Main Condensate & Feed Systems We Love Engineering!

Main Condensate Main Condensate & Feed Systems& Feed Systems

We Love We Love Engineering!Engineering!

ObjectivesObjectives

• Components of Main Condensate Components of Main Condensate System and purposes of eachSystem and purposes of each

• Components of Main Feed System Components of Main Feed System and purposes of eachand purposes of each

• Operation of Automatic Control Operation of Automatic Control SystemsSystems

• Interrelationship of systems during Interrelationship of systems during operationsoperations

Main Condensate Main Condensate SystemSystem

• Provides condensation phase of Provides condensation phase of the main steam cyclethe main steam cycle

• Condenses steam from turbines to Condenses steam from turbines to liquidliquid

• Pumps condensate from main Pumps condensate from main condenser to the Main Feed condenser to the Main Feed SystemSystem

Main Condensate Main Condensate SystemSystem

Main CondenserMain Condenser

• Indirect, shell-and-tube, cross flow Indirect, shell-and-tube, cross flow heat exchangerheat exchanger

• Maintained at vacuum of 25-29” HgMaintained at vacuum of 25-29” Hg– How is the vacuum initiated & How is the vacuum initiated &

maintained?maintained?• Two flow paths through condenserTwo flow paths through condenser• Condensate collects in hotwellCondensate collects in hotwell

– Provides NPSH to condensate pumpsProvides NPSH to condensate pumps

Main CondenserMain Condenser

Main Seawater System Main Seawater System (MSW)(MSW)

• Provides cooling water for main Provides cooling water for main condenser to condense steamcondenser to condense steam

• Scoop Injection SystemScoop Injection System– Used at higher speeds (> 8 knots)Used at higher speeds (> 8 knots)– Uses ship’s speed and scoop to cause Uses ship’s speed and scoop to cause

flowflow– Not on SSN/SSBN’sNot on SSN/SSBN’s

• MSW PumpMSW Pump– Used when going slow or asternUsed when going slow or astern– All SSN/SSBN’sAll SSN/SSBN’s

Main Condensate Main Condensate PumpsPumps

• Centrifugal pumps, either Centrifugal pumps, either steam or electrical power (subs steam or electrical power (subs all electrical)all electrical)

• Usually 2 pumps per condenserUsually 2 pumps per condenser• Check valve on discharge of Check valve on discharge of

pump to prevent backflowpump to prevent backflow• Lowest pressure in MS cycle at Lowest pressure in MS cycle at

suction of pumpssuction of pumps

Condensate DepressionCondensate Depression

• Amount of subcooling of Amount of subcooling of condensate in the hotwell of the condensate in the hotwell of the main condensermain condenser

• If too little (< 2If too little (< 2ooF), then cavitation F), then cavitation of condensate pumps can occurof condensate pumps can occur

• If too much (> 5If too much (> 5ooF), then lose F), then lose efficiency (since condensate must efficiency (since condensate must be reheated later)be reheated later)

• Controlled by regulating MSW flowControlled by regulating MSW flow

Main Feed SystemMain Feed System• PurposePurpose: to deaerate, preheat, store, : to deaerate, preheat, store,

and transport water from DFT to the and transport water from DFT to the boiler or S/Gboiler or S/G

Deaerating Feed Tank Deaerating Feed Tank (DFT)(DFT)

• Preheats feed using 150# Auxiliary SteamPreheats 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)

Deaerating Feed Tank Deaerating Feed Tank (DFT)(DFT)

• OperationOperation– 150# Aux Steam enters in 150# Aux Steam enters in

for heatingfor heating– Condensate sprayed in Condensate sprayed in

thru nozzles (foglike)thru nozzles (foglike)– Baffles collect Baffles collect

condensate/condensed condensate/condensed steam and directed to steam and directed to atomizer assemblyatomizer assembly

– Atomizer uses high-Atomizer uses high-velocity steam to redirect velocity steam to redirect condensate-> remove last condensate-> remove last gases (scrubbing)gases (scrubbing)

More ComponentsMore Components

• Main Feed Booster Pump (MFBP)Main Feed Booster Pump (MFBP)– Single-stage centrifugal pumpSingle-stage centrifugal pump– Provides NPSH to MFPProvides NPSH to MFP

• Main Feed Pump (MFP)Main Feed Pump (MFP)– Multi-stage centrifugal pumpMulti-stage centrifugal pump– Raises feed pressure > S/G pressureRaises feed pressure > S/G pressure

• Feedwater Control ValveFeedwater Control Valve– Regulates quantity of feed flow to S/G Regulates quantity of feed flow to S/G

Makeup-and-Excess Makeup-and-Excess Feed SystemFeed System

• During normal operations, necessary During normal operations, necessary to add/remove water from steam cycleto add/remove water from steam cycle

• System stores feed and provides it if System stores feed and provides it if neededneeded

• DFT level control system provides DFT level control system provides controlcontrol– If level low, make-up feed valve openedIf level low, make-up feed valve opened– If level high, excess feed valve openedIf level high, excess feed valve opened

Makeup-and-Excess Feed Makeup-and-Excess Feed SystemSystem

Automatic Boiler / S/G Automatic Boiler / S/G Level Control System Level Control System

• Uses closed loop feedback Uses closed loop feedback principle of operationprinciple of operation– Measure Measure actual outputactual output– CompareCompare actual output with desired actual output with desired

outputoutput– ComputeCompute necessary correction signal necessary correction signal– Correct Correct actual outputactual output

Automatic Boiler / S/G Automatic Boiler / S/G Level Control SystemLevel Control System

• Automatic Combustion Control (ACC)Automatic Combustion Control (ACC)– Maintains boiler’s steam drum pressure by Maintains boiler’s steam drum pressure by

controlling rate of combustion (air/fuel)controlling rate of combustion (air/fuel)• Feedwater Control System (FCS)Feedwater Control System (FCS)

– Regulates flow of feedwater to boiler to Regulates flow of feedwater to boiler to maintain levelmaintain level

• Diff Control System of MFP (DCS)Diff Control System of MFP (DCS)– Maintains feedwater supply pressure above Maintains feedwater supply pressure above

steam drum pressuresteam drum pressure

Automatic Combustion Automatic Combustion Control (ACC) SystemControl (ACC) System

Feedwater Control Feedwater Control System (FCS)System (FCS)

Differential Control Differential Control System of MFP (DCS)System of MFP (DCS)

Interrelation of Interrelation of SystemsSystems

• Answering AA2/3 -> OOD orders AAIIAnswering AA2/3 -> OOD orders AAII• Open throttles -> steam flow -> Open throttles -> steam flow ->

steam pressure steam pressure • ACC system air & fuel to ACC system air & fuel to

combustion ratecombustion rate• FWC system feed to match steam FWC system feed to match steam

flowflow• DCS of MFP speed of MFP to DCS of MFP speed of MFP to

discharge pressuredischarge pressure

Boiler Chemistry Boiler Chemistry ControlControl

• High temperature water and steam High temperature water and steam at neutral pH can be very corrosiveat neutral pH can be very corrosive

• Holes in pipingHoles in piping• Chemicals are added to the water Chemicals are added to the water

to ensure pH stays low (basic)to ensure pH stays low (basic)• Must analyze for proper levels of these Must analyze for proper levels of these

chemicals to ensure corrosion prevented.chemicals to ensure corrosion prevented.• Can’t have too much – will cause fouling Can’t have too much – will cause fouling

and scale depositsand scale deposits

QuestionsQuestions??