1. What is the function of the feedwater system?
    To provide deareated and chemically treated feedwater to the plants� boilers, to be converted to steam, at 100-150 psi over steam drum pressure.
  2. Feedwater pump
    • * Function: To receive water from the DFT and pump it thru to the steam drum at approximately 800 psi.
    • * Location: Southeast end of the basement between the surge tank and sump.
    • * Safety/Protective Devices: #1 MFP has air vents to keep from blowing out the seals during startup. #3 & #4 are protected electrically by local disconnects in the basement. Each pump also has check valves to prevent backflow and a water recirculation system to prevent over pressurization.
    • * Failure indications: Loss of feedwater flow to the boiler.
  3. Economizer
    • * Function: To receive feedwater from the MFP and add exhaust stack BTU�s to it prior to the water entering the steam drum.
    • * Location: In the exhaust stack of each boiler
    • * Safety/Protective Devices: #2 Economizer relief lifts at 750 psi. #2 Economizer can also be bypassed. #1 and #3 Economizer have no relief or bypass.
    • * Failure indications: No change in feedwater in/out temperature leading to potentially low drum temperature.
  4. Deaerating feed tank:
    • * Function: Deareate the feedwater, preheat the feedwater, provide a reservoir for the feedwater, provide NPSH to the MFP.
    • * Location: South end of the building, east of the control room, two levels.
    • * Safety/Protective Devices: Relief valve lifts at 20 psi, and vacuum breaker check valve.
    • * Failure indications: Loss of NPSH to the pumps causing audible cavitation or low feedwater trip at about 600 psi. Water hammer. Shell pressure rising or falling out of the 2-5 psi range. Water flow out of the vent.

    • Automatic feedwater control valve:
    • * Function: Control the flow of feedwater from the header into the economizer in sync with the boilers demand.
    • * Location: Boiler deck east wall for #1 and #2, south side of #3.
    • * Failure indications: Erratic flow that doesn�t match up with the boiler load.
  5. Feedwater pump bearings:
    • * Function: Support the pump shaft.
    • * Location: Inboard and Outboard ends of the shaft
    • * Failure indications: Hot oil, metal shavings in oil sample, shaft seizure
  6. Feedwater pump re-circulating line:
    • * Function: Direct excess feedwater back to the lower half of the DFT or to the Surge Tank.
    • * Location: On the discharge line of each pump.
    • * Failure indications: Over or under pressure at the gage. Unnatural throttling of the Automatic Feedwater valve.
  7. Feedwater pump vent line:
    • * Function: Release trapped air in the pump casing and direct it to the upper half of the DFT.
    • * Location: Top of the casing on #1 MFP
    • * Failure indications: Blown seals at startup.
  8. In-line desuperheater pump:
    • * Function: To provide deareated feedwater from the suction header to the desuperheaters.
    • * Location: Three pumps at the South end of the basement next to the condensate transfer pumps.
    • * Safety/Protective Devices: VFD controlled, automatic switching at or about 0700 daily.
    • * Failure indications: Loss of feed to desuperheaters showing a drastic rise in the 80# steam to campus temperature.
  9. Chemical injection:
    • * Function: To treat the feedwater chemically in order to control oxygen content, alkalinity, and turbidity.
    • * Location: Suction Header and DFT
    • * Failure indications: Out of spec results on the S03, OH Alkalinity, or SP531 tests on the boiler water.
  10. Feedwater flow indication:
    • * Function: Monitor the total flow of feedwater into the economizer.
    • * Location: Control room computer screens.
    • * Failure indications: No indication or inaccurate indication on the screen.
  11. Pressure gauge:
    • * Function: Show pressure at a specific location.
    • * Location: Suction and Discharge
    • * Failure indications: Obviously false readings.
  12. Economizer bypass valve:
    • * Function: To allow feedwater to bypass the #2 economizer and dump straight into the steam drum. It is chained in the shut position.
    • * Location: #2 Economizer
    • * Failure indications: High water level in the steam drum if the valve is leaking by and lowered temperature since the water would not be entering the economizer.
  13. Sample cooler:
    • * Function: To allow the safe sampling of cooled feedwater to ensure that chemical treatments are working.
    • * Location: Basement, co-located with the desuperheater pumps.
    • * Failure indications: No sample, sample is too hot to handle, or the sample readings are obviously off when compared to other tests/trends.
  14. Automatic feedwater control valve bypass:
    • * Function: To allow feedwater flow around the Automatic Feedwater Control Valve.
    • * Location: At each feedwater station for each boiler.
    • * Failure indications: Valves open and no-flow or valves shut and leakby.
  15. Desuperheater feed:
    • * Function: Provide redundancy in the system to allow us to continue feeding the desuperheaters in the event of the pump station failing.
    • * Location: There is a line off the feedwater discharge header that leads to the #1 & 2 desuperheaters. This line is cross connected (2 isolation valves) with the discharge line from the DSPumps. Additionally there is another line just before the #3 Boiler that goes to the Thompson Tunnel inline DS. That line also cross connects with a discharge line from #3 RO Booster pump. This creates a complete loop and allows all desuperheaters to be directly fed without the DSPumps if needed.
    • * Failure indications: Loss of feedwater pressure, elevated 80# temperatures at the tunnels.
  16. How do the components work together to achieve the system's function?
    Deareated and chemically treated water flows from the bottom of the DFT thru the suction header to the suction side of the MFP. The pump increases the pressure and it flows out the discharge into another header where it is metered by the Automatic Feedwater Control Valve. The water travels thru an orifice plate where the pressure/flow is measured. After travelling thru the Economizer the water is heated an additional 100�F (approximately) and dumped into the steam drum.
  17. Where are the start/stop motor controllers for the feedwater pumps?
    #1, 3, & 4 are soft starts and are located in the switchgear room. #2 is started via the VFD located just east of the south ladderwell.
  18. Describe the procedure for starting, operating and securing the feedwater pump.
    In general: Open the vents and recirculation lines. Open the suction and discharge valves. Warm up the casing to a uniform temperature approximating the feedwater temp. Close the warming valves. The Lead Operator will then issue the start command from the switchgear room or the VFD while the B-Operator is standing by to visually verify a good start. In all cases consult the control room procedures for the specific pump prior to the evolution.
  19. Explain the basic operation of the VFD as applied to the feedwater system.
    #2 MFP is the only one on a VFD. You issue a start command in "auto". The VFD will control the pump based on a setpoint (pressure).
  20. Feedwater pump suction pressure:
    • * Normal Operating Values? 12-20 psi
    • * Parameters Sensed/Monitored? At the pump and in the control room.
    • * Physical Location - Indicators? Gage is located at the suction line
  21. Feedwater pump discharge pressure:
    • * Normal Operating Values?700-800 psi
    • * Parameters Sensed/Monitored? At the pump and in the control room.
    • * Physical Location - Indicators? Gage is located at the discharge line
    • * Alarm Setpoint? About 650 psi depending on which boiler we are talking about.
  22. Economizer inlet feedwater temperature:
    • * Normal Operating Values? 220 �F
    • * Parameters Sensed/Monitored? Control Room
    • * Physical Location - Indicators? Control Room Computers, Instrument tree at economizer
  23. Economizer outlet feedwater temperature:
    • * Normal Operating Values?320 �F
    • * Parameters Sensed/Monitored? Control Room
    • * Physical Location - Indicators? Control Room Computers, Instrument tree at economizer
  24. In-line desuperheater pump discharge pressure:
    • * Normal Operating Values?150-160 psi
    • * Parameters Sensed/Monitored? Control Room (Steam � Desup screen). Additionally there are pressure gages at the pumping station.
    • * Physical Location - Indicators? Gages on the pump station and a VFD that is co-located.
  25. DFT water level:
    • * Normal Operating Values? 67� to 81� It tends to stay in the 70-71� range typically.
    • * Parameters Sensed/Monitored? Control Room or at equipment sight glass.
    • * Physical Location - Indicators? Sight glass is on the bottom level on the east end. The level transmitter is at the floor on the bottom level east end.
    • * Alarm Setpoint? 81�
  26. Main feed pump GPM & lb/hr (capacity max):
    • * Normal Operating Values?
    • #1 MFP 500 gpm/249900 lb/hr -- (500*8.33)*60#2 MFP 400 gpm/199920 lb/hr -- (400*8.33)*60#3 MFP 450 gpm/224910 lb/hr -- (450*8.33)*60#4 MFP 140 gpm/69972 lb/hr -- (140*8.33)*60* Parameters Sensed/Monitored? Control Room Screens DA/FW, Key, and the boiler screens.
    • * Physical Location � Indicators? There is an instrument tree with a pressure and flow transmitter close to the feedwater station for each boiler. They are connected to the orifice plate located between the Automatic Feedwater Control Valve and the Economizer inlet.
  27. Desuperheater feed flow:
    • * Normal Operating Values? Around 80% of the 53 gpm spec as shown on the VFD
    • * Parameters Sensed/Monitored? Flow is seen at the VFD.
    • * Physical Location - Indicators? DSPump station VFD.
    • * Alarm Setpoint? There is no alarm on the Control Room Screens to indicate loss of flow. Instead we�ll get a temp alarm on the desuperheaters.
    • o High de-superheater temperature audible alarm# 1 will go at 360F.
    • o High de-superheater temperature audible alarm # 2 will go at 375F.
    • o Low desuperheater temperature audible alarm at 325F.
  28. Explain How Variations in boiler pressure affect this system:
    The harder the boiler is firing the higher the minimum output pressure will have to be in order for the water to make it thru the economizer and into the steam drum.
  29. Explain How Variations in boiler water level affect this system:
    The steam drum water level directly determines how wide open the feedwater control valve has to be in order to ensure an adequate supply.
  30. Explain How Variations in DFT water level affect this system:
    The level in the DFT determines the amount of Net Positive Suction Head (NPSH) available to the pump or pumps at the suction side.
  31. Explain How Variations in DFT pressure affect this system:
    The pressure plus water level directly determine the NPSH available at the pumps.
  32. Explain How Variations in cogeneration steam supply affect this system:
    The more steam cogen is putting out, the less we have to. This can reduce the demand on the system since the boiler load won�t be as high. Also, the amount of condensate we send cogen can affect the DFT and available water to the pumps.
  33. Explain how this system interfaces with the Condensate system:
    • Part of the recirculation water goes to the surge tank.
    • The MFP suction header can also be aligned to the discharge of the Condensate XFER Pumps in order to bypass the DFT.
  34. Explain how this system interfaces with the Boiler system:
    The feedwater system is the source of supply for the boiler.
  35. Explain how this system interfaces with the Condenser water system:
    Condenser water is used to cool the #2 and #3 MFP.
  36. Explain how this system interfaces with the Desuperheater feed system:
    The Desuperheater Pumps take suction from the MFP Suction Header. The main feed line, under the boiler deck grating, sends a direct line to the desups as well tying in with the DSPumps discharge. The main feed line, under the boiler deck grating closer to #3 Boiler, sends a direct line which links up the #3 DS at Thompson Tunnel. The Thompson Tunnel line also loops back into the original DSPump discharge.
  37. What safety precautions apply to this system?
    Tag out per PP/OP 08.01 due to electrical shock, water pressure, and water temperature hazards. Allow the system to completely cool before working. Open / close valves gradually to avoid hammering the pipes. Use caution when venting/draining during the tag out.
  38. Discuss possible casualties / causality control procedures that pertain to this system?
    • * High Boiler Water Level (page 1 of Casualty pocket guide)
    • * Low Boiler Water Level (page 3 of Casualty pocket guide)
    • * Loss Of Main Feedwater Control (page 13 of Casualty pocket guide)
    • * Low DFT Water Level (page 19 of Casualty pocket guide)
    • * Loss Of Electrical Power (page 37 of Casualty pocket guide)
    • * Loss of Main Feed Pump
    • o Hot bearing
    • o Breaker/Switchgear malfunction
    • o Low or no oil
    • o Loss of Condenser water cooling.
  39. Draw The System
    Image Upload 2
Card Set
Feedwater Systems Checkout for UPOII