Main Turbine, Turbine Lube Oil, Auto Stop Oil, Gland Seal

Question 1

Describe the Main Turbine.

Answer 1

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

Question 2

Describe the Steam Flow thru Turbine

Answer 2

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

Question 3

Describe the Turbine Throttle Valves.

Answer 3

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

Question 4

Describe the Turbine Governor Valves.

Answer 4

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.)

Question 5

Describe the Turbine Intercept Valves.

Answer 5

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

Question 6

Describe the Turbine Reheat Stop Valves.

Answer 6

Right above the MSR
Close on turbine trip to prevent overspeeding of the turbine should the intercept valve fail to close

Question 7

Describe Turbine Drain Valves.

Answer 7

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

Question 8

Describe the Turbine Casing Breakable Diaphragms (Rupture Disks).

Answer 8

Backup safety device if Low Vacuum Trip mechanism fails to provide condenser overpressure protection
4 per LP Turbine casing
Rupture at 5 psig

Question 9

Describe the Turbine Gland Seal System.

Answer 9

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

Question 10

Describe the Gland Steam Exhausters.

Answer 10

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

Question 11

Describe Turbine Exhaust Hood Spray: (TCV-22-61-A & TCV-22-61-B).

Answer 11

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

Question 12

Describe the Turbine Journal (Sleeve) Bearings.

Answer 12

(9) Support the rotor during normal operations

Question 13

Describe the Turbine Thrust Bearing.

Answer 13

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

Question 14

Describe the Turbine Turning Gear.

Answer 14

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

Question 15

What is required to momentarily jog the Turning Gear?

Answer 15

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

Question 16

What is required to PB Start at the turning gear?

Answer 16

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

Question 17

When does Oil flow to the Turning Gear bath start?

Answer 17

1) RTGB Control switch is in Manual; OR
2) RTGB Control switch is in Auto and Turbine Speed < 600 rpm

Question 18

Describe Auto Turning Gear Engagement/Start.

Answer 18

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

Question 19

What will cause the Turning Gear to Auto Disengage?

Answer 19

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

Question 20

Describe the Turning Gear synopsis.

Answer 20

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

Question 21

What Turning Gear Indications are available in the Control Room?

Answer 21

RTGB lights indicate the status of the turning gear systems
Red/Green for Running/Stopped and Engaged/Disengaged
Amber for Satisfied Lube Oil Permissive

Question 22

How is Turbine Speed determined?

Answer 22

Proximity probes are installed above the Turning Gear (60 Teeth) and provide pulse inputs (AC signal) to determine Turbine speed.

Question 23

What does the Main Turbine Lube Oil System Supply?

Answer 23

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

Question 24

Describe the Unit 1 Turbine Lube Oil Storage Tank.

Answer 24

Supplies Both Units; Capacity – 15,000 gallons

Question 25

Describe the Turbine Lube Oil Reservoir.

Answer 25

Capacity - 15,000 gallons; all lube oil pumps are mounted on top

Question 26

Describe the Turbine Lube Oil Vapor Extractor.

Answer 26

Maintain Lube Oil Reservoir at a slightly negative pressure (~ 3” of Water) to ensure proper return oil flow
Mounted on top of each Unit’s Lube Oil Reservoir
Powered from MCC 1B1 [2B1]
Prevents casing oil leaks
Also prevents the buildup of Hydrogen Gas in the reservoir

Question 27

Describe the Turbine Main Lube Oil Pump.

Answer 27

(HP) (320-380 psig)
Supplies ALL Lube Oil system loads during normal operation; shaft driven
Suction source is from the eductor using the shaft driven pump discharge pressure.

Question 28

Describe the Turbine Bearing Oil Pump.

Answer 28

(LP) (40-50 PSIG)
Normal supply of LP oil during startup and shutdown
Backup for Main Oil Pump
Powered from 480V MCC 1C [2C], Primes Shaft driven MLO Pump,
Controlled by same switch on RTGB as the Seal Oil Backup Pump, (OFF/AUTO/PTL/START)
Auto starts at 9.5 - 13.5 psig and lowering if in AUTO

Question 29

Describe the Turbine Emergency Bearing Oil Pump.

Answer 29

(LP) (40-50 PSIG)
Backup to the Bearing Oil Pump on loss of AC power
Backup supply for Low Press Seal Oil
OFF/AUTO/PTL/START switch, Powered from 125 VDC Bus 1C [2C]
Auto starts:
1) 8.5 - 12.5 psig and lowering; OR
2) Loss of Pwr to Bearing Oil Pump and Main Gen Output Breakers Open
{The Unit 1 EOP will also start in Pull-to-Lock}

Question 30

Describe the HP Seal Oil Backup Pump.

Answer 30

(120-125 PSIG)
Supplies Lube Oil High Pressure Loads during SU and SD
Backup source of oil to the Seal Oil System
Powered from 480V MCC 1A1 [2B1]
Controlled by same switch on RTGB as Bearing Oil Pump, (OFF/AUTO/PTL/START)
Auto starts at 9.5-13.5 psig and lowering if in AUTO

Question 31

Describe the Turbine Bearing Lift Pump.

Answer 31

(1200-1500 Psig)
Supplies oil to the LP Turbine Bearings 3, 4, 5, & 6 to lift the shaft.
Suction provided by the MLO Pump or Bearing Oil Pump
Powered by 480V MCC 1A1 [2B1]
Auto starts:
1) Turbine rotor speed decreases to < 600 RPM; and
2) Turning gear oil bath > 4-5 psig

Question 32

Describe the Turbine Lube Oil Coolers.

Answer 32

Temp: 110-120F, Maximum inlet to bearing < 170°F, Bearing Metal Temp < 210°F
Turbine Vibration increases if the oil is too hot or too cold
Only 1 cooler in service at a time; Coolers can be swapped On-Line
Bearing temperatures/oil temperature monitoring/ alarms and turbine vibration are monitored by Turbine Supervisory System

Question 33

Describe Turbine Supervisory Instrumentation.

Answer 33

Provides essential information for operators about the condition of the turbine
a) Vibration
b) Eccentricity
c) Differential Expansion
d) Thrust Bearing Position
e) Case Expansion
f) Turbine Speed and Acceleration

Question 34

What conditions would require a Turbine Trip?

Answer 34

Need to trip the Reactor and/or Turbine if:
a) If a valid turbine vibration alarm of ≥ 14 mils
b) Bearing oil temperature > 180°F
c) Bearings 1-6: > 250°F
d) Bearings 7-8: > 225°F
e) Thrust Bearing: > 225°F

Question 35

Describe Condenser Vacuum Limitations.

Answer 35

4 Regions curve which govern acceptable Condenser Backpressure limits
Operating in the Restricted Region for 300 seconds (5 min) will generate an automatic turbine trip.
Total time spent in this region must be tracked. Max of 300 minutes allowed based on the LP turbine blades last row.
Automatic Turbine Trip is generated at ≥ 8.859 in HgA

Question 36

Describe the Turbine Startup Sequence.

Answer 36

• All valves shut
• BOP supplying LP LO
• SOBP supplying HP LO
• Main steam supplying steam seals
• Latch (Reset) the Turbine
• Resets the Turbine (operates the vacuum trip override arm and overspeed trip latch)
• Allows ETS Pressure to build up to 90 - 100 psig
• Emergency Trip Pressure increases to EH Supply Pressure
• Reheat Stop Valves & Intercept Valves go open
• Governor Valves are opened 100%
• TVs are opened to raise speed to1750 rpm
• At 1750 rpm, speed control is transferred from TV’s to GV’s
• GV’s close down to take over speed Control, TVs open 100%
• GV’s are use to increase speed and all subsequent turbine loading
• In Auto Control, Generator automatically picks up 65 MW when Synchronized to Grid
• When Latched - Turbine Trip Lamp will extinguish