Main Feed Water 1
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Give the primary and secondary purposes of the feed water system.
- Main Purpose:
- -To deliver feed water to the 4 S/Gs under all expected operating
- conditions at elevated temp and pressure.
- -Pump speed is automatically adjusted to meet system demands to increase feed water pressure sufficient to overcome S/G pressure.
- -To isolate feedwater to the steam generators to prevent
- over-filling during accident conditions.
- Secondary Purpose:
- -Long cycle and short cycle reroutes flow back to the condensers for de-aeration.
- -Short cycle-Protects MFP from deadhead <3500gpm.
- -Long cycle- Initial Filling and venting/cleaning.
State the following system operating parameters: Feed Water Flow:
- aprox. 15 million pph. 100% of the flow.
- 1.) condensate system – 8 million pph. 55.3% of flow
2.) No. 7 Heater Drain Tank – 2 million pph. 13.62% of flow
3.) No.3 Heater Drain Tank – 5 million pph. 31.05% of flow
State the following system parameters: Pressure:
- i.) No load : 1085 psig (1005+80)
- ii.) Full Load: 1027 psig (832+195)
- iii.) draw accompanying graph
State the following system parameters: Temperature:
i.) no load: 120F (No Feedwater Heating)
ii.) full load: 438.1F (All Feedwater Heaters in service)
Give the purpose of the Main Feed Pumps:
- -To deliver feedwater to the 4 S/Gs under all expected operating conditions.
- -Pump speed is automatically adjusted to meet system demands to increase feedwater pressure sufficient enough to overcome S/G pressure.
Give the purpose of the recirculation valves:
Maintain a minumum of 3500gpm for pump protection
Give the purpose of the HP Feed Water Heaters:
Increases the feedwater temp. by about 30 degrees for greater efficiency.
Give the purpose of the LEFM:
- -Leading Edge Flow Monitor
- -Ultrasonic flow meter installed in 2000 to replace venture type flow monitors. Gives a more accurate flow rate which increased power by 1.3%
Give the purpose of the Main Feed Reg. Valves:
- Regulates flow to the S/Gs to maintain level during power
- operations of >15%
Give the purpose of the Bypass Reg. Feed Valves:
Regulates flow to the S/Gs to maintain level during low power operations of <15%
Give the purpose of the Feed Water Isolation Valves:
Shuts the flow off to the S/G due to a FW Isolation signal
Describe the Short and Long Cycle flow paths:
- -Short Cycle: used for pump protection and de-aeration, located right after the MFPs and goes back to condenser A. If the chemistry is ok than the long cycle may be used.
- -Long Cycle: used for de-aeration and recircs back to the main condenser.
Describe the feed water pumps including main components:
- -Type: Double Volute Single Rotor (DVSR), Turbine
- driven, Single Stage, Double suction, centrifigul
- -Capacity: 20,000gpm @ 1680ft TDH
- -Pump Bearings: Axial split Radial and Thrust bearings
- -Turbine driven: Torque from the turbine shaft to the pump delivered by a coupling.
- -Bearing Lubrication: 2 reduntant external AC motor driven pumps.( 1 in service, 1 for back up) MOP. 1 emergency DC pump EOP
- -Shaft Seals: each pump has injection water type stuffing box bushing for shaft seals Injection water pumps: Two High pressure pumps take suction from downstream of the cond DI to provide a cool supply of high quality water to the shaft seals at a sufficiently high pressure to prevent leaking of water from the seals
Explain the high pressure injection water system to the
main feed water pumps:
- To provide relatively cool, high quality H20 for the seals at a high enough pressure to prevent leaking.
- Taken downstream of the cond DI. Water is injected onto both sides of the shaft and flows both toward and away from pump impeller. Leakage from the suction of the pump mixes with the inward flow of injection water and out the intermediate leakoff. then to the no 3 heater drain pump suction line through a back pressure control valve. or through the atmospheric leak off into an atmospheric
List the suction valve interlocks:
- a.) Bearings must have pump lube oil pressure > 10psig,
- turbine lube oil >10psig
b.) Seal Injection Water Pressure > 220psig
c.) Handswitch must be in open position from either the Main Control Room or local panel
Explain the operation of the main feed pump recirc. valves:
Opens when MFP drops below 3500gpm(air operated, fails open) for pump protection. There is a flow orifice to prevent the thinning of pipes.
Describe the main feed pump turbines including major
- Purpose: Provides a variable speed drive for the pumps. 6,000rpm max, 8 stage
- Motor: 17,000 HP . 6,000 rpm maximum
- Rotor 8 stage.
- Turning Gear: 3-5 rpm, reduces the possibility of distortion
- due to uneven heating/cooling
- Turbine Blading
- Thrust Bearing
- Rupture Diaphragm: Protects from over pressurization
- LP Steam Valves: Uses a lifting rod to raise the bar to pull the low pressure valves off their seats in sequence of valve
- stem length.
Describe the steam supplies to the MFP turbines and when each is used:
- HP Steam comes from the mainsteam and LP Steam comes from the moisture separator heaters. Low pressure and High Pressure governor valves operate together. At low power levels, MSR outlet header does not have enough steam pressure. HP steam is used on startup to get the turbine moving. Once enough steam is established (40-50%
- load) the LP sources contributes and the HP governor valve closes and all steam is supplied via the LP governor valve.
Describe the steam seals and supplies for the MFPTs:
The seals are created by using steam at a higher pressure. Labyrinth steam comes in through chambers which expand. After steam goes through the seals it goes to the leak offs. Regulating steam is supplied by the X chamber and leakage steam is removed by the Y chamber by the gland condenser which maintaines a partial vacuum in the chamber and prevents leakage to the atmosphere.
Explain how vacuum is established and maintained in the MFPT Condenser:
1.) Seals are established
2.) The MFPT Cond. Is aligned to the vacuum pumps
3.)Once it reaches 20 in. mercury vacuum, align to the main condenser
- Once vacuum is established via the 4 inch line to the
- condenser vacuum pumps. Valves to the main condenser are opened and the valves to the condenser vacuum pump are closed (in that order)
Describe the MFPT condenser drain system:
Condensers provide a low pressure area for exhaust of steam from the turbine to increase efficiency by getting the maximum amount of work from turbine inlet steam. Steam condenses and drains off into the MFPT Condenser Drain Tank and is injected back into the condensate system. Recirc line goes back to the suction header. 4 air operated valves, 2 LP stop valves and 2 HP stop valves.
Give the MFPT turning gear interlocks:
1.) Lube oil pressure to turbine and pump bearings
2.) the stop valves LP and HP must be fully closed
3.) Turbine Speed <2rpm
4.) Turbine gear motor < temp. set point
Describe the MFPT drains:
Condensate is built up in the pipes and must be drained. 4 air operated valves, 2 per stop valve (1 HP and 1 LP). Keeps water off of the turbine.
- Startup drains: Removes condensate from HP and LP
- steam lines to prevent corrosion. Opened on startup, left open until MT @ 40% load. Left open on shutdown.
Briefly describe the MFP turbine Oil System, and list the 4 subsystems:
- 1.) oil tank cap. 650gal
- 2.) 2 AC main oil pumps, 1 emergency DC pump
- 3.)Routed through a cooler
- 4.)Filters to keep oil clean of debris
- 5.) Vapor exhaust fan pulls vapors out to atmospheres to
- avoid fire hazard
- 1.)Lubrication Oil (turbine and pump bearings)
- 2.)Control oil (to the speed changer)
- 3.)High Pressure (Governor Valve Posistion)
- 4.)Trip Oil System (Isolates steam to the turbine
Describe the speed control program for the main feed pumps:
- Purpose: Controls the speed of the MFP Turbine by maintaining a programmed delta P across the No. 1 feedwater heater. Makes sure there is adequate flow to all 4 S/Gs.
- It uses a summation circuit to compare the DP with the actual DP that is obtained from PT 3-1 on the feedwater side and PT 1-33 on the Main Steam side. Each pump has an associated electric speed changer controller that can run in auto or manual. (draw diagram to show how it receives its signal) *NOTE: in manual, the operator controls the
- DP as desired.
- 1.)Draw Chart
- 2.) Draw print
List the main feed pump trips:
- 1.) Manual
- 2.) low bearing
- oil pressure to both pumps and turbine bearings
- 3.) MFP suction valve not fully open
- 4.) Low injection water pressure
- 5.) Loss of vacuum to MFPT Cond.
- 6.) Thrust bearing wear
- 7.)Feed Water Isolation Signal
Give the purpose of the feedwater flow and temperature
Purpose: measure the flow to each S/G
1.)Feeds the steam generator level control system.
2.)Steam Flow/ Feed Flow mismatch >1,420,000 lbm/hr
3.) Feed Reg Valve Control Logic
4.)Flow Indicator (So unit operators know the flow to the S/Gs and flow recorders)
Explain how the feed water regulating valves and the feed water regulating bypass valves control level in the S/Gs:
Controls the level of the S/G. Level between 33 and 44% to keep from overheating on the primary side. Bypass used on startup to regulate the level until 15% load.
1.)Draw accompanying graph
State the feed water isolation signals and automatic actions which occur when feed water isolation signal is received:
- 1.)High-high S/G level
- 3.)Reactor trip with low Tave
- FW Isolation
- 1.)Feed reg. valves will close
- 2.)Main FW Isolation Valves close
- 3.)MFPs trip
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