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Main Condensate & Feed Systems We Love Engineering!

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Presentation on theme: "Main Condensate & Feed Systems We Love Engineering!"— Presentation transcript:

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2 Main Condensate & Feed Systems We Love Engineering!

3 Objectives Components of Main Condensate System and purposes of each Components of Main Condensate System and purposes of each Components of Main Feed System and purposes of each Components of Main Feed System and purposes of each Operation of Automatic Control Systems Operation of Automatic Control Systems Interrelationship of systems during operations Interrelationship of systems during operations

4 Main Condensate System Provides condensation phase of the main steam cycle Provides condensation phase of the main steam cycle Condenses steam from turbines to liquid Condenses steam from turbines to liquid Pumps condensate from main condenser to the Main Feed System Pumps condensate from main condenser to the Main Feed System

5 Main Condensate System

6 Main Condenser Indirect, shell-and-tube, cross flow heat exchanger Indirect, shell-and-tube, cross flow heat exchanger Maintained at vacuum of Hg Maintained at vacuum of Hg – How is the vacuum initiated & maintained? Two flow paths through condenser Two flow paths through condenser Condensate collects in hotwell Condensate collects in hotwell – Provides NPSH to condensate pumps

7 Main Condenser

8 Main Seawater System (MSW) Provides cooling water for main condenser to condense steam Provides cooling water for main condenser to condense steam Scoop Injection System Scoop Injection System – Used at higher speeds (> 8 knots) – Uses ships speed and scoop to cause flow – Not on SSN/SSBNs MSW Pump MSW Pump – Used when going slow or astern – All SSN/SSBNs

9 Main Condensate Pumps Centrifugal pumps, either steam or electrical power (subs all electrical) Centrifugal pumps, either steam or electrical power (subs all electrical) Usually 2 pumps per condenser Usually 2 pumps per condenser Check valve on discharge of pump to prevent backflow Check valve on discharge of pump to prevent backflow Lowest pressure in MS cycle at suction of pumps Lowest pressure in MS cycle at suction of pumps

10 Condensate Depression Amount of subcooling of condensate in the hotwell of the main condenser Amount of subcooling of condensate in the hotwell of the main condenser If too little (< 2 o F), then cavitation of condensate pumps can occur If too little (< 2 o F), then cavitation of condensate pumps can occur If too much (> 5 o F), then lose efficiency (since condensate must be reheated later) If too much (> 5 o F), then lose efficiency (since condensate must be reheated later) Controlled by regulating MSW flow Controlled by regulating MSW flow

11 Main Feed System Purpose: to deaerate, preheat, store, and transport water from DFT to the boiler or S/G Purpose: to deaerate, preheat, store, and transport water from DFT to the boiler or S/G

12 Deaerating Feed Tank (DFT) Preheats feed using 150# Auxiliary Steam Preheats feed using 150# Auxiliary Steam Stores feed (provides NPSH for MFBP) Stores feed (provides NPSH for MFBP) Deaerates feed (removes dissolved air) Deaerates feed (removes dissolved air)

13 Deaerating Feed Tank (DFT) Operation Operation – 150# Aux Steam enters in for heating – Condensate sprayed in thru nozzles (foglike) – Baffles collect condensate/condensed steam and directed to atomizer assembly – Atomizer uses high-velocity steam to redirect condensate-> remove last gases (scrubbing)

14 More Components Main Feed Booster Pump (MFBP) Main Feed Booster Pump (MFBP) – Single-stage centrifugal pump – Provides NPSH to MFP Main Feed Pump (MFP) Main Feed Pump (MFP) – Multi-stage centrifugal pump – Raises feed pressure > S/G pressure Feedwater Control Valve Feedwater Control Valve – Regulates quantity of feed flow to S/G

15 Makeup-and-Excess Feed System During normal operations, necessary to add/remove water from steam cycle During normal operations, necessary to add/remove water from steam cycle System stores feed and provides it if needed System stores feed and provides it if needed DFT level control system provides control DFT level control system provides control – If level low, make-up feed valve opened – If level high, excess feed valve opened

16 Makeup-and-Excess Feed System

17 Automatic Boiler / S/G Level Control System Uses closed loop feedback principle of operation Uses closed loop feedback principle of operation – Measure actual output – Compare actual output with desired output – Compute necessary correction signal – Correct actual output

18 Automatic Boiler / S/G Level Control System Automatic Combustion Control (ACC) Automatic Combustion Control (ACC) – Maintains boilers steam drum pressure by controlling rate of combustion (air/fuel) Feedwater Control System (FCS) Feedwater Control System (FCS) – Regulates flow of feedwater to boiler to maintain level Diff Control System of MFP (DCS) Diff Control System of MFP (DCS) – Maintains feedwater supply pressure above steam drum pressure

19 Automatic Combustion Control (ACC) System

20 Feedwater Control System (FCS)

21 Differential Control System of MFP (DCS)

22 Interrelation of Systems Answering AA2/3 -> OOD orders AAII Answering AA2/3 -> OOD orders AAII Open throttles -> steam flow -> steam pressure Open throttles -> steam flow -> steam pressure ACC system air & fuel to combustion rate ACC system air & fuel to combustion rate FWC system feed to match steam flow FWC system feed to match steam flow DCS of MFP speed of MFP to discharge pressure DCS of MFP speed of MFP to discharge pressure

23 Boiler Chemistry Control High temperature water and steam at neutral pH can be very corrosive High temperature water and steam at neutral pH can be very corrosive Holes in piping Holes in piping Chemicals are added to the water to ensure pH stays low (basic) Chemicals are added to the water to ensure pH stays low (basic) Must analyze for proper levels of these chemicals to ensure corrosion prevented. Must analyze for proper levels of these chemicals to ensure corrosion prevented. Cant have too much – will cause fouling and scale deposits Cant have too much – will cause fouling and scale deposits

24 Questions?


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