PresentationPresentationOnOn

Design, Operation & Maintenance Design, Operation & Maintenance

of Cooling Towers of Cooling Towers of Cooling Towers of Cooling Towers

ATAT

Date: 29 July 2008Date: 29 July 2008

Power Management InstitutePower Management Institute

ByBy

S. Ramasundar &S. Ramasundar &

Mahesh KumarMahesh Kumar

PaharpurPaharpur Cooling Towers Ltd.Cooling Towers Ltd.

KolkataKolkataKolkataKolkata

Road MapRoad Map

BriefBrief HistoryHistory OfOf PaharpurPaharpur CoolingCooling TowersTowers LtdLtd..

PCTPCT AssociationAssociation WithWith NTPCNTPC

LatestLatest DevelopmentDevelopment InIn DesignDesign OfOf CoolingCooling TowersTowers

TipsTips forfor BetterBetter PerformancePerformance ofof CoolingCooling TowersTowersTipsTips forfor BetterBetter PerformancePerformance ofof CoolingCooling TowersTowers

ProblemsProblems inin CoolingCooling TowersTowers andand TheirTheir ImpactImpact onon TowerTower PerformancePerformance

InspectionInspection andand MaintenanceMaintenance ScheduleSchedule ofof CoolingCooling TowersTowers

PreferredPreferred CoolingCooling WaterWater ConditionCondition LimitsLimits

AA CaseCase StudyStudy OnOn MaintenanceMaintenance ProblemProblem atat NTPCNTPC KanihaKaniha

AnnualAnnual MaintenanceMaintenance ContractsContracts forfor CoolingCooling TowerTower MaintenanceMaintenanceAnnualAnnual MaintenanceMaintenance ContractsContracts forfor CoolingCooling TowerTower MaintenanceMaintenance

BriefBrief NoteNote onon TreatedTreated TimberTimber CoolingCooling TowersTowers..

Brief History of Paharpur Cooling TowersBrief History of Paharpur Cooling Towers

PaharpurPaharpur CoolingCooling TowersTowers LtdLtd.. -- AnAn ISOISO 90019001 CompanyCompany

CoreCore competencycompetency inin turnkeyturnkey contractscontracts forfor supplysupply ofof coolingcooling towerstowers

-- TreatedTreated timbertimber (Cross/(Cross/ countercounter flow)flow)

-- RCCRCC (Cross/(Cross/ countercounter flow)flow)

-- NaturalNatural draftdraft (Hyperbolic)(Hyperbolic)NaturalNatural draftdraft (Hyperbolic)(Hyperbolic)

-- GRPGRP PultrudedPultruded sectionsection

FirstFirst CoolingCooling TowerTower ofof 77 cellscells (Treated(Treated Timber)Timber) constructedconstructed inin 19591959 atat

29 June 2008

RourkelaRourkela SteelSteel PlantPlant;; ThisThis CoolingCooling TowerTower isis stillstill inin operationoperation..

Total Nos of Towers Constructed Till Date Total Nos of Towers Constructed Till Date Including Jobs in HandIncluding Jobs in HandIncluding Jobs in HandIncluding Jobs in Hand

Treated Timber 586

Total no of Cooling Towers

Cross Flow RCC 522

C t FlTreated Timber 93

Cooling Towers(1709)*

Counter Flow

RCC 479

18Natural Draft Pultruted FRP 18Natural Draft

RCC 11* Includes jobs in hand as on 12/06/2008* Includes jobs in hand as on 12/06/2008

29 June 2008 4

PCT Association With NTPCPCT Association With NTPC

N fN f N fN fS. N.S. N. LocationLocation Order No.Order No. ModelModel No of No of towerstowers Order No.Order No. ModelModel No of No of

towerstowers

11 AntaAnta 8787--22--917917 15121512--11(15'AT)11(15'AT) 11

22 AuraiyaAuraiya 8888--22--902A902A 8364283642--3.53.5--18B18B 22

33 BadarpurBadarpur 7979--22--291291 15121512--0909 11

44 BahrBahr 0505--2I2I--0118 A0118 A 8664186641--18V18V--1212 66 ++ 0505--2I2I--0118 G0118 G 8363683636--18V18V--0303 11

55 DadriDadri 9090--22--910A910A 8364283642--4.04.0--18B18B 22 ++ 0707--2I2I--0082 B0082 B ND TowerND Tower 11

66 FaridabadFaridabad 9898--2I2I--00160016 8424284242--4.04.0--18B18B 11

77 GandharGandhar 9292--22--926926 8484884848--4.04.0--20B20B 11

88 JamshedpurJamshedpur 0202--2I2I--00450045 14091409--02(18'AT)02(18'AT) 11

99 KahalgaonKahalgaon 8888--22--909A909A 1512X1512X--1010 44 ++ 0404--2I2I--0030A0030A 8664286642--6.06.0--1010 66++ 0404 2I2I 0030G0030G 8303083030 6 06 0 0303 11++ 0404--2I2I--0030G0030G 8303083030--6.06.0--0303 11

1010 RamagundamRamagundam 8181--22--091A091A 15141514--0808 33 ++ 0202--2I2I--00290029 8664286642--6.06.0--10 10 44

1111 SipatSipat 0404--2I2I--0025A0025A 8664286642--6.06.0--1010 44 ++ 0404--2I2I--0025D0025D 8243082430--6.06.0--0303 11

29 June 2008

1212 TalcherTalcher 0000--2I2I--00030003 8604286042--5.05.0--1010 88 ++ 0707--2I2I--00850085 65166516--00--1212 11

1313 UncharUnchar 9696--22--905A905A 8364283642--4.04.0--18B18B 22 ++ 0404--2I2I--00430043 8664286642--6.06.0--0909 11

1414 VindhyachalVindhyachal 8585--22--903A903A 15141514--0909 66 ++ 9595--22--958A958A 8644886448--4.04.0--0909 445

Latest Development In Design Of Latest Development In Design Of Cooling TowersCooling Towers

PultrudedPultruded FROFRO CoolingCooling TowersTowers

ConcreteConcrete towerstowers (Cross(Cross flow/flow/ countercounter flow)flow) withwith GRPGRP FanFan cylindercylinderConcreteConcrete towerstowers (Cross(Cross flow/flow/ countercounter flow)flow) withwith GRPGRP FanFan cylindercylinder

SSSS channelschannels forfor BottomBottom supportsupport inin countercounter flowflow towerstowers replacedreplaced withwith

aa.. RCCRCC postpost andand FRPFRP channelschannels

bb.. RCCRCC postpost andand RCCRCC beamsbeams

ThreeThree passpass PVCPVC eliminatorseliminators insteadinstead ofof twotwo passpass PVCPVC // ACBACB eliminatorseliminators..

DriftDrift lossloss inin threethree passpass PVCPVC eliminatoreliminator isis 00..005005%% asas comparedcompared toto 00..0505%%

forfor twotwo passpass eliminatorseliminators.. ReducedReduced driftdrift lossloss meansmeans lessless makeupmakeup waterwater..

•• PCTPCT hashas alsoalso developeddeveloped highhigh temperaturetemperature resistantresistant fillfill materialmaterial forfor

engineeringengineering plasticsplastics forfor splahsplah andand filmfilm typetype fillfill whichwhich cancan withstandwithstand

29 June 2008

temperaturetemperature uptoupto 10010000CC..

•• FRPFRP GratingsGratings inin coolingcooling towerstowers inin placeplace ofof MSMS HDGHDG gratingsgratings..6

Latest Development In Design Of Latest Development In Design Of Cooling TowersCooling Towers

CarbonCarbon fiberfiber drivedrive shaftshaft

a. Tube all glassa. Tube all glass

b. Tube all carbon

c. Tube Hybrid (50% Glass fiber + 50% Carbon fiber)

Advantages:Advantages:

a. Light weight – easy to handle

b Hi h t th t i ht tib. Higher strength to weight ratio

c. Highly corrosion resistant and hence longer life.

d. increased bearing life of motor/ gear box because of reduced g g

weight.

Combination of Splash type and Film type fill in cross flow towersCombination of Splash type and Film type fill in cross flow towers

Bigger fans up to 11 meter diameter Bigger fans up to 11 meter diameter 29 June 2008 7

Tips for Better Performance of Cooling TowersTips for Better Performance of Cooling Towers

Water level in all the distribution decks of cross flow towers and water flow in Water level in all the distribution decks of cross flow towers and water flow in

all cells of counter flow towers should be equal and uniformall cells of counter flow towers should be equal and uniformall cells of counter flow towers should be equal and uniform.all cells of counter flow towers should be equal and uniform.

After adjusting flow the lock handle of flow control valve in cross flow towers After adjusting flow the lock handle of flow control valve in cross flow towers

should be in locked position. If this is not done, this will lead to damage of should be in locked position. If this is not done, this will lead to damage of

stem guide and FC valve cannot be operated.stem guide and FC valve cannot be operated.

Distribution deck should be clean with all nozzles in position. Excess water Distribution deck should be clean with all nozzles in position. Excess water

circulation leads to over flow from louver side in cross flow towers there by circulation leads to over flow from louver side in cross flow towers there by

causing fill damage. causing fill damage.

29 June 2008 8

Tips for Better Performance of Cooling TowersTips for Better Performance of Cooling Towers

For better performance of gear box oil to be used in the gear box should be For better performance of gear box oil to be used in the gear box should be

as per manufacturer’s specification only Specification of oil should not be as per manufacturer’s specification only Specification of oil should not be as per manufacturer s specification only. Specification of oil should not be as per manufacturer s specification only. Specification of oil should not be

changed without concurrence of the manufacturer of gear box.changed without concurrence of the manufacturer of gear box.

New gear box is supplied with some oil in the gear box when despatched. New gear box is supplied with some oil in the gear box when despatched.

Before installation this oil must be drained out and the gear box flushed twice Before installation this oil must be drained out and the gear box flushed twice

with flushing oil before new oil is filled in. Flushing oil once used should be with flushing oil before new oil is filled in. Flushing oil once used should be

discarded.discarded.

In case of gear box in use, the insides of gear box should be cleaned once In case of gear box in use, the insides of gear box should be cleaned once

with flushing oil before changing oil.with flushing oil before changing oil.

Operation and maintenance practices as mentioned in the manuals should be Operation and maintenance practices as mentioned in the manuals should be

followed strictly. followed strictly. 29 June 2008 9

Problems in Cooling Towers and Their ImpactProblems in Cooling Towers and Their Impacton Tower Performance on Tower Performance

Contaminated water Contaminated water –– clogging of V bars clogging of V bars –– reduced splashing reduced splashing –– affects thermal affects thermal

performance and can lead to collapse of fill.performance and can lead to collapse of fill.performance and can lead to collapse of fill.performance and can lead to collapse of fill.

Contaminated water Contaminated water –– clogging of Fill packs clogging of Fill packs –– reduced surface area reduced surface area –– affects affects

thermal performance and can lead to collapse of support and fills.thermal performance and can lead to collapse of support and fills.

Clogging of eliminators Clogging of eliminators –– restricts air flow restricts air flow –– affecting tower performance affecting tower performance

Clogged nozzles Clogged nozzles ––unequal distribution of water unequal distribution of water –– affects thermal performance.affects thermal performance.

N l Cl b t d N l Cl b t d l di t ib ti f t l di t ib ti f t ff t ff t Nozzles Clean but caps removed Nozzles Clean but caps removed –– unequal distribution of water unequal distribution of water –– affects affects

thermal performancethermal performance

Algae formation on fill Algae formation on fill –– reduces splashing reduces splashing –– affects thermal performanceaffects thermal performancegg p gp g pp

Replacement of originally supplied fans with hollow blade fans Replacement of originally supplied fans with hollow blade fans –– leads to leads to

thermal performance problems.thermal performance problems.

29 June 2008 10

Problems in Cooling Towers and Their ImpactProblems in Cooling Towers and Their Impacton Tower Performance on Tower Performance

Excess oil in gear boxes /Oil seal leakExcess oil in gear boxes /Oil seal leak -- Common problemCommon problem–– oil leakage oil leakage ––

mixes with water mixes with water –– can affect thermal performance.can affect thermal performance.

Incorrect fitting of NBM inserts Incorrect fitting of NBM inserts –– vibration in drive shafts. vibration in drive shafts.

NBM inserts are pressure fitted and hence to be lubricated with NBM inserts are pressure fitted and hence to be lubricated with soap solution soap solution

only. GREASE / OIL SHOULD NOT BE USED AS LUBRICANT.only. GREASE / OIL SHOULD NOT BE USED AS LUBRICANT.yy

Fan pitch angle setting Fan pitch angle setting –– Unequal pitch angle Unequal pitch angle -- leads to vibration leads to vibration

Center line of fan / gear box not matching with the centre line of fan cylinder Center line of fan / gear box not matching with the centre line of fan cylinder Center line of fan / gear box not matching with the centre line of fan cylinder Center line of fan / gear box not matching with the centre line of fan cylinder

–– unequal tip clearance.unequal tip clearance.

Track variations of fan blade not within limits Track variations of fan blade not within limits –– leads to vibration in fan.leads to vibration in fan.

Problem with water quality Problem with water quality –– proper water treatment measures required.proper water treatment measures required.29 June 2008 11

Inspection & Maintenance Schedule (General Inspection & Maintenance Schedule (General recommendations)recommendations)

(More frequent inspection and n mbe

rs

ks(More frequent inspection and Maintenance may be desirable)

Stru

ctur

e

Fan

Mot

or

DS

& G

uard

s

Gea

r Red

ucer

E

limin

ator

sFi

llC

W b

asin

HW

Dis

t.Fl

oat v

alve

Suc

tion

scre

en

Valv

esS

truct

ural

Mem

Cas

ing

fan

Cyl

inde

rS

tairs

, Doo

rs,

Dav

its, D

erric

k

S G

1 Inspect for clogging M M W W2 Check for unusual noise D D D D3 Inspect keys, keyways and set screws S S S S4 Make sure vents are open S4 Make sure vents are open S5 Lubricate R S6 Check oil seals M7 Check operating oil levels D8 Check static oil level M8 Check static oil level M9 Check oil for water and sludge M

10 Change oil, at least S11 Check fan blade tip clearance S12 Check water level D D

16 June 2008 12

12 Check water level D D13 Check for leakage W S S S

Inspection & Maintenance Schedule (General Inspection & Maintenance Schedule (General recommendations)recommendations)

(More frequent inspection and M i t b d i bl ) s er

een em

bers

s,

icks

Maintenance may be desirable)

Stru

ctur

e

Fan

Mot

or

DS

& G

uard

Gea

r Red

uce

Elim

inat

ors

Fill

C W

bas

inH

W D

ist.

Floa

t val

ve

Suc

tion

scre

Valv

esS

truct

ural

MC

asin

gfa

n C

ylin

der

Sta

irs, D

oors

Dav

its, D

err

14 Inspect for general condition S S S S Y S Y S Y S S S Y S S S15 Tighten loose bolts S S S S Y R S16 Clean R R R R R R S R R R R17 Repaint R R R R R R18 Rebalance R R19 Completely open and close S20 Inspect for proper spray formation M21 Inspect / repair for safe use Y Y Y22 Inspect and repair before each use R23 Inspect Structure for any deterioration Q

D - daily; W - weekly; M - monthly; Q - quarterly; S - semi-annually; Y - yearly; R - as required

29 June 2008 13

Note: In the case of concrete cooling towers, inspect the concrete members for cracks and exposed rebarsannually and repaint all originally painted surfaces as required

Preferred Cooling Water Condition LimitsPreferred Cooling Water Condition Limits

pH : 6.5 to 8.5

Temperature : 1250 F

Langelier Separation Index : 0.0 to 1.0

M-Alkalinity : 100 to 500 ppm as CaCO3

Silica : 150 ppm as SiOSilica : 150 ppm as SiO2

Iron : 3 ppm max.

Sulphides : More than 1 ppm can be corrosive to copper , Iron, steel and G. steel

Manganese : 0.1 ppm max.

Ammonia : 50 ppm max if copper alloys present

Free Chlorine : Wood structure: 1 ppm (Shock) Or 0.4 ppm (Continuously)

Organic Solvents : Attack plastics and promote bio-growth. <50ppm may be acceptable.

TDS > 5000 ff t th l f & d t i t l t d iTDS : > 5000 ppm affect thermal performance & detrimental to wood in

alternately wet/dry zones such as fan deck and louver face.

29 June 2008 14

Preferred Cooling Water Condition LimitsPreferred Cooling Water Condition Limits

Individual Ions: Maximum

Cations: Ca : 800ppm as CaCO3

Mg : Depends on pH and Silica level

Na : No Limit

Anions: Chlorides : 750 pppm as NaCl (455 ppm as Cl-)

Sulphates : 800 as CaCO3 s

Nitrates : 300 ppm as NO3 (Bacteria Nutrient)

Carbonates/ Bicarbonates : 300 ppm as CaCO3 max for Wood

Biological / BacteriaBacteria counts listed below relate to maintaining fill thermal efficiency only

29 June 2008

Biocidal Treatment is required for all cooling tower installations

15

Preferred Cooling Water Condition LimitsPreferred Cooling Water Condition Limits

Fill Type Aerobic bacteria Std. Plate Count

TSS Sulphides

Total Suspended Solids

MC67 10,000CFU/ml <25ppm preferred* 0.5 ppm

Splash fill 1000000CFU/ml target level No specific limit Not Applicable

* i h b id d b b i l i i* Higher TSS can be considered on a case-by-case basis. Consult PCT Engineering

Miscellaneous Solids and Nutrients

F fil fill id fib il f tt t t i l hi h l fill d id t i t hFor film fill avoid fibrous, oily, greasy, fatty or tarry material which can plug fill and avoid nutrients such as

glycols, alcohols and sugars which promote bacterial growth.

For splash fill, oil and grease levels greater than 10 ppm can adversely affect thermal performance.

Special Note: In general, do not use film fill in steel plants, Pulp & Paper Mills Food Processing Operations or

similar applications unless leaks and contamination by airborne or waterborne particulates oil or fibers are extremely

29 June 2008

unlikely. If film fill is used, biological growth control must be stringent an diligent.

16

A Case Study on Maintenance Problem A Case Study on Maintenance Problem

at at

NTPC NTPC -- KanihaKaniha

29 June 2008 17

Annual Maintenance Contracts for Cooling Annual Maintenance Contracts for Cooling Tower MaintenanceTower Maintenance

Paharpur is having AMC with Paharpur is having AMC with

a.a. NTPC NTPC –– TalcherTalcher b.b. NTPC NTPC –– TandaTanda

c.c. WBPDCL WBPDCL –– KolaghatKolaghat d.d. WBPDCL WBPDCL –– BakreswarBakreswar

NTPC NTPC Si tSi t (U d ti ti ) (U d ti ti ) ff DVC DVC DDe.e. NTPC NTPC –– SipatSipat (Under negotiation) (Under negotiation) f.f. DVC DVC –– DurgapurDurgapur

g.g. DPL DPL -- DurgapurDurgapur

Advantages of AMC:Advantages of AMC:gg

Maximum cell availabilityMaximum cell availability

Correct fitment of original spare partsCorrect fitment of original spare parts

Easy availability of original spare parts as per rate contract Easy availability of original spare parts as per rate contract

(Local manufacturer’s supply does not conform to OEM quality criteria.)(Local manufacturer’s supply does not conform to OEM quality criteria.)

29 June 2008 18

Why Treated Timber Cooling TowersWhy Treated Timber Cooling Towers

Cost of RCC Cooling Tower is much more than timber cooing tower.Cost of RCC Cooling Tower is much more than timber cooing tower.g gg g

Susceptible to corrosion & Prone to attack by chemicals.Susceptible to corrosion & Prone to attack by chemicals.

Repair of structure is very costly and time takingRepair of structure is very costly and time takingRepair of structure is very costly and time taking.Repair of structure is very costly and time taking.

Treated timber cooling tower ideally suited for fertilizer and Treated timber cooling tower ideally suited for fertilizer and chemical plants and for salt water duty.chemical plants and for salt water duty.

Erection time very much less compared to RCC tower.Erection time very much less compared to RCC tower.

Each part of timber cooling tower is easily accessible and hence Each part of timber cooling tower is easily accessible and hence Each part of timber cooling tower is easily accessible and hence Each part of timber cooling tower is easily accessible and hence easy to repair and maintain the tower. easy to repair and maintain the tower.

27 June 2008 19

Timber Used In Cooling TowersTimber Used In Cooling Towers

&&

Treatment of TimberTreatment of Timber

Preservatives Options:- CCA : Cromated Copper Arsenate

- ACC : Acid Copper Chrome

- ACA : Ammoniated Copper ArsenateACA : Ammoniated Copper Arsenate

Paharpur Carries out Treatment at Kandla factory as per CTI STD – 112 for US Species and as per IS 401 for rest of the species

2027 June 2008

per IS 401 for rest of the species

Note: CCA is the best Preservative treatment. Also specified in CTI -STD 112

Class 400 / F400: Counter Flow Industrial Cooling Tower

Structure : Treated Wood / Pultruted GRP

Fill : Film / Splash type

Models : 4 A B - X - Y / F 4 A B - X - Y

Model Code Particulars

4 Structure: Treated WoodF4 St t P lt t d GRP

Model Specifications: F4 Structure: Pultruted GRPA Breadth of Cell: No of bays each of 6 ft

B Length of Cell: No of bays each of 6 ft

16 June 2008 21

X Height of Fill

Y No. of Cells

Class 500 : Cross flow Industrial Cooling Tower

Structure : Treated WoodStructure : Treated Wood

Fill : Splash type PVC

Models : 5 A B - XV - Y

Model Code Particulars

A Splash Fill Height ( A x 3 ft)

B Length of Cell: = No of bays X 4 ft

X Air Travel ( X + 8 ft)

V V Bar Fill

Model Specifications:

16 June 2008 22

V V Bar Fill

Y No. of Cells

Class 600 : Cross flow Industrial Cooling Tower

Structure : Treated Wood

Fill : Splash type PVC

Models : 6 A B - X - Y

Model Code Particulars

A Height of Fill ( A x 3 ft)

L th f C ll 1 20’ 2 24’ 3 28’ 4 32’ 15 36’

Model Specifications:

B Length of Cell: 1=20’, 2=24’, 3=28’, 4=32’, 15=36’, 16=40’, 17=44’

XAir Travel : -3 = 16’ ( With 1-03/8” in 6’ ) slope

-4 = 18’ ( With 2” in 6’ ) slope5 = 20’ ( With 2” in 6’ ) slope

16 June 2008 23

p f-5 = 20 ( With 2 in 6 ) slope

Y No. of Cells

29 June 2008 24