O&M_Seimens_D.E

7/29/2019 O&M_Seimens_D.E.

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Cycle of Operation

C2M SCS 00 01_0 I - 1

Chapter 1

Cycle of Operation

Chapter Objectives This chapter describes the working cycle of the vapour absorptionchiller and the functions of its various components

What is Refrigeration ? Refrigeration is defined as the process of extracting heat from a lowtemperature medium and transferring it to a high temperature heatsink. Refrigeration maintains the temperature of the heat sourcebelow that of its surroundings while transferring the extracted heatto a heat sink.

Basic Principles The boiling point of water is directly proportional to pressure. Atatmospheric pressure water boils at 100C. At lower pressure itboils at lower temperature. At 6mmHg absolute pressure the boilingpoint of water is 3.7C.

To change water from liquid to vapour it has to be heated. The heatis absorbed by the water and its temperature starts rising. Howeverit rises until it reaches a point where the temperature stays constantand it starts boiling, ie. the liquid water vapourises. This point iscalled the boiling point. At this point all the heat being absorbed bythe water does not change its temperature but only its phase. Thisheat, required to change the phase of a liquid to vapour, is calledthe Latent of Vapoursation. Similarly the heat rejected by a vapourwhen it condenses is called the Latent Heat of Condensation.

Lithium Bromide (LiBr) is a chemical similar to common salt (NaCl).LiBr is soluble in water. The LiBr water solution has a property toabsorb water due to its chemical affinity. As the concentration ofLiBr solution increases, its affinity towards water increases. Also asthe temperature of LiBr solution decreases, its affinity to waterincreases.

Further there is a large difference between vapour pressure of LiBrand water. This means that if we heat the LiBr water solution, thewater will vapourise but the LiBr will stay in the solution and becomeconcentrated.

Absorption Cycle

overview

Absorption systems use heat energy to produce a refrigeratingeffect. In these systems the refrigerant, ie. water, absorbs heat at alow temperature and pressure during evaporation and releases heatat a high temperature and pressure during condensation.

A solution known as absorbent, ie. Lithium Bromide (LiBr),

is used to absorb the vapourised refrigerant (after its evaporation atlow pressure). This solution, containing the absorbed vapour isheated at a higher pressure. The refrigerant vapourises and thesolution is restored to its original concentration for recirculation.

In a double effect absorption machine, the latent heat ofcondensation of the refrigerant generated in the first stagegenerator, is used in a second stage generator to enhance theefficiency of the cycle

When the refrigerant undergoes a series of evaporation,absorption, pressurisation, vapourisation, condensation, throttling,and expansion processes, absorbing heat from a low temperatureheat source and releasing it to a high temperature sink, so that itsstate is restored to its original one, it is said to have completed a

refrigerating cycle.


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Cycle of Operation

I - 2

Schematic Diagram A schematic diagram of the absorption cycle is shown in the Fig. 1.1

Individual Parts The operation of the various parts of the absorption machine is describedbelow.

EvaporatorThe evaporator consists of a tube bundle, an outer shell, distribution

trays, and a refrigerant pan. The chilled water flows inside the tubes. Arefrigerant pump circulates the refrigerant from the refrigerant pan intothe distribution trays. From the trays the refrigerant falls on the

evaporator tubes. The shell pressure is very low (6mmHg). At thispressure the refrigerant evaporates at a low temperature (3.7C) andextracts latent heat of evaporation from the water being circulatedthrough the evaporator tubes. Thus the water being circulated throughthe tubes becomes chilled.

Absorber The absorber consists of a tube bundle, an outer shell (common with theevaporator), distribution trays, and an absorbent collection sump.Concentrated absorbent solution (63.4%) from the low temperature

generator is fed into distribution trays. This solution falls on the absorbertubes. Concentrated absorbent has an affinity to water and absorbs thevapourised refrigerant from the evaporator section. Hence the vacuum inthe shell is maintained at a low pressure and ensures the correct chilledwater temperature. The concentrated absorbent becomes diluted. Duringthis dilution the 'Heat of Dilution' is generated. This increases thetemperature of the absorbent solution. This heat is removed by thecooling water being circulated in the absorber tubes. As the absorbentsolution loses it's heat to the cooling water, it is able to absorb morerefrigerant vapour, and gets further diluted. The diluted absorbent

(58.5%) collects in the bottom of the shell.

Heat exchangers The diluted absorbent is pumped to the high temperature generator by

the absorbent pump. It first passes through the low temperature heatexchanger where it absorbs heat from the concentrated absorbent. Itnext flows through the heat reclaimer where it absorbs heat from thesteam condensate. Then the diluted absorbent flows through the hightemperature heat exchanger where it absorbs heat from the intermediateabsorbent solution. The solution then enters the high temperaturegenerator. The heat exchangers serve to heat up the cool absorbentsolution before it enters the high temperature generator for reheating.This reduces the heat input required in the high tremperature generator.This increases the efficiency of the cycle.

High Temperature

Generator

The high temperature generator (HTG) consists of a tube bundle, anouter shell and a set of eliminators. Steam is allowed to pass inside the

tubes. The diluted absorbent flows around these tubes and is heated.The temperature of the solution increases until it reaches it's boilingpoint. The absorbed refrigerant boils out of the solution. The solutionconcentration increases (to 61%). This increased concentration isreferred to as the intermediate concentration. The vaporised refrigerantgenerated passes through the eliminators and goes to the lowtemperature generator.

Low Temperature

Generator and

Condensor

The low temperature generator (LTG) and condensor tube bundles areenclosed in a shell and are separated by an insulation plate. Thevaporised refrigerant flows into the LTG tubes. It heats the intermediateabsorbent, flowing outside the tubes, and condenses. The condensedrefrigerant flows into the condenser. Refrigerant vapourised from the

intermediate absorbent passes through the eliminators to the condenser.Here it is cooled by cooling water being circulated inside the condensertubes. The refrigerant vapour condenses on the outside of the condensor


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C2MSCS0001_

0

I-3

A B

R E

D

R E

C

L O

LP

O

H

G

T

P

AllPressures

N O T


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C*M *** 02 00_0 II - 1

Chapter 2

Water Circuit Considerations

Chapter Objective This chapter describes the effects of changes in the hot / coolingand chilled water specifications and other issues, on theperformance and operation of the machine.

The lower the temperature

of hot / cooling water, the

better.

The temperature at which the refrigerant vapour in the condensercondenses, goes down in proportion to the reduction in thetemperature of hot / cooling water. Hence the temperaturedifferences available in the absorber and condenser increaseenabling the machine to deliver a higher than rated capacity. Asthe capacity increases for the same solution flow rate, the variousinefficiencies of the heat exchange reduce, thereby increasing theefficiency of operation.

Extremely low hot /

cooling water temperature

is not acceptable.

LiBr solution crystallizes when it is cooled. As the LiBr solutionconcentration decreases, the crystallization temperaturedecreases. At a concentration of 65% the crystallization

temperature is 42C, at a concentration of 60% the crystallizationtemperature is 17C and at a concentration of 55% thecrystallization temperature is 5C. The cooling water cools thediluted LiBr in the absorber, which cools the concentrated LiBr inthe low temperature heat exchanger (LTHE). If the concentratedLiBr is cooled so that it crystallizes in the LTHE, the LiBr stopsflowing through the LTHE, and the machine cannot operate. Hencethe temperature of cooling water is to be controlled to ensure thatthe LiBr does not crystallize.

Capacity of the machine

reduces when hot / cooling

water temperatureincreases

LiBr becomes hot when it absorbs vapourised refrigerant. As thetemperature of LiBr solution increases its the absorption powerdecreases. Hot / cooling water removes heat from the LiBr andensures maximum absorption of the refrigerant. If the hot / coolingwater temperature increases, so does the LiBr temperature. Hencethe absorption of refrigerant vapour is reduced and the pressure inthe evaporator increases. The rated chilled water temperaturecannot be maintained and steam is wasted. To prevent this, themaintenance of the hot / cooling water temperature is essential andhot / cooling water temperature should not be allowed to rise.

Interlock between chilled

and hot / cooling water

flows

If the chilled water flow to the machine stops for any reason, thehot / cooling water flow to the machine should also stop within oneminute. If the hot / cooling water flow to the machine continueswhen the chilled water flow is stopped, the absorbent solution in

the absorber continues to get cooled and creates a high vacuum inthe lower shell. The refrigerant temperature drops sharply and theevaporator tubes may ice as the chilled water becomes stagnant.

Ensure that the hot / cooling water pump stops by interlocking thechilled and hot / cooling water pump contactors so that the hot /cooling water pump stops if the chilled water pump is stopped.

In case the hot / cooling water pump is not dedicated to themachine and the hot / cooling water pump cannot be stopped whenthe chilled water pump stops, provide a butterfly valve in the hot /cooling water inlet line to the absorption machine. Hook up the hot/ cooling water stop signal from the control panel to the actuator of

the butterfly valve so as to close the valve when hot / cooling wateris not required.


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Chapter 2

II - 2 C*M *** 02 00_0

Water treatment of chilled

and hot / cooling water

The water treatment of chilled and hot / cooling water is importantfor the machine performance and long life.

If the water quality is bad and shows a scaling tendency, scaleadheres to the inside of the heat transfer tubes of the evaporator,absorber and condenser. The heat transfer between the chilledwater and the refrigerant, and the hot / cooling water and the LiBr

solution and the condensing refrigerant reduces. This causes anincrease in the LiBr and condensed refrigerant temperatures andincreases the steam consumption. The chilled and hot / coolingwater should be treated to prevent scaling inside the tubes.

If the chilled or hot / cooling water becomes corrosive, it willcorrode the inside of the evaporator, absorber and condensertubes. Tube failure due to corrosion will occur. It is essential to fullytreat the chilled and hot / cooling water to prevent corrosivetendency.

Water Quality The standard for water in the chilled and hot / cooling water circuitsis shown in the following tables.

STANDARD WATER QUALITY (For Copper tubes)

Items Hot / Cooling water Heat source /Chilled water

Tendency

One-pass orcirculating

Make-up water Circulating Corrosion

Scaling

pH 25C 6.5~8.0 6.5~8.0 6.5~8.0

Electrical conductivity(25lS/cm)

800 max 200 max 500 max

M alkalinity (ppm) 100 max 50 max 100 max

Total hardness (ppm) 200 max 50 max 100 max

Chlorine Ion (ppm) 200 max 50 max 100 max Sulphuric acid ion (ppm) 200 max 50 max 100 max

Total Iron (ppm) 1.0 max 0.3 max 1.0 max

Sulphur ion (ppm) Not detected Not detected Not detected

Ammonium Ion 1.0 max 0.2 max 0.5 max

Silica (ppm) 50 max 30 max 50 max

Free Carbonic acid - - 10 max

Turbidity (NTU) 20 max 5 max 10 maxSuspended solids (mg/l) 20 max 5 max 10 max

Biological OxygenDemand (BOD) ppm

- Below 160 -

Chemical Oxygen

Demand (COD) ppm

- Below 160 -

NOTE :

1. Each item of the standard values has a strong bearing on the failure due to corrosion or scaleformation, and if any value item deviates from the standard value, it will cause corrosion orscaling. Therefore, these should be controlled.

2. The range of the quality of water which may be used differs depending on the chemicals usedto treat the water, and is not given here. It is desirable to set the appropriate water qualitycontrol values under the guidance of a water processing specialist who will periodically controlit.


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Water Circuit Considerations

C*M *** 02 00_0 II - 3

STANDARD WATER QUALITY ( For Cupro Nickel 90:10 tubes )

Items Hot / Cooling water Heat source /Chilled water

Tendency

One-pass orcirculating

Make-up water Circulating Corrosion

Scaling

pH 25C 6.5~8.5 6.5~8.5 6.5~8.5 Total hardness (ppm) 200 max 50 max 100 max

Chlorine Ion (ppm) 4000 max 1000 max 2000 max

Sulphuric acid ion (ppm) 800 max 200 max 400 max

Total Iron (ppm) 1.0 max 0.3 max 1.0 max

Sulphur ion (ppm) Not detected Not detected Not detected

Ammonium Ion 1.0 max 0.2 max 0.5 max

Silica (ppm) 50 max 30 max 50 max

Turbidity (NTU) 20 max 5 max 10 maxSuspended solids (mg/l) 20 max 5 max 10 max

Biological OxygenDemand (BOD) ppm

- Below 160 -

Chemical OxygenDemand (COD) ppm - Below 160 -


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Liquids

III - 1

Chapter 3

Liquids

Lithium Bromide (LiBr) -

absorbent

Lithium Bromide (LiBr) is chemical. It is made from lithium obtainedfrom lithium ore, and bromide obtained from sea water. LiBr andSodium Chloride (NaCl) have similar characteristics, because

Lithium (Li) and Sodium (Na) are alkalis, while Bromide (Br) andChlorine (Cl) are halogens. Sodium Chloride is table salt. Hence wecan easily imagine the properties of LiBr.

If table salt is left in a high humidity atmosphere, it becomes sticky.This is because it absorbes moisture from the atmosphere. LiBr hasthe same characteristics and its absorption power is stronger thanthe table salt. The higher the LiBr solution concentration and thelower its temperature, the stronger its power to absorb watervapour.

. Chemical formula : L iBr

. Molecular weight : 86.856

. Components : Li - 7.99%, Br - 92.01%

. Specific gravity : 3.464 at 25C

. Melting point : 549C

. Boiling point : 1265C

Lithium Molybdate

(Li2MoO4) - Corrosion

Inhibitor

Lithium Bromide has a corrosive action on steel in the presence ofoxygen. As the absorption machine is a vacuum vessel, there isalmost no oxygen in it. However, corrosion inhibitor is added in theabsorbent and the absorbent alkalinity is adjusted. The corrosioninhibitor forms an inert protective layer on the inside surface of themachine and inhibits the metal corrosion by LiBr. The formation ofthe protective layer reduces the concentration of the inhibitor.Hence the absorbent composition should be controlled, that is theamount of inhibitor should be maintained by chemical analysing theabsorbent and recharging inhibitor as required. Excess inhibitorshould not be added as it causes the Lithium Bromide to precipitateand degrades the machine performance.

Water (H2O) -

Refrigerant

Refrigerant used in the absorption machine is water. The watershould be pure and free of contaminants. Distilled water ordemineralised water is used as refrigerant.

Specifications of the water which can be used as refrigerant are

. Specific Resistance : 5 x 105

Ohm/cm. Ca, Mg, Cl, Na : 0.01 ppm max.. Sulphur and Ammonium shall not be detected.

Octyl Alcohol (2-Ethyl-

1-Hexanol) Additive

To increase absorption effect of absorbent, Octyl alcohol is addedinto the machine. Excess quantity of octyl alcohol should not beadded into the machine as it could form a sludge in the heatexchangers and degrade machine performance.

. Molecular weight : 130.23

. Specific gravity : 0.831 ~ 0.836 at 20C

. Refractive index : 1.428 ~ 1.433


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C2M S** 0004_0 IV - 1

Chapter 4

Machine illustration

Chapter Objective This chapter includes the four views of the machine and indicatesthe positions of its various parts and components.

Absorber

E

vapora

tor

E

vapora

tor

HTG

Condenser

DrainOutlet

Steam

Inlet

Side View(Left)

Sight Glass Cooling Water

Inlet


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IV-2

C2MS**0004_0

CoolingWater Inlet

Sight Glass

RefrigerantLevel Electrode

Control Panel

RefrigerantBlowdown Valve

Refrigerant Pump Absorbent Pump Purge Pump

Front View

Refrigerant service valve


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C2MS**0004_0

IV-3

Rear View

Sight Glass

Drain Heat Exchanger

Heat Reclaimer

Low Temperature Heat Exchanger

High Temperature Heat Exchanger

Drain Outlet

Generator SolutionLevel Electrode

Strong solution service valve

Intermediate solution service valve

Weak solutionservice valve


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Chapter 4

IV - 4 C2M S** 0004_0

Side View(Right)

SteamTrap

AbsorberEvap

HTG

LTG

Cooling Water

Outlet

Chilled WaterOutlet

Purge

Pump

Condenser

Chilled WaterInlet

Evap


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C2M **S 0105_0 V - 1

Chapter 5

Controls and Safeties

Chapter Objective This chapter describes the operational controls of the machine and thesafeties provided.

Control Panel The control panel consists of the following components :. Programmable Logic Controller (PLC).. Operator interface.. Power circuit for pumps.. Panel mounted instruments.

Capacity Control The cooling capacity of the machine is the total heat extracted from thechilled water. The chilled water flow rate to the machine is kept constant.Hence the capacity is proportional to the difference in the temperatures ofthe inlet and outlet chilled water.

Load changes are reflected in the rise or fall of the temperature of the inletchilled water. As the inlet chilled water temperature rises or falls the outletchilled water temperature tends to follow the same pattern. A RTD sensor inthe outlet chilled water senses this change in temperature. This signal isfed to the PLC.

An inbuilt software PID control loop processes this signal with respect tothe chilled water set point. A control output signal of 4 to 20 mA is sent tothe I/P converter.

The I/P converter converts the 4 to 20 mA electrical signal to a 0.2 to 1kg/cm

2g pneumatic signal. This pneumatic signal controls the position of

the steam control valve. As the load increases the steam control valve

opens, as the load reduces the steam control valve closes, and thusregulates the quantity of steam entering the machine.

BLOCK DIAGRAM:

PT100 TEMP. SENSOR PLC I to P STEAM CONTROL

CONVERTER VALVE


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Chapter 5

V - 2 C2M **S 0105_0

Safeties Safety devices are provided to protect the machine from abnormalconditions and safeguard it from damage and ensure continued availability.

Safety devices are -

Machine mounted safeties located on the machine,Panel mounted safeties in the control panel, andField Interlocks passing signals from the field to the machine.

Machine mounted

safeties

. Chilled water flow switch :Paddle type device mounted on the chilled water outlet nozzle.

. Chilled water Differential Pressure (DP) switch :Connected to the inlet and outlet chilled water nozzles.

. Chilled water Antifreeze thermostat :Capillary thermostat mounted on the chilled water owlet nozzle

. Absorbent pump thermal cutout :A thermal cutout provided in the absorbent pump stator winding.

. Refrigerant level electrodes :Mounted in the refrigerant level box.

. Generator level electrodes :Mounted in the high temperature generator level box.

Panel mounted safeties . Generator level controller.. Refrigerant level controller.. Absorbent pump overload relay / AC Drive.. Refrigerant pump overload relay.. Purge pump overload relay.. Absorbent pump miniature circuit breaker.. Refrigerant pump miniature circuit breaker.

Field Interlocks . Chilled water pump interlock.. Cooling water pump / butterfly valve interlock.

Safety Functions The safety functions of the machine protect it against abnormal conditions.The various safety functions are

Thermal shock protection.Antifreeze protection.Crystallization protection.Cavitation protection of refrigerant pump.Cavitation protection of absorbent pump.Motor protection.

Thermal shock

protection.

To protect the machine from thermal shock, the steam control valve is

opened gradually for first 10 minutes after machine start up, when the HTGtemperature is less than 70C. After the slow opening duration is over, thecontrol is switched over to chilled water temperature modulationautomatically.

Antifreeze protection. To prevent the chilled water from freezing in the evaporator tubes, thesafety functions below stop the machine if abnormal conditions leading toice formation appear.

L-cut : If the chilled water outlet temperature drops below the L-cut setpoint, therefrigerant pump is switched off. The L-cut is set from the cool modecontrol loop screen. This safety prevents further temperature drop of the

chilled water. The refrigerant pump will restart after the Chilled water outlettemperature rises above the L-cut setpoint plus the hysterisis set point.


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C2M **S 0105_0 V - 3

Internal antifreeze : If the chilled water outlet temperature drops below the internal antifreezeset point, the machine trips and the TOTAL SHUTDOWN alarm sequenceis carried out. The alarm will be reset only after the chilled water outlettemperature rises above the internal antifreeze set point plus the hysterisisset point.

Antifreeze thermostat : If the chilled water outlet temperature drops below the setting of thermostat,the TOTAL SHUTDOWN alarm sequence is carried out.

Chilled water pump

interlock :

Chilled water flow is essential for machine operation. A potential freecontact is to be wired from the chilled water pump motor starter to VAM/cpanel to sense chilled water pump ON / OFF / TRIP status. The machinestarts only when the chilled water pump is ON. If the chilled water pumpstops / trips during operation, the TOTAL SHUTDOWN alarm sequence iscarried out.

Chilled water flow

switch :

If the chilled water flow drops below 50% of the rated value, the TOTALSHUTDOWN alarm sequence is carried out.

Chilled water DP switch If the chilled water flow drops below 50% of the rated value, the TOTAL

SHUTDOWN alarm sequence is carried out.

Crystallization

prevention

If the concentrated absorbent solution returning to the absorber from thelow temperature generator is excessively cooled, it crystallizes in the lowtemperature heat exchanger and the operation of the machine is affected.Crystallization occurs either when the concentration of the absorbent(related to its temperature) goes too high or its temperature dropsexcessively. The following safety functions prevent the machine fromcrystallizing.

Valve control on HTG

temperature

When the HTG temperature exceeds the 159C, the steam control valvecloses immediately. This prevents further increase in LiBr concentration.

The valve control is returned to the chilled water temperature control loopwhen the HTG temperature drops below 155C.

HTG high temperature

safety

If the HTG temperature exceeds the HTG high temperature set point(160C), the DILUTION CYCLE alarm sequence is carried out and themachine goes into dilution cycle immediately. HTG high temperature alarmcan be reset only when the HTG temperature drops below the set pointminus the hysterisis set value (5C).

Cooling water low

temperature safety:

If the cooling water inlet temperature drops below the cooling water lowtemperature set point, the DILUTION CYCLE alarm sequence is carriedout and the machine goes into dilution cycle immediately. The alarm canbe reset only when the cooling water inlet temperature rises above the

cooling water low temperature set point plus hysterisis set value.

Cavitation protection of

refrigerant pump.

If the refrigerant level in the evaporator pan falls excessively, the pressurein the refrigerant pump suction drops below the saturation pressure of therefrigerant and the refrigerant pump starts to cavitate. To ensure minimumacceptable suction pressure the level of refrigerant is not allowed to fallbelow a certain level. This is done by means of three level electrodes, RE1,RE2, RE3, and a level relay, 33RL.

The three electrodes are mounted in the refrigerant level boxassembly on the lower shell (Evaporator side). RE1 electrode is thesmallest in length and RE3 is the longest. The level is maintained betweenRE1 and RE2. RE3 acts as a reference electrode. When the level reaches

RE1, the pump starts and when the level goes below RE2, the pump stopsand restarts only when the level reaches RE1 again. When the level goesbelow RE2, a delay of 20 seconds is provided before the pump is switched


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Chapter 5

V - 4 C2M **S 0105_0

off.

Cavitation protection of

absorbent pump.

If the absorbent level in the absorber sump falls excessively, the pressurein the absorbent pump suction drops below the saturation pressure of theabsorbent solution and the absorbent pump starts to cavitate. To ensureminimum acceptable suction pressure, the level of absorbent is controlled.

Absorbent level in the HTG is not allowed to rise above a certain level. Thisprevents excess absorbent from being pumped out of the absorber sump.

This is done by means of three level electrodes, AE1, AE2, AE3, and alevel relay, 33AL.The three electrodes are mounted on the high temperature generator levelbox. AE1 is the smallest electrode and AE3 is the longest. The level is to bemaintained below AE1. AE3 acts as the reference electrode. When thelevel reaches AE1, the pump stops after a delay of 5 seconds. When thelevel goes below AE2, the pump restarts.

Motor protection safeties

Absorbent pump thermal

cutout (ATHC)

A thermal cutout in the winding of the absorbent pump motor opens if thetemperature of the winding rises above the permitted level. If this contact

opens the DILUTION CYCLE alarm sequence is carried out. This alarmcan be reset only when the ATHC contact closes after the windingtemperature drops below the maximum permitted level.

Absorbent pump

overload relay / AC

Drive

If the absorbent pump motor draws more than its rated current, thisoverload relay trips and the DILUTION CYCLE alarm sequence is carriedout. The alarm is reset by resetting the overload relay / AC Drive.

Refrigerant pump

overload relay

If the refrigerant pump motor draws more than its rated current, thisoverload relay trips and the DILUTION CYCLE alarm sequence is carriedout. Resetting the overload relay resets the alarm.

Purge pump overloadrelay

If the purge pump motor draws more than its rated current, this overloadrelay trips. Resetting the overload relay resets the alarm.

Short Circuit Protection Miniature Circuit Breakers (MCBs) are provided in the power circuits of theabsorbent, refrigerant and purge pumps. If a short circuit fault occurs inthe power supply to the pumps, the MCBs trips.


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C2M **S 0105_0 V - 5

Alarm sequences : There are three alarm sequences which activate when the fault conditionsoccur

. Dilution cycle alarm sequence.

. Total shutdown alarm sequence.

. Power failure alarm sequence.

Dilution cycle alarm

sequence.

This alarm sequence protects the machine from crystallisation.

Fault conditions which activate this alarm sequence are -

. High temperature generator temperature high.

. High temperature generator pressure high.

. All temperature sensor errors except chilled water outlet temperaturesensor.

. Cooling water inlet temperature low.The alarm action is as follows

Steam control valve closes immediately.

Refrigerant pump stops.

Machine goes into dilution cycle for 20 minutes.

After 1 minute the cooling water pump stops or shut-off valve closes.

If the operator does not acknowledge the fault within 20 minutes, themachine stops completely.

Total Shutdown Alarm

Sequence

This alarm sequence protects the machine from freezing of the evaporatoror any other damage.

Fault conditions which activate this alarm sequence are -

. Chilled water flow switch trip.

. Chilled water D.P. switch trip.

. Chilled water pump interlock trip.

. Chilled water antifreeze thermostat trip.

. Chilled water outlet temperature sensor fault.

. Antifreeze trip inbuilt in the PLC software.

. Absorbent pump over current trip / AC Drive trip.

. Absorbent pump thermal cutout trip.

. Absorbent pump contactor / AC Drive not responding.

. Refrigerant pump over current trip.

. Refrigerant pump contactor not responding.

. MCB1 (Absorbent pump) / MCB2 (Refrigerant pump) trip.

The alarm action is as follows

Steam control valve closes immediately.

Refrigerant and absorbent pump stop.


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Chapter 5

V - 6 C2M **S 0105_0

Machine shuts down.After the fault(s) is reset the machine goes into dilution cycle. If themachine is not restarted during the dilution cycle, the machine stopscompletely after the dilution cycle is over.

Power failure alarm

sequence

This alarm is displayed when the machine is powered up after a powerfailure during operation. Acknowledge and reset the alarm and restart the

machine.

Alarm acknowledgment

and reset sequence

When an alarm sequence is initiated, the alarm screen will pop up, with anaudio alarm.

Unless and until the activated alarm is acknowledged the user will not beallowed access to any other screen.

Currently activated alarm(s) will be displayed, with the date and time.

Press ACK to stop the hooter (audio signal).

If there is more than one alarm, pressing the ACK key will display the

next active alarm. Use ACK key to scroll through all active alarms.

After rectifying the fault condition, each alarm will have to beindividually displayed on the ALARM screen, and then reset all the

alarm conditions by pressing the alarm reset key i.e. K4 key.

Start the machine by pressing the key on the OPERATION screen.

Example If the chilled water pump trips, three alarms will be triggered :

Chilled water pump OFF / TRIPChilled water flow switchTRIPChilled water DP switch TRIP

. The ALARM screen will pop-up and the hooter will start. CHILLEDWATER PUMP OFF / TRIP will be displayed on the ALARMscreen.

. Pressing ACK key will stop the hooter, and CHILLED WATER FLOW

SWITCH TRIPPED will be displayed on the ALARM screen.

. Pressing ACK again will display the next active alarm i.e. CHILLED

WATER DP SWITCH TRIPPED.. Once all the alarms have been acknowledged, go to the STATUS screen

and monitor the current status of the concerned devices, i.e.

Chilled water pump CHW PUMP OFFChilled water flow switch FLSw TRIPChilled water DP switch DPSw TRIP

. After the chilled water pump has been started and the required flow isresumed, the STATUS screen display will be -

Chilled water pump CHW PUMP ONChilled water flow switch FLSw HEALTHYChilled water DP switch DPSw HEALTHY

. Once this condition is achieved, press alarm reset K4 key to reset the

alarms. The red LED will go off to indicate that the alarm has beenreset.

Start the machine by pressing the 'M/C START' key on the operationscreen.


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C2M **S 0105_0 V - 7

Set points The field instruments and the components in the control panel are to be setas follows

S.NO. Description Set points

1. Chilled water flow switch 50 % of rated flow

2. Chilled water D.P. switch 50 % of rated flow

3. Antifreeze thermostat 4.0C

4. Absorbent pump over current relay As per pump rating

5. Refrigerant pump over current relay As per pump rating

6. Purge pump over current relay As per pump rating

OP 7 Set points The operator terminal settings are as follows

S.NO. Description Set points Remarks

1. Chilled water temperature control set point(CHWSP)

- Refer machine specs.

2. Chilled water temperature modulationcontrol settings:

a) Proportional Band - 85

b) Integral Band + 10

c) Derivative Band 0

3. L-cut set point CHWSP - 1C

4. L-cut hysterisis 2C

5. Internal PLC software antifreeze CHWSP - 1.5C

6. Internal PLC software antifreeze hysterisis 2C

7. Cooling water inlet temperature set point 20C

8. Cooling water inlet temperature hysterisis 5C

9. HTG trip set point 160C

10. HTG hysterisis 5C

11. HTG set point for controlling the steamcontrol valve

159C Not accessible

12. HTG temperature set point for AC drive forabsorbent pump speed control

140C Optional

13. Steam control valve maximum travel limit As per capacitytesting

14. Data log sampling time 60 min Adjustable

15. Trip log sampling time 1 min Adjustable

16. Anti-chattering timer 2 sec Not accessible

17. Dilution cycle timer 20 min Not accessible


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Chapter 5

V - 8 C2M **S 0105_0

18. ON delay timer for absorbent pump 5 sec Not accessible

19. ON delay timer for refrigerant pump 20 sec Not accessible

PLC Input/Output

assignments

Digital Inputs 24 VDC type OnboardPLC S7-200 CPU 226Address Device Tag Description

I 0.0 52W Chilled water pump interlock

I 0.1 69W Chilled water flow switch

I 0.2 DPS2 Chilled water DP switch

I 0.3 26W Antifreeze thermostat

I 0.4 SPARE SPARE

I 0.5 ATHC Abso pump thermal cutout

I 0.6 MCB 1&2 MCB 1 & 2 onI 0.7 88A Abso pump contactor/AC Drive ON

I 1.0 51A Abso pump overload

I 1.1 88R Refrigerant pump contactor on

I 1.2 51R Refrigerant pump overload

I 1.3 51P Purge pump overload

I 1.4 33AL HTG level low

I 1.5 33RL Evaporator level low

I 1.6 4Y1 Remote start/stop

I 1.7 SPARE SPARE

I 2.0 SPARE SPARE

I 2.1 SPARE SPAREI 2.2 SPARE SPARE

I 2.3 SPARE SPARE

I 2.4 SPARE SPARE

I 2.5 SPARE SPARE

I 2.6 SPARE SPARE

I 2.7 SPARE SPARE

Digital outputs 24 VDC type onboardPLC S7-200 CPU 226Address Description

Q 0.0 Hooter

Q 0.1 Refrigerant pump onQ 0.2 Purge pump on

Q 0.3 Remote machine on indication


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C2M **S 0105_0 V - 9

Q 0.4 Remote machine trip indication

Q 0.5 Chilled water pump start enable

Q 0.6 Cooling water pump start enable

Q 0.7 CT Fan start enable

Q 1.0 Absorbent pump / AC drive start

Q 1.1 * AC Drive preset speed 50 Hz

Q 1.2 * AC Drive inline contractor Q 1.3 SPARE

Q 1.4 SPARE

Q 1.5 SPARE

Q 1.6 SPARE

Q 1.7 SPARE* Only used if AC Drive is provided

Analog Input / OutputAnalog Inputs RTD PT100 and Outputs 4 ma to 20 ma

Module type EM235 2 Nos. in slot 0 and slot 2

Address Description

AIW0 Chilled water inlet temperature

AIW2 Chilled water outlet temperature

AIW4 Cooling water inlet temperature

AIW6 Cooling water outlet temperature

QW0 Signal to I/P converter

AIW8 HTG temperature

AIW10 Dilute solution temperatureAIW12 Spray solution temperature

AIW14 HTG vapour temp.

QW4 Modulation signal for AC Drive

OP7 Operator Interface:- The entire operation of the VAM/c is controlled through the OP7

operator interface.

OP7 consists of:

1. A LCD display 4-Lines * 20-characters.

2. Function keys F1 to F4 andK1 to K4

3. Arrow keys Left, Right, Up, Down.4. Numeric keys 0 to 9 with decimal point.5. ENTER key to enter set points.6. ACK key to acknowledge Hooter/Alarm.

K1 to K4 keys are global keys with functions

K1 MAIN MENU

K2 MACHINE PARAMETERS

K3 MACHINE STATUS


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Chapter 5

V - 10 C2M **S 0105_0

K4 FAULT RESET

The LCD display is programmed to show the interface screens. A screenconsists of a combination of indications, and keys. Through these, themachine status is observed, and its operation can be controlled.

Screen tree structure is given below

MAIN MENUOPERATIONSTATUSSETPOINTS'M/C PARAMETERS''UTILITY'ALARMS'DATALOG

'NORMAL''TRIP'

'SERVICES''M/C OPERATION''HTG / COW SP''LCUT / HCUT SP''OFFSET ADJ''PID SETTINGS''A/C DRIVE SETTINGS'M/C/ COMM DATE'

'PLC DATE / TIME''PRODUCT INFO''M/C MODES''ALARM LOG

Product Info Screen This screen is the startup screen and is displayed on power up. The firstpage of this screen displays the Product and Model number.

T H E R M A X L T D , I N D I A

P r o d u c t : S F / H F

V A P O U R A B S O R P T I O N

M A C H I N E

The second page is accessed by pressing the F4 key.

P L C S o f t w a r e : -

S F H F - P L C O P - 1 . 0 - 0 2 0 1

M M I S o f t w a r e : -

S F H F - O P - 1 . 0 - 0 2 0 1

The second page displays the software version loaded in theProgrammable Logic Controller (PLC) and the Operator Interface (OP7)also called the Man Machine Interface (MMI).

This screen can also be accessed from 'MAIN MENU'

Press K1 to go to Main Menu.

Main Menu : This screen displays the names of all the other function and operation


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C2M **S 0105_0 V - 11

Access - K1 Key

screens.

The first page of the 'MAIN MENU' screen shown the names of the'OPERATIONS', 'STATUS', and 'SETPONTS' screens, and shows the keysto be pressed to activate them.

M A I N M E N UO P E R A T I O N [ F 1 ]

S T A T U S [ F 2 ]

S E T P O I N T S [ F 3 ] > >

The other pages of the MAIN MENU screen can be displayed by scrolling

down using the F4 key.

The second page shows the M/C PARAMETERS, and the UTILITYactivation keys.

M / C P A R A M E T E R S [ F 1 ]U T I L I T Y [ F 2 ]

< < > >

The third page shows the ALARMS and the 'DATALOG screen activationkeys.

A L A R M S [ F 1 ]

D A T A L O G [ F 2 ]

< < > >

The fourth page shows the SERVICES and the 'PLC DATE/TIME screenactivation keys.

S E R V I C E S [ F 1 ]

P L C D A T E / T I M E [ F 2 ]

< < > >

The fifth page shows the PRODUCT INFO, 'M/C MODES' and the 'ALARMLOG screen activation keys.

P R O D U C T I N F O [ F 1 ]

M A C H I N E M O D E S [ F 2 ]

A L A R M L O G [ F 3 ]

< >

Start the machine by pressing F1 and stop the machine by pressing F2. If

the machine is ready to start the following message will be displayed - "MACHINE READY TO START ".

If there is any fault condition then the following message will be displayed -" MACHINE NOT READY TO START ".

At the same time the machine status is also displayed.

The next page can be displayed by pressing F4 function key

Refrigerant pump auto / manual selection screen

R E F R P U M P : A U T O

A U T O M A N

F 1 F 2 < < > >

This screen is used to select the mode of operation of the refrigerantpump. In order to start or stop the refrigerant pump irrespective of theevaporator level, (for e.g. during Blowdown cycle) the refrigerant pump hasto be in MANUAL mode. Default position is AUTO.

Refrigerant pump AUTO / MANUAL mode can be changed using the F1

and F2 keys. To operate refrigerant pump in AUTO mode press F1 key,

To operate refrigerant pump in manual mode press F2 key. Present mode

status is also displayed.

Refrigerant pump manual operation screen

R E F R P U M P : O F F

S T A R T S T O P

F 1 F 2 < < > >

This screen is used to switch the refrigerant pump on or off manually. Itworks only when the refrigerant pump is in MANUAL mode. This screenaction is disabled when the refrigerant pump mode is in AUTO mode.Default position is STOP.

Refrigerant pump START / STOP operation can be done using the F1 and

F2 keys. To start the refrigerant pump press F1 key. To stop the

refrigerant pump press F2 key. The current pump status is also displayed.


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C2M **S 0105_0 V - 13

Purge pump operation screen

P U R G E P U M P : O F F

S T A R T S T O P

F 1 F 2 < < > >

The Purge pump can be switched on or off from this screen. Defaultposition is STOP. Current pump status is also displayed.

Purge pump START / STOP operation can be done using F1 and F2 keys.

To start the purge pump press F1 key. To stop the purge pump press F2

key.

Concentration limit control activation screen

C O N C L I M I T : O F F

O N O F F

F 1 F 2 < < > >

Concentration control can be activated or deactivated using F1 and F2

keys. To switch ON concentration control press F2 key. To switch OFF

concentration control press F1 key.

Chilled water inlet temperature control override screen

C H W I N O V E R R I D E : O F F

O N O F F

F 1 F 2 < >

TRIP D'LOG TIME - During machine trip condition, the machineparameters are logged at the interval of specified time interval. To changethis set point scroll down cursor at set point value, cursor blinks here, type

required time interval in minutes and press ENTER key.

NORMAL D'LOG TIME - This is the time interval at which PLC logs allmachine parameters. To change this set point scroll down cursor at setpoint value, cursor blinks here, type required time interval in minutes and

press ENTER key.

N O R D ' L O G T I M E : 6 0 M

T R I P D ' L O G T I M E : 1 MS C V O U T P U T L I M I T : 7 5 %

< < > >

VALVE LIMIT - As the steam control valves are selected for the range ofmachine models, the value of steam control valve opening at which therated capacity is achieved has to be the limit for valve openings. This valuedetermines the maximum limit on the steam control valve opening. Tochange this set point scroll down cursor to this set point value. When the

cursor blinks here, type the required %, and press ENTER key.

DIL. SOL TEMP S.P. FOR DECRYSTALISATION OR HOT DEGREASING -This set point is used to control steam valve in the de-crystallization / hot

degreasing mode.D I L . S O L T E M P S . P .

F O R D E C R Y S T A L I S A T I O N

O R H O T D E G R E A S I N G

1 2 3 . 4 < >

Go to the next page of the screen by pressing the F4 key

P U R G E R U N H R S : 1 2 3

L A S T P U R G E D O N E O N

0 1 / 0 8 / 0 0 1 1 : 0 0

< < > >

In the second page of this screen, the number of purge pump run hours isdisplayed. The date and time at which the purge pump was last run is also


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C2M **S 0105_0 V - 15

displayed

Go to the next page of the screen by pressing the F4 key

M / C C O M M I S I O N E D O N

D A T E 0 1 / 0 8 / 0 0

M A I N [ F 1 ] < >

Press F1 to display normal data log.

Press F2 to display trip data log.

Using F3 and F4 Keys scroll pages UP/DOWN.

Service Settings The critical machine parameter settings can be edited through theSERVICE screen. To avoid access from unauthorized persons, thesescreens are password protected

There are 7 pages of Service Settings

1. M/c OPERATIONS2. HTG / COW SP3. L-CUT / H-CUT SP4. OFFSET ADJ5. PID SETTINGS6. DRIVE SETTINGS7. M/C COMM DATE

S E R V I C E S E T T I N G S

M / C O P E R A T I O N S [ F 1 ]

H T G / C O W S P [ F 2 ]> >


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Chapter 5

V - 16 C2M **S 0105_0

L - C U T / H - C U T S P [ F 1 ]

O F F S E T A D J [ F 2 ]

< < > >

P I D S E T T I N G S [ F 1 ]

D R I V E S E T T I N G S [ F 2 ]

< < > >

M / C C O M M . D A T E [ F 1 ]

< >

HTG TEMP. TRIP SP - If actual HTG temperature exceeds this set pointvalue, machine trips on 'HTG TEMP. HIGH ALARM'.

HTG HYSTERISIS - This value determines the HTG temperature, below theHTG TEMP TRIP SET POINT, at which the HTG temp high alarm can bereset. The HTG temp high alarm can be reset only when the actual HTGtemperature is less than 'HTG TEMP TRIP SETPOINT ' - 'HTGHYSTERISIS'.

C O W I N T R I P S P : 1 2 3 . 4

C O W I N H Y S T : 1 . 2

< < > >

COOLING WATER IN TRIP SETPOINT - If cooling water inlet temperaturedrops below this value machine trips on "COW IN TEMP LOW" alarm.

COW HYSTERISIS - This value determines the value of cooling water inlettemp at which the alarm can be reset. The alarm is reset at "COW IN TRIPSP" + "COW HYSTERISIS"

CT FAN OFF SETPOINT - This value determines the temperature ofCOOLING WATER at which the cooling tower fan is to be switched off.

CT HYSTERISIS - This value determines the actual cooling water inlet tempabove the CT fan off setpoint at which the cooling tower fan would restart.


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C2M **S 0105_0 V - 17

L-CUT/H-CUT SP

L C U T S P : 6 . 0

L C U T H Y S T : 1 . 2

< < > >

L CUT SP - This is one of the antifreeze safeties for chilled watertemperature. If the chilled water temperature drops below this value therefrigerant pump stops. Set this value at 'CHILLED WATER OUTLETTEMPERATURE SP' - '1.O' (degree C).

L CUT HYST This set point determines the value above the L CUT SP atwhich the refrigerant pump restarts. The refrigerant pump restarts when thechilled water outlet temperature becomes greater than or equal to L CUTSP + L CUT HYST. Unit is degree centigrade.

ANTIFREEZE SP - If the Chilled water outlet temperature drops below this

set point the machine trips on 'INTERNAL ANTIFREEZE ALARM'. Set thisvalue at 'CHILLED WATER OUTLET TEMPERATURE SP' - 1.5 O C.

ANTIFREEZE HYST - The antifreeze trip alarm can be reset only when theChilled water outlet temperature exceeds ' ANTIFREEZE SP' +

ANTIFREEZE HYST.' Unit is degree centigrade.

A N T I F R E E Z E : 4 . 5

A N T I F R E E Z E H Y S T : 1 . 2

M A I N [ F 1 ] < < > >

H CUT SP - If the Chilled water outlet temperature goes above this value analarm is activated. Value set is in O c.

H CUT HYST - This value determines the actual temperature of chilledwater outlet below the 'H CUT TRIP SP at which the chilled water outlettemp. High alarm can be reset. The alarm will only reset when the outlettemp value is less than ' H CUT TRIP SP' - 'H CUT TRIP HYST'

H C U T S P : 1 2 . 3

H C U T H Y S T : 1 . 2

M A I N [ F 1 ] < >

S C V : A U T O

A U T O M A N

F 1 F 2 < < > >

S C V O P E N I N G

M A N U A L M O D E


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Chapter 5

V - 18 C2M **S 0105_0

O P E N C L O S E

F 1 F 2 < >

A C D R I V E : I N L I N EI N L I N E [ F 1 ]

B Y P A S S [ F 2 ]


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C2M **S 0105_0 V - 19

< >

Machine commissioned date is over written by pressing this key.

PLC date / time This screen displays the current DATE and TIME of the PLC

P L C D A T E & T I M E

D A T E - 0 1 / 0 1 / 0 1

T I M E - 1 2 : 0 0 : 0 0

> >

Current DATE and TIME of PLC can be changed in this screen. Typeseach field of DATE and TIME and press ENTER key on OP7 and to write

this to PLC - press ENTER (F1) key.

C H A N G E D A Y ( 1 - 7 ) : 1

D A T E - 0 1 / 0 1 / 0 1

T I M E - 1 2 : 0 0 : 0 0

E N T E R [ F 1 ] < >

DECRYSTALISATION - By pressing F1 key machine can be operated inde-crystallization mode.

If the machine was in operation prior to pressing the de-crystallization keythen machine carries out dilution cycle of 20 minutes and then goes to de-crystallization mode.

The machine operates in de-crystallization mode for the time set from OP7.After the timing is over de-crystallization mode is stopped and absorbentpump continues to run for 20 minutes.

In de-crystallization mode if machine trips on any alarm then de-crystallization machine carries out dilution cycle. De-crystallization mode


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Chapter 5

V - 20 C2M **S 0105_0

can be switched off by pressing F2 key. Machine can not be started in de-

crystallization mode.

In de-crystallization modea. Chilled water pump is off.b. Cooling water pump is off.c. Cooling Tower fan is off

d. Refrigerant pump is off.e. Absorbent pump is on.g. Steam control valve is open

Steam control valve opening is controlled on Dilute solution temp and HTGtemp. If dilute solution temp exceeds 90C or HTG temp exceeds 130CSteam control valve is closed, and is opened only when the respectivetemperatures drop below their hysterisys values.

Alarm Log In this screen, the last six alarms logged in PLC are displayed. By pressingF3 and F4 keys all six alarms can be scrolled.

1 .

H T G T E M P H I G H A L A R M

0 1 / 0 1 / 0 1 1 2 : 0 0

< < > >


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Operation of the Machine

Siemens (1.0) VI - 1

Chapter 6

Operation of the Machine

Chapter Objective This chapter describes the pre-start checks, starting procedure andthe stopping procedure.

Pre - start checks . Switch on the input power supply to the control panel.. Check and maintain the vacuum in the machine.. Check all the set points on the operator panel.

( Refer list of set points ). Set the position of all the function keys on the operator panel, as

follows :

MACHINE status. - OFFPURGE key. - STOPREF. PUMP key. - AUTOAUTO/MAN key - AUTO

Note : - These settings are default and should appear when themachine is powered up.

Starting Procedure . Start the chilled water pump and maintain the required P across themachine. If the flow rate is less than minimum rated flow,CHILLED WATER FLOW LOW status will be displayed on theSTATUS screen of the operator panel. After setting right theflow, the DP switch and the flow switch will indicate HEALTHYindication.

. Start the hot / cooling water pump / flow and maintain the required

P across the machine.. Start the air-compressor and / or maintain the required air pressure

(oil and moisture free air) supply to the air filter regulators.

. Open the isolating valve before the steam control valve and maintainthe required dry and saturated steam pressure before thesteam control valve.

. Give machine START command on the operator panel. Machine ONindication is displayed on the STATUS screen.

. Absorbent pump contactor 88A is energized. Absorbent pumpON/OFF is controlled by the level controller 33AL. Absorbentpump ON/RUN indication is displayed on the STATUSscreen.

. Refrigerant pump contactor 88R is energized. Refrigerant pumpON/OFF is controlled by the level controller 33RL. Therefrigerant pump ON/RUN indication is available on the

STATUS screen.. Slow opening of steam control valve starts and opens from 0-100% in

10 minutes, when the high temperature generator temperatureis below 70C. The steam control valve slow openingindication is available on the STATUS screen.

. After 10 minutes the control valve is put into modulation control. Thevalve opening is controlled according to the chilled water PIDtemperature control and the valve status will be displayedaccordingly.

When the potential free contacts of the PLC are used to start or stopchilled water pump and hot / cooling water pump or shut off valve, themachine start command automatically starts the chilled water pumpand the hot / cooling water pump or opens the cooling water shut offvalve in proper sequence.


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Chapter 6

VI - 2 Siemens (1.0)

Stopping Procedure . Press the M/C STOP switch into the OFF position on the operatorpanel.

. Steam control valve closes immediately.

. The contactor 88R is de-energized and the refrigerant pump stops.

. Machine goes into dilution cycle and the indication DILUTIONCYCLE ON on the STATUS screen.

. Hot / Cooling water pump stops or shut off valve closes after 1minute.

. The status screen will indicate hot / cooling water pump / shut offvalve DISABLED.

. After 20 minutes, dilution cycle completes and the absorbent pumpstops.

. STATUS screen indicates MACHINE : OFF.

. Stop the chilled water pump / flow.

. The machine stops completely.

When the potential free contacts of the PLC are used to start and stopthe chilled water pump and hot / cooling water pump / shut off valve,the machine stop command automatically stops the chilled water pumpand the hot / cooling water pump or closes the cooling water shut offvalve in proper sequence.


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C2M ***0007_0 VII-1

Chapter 7

Operational Activities

Chapter Objective This chapter describes the operational activities required to keep themachine in best condition. These activities are

Air purging

Blowdown of refrigerantMaintenance of operating logThese should be carried out as per the Operational Activity Schedule

Air Purging Air purging is the activity by which non condensable gases areremoved from the machine. This is done by operating the vacuumpump and opening the manual air purge valves. After purging iscompleted the valves are closed and the vacuum pump is stopped.

Air Purging SystemPurge unit

Valve assly

Manometer

Service valves

Purge pump

The air purging system (see Figure 7.1) consists of -Non condensable gases and water vapour are drawn from the

absorber into the purge unit by a venturi action using

absorbent bled off the absorbent pump discharge. The gasesare bubbled through LiBr collected at the bottom of thestorage tank to remove water vapour. The non condensablegases collect to a maximum pressure of 50mmHg.

This consists of an arrangement of three diaphragm valves that enablethe operator to connect the vacuum manometer to differentparts of the machine by closing and opening the valves.

A mercury in glass vacuum manometer capable of reading vacuumfrom 0mmHg absolute to 100mmHg absolute.

One service valve provides access for the manometer to the machineand the other provides access for maintenance procedureslike N2 charging and sampling.

A double stage oil sealed vacuum pump for evacuating the machine

and carrying out maintenance procedures.

Measuring vacuum Three different vacuum measurements are carried out. The positionsof the manual purge valves for these measurements are described inthe table below.

Position of Manual Purge Valves

Vacuum reading Valve no. 1 Valve no. 2 Valve No. 3

Ultimate (No Load) Vacuum Open Closed Closed

Pressure in the storage tank Closed Open Closed

Pressure in the shell Closed Closed Open

Reading the manometer The manometer (see Figure 7.2) consists of a glass tube fitted into acasing with a graduated scale. One end of the glass tube issealed and the other end is connected to the vessel whosedegree of vacuum is to be measured. Mercury fills the glasstube from the sealed end to the bottom of the graduated scale.

When the manometer is connected to a vessel at a vacuum of100mmHg or greater, the mercury drops in the sealed leg ofthe glass tube. The degree of vacuum is the difference in thelevel of mercury in the two legs. This is read off the graduatedscale.

The level of mercury in the sealed leg of the manometer should alwaysbe higher than the other leg. Otherwise the reading is wrong

and the manometer has to be repaired.


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Chapter 7

VII - 2 C2M *** 0007_0

When the manometer is connected to the atmosphere the mercuryshould rise to the top of the sealed leg. If there is a gapbetween the mercury and the top of the sealed leg of themanometer, it is faulty and should be repaired.

Kinds of air purging The two types of air purging arePurging from the storage tank, andPurging from the shell.

The procedure followed for the two types of purging are the sameexcept for the position of the manual purge valves (shown in the earliertable)

Air purging procedure . Power on the machine panel if it is off.. Start the purge pump.. Check that the purge pump is running well.. Open Manual purge valve No. 1.. Check that the ultimate (no load) vacuum developed by the vacuum

pump is 4mmHg or less.. Open

Manual purge valve No. 2 - for purging storage tank.

Manual purge valve No. 3 - for purging from shell.. Continue operation of purge pump till purging is completed.. Close

Manual purge valve No. 2 - when purging storage tank.Manual purge valve No. 3 - when purging from shell.

. Continue operation of purge pump for 30 minutes to remove watervapour from pump oil.

. Close Manual purge valve No. 1.

. Stop the purge pump.

Precautions . Check that the ultimate vacuum of the purge pump is 4mmHg or lessbefore air purging.

. Carry out air purging at least once a week. Purging may be requiredat more frequent intervals.

. Always keep the gas ballast valve open while purging to prevent waterfrom contaminating the purge pump oil.

. Carry out purging from storage tank before the storage tankpressure reaches 50mmHg.

Blowdown of refrigerant During operation, a small amount of absorbent disperses in therefrigerant and accumulates over time, resulting in a reduction incooling capacity. Blowdown is carried out to purify the refrigerant.Contaminated refrigerant collected in the refrigerant pan is transferredto the absorber sump. Pure, fresh refrigerant collects in the refrigerantpan.

Procedure . Put the refrigerant pump switch into auto mode if it is not soalready.

. Confirm that the refrigerant pump is running and refrigerant is visiblein the sight glass.

. Open the refrigerant blowdown valve completely. Refrigerant startsbeing pumped to the absorber sump.

. Wait till the refrigerant pump stops due to low level signal from therefrigerant level relay (about 15min), and close the refrigerantblowdown valve completely.

. Refrigerant will start building up and the refrigerant pump will startwhen the refrigerant level reaches the center of the evaporator

sight glass. (About 20 min)


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C2M ***0007_0 VII - 3

. Repeat the procedure two or three times for complete purification of refrigerant.


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Chapter 7

VII - 4 C2M *** 0007_0

Manual purge

valve No.1

Manual purge

valve No. 2

Manual purge

valve No.3

Purge pump

Vacuum

Manometer

Purgetank

Service valve

PurgeCheck

valve

Purge System

Figure 7.1

20

2030

50

40

10

10

0

50

30

40

MANOMETER

Figure 7.2


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C2M ***0007_0 VII - 5

Precautions . Outlet chilled water temperature goes up during the blowdownprocedure and will go down when the refrigerant restarts. Blowdownoperation is carried out when chilling requirement is not critical.. Carry out refrigerant blowdown once a week.

Operating log Record readings in accordance with the operating log at frequentintervals. These aid the operator to recognize both normal and

abnormal machine conditions and also aids in planning the preventivemaintenance schedule and in diagnosing machine problems. A typicaloperating log sheet is shown below.

Re. Items Unit Date : / /

1. Time : : : :

2. Ambient temp. C

3. Chilled water flow rate m3/hr

4. Chilled water inlet & outlet temp. C ( / ) / / /

5. Chilled water inlet & outlet pressure kg/cm2g / / /

6. Hot / Cooling water flow rate m3/hr

7. Hot / Cooling water inlet & outlet temp. C ( / ) / / /

8. Hot / Cooling water inlet & outlet pressure kg/cm2g / / / 9. Generator temp. C

10. Generator pressure mmHg

11. Absorbent pump pressure kg/cm2g

12. Generator fluid level O

13. Absorber fluid level O

14. Evaporator fluid level O

15. Supply steam pressure kg/cm2g

16. Steam flow rate kg/hr

17. Steam control valve opening %

18. Pressure in storage tank mmHg

19. Pressure in shell mmHg

20. Attained vacuum of purge pump mmHg

21. Concentration of diluted absorbent %

22. Concentration of intermediate absorbent %

23. Concentration of conc. absorbent %

24. Concentration of refrigerant %

Operational activity

Schedule

This section lists the operational activities in a schedule to be carriedout on a daily, weekly, monthly, and quarterly basis.

Daily . Check chilled water and hot / cooling water flow rates.. Check steam inlet temperature and pressure.. While the machine is in operation the following may be observed -. No abnormality in the steam control valve.. No abnormal sound in the absorbent, refrigerant and purge pumps.. No other abnormality.

Weekly . Check oil in vacuum pump.. Air purging. Blowdown refrigerant.. Check pH and hardness of chilled and hot / cooling water.

Monthly . Check and record TRG readings of Absorbent and refrigerant pumps

Quarterly . Measure and record current drawn by absorbent, refrigerant andpurge pump.


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Chapter 7

VII - 6 C2M *** 0007_0

. Analyze and control chilled and hot / cooling water quality.


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Dos and Don'ts

VIII - 1

Chapter 8

Dos and Don'ts

Chapter Objective This chapter describes various activities which are to be carried outin the operation of the machine and others which should not bedone.

Dos Blowdown refrigerant once a week.Purge non condensable gases from the purge unit, if the storage

tank vacuum is more than 15 mm Hg.Close the main steam isolation valve after switching off the

machine.Maintain inlet steam pressure constant at rated value.Check the presence of octyl alcohol and corrosion inhibitor

periodically.Analyse chilled and hot / cooling water every three months and

maintain the quality of chilled and hot / cooling water.Ensure that hot / cooling water flow stops one minute after the

stopping the machine.

Change the vacuum pump oil, if it is contaminated (white mistycolour) .

Charge nitrogen gas upto 0.3 kg/cm2(g) in the system for long

shutdown of the machine (i.e more than a month). If theshutdown is for a shorter period, purge the machine for 20minutes, twice a week.

Ensure that the rated electric supply (3 phase) is available.Always start the chilled water pump first and then the hot / cooling

water pump. Ensure that the rated chilled water and hot /cooling water flows are passing through the machine.Ensure that the steam is available at rated inlet condition.

Donts Dont open any of the valves of the purge unit without running thevacuum pump.

Dont disturb the setting of any instrument or safety provided on themachine.

Dont put the refrigerant pump switch or the steam control valveoperational switch in MANUAL, during normal operation ofthe machine.

Dont increase the overload setting of any motor, even if theoverload alarm trips.

Do not run the vacuum pump continuously.Do not let the temperature of hot / cooling water fall below 22 deg.C.

Maintain it by stopping the cooling tower fan or bybypassing the cooling water into the cooling tower basin byinstalling a 3 way valve.

Dont decrease the chilled water flow below the specified value.Dont remove the bulb of the antifreeze thermostat from the

thermowell provided. Ensure that the thermowell is alwaysfull of oil.

Dont run the hot / cooling water pump if chilled water pump is notrunning.

Do not by pass or change setting of any safety devices orinstruments


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Preventive Maintenance

IX - 1

Chapter 9


Chapter Objective This chapter details the schedule of the various preventivemaintenance procedures to be carried out. Preventive maintenanceensures best performance and long life of the machine.

Quaterly maintenance

procedures

Following activities are to be carried out every three months -

. Check and record working of all the safeties and their settings .Reset or replace the safety device ,as required.

. Check all the set point values on the control panel .

. Check and record the TRG reading of the absorbent andrefrigerant pump.

. Check and record the current drawn by absorbent, refrigerant andpurge pump.

. Analyse the Lithium bromide solution and maintain the corrosioninhibitor level and alkalinity. Charge corrosion inhibitor, ifrequired. Charge alkali or acid, if required to maintain the

desired parameters of lithium bromide.. Check for the presence of octyl alcohol. Charge octyl alcohol, if

required.. Check and maintain the hot / cooling and chilled water quality.

Annual maintenance

procedures

Following activities are to be carried out once in a year -

. External visual inspection of the machine for any damage. If anysafety device is missing / damaged , replace the same.

. Conduct nitrogen leak test on the machine. If any leak is detected,rectify the leak point.

. Replace all the diaphragms on the diaphragm valves.

. Check for any scaling / slime in the absorber, condenser andevaporator tubes. Carry out the tube cleaning , if required.

. Overhaul the absorbent and refrigerant pump.

. Clean the steam trap on the machine.

. Check and record the working of all the safeties. Reset or replacethe safety device , as required.

. Check all the set point values in the control panel.

. Check and record the insulation resistance.

. Overhaul the purge pump and clean the moisture trap on the purgeline.

. Conduct bubble test on the machine.

. Clean the seat of the steam control valve.

Maintenance for longterm shut downThis section describes the activities to be carried out during thelong-term shut down of the machine .

. Make sure that the steam control valve is closed and there is nocirculation of hot / cooling and chilled water through themachine.

. In case the shutdown is for one week or more, perform either :A. Perform air-purging once a week, to maintain the required

vacuum in the machine.B. If the shutdown is for a period more than three weeks

charge nitrogen gas into the machine upto a positive pressure of0.2 kg/cm

2g. No air-purging required in this case.


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IX - 2

Water circuit preparation

for long term shutdown

Water circuit preparation is done forAbsorber and condenser section andEvaporator section.

Absorber and condenser

section

The absorber and condenser tubes should be kept dry.

. Drain out all the water from the absorber and condenser from thedrain port of the absorber header.

. Carry out tube cleaning to remove any scale or slime in theabsorber and condenser tubes.

. Clean the tubes with water.

. Add anti-corrosion chemicals to water and circulate it in theabsorber and condenser circuit.

. Drain the water from the tubes.

. Dry the inside surface of the tubes.

Evaporator section The evaporator tubes should be kept full with water.

If the machine is located at a site where the ambient temperature

will be below freezing point of water, drain out all the chilled waterand dry the evaporator tubes.


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C*M *** 0010_0 X - 1

Chapter 10

Procedures

Chapter Objective This chapter describes the various procedures to be carried outduring the maintenance of the machine.

List of Procedures Charging solutions (absorbent and refrigerant).

Sampling absorbent.

Measuring absorbent concentration.

Absorbent analysis.

Charging inhibitor (Li2MoO4).

Charging alkali (LiOH).

Charging acid (HBr).

Checking and adding Octyl alcohol.

Charging Nitrogen gas.

Expelling Nitrogen gas.

Bubble test.

Electrical and

Instrumentation

Checking insulation resistance.

Checking safety device operation.


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Chapter 10

X - 2 C*M *** 00 10_0

Me

tho

do

fCharg

ingso

lutionatt

he

bo

ttom

ofthecon

tainer

Ben

dingo

fVacuum

ru

bber

hose

Figure10.1


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Procedures

C*M *** 0010_0 X - 3

Charging solutions

(absorbent and refrigerant)

This section describes the procedure for charging absorbent andrefrigerant into the machine. (See Figure 10.1)

Equipment used . Solution container (absorbent and refrigerant).. Vacuum rubber hose with hose clamps.. Copper tube

Procedure(to be carried out when

the machine is off)

. Place solution containers near the service valve to be used forcharging.

. Operate the vacuum pump and ensure vacuum level of35mmHg(abs) or less inside the machine.

. Clean the equipment.

. Connect the equipment as shown in the figure.

. Fill the rubber tube with distilled water to avoid air ingress into themachine.

. Insert the copper tube on the end of the vacuum rubber hose into.the liquid container (keep the end of the copper tube slightlyabove the bottom of the container)

. Open the service valve using the slot in the cap.

. When solution starts being sucked into the machine, watch

carefully to ensure that air does not leak into the machine.. As the container starts becomes empty, tilt it so that air does not

enter the tube as shown in the figure.. Before the container become fully empty, bend the rubber vacuum

hose with both hands to ensure that air does not leak in,and quickly insert it into the next container.

. Repeat the above steps till all the solution has been charged intothe machine.

. Once the required amount of solution has been charged, close theservice valve.

. Remove the rubber vacuum hose from the service valve and putthe cap back on the service valve.

. Stop the vacuum pump.

. Wash all the equipment with water and store carefully.

Precautions . When charging solution, be careful to prevent spillage.. Because vacuum exists inside the machine, be careful to prevent

air leaking in during the above work.. Carefully wash the hose used in the above work with water so as

to prevent dirt ingress.. Wear rubber gloves (Do not handle equipment or solution with

bare hands.) and thoroughly wash off any absorbent whichgets on hands, skin or clothes. Take care to preventabsorbent entering the eyes or mouth.

. If any absorbent should spill, thoroughly wash it off with water.


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Chapter 10

X - 4 C*M *** 00 10_0

Sam

pling

Too

l

Vacuum

Manome

ter

Manua

lpurge

va

lve

No.1

Serv

iceva

lve

Purge

Chec

k

va

lve

Purgepump

Purge

Tan

k

Samp

ling

Too

l

Manua

lpurge

va

lve

No.3

Manua

lpurge

va

lve

No.2

Figure10.2


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Procedures

C*M *** 0010_0 X - 5

Method of sampling

absorbent

This section describes the procedure for sampling small amounts ofabsorbent.(See figure 10.2)

Equipment used . Sampling Tool.. Rubber hoses for vacuum with hose clamp.

Procedure . Operate purge pump.

. Open manual air-purge valve No.1.

. Check vacuum less than 4mmHg

. Connect the sampling tool to the service valve on the purgesystem as shown in figure.

. Open up the service valve connected to the sampling tool.

. Open up the service valve of the sampling tool.

. When pressure drops below 4mmHg, close service valve of thesampling tool.

. Close the service valve of the purge system connected to thesampling tool.

. Close Manual purge valve No.1.

. Remove the sampling tool from the purge system.

. Connect the sampling tool to the service valve from which sample

is to be extracted as shown in figure (ensure that the samplingbottle is held tilted downwards).

. Open the service valve of the sampling tool.

. Open the service valve from which sample is to be extracted.

. When sampling flask becomes full of the sample (find by feelingthe temperature near the mouth)

. Close the service valve from which sample was extracted.

. Remove the sampling tool, open the cap and transfer the contentsas required.

. Wash all equipment with water before reuse.

. Upon completion, refit caps and gasket on all service valves.

. Purge the machine for 15 minutes after sampling is over.

. Stop purge pump.

Precautions Vacuum exists inside the machine. Take care to ensure that airdoes not leak into the machine.Handle all valves carefully so as not to damage them.Carefully wash equipment and rubber hose with water to removedirt before using it in the above work.Do not discard the solution after measurement. Store it in an emptybottle and when it becomes full recharge the solution into themachine. (See procedure for charging solution )

Measuring absorbent This section explains the procedure to measure the concentration ofabsorbent and refrigerant. (See Figure 10.3)


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Chapter 10

X - 6 C*M *** 00 10_0

concentration.

Equipment used . Sampling cylinder. Gravimeter (Scale of 1.6 to 1.8 for absorbent and 1.0 to 1.2 for

refrigerant).. Thermometer. Concentration Diagram of Lithium Bromide Solution (Figure 10.4)

. Absorbent or refrigerant (solution to be checked)

Procedure . Take sample of solution to be checked (Refer method of sampling).. Fill sampling cylinder to about 80% with solution to be checked.. Maintain sampling cylinder vertical and insert the thermometer into

the cylinder and stir the solution thoroughly.. When the temperature stabilizes, read the indication on the

thermometer.. Remove the thermometer and insert gravimeter.. When the gravimeter stops moving up and down, read the

indication on the scale.. Remove the gravimeter from the measuring cylinder.. Store the solution in an empty bottle.

. Read the concentration of Lithium Bromide Solution, using theConcentration Diagram (Figure 10.4).

. Upon completion of measurement, wash the gravimeter,thermometer, and sampling cylinder with water, and then storethem carefully.

Example In the concentration diagram the horizontal axis representstemperature and the vertical axis specific gravity. The lines goingdown from left to right represent fixed concentration. If the specificgravity is 1.76 and the temperature is 60C, the concentration givenby the point of intersection of lines projected from these valves willbe 63.0%.

Precautions Do not damage the gravimeter and thermometer.Do not spill any solution.Do not fill the sampling cylinder more than about 80%.Perform specific gravity and temperature measurements quickly.

601.76

1.75

Figure 10.3


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Procedures

C*M *** 0010_0 X - 7

0

1.95

94

93

92

91

1.90

89

88

87

86

85

84

83

82

81

1.80

79

78

76

75

74

73

72

71

1.70

69

68

67

65

64

63

62

61

1.60

59

58

57

56

55

54

53

52

51

1.50

06

16

18

19

1.20

17

11

13

14

15

12

08

09

110

07

03

04

05

01

02

98

99

100

96

97

095

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE (C)

TEMPERATURE (C)

170160150140130120 180

7060 9080 100 110

302010 40 50

.49

.48

1.47

.44

.45

1.43

.46

SPE

CIFI

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GRA

VITY

CON

CENTRATI

ON

(\)

CON

CENTRATI

ON

(\)

LITHIUM

CONCENTRATION DIAGRAM OF

LITHIUM BROMIDE SOLUTION

77

66

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

0

1

2

4

6

8

10

12

14

16

18

20

22

Figure 10.4


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Chapter 10

X - 8 C*M *** 00 10_0

Absorbent (LiBr)

Analysis

Analysis of the absorbent solution is done to determine the following

. Concentration of inhibitor (Lithium Molybdate).

. Alkalinity of the solution.

. Copper concentration.

. Iron concentration.

Standard values Inhibitor 50 ~ 300ppm

Alkalinity 0.03N ~ 0.07NCopper 20 ppm maximumIron 10 ppm maximum

Concentration of

inhibitor

The concentration of the Lithium Molybdate can be checked by"Atomic Absorption Spectrochemical Analysis". A sample of theabsorbent solution made in following procedure is to be sent to alaboratory for analysis.

If the concentration of Lithium Molybdate is less than the standardrefer to procedure for adding inhibitor.

Procedure This procedure decides the sequence for preparing the sample for

checking the concentration of inhibitor. Take solution sample (Refer solution sampling procedure).. Pour the solution sample into a bottle.. Stand the bottle for about 24 hours. After 24 hours, solids will

settle at the bottom of the bottle. Collect 5ml of absorbent solution from the top of the bottle by the

pipette.. Pour the absorbent solution by above work into the beaker.. Mix 4ml of Aluminum nitrate and 1ml of 50% Hydrochloric acid

solution in another bottle.. Add 1ml of solution made above into the beaker by another

pipette.. Pour 94ml of pure water into the beaker by the burette.

Total quantity of the solution in the beaker is 100ml.This means thatabsorbent solution is diluted to 1/20.

Send this sample for inhibitor analysis.Before sampling, It is recommended to perform Decrystallisation

cycle for 8 hours.

Alkalinity of the solution Analysis of Alkalinity is done by phenolphthalein and acid titrationmethod.

Standard Concentration of the alkalinity : 0.03 N ~ 0.07 N

Procedure . Take solution sample (Refer solution sampling procedure).. Pour the solution sample into a bottle.. A sample of absorbent is allowed to stand in a bottle for about 24

hours to decant the solution. (After 24 hours, solids willsettle at the bottom of the bottle.)

. Take 10 ml of absorbent solution from the top of the bottle using apipette.

. Pour the sample absorbent solution into a beaker.

. Pour 50 ml of pure water into the beaker.

. Add Phenolphthalein (2~3 drops) into the beaker. (Absorbentsolution turns pink).

.Add N/10 Hydrochloric acid (HCl) solution drop by drop into theabsorbent solution using a burette till the absorbent solutionbecomes colourless

.Calculate the Alkalinity using the following formulaN = A x 0.01

Where N: Alkalinity of the sample.A : Quantity of HCl acid solution added (ml)


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Procedures

C*M *** 0010_0 X - 9

Action to be taken based on the alkalinity result (adding chemicals)

a. Alkalinity is 0.03 N~0.07 N: No addition.b. Alkalinity is less than 0.03 N : Add LiOH.c. Alkalinity is more than 0.07 N : Add HBr

Refer to the procedure for adding LiOH or HBr. as applicable.

Concentration of Copperand Iron.

The concentration of Copper and Iron can be checked by "AtomicAbsorption Spectrochemical Analysis". A sample of the absorbentsolution is to be sent to a laboratory for analysis.

Standard of concentration of the All Copper : 20 ppm maximumStandard of concentration of the All Iron : 10 ppm maximum

If concentration of the Copper and Iron are more than the standardvalves, absorbent solution in the machine is to be filtered. Pleasecontact service company.

Procedure This procedure decides the sequence for preparing the sample foranalysing the concentration of all Copper and all Iron. Take solution sample (Refer solution sampling procedure).. Pour the solution sample into a bottle.. Shake the bottle before collecting the absorbent solution.. Collect 1ml of absorbent solution from the top of the bottle by the

pipette.. Pour the absorbent solution by above work into the beaker.. Add 1ml of N/10 Hydrochloric acid solution into the beaker by

another pipette.. Pour 98ml of pure water into the beaker by the burette.Total quantity of the solution in the beaker is 100ml.This means thatabsorbent solution is diluted to 1/100.

Send this sample for analysis.

Note In case that crystallization of the absorbent solution occurs,decrystallise the machine and carry out the above procedures.In case that all Copper and all Iron are analyzed, wait for a whileafter adding HCl solution into the absorbent solution.


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Chapter 10

X - 10 C*M *** 00 10_0

Adding Inhibitor This section describes the procedure to add inhibitor into themachine to prevent corrosion.Target concentration of inhibitor : 300 ppm

Equipment used . Inhibitor : Li2MoO4 H2O (20 w% solution). Container

. Rubber gloves. Pure water (DM water/Distilled water)

. Vacuum rubber hose.

. Copper tube

. Hose clips.

Procedure . Contact the service company for dosage of Inhibitor.. Put pure water into the rubber hose and replace the air it with the

pure water.. Connect the rubber hose to the refrigerant service valve using the

hose clip and push the copper tube into the other end of therubber hose and secure it with a hose clip.

. Pour inhibitor into a container.

. Put on rubber gloves.. Insert the copper tube on the end of the vacuum rubber hose intothe inhibitor container.

. Perform air purging from the shell side of VAM.

. Open up the refrigerant service valve.

. When solution starts being sucked into the machine, watchcarefully to ensure that air does not leak into the machine.

. Close the service valve after completely charging the calculatedamount of inhibitor.

. Remove the rubber hose.

. Place the cap on service valve after checking the packing inside.

. Wash the equipment with water.

. Perform refrigerant blow-down twice or thrice after these

procedures are completed to circulate the inhibitor in themachine.

. Perform air purging from the shell side of VAM for 30 minutes aftercompletion of the above steps.

Precautions Carry out this procedure while the machine operates.Wear rubber gloves while working.Thoroughly wash off any inhibitor which gets on hands, skin and

clothes. Take care to prevent inhibitor entering the mouth.Don't spill inhibitor on the floor.

All excess quantities of the solutions and waste fluids are to bedisposed properly as per local laws and regulations.

In case that machine is operated for 18 hours or more per day, add

650 cc of inhibitor ( Li2MoO4 H2O, 20 w% solution) every twomonths in spite of analyzing result of inhibitor.


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Procedures

C*M *** 0010_0 X - 11

Adding Alkali (LiOH) This section describes the method of adding Lithium Hydroxide(LiOH) into the machine when the measured alkalinity is less than0.03N.

Equipment used . Solution container 25 litre capacity

. LiOH powder.. Rubber gloves

. Pure water (DM water/Distilled water)

. Vacuum rubber hose.

. Copper tube

. Hose clips

Procedure . Contact service company for dosage and method of addingalkali - LiOH.

. Perform air purging from the shell side of VAM continuouslythroughout the process.

. After completing the process, Remove the rubber hose and washthe inlet port of service valves with water.

. Replace the cap on the service

Documents

O&M_Seimens_D.E