Main Turbine, Turbine Lube Oil, Auto Stop Oil, Gland Seal Flashcards
Describe the Main Turbine.
Converts steam enthalpy into mechanical work
HP Turbine - 7 Stages, (90% Impulse, 10% Reaction)
LP Turbine (2) - 8 Stages (Reaction)
10% Step Load; 5%/minute Ramp Load
Guaranteed ~1080 MWe, Normal observed ~1010 MWe
Describe the Steam Flow thru Turbine
Throttle Valve (Stop Valve) => Governor Valve (Control Valve) => Steam Chest => Nozzle Block => Nozzles => Center of HP Turbine (flow axially to both ends – first stage is 90% impulse, 10% reaction; impulse characteristic decreases thru next 6 stages => Exhaust Trunk => MSR Shell => MSR Chevron Baffles => over MSR tube bundles => Reheat Stop Valve => Intercept Valve => LP Turbine (2) => 8 stages of reaction blading => Main Condenser
Describe the Turbine Throttle Valves.
Rapidly stop steam flow on a turbine trip
Control Turbine speed from initial roll to 1750 rpm
Opening sequence
a) Small inner valve opens first
b) Allows steam pressure to equalize across larger valve, less force necessary to open main valve
c) EH system used to overcome spring pressure to open valve
During turbine roll, the throttle valves are used to bring the turbine to 1750 rpm. The valves are then fully opened and the governor valves control speed or turbine load.
All Throttle Valves close on:
Turbine Trip
Describe the Turbine Governor Valves.
Control turbine speed > 1750 rpm
Stop steam flow on a turbine trip
Control MW
All Governor Valves close on:
a) Turbine Trip
b) Overspeed - (103% of rated speed “1854 rpm”) fed from Overspeed Protection Control (OPC)
c) Load Drop Anticipator - Prevents overspeed on a total loss of load by closing Governor Valves & Intercept Valves.
d) Turbine Acceleration (Prevents speeding up too fast.)
Describe the Turbine Intercept Valves.
Right above the LP turbine
Stop steam flow from MSR to LP turbine on:
a) Turbine trip
b) Overspeed from OPC (103%)
c) Load Drop Anticipator (LDA)
d) Turbine Acceleration
Describe the Turbine Reheat Stop Valves.
Right above the MSR
Close on turbine trip to prevent overspeeding of the turbine should the intercept valve fail to close
Describe Turbine Drain Valves.
Remove moisture from Turbine
9 Drain Valves, One switch operates all valves, fail open
4 on HP inlet, 4 on MSR inlet (have orifice bypass), 1 is HP Turbine Casing drain to Main Condenser
One switch which controls all of the valves (Close – Auto – Open)
“AUTO” – valves open at ~ 20% and lowering turbine load based on OPC pressure (PT-22-28, 39A, 39B)
< 20% Load, drains verified open per GOP-123
Describe the Turbine Casing Breakable Diaphragms (Rupture Disks).
Backup safety device if Low Vacuum Trip mechanism fails to provide condenser overpressure protection
4 per LP Turbine casing
Rupture at 5 psig
Describe the Turbine Gland Seal System.
Prevents air and dirt from being drawn into the turbine thru the rotor casing penetrations
Gland Seal is normally supplied by:
a) Main Steam System (≤ 20% power)
b) Governor Valve and Throttle Valve high pressure steam leakoff ≥ 20%
c) ≥ ~ 20% power the HP turbine provides its own sealing steam
Main Gland Seal Regulator takes Main Steam and reduces it to 125 psig
The 125# Header has 5 other individual Gland Seal Regulators that reduce pressure to:
* (1) 16-21 psia for HP Turbine
* (4) 2.5-5 psig for LP Turbines
GV’s HP Leak off taps in upstream of the HP Regulator PCV and can supply LP & HP turb seals
TVs HP Leak off taps in downstream of the HP Regulator PCV supplies HP turbine only
Gland Seal is placed in service AFTER Turbine is on Turning Gear and BEFORE drawing vacuum
Overpressure Protection downstream of the Main Gland Seal Regulator is provided by:
a) Safety Valve that lifts @ 300 psig
b) Rupture Disc that blows @ 500 psig.
Both are located inside the HP Turbine Housing East side
Gland Seal Header pressure maintained by the Spillover Regulator, dumps excess steam back to the Main Condenser (PCV ~17 psia) or Manual control of the Spillover Bypass valve from RTGB
Describe the Gland Steam Exhausters.
Remove air and non-condensable vapors from the gland steam condenser.
Exhaust steam is then sent to the Plant Vent Stack via SJAE Rad Monitor
Receives gland steam exhaust and turbine valve leak off. Cooled by condensate system
Drains to gland steam condensate Receiver Tank which is pumped back to the hotwell by the Condensate Receiver Tank Transfer Pump. Maintained at 14.6 psia (18-25 in H20 vacuum) by Gland Exhaust Fans, Normally only one running, Controlled from RTGB 101[201], MCC A1/B1
Describe Turbine Exhaust Hood Spray: (TCV-22-61-A & TCV-22-61-B).
Prevent LP turbine rotor overheating under low vacuum or low load conditions
Exhaust Hood Spray flows thru an AOV on the discharge of Condensate pumps or from the Condensate Transfer Pump, NPO opens the HOOD Spray Bypass valves for SPTA’s
Exhaust Hood Temperature Can Be Lowered By Improving Condenser Vacuum, Increasing Electrical Load (Increases Steam Flow), and Actuation of Exhaust Hood Spray
6 RTDs (3 for A and 3 for B) look at exhaust hood temperature and input into the following actuations:
a)250 F-Turbine Trip - (2/3 on either exhaust hood) - Trip via TDM-1 & 2
b)175 F-Exhaust Hood High Temperature Alarm – (1/3 on either exhaust hood)
c)160 F-Exhaust Hood Spray Valves Open
Describe the Turbine Journal (Sleeve) Bearings.
(9) Support the rotor during normal operations
Describe the Turbine Thrust Bearing.
Located on governor end of the LP Turbines; Flooded with oil under pressure at all times
Absorbs axial thrust from generator transmitted thru the turbine rotor
Describe the Turbine Turning Gear.
Turning Gear is located between the Generator and the LP Turbine.
Powered from 1C [2C] – loss of this MCC would prevent Auto TG engagement
Rotates Turbine rotor at 1.5 rpm to minimize bowing due to uneven HU or CD
RTGB – OFF/MANUAL/AUTO; Local PB’s – START/STOP/JOG
What is required to momentarily jog the Turning Gear?
PB Jog (momentary) at the turning gear requires:
1) Turning gear intermediate/engaged or RTGB switch in Manual
2) Oil bath pressure switch senses >4-5 psig.
3) Lift oil pressure switch senses >1350 psig
What is required to PB Start at the turning gear?
PB Start at the turning gear requires:
1) Turning gear intermediate/engaged or RTGB switch in Manual
2) Oil bath pressure switch senses >4-5 psig.
3) Lift oil pressure switch senses >1350 psig
When does Oil flow to the Turning Gear bath start?
1) RTGB Control switch is in Manual; OR
2) RTGB Control switch is in Auto and Turbine Speed < 600 rpm
Describe Auto Turning Gear Engagement/Start.
1) RTGB Control Switch in AUTO
2) (2/2) Both Zero Speed Monitors indicate Zero RPM
3) Turbine Speed < 600 rpm
4) Lift Oil pressure > 1350 psig
5) Oil Bath pressure > 4-5 psig
What will cause the Turning Gear to Auto Disengage?
1) If Turbine Speed increases > 1.5 RPM.
Lever position reaches intermediate, and engaging air pressure is < 20 psig
2) Allows the engaging lever to mechanically unlatch if rpm increases beyond 1.5 rpm
3) When fully disengaged, air is removed, and circuit is reset for another engagement attempt
Describe the Turning Gear synopsis.
As turbine < 600 rpm
* Bearing Oil Lift Pump starts
* Lube oil is aligned to the turning gear oil bath
When turbine stops
* Logic complete for lever engaging air
* Gear engages
Engagement completes the motor start logic and starts turning gear motor if:
* Lift Oil Pump > 1350 psig
* 4-5 psig TG Oil bath pressure
When zero speed monitors sense > 0 rpm
* Engaging air removed
* Turbine continues to rotate at 1.5 rpm
What Turning Gear Indications are available in the Control Room?
RTGB lights indicate the status of the turning gear systems
Red/Green for Running/Stopped and Engaged/Disengaged
Amber for Satisfied Lube Oil Permissive
How is Turbine Speed determined?
Proximity probes are installed above the Turning Gear (60 Teeth) and provide pulse inputs (AC signal) to determine Turbine speed.
What does the Main Turbine Lube Oil System Supply?
Consists of an HP and LP header.
The HP header is supplied by:
1) Shaft Driven Main Lube Oil Pump when the turbine is operating.
2) AC Seal Oil Backup Pump when the turbine is shutdown.
The HP Header supplies:
1) Shaft Driven MLO Priming Eductor
2) HP Seal Oil B/U
The LP Header is supplied by:
1) The Priming Eductor when the turbine is operating.
2) The Bearing Oil Pump (BOP) when the turbine is shutdown.
3) The DC Emergency Oil Pump (EOP) if AC power is lost.
The LP Header supplies:
1) Shaft Driven MLO Pump suction
2) Bearing Oil Lift Pump suction
3) TG Oil Bath,
4) Journal Bearings
5) Thrust Bearing
6) Low pressure Seal Oil back-up source
Describe the Unit 1 Turbine Lube Oil Storage Tank.
Supplies Both Units; Capacity – 15,000 gallons
