Main Steam and Turbine
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APPLY the functions of the Turbine, Turbine Oil and Gland Seal Systems in the support of plant operations.
Main turbine converts thermal energy into useful work
Turbine oil system provide turbine and generator lubricating needs
- High pressure fluid for valve actuation, turbine
- control and tripping
Steam sealing system prevent steam leakage from turbine case, prevent air leakage inward
Turbine has 1 Impulse stage and 7 Reactor stages
Turbine has 9 Reactor stages
Gland Steam Pressure
3 - 5 PSIG reduced from main steam
At what pressure does CV-3725 open to spillover excess Gland Steam?
> 5.5 PSIG
What are the Gland Seal over protections
- Relief Valve at 25 PSIG
- Rupture Disc at 100 PSIG
List Three Turbine Trips
- Low Vacuum
- High thrust bearing pressure
- Overspeed (1990 RPM)
List exhaust hood spray setpoints
When spray occurs
When CR receives an alarm
When Reactor Trips
- Spray at 142oF
- Alarm at 175oF
- Trip at 250oF
Setpoints for the thrust bearing trip device are
•35 psig alarms TURB THRUST BRG WEAR annunciator window E-1/3.
•75 psig alarms TURB THRUST BRG TRIP annunciator window E-6/1.
•At 75 psig a turbine trip occur
Where is Gland exhauster powered from?
A MCC / B MCC
What are the setpoints for the Gland Steam Condensor Receiver Drain Pump
- Auto starts at 14" below ground level
- Auto stops at 48" below ground level
What are the power supplies for the Turning Gear
3A MCC / 4A MCC
What is the normal turning gear amperage
<32 Amps Steady
What is the turning gear engagement sequence
- Turbine spinning down from 600 rpm
- Starts Bearing Lift Pump
- Opens SV-3400 to supply oil to TG & zero speed indicator
- At zero speed open 20/TGE and 20/TGV to engage Turning Gear
What is the capacity of the Lube Oil Tank and how many do we have at PTN
- 11' diameter cylindrical tank with a capacity of 14,800 gallons and is common to both units. 1 Storage tank that can take oil from either units lube oil reservoir but not both at the same time.
- Lube Oil Tank should normally be empty
What is the capacity of either units lube oil reservoir tank?
13,875 gallons full. Normal level is 10,000 gallons
What is the primary function of the guarded oil system?
Fire Protection. Pipe inside of a pipe to prevent leaks directly onto the turbine which would flash to fire
How is the Main Oil Pump powered?
Shaft driven and mounted in the governor end of the turbine. Starts at ~1700 RPM
Describe the Auxiliary Oil pump
- 200 HP U3, 250 HP U4 - LC3(4)C
- Suction below the oil level to eliminate need of priming.
- Consists of 2 pumps on common shaft.
- High pressure (Low volume/capacity)
- Low pressure (High volume/capacity)
- At startup supplies suction for main oil pump and oil to the zero speed indicator.
- Auto start (Switch in Mid Position) on decreasing bearing oil pressure of »10 psig
Describe the Turning Gear Oil Pump
- Vertically mounted on Turbine lube oil reservoir.
- 40 HP (Same on both units) - MCC 3A [MCC 4A]
- Pump is self priming with suction below oil level
- Discharges to:
- –Bearing oil
- –Seal oil backup
- Auto start – pump starts on low bearing pressure »9 PSIG (PS-3609) and no LOOP on “A” or “B” Bus
Describe the Emergency Bearing Oil Pump
- Same type pump as turning gear oil pump
- Motor driven - 40 HP DC (Same on both units) 3(4)D31
- Pump is an emergency backup if AC is lost.
- AUTO - Pump starts on low bearing oil pressure of »7 PSIG (PS-3608)
Describe the Bearing Oil Lift Pump
- Multi-vane, positive displacement, horizontal pump
- Motor driven - 25 HP on Unit 3; 20 HP on Unit 4
- MCC 3A [MCC 4A]
- Used on turbine startup, shutdown, and TG operation.
- Supplies lift oil to all but the extreme north and south turbine bearings including the generator bearings.
- Takes suction on the bearing oil discharge header cooler outlet
- In AUTO pump starts when rotor speed decreases to 600 RPM and Bearing oil supply pressure >9 PSIG.
Describe the Oil Ejectors
- Mounted inside the reservoir below the oil level.
- Uses main oil pump discharge as the motive fluid.
- Fluid pumped is the reservoir oil.
- Large flow of low pressure oil
- Zero speed indicator
- Turbine and generator bearings
- Turning gear.
- Main oil pump suction (other ejector)
What cools the turbine lube oil coolers
Describe the vapor extractor
- Motor driven blower
- Removes and discharges to atmosphere, oil vapors rising from the reservoir and H2 gas.
- Provides a low pressure area for better drainage
- Normally in operation (Must be in operation when turbine is idle or <600 RPM with an oil pump in operation)
- Vacuum on the Lube Oil Reservoir should be maintained between 4 to 5 inches of water as indicated on PI-4-1559
Describe the Turbine Lube Oil Conditioning System
- Removes foreign particles and water from the turbine Lube oil.
- Contains three main compartments and a pump, associated piping, valves & controls.
- Located below and to the east of the Lube Oil Reservoir.
- Variable speed positive displacement pump – from reservoir to the conditioner then back to reservoir.
- Normally in service cleaning the oil in the lube oil reservoir.
- Turbo-Toc pump has internal relief to protect from dead head conditions.
- Powered from non-vital MCC 3(4)A
- Local Start-Stop pushbutton.
- The 3 main compartments of the conditioner:
- –Pre-filter - 3 filter elements sized for 6 microns
- –Coalescer vessel - 2 compartments of coalescent filters
- –Polishing filter - 3 filter elements sized for 2.8 microns
What is the purpose of the Turbine Control System
- Regulates the speed and load of the main turbine.
- Controls amount of steam flow through turbine.
- Provides turbine protection
Explain the design basis of the Turbine Control System
- Drive the turbine generator such that the generator may produce its rated megawatt output (MWR) of 774 MWe
- Turbine trip initiates a reactor and generator trip above >10% power
- Generator trip to prevent motorizing the turbine
Where are the Main Turbine Stop Valves Located?
Located between MSIVs and turbine control valves
What is the Governor Impeller Discharge
- PI-3413 (30 PSIG @ 1800 RPM)
- Constant 15 GPM flow from main oil pump
The Main Governor
- Controls speed when synchronizing turbine
- Controls load when on the line
The Main Governor Speed Changer Switch has how many positions
Describe the function of the Auxiliary Governor
Controls turbine speed when speed increases to between 1850 and 1950 or acceleration is >3% / sec.
List the 5 trips Auto Stop Oil Arms
- Low bearing oil pressure
- High thrust bearing oil pressure
- Low vacuum
- Solenoid valve (20 AST) operates tripping lever
- Overspeed trip
Describe the operation of the overspeed trip mechanism
Trip weight forced outward due to centrifugal force at 1998 RPM
What will happen if the Turbine Trip Handle is left in the TEST position?
Handle in TEST position blocks all trips (except 20-ASB).
How does the Turbine Thrust Bearing Trip Device work
- Thrust bearing located between the two LP turbines
- Shoes wear as rotor turns
- Trip shuts down turbine before turbine blades are damaged due to axial movement.
How many Turbine Stop Valves and How Many Turbine Control Valves?
2 Stop Valves and 4 Control Valves
State the functions of Main Steam
- Supplies steam to main turbine throttle valves
- Reheats steam to low pressure turbines
- Supplies steam to steam jet air ejector, hogging jets and water box priming jet
- Supplies steam to gland sealing steam system
- Supplies steam to auxiliary feed pump turbines
- Provides means of RCS temperature control using Steam Dumps (atmos. & condenser)
- Supplies steam to the auxiliary steam system pressure reducing station
- Supplies steam for the turbine cylinder heating system
State the function of extraction steam
- Extracts steam from main turbine
- Preheats feedwater in feedwater heaters
- Improves steam cycle efficiency
State the backups for Unit 3 and Unit 4 MSIVs
- Unit 3 Nitrogen Backup
- Unit 4 Air Accumulator
State the graduated setpoints for the Main Steam Safety Valves
- RV-1400 (1405, 1410): 1085 psig
- RV-1401 (1406, 1411): 1100 psig
- RV-1402 (1407, 1412): 1115 psig
- RV-1403 (1408, 1413): 1130 psig
- T/S- Mode 3 or Above: Safeties Operable!
When do the MSIVs close?
- Close on “Steam Line Isolation”
- Annunciator C-8/2
- Containment High (4PSIG) and High-High Pressure (20PSIG)
- High Steam Flow (40% to 114%) coincident with:
- Low Tavg (543oF)
- Low Steam Line Pressure(614 PSIG)
Describe the Main Steam Isolation Valves
- One per steam line
- Air Operated Stop Check
- Header A: POV-3/4-2604
- Header B: POV-3/4-2605
- Header C: POV-3/4-2606
Steam dumps must be ______ in order to operate
The greater the difference between Tavg and Tref
The more the dump valves are open
What are the setpoints for the Aux steam relief valves
- RV6264 - 288 PSIG
- RV1422 - 275 PSIG
What are the 3 loads off of the 250# Aux Steam
- Condenser Waterbox Aux Priming Ejectors
- Back-up Supply to the AFW pumps
- Opposite units main steam line warm-up
What are the power supplies for Aux Steam
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