DFWCS

Question 1

What are the different modes of DFWCS?

When do they take affect?

What is main difference?

Answer 1

Low power mode & Hi power mode

Up power - @ 25% switches to Hi power mode
Down power- @ 15% switches to Lo power mode

Hi power compares Lvl setpoint vs. lvl act & stm flow vs. feed flow

Lo power doesn’t use stm & feed flows due to inaccuracies @ low power, instead uses WR S/G lvl

Question 2

What is arbitration? What signals use arbitration in DFWCS?

Answer 2

A method of signal validation for parameters that

• use only two inputs
• use a separate parameter that can infer what monitored parameter should be

Stm flow arbitration sig = Pimp
Fd flow arbitration sig = total error (fw demand)

Question 3

Describe purpose of DFWCS valve linearization and sequencing logic?

What is sequence of valves opening on up power?

Answer 3

Open FRV and bypass valves based on

• flow demand (error)
• valve throttling characteristics (flow,…)
• pressure drop across valve (Psg vs. Pfw)
• BPV opens at low power
• @ 60% BPV position, FRV starts open
• @ 100% BPV position, FRV @ 16%
• BPV starts close, FRV continues open
• @ 30% flow, BPV closed, FRV throttled
• @ 100% flow, FRV position @ 60%

Question 4

How does DFWCS control MFP speed?

Why designed like this?

Answer 4

• program ramp on delta P (Psg vs. Pdisch fwp)
• 74 psid @ 0-20% —>185 psid @ 100% stm flw
• if delta P low, speed of pump increased=> Pfw inc
• if delta P hi, pump speed reduced=> Pfw lowered

@ higher flows, more head losses=>need more d/p to get fw to SG’s
@ lo flows, minimize erosion by lowering d/p

Question 5

Inputs to Hi power mode of DFWCS?

Answer 5

Pimp
   - PT-505A,506A,8 (med select)
   - input to program lvl (old system ramp lvl)
   - arbitrator sig for steam flow
Ls/g
   - LT-517,518,518 (med select)
   - vs. program lvl
Tfw 
   - TT-1189,1190,1191 (med select)
   - temp compensation for lvl error (shrink & swell)
Fstm 
   - FT-512,513 (arbitrated w/ Pimp)
   - vs. Ffw
Ffw
   - FT-510,511 (arbitrated w/ total error)
   - vs. Fstm 
Ps/g
   - PT-514,515,516 (med select)
   - avg of all loops
   - density compensation for steam flow

Question 6

Inputs to Lo power mode of DFWCS

Answer 6

Pimp
   - PT-505A,506A,8 (med select)
   - input to program lvl (old system ramp lvl)
Ls/g (NR)
   - LT-517,518,518 (med select)
   - vs. program lvl
Tfw 
   - TT-1189,1190,1191 (med select)
   - temp compensation for lvl error (shrink & swell)
Ls/g (WR)
   - LT-501
   - anticipatory signal...?

Question 7

Inputs to valve linearization & sequencing logic

Answer 7

Ps/g
   - PT-514,515,516 (med select)
   - all loops averaged
   - vs. Pfw for d/p signal
Pfw
   - PT-508,508A,508B (med select)
   - vs. Ps/g for d/p signal