a controlled pressure.
    • Backpressure governing:
      • Uses a pressure-sensing element on the exhaust steam line from the turbine
      • Adjusts the position of the inlet steam throttle valve to maintain a setpoint pressure
    • Extraction governing:
      • Used in extraction turbines to extract steam at controlled pressure from intermediate stages
      • Control systems are complicated, requiring adaptation to changes in turbine load and steam extraction demand

    Governor Droop

    • Governor droop is the change in speed that results from an increase in load.
    • The ideal governor would maintain a constant speed at any load, but mechanical losses prevent this.
    • The difference between the no-load and full-load speed, expressed as a percentage of the set speed, is the governor droop.

    Isochronous Control

    • Isochronous governors regulate the turbine at a constant speed regardless of load.

    Types of Speed Sensitive Governors

    • Mechanical governors:
      • Simple, mechanical governor: uses a set of weights, called flyweights, that pivot and move in and out to control the steam inlet valve
      • Mechanical-hydraulic governor: uses a pilot valve and hydraulic amplifier to remove mechanical losses
    • Mechanical-hydraulic governors:
      • Use a pilot valve and hydraulic amplifier to reduce mechanical losses
      • Have a lower droop than mechanical governors
    • Electronic-hydraulic governors:
      • Use a combination of electronic and hydraulic controls
      • Use a computer in the control console to amplify and compare the speed signal to a reference signal
      • Have a separate fluid power unit to provide high-pressure hydraulic oil to operate the servo-rams

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    Learn about the importance of lubricating systems in turbines and the different types of lubrication systems used based on the size of the turbine. This quiz covers the use of ring-oiled bearings and circulating oil systems in small and medium-sized turbines.

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