Download - Nalco Cooling Tower Presentation
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Nalco CompanyCooling Water Presentation 6-24-04
Stress Management for Cooling Systems
TVWD Cooling Tower TVWD Cooling Tower Seminar and WorkshopSeminar and Workshop
November 29, 2005November 29, 2005
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AgendaAgenda
IntroductionIntroductionFundamentals of Cooling WaterFundamentals of Cooling WaterCooling System Problems (Stresses)Cooling System Problems (Stresses)Treatment ProgramsTreatment ProgramsThe Engineering ApproachThe Engineering ApproachMicrobiological Control and Microbiological Control and MonitoringMonitoringStress ManagementStress Management
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The purpose of cooling The purpose of cooling systems is to transfer systems is to transfer heat from one substance heat from one substance to anotherto anotherThe substance that The substance that gives up its heat is gives up its heat is ““cooledcooled””The substance that The substance that receives the heat is the receives the heat is the ““coolantcoolant””
THE COOLING PROCESS
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Open Recirculating SystemsOpen Recirculating Systems
Open recirculating systems are open to the atmosphere Open recirculating systems are open to the atmosphere at the tower. As the water flows over the tower, heat at the tower. As the water flows over the tower, heat picked up by the process is released by evaporation. picked up by the process is released by evaporation.
The cooling water then returns to the heat exchangers The cooling water then returns to the heat exchangers to pick up more heat.to pick up more heat.
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Open Recirculating SystemOpen Recirculating SystemMakeupWater
Pump
Blowdown
EXAMPLESSpray PondsCooling TowersEvaporative Condensers
CHARACTERISTICSAvg. Temp. Change: 20-30°F [11.1-16.7°C]Amount of Water Used: Moderate
Heat Exchanger
Cooling Tower
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Open Recirculating SystemsOpen Recirculating Systems
Heat TransferHeat TransferProcess in which heat Process in which heat is transferred from is transferred from one substance to one substance to another.another.
EvaporationEvaporationProcess by which Process by which the hot cooling the hot cooling water releases its water releases its heat to the heat to the atmosphere so atmosphere so that it can return that it can return cool water back to cool water back to the heat the heat exchangersexchangers
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Open Recirculating SystemsOpen Recirculating Systems
A cooling tower provides two conditions A cooling tower provides two conditions that enhance the evaporation process...that enhance the evaporation process...
Break water into tiny droplets, thus Break water into tiny droplets, thus providing more escape routes for water providing more escape routes for water molecules to evaporate.molecules to evaporate.Fans provide rapid flow of air through Fans provide rapid flow of air through the tower which removes evaporated the tower which removes evaporated water molecules and allows even more to water molecules and allows even more to escape.escape.
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Why Use Water for Cooling?Why Use Water for Cooling?
Plentiful; Readily Available; CheapPlentiful; Readily Available; CheapEasily Handled: Easily Handled: PumpablePumpableCan carry large amounts of heatCan carry large amounts of heatDoes not expand/contract much at Does not expand/contract much at normally encountered temperaturesnormally encountered temperaturesDoes not decomposeDoes not decompose
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Why Use Water for Cooling?Why Use Water for Cooling?
Specific Heat: Measure of how well Specific Heat: Measure of how well a substance absorbs heata substance absorbs heatWater can absorb more heat than Water can absorb more heat than virtually any other substance that virtually any other substance that would be considered for industrial would be considered for industrial coolingcoolingMinor increases in temperatureMinor increases in temperatureMinimal environmental impactMinimal environmental impact
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Why IsnWhy Isn’’t Water Perfect for t Water Perfect for Cooling?Cooling?
Dissolves everything it touches: Dissolves everything it touches: Metal; earth; stone; gassesMetal; earth; stone; gassesUnique dissolving ability has earned Unique dissolving ability has earned water the title...water the title...
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Two Sources of WaterTwo Sources of WaterSurface WaterSurface Water
Low in dissolved solidsLow in dissolved solidsHigh in suspended solidsHigh in suspended solidsQuality changes quickly with seasons & weatherQuality changes quickly with seasons & weather
Ground WaterGround WaterHigh in dissolved solidsHigh in dissolved solidsLow in suspended solidsLow in suspended solidsHigh in iron & manganeseHigh in iron & manganeseLow in oxygen, may contain sulfide gasLow in oxygen, may contain sulfide gasRelatively constant quality & temperatureRelatively constant quality & temperature
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What Chemical Properties of What Chemical Properties of Water Are Important?Water Are Important?
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Important Properties of WaterImportant Properties of Water
1. Conductivity1. Conductivity2. Hardness2. Hardness3. Alkalinity3. Alkalinity4. pH4. pH5. Silica 5. Silica 6. Other impurities6. Other impurities
---- Iron, Manganese,Iron, Manganese,Chlorides, Phosphate, etc.Chlorides, Phosphate, etc.
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EvaporationEvaporation
Each 10Each 10°°F [6F [6°°C] drop in temperature results C] drop in temperature results in an avg. 0.85% evaporation of in an avg. 0.85% evaporation of
recirculated cooling waterrecirculated cooling waterER = (RR)*(dT/10)*(.0085)ER = (RR)*(dT/10)*(.0085)
WhereWhere::ER: Evaporation Rate [gpm]ER: Evaporation Rate [gpm]RR:RR: Recirculation Rate [gpm]Recirculation Rate [gpm]dT:dT: Temp drop across tower [DegF]Temp drop across tower [DegF]
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Concentration of Dissolved Concentration of Dissolved SolidsSolids
Only pure water can evaporateOnly pure water can evaporate–– Excluding volatile chemicals Excluding volatile chemicals
like bleachlike bleachNo dissolved solids leave the No dissolved solids leave the liquid waterliquid waterIf there are no other water If there are no other water losses from the system, the losses from the system, the evaporation process causes an evaporation process causes an increase in the concentration increase in the concentration of dissolved solids in the of dissolved solids in the recirculating cooling water.recirculating cooling water.
6
1
32
54
ConstantEvaporation
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Concentration of Dissolved Concentration of Dissolved SolidsSolids
Mineral scale will form if the Mineral scale will form if the dissolved solids concentration in the dissolved solids concentration in the cooling water becomes too highcooling water becomes too highSupersaturationSupersaturation
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Impact of Blowdown onImpact of Blowdown onConcentration RatioConcentration Ratio
Blowdown:Blowdown:Deliberate Deliberate discharge of discharge of water to prevent water to prevent the dissolved the dissolved solids from solids from getting to highgetting to high
6
1
32
54
Constant Evaporation
6
32
54
Constant Evaporation
1
WithZeroBlowdown
With Continuous BlowdownMaintaining 4 Cycles
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Makeup WaterMakeup Water
Amount of water Amount of water required to required to replace water lost replace water lost by evaporation by evaporation and blowdownand blowdown
Evaporation
Makeup
Blowdown
Makeup = Evaporation +
Blowdown
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Concentration RatioConcentration Ratio
CR = Make-up Flow
Blowdown Flow
MU = Evaporation xCR
(CR – 1)
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COMMON COOLINGCOMMON COOLINGSYSTEM PROBLEMSSYSTEM PROBLEMS
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CORROSION
MICROBIO
FOULINGSCAL
E
Cooling System ProblemsCooling System Problems
Left unchecked these Left unchecked these problems causeproblems cause
Loss of heat transferLoss of heat transferReduced equipment Reduced equipment lifelifeEquipment failuresEquipment failuresLost productionLost productionLost profitsLost profitsIncreased Increased maintenance costsmaintenance costsPlant shutdownPlant shutdown
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MINERAL SCALEMINERAL SCALE
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Mineral ScaleMineral Scale
Cooling Water contains many Cooling Water contains many different minerals different minerals ---- normally these normally these minerals are dissolved in the waterminerals are dissolved in the waterUnder certain conditions minerals Under certain conditions minerals can come out of solution and form can come out of solution and form into hard, dense crystals called into hard, dense crystals called SCALESCALE
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Scaled Heat Exchanger Tubes
Mineral ScaleMineral Scale
Common ScalesCommon ScalesCalcium CarbonateCalcium CarbonateMagnesium SilicateMagnesium SilicateCalcium PhosphateCalcium PhosphateCalcium SulfateCalcium SulfateIron OxideIron OxideIron PhosphateIron PhosphateOthers...Others...
CaPO4
CaCO3
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Mineral ScaleMineral Scale
The Following Factors AffectThe Following Factors AffectScale Formation...Scale Formation...
Mineral ConcentrationMineral ConcentrationWater TemperatureWater TemperatureWater pHWater pHSuspended SolidsSuspended SolidsWater Flow VelocityWater Flow Velocity
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Mineral ScaleMineral Scale
Scale usually forms in hot areas of Scale usually forms in hot areas of cooling systemscooling systemsReduces heat transfer efficiencyReduces heat transfer efficiencyMechanical/Chemical cleaningMechanical/Chemical cleaningUnder deposit corrosion (pitting)Under deposit corrosion (pitting)Plant shutdownPlant shutdownEquipment replacementEquipment replacement
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Preventing Mineral ScalePreventing Mineral Scale
Limit concentration of scale forming Limit concentration of scale forming minerals: Blowdown, clarify/filter MUminerals: Blowdown, clarify/filter MUFeed acid to reduce pH & alkalinity: Feed acid to reduce pH & alkalinity: Reduces scaling Reduces scaling ---- increases corrosionincreases corrosionMechanical design changes: Increase HX Mechanical design changes: Increase HX water velocity, water velocity, backflushbackflush, air rumble , air rumble Apply chemical scale inhibitorsApply chemical scale inhibitors
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Mineral ScaleMineral ScaleThree Classifications Of ScaleThree Classifications Of Scale
Inhibiting Chemicals AreInhibiting Chemicals Are……
Crystal ModifiersCrystal Modifiers–– Prevent scale from Prevent scale from ““laying downlaying down””
SequestrantsSequestrants–– Prevent scale from agglomeratingPrevent scale from agglomerating
DispersantsDispersants–– Affect mineral charge so that scale Affect mineral charge so that scale
formers repel each otherformers repel each other
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Normal OperationsNormal Operations
Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.4 1.3 3.9 10.9 29 68 96 pHTricalcium Phosphate 1 1 1 1 1 1 1 Temp 120Magnesium Silicate 0.1 0.3 1 3.2 10 28 72 PO4 2Silica 0.6 0.6 0.55 0.53 0.5 0.44 0.36 Cycles 8
Comments:
Parameters 6 7 8 9 10 11 12Calcite 6 6.5 7 7.4 7.7 8 8.3 pH 8.3Tricalcium Phosphate 1 1 1 1 1 1 1 Temp 120Magnesium Silicate 1.3 1.6 2.1 2.5 3 3.5 0.8 PO4 2Silica 0.4 0.5 0.55 0.6 0.7 0.75 0.8 Cycles
Constants
Impact of pHConstants
Impact of Cycles
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PGE Beaver Condenser Scale AnalysisPGE Beaver Condenser Scale Analysis
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Calcium Carbonate ScaleCalcium Carbonate Scale
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High Silica, Minimum BlowdownHigh Silica, Minimum Blowdown
Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.67 1.9 5.5 15 38 89 187 pHTricalcium Phosphate 1 1 1 1 1 11 1 Temp 120Magnesium Silicate 0.2 0.8 2.8 9 28 81 203 PO4 2Silica 1.08 1.07 1.05 1 0.9 0.8 0.7 Cycles 15
Comments: 15 cycles, 230 PPM Silica
Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.4 1 3 9 24 60 136 pHTricalcium Phosphate 1 1 1 1 1 11 1 Temp 80Magnesium Silicate 0.1 0.1 0.3 1.1 3.6 11 31 PO4 2Silica 1.8 1.8 1.8 1.78 1.73 1.64 1.5 Cycles 15
Comments: 15 cycles, 230 PPM Silica
Impact of pH and High SilicaConstants
Impact of pH and High SilicaConstants
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CORROSIONCORROSION
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CORROSIONCORROSION
Corrosion is the mechanism by which metals Corrosion is the mechanism by which metals are reverted back toare reverted back to
their their naturalnatural ““oxidizedoxidized”” statestate
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Battery AnalogyBattery AnalogyAnodeAnodeCathodeCathodeElectrical CircuitElectrical CircuitMetal lost at anodeMetal lost at anode
CorrosionCorrosion
e -
Electrolyte
Ano
de
Cat
hode
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Simplified Corrosion CellSimplified Corrosion Cell
Fe 2+
CATHODE
ANODE
O2
OH-
e-
STEP 1
STEP 2
STEP 3
STEP 4
Water withDissolvedMinerals
Base Metal
O2
e-e- e-
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Four Step Corrosion ModelFour Step Corrosion Model
Step 1Step 1: At the anode, pure iron begins to break : At the anode, pure iron begins to break down in contact with the cooling water. This down in contact with the cooling water. This step leaves behind electrons.step leaves behind electrons.Step 2Step 2: Electrons travel through the metal to the : Electrons travel through the metal to the cathode.cathode.Step 3Step 3: At the cathode, a chemical reaction : At the cathode, a chemical reaction occurs between the electrons and oxygen carried occurs between the electrons and oxygen carried by the cooling water. This reaction forms by the cooling water. This reaction forms hydroxide.hydroxide.Step 4Step 4: Dissolved minerals in the cooling water : Dissolved minerals in the cooling water complete the electrochemical circuit back to the complete the electrochemical circuit back to the anode.anode.
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Factors Influencing CorrosionFactors Influencing Corrosion
pHpHTemperatureTemperatureDissolved SolidsDissolved SolidsSystem DepositsSystem DepositsWater VelocityWater VelocityMicrobiological GrowthMicrobiological Growth
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100
10
05 6 7 8 9 10
Cor
rosi
on R
ate,
Rel
ativ
e U
nits
pH
Corrosion Vs. pHCorrosion Vs. pH
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Corrosion Vs. TemperatureCorrosion Vs. Temperature
Corrosion Rate
Tem
pera
ture
In general, for every 18°F in water temperature, chemical reaction rates double.
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Other Causes of CorrosionOther Causes of Corrosion
System DepositsSystem Deposits•• Anodic pitting sites develop under depositsAnodic pitting sites develop under deposits
Water VelocityWater Velocity•• Too low = depositsToo low = deposits•• Too high = ErosionToo high = Erosion
Microbiological GrowthMicrobiological Growth•• Deposits; Produce corrosive byDeposits; Produce corrosive by--productsproducts
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Types of CorrosionTypes of Corrosion
All cooling system metallurgy experiences some All cooling system metallurgy experiences some degree of corrosion. The objective is to control degree of corrosion. The objective is to control the corrosion well enough to maximize the life the corrosion well enough to maximize the life
expectancy of the system...expectancy of the system...
1. General Corrosion1. General Corrosion2. Localized Pitting Corrosion2. Localized Pitting Corrosion3. Galvanic Corrosion3. Galvanic Corrosion
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Base Metal
General Etch Uniform Attack
Water
Original
Thickness
General CorrosionGeneral Corrosion
Preferred situationPreferred situationTake a small Take a small amount of metal amount of metal evenly throughout evenly throughout the systemthe systemAnode very largeAnode very large
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Base Metal
Localized Pitting Attack
WaterOriginal
Thickness
Pitting CorrosionPitting Corrosion
Metal removed at Metal removed at same rate but from a same rate but from a much smaller areamuch smaller areaAnode very smallAnode very smallOften occurs under Often occurs under deposits or weak deposits or weak pointspointsLeads to rapid metal Leads to rapid metal failurefailure
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Galvanic CorrosionGalvanic CorrosionActive End
Passive End
MagnesiumGalvanized SteelMild SteelCast Iron18-8 Stainless Steel Type 304 (Active)18-12-3 Stainless Type 316 (Active)Lead TinMuntz SteelNickel (Active)76-Ni-16 Cr-7 Fe Alloy (Active)BrassCopper70:30 Cupro Nickel67-Ni-33 Cu Alloy (Monel)Titanium18-8 Stainless Steel Typ 304 (Passive)18-12-3 Stainless Steel Type 316 (Passive)GraphiteGoldPlatinum
Occurs when two Occurs when two different metals different metals are in the same are in the same systemsystemMore reactive More reactive metal will corrode metal will corrode in presence of less in presence of less reactive metalreactive metalPotential for Potential for galvanic corrosion galvanic corrosion increases with increases with increasing distance increasing distance on charton chart
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Affects of CorrosionAffects of Corrosion
Destroys cooling system metalDestroys cooling system metalCorrosion product deposits in heat exchangersCorrosion product deposits in heat exchangersHeat transfer efficiency is reduced by depositsHeat transfer efficiency is reduced by depositsLeaks in equipment developLeaks in equipment developProcess side and water side contamination Process side and water side contamination occursoccursWater usage increasesWater usage increasesMaintenance and cleaning frequency increasesMaintenance and cleaning frequency increasesEquipment must be repaired and/or repairedEquipment must be repaired and/or repairedUnscheduled shutdown of plantUnscheduled shutdown of plant
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Methods To Control CorrosionMethods To Control Corrosion
Use corrosion resistant alloys: $Use corrosion resistant alloys: $Adjust (increase) system pH: ScaleAdjust (increase) system pH: ScaleApply protective coatings: IntegrityApply protective coatings: IntegrityUse Use ““sacrificial anodessacrificial anodes””: Zn/Mg: Zn/MgApply chemical corrosionApply chemical corrosioninhibitorsinhibitors
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Anodic Corrosion InhibitorsAnodic Corrosion Inhibitors
Stop corrosion Stop corrosion cell by blocking cell by blocking the anodic sitethe anodic siteSevere localized Severe localized pitting attack can pitting attack can occur at an occur at an unprotected unprotected anodic sites if anodic sites if insufficient insufficient inhibitor is inhibitor is presentpresent
Anodic InhibitorsAnodic InhibitorsChromatesChromatesNitritesNitritesOrthophosphatesOrthophosphatesSilicatesSilicatesMolybdatesMolybdates
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Cathodic Corrosion InhibitorsCathodic Corrosion Inhibitors
Stop corrosion cell Stop corrosion cell by blocking the by blocking the electrochemical electrochemical reaction at the reaction at the cathodecathodeCorrosion rate is Corrosion rate is reduced in direct reduced in direct proportion to the proportion to the reduction in the size reduction in the size of the cathodic area.of the cathodic area.
Cathodic InhibitorsCathodic InhibitorsBicarbonatesBicarbonatesPolyphosphatesPolyphosphatesPolysilicatesPolysilicatesZincZincPSOPSO
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General Corrosion InhibitorsGeneral Corrosion Inhibitors
Protect metal by Protect metal by filming all filming all surfaces whether surfaces whether they are anodic or they are anodic or cathodiccathodic
General InhibitorsGeneral InhibitorsSoluble OilsSoluble OilsTolyltriazolesTolyltriazolesBenzotriazolesBenzotriazoles
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Nalco Corrosion MonitorNalco Corrosion Monitor
Linear Polarization Resistance (LPR)Linear Polarization Resistance (LPR)Effective in Low Conductivity Waters Effective in Low Conductivity Waters ––Soft Water, CondensateSoft Water, CondensateProbes and Tips are one unitProbes and Tips are one unitBattery PoweredBattery PoweredInternal Data Logger Internal Data Logger –– PDA/Computer PDA/Computer Down LoadDown LoadInexpensiveInexpensive
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Unit 2 NCM 100 Data
0.00
0.50
1.00
1.50
2.00
2.50
4-Sep 6-Sep 8-Sep 10-Sep 12-Sep 14-Sep 16-Sep 18-Sep 20-Sep
Date
M P
Y
Start Trial
Chlorine Shock Normal Operations
Startup
Unit 2 Circ Water Corrosion Rates
9/6/03 to 9/17/03
Unit Shutdown
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FOULINGFOULING
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FoulingFouling
FOULING is the accumulation of solid FOULING is the accumulation of solid material, other than scale, in a way that material, other than scale, in a way that hampers the operation of equipment or hampers the operation of equipment or
contributes to its deteriorationcontributes to its deterioration
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Common FoulantsCommon FoulantsSuspended SolidsSuspended Solids
Silt, Sand, Mud and IronSilt, Sand, Mud and IronDirt & DustDirt & DustProcess contaminants, e.g. OilsProcess contaminants, e.g. OilsCorrosion ProductsCorrosion ProductsMicrobio growthMicrobio growthCarryover (clarifier/lime softener)Carryover (clarifier/lime softener)
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Water CharacteristicsWater CharacteristicsWater TemperatureWater TemperatureWater Flow VelocityWater Flow VelocityMicrobio GrowthMicrobio GrowthCorrosionCorrosionProcess LeaksProcess Leaks
Factors Influencing FoulingFactors Influencing Fouling
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Affects of FoulingAffects of Fouling
Foulants form deposits in hot and/or low Foulants form deposits in hot and/or low flow areas of cooling systemsflow areas of cooling systemsShellShell--side heat exchangers are the most side heat exchangers are the most vulnerable to foulingvulnerable to foulingDeposits ideal for localized pitting Deposits ideal for localized pitting corrosioncorrosionCorrosive bacteria thrive under depositsCorrosive bacteria thrive under depositsMetal failure resultsMetal failure results
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Economic Impact of FoulingEconomic Impact of Fouling
Decreased plant efficiencyDecreased plant efficiencyReduction in productivityReduction in productivityProduction schedule delaysProduction schedule delaysIncreased downtime for maintenanceIncreased downtime for maintenanceCost of equipment repair or replacementCost of equipment repair or replacementReduced effectiveness ofReduced effectiveness ofchemical inhibitorschemical inhibitors
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FoulingFouling
Three Levels Of Attack Can Be Three Levels Of Attack Can Be Employed To Address The Effects Employed To Address The Effects
Of Fouling...Of Fouling...
1. Prevention1. Prevention2. Reduction2. Reduction3. Ongoing Control3. Ongoing Control
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Preventing FoulingPreventing Fouling
PreventionPreventionGood control of makeup qualityGood control of makeup qualityGood control of corrosion, scale, & microbioGood control of corrosion, scale, & microbio
ReductionReductionIncrease blowdownIncrease blowdownSidestream filterSidestream filter
Ongoing ControlOngoing ControlBackflushing, Air rumbling, Clean tower basinBackflushing, Air rumbling, Clean tower basinChemical treatmentChemical treatment
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Preventing FoulingPreventing Fouling
PreventionPreventionHigh Efficiency Multimedia FiltersHigh Efficiency Multimedia Filters–– Capable of 80% removal of 0.5 micronCapable of 80% removal of 0.5 micron–– Typical multimedia depth filters capable of Typical multimedia depth filters capable of
80% removal only down to 10 micron80% removal only down to 10 micron–– Most (greater than 90%) of particles found in Most (greater than 90%) of particles found in
a cooling tower are less than 10 microna cooling tower are less than 10 micron
Do not overlook Do not overlook sidestream sidestream filtration and filtration and choose wisely!choose wisely!
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FoulingFoulingChemical TreatmentChemical Treatment
Charge Charge ReinforcersReinforcers–– Anionic polymers increase strength of Anionic polymers increase strength of
charge already present on suspended charge already present on suspended solidssolids
–– Keep particles small enough so they Keep particles small enough so they do not settle outdo not settle out
Wetting AgentsWetting Agents–– SurfactantsSurfactants–– Penetrate existing depositsPenetrate existing deposits–– Wash away from metal surfacesWash away from metal surfaces
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MICROBIOLOGICALMICROBIOLOGICALGROWTHGROWTH
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Microbiological GrowthMicrobiological Growth
Water treatment is Water treatment is about managing about managing three fouling three fouling processes...processes...CorrosionCorrosionScaleScaleMicrobioMicrobio
The microbial fouling The microbial fouling process is...process is...
The most complexThe most complexThe least understoodThe least understoodThe hardest to The hardest to measure and monitormeasure and monitorControlled using the Controlled using the least desirable, most least desirable, most expensive, & expensive, & potentially hazardous potentially hazardous productsproducts
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Microbiological GrowthMicrobiological Growth
Three Kinds Of Troublesome Three Kinds Of Troublesome Microorganisms In Cooling Water...Microorganisms In Cooling Water...
1. Bacteria1. Bacteria2. Algae2. Algae3. Fungi/Mold/Yeast3. Fungi/Mold/Yeast
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BacteriaBacteria
Sears Tower
Bacteria extremely Bacteria extremely smallsmallCompared to a Compared to a human, a bacteria is human, a bacteria is like a grain of sand to like a grain of sand to the Sears Towerthe Sears TowerSize allows many Size allows many (millions) to fit into a (millions) to fit into a small volume of small volume of water...water...
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BacteriaBacteria
There are as many There are as many bacteria in 12 oz. of bacteria in 12 oz. of cooling water as cooling water as there are people there are people living in the United living in the United StatesStatesThere are 40,000 There are 40,000 times as many times as many bacteria in a 50,000 bacteria in a 50,000 gallon cooling gallon cooling system as there are system as there are people in the world!people in the world!
12oz.Cooling Water
40,000 X50MGAL
Cooling System
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BacteriaBacteria
Types of BacteriaTypes of Bacteria1. Slime Forming1. Slime Forming2. Anaerobic Corrosive2. Anaerobic Corrosive3. Iron Depositing3. Iron Depositing4. Nitrifying4. Nitrifying5. Denitrifying5. Denitrifying
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BacteriaBacteria
Slime Formers
Iron DepositingAnaerobic
Typical Rods
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BacteriaBacteria
Produce acidic waste that lowers pH andProduce acidic waste that lowers pH andcauses corrosioncauses corrosionProduce large volumes of iron deposits Produce large volumes of iron deposits that foulthat foulProduce acids from ammonia that Produce acids from ammonia that increase corrosion & lower pHincrease corrosion & lower pHForm sticky slime masses that foul & Form sticky slime masses that foul & cause reduced heat transfercause reduced heat transfer
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Two Classifications of BacteriaTwo Classifications of Bacteria
PlanktonicPlanktonic::FreeFree--floating bacteria in bulk waterfloating bacteria in bulk water
SessileSessile::Bacteria attached to surfacesBacteria attached to surfacesOver 95% of bacteria in a cooling system Over 95% of bacteria in a cooling system are sessile and live in BIOFILMSare sessile and live in BIOFILMS
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BiofilmsBiofilms
Contribute to all Contribute to all cooling water cooling water problemsproblemsUnderdeposit Underdeposit corrosioncorrosionTrap silt & debris Trap silt & debris which foul heat which foul heat exchangers and exchangers and tower filltower fillProvide nucleation Provide nucleation sites for scale sites for scale formationformation Biofilm Formation
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FLOW
ThermalFoulant Conductivity
CaCO3 1.3-1.7CaSO4 1.3CaPO4 1.5MgPO4 1.3Fe Oxide 1.7Biofilm 0.4
P P
Common biofilms are 4 times more insulating than CaCO3 scale!
BiofilmsBiofilms
More insulating More insulating than most than most common scales common scales Reduce heat Reduce heat transfer efficiencytransfer efficiencyIncrease dP across Increase dP across heat exchangers & heat exchangers & reduce flowreduce flowHealth risks Health risks (legionella)(legionella)
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AlgaeAlgae
Require sunlight to growRequire sunlight to growFound on tower decks & exposed areasFound on tower decks & exposed areasForm Form ““algae matsalgae mats””Plug distribution holes on tower decksPlug distribution holes on tower decksPlug screens/foul equipmentPlug screens/foul equipmentConsume oxidantsConsume oxidantsProvide food for other organismsProvide food for other organisms
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FungiFungi
Use carbon in Use carbon in wood fibers for wood fibers for foodfoodDestroy tower Destroy tower lumber by either lumber by either surface or internal surface or internal rotting (deep rot) rotting (deep rot) Loss of structural Loss of structural integrity of towerintegrity of tower
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Factors Affecting Growth of Factors Affecting Growth of MicroorganismsMicroorganisms
Microorganism Sources: Air or Makeup Microorganism Sources: Air or Makeup waterwater
Cooling systems provide the ideal Cooling systems provide the ideal environment for microbiological growth environment for microbiological growth –– Nutrients: Ammonia, oil, organic Nutrients: Ammonia, oil, organic
contaminantscontaminants–– Temperature: 70Temperature: 70--140140°°F acceptableF acceptable–– pH: 6.0 pH: 6.0 -- 9.0 ideal9.0 ideal–– Location: Light/No LightLocation: Light/No Light–– Atmosphere: Aerobic/AnaerobicAtmosphere: Aerobic/Anaerobic
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Controlling Microbiological Controlling Microbiological GrowthGrowth
Water QualityWater Quality–– Eliminate organic contaminants (food)Eliminate organic contaminants (food)–– No food = No bugsNo food = No bugs
»» Bugs are Bugs are carniverous carniverous –– A forest feeds A forest feeds itselfitself
System Design ConsiderationsSystem Design Considerations–– Clean tower and sumps, cover decksClean tower and sumps, cover decks
Chemical Treatment with BiocidesChemical Treatment with Biocides
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Microbiological GrowthMicrobiological Growth
Chemical Treatment With BiocidesChemical Treatment With Biocides
Oxidizing BiocidesOxidizing BiocidesNonNon--oxidizing Biocidesoxidizing BiocidesBiodispersantsBiodispersants
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What About Dipslides?What About Dipslides?
Simple, quick, and inexpensive.
However, only gives bacteria levels from the bulk water.
There is more to this picture!
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Monitoring Tools for Monitoring Tools for Planktonic Microorganisms Planktonic Microorganisms
-- DipslidesDipslidesDipslides only measure selected Dipslides only measure selected aerobic planktonic microorganismsaerobic planktonic microorganisms
Total aerobic bacterial counts Total aerobic bacterial counts determined from dipslides are useful determined from dipslides are useful for tracking for tracking trendstrends
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Aerobic Plate CountsAerobic Plate Counts
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Microbiological MonitoringMicrobiological Monitoring
Sessile Monitoring
Tracide, ATP
Bio Box
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DIVERSITYDIVERSITYof different kinds….
the state of being unlike or different
refers to the KINDS of microorganisms present
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Differential Microbiological Differential Microbiological Analysis (DMA)Analysis (DMA)
Testing designed to differentiate the microbiological content within a system.
From: Analysis No. MB 207310 ABC Plant Date Sampled 9/ 9/97 Date Received 9/10/97 Date Completed 9/15/97 Sample Marked: Date Printed 9/15/97 Cooler Outlet
>>> Microbiological Evaluation <<<
PHYSICAL APPEARANCE Liquid with Floc
TOTAL AEROBIC BACTERIA 4,000 Enterobacter <100 Pigmented <100 Mucoids <100 Pseudomonas <100
Spores <10
TOTAL ANAEROBIC BACTERIA Sulfate Reducers 2
Clostridia <10
TOTAL FUNGI Yeasts <10 Molds 20
IRON-DEPOSITING Gallionella None Sphaerotilus None
ALGAE Filamentous None Nonfilamentous None
OTHER ORGANISMS None
Lab Comments: All counts express colony forming units per ml.
Microscopic examination: few crystals and very few diatoms.
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The goal in microbial fouling control ...
is almost never to “sterilize” the system, but rather,
...it is to MANAGE the fouling control process to a level that causes no operational problems
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How do I measure How do I measure biofilms?biofilms?
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Sessile monitoring is an Sessile monitoring is an integral part of the microbial integral part of the microbial
monitoring programmonitoring program
Planktonic results have a weak Planktonic results have a weak correlation to the sessile populationcorrelation to the sessile population
The sessile population, or biofilms, are The sessile population, or biofilms, are the true microbial control targetthe true microbial control target
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Surface Microbial Surface Microbial Monitoring Test Kit Monitoring Test Kit
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Surface Microbial Monitoring Test KitSurface Microbial Monitoring Test Kit–– Applied Services C0243Applied Services C0243–– SBIO is test codeSBIO is test codeKit contains supplies necessary to Kit contains supplies necessary to sample a surfacesample a surfaceMeasures microorganisms on surfaces, Measures microorganisms on surfaces, i.e., sessile populationi.e., sessile population
Monitoring Tools for Monitoring Tools for Sessile MicroorganismsSessile Microorganisms
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Sessile MonitoringSessile MonitoringSwab
Coupon
SterileBuffer
BioBox Surface MicrobialTest Kit
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Bio BoxBio Box
Visual indicatorVisual indicator
Removable Slides Removable Slides for Microscopic for Microscopic AnalysisAnalysis
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• Planktonic counts don’t often correlate with sessile counts.
• Use microbial types, numbers, and locations as clues to current conditions, trends, and improvements.
• Be creative with sample point locations, timing with cleanup events, etc.. to provide powerful diagnostic information.
• Establish criteria for success
BioManageBioManageTMTM Best PracticesBest PracticesRecognizing The ProblemRecognizing The Problem
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THANK YOU THANK YOU --
Any questions on Any questions on any topics we any topics we covered?covered?
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Every system Every system …… under under stressstress
High Stress Causes:High Stress Causes:–– ScaleScale–– CorrosionCorrosion–– FoulingFouling
Low Stress CausesLow Stress Causes–– High water costsHigh water costs–– High energy costsHigh energy costs–– High chemical costsHigh chemical costs
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Stress: varies by system Stress: varies by system operationoperation
High temperaturesHigh temperaturesLong holding time indices (Long holding time indices (HTIHTI’’ss))Biological/Organic contaminationBiological/Organic contamination–– Size, type and diversity of bioSize, type and diversity of bio--
populationspopulations
Low flow ratesLow flow ratesHigh oxidant concentrationsHigh oxidant concentrationsWater chemistryWater chemistry
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Stress: varies by system Stress: varies by system designdesign
Erratic feed systemsErratic feed systemsProblematic equipmentProblematic equipment–– Blowdown valves, makeBlowdown valves, make--up up
systems, etc.systems, etc.
Monitoring problemsMonitoring problems–– How does the rest of your facility How does the rest of your facility
work?work?
System design limitationsSystem design limitationsSystem locationSystem location
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Stress: varies by industryStress: varies by industry
Capacity limitationsCapacity limitationsAggressive water Aggressive water chemistrychemistry
Variable water Variable water chemistrychemistry
NutrientNutrient--rich rich environmentsenvironments
Regulatory NeedsRegulatory NeedsRegulatory NeedsRegulatory Needs
System System ContaminationContamination
Long Long HTIHTI’’ssEquipment often idle Equipment often idle for long periodsfor long periods
Food & BeverageFood & BeverageInstitutionalInstitutionalSemiconductorSemiconductor
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Stress: varies by locationStress: varies by location
Texas City, TX
Morris, IL
San Diego, CA
El Segundo, CA
Houston, TX
Westchester, IL
Sandy, UT
Beaumont, TX
Phoenix, AZ
Rahway, NJ
Naperville, IL
Tiger Bay, FL
Sioux City, IAMartinez, CA
Variab
le Wate
r
Chemist
ry
Low Hardness
Low Alkalinity
High HardnessHigh Alkalinity
High TemperaturesVariable Water Chemistry
Critical SystemsVariable Water Chemistry
High water costGray water use
Environmental ConcernsHigh Bio-Activity
Minneapolis, MN
Texas City, TX
Morris, IL
San Diego, CA
El Segundo, CA
Houston, TX
Westchester, IL
Sandy, UT
Beaumont, TX
Phoenix, AZ
Rahway, NJ
Naperville, IL
Tiger Bay, FL
Sioux City, IAMartinez, CA
Variab
le Wate
r
Chemist
ry
Low Hardness
Low Alkalinity
High HardnessHigh Alkalinity
High TemperaturesVariable Water Chemistry
Critical SystemsVariable Water Chemistry
High water costGray water use
Environmental ConcernsHigh Bio-Activity
Minneapolis, MN
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Stress: constantly varyingStress: constantly varying……
Control Based on System Stress
-
10
20
30
40
50
60
70
80
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89
Time (each interval = 4 hours)
Con
cent
ratio
n (p
pm)
Active Concentration (ppm)Treatment Concentration (ppm)
As system stress varies, 3D TRASAR adjusts dosage to compensate. At times of high stress, more inhibitor is fed. When stress decreases, less inhibitor is fed.
High Stress!Low Stress!
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Stress: unpredictableStress: unpredictable
3D TRASAR Optimizes System Stress
-
200
400
600
800
1,000
1,200
1,400
1,600
1,800
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61
Time (Each Division = 4 hours)
Con
duct
ivity
3D TRASAR detects low stress and increases conductivity to minimize operating cost.
3D TRASAR detects high stress and decreases conductivity to prevent operational problems.
3D TRASAR detects low stress and increases the conductivity to minimize operating cost.
In this case, a bleach feed system failed. When the system was repaired at 10:50 PM, high concentrations of bleach were fed into the system, increasing system stress. 3D TRASAR detected the stress and decreased the conductivity to prevent an operational problem.
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Stress: undiscoveredStress: undiscovered
-
100
200
300
400
500
600
700
800
900
1,000
Time (each division = 1 day)
OR
P (m
V)
-
0.5
1.0
1.5
2.0
2.5
3.0
Cop
per C
orro
sion
Rat
e (m
py)
ORP Copper
Before 3D Bio-Control, ORP-based control was erratic and copper corrosion rates were high.
After 3D Bio-Control was implemented, ORP levels were reduced, variability was reduced and copper corrosion rates improved.
3D Bio-Control Started
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Stress: many sourcesStress: many sources
Average Daily Nalco Bio-Index
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
1-Ju
n
2-Ju
n
3-Ju
n
4-Ju
n
5-Ju
n
6-Ju
n
7-Ju
n
8-Ju
n
9-Ju
n
10-J
un
11-J
un
12-J
un
13-J
un
14-J
un
15-J
un
16-J
un
17-J
un
18-J
un
19-J
un
20-J
un
21-J
un
22-J
un
23-J
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24-J
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25-J
un
26-J
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27-J
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28-J
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29-J
un
30-J
un
Date
Nal
co B
io-In
dex
Monday
Monday
Monday
Monday
Monday
Bio-activity stresses cooling systems.
Bringing idle equipment online increases system
stress.
![Page 109: Nalco Cooling Tower Presentation](https://reader034.vdocuments.us/reader034/viewer/2022052118/55cf9a08550346d033a02def/html5/thumbnails/109.jpg)
Stress: requires dynamic Stress: requires dynamic responseresponse
June 16Nalco Bio-Index and Pump On Time
(5)
-
5
10
15
20
25
30
35
0:00 3:00 5:40 8:40 11:40 15:00 18:20 21:28
Time (Hours:Minutes)
Nal
co B
io-In
dex
-
1
2
3
4
5
Pum
p O
n (m
inut
es)
Pump On (minutes) Nalco Bio-Index
Nalco Bio-Index Set-Point
3D TRASAR detects a change in the bio-population and starts applying more oxidizing biocide to compensate.
When 3D TRASAR detects a change in the rate of bio-population increase, it responds by feeding less biocide, controlling the bio-population, but preventing a biocide overdose.
![Page 110: Nalco Cooling Tower Presentation](https://reader034.vdocuments.us/reader034/viewer/2022052118/55cf9a08550346d033a02def/html5/thumbnails/110.jpg)
Stress: intermittentStress: intermittent
3.0
4.0
5.0
6.0
7.0
8.0
9.0
12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PMDate/Time
pH
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
Mild
Ste
el C
orro
sion
Rat
e (m
py)
pH MS Corrosion Rate
7:17 PM: acid upset causes pH to drop.
11:24 PM, pH returns to normal
In spite of extremely low pH, corrosion rate is unaffected.
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Stress: interrelated causesStress: interrelated causes
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
2.25
2.30
Date (Each Division = 10 days)
Exch
ange
r Effi
cien
cy
Average Silica = 8 ppm
Average Silica = 7 ppm
Prior to 3D TRASAR control, phosphate upsets put stress on the system which caused significant fouling. In this case, the overfeed caused a 14% efficiency loss.
Average Silica = 26 ppm
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Stress: interrelated causesStress: interrelated causes
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
2.25
2.30
Date (Each Division = 10 days)
Effic
ienc
y Fa
ctor
Average Silica = 8 ppm
4
Average Silica = 26 ppm
4
4Average Silica = 7 ppm
Even with a significant phosphate overfeed, efficiency loss due to fouling was only 3%.
![Page 113: Nalco Cooling Tower Presentation](https://reader034.vdocuments.us/reader034/viewer/2022052118/55cf9a08550346d033a02def/html5/thumbnails/113.jpg)
Stress: unique to every Stress: unique to every systemsystem
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Stress: highly visibleStress: highly visible
![Page 115: Nalco Cooling Tower Presentation](https://reader034.vdocuments.us/reader034/viewer/2022052118/55cf9a08550346d033a02def/html5/thumbnails/115.jpg)
Manage
Stress
Grow Revenue
Control Costs
Reduce Cost of Capital
Manage Risks
Improve Cash Flow
improve product quality
extend time between turnarounds
reduce maintenance
decrease chemical usageavoid
equipment purchase
reduce legal exposure
reduce operating liability
minimize onsite inventory
fixed contract pricing
increase throughput
decrease energy usage
decrease water usage
extend equipment life
avoid EH&S fines
avoid unplanned expenses
improve operator efficiency
Stress: highly visibleStress: highly visible