PROJECT

PRESENTED BY:- Abhimanyu Meena

Karan Manek

Mayur Solanki

Mohamed Zaid Afzal

STUDENT OF: – CHEMICAL ENGINEERING DEPARTMENT,

SVNIT, Surat.

MENTOR:- Mr.CHANCHLESH KABRA

ACKNOWLEDGEMENTSIndustrial Training is an integral part of engineering curriculum providing engineers with first hand and practical aspects of their studies. It gives us the knowledge about the work and circumstances existing in the company. It gives us great pleasure to have completed my project at Gas Processing Plant of ONGC at Hazira and submitting the project report for the same. I express my deep sense of gratitude to Mr.CHANCHLESH KABRA for giving me the project on cooling tower.My sincere thanks to Mrs. D. SWAROOPA, E.E. (P)-RE CELL, ONGC Hazira for allotting me appropriate schedule, guiding me through various aspects, functioning and processing of plant, and giving their effective coordination for undertaking the training. I thank Oil and Natural Gas Corporation Limited, Hazira for giving me an opportunity to have an industrial exposure under the guidance of the experts. I also thank all of them who have directly or indirectly helped us during the tenure of our training. Sincerely thanking all of the above once again, we hope to continue to take the guide from the aforementioned in near future. It has been a great experience for me.

Abstract The main purpose of the project is to work on cooling tower of ONGC Plant , Hazira . The total number of cooling tower are four.There are two types of cooling tower in ONGC Plant.a) Induced counter flow b) Induced cross flow The more efficient is induced cross flow as compare to the counter flow.The number of towers are four in which one is induced counter flow (Phase II) and three are induced cross flow(Phase I , Phase III , Phase III(A)).

The project is based on the induced cross flow (Phase I).

The height of tower is 50 meters.

Mild steel are been used in most of the piping.

Stainless steel is used for acid pass piping.

Cooling Tower

1.1.Cooling Towers for RefrigerationAn important device used in any refrigeration or air conditioning system is a condenser. A condenser is used in the high pressure side of a refrigeration or air conditioning system to convert the high-pressure vapour refrigerant from the compressor into liquid refrigerant. The medium used in a condenser may be water or air, depending upon the application. In the case of water cooled condensers, the warm water being pumped by the condenser should be cooled with the help of cooling towers so that the same water may be re-circulated to the condenser.

1.2 Principle of Operation for Cooling TowersThe principle of operation of cooling towers is very similar to that of the evaporative type of condensers, in which the warm water gets cooled by means of evaporation. Water evaporates as a result of the hot water droplet coming in contact with the air (which is being pumped out by means of a fan). This evaporating water also absorbs the latent heat from the water surrounding it. By losing latent heat, the water is cooled.

1.3.Classification Of Cooling Tower

1.4TYPES OF COOLING TOWER

1.4.1.Natural Draft Cooling Towers

->Hot air moves through tower

->Fresh cool air is drawn into the tower from bottom

->No fan required

->Concrete tower <200 m

->Used for large heat duties

1.4.2.Mechanical Draft Cooling Towers

->Large fans to force air through circulated water

->Water falls over fill surfaces: maximum heat transfer

->Cooling rates depend on many parameters

->Large range of capacities

->Can be grouped, e.g. 8-cell tower

1.4.3.Types Of Mechanical Draft Cooling Tower

(A) Forced Draft

(B) Induced Draft Cross Flow

(C) Induced Draft Counter Flow

(A) Forced Draft Cooling Towers

Air blown through tower by centrifugal fan at air inlet

Advantages:-suited for high air resistance & fans are relatively quietDisadvantages:- recirculation due to high air-entry and low air-exit velocities

(B) Induced Draft Cross Flow

=>According To Flow Direction,There is Tow Types:

(A)Induced Draft Cross flow Tower (B)Induce Draft Counter flow Tower

(A)Induced Draft Cross flow Tower (B)Induce Draft Counter flow Tower

->Hot water enters at the top ->Water enters top and passes over fill

->Air enters at bottom and exits at top ->Air enters on one side or opposite sides

->Uses forced and induced draft fans ->Induced draft fan draws air across fill

Advantage : less recirculation than forced draft towers

Disadvantage : fans and motor drive mechanism require weather-proofing.

1.8.We Need To Maintain 16 Parameters

(1) PH Balance:- Maintain 7 to 8 (9) Free Chlorine

(2) Conductivity:- Maximum 2000 (10) Total Phosphate

(3) Total Hardness:- Maximum 350 (11) Ortho Phosphate

(4) Calcium Hardness (12) Inorganic

(5) Magnesium Hardness (13) Organic

(6) P-Alkality:- Most Probably Nill (14) TDS

(7) M-Alkality:- Most Probably Nill (15) Zinc

(8) Total Chlorides (16) Turbidity

1.9.MEASURED PARAMETERS

(A) Wet bulb temperature of air

(B) Dry bulb temperature of air

(C) Cooling tower inlet water temperature

(D) Cooling tower outlet water temperature

(E) Exhaust air temperature

(F) Electrical readings of pump and fan motors

(G) Water flow rate

(H) Air flow rate

1.5.Cooling Tower Construction Materia

1.5.1.Fills

In a cooling tower, hot water is distributed above fill media which flows down and is cooled due to evaporation with the intermixing air. Air draft is achieved with use of fans. Thus some power is consumed in pumping the water to a height above the fill and also by fans creating the draft.

An energy efficient or low power consuming cooling tower is to have efficient designs of fill media with appropriate water distribution, drift eliminator, fan, gearbox and motor. Power savings in a cooling tower, with use of efficient fill design, is directly reflected as savings in fan power consumption and pumping head requirement.

Heat exchange between air and water is influenced by surface area of heat exchange, time of heat exchange (interaction) and turbulence in water effecting thoroughness of intermixing. Fill media in a cooling tower is responsible to achieve all of above.

=> Splash and Film Fill Media: As the name indicates, splash fill media generates the required heat exchange area by splashing action of water over fill media and hence breaking into smaller water droplets. Thus, surface of heat exchange is the surface area of the water droplets, which is in contact with air.

=> Film Fill and its Advantages : In a film fill, water forms a thin film on either side of fill sheets. Thus area of heat exchange 7. Cooling Tower Bureau of Energy Efficiency 144 is the surface area of the fill sheets, which is in contact with air.Due to fewer requirements of air and pumping

head, there is a tremendous saving in power with the invention of film fill. Recently, low-clog film fills with higher flute sizes have been developed to handle high turbid waters. For sea water, low clog film fills are considered as the best choice in terms of power saving and performance compared to conventional splash type fills.

Examples:-PVC Honeycombed : This Is Film Fill system designed to significantly reduce the risk of biological fouling without sacrificing high performance heat transfer.

The film fill is a bottom support low-clog log fill configuration. Open, angular cross corrugations allow debris and biological growth foulant to pass, while providing maximum surface area and turbulence to develop efficient heat transfer. Texturing creates thermal capability improvement with little effect on fouling. The fills offers low pressure drop in an aerodynamic, durable design.

Product Code: PFT-001050

Product Code: PFT-001052 Product Code: PFT-001050 Product Code: PFT-001061

Product Code: PFT-001072 Product Code: PFT-001073 Product Code:PFT-001202

Parameters Splash Fill Film Fill Low Clog Film Fill

Possible L/G Ratio 1.1 – 1.5 1.5 – 2.0 1.4 – 1.8

Effective Heat Exchange Area

30 – 45 m2/m3 150 m2/m3 85 - 100 m2/m3

Fill Height Required 5 – 10 m 1.2 – 1.5 m 1.5 – 1.8 m

Pumping Head Requirement

9 – 12 m 5 – 8 m 6 – 9 m

Quantity of Air Required High Much Low Low

1.5.2.Drift Eliminators

Application : These capture water droplets entrapped in the air stream that otherwise would be lost to the atmosphere.

PERFECT offers Drift Eliminators, made out of rigid PVC, are designed to remove entrained particles from air steam efficiently, with minimum pressure drop, thereby reducing the fan power requirement when the air passes through the Drift Eliminator.

Water droplets are separated from the air drift at the three direction change points on the drift eliminator. Our drift eliminator provides a cellular rugged structure with a very low pressure drop. This results in high drift elimination efficiency while exerting minimum driving force on fan. http://www.perfectcoolingtowers.com/PVC%20HONEYCOMB%20FILLS.html

1.5.3.Sprinklers

Application : To Distributes Hot Water Over Entire Space Of Fillers.

Product Code :PFT-002035 Product Code: PFT-002060 Product Code: PFT-002140

Product Code: PFT-002020 Product Code: PFT-002030 Product Code: PFT-002050

Perfect offers cooling tower sprinkler with rotary head and sprinkler pipe distributes the hot water over the entire space of the filler. Sprinkler pipes are non corrosive, require low pressure to operate and assure uniform water flow with minimal operating pump head.

Consists of a set of sprinkler pipes and one sprinkler head that is mounted on top of the stand pipe on the cooling tower. The sprinkler is rotated by the pressure of circulating water. There are numerous holes in the sprinkler pipe to allow the water to jet out as the pump impacts rotation.http://www.perfectcoolingtowers.com/cooling_tower_sprinkler.html

1.5.4.Nozzel

Application : These provide the water sprays to wet the fill. Uniform water distribution at the top of the fill is essential to achieve proper wetting of the entire fill surface. Nozzles can either be fixed in place and have either round or square spray patterns or can be part of a rotating assembly as found in some circular cross-section towers.

=>High Performance Nozzle

The Variable Flow Nozzle solution is not only simple, but it can be applied to both existing and new cooling towers. And not just cooling towers: fluid coolers, scrubbers, trickling filters and other water-cooled equipment. These nozzles are where the rubber meets the road in cooling tower performance. Increase your cooling tower efficiencey, maximize your towers efficincey. Increase your cooling by 10-20% by simply using NK-100 series variable flow nozzles.

NK-100 "Non clogging" square pattern spinning nozzle. 2" NPT with insert orifice selections. VariableFlow

NK-101 Square pattern spinning nozzle. 2" NPT

$35.00 each / 2" NPT thread

 The Variable Flow Nozzle has a spring-loaded orifice that automatically opens and closes with changing water pressure: in other words, the Variable Flow Nozzle doubles as a flow-control valve. That means you can turn OFF one or more of your cooling tower pumps as the wet bulb or load conditions dictate. This will conserve enormous amounts of energy.

NK-103 1" Variable Flow Nozzle

Square Pattern 3 x 3'

Low pump turn-down with out loosing nozzle performance. Reduces pumping head by as much as 2'

Acts like its own balancing valve

1.5.5.Louvers : Generally, cross-flow towers have inlet louvers. The purpose of louvers is to equalize air flow into the fill and retain the water within the tower. Many counter flow tower designs do not require louvers.

Anti-Splash Louvers Cost 882$ Per Cooling Tower Of 6 Unit.

1.5.6.Vibration Isolators

Application: Use To Reduce Vibration & Noise Control in Cooling Tower.

Vibration isolators for equipment which is subject to load variations and large external or torquing forces shall consist of large diameter laterally stabile steel springs assembled into welded steel housing assemblies designed to limit vertical movement of the supported equipment.

Housing assemblies shall be fabricated steel members and shall consist of a top load plate complete with adjusting and leveling bolts, vertical restraints, isolation washers and a bottom plate with internal non-skid noise isolation pads. Housing shall be electrozinc plated or hot dip galvanized for corrosion resistance. Housing should be designed to provide a constant free and operating height within 1/8" (0.06 mm).

Spring elements shall have a lateral stiffness greater than 1.2 times the rated vertical stiffness and shall be designed to provide a minimum of 50% overload capacity. Non-welded spring elements shall be polyester powder coated, and shall have a 1000 hr rating when tested in accordance with ASTM B-117.

Springs shall be selected to provide static deflections shown on the Vibration Isolation Schedule or as indicated on the project documents. Springs shall be color coded or otherwise identified to indicate load capacity. Vibration isolators shall be Model FLS, as manufactured by Kinetics Noise Control, Inc..> http://www.kineticsnoise.com/hvac/fls.html

1.5.7.Cooling Tower Motors

The company offers cooling tower motors that are specially designed flange mounted motors in totally enclosed construction to suit extreme environmental conditions. They are provided with special long shaft construction with external threaded end to directly mount the fan blades this also helps in the better cooling of the motor. Motors are compact in design & less in weight to facilitate easy maintenance

Cooling Tower Motors are specially designed ,flange mounted motors in totally enclosed construction to suit air conditioning & refrigeration industries. They are provided with special long shaft construction with external threaded end to directly mount the fan blades. This also helps in the better cooling of the motor. Motors are compact in design & less in weight to facilitate easy maintenance. Cooling Tower Motors available as standard catalouge designs or as custom built.

The Motor Bearings are sealed with grease for lifetime with seals on shaft to prevent moisture and debris from getting into the bearing.Provision for horizontal lifting is provided as standard, while vertical lifting for easy handling of motor during installation can be provided. They are available as standard catalogue designs or as custom built.> http://www.perfectcoolingtowers.com/cooling_tower_moters.html

Product Code: PFT-004141 Product Code: PFT-004142 Product Code: PFT-004143

1.5.8.Cooling Tower Fans

=>Fans must overcome system resistance, pressure loss:

->impacts electricity use

->Fan efficiency depends on blade profile

->Replace metallic fans with FBR blades (20-30% savings)

->Use blades with aerodynamic profile (85-92% fan efficiency)

=>Fan’s Blade Angle Is Change As Per Season.->In Winter and rainy seasons, the higher CT fan blade angle resulted in higher power consumption although the water temperature obtained was lower (which in these seasons, was not required for the process).

->The blade angle of the cooling tower CT was reduced from 50 0 to 45 0 . This resulted in reduced power consumption and rationalized air flow. For the

Summer season the blade angle remains the same as modified but the number of cooling tower cells under operation are increased.

By Using This Concept We Can Consume Financial benefits:Investment:- none

Annual cost savings:- Rs. 2.12 lakhs or US$ 4923 (= 105,840 kWh X Rs. 2 @ Rs 43/US$) (Energy Efficiency Guide

for Industry in Asia- www.energyefficiencyasia.org

1.5.9.Filter

Application: Filter At Inlet For Filtering Solid Dust And Feeding It Directly To

Shell.

Side stream filtration systems reduce suspended solids and debris in the systemcooling water, which leads to less fouling in the system. Decreasing suspended solids can also help reduce biological growth in the system because suspended solids are a good source of food for microbiological organisms.(2% Filter Water Use In Process)

1.5.10.Slump Level Maintain Techniques

There Is Two Types Of Techniques Use To Control Slum Level:

(1) Manually : By Using Of Simple Bypass Control Valve Fluid Flow & Other Person See The Slum Level.At Required Slum Level Flow Stop Or Reduce It Manually.

(2) Pneumatic Control Valve : By Using Of Special Type Of Automatically Control Valve Here We Automatically Slum Level Is Adjust.Here As Slum Level Is Decrease,Valve Automatically Open & Adjust It.

Here At ONGC Process We Have To Maintain 75m3 Slum Level.

1.5.12.Mixing Tank

->In Mixing Tank All Chemical Mix As Per Required.

->Must Be Non-Corrosive Wall Of Mixing Tank Requires.

1.6.TANK DETAILS (CAPACITY IN M^3)

(A) H2SO4

TYPE l C.T

I II III

MAIN STORAGE (H2) (Vt)

18.6 7.85 7.85

DOING 0.78 0.78 0.78

I II III III A3.2

1.0 1.0 1.0

(B)CHEMICALS (SHMP, HEDP, ZNSO4) DOSING TANK

=>CHEMICALS DETAILS

SR.NO

NAME MEANING FORM PURPOSE

1. HEDP HYDROXY ETHYLINE DI-PHOSPHONIC ACID

LIQUID ANTI SCALE FORMATION & FREE FLOW CREATION

2. SHMP SODIUM HEXA META PHOSPHATE

SOLID ANTI-CORROSIVE LAYER

3. ZnSO4 ZINC SULPHATE SOLID ANTI-CORROSIVE LAYER

4. H2SO4 SULPHURIC ACID LIQUID TO MAINTAIN PH LEVEL

5. Cl2 CHLORINE GAS TO KILL ALGAE, BACTERIA & FUNGUS

1.7.Make Up Water

As water evaporates in a cooling tower system, the water vapor enters the atmosphere while any dissolved solids remain behind, building concentration in the remaining water.

Most water treatment systems control this concentration by bleeding off the high concentration water, which is made up by fresh city water with a lower solid concentration. The amount of water that is bled off by the water treatment system is usually less than or equal to the amount of water that evaporates.

=>To compensate the water loss due to:

1. Evaporation,

2. Drift (water entrained in discharge vapor), estimated to be About 0.2% of water supply

3. Blow down (water released to discard solids).

1.8.Chlorine Leakage:

There Is Three Types Of Leakage Occurs:

(A) Body Leakage: On The Surface Of Tank,If Leakage Is Occurs Than By Using Of Liquid Ammonia We Detected Leakage

(B) Valve Leakage: At Valve of Chlorine Tank These Type Of Leakage Occurs.

(C) Plug Leakage: At Any Plug Of Chlorine Tank Or Process Its Occurs.

=>Chlorine Leakage Detection Absorption System with Neutralization

Chlorine Leakage Detection Absorption System with Neutralization support provided works as safety device that assists in reducing risk of spreading of chlorine gas into atmosphere. The system works by automatically absorbing/controlling heavy leaks from 100 kg/from 900 kg ton containers and absorb in caustic solution that allows creation of hypo chlorine which can be reused/used as cleaning agent. The neutralizing system comprises-

->Blower

->Absorption tower packed with ranching rings

->Alkali (NaOH) tanks

->Alkali circulation pump

->Piping valves

->Light weight FRP & PVC duct

We Use Chlorine Neutralization System Compostion:

Caustic    +    Water (40%) (60%)

1.9.Termidology Of Cooling Tower

Drift - Water droplets that are carried out of the cooling tower with the exhaust air. Drift droplets have the same concentration of impurities as the water entering the tower. The drift rate is typically reduced by employing baffle-like devices, called drift eliminators, through which the air must travel after leaving the fill and spray zones of the tower.

Blow-Out - Water droplets blown out of the cooling tower by wind, generally at the air inlet openings. Cooling water may also be lost, in the absence of wind, through splashing or misting. Devices such as wind screens, louvers, splash deflectors and water diverters are used to limit these losses.

Plume - The stream of saturated exhaust air leaving the cooling tower. The plume is visible when water vapor it contains condenses in contact with cooler ambient air, like the saturated air in one's breath fogs on a cold day. Under certain conditions, a cooling tower plume may present fogging or icing hazards to its surroundings.

Note that the water evaporated in the cooling tower operation process is "pure" water, in contrast to the very small percentage of drift droplets or water blown out of the air inlets.

Blow-Down - The portion of the circulating water flow that is removed in order to maintain the amount of dissolved solids and other impurities at an acceptable level - the higher the TDS concentration, the greater the risk of scale, biological growth and corrosion.

Approach - is the difference in temperature between the cooled-water temperature and the entering-air wet bulb temperature. Since cooling towers use an evaporative cooling design, cooling tower efficiency depends on the wet bulb temperature of the air.

Range - is the temperature difference between the water inlet and water exit.

Fill - Inside the tower, fills are added to increase contact surface as well as contact time between air and water. Thus they provide better heat transfer. The efficiency of the tower also depends on them. The two most common types of fill that currently in use are:

(a) Film type fill - causes water to spread into a thin film(b) Splash type fill - breaks up water and interrupts its vertical progress

The fill may consist of multiple, mainly vertical or sloped, wetted surfaces upon which a thin film of water spreads (film fill), or several levels of horizontal splash elements which create a cascade of many small droplets that have a large combined surface area (splash fill).

Recirculation - is a percentage of the hot, humid discharge air entering back into the inlet air stream thereby increasing the air inlet wet bulb temperature to a value higher than that of the ambient air condition. http://www.iwc.co.za/Common-Industry-

Terms.html

1.10.PERFORMANCE PARAMETERS

(A) Range: Hot Water Temp (Inlet) – Cold Water Temp (Outlet)

(B) Approach: Cold Water Temp (Outlet) - WBT

(C) Effectiveness: Rang / (Range+Approach)

(D) Cooling capacity: The process of cooling is called refrigeration. Refrigeration or cooling capacity is measured in tons.

A water-chiller refrigeration ton is defined as:

1 Ton Refrigeration = 1 TONScond = 12000 Btu/h = 200 Btu/min = 3025.9 k Calories/h = 12661 kJ/h = 3.517 KW

(E) Evaporation loss: 0.00085 x 1.08 x Flow rate (M3/HR) x Range [M3/Hr]

(G) Cycles of concentration: The term used in calculating and determining the amount of bleed is called cycles of concentration. Cycles can be defined as the number of times the dissolved minerals in the system cooling water are concentrated versus the level in the raw makeup water.

(H) Blow down losses: Evaporation losses / (COC-1)

(I) Liquid/Gas ratio: Liquid/Gas (L/G)ratio, of a cooling tower is the ratio between the water and the air mass flow rates.

1.11.Efficient System Operation

(A) Cooling Water Treatment:-Cooling water treatment is mandatory for any cooling tower whether with splash fill or with film type fill for controlling suspended solids, algae growth, etc.With increasing costs of water, efforts to increase Cycles of Concentration (COC), by Cooling Water Treatment would help to reduce make up water requirements significantly. In large industries, power plants, COC improvement is often considered as a key area for water conservation.

(B) Drift Loss in the Cooling Towers:- It is very difficult to ignore drift problem in cooling towers. Now-a-days most of the end user specification calls for 0.02% drift loss.With technological development and processing of PVC, manufacturers have brought large change in the drift eliminator shapes and the possibility of making efficient designs of drift eliminators that enable end user to specify the drift loss requirement to as low as 0.003 – 0.001%.

(C) Cooling Tower Fans:- The purpose of a cooling tower fan is to move a specified quantity of air through the system, overcoming the system resistance which is defined as the pressure loss. The product of air flow and the pressure loss is air power developed/work done by the fan; this may be also termed as fan output and input kW depends on fan efficiency. The fan efficiency in turn is greatly dependent on the profile of the blade. An aerodynamic profile with optimum twist, taper and higher coefficient of lift to coefficient of drop ratio can provide the fan total efficiency as high as 85–92 %. However, this efficiency is drastically affected by the factors such as tip clearance, obstacles to airflow and inlet shape, etc.

1.12.Cooling Tower Performance

The important parameters, from the point of determining the performance of cooling towers, are:

(1)."Range" is the difference between the cooling tower water inlet and outlet

temperature (See Figure)

(2)"Approach" is the difference between the cooling tower outlet cold water temperature and ambient wet bulb temperature. Although, both range and approach should be monitored, the 'Approach' is a better indicator of cooling tower performance. (see Figure).

(3)"Approach" is the difference between the cooling tower outlet cold water temperature and ambient wet bulb temperature. Although, both range and approach should be monitored, the 'Approach' is a better indicator of cooling tower performance. (see Figure).

(4)Cooling capacity is the heat rejected in kCal/hr or TR, given as product of mass flow rate of water, specific heat and temperature difference

(5)Cycles of concentration (C.O.C) is the ratio of dissolved solids in circulating water to the dissolved solids in make up water.

(6)Blow down losses depend upon cycles of concentration and the evaporation losses and is given by relation: Blow Down = Evaporation Loss / (C.O.C. – 1)

(7)Liquid/Gas (L/G) ratio, of a cooling tower is the ratio between the water and the air mass flow rates. Against design values, seasonal variations require adjustment and tuning of water and air flow rates to get the best cooling tower effectiveness through measures like water box loading changes, blade angle adjustments.

->Thermodynamics also dictate that the heat removed from the water must be equal to the heat absorbed by the surrounding air:

where: L/G = liquid to gas mass flow ratio (kg/kg)

T1 = hot water temperature (°C)

T2 = cold water temperature (°C)

h2 = enthalpy of air-water vapor mixture at exhaust wet-bulb temperature (same units as above)

h1 = enthalpy of air-water vapor mixture at inlet wet-bulb temperature (same units as above)

1.13.TOWER PROBLEMS

(A)Scale Deposit

As a water's dissolved solids level increases, corrosion and deposition tendencies increase. Because corrosion is an electrochemical reaction, higher conductivity due to higher dissolved solids increases the corrosion rate (see Chapter 24 for further discussion). It becomes progressively more difficult and expensive to inhibit corrosion as the specific conductance approaches and exceeds 10,000 µmho.

Some salts have inverse temperature solubility; i.e., they are less soluble at higher temperature and thus tend to form deposits on hot exchanger tubes. Many salts also are less soluble at higher pH. As cooling tower water is concentrated and pH increases, the tendency to pre-cipitate scale-forming salts increases.

Because it is one of the least soluble salts, calcium carbonate is a common scale former in open recirculating cooling systems. Calcium and magnesium silicate, calcium sulfate, and other types of scale can also occur. In the absence treatment there is a wide range in therelative solubility of calcium carbonate and gypsum, the form of calcium sulfate normally found in cooling systems.

Calcium carbonate scaling can be predicted qualitatively by the Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI). The indices are determined as follows:

Langelier Saturation Index = pHa - pHs

Ryznar Stability Index = 2(pHs) - pHa

The value pHs (pH of saturation) is a function of total solids, temperature, calcium, and alkalinity. pHa is the actual pH of the water.

With or without chemical treatment of the cooling water, cycles of concentration are eventually limited by an inability to prevent scale formation.

=>DEPOSITION CONTROL

As noted earlier, there are many contaminants in cooling water that contribute to deposit problems. Three major types of deposition are discussed here: scaling, general fouling, and biological fouling.

=>Scale Formation

Scale formation in a cooling system can be controlled by:

->minimizing cycles of concentration through blowdown control

->adding acid to prevent deposition of pH-sensitive species

->softening the water to reduce calcium using scale inhibitors to allow operation under supersaturated conditions

(B) Fouling due to presence of silt, dirt, sand etc.

(C) Microbiological growth due to presence of microrganisms ,Algae, fungi

(D) Corrosion of steel parts

1.14.Loss of Water

=>Evaporation Rate is the fraction of the circulating water that is evaporated in the cooling process.

->A typical design evaporation rate is about 1% for every 12.5C range at typical design conditions.

->It will vary with the season, since in colder weather there is more sensible heat transfer from the water to the air, and therefore less evaporation.

->The evaporation rate has a direct impact on the cooling tower makeup water

requirements.

=>Drift is water that is carried away from the tower in the form of droplets with the air discharged from the tower.

->Most towers are equipped with drift eliminators to minimize the amount of drift to a small fraction of a percent of the water circulation rate.

->Drift has a direct impact on the cooling tower makeup water requirements.

=>Recirculation is warm, moist air discharged from the tower that mixes with the incoming air and re-enters the tower.

->This increases the wet bulb temperature of the entering air and reduces the cooling capability of the tower.

->During cold weather operation, recirculation may also lead to icing of the air intake areas.

1.15.SOME PROBLEMS & IT’S REMEDY FOR COOLING TOWERS

Drift/carry-over ofwater outside theunit

(1) Uneven operation of spray nozzles(2) Blockage of the fills(3) Defective or displaced droplet eliminators(4) Excessive circulating water flow may be due to too high pumpinghead

(1)Adjust & clean the nozzle(2) Eliminate any dirt on the top of the fill or with suitable chemical pretreatment(3) Replace or realign the eliminators(4) Adjust the water flow-rate by means of the regulating valves. Check damage tothe fill

Lack of cooling andhence increase intemperatures owingto increasedtemperature range

(1) Water flow below the design value(2) Irregular airflow or lack of air(3) Recycling of humid discharge air(4) Intake of hot air from other sources(5) Blocked spray nozzles (or even blocked water pipes)(6) Scaling of joints(7) Scaling of the fill pack

(1) Regulated the flow by means of the valves(2) Ensure adequate clearance around cooling towers(3) Check the air descent velocity(4) Install deflectors(5) Clean the nozzles and/or the Tubes(6) Wash or replace the item(7) Clean or replace the material (washing with inhibited aqueous sulphuric acid is possible but long, complex and expensive)

1.16. Safety

(1) Chlorine Leakage Safety

(2) During Chemical Mixing Must Be Wear Gloves, Ear Clips, Goggles ect.

(3) If the volume of decomposing debris exceeds the chemical dosage’s ability to provide control ,the cooling tower will silently grow dangerous even while chemical dosing continues.

(4) Keep the cooling tower free of debris and deploy a good water treatment program and your cooling tower will operate safely and efficiently.

=>Personal Safety 

No matter what procedures are adopted in maintaining cooling towers, personal safety

precautions must be integral to the maintenance procedures. Best practices require workers to wear respirators, gloves and protective clothing to help prevent exposure to bacteria, especially Legionella.

cooling water doesn’t have to look dirty to be dangerous – just because the water is clear doesn’t mean it’s clean or free of bacteria – Every cooling tower can harbor bacteria. Always, always take precautions because unless the water is routinely tested for Legionella and other bacteria, the bacteria will never announce its presence until it’s too late.

Conclusion:

Components Current Condition Required Condition1.5.1.Fill Media Splash Fill Type, V-Bar Fill Media Is

Use.According To Its Structure Less Droplets Form Is Generates.So That Less Heat Transfer Is Occurring.Hence Efficiency Decrease.

Film Fill Type,Honey Comb Fill Media Use. According To Its More Layer Structure More Droplets Form Is Generates.So That Less Heat Transfer Is Occurring.Hence Efficiency Decrease.(See Product Images)

1.5.2.Drift Eliminator Blande Type,Wood Material Use To Cellular Type,PVC Material

Catch Water Droplets.->Less Lifetime(20 Years).

Use.PVC Material Is More Efficient Than Wood.->Long Life.

1.5.3.Sprinklers Same As Use Same As Use But More Efficient Product Is Use Now A Day.(See Product Images)

1.5.4.Nozzles Round Type Pattern Nozzle Use Square Type Variable Nozzles Use To Increase Tower Efficiency(See The 1.5.4. Paragraph)

1.5.5.Louvers Asbestos Concrete Sheet Use.->More Cost.->Less Lifetime

Anti-Splash Louvers Use.->Less Cost.->More Liferime.

1.5.6.Vibration Isolators

No Use In Process. We Should Use VI To Reduce Vibration Occurs In Cooling Tower.

1.5.7.Motors Same As Use. More Efficient Product (Show In Image 1.5.7.)

1.5.8.Fans Propellers Type Fans Use. FPR Cooling Tower Fans Should Use To Increase Efficiency.->More Desirable Aerodynamic Profile Over Full Blade.->Variable Axial Flow Cooling Tower Fans.

Mixing Tank Not Use In Process.Manually Mixing.

Must Be Done Systematically Step By Step To Reduce Lumps Formation Occurs By Solid Chemical.

Cold Storage Tank Concreate Cement Tank Use.->Less Life Time.->Corrosive In Some Chemials.->More Costly.

Fiber Glass Tank Use.->More Life Time.->Non Corrosive.->Less Costly.