cooling water (cw) system

COOLING WATER SYSTEM

Prepared by: Mohammad Shoeb SiddiquiSenior Shift SupervisorSaba Power Plant

INTRODUCTIONCooling water is the water removing heat from a machine or system. Cooling water may be recycled through a re-circulating system or used in a single pass once-through cooling (OTC) system. Recirculating systems may be open if they rely upon cooling towers or cooling ponds to remove heat or closed if heat removal is accomplished with negligible evaporative loss of cooling water.

Prepared by: Mohammad Shoeb Siddiqui

http://en.wikipedia.org/wiki/Cooling_tower

http://en.wikipedia.org/wiki/Cooling_pond

IntroductionIndustrial cooling towers may use river water, coastal

water (seawater), or well water as their source of fresh cooling water. The large mechanical induced-draft or forced-draft cooling towers in industrial plants continuously circulate cooling water through heat exchangers and other equipment where the water absorbs heat. That heat is then rejected to the atmosphere by the partial evaporation of the water in cooling towers where upflowing air is contacted with the circulating downflow of water. The loss of evaporated water into the air exhausted to the atmosphere is replaced by "make-up" fresh river water or fresh cooling water. Since the evaporation of pure water is replaced by make-up water containing carbonates and other dissolved salts, a portion of the circulating water is also continuously discarded as "blowdown" water to prevent the excessive build-up of salts in the circulating water.


http://en.wikipedia.org/wiki/Seawater

Circulating Water System

Cooling Tower

Condenser

CW Pumps

CTFFrom Bore Wells

CT Makeup

Ambient ConditionTemp. 27.5 oC Humidity 88.5 %

CW I/L Temp. 30 oC

CW O/L Temp. 45 oC

Air flow

Air flow

Raw & Fire Water Tank Capacity 2155 m3

CCW Heat Exchanger


Background

Condenser:The condenser is the most important component of the turbine cycle that affects the turbine heat rate. The function of the condenser is to condense exhaust steam from the steam turbine by rejecting the heat of evaporation to the cooling water passing through the condenser. Generally, twin shell- double pass- surface type condensers are employed for higher capacity units

Condenser

Cooled Water

Cooling Tower

AirAir

Make-up Water

Hot Water


COOLING TOWER


TYPES OF COOLING TOWERDifferent types of cooling towers are used in the power plants depending upon the location, size, infrastructure and water resources etc. Close cycle – wet cooling systems:

-Induced draft- Forced draft

- Natural draft cooling towers


Natural draft Large concrete chimneys generally used for water flow rates above 45,000

m3/hr utility power stations

Mechanical draft Lrge fans to force or suck air through circulated

water. The water falls downward over fill surfaces, which

help increase the contact time between the water and the air maximising heat transfer between the two.

Cooling rates of Mechanical draft towers depend upon their fan diameter and speed of operation

TYPES OF COOLING TOWER


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



Natural Draft Cooling Towers TYPES OF COOLING TOWER


Counter flow

• Air drawn up through falling water

• Fill located inside tower

Cross flow

• Air drawn across falling water

• Fill located outside tower

Natural Draft Cooling Towers TYPES OF COOLING TOWER


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. 4-cell tower



Three types• Forced draft• Induced draft cross flow• Induced draft counter flow

Mechanical Draft Cooling Towers



Induced Draft Cooling Towers• Two types

• Cross flow• Counter flow

• Advantage: less recirculation than forced draft towers

• Disadvantage: fans and motor drive mechanism require weather-proofinh



• Hot water enters at the top• Air enters at bottom and exits at top• Uses forced and induced draft fans

Induced Draft Counter Flow CT TYPES OF COOLING TOWER


Induced Draft Cross Flow CT• Water enters top and passes over fill• Air enters on one side or opposite sides• Induced draft fan draws air across fill



• Air blown through tower by centrifugal fan at air inlet

• Advantages: suited for high air resistance & fans are relatively quiet

• Disadvantages: recirculation due to high air-entry and low air-exit velocities

Forced Draft Cooling Towers TYPES OF COOLING TOWER


Components of Cooling Tower Frame and casing Fill Cold water basin Drift eliminators Air inlet Louvers Nozzles Fans Pumps Chemical Dosing System


Components of Cooling Tower

• Frame and casing: support exterior enclosures

• Fill: facilitate heat transfer by maximizing water / air contact• Splash fill• Film fill

• Cold water basin: receives water at bottom of tower



• Drift eliminators: capture droplets in air stream• Air inlet: entry point of air• Louvers: equalize air flow into the fill and retain

water within tower• Nozzles: spray water to wet the fill• Fans: deliver air flow in the tower• Pumps: deliver the water flow in the tower


Tower Materials Wooden components included the frame, casing,

louvers, fill, and often the cold water basin Galvanized steel, various grades of stainless steel,

glass fiber, and concrete enhance corrosion resistance, reduce maintenance, and promote reliability

and long service life Plastics are widely used for fill, including PVC,

polypropylene, and other polymers. Plastics also find wide use as nozzle materials

Aluminum, glass fiber, and hot-dipped galvanized steel are commonly used fan materials.

Centrifugal fans are often fabricated from galvanized steel. Propeller fans are fabricated from galvanized, aluminum, or molded glass fiber reinforced plastic



Fill Media Effects 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.



Assessment of Cooling TowersMeasured Parameters

• Wet bulb temperature of air• Dry bulb temperature of air• Cooling tower inlet water temperature• Cooling tower outlet water temperature• Exhaust air temperature• Electrical readings of pump and fan

motors• Water flow rate• Air flow rate


Performance Parameters

1. Range2. Approach3. Effectiveness4. Cooling capacity5. Evaporation loss6. Cycles of concentration7. Blow down losses8. Liquid / Gas ratio

Assessment of Cooling Towers


FACTORS AFFECTING COOLING TOWER PERFORMANCE

Capacity

Heat dissipation (in kCal/hour) and circulated flow rate (m3/hr) are not sufficient to understand cooling tower performance.

For example, a cooling tower sized to cool 4540 m3/hr through a 13.9oC range might be larger than a cooling tower to cool 4540 m3/hr through 19.5oC range.


Efficient System Operation Cooling Water Treatment Drift Loss in the Cooling Towers

drift loss requirement to as low as 0.003 – 0.001%

Cooling Tower Fans Flow Control Strategies


1. Range Difference between

cooling water inlet and outlet temperature:

Range (°C) = CW inlet temp – CW outlet temp

High range = good performance

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Hot Water Temperature (In)

Cold Water Temperature (Out)

Wet Bulb Temperature (Ambient)

(In) to the Tower(Out) from the Tower



Cold Water Temperature 32.2oC – Wet Bulb Temperature (26.7oC) = Approach (5.5oC)

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Difference between cooling tower outlet cold water temperature and ambient wet bulb temperature:

Approach (°C) = CW outlet temp – Wet bulb temp

Low approach = good performance

2. ApproachAssessment of Cooling Towers


3. Effectiveness

Effectiveness in %

= Range / (Range + Approach)

= 100 x (CW temp – CW out temp) / (CW in temp – Wet bulb temp)

High effectiveness = good performance

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4. Cooling Capacity

Heat rejected in kCal/hr or tons of refrigeration (TR)

= mass flow rate of water X specific heat X temperature difference

High cooling capacity = good performance

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5. Evaporation LossWater quantity (m3/hr) evaporated for cooling duty

= theoretically, 1.8 m3 for every 10,000,000 kCal heat rejected

= 0.00085 x 1.8 x circulation rate (m3/hr) x (T1-T2)

T1-T2 = Temp. difference between inlet and outlet water

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6. Cycles of concentration (C.O.C.)

Ratio of dissolved solids in circulating water to the dissolved solids in make up water

Depend on cycles of concentration and the evaporation losses

Blow Down = Evaporation Loss / (C.O.C. – 1)

7. Cycles of concentration (C.O.C.)



8. Liquid Gas (L/G) RatioRatio between water and air mass flow rates

Heat removed from the water must be equal to the heat absorbed by the surrounding air

L(T1 – T2) = G(h2 – h1)L/G = (h2 – h1) / (T1 – T2)

T1 = hot water temp (oC)T2 = cold water temp (oC)Enthalpy of air water vapor mixture at inlet wet bulb temp (h1) and outlet wet bulb temp (h2)



Energy Efficiency Opportunities

1. Selecting a cooling tower2. Fills3. Pumps and water distribution4. Fans and motors


Heat Load

The heat load imposed on a cooling tower is determined by the process being served

In most cases, a low operating temperature is desirable to increase process efficiency or to improve the quality or quantity of the product. In some applications (e.g. internal combustion engines), however, high operating temperatures are desirable

The size and cost of the cooling tower is proportional to the heat load


Wet Bulb Temperature

Minimum cold water temperature to which water can be cooled by the evaporative method

Thus, the wet bulb temperature of the air entering the cooling tower determines operating temperature levels throughout the plant, process, or system.

Theoretically, a cooling tower will cool water to the entering wet bulb temperature, when operating without a heat load. However, a thermal potential is required to reject heat, so it is not possible to cool water to the entering air wet bulb temperature, when a heat load is applied

The temperature selected is generally close to the average maximum wet bulb for the summer months whether it is specified as ambient or inlet


Range, Flow and Heat Load

Range is a direct function of the quantity of water circulated and the heat load. Increasing the range as a result of added heat load does require an increase in the tower size. If the cold water temperature is not changed and the range is increased with higher hot water temperature, the driving force between the wet bulb temperature of the air entering the tower and the hot water temperature is increased, the higher level heat is economical to dissipate.

If the hot water temperature is left constant and the range is increased by specifying a lower cold water temperature, the tower size would have to be increased considerably. Not only would the range be increased, but the lower cold water temperature would lower the approach. The resulting change in both range and approach would require a much larger cooling tower.


Saba Power Plant Data


SABA POWER PLANT DESIGN DATA1 x 4 cell cooling tower

Design data: GEAType: Counter flow.Number of cells: 4Cell Size (ft x ft) 60 x 60.Overall Length/ Width (ft x ft) 240 x 60.Distribution type: Up spray.Snow Load: 0Design wind velocity: 100 mph.


SABA POWER PLANT DESIGN DATA

Cooling Tower Performance Data:

Water circulation: 58,558 gpm(13300 m³/hour)

Inlet water circulation temperature: 91.4ºF (33ºC)

Outlet Water Temperature: 71.42ºF (22ºC)Design wet bulb temperature 62.96ºF

(17.2ºC)Prepared by: Mohammad Shoeb Siddiqui

SABA POWER PLANT DESIGN DATA2 x 100% duty mixed flow centrifugal pumps.

Capacity: 60,000 gpm.

2 x 1000 HP motors use to drive the circulating water pumpsSpeed: 500 RPM.Voltage: 6.6Kv.

4 x cooling tower with induce draft fans.

Speed: 98.3 RPM.Number of blades: 6 per fan.

4 x cooling tower fan motors.Speed: 1500 RPM.Rated capacity: 200 HP.Rated Voltage: 415 Volts.

4 x Amarillo gearboxes.

Reduction ratio: 15:1Prepared by: Mohammad Shoeb Siddiqui

SABA POWER PLANT DESIGN DATA1 x Condenser

Design Data: Made EcolaireSteam load: 588,694 LB/HRSteam Temperature: 100.61oFHeat rejected to circulating water: 555.5161 million BTU/HR.Effective Tube length: 9398 mmEffective Condenser surface: 62,462 Sq.Ft.Circulating water flow: 55,256 gpmCirculating water inlet temperature: 21.6oCCleanliness factor: 90%Average Circulating water velocity in tubes: 7.2 FT/SECAbsolute Pressure: 50 mm HgA

Circulating water friction loss through clean tubes and water box: 16.22 Ft. of water.

Number of tubes: 7777Tubes material: SS-A249 TP 304L, 22BWGTubes outer diameter: 25 mm


SABA POWER PLANT DESIGN DATABently Nevada vibration monitoring system (3300 series).

The main components of the cooling tower dosing system are:

1 x Acid storage tank . Capacity 16.5 cubic meters 2 x Acid dosing pumps, Neptune. Capacity 125 lph, 7 kg/cm2

Motor capacity 1 KW 1 x Anti-scalant dosing tank, Capacity 190 liters 2 x Anti-scalant dosing pumps, Neptune. Capacity 5 lph, 50

kg/cm2 Motor 1 KW


SABA POWER PLANT DESIGN DATA 2 x Chlorination booster pumps, Jonson MarchCapacity 43.14 m3/h, 28 mlcMotor 5.6 KW, 1,440 rpm 1 x Chlorine evaporatorCapacity 2,727 Kg/day 1 x ChlorinatorCapacity 2,727 Kg/day2 x Ton chlorine cylinder containers for liquid chlorine 1 x Weigh scale for the chlorine cylinder containercapacity 0 to 1,800 Kg.


Working PrincipleDuring normal operation, one circulating water pump

is in service supplying approximately 60,000 gallons of water at a temperature of 30ºC and a pressure of 1.4 kg/cm² to the Main condenser and the closed cooling water plate heat exchangers.

The circulated water makes two passes in the condenser. Water enters the condenser waterbox inlet and flows through the tubes into the return waterbox, and then through the second set of tubes and into the outlet waterbox.

As the circulating water flows through the tubes, the exhaust steam thermal energy is transferred to the circulating water. Rapid condensation of the steam occurs and a vacuum is created in the condenser.


Working PrincipleThe heated water returns to the top of the cooling

tower via four pipe risers and into a horizontal distribution header pipe. From there, it branches into a system of lateral distribution pipes, where the nozzles spray the water downward in a predetermined pattern over the heat exchange medium, or fill.

Before the air flow is permitted to exit through the top of the tower, it must pass through the drift eliminators. The shape of this material causes the air to change directions and thus provides impact surfaces which prevent water droplets from being carried out of the tower with the air flow.

The cold water basin of the cooling tower catches the falling water, which then flows back to the circulation pumps.Prepared by: Mohammad Shoeb Siddiqui

Working PrincipleAs this process takes place, a small percentage of water is

loss due to evaporation. Ambient temperature and Relative Humidity also affect the rate of evaporation. The cool water is then recirculated to the users.

When the water evaporates in the cooling tower operations, most of the dissolve solids remain behind in a non-evaporative state. If the ratio of these concentrations become excessively high, scale and deposits will form in the Main condenser tubes and other piping. This will drastically affect the efficiency of the condenser, which will in turn cause a high back pressure for the steam turbine.

To reduce the amount of total dissolve solids (TDS) in the system, blowdown is required. The operating (TDS) range is blow (3500 PPM). Cooling tower make up is therefore necessary to replace the water loss caused by evaporation, blowndown, windage and carryover.Prepared by: Mohammad Shoeb Siddiqui

Working Principle

WATER TREATMENTCooling tower maintenance can be very high unless the water is treated to prevent corrosion, biological growth, and deposits. Water treatment also protects the cooling tower wood from chemical attack.


Working PrincipleWATER TREATMENT

Due to the evaporation that takes place in the cooling tower, the dissolved solids in the water become concentrated. The evaporated water must be replaced by make up water. The circulating water becomes more concentrated than the make up water due to this evaporation loss. The cycle of concentration is the term applied to indicate the degree of concentration of the circulating water with the make up water. Some water of the cooling tower is also lost due to wind or drift loss, this is the loss of fine droplets of water that are carried away by the circulating air. In mechanical draft towers, 0.1 % to 0.3 % wind losses are possible. The water treatment process plays a vital role in the cooling tower operation. Prepared by: Mohammad Shoeb Siddiqui

Working PrincipleWATER TREATMENT

Calcium bicarbonate which is normally present in raw water, breaks down to form relatively insoluble calcium carbonate. Calcium carbonate scale is the most common type of water formed deposits in a cooling system. The Langlier Index measures the tendency of CaCO3 to precipitate under given conditions of calcium hardness, alkalinity, pH, temperature and total dissolved solids. A positive index means that water will tend to deposit scale while a negative index tends to dissolve scale.Prepared by: Mohammad Shoeb Siddiqui

WATER TREATMENTThe Saba Power Plant cooling water system

has three (3) dosing systems. Sulfuric acid dosing Anti-scalant dosing Chlorination injection

Working Principle


WATER TREATMENTSulfuric Acid Dosing System Chemical treatment with sulfuric acid

keeps the scale forming salts of calcium and magnesium in solution by lowering the pH of the circulating system. At Saba, the pH is controlled between 7.8 to 8.5.

Working Principle


Anti-scalant Dosing System

Chemical inhibitors are needed to check corrosion. Surface active chemicals or chelating agents such as sodium hexameta phosphate prevent crystal growth & therefore scale formation. In effect, they increase the solubility range of scale forming salts. Controlled scale treatment adjusts the composition of water so that a thin impervious layer of calcium carbonate scale deposits on the surface of the circulating water system. The scale must be thick enough to prevent any corrosion, but thin enough not to effect the overall heat transfer.For the Anti-scalant dosing system, there is one dosing tank of 220 litters capacity with two dosing pumps.

Working Principle


Chlorination System Microbiological growth, slimes &

algae, retard cooling, cut cooling efficiency and increases the maintenance cost of the cooling system. When growth breaks loose, it will clog pipelines, pumps & equipment. Mechanical cleaning is the best way to get rid of accumulated growths. But to keep slime & algae from getting a toehold in the first place, chlorine gas is used.

Working Principle


Saba Power Plant

Precautions, Limitations and Setpoints


Precautions, Limitations and SetpointsBefore starting any circulating water pump (CW-PP-

1/2), verify that all four (4) riser isolation valves to the distribution header at the cooling tower, are fully opened.

The circulating water pumps (CW-PP-1-2) motors are limited to the number of starts, depending on the existing conditions. This limitation is designed to protect the stator and rotor from excessive heat that is generated from the high inrush current when a motor is started. If the motor is in a cold condition (standby), three (3) consecutive starts are allowed. If the motor was running and achieved normal operating temperature, the motor will be limited to two (2) consecutive starts. If the number of starts is exceeded, the IQ-1000 which is the supervisory instrumentation located on the respective motor breakers will “lockout” the motor to inhibit a restart. The number of starts should not average more than six (6) starts per day.



The circulating water pumps (CW-PP-1-2) are equipped with temperature sensing devices (TE-1028A-J for CW-PP-1 and TE-1031A-J for CW-PP-2) that continuously monitor the motor bearing and winding temperatures. If any winding temperatures exceeds 170°C an alarm will annunciate on the DCS (TAH-1028A-F for CW-PP-1 and TAH-1031A-F for CW-PP-2) and if the winding temperature exceeds 180°C the respective motor will trip and an alarm will annunciate on the DCS (TAHH-1028A-F for CW-PP-1 and TAHH-1031A-F for CW-PP-2).If any motor bearing temperature exceeds 90°C, an alarm will annunciate on the DCS (TAH-1028G-J for CW-PP-1 and TAH-1031G-J for CW-PP-2) and if bearing temperature exceeds 95°C the respective motor will trip and an alarm will annunciate on the DCS (TAHH-1028G-J for CW-PP-1 and TAHH-1031G-J for CW-PP-2).Prepared by: Mohammad Shoeb Siddiqui


A circulating water pump (CW-PP-1-2) will be prohibited from starting if the discharge motor operated valve (MOV-2007, MOV-2009) is open. This requirement is to prevents the motor from overloading and also prevent the system from a sudden shock, which will result if the system is rapidly pressurized.

During normal operation, one circulating pump (CW-PP-1 or 2) will be in service and one will be in the standby mode. The discharge MOV-2007 and 2009 controllers must be in the AUTO mode. If AUTO mode is not selected when the pump is running, an alarm will annunciate on the DCS (PUMP IS RUNNING and VALVE IS NOT IN AUTO). The standby pump must be in the AUTO mode in the event that the running pump fails and the standby pump will start automatically.



A low level in the cooling tower basin will annunciate on the DCS (LAL-1036) to warn the control room Operator. The Low level alarm is set at –700 mm. Note that this alarm gets its signal from the cooling tower basin level transmitter.A low low level in the cooling tower basin will trip the pump that is in service and annunciate on the DCS (LALL-1004). The level switch (LSLL-1041) is set at –800 mm.A low press switch, (PSL-1005) is located on the circulating water header, if this switch detects a low pressure <1 kg/cm²>, the standby pump will start and an alarm will annunciate on the DCS (PAL-1005).



All four (4) cooling tower fan gearboxes (CT-FN-1-4) are provided with vibration monitoring instrumentation (VE-1050A-D), that will generate an alarm on the DCS (VAH or VAHH-1050A-D) if the respective vibration supervisory circuit detects a Hi or Hi Hi vibration on the fan gearbox. The Hi and Hi Hi vibration alarm is set at 0.075 in/sec. and 0.1 in/sec. respectively.

All four (4) of the cooling tower fan gearboxes are provided with temperature measuring devices that will generate an alarm on the DCS (TAH-1051A-D) if the temperature exceeds 100ºC and if temperature exceeds 111ºC, the fan will trip.



Sulifuric Acid Sulfuric acid mist begins to irritate the eyes, nose and

throat at 0.5 mg/m3; the threshold limit value of 1 mg/m3 may corrode teeth, with frequent exposure. Sulfuric acid is more irritating in a high humidity environment. Liquid sulfuric acid will burn skin and eyes and it will deeply burn the stomach and throat if swallowed. Sulfuric acid is non-flammable but reacts violently with water and organic materials. Poisonous gas may be produced in a fire. Flammable hydrogen gas may be produced at acid facilities. Fire fighters should wear protective equipment when exposed to such conditions.

Low Low level switches are provided in the sulfuric acid

and Anti- scalant dosing tanks, these switches will trip the pump and will annunciate on the DCS, when actuated.


Chlorine Chlorine is known as a potential danger to worker health. Chlorine causes irritation of the eyes, nose, throat and lungs. Exposure to a sufficiently high concentration of chlorine will be fatal. Chlorine gas exhibits a sharp pungent odor. Therefore, its presence is readily detected and it is unlikely that anyone could remain in a contaminated area. Fortunately, chlorine gas does not produce a cumulative physiological effect and complete recovery will occur following mild exposure.



The physiological effects of chlorine are; detectable odor at 3.5 ppm, throat irritation at 15.1 ppm, coughing at 30.2 ppm and extreme danger in 30-60 minutes at 40-60 ppm. The characteristic penetrating odor of chlorine gas gives warning of its presence in the air. Its greenish yellow color makes it visible when high concentrations are present. The handling and use of both liquid and gaseous chlorine require close attention to safety precautions and practices.



○ Gas masks for chlorine protection are available at;

○ The closed cooling water pump area/green box

○ The air heater washing basin /green box○ The firewater foam tank /green box○ The raw water building, north wall/green

box○ The main control room, SCBA is also

available in the control room



(If a chlorine ton/cylinder container develops a leak, its contents are disposed of by placing it in position for gas withdrawal and bubbling the gas into the neutralization bath as describe below.)

1.4 pounds of Caustic Soda (NaOH) is required for

neutralization of one pound of Chlorine. 3.7 pounds of Soda Ash (Na2CO3) is required for

neutralization of one pounds of Chlorine. 1.3 pond of Hydrated Lime [Ca(OH)2] is required for

neutralization of one pounds of ch



There are two (2) chlorine leak detectors installed at the chlorination control room building, one inside the chlorination room and the other at the ton/cylinder container skid area. These leak detectors will give a Chlorine leak alarm at the DCS and start the strobe/horn at the Chlorination control room building.

Two windsocks are provided in the plant to establish the wind direction in case of a chlorine gas leak. Personnel should check the direction of these windsocks before rushing to fix the leak.

NoteDon’t rush in the opposite direction of the

wind



ChlorineThe Control Panel: The control panel contains all the equipment

required to operate the chlorination sequence. A programmable timer can be programmed to control the chlorination process automatically.

The System Control Panel Alarm Lights are as

follows; Chlorine evaporator low water level Chlorine evaporator water temperature high Evaporator water temperature low Liquid chlorine manifold pressure low (2.8 Kg/cm2)



Chlorine

Expansion chamber pressurized (2.8 Kg/cm2) Evaporator discharge pressure relief valve (2.8

Kg/cm2) Evaporator discharge pressure high (17.6 Kg/cm2) Evaporator discharge gas temperature low Filter exit low pressure (4.2 Kg/cm2) Ejector pressure supply low Booster pumps discharge pressure low (3.9 Kg/cm2) Booster pumps suction pressure low (1.05 Kg/cm2) Chlorinator vacuum low Chlorinator vacuum high



The purpose of starting this system is to provide cooling water to the following users.

1. Main condenser.2. Plate heat exchangers.3. Chlorination booster pumps. The following support systems should be aligned

so that they may be placed in service when required.

Acid injection system Anti scalant injection systemChlorination systemWater Well pumps and raw water system

Startup


Startup

The normal operating level is (-325 mm). If filling of the basin is required, verify on the DCS that the raw water tank level is at normal operating level of 12 meters as indicated on (LT-1505) and the water well pumps are in auto. Place the level control valve (MOV-1521) in <Manual> and commence filling the basin by giving the controller a 25% output, this will allow water to flow by gravity from the raw water tank to the cooling tower basin.

NoteThe water well pumps will only start when the raw water

tank level drops to 3.5 meters. Verify that the Low and Low Low level (LAL-1036 and

LALL-1040) alarms are cleared, “normal” status, as indicated on the DCS alarm summary and also have the field operator verify the actual level.


Startup

Once the normal operating level of the cooling tower basin is established, verify that all the permissive are satisfied, Proceed to start the CW pump .

The field operator should verify that the circulating water pump discharge motor operated valve (MOV-1007 or 1009) opens to approximately 25%. When the system is pressurized > 1 Kg/cm², the discharge MOV should continue to open, when the valve is fully open the valve indication on the DCS will change color from green to red. If the valve fails to open , the valve is provided with a hand wheel that can be used to open the valve. In order to open the valve locally through the motor, the field operator will have to switch from REMOTE to LOCAL control.

The field operator must check the pump and motor for abnormal noise and vibration. If any abnormal noise or vibration is detected, immediately shutdown the pump and inform the Shift Supervisor. Prepared by: Mohammad Shoeb Siddiqui

Startup

The system should be vented once circulation is established. The high point vents (GW-GA-06, GW-GA-07 and GW-GA-08) are located on the Main condenser water box inlet, outlet and return respectively.

Align and place the plate heat exchangers in service as required.

Check the gearbox oil level before starting the cooling tower fans. Cooling tower fans will be started as required to control the circulating water temperature. Proceed to start the cooling tower fans

Start and maintain the circulating water chemistry as per the Plant Chemistry Manual.

Place the Blowdown system in service by opening (CW-GA-01) as required to control the Total Dissolve Solids (TDS) as per the Chemistry manual.


Chemical Dosing system Startup

Acid dosing system Align all the valves per procedure. Align all the electrical breakers as per procedure. Make sure that the acid storage tank level is not low. Start the Acid dosing pump A or B from DCS

Anti-scalant dosing system Align all the valves per procedure. Align all the electrical breakers as per procedure. Make sure that the acid storage tank level is not low. Start the Acid dosing pump A or B from DCS



Chlorination System Close the drain valves in the water piping system and

open all shutoff valves in the water supply line to the water supply piping system.

Fill the water chamber to the operating level, as confirmed by water being discharged to the drain through the open drain connection in the rear of the evaporator. Observe the sight glass to check the water level.

When the chamber is filled to the operating level, gradually close the throttling valve.

Apply 120 V. ac power to the control circuit connection box.

Observe the position of the indicating pointer of the cathodic protection ammeter; turn the adjustment screw of the potentiometer, if necessary, to bring the pointer just within the lower portion of the green band on the scale. If the reading in the green portion of the scale cannot be achieved, this is indicative that the conductivity of the water is too low to permit a sufficient flow of protection current. In such instances, it will be necessary to increase the conductivity by adding sodium sulfate or magnesium sulfate to the water via the standpipe provided for this purpose in the top of the water chamber.Prepared by: Mohammad Shoeb Siddiqui


Chlorination System Set the water temperature control to 155 oF, the high

temperature control to 170 oF and the low temperature control to 140 oF.

Energize the immersion heater by closing the circuit breaker in the power supply line to the heater. While the Evaporator is warming up, leak test all piping.

Inspect all joints in the liquid chemical supply and the gas discharge lines to ensure that the joints are tight.

Verify that the blow-off valve in the bypass line is closed. To test for leaks, open all in-line valves between the liquid

chemical supply valve and the gas dispenser, including the valve in the bypass line around the electrically operated pressure reducing and shut-off valve, to provide a path around the de-energized valve.



CAUTIONDo not open the header valve that is closest to the

chemical supply

WARNINGDamaging or breaking of the chemical piping, valves

or fittings can cause a major hazardous chemical spill. Never tighten or adjust any leaking fitting when the chemical supply cylinder valve is open.

WARNINGWhen system leaks occur, the procedures required to

find these leaks may cause exposure to hazardous chemicals at levels that exceed the Occupational Safety and Health Administration (OSHA) limits.


Cooling Towers

THANK YOUFOR YOU ATTENTION


cooling water (cw) system

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