Main Turbine Flashcards
What valves are operated by PACs ?
-Stop Valves
-Control Valves
-Combined Intermediate Valves(CIVs)
What’re the two types of Control PACs ?
-PACs for controlling steam valves
-PACs for non-controlling steam valves
What valves use a Controlling PAC ?
-Stop Valve #2
-Control Valves 1,2,3,4
-Intercept valves 1,2,3
What Valves use Non-Controlling Valves ?
-Stop Valves 1,3,4
-Intercept Valves 4,5,6
-Intermediate Stop Valves 1,2,3,4,5,6
How fast do the Control PACs normally open & close valves ?
10% per second
How fast do the PACs close valves on a Turbine Trip ?
Will rapidly close valves in 0.2 seconds
What is the difference between PAC Controlling Valves & PAC NON-Controlling Valves ?
Controlling valves- Have a servo-valve that regulates EHC Oil flow
NON-Controlling Valves- Test solenoid admits full flow to the valve maintain them fully open during normal operation
Test Solenoid used during MT valve testing
What is the Maintain Turbine Stop Valved used for ?
-Allow steam to Main Turbine during normal conditions
-Quickly isolates steam during emergency conditions
How is the Steam Chest formed by the Stop Valves ?
Outlet of each Stop Valve is welded to the inlet of each Control Valve & below sets of stop valves is welded together to form Steam Chest
What does Stop Valve #2 provide ?
-Bypass valve that can open across pressure drop across valve
-Slowly warms steam chest & HP Turbine
-Pressurizes steam chest to minimize DP across Stop Valves to open rest of the Stop Valves
When control room tests each Stop Valve one at a time, what is the AO supposed to be looking for ?
Supposed to monitor valve stroke during closing & opening of Stop Valve
Why aren’t Control Valves affected when the Stop Valves are being tested ?
Steam chest supplies all 4 Control Valves so it has little impact
What is the Steam Chest used for ?
Used as equalization line to maintain steam flow through all 4 Steam lines to the HP Turbine
Above 50% power, what system receives steam leakoff from the Stop Valves ?
Stop Valve leakage provides steam to Gland Sealing Steam
What’re the Main Turbine Control Valves used for ?
-Controls steam flow during startup& shutdown
-Regulates steam flow for load requirements during normal operation
-First line of defense to prevent over speeding during emergency condition
Where is the inlet of the Control Valve directly welded to ?
Directly welded to the outlet of the Stop Valves
While at rated power the Main Turbine Control Valves normally maintained at ?
Maintained 40-50% open
How do we test the Main Turbine Controls Valves if it’s going to affect on Main Turbine operation?
-Turbine temporality reduced so control valves are less than 40% open
-As each control valve is closed, other control valves will auto open to maintain supply to Main Turbine
-Once control valve is fully closed & opened, other control valves throttle back to original position
After 50% power where do the Control Valves leak off to ?
Leaks off to the Main Turbine Gland Sealing Steam
What does the HP Turbine Shell provide for the turbine ?
-Pressure barrier between Turbine internals & turbine building
-Maintains alignment of turbine
What is provided to the HP Turbine Shell to prevent Main Steam from leaking out at Low-Load operations ?
Gland Sealing Steam is applied to HP Turbine Shell to prevent main steam from leaking out Shell Joints
What speed does the turbine spin at ?
1800 rpm
What is the Turbine Rotor geared to inside the Front Standard ?
Geared to the:
-Main Shaft LO Pump
-Permanent Magnet Generator
-Also extends to the ‘A’ LP Turbine Rotor
Where does extracted steam from the 3rd stage of the HP Turbine go ?
-Goes to the #7 HPFW Heater
-Goes to the 1st stage of the MSR
Where does extracted steam from 5th stage of the HP Turbine go ?
Goes to the #6 HPFW Heater
Where does the Exhaust Steam go after it exits HP Turbine ? What is the HP Turbine Exhaust called?
- Cold Reheat goes to the MSRs
-Exhaust is called Cold Reheat
What two valves are in the Combined Intermediate Valves ?
-Intercept Valve
-Intermediate stop valve
What does the Intercept Valve do inside the CIVs?
-Regulates steam flow into LP Turbine
-Rapidly isolates steam from cross around piping
What do the Intermediate Stop Valves do inside the CIVs ?
-Second line of defense against energy stored in the Cross Around Piping in event of Intercept Valve failure
Why’re the CIVs located as close as possible to the LP Turbine ?
Limits amount of uncontrolled steam in the cross around piping to prevent overspending during a Turbine Trip
What happens to the CIVs during Normal Operation, Normal shutdown, & Turbine Trip
-CIVs are wide open during Normal Operation
-BOTH valves close during Normal Turbine Shutdown or Turbine Trip
Which Intercept Valves are Controlling Valves ? What do they do ?
IVs 1,2,3 regulate steam flow to the LP Turbine
Which IVs are NON-Controlling Valves? What’re they supposed to do ?
4,5,6 respond to the positioning of IV 1,2,3
What happens when the Controlling Intercept Valves reach 90% ?
NON-Controlling IVs for LP Turbine will fully OPEN
What happens when the Controlling Intercept Valves closes to 50%?
NON- Controlling Intercept Valves for the LP Turbine will go fully CLOSED
Which valves inside the CIVs can open against pressure ?
-Intercept valve can open against pressure
-Intermediate Stop Valve can’t open against pressure
Since the CIVs Intermediate Stop Valves can’t open against pressure, how are you supposed to open them ?
When opening CIVs the Intermediate Stop Valve must be opened first,
THEN Intercept Valve will be opened second
Why do we try minimizing time having the CIVs closed?
Uneven steam flow to the LP Turbine causes unequal heating which leads to High Vibration
What is provided to the CIVs to prevent leakage from valve casing ?
Gland sealing steam is supplied to both Intercept Valve & Intermediate Stop Valve
Where do the LP Turbine receive there steam from ?
Received hot reheat from MSRs
What is used to control temperature of the LP Turbine Hood during startup & Low Load operations ?
Has spray nozzles that spray water from condensate system
How is the flow of water to the spray valve controlled ?
Temperature transmitters & local temperature indicators will automatically adjust the spray valves
When is the manual bypass used for the Spray Nozzles for the LP Turbine ?
Used when the automatic system malfunctions
What are the rupture discs on each of LP Turbines used for ?
Protects LP Turbine exhaust hood & Condenser, during a loss of CW to the Condenser
How do the Rupture discs on the LP Turbine Exhaust Hood work ?
-If LP Turbine Exhaust Hood pressure rises to 5 psig, it forces rupture disc diaphragm into a cutting knife
-Relieves to Turbine Building Atmosphere
What’re the Main Turbine Bearings used for ?
-Absorbs Axial thrust on turbine & generator rotors
What’re the Main Turbine journal bearings used for ?
Supports weight of the Main Turbine Rotor
Where are the Journal Bearings located at ?
At the end of each:
-HP Turbine Rotor
-LP Turbine Rotor
-Main Generator Rotor
What’re the Main Turbine Bearings cooled by ?
Cooled by Main Turbine Oil fed into 25psig
What should the temperature rise across the bearings be?
Should be <45F
What is considered abnormal when it comes to the Main Turbine Bearings ?
ANY sudden increase in oil temperature across bearing is abnormal
Where is the oil that cools the Main Turbine Bearings drained to ?
Drained to Main Turbine Lube Oil Reservoir
Where is the lube oil drained to from the Main Generator ?
Drains into Aux. Detraining Section, then drains into Main Turbine LO Reservoir
What is the Sight Box used for on the Lube Oil system ?
Portion of Lube Oil from each heating passed through Sight Box that allows visual inspection & oil temperature
When is the Main Turbine Turning Gear used ?
Rotates Main Turbine Rotor slowly during shutdown periods when Rotor temperature changes occur
How does the Turning Gear prevents temporary bowing of the Main Turbine Rotor ?
Provides means to obtain uniform state of temperature in the Turbine Rotors
How is the Turning Gear used during Main Turbine Startup ?
Ensures no temporary rotor bow, which could affect:
-Shaft Clearances
-Unbalanced rotor weight causing vibration during startup
What does the Turning Gear
Pre-Engagement Motor do ?
It engages the Turning Gear onto the Main Turbine Rotor
What does the Turning Gear Driving Motor do ?
Supply torque for breakaway of Turbine Generator Rotor
What are the Turning Gear automatic actuations ?
-Engages & starts when rotor drops below speed set point
-Disengages when Main Turbine Rotor is rolled with steam
During turning gear operations where is the lubrication provided from ? Which pumps provide it ?
-Provided from Main Turbine LO system
-Turning Gear Oil Pump or Emergency Bearing Oil Pump for turning gear operations
What’re the Pre-Engagement Motor & Driving Motor powered from ?
Powered from NH
Does the Turning Gear have a shutoff valve for Lube Oil supply ?
No there is no shutoff valve from the Main Turbine Lube Oil supply header
What does the Emergency Trip System contain ?
-Combines mechanical trip in front standard & electrical trip signals of Trip& Monitoring system
-Contains Air Relay Dump Valves used following Turbine Trip
What does the Electro-Hydraulic Control Oil referred to as Emergency Trip Supply do ?
Allows Main Turbine Stop Valves, Control Valves, & Combined Intermediate Valves to open
What does the Emergency Trip System do to the Emergency Trip Supply when it receives a mechanical or electrical trip signal ?
Emergency Trip System isolated Emergency Trip Supply oil to all Control PACs which will trip CLOSE all steam valves
What’re the Air Relief Dump Valves used for? How do they work ?
-They’re kept opened by Emergency Trip Supply Oil
-Admit Instrument Air to Bleeder Trip Valves to overcome spring force to help maintain them open
What Air Relay Dump Valves do during a Turbine Trip ?
-ETS oil is cut off causing ARDVs to close which isolates Instrument Air from Bleeder Trip Valves
-This causes bleeder trip valves to close & prevent back flow steam going back to Main Turbine from extraction lines
When does the Main Turbine Overspeed Trip Device actuate ?
Actuated at 110% speed
How does the Overspeed Trip Device work ?
-Normal speeds compressed spring holds ring in normal position
-Overspeed will centrifugal force will over come spring force activating Mechanical Trip Mechanism
What does the Permanent Magnet Generator do ?
Provides AC power to Electro-Hydraulic Control Oil when Turbine is >95%
What do the Turning Gear Low Speed Switches do ?
-Electro- Hydraulic device that activates turning gear when MT Rotor speed drops below setpoint
-Sensed by Aux. Control Rotor
How do the speed sensors work ?
-Positioned around Aux Control Rotor
-Generates voltage proportional to shaft speed & provides it to Electro-Hydraulic Control Oil System
What does Thrust Bearing Wear Detector do?
-Hydraulic device detects axial position of Turbine Rotor compared to Thrust Bearing Casing
-TBWD activates Emergency Trip System when Thrust Bearings Plates exceed set point
Where do all the Main Turbine Valve drains routed to ?
Routed to the Main Condenser
What’re the position of the Main Turbine Drain Valves during normal, startup, & shutdown operations ?
-Closed during normal operation
-Opened on main turbine trip to depressurize steam lines
-Maintained open during shutdown
-Closed during startup
When is gland sealing steam provided to ?
-Stop & Control valves at low power
-High Pressure Turbine shell at low power
-Combined Intermediate Valves
-LP Turbine Shells
Where does Main Turbine supply Gland sealing steam at high power ?
Supplied from:
-Stop& Control Valves
-High Pressure Turbine
What will happen if the RCS gets to cold following a Main Turbine Setback ?
Main Turbine Runback is initiated to throttle Main Turbine Control valves & reduce Main Turbine loading
What happens on loss of Electro-Hydrualic Control Oil ?
Main Turbine Trip will happen
What is reactor power reduced to during a Main Turbine Trip or Load Rejection ?
Selected CEAs will drop into core reducing power level to 50%
During a Turbine Trip or Load Rejection besides a Reactor Power Cutback, what other system is put into service ?
The Steam Bypass Control System will be initiated to control RCS Temperature & Pressure
Where will Steam Bypass Control System dump steam to if there is no condenser vacuum ?
SBCS will dump steam to atmosphere to control RCS Temp. & Pressure
