Main Turbine and MSR (MT)

Question 1

What are the trips for the Main Turbine?

Answer 1

• Loss of Stator Cooling Water (70 sec TD, 2/3)
• Low Generator Inlet pressure
• High Generator outlet temp
• Low connection ring inlet flow
• Low stator inlet flow
• Low flow generator bushing
• Low Discharge Pressure on Shaft Driven Lube Oil Pump (2/3, 100 psig) (Enabled > 75% speed)
• MSR Hi-Hi Level (10 sec TD, 2/3 LTs on any MSR, 3” below MSR Bottom)
• Low EHC Pressure (2/3, 1100 psig)
• Low Bearing Oil Pressure (2/3, 12 psig)
• Low Condenser Vacuum (2/3, 7.5” HgA)
• Excessive Thrust Bearing Wear (40 Mils)
• High Exhaust Hood Temperature (225°F)
• Power Load Unbalance (Mismatch between generator amps and cross-under pressure)
• Excessive Vibration (12 Mils)
• Manual push button (same button gets 125Vdc and 24Vdc)
• Loss of 125Vdc power (enabled > 75% speed)

Question 2

What are the main turbine turning gear start interlocks?

Answer 2

TG motor start interlocks
o Piggyback motor stopped
o TG engaged for 5 seconds
o No quill shaft failure signal

Question 3

Which main turbine stop valve has an internal bypass? Why?

Answer 3

• Internal bypass valve (MSV-2 ONLY)
  o SVs cannot open against full pressure drop.
  o Bypass pressurizes the stop valve below seat areas for opening the MSVs.
  o Bypass warms the stop valve below seat areas and control valve bodies.
• MSVs open when a speed request is selected at EHC. Remain full open until turbine trips.

Question 4

What are the open interlocks for the 2nd Stage Reheat Steam Control Source Valve?

Answer 4

2nd Stage Reheat Steam Control (Main Steam supply)
Reheat Steam Source Valves (RSSVs)

o Open interlocks:
 > 10% load (2/3 PSs)
 RSCV not full closed (1st stage reheat aligned)
 Not in steam blanketing mode

o Auto close:
 < 10% load (2/3 PSs on cross-around piping)
 Steam blanketing mode (AS aligned)
 RSCV closed (1st stage steam supply isolated)

Question 5

Describe the operating characteristics of the 2nd Stage Reheat Steam Low Load Valve (RSLLV) and High Load Valve:

Answer 5

• Reheat Steam** Low Load Valve **(RSLLV)
  o AOV that ramps open from 15 to 65% load to maintain linear pressure change.
  o Based on ∆P between 2nd stage reheat pressure and cross-around pressure.
• Reheat Steam High Load Valve (RSHLV)
  o MOV (Jog HS in MCR)
  o **Auto opens > 65% / closes < 65% load **(based on one PS) to bypass the RSLLV.
   Built-in dead band prevents cycling.

Question 6

What are the interlocks for starting the piggyback motor?

Answer 6

Placing the switch in the START position starts the piggyback motor if the following interlocks are met:
* The main generator circuit breakers or motor operated disconnect are/is open
* A bearing lift pump is running,
* Bearing lube oil pressure is adequate
* The TG is disengaged.
Once the piggyback motor is energized, the TG will engage if the rotor speed is less than 2 rpm and if a low speed permissive signal is generator by the EHC. Once the TG is engaged, the piggyback motor stops and the **slow speed motor **will start.

Question 7

Which lift oil pumps stop when the turbine is placed on the turning gear?

Answer 7

Turning gear operation can pulse the turbine shaft causing it to **speed up and disengage the turning gear. To correct this problem the lift pumps, M-LON-P09 E & H (5&8) **(to Nos. 7 and 10 bearings) have been interlocked such that:
With the following conditions:
* Bearing Oil Lift Pumps handswitch in the Control Room on Panel B06 (HS-50) is in Auto
and,
* The Turning Gear Motor is running and,
* Turbine rotor speed > 2 RPM
then the lift pumps, M-LON-P09 E & H for bearings 7 & 10 will stop.