operation and maint for energy efficiency

Cooling Tower Operation and Maintenance is the Key for Improved Energy Efficiency

Cooling Tower Operation and Maintenance is the Key for Improved Energy Efficiency

Principle of Operation and Layout Principle of Operation and Layout –– Kavita AnujeKavita AnujeMaintenanceMaintenance Regimens Regimens –– Trevor Trevor HeggHeggOperating Strategies & Water Treatment Operating Strategies & Water Treatment -- Paul LindahlPaul Lindahl

Cooling Tower Operation and Maintenance for Improved Energy Efficiency

Terminology

Forced Draft CounterflowForced Draft Counterflow

Induced Draft CounterflowInduced Draft Counterflow

Forced Draft CrossflowForced Draft Crossflow

Induced Draft Crossflow

Open Cooling TowersOpen Cooling Towers

Closed Circuit Closed Circuit Cooling TowersCooling Towers

Induced Draft Crossflow


Open Cooling TowerOpen Cooling TowerAn evaporative piece of equipment that exposes An evaporative piece of equipment that exposes water directly to the cooling atmosphere, thereby water directly to the cooling atmosphere, thereby

transferring the source heat load directly to the air.transferring the source heat load directly to the air.


Closed Circuit Cooling TowerClosed Circuit Cooling TowerAn evaporative piece of equipment that contains twoAn evaporative piece of equipment that contains twoseparate fluid circuits. The first is an external circuitseparate fluid circuits. The first is an external circuit

where water is exposed to the atmosphere as itwhere water is exposed to the atmosphere as itcascades over the tubes of a coil bundle. The secondcascades over the tubes of a coil bundle. The secondis an internal circuit in which the fluid to be cooledis an internal circuit in which the fluid to be cooled

circulates inside the tubes of the coil bundle.circulates inside the tubes of the coil bundle.


Forced DraftForced DraftType of mechanical draft tower in which one orType of mechanical draft tower in which one or

more fans are located at the air inlet to force air into more fans are located at the air inlet to force air into the cooling tower.the cooling tower.


Induced DraftInduced DraftType of mechanical draft tower in which one orType of mechanical draft tower in which one or

more fans are located in the air outlet to induce air more fans are located in the air outlet to induce air through the air inlets.through the air inlets.


CounterflowCounterflowIn a counterflow cooling tower, the air enters at theIn a counterflow cooling tower, the air enters at the

base of the tower, flows upward and interfacesbase of the tower, flows upward and interfacescounter currently with the falling hot water.counter currently with the falling hot water.


CrossflowCrossflowIn a crossflow cooling tower, the air flowsIn a crossflow cooling tower, the air flows

horizontally through the cooling tower and interfaceshorizontally through the cooling tower and interfacesperpendicularly with the falling hot water.perpendicularly with the falling hot water.


Air Flow Direction

Water Flow Direction


Air Flow Direction


Fluid Inlet

Fluid Outlet


Air Flow Direction



Air Flow Direction


Fluid Inlet

Fluid Outlet


Air Flow Direction



Water Distribution SystemsWater Distribution Systems–– Gravity distribution systemGravity distribution system–– Spray distribution systemSpray distribution system


Gravity Distribution SystemGravity Distribution System–– Open basinsOpen basins–– Large orifice, 360° nozzlesLarge orifice, 360° nozzles–– Easily accessed for maintenance Easily accessed for maintenance –– Basin water level used to balance flowBasin water level used to balance flow


Spray Distribution SystemSpray Distribution System–– Pressurized systemPressurized system–– Large orifice, 180° directional nozzlesLarge orifice, 180° directional nozzles–– Spray header and branchesSpray header and branches–– 2 PSI spray pressure at the header inlet2 PSI spray pressure at the header inlet


Heat Transfer Surface (Fill or Wet Deck)Heat Transfer Surface (Fill or Wet Deck)–– PVC wet deck surfacePVC wet deck surface–– Specialty wet deck materialsSpecialty wet deck materials


PVC Wet Deck SurfacePVC Wet Deck Surface–– Impervious to rot, decay, fungus and biological Impervious to rot, decay, fungus and biological

attackattack–– 130°F limitation for counterflow cooling towers130°F limitation for counterflow cooling towers–– 120°F limitation for crossflow cooling towers 120°F limitation for crossflow cooling towers


High Temperature PVC Wet Deck SurfaceHigh Temperature PVC Wet Deck Surface–– Impervious to rot, decay, fungus and biological Impervious to rot, decay, fungus and biological

attackattack–– 150°F limitation for counterflow cooling towers150°F limitation for counterflow cooling towers–– 135°F limitation for crossflow cooling towers 135°F limitation for crossflow cooling towers


Specialty Wet Deck SurfacesSpecialty Wet Deck Surfaces–– Available for process type applicationsAvailable for process type applications

–– Galvanized or stainless steel wet deck Galvanized or stainless steel wet deck surfacesurface

–– Dirty water fillDirty water fill–– Splash fillSplash fill

–– Contact equipment manufacturer for Contact equipment manufacturer for performance information performance information


Air Moving SystemsAir Moving Systems–– Axial fansAxial fans–– Centrifugal fansCentrifugal fans


Axial FansAxial Fans–– Over 80% of cooling towers on HVAC Over 80% of cooling towers on HVAC

applications use axial fansapplications use axial fans–– High volume/ Low static pressureHigh volume/ Low static pressure–– High efficiencyHigh efficiency–– Low energy consumptionLow energy consumption–– Improved sound ratingsImproved sound ratings


Centrifugal FansCentrifugal Fans–– High volume/Static pressuresHigh volume/Static pressures

–– Indoor installationsIndoor installations–– Inlet or discharge ductworkInlet or discharge ductwork

–– High energy consumptionHigh energy consumption–– Quiet operationQuiet operation–– Tight layout requirementsTight layout requirements


1,500 GPM of Water1,500 GPM of Water95°F EWT95°F EWT85°F LWT85°F LWT78°F EWB

Counterflow, centrifugal Counterflow, centrifugal fan unit requires 60 HPfan unit requires 60 HPCrossflow, axial fan unit Crossflow, axial fan unit requires 30 HPrequires 30 HPAxial fan units require less Axial fan units require less HP than centrifugal fan HP than centrifugal fan units

78°F EWB

units


Drive SystemsDrive Systems–– Belt driveBelt drive–– Gear driveGear drive


Proven performance on cooling Proven performance on cooling tower applicationtower applicationEfficient and designed for moist Efficient and designed for moist air applicationsair applications


Cooling Tower Equipment LayoutCooling Tower Equipment Layout


Prevent warm air or drift from being introduced into fresh Prevent warm air or drift from being introduced into fresh air intakes or from being carried over populated areasair intakes or from being carried over populated areasConsider the potential for plumeConsider the potential for plumeNote the direction of the prevailing windsNote the direction of the prevailing windsEnsure adequate supply of fresh air to the air intakeEnsure adequate supply of fresh air to the air intakeProvide adequate space for piping and proper servicing and Provide adequate space for piping and proper servicing and maintenancemaintenanceTop of the unit discharge must be at least level with the Top of the unit discharge must be at least level with the adjacent wall adjacent wall


Layout ExamplesLayout Examples–– Adjacent to a wall or buildingAdjacent to a wall or building–– In an enclosureIn an enclosure–– Adjacent to a louvered or slotted wallAdjacent to a louvered or slotted wall


NominalNominal–– 1,500 GPM 95/85/781,500 GPM 95/85/78

1°F Recirculation1°F Recirculation–– 1,384 GPM 95/85/791,384 GPM 95/85/79–– 8% 8% DerateDerate

2°F Recirculation2°F Recirculation–– 1,258 GPM 95/85/801,258 GPM 95/85/80–– 19% 19% DerateDerate

Prevailing Wind

Induced DraftCooling Tower


NominalNominal–– 1,500 GPM 95/85/781,500 GPM 95/85/78

1°F Recirculation1°F Recirculation–– 1,500 GPM 1,500 GPM

95.77/85.77/7995.77/85.77/792°F Recirculation2°F Recirculation

–– 1,500 GPM 1,500 GPM 96.56/886.56/8096.56/886.56/80

Prevailing Wind



Every 1°F Increase in CWT Corresponds to aEvery 1°F Increase in CWT Corresponds to a2% Decrease in Chiller Efficiency2% Decrease in Chiller Efficiency


Correct cooling tower Correct cooling tower installation when installation when located adjacent to a located adjacent to a building or wallbuilding or wall



What is the distance What is the distance between the wall and between the wall and the air inlet to the the air inlet to the cooling tower?cooling tower?

–– Maximum air velocity Maximum air velocity should not exceed 300 should not exceed 300 FPMFPM

–– Air entry envelope Air entry envelope consists of top and two consists of top and two sidessides

–– Based on 125,900 Based on 125,900 CFM, an inlet height of CFM, an inlet height of 10 feet and an air inlet 10 feet and an air inlet length of 12 feet, the length of 12 feet, the distance to the wall is distance to the wall is 6.5 feet6.5 feet


D


When cooling towers When cooling towers are positioned with air are positioned with air inlets facing each inlets facing each other, the distance other, the distance between cooling between cooling towers is 2 x Dtowers is 2 x D


What is the distance between What is the distance between the wall and the air inlet to the the wall and the air inlet to the cooling tower for a well cooling tower for a well enclosure?enclosure?

–– Maximum air velocity should not Maximum air velocity should not exceed 400 FPMexceed 400 FPM

–– Center the cooling tower within Center the cooling tower within the enclosure for uniform air flow the enclosure for uniform air flow to the air inletsto the air inlets

–– Air entry is from the top onlyAir entry is from the top only–– Based on 125,900 CFM, an air Based on 125,900 CFM, an air

entry area as indicated by the entry area as indicated by the shaded area, the distance to the shaded area, the distance to the wall is 8 feetwall is 8 feet

D D

Well Installation with anInduced Draft Cooling Tower


What is the distance between What is the distance between the louvered wall and the air the louvered wall and the air inlet to the cooling tower for a inlet to the cooling tower for a well enclosure?well enclosure?

–– Center the cooling tower within Center the cooling tower within the enclosure for uniform air flow the enclosure for uniform air flow to the air inletsto the air inlets

–– Louver must provide at least 50% Louver must provide at least 50% net free areanet free area

–– Louver air velocity should not Louver air velocity should not exceed 600 FPMexceed 600 FPM

–– Maintain at least 3 feet between Maintain at least 3 feet between the tower air inlets and the the tower air inlets and the louvered walllouvered wall

D D

Louvered Well Installation with anInduced Draft Cooling Tower


Maintenance Regimens – Trevor Hegg

Maintenance Guidelines forOpen Cooling Towers & Closed Circuit Cooling Towers

MAINTENANCE

Maintenance and water treatment are Maintenance and water treatment are the most important factors affecting the most important factors affecting the life and energy efficient operation the life and energy efficient operation of evaporative cooling equipment!of evaporative cooling equipment!

MAINTENANCE? Who needs it?

MAINTENANCE

Maintenance and water treatment are the Maintenance and water treatment are the most neglected regimens of cooling most neglected regimens of cooling tower operation, and cooling towers are tower operation, and cooling towers are generally the most neglected generally the most neglected components in the mechanical system.components in the mechanical system.

Why?Why?•• Remotely located & difficult to accessRemotely located & difficult to access•• Limited maintenance resourcesLimited maintenance resources

PeoplePeopleTrainingTrainingBudgetsBudgets

MAINTENANCE

Objectives:Objectives:

•• Review basic elements of a good Review basic elements of a good maintenance regimen.maintenance regimen.

•• Develop an understanding of the Develop an understanding of the costs of poor maintenance on the costs of poor maintenance on the life & energy efficiency of cooling life & energy efficiency of cooling towers.towers.

MAINTENANCE REGIMENSReview major cooling tower systems and Review major cooling tower systems and their appropriate maintenance regimens:their appropriate maintenance regimens:

•• Circulating WaterCirculating Water•• Fan and DriveFan and Drive•• Heat Transfer Surface (Fill or Coil)Heat Transfer Surface (Fill or Coil)•• Air Entry LouversAir Entry Louvers•• Drift EliminatorsDrift Eliminators

MAINTENANCE REGIMENS

•• Reputable manufacturers provide maintenance Reputable manufacturers provide maintenance instructions and check sheets. It is best to follow instructions and check sheets. It is best to follow the manufacturer’s recommendations!the manufacturer’s recommendations!

•• ASHRAE Handbook also provides a good general ASHRAE Handbook also provides a good general guide.guide.

MAINTENANCE REGIMENS

•• Manufacturer and ASHRAE Manufacturer and ASHRAE guidelines are for normal cooling guidelines are for normal cooling season regimens.season regimens.

•• Unusual operating conditions will Unusual operating conditions will require additional operator require additional operator attention.attention.

•• Winter operation and longWinter operation and long--term term shutshut--down requires additional down requires additional servicing. Consult the servicing. Consult the manufacturer.manufacturer.

MAINTENANCE REGIMEN –Circulating Water System Types

CrossCross--flow Tower Operation View of Water Distribution Boxflow Tower Operation View of Water Distribution Box

Gravity Flow Water Distribution SystemGravity Flow Water Distribution SystemCommon to crossCommon to cross--flow cooling towers and coolers.flow cooling towers and coolers.

MAINTENANCE REGIMEN –Circulating Water System Types

Closed Circuit Tower View of Pressurized DistributionClosed Circuit Tower View of Pressurized DistributionOperation System and NozzlesOperation System and Nozzles

Pressurized Flow Water Distribution SystemPressurized Flow Water Distribution System

MAINTENANCE REGIMEN –Circulating Water System

Spray Nozzles & Water Distribution Spray Nozzles & Water Distribution Boxes need to be inspected & Boxes need to be inspected & cleanedcleaned••After startAfter start--up and up and ••Monthly thereafter.Monthly thereafter.

Regular inspection allows quick Regular inspection allows quick treatment and control of corrosion treatment and control of corrosion and mechanical failures. and mechanical failures.


Clogged distribution nozzles cause:Clogged distribution nozzles cause:•• Reduced or malReduced or mal--distributed water flow = distributed water flow =

capacity reductioncapacity reduction•• Heat Exchanger surface scaling/fouling = Heat Exchanger surface scaling/fouling =

capacity reductioncapacity reduction•• Overflowing distribution boxes = water & Overflowing distribution boxes = water &

chemical losschemical loss•• Excessive drift = water & chemical lossExcessive drift = water & chemical loss•• Fan motor overFan motor over--ampingamping (forced draft) = (forced draft) =

reduced motor lifereduced motor life


Suction Strainers:Suction Strainers:•• Designed to protect pump Designed to protect pump

and nozzles.and nozzles.•• Inspect & clean weekly.Inspect & clean weekly.•• Operating environments Operating environments

laden with airborne fibrous laden with airborne fibrous materials (agricultural, materials (agricultural, paper, textile processing) paper, textile processing) demand more frequent demand more frequent strainer cleaning.strainer cleaning.


Poor Strainer maintenance leads to:Poor Strainer maintenance leads to:•• Reduced flow = reduced capacityReduced flow = reduced capacity•• Pump Pump cavitationcavitation = pump repair costs = pump repair costs and objectionable plant noiseand objectionable plant noise

•• Collapsed strainers = tower repair Collapsed strainers = tower repair costscosts


Basin Maintenance:Basin Maintenance:••Clean and flush monthly.Clean and flush monthly.••Inspect and repair corrosion.Inspect and repair corrosion.

Accumulated solids:Accumulated solids:••Clog equalizer & bypass linesClog equalizer & bypass lines••Hide corrosion cellsHide corrosion cells••Give breeding environment for bioGive breeding environment for bio--growthgrowth


Closed Circuit Tower Water Pumps:Closed Circuit Tower Water Pumps:•• Inspect seals & free rotation of shaft monthly.Inspect seals & free rotation of shaft monthly.•• Lubricate bearings per motor manufacturer Lubricate bearings per motor manufacturer instructions.instructions.

Leaking seals are costly Leaking seals are costly with lost water and with lost water and treatment chemicals.treatment chemicals.


MakeMake--up water and operating level controlsup water and operating level controls

Mechanical Float Valve Electric Valve & SensorMechanical Float Valve Electric Valve & Sensor


Set operating level and water supply pressure to Set operating level and water supply pressure to manufacturer’s recommendations.manufacturer’s recommendations.

••Inspect water level and adjust float monthly.Inspect water level and adjust float monthly.

••Inspect valve seals and full shutInspect valve seals and full shut--off monthly.off monthly.

Clean electronic sensing elements as required! Clean electronic sensing elements as required!


Malfunctioning level Malfunctioning level control can be costly with control can be costly with water and chemical loss water and chemical loss and even equipment and even equipment damage.damage.

Proper water level control is required for pump Proper water level control is required for pump priming and prevention of air entrainment in priming and prevention of air entrainment in suction lines.suction lines.

MAINTENANCE REGIMEN –Fan & Drive System

The fan system moves the air which cools The fan system moves the air which cools the water. the water. It is critical to keep the fan It is critical to keep the fan system in top operating condition!system in top operating condition!

•• Daily walk around the tower and listen for unusual Daily walk around the tower and listen for unusual noises or vibration.noises or vibration.

•• If reasons for vibration are easily detected, (loose If reasons for vibration are easily detected, (loose belts, loose motor base, loose bearing locking belts, loose motor base, loose bearing locking collars, loose fan or sheave bushings) correct as collars, loose fan or sheave bushings) correct as required.required.

•• If causes of vibration are not easily detected, If causes of vibration are not easily detected, consult a specialty vibration analysis contractor.consult a specialty vibration analysis contractor.


•• Quarterly clean fan of heavy debris (trash, Quarterly clean fan of heavy debris (trash, bird droppings, scale) and inspect the fan bird droppings, scale) and inspect the fan and drive components for tight fasteners, and drive components for tight fasteners, missing balance washers & structural missing balance washers & structural integrity. integrity.

•• Repair or replace corroded hardware, Repair or replace corroded hardware, even the fan if necessary. even the fan if necessary.

•• Check the mechanical equipment support Check the mechanical equipment support for cracks and tight hardware.for cracks and tight hardware.

•• Check security of fan guards.Check security of fan guards.


Belt Drive Systems:Belt Drive Systems:Belt Tensioning:Belt Tensioning:Check 24 hrs after startCheck 24 hrs after start--up.up.

Check monthly thereafter.Check monthly thereafter.

1/2” 1/2” -- 3/4” deflection with 3/4” deflection with moderate finger pressure at moderate finger pressure at center span of belt. Check center span of belt. Check manufacturer’s O&M guide.manufacturer’s O&M guide.


Gear Drive Systems:Gear Drive Systems:Lubrication:Lubrication:Check oil level weekly.Check oil level weekly.Change oil 500 hours or Change oil 500 hours or 4 weeks after start4 weeks after start--up.up.Follow gear box O&M Follow gear box O&M guide for oil type and guide for oil type and change frequency. change frequency. Recommend synthetic, Recommend synthetic, oxidation inhibited oil.oxidation inhibited oil.


Gear Drive Systems:Gear Drive Systems: Drive Shafts:Drive Shafts:•• Inspect drive shaft Inspect drive shaft and coupling and coupling hardware monthly.hardware monthly.

•• Inspect coupling flex Inspect coupling flex elements for elements for buckling and fatigue buckling and fatigue damage. Replace damage. Replace as required.as required.

Drive shaft CouplingDrive shaft Coupling


Fan Shaft Bearings:Fan Shaft Bearings:Bearing Lubrication:Bearing Lubrication:Lubrication ScheduleLubrication Schedule•• 1000 hours or 3 months 1000 hours or 3 months

-------- Induced DraftInduced Draft•• 2000 hours or 6 months 2000 hours or 6 months

-------- Forced DraftForced Draft•• Use water resistant Use water resistant

grease approved by grease approved by manufacturer.manufacturer.


Motors:Motors:Good maintenance starts with the installationGood maintenance starts with the installation1. Wire per nameplate and check rotation1. Wire per nameplate and check rotation•• MultiMulti--lead (9, 12 wire) motors may be confusinglead (9, 12 wire) motors may be confusing•• Check multiCheck multi--speed motor rotation at both speedsspeed motor rotation at both speeds•• Check current draw on startCheck current draw on start--upup2. 2. Check operational controlsCheck operational controls•• Set proper time delay between speed changesSet proper time delay between speed changes•• Set thermostat differentials to limit fan cycling Set thermostat differentials to limit fan cycling

(3(3--6 starts/hour)6 starts/hour)


Motors:Motors:Motor life and efficiency is enhanced byMotor life and efficiency is enhanced by1. Keeping motor body cool1. Keeping motor body cool•• Clean casing and cooling fins of scale buildClean casing and cooling fins of scale build--upup•• Do not obstruct cooling vents around motorDo not obstruct cooling vents around motor2. Properly lubricating motor bearings2. Properly lubricating motor bearings•• Follow motor O&M guide for lubrication intervals, Follow motor O&M guide for lubrication intervals,

typically 2typically 2--3 years, and compatible greases.3 years, and compatible greases.•• Some motors have sealed bearings and do not Some motors have sealed bearings and do not

require lubrication.require lubrication.


Motors:Motors:Motors driven by variable frequency drives (Motors driven by variable frequency drives (vfdvfd) ) 1.1. Offer fan energy saving at the cooling towerOffer fan energy saving at the cooling tower2.2. Reduce fan cycling and provide soft startingReduce fan cycling and provide soft starting3.3. Need to be specifically selected for Need to be specifically selected for vfdvfd dutyduty4.4. Need limits on length between motor & driveNeed limits on length between motor & drive

(Depending on drive, typically 50 to 200 feet.)(Depending on drive, typically 50 to 200 feet.)5.5. Run hotter and need good cooling airRun hotter and need good cooling air--flowflow

MAINTENANCE REGIMEN –Heat Transfer Surface

Open tower surface (fill)Open tower surface (fill) Closed circuit tower coilClosed circuit tower coil

Inspect heat transfer surfaces monthly.Inspect heat transfer surfaces monthly.Inspect both the top Inspect both the top andand bottom. Generally, bottom. Generally, scaling starts on the top and bioscaling starts on the top and bio--fouling builds fouling builds from the bottom. from the bottom.


Open Tower Packing (Fill):Open Tower Packing (Fill):••Scale, solids and bioScale, solids and bio--fouling fouling restrict air & water passages.restrict air & water passages.

••Capacity diminishes rapidly Capacity diminishes rapidly with increased fouling.with increased fouling.

••Extra weight can damage fill Extra weight can damage fill and structural supports.and structural supports.

Typical fill clogging from bioTypical fill clogging from bio--films and suspended solids.films and suspended solids.


Closed Circuit Tower Coil:Closed Circuit Tower Coil:••Scale on coil Scale on coil walls is a direct walls is a direct heat transfer heat transfer barrier. barrier.

••Capacity Capacity diminishes with diminishes with increased increased fouling.fouling.


Closed Circuit Cooling Tower Performance vs. Scale Accumulation on Heat Transfer Coil

40.0%50.0%60.0%70.0%80.0%90.0%

100.0%

0 0.002 0.004 0.006

Fouling Factor & Approximate Scale Thickness On Coil

Tow

er P

erfo

rman

ce

Cap

abili

ty

1/32" Scale 1/16" ScaleClean Tube 3/32" Scale

High Heat Flux Coil

Low Heat Flux Coil

( 0.8 mm ) ( 1.6 mm ) ( 2.4 mm )

Closed Circuit Tower CoilClosed Circuit Tower Coil


Cleaning heavy scale or bioCleaning heavy scale or bio--fouling is difficult.fouling is difficult.Often the fill or coil are damaged in the process.Often the fill or coil are damaged in the process.

Results of a scaled coilResults of a scaled coilcleaned with acid. cleaned with acid. This coil is ruined.This coil is ruined.

IT IS ESSENTIAL TO MAINTAIN A IT IS ESSENTIAL TO MAINTAIN A PREVENTATIVEPREVENTATIVE WATER TREATMENT WATER TREATMENT PROGRAM.PROGRAM.

MAINTENANCE REGIMEN –Drift Eliminators

Separate water droplets from leaving air streamSeparate water droplets from leaving air stream••Subject to damage from weather & vandalismSubject to damage from weather & vandalism••Subject to corrosionSubject to corrosion

Damaged eliminatorDamaged eliminatorsection, which shouldsection, which shouldbe replaced.be replaced.

MAINTENANCE REGIMEN –Drift Eliminators

Proper placement and good physical conditionProper placement and good physical condition•• Minimizes water and treatment chemical lossMinimizes water and treatment chemical loss•• Minimizes air restriction for maximum capacityMinimizes air restriction for maximum capacity•• Minimizes airborne bacterial transmission Minimizes airborne bacterial transmission

Inspect condition and placement monthly.Inspect condition and placement monthly.Remove bioRemove bio--growth and debris. Notify growth and debris. Notify treatment service of biotreatment service of bio--growth. growth. Replace damaged eliminators.Replace damaged eliminators.

MAINTENANCE REGIMEN –Air Inlet Louvers

Examples of scaled, bioExamples of scaled, bio--fouled and debris laden inlet louvers.fouled and debris laden inlet louvers.

MAINTENANCE REGIMEN –Air Inlet Louvers

Proper placement and good physical conditionProper placement and good physical condition•• Minimizes water and treatment chemical loss Minimizes water and treatment chemical loss

from basin splashfrom basin splash--out.out.•• Minimizes air restriction for maximum capacityMinimizes air restriction for maximum capacity•• Minimizes airborne bacterial transmission Minimizes airborne bacterial transmission

Inspect condition and placement monthly.Inspect condition and placement monthly.Remove bioRemove bio--growth and debris. Notify growth and debris. Notify treatment service of biotreatment service of bio--growth. growth. Repair damaged louvers.Repair damaged louvers.

Winter OperationMaintenance & Energy Saving Tips

Prevent freezing and expensive ice damage Prevent freezing and expensive ice damage before the winter season arrives:before the winter season arrives:

•• Check heat tracing and insulation on drains, Check heat tracing and insulation on drains, makemake--up and circulating water lines.up and circulating water lines.

•• Test basin heaters and controls.Test basin heaters and controls.•• Charge coils with glycol or drain completely.Charge coils with glycol or drain completely.•• Test operation of positive closure dampers Test operation of positive closure dampers --

open with fan on and closed with fan off. open with fan on and closed with fan off.


More tips:More tips:•• Do not run fans with pumps off unless basin is Do not run fans with pumps off unless basin is

drained.drained.•• Ensure that fan drives are selected for dry Ensure that fan drives are selected for dry

operation.operation.•• Interlock heater “off” when pump or fan Interlock heater “off” when pump or fan

operates.operates.•• Keep a heat load on the tower. Cold water Keep a heat load on the tower. Cold water

temperature should stay above 40°F (4.4C) temperature should stay above 40°F (4.4C)


Ice can cause expensive damage to the fill and Ice can cause expensive damage to the fill and tower structure.tower structure.

•• Schedule regular Schedule regular defrost cycles.defrost cycles.

•• Keep water flow in Keep water flow in safe range of the safe range of the distribution nozzle.distribution nozzle.

Maintenance & Energy Efficient OperationTowers lacking a good maintenance regimen, which Towers lacking a good maintenance regimen, which includes water treatment, routinely operate at well below includes water treatment, routinely operate at well below design capability.design capability.

A basic maintenance regimen is an investment to: A basic maintenance regimen is an investment to: maximize the energy efficiency of the tower and maximize the energy efficiency of the tower and the mechanical system,the mechanical system,minimize capital investment in equipment by minimize capital investment in equipment by extending its life and replacement intervals,extending its life and replacement intervals,minimize annual maintenance expenses through minimize annual maintenance expenses through preventative measures rather than costly repairs.preventative measures rather than costly repairs.


Operating Strategies and Water Treatment

Paul Lindahl

WHY WATER TREATMENT? Air

Water

AirDebrisGases

Air and water contents enter and build in the tower.

Biological Growth

Bacteria, AlgaeBacteria, AlgaeFouling exchangersFouling exchangersFouling Cooling TowerFouling Cooling TowerHealth Effects, such as Legionnaire’s DiseaseHealth Effects, such as Legionnaire’s Disease

Water TreatmentsWater TreatmentsOxidizing BiocidesOxidizing BiocidesNonNon--oxidizing Biocidesoxidizing Biocides

Deposits assist growth of Deposits assist growth of biofilms biofilms and and biofoulingbiofouling, , side stream filtration is recommendedside stream filtration is recommended

Corrosion

Consider metals in entire water systemConsider metals in entire water systemSteel and Iron vs. Stainless SteelSteel and Iron vs. Stainless SteelCopper and its AlloysCopper and its AlloysAluminumAluminum

Appropriate Water Treatments with Appropriate Water Treatments with qualified WT vendor/consultantqualified WT vendor/consultantControl deposition of solids, side stream Control deposition of solids, side stream filtration recommendedfiltration recommended

Deposits Impact Corrosion

Oxide Layer

CELL METABOLISM LOWERS pH UNDER BIOFILM WHICH CORRODES METAL

Deposits Impact Corrosion

Oxide Layer

PITTING FAILURE

Each Treatment Impacts the Others

MICROBES (MB)

CORROSION DEPOSITION

Control Methods

BiocideBiocide to reduce Microbe and to reduce Microbe and BiofilmBiofilmGrowth [corrosion and scaling effect]Growth [corrosion and scaling effect]InhibitorsInhibitors to protect Metals from Corrosionto protect Metals from CorrosionInhibitorsInhibitors to prevent Scale Precipitationto prevent Scale Precipitation

SurfactantSurfactant = Bio= Bio--penetrationpenetrationAntiAnti--foamfoam = Reduce visible effect of = Reduce visible effect of biocidebiocide

Water Quality

General GuidelinesGeneral Guidelines: : Note: for tower water, not makeNote: for tower water, not make--upup

High TemperatureHigh Temperature:: < 120 < 120 °°F F PH: 6.5 PH: 6.5 –– 9.09.0Chlorides: < 750 Chlorides: < 750 ppm ppm for Galvanized Steel, for Galvanized Steel, < 1500< 1500 ppmppm for 300 Series Stainless Steelfor 300 Series Stainless SteelCalcium: (as CaCO3) < 800Calcium: (as CaCO3) < 800 ppmppm should not should not result in calcium sulfate scaleresult in calcium sulfate scale

Water Quality

Sulfates: If calcium > 800Sulfates: If calcium > 800 ppmppm, sulfates < , sulfates < 800800 ppmppm (or less in arid climates) to limit (or less in arid climates) to limit scale. scale.

Otherwise, < 5000Otherwise, < 5000 ppmppm is acceptable. is acceptable. Silica: < 150Silica: < 150 ppmppm as SiO2 to prevent silica as SiO2 to prevent silica scalescaleIron: < 3 Iron: < 3 ppmppmManganese: < 0.1Manganese: < 0.1 ppmppm

Water Quality

Total Suspended Solids (TSS): Total Suspended Solids (TSS): < 25< 25 ppmppm for film fillfor film fill

Total Dissolved Solids (TDS): Total Dissolved Solids (TDS): < 5000< 5000 ppmppm for thermal performancefor thermal performance

Oil and Grease: Oil and Grease: Avoid with film fill (contributes to fill Avoid with film fill (contributes to fill plugging, prevents proper seasoning).plugging, prevents proper seasoning).

Ammonia: Ammonia: Limit to 50Limit to 50 ppmppm if copper alloys are presentif copper alloys are present

Water Quality

Combinations of treatment chemicals may Combinations of treatment chemicals may cause reactions which reduce treatment cause reactions which reduce treatment effectivenesseffectivenessCertain chemicals such as surfactants,Certain chemicals such as surfactants,biodispersantsbiodispersants and antifoams may increase and antifoams may increase drift ratedrift rateConsult CT & WT vendors/consultantsConsult CT & WT vendors/consultants

Concentrations and Blowdown

Evaporating water leaves minerals, Evaporating water leaves minerals, concentrates over timeconcentrates over timeBlowdown of a small amount of water Blowdown of a small amount of water keeps concentration at desired levelkeeps concentration at desired levelC = (R x EPD + BD + D)/(BD + D)C = (R x EPD + BD + D)/(BD + D)


Example:Example:Evaporation = 0.08% circulating water Evaporation = 0.08% circulating water per degree of rangeper degree of rangeDrift = 0.02% of circulating water rateDrift = 0.02% of circulating water rateRange = 10 Deg FRange = 10 Deg FConcentrations = 5Concentrations = 5Blowdown = 0.18% of circulating water Blowdown = 0.18% of circulating water raterate


Range 1.5 2 2.5 3 4 5 65 0.78 0.36 0.23 0.21 0.11 0.08 0.0610 1.58 0.76 0.50 0.41 0.24 0.18 0.1415 2.38 1.16 0.77 0.61 0.37 0.28 0.2220 3.18 1.56 1.03 0.81 0.51 0.38 0.3025 3.98 1.96 1.30 1.01 0.64 0.48 0.3830 4.78 2.36 1.57 1.21 0.77 0.58 0.4635 5.58 2.76 1.83 1.41 0.91 0.68 0.54

Based on: 0.02 % drift rate and 0.08 % evaporation rate

Operation for System Efficiency

Condensing Water Temperature

•• 3 GPM/TR (95°/85°/78°)3 GPM/TR (95°/85°/78°)•• 2 GPM/TR (105°/85°/78°)2 GPM/TR (105°/85°/78°)•• Lower condensing Lower condensing

temperatures, fans full, temperatures, fans full, gives coldest water at gives coldest water at chillerchiller

•• Chiller energy savings Chiller energy savings almost always outweighs almost always outweighs tower fan energy tower fan energy consumption

0.0350.04

0.0450.05

0.0550.06

0.0650.07

0.0750.08

0.085

80 81 82 83 84 85 86 87

3 GPM/TON 2 GPM/TON

DESIGN COLD WATER TEMP. — (°F)

HP

per

TON

DESIGN COOLING TOWER FAN HP VARIATIONFAN HP PER TON OF LOAD

(BASIS: 75°F WET-BULB)

consumption

Capacity Control Methodologies

•• Capacity Control DampersCapacity Control Dampers•• MultiMulti--speed Motorsspeed Motors•• Variable Frequency DrivesVariable Frequency Drives•• Single Speed Fan CyclingSingle Speed Fan Cycling•• Free CoolingFree Cooling•• Fans full Speed Fans full Speed –– Run Wild Run Wild

Capacity Control Dampers

•• Offers precise system controlOffers precise system control•• No fan power savingsNo fan power savings

Effect of Fan Speed on Capacity

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80 90 100

CAPACITY (AIRFLOW) REQUIRED POWER

PERCENT OF DESIGN FAN SPEED

PERCENT

FAN CHARACTERISTICSCAPACITY & HORSEPOWER RELATIVE TO SPEED

Single Speed, Full Power

45505560657075808590

20 30 40 50 60 70 80

10°F RANGE

WET BULB TEMPERATURE — (°F)

COLD

WATER

TYPICAL COOLING TOWER PERFORMANCESINGLE CELL TOWER — SINGLE SPEED FAN

Two Speed

45505560657075808590

20 30 40 50 60 70 80

FULL SPEED HALF SPEED


COLD

WATER

TYPICAL COOLING TOWER PERFORMANCESINGLE CELL TOWER — TWO SPEED FAN

(10°F RANGE)

Two Cell, Two Speed

45505560657075808590

20 30 40 50 60 70 80

FULL SPEED 1 HALF, 1 FULL HALF SPEED


COLD

WATER

TYPICAL COOLING TOWER PERFORMANCETWO CELL TOWER — TWO SPEED FANS

(10°F RANGE)

35° 45° 55° 65° 75° 85°

80%

60%

40%

20%

0

90°

80°

Cold Water °F

100%

100%

Control Temperature

Variable FrequencyDrive Fan

Control

Variable Frequency

Compressor Impact

45505560657075808590

20 30 40 50 60 70 80

10°F RANGE


COLD

WATER


Region for influencing compressor horsepower.

Compressor Power

8486889092949698

100

70 75 80 85

COMPRESSOR HORSEPOWER

COLD WATER TEMPERATURE (°F)

PERCENT

POTENTIAL COMPRESSOR HP REDUCTIONSCONSTANT LOAD — REDUCING CONDENSER WATER TEMPERATURE

This is a “rule of thumb” curve. Verify actual reductions with chiller manufacturer.

Free Cooling Region

45505560657075808590

20 30 40 50 60 70 80

10°F RANGE


COLD

WATER


Region for consideration of “free cooling”.

“Free Cooling”“Free Cooling”••When the tower can produce sufficiently When the tower can produce sufficiently cold water without the chiller.cold water without the chiller.

••Direct free cooling..Direct free cooling..

••Indirect free cooling..Indirect free cooling..

Free Cooling Operation

Graph assumes that the system will go to free cooling when the tower is capable of producing 50°F or colder water.

4045505560657075808590

20 30 40 50 60 70 80

CHILLER ON CHILLER OFF


COLD

WATER

TYPICAL COOLING TOWER PERFORMANCEFULL LOAD — FULL FAN SPEED — FULL WATER FLOW

Benefit Depends on Location

0

2000

4000

6000

8000

10000

-10 0 10 20 30 40 50 60 70 80

ANNUAL HOURS INDICATED W.B. WILL NOT BE EXCEEDED


HOURS

WET BULB OCCURRANCEDES MOINES VICINITY

operation and maint for energy efficiency

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