Case Study=[Analytical Instruments] [Power Industry] [BHEL(PSWR)]

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    CASE STUDY ON ANALYTICAL INSTRUMENTS

    (ANALYSERS)

    BY

    VINAY KUHIKAR

    SR. MANAGER, TSX, PSWR

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    BHARAT HEAVY ELECTRICALS LIMITED

    POWER SECTOR WESTERN REGION

    CONTENTS

    SL. NO. DESCRIPTION NO. OFPAGES

    PAGENO.

    1.0 COVER SHEET 01 01

    2.0 CONTENTS 01 02

    3.0 INTRODUCTION 01 03

    4.0 FLUE GAS ANALYSERS 05 04 - 08

    5.0 OXYGEN ANALYSERS 02 08 - 09

    6.0 DUST / OPACITY MONITOR 02 10 - 11

    7.0 STEAM AND WATER ANALYSIS SYSTEM (SWAS) 11 12 - 22

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    3. INTRODUCTION

    "Air pollution" is the presence in the atmosphere of one or more contaminants in sufficient

    quantities and of such characteristics and duration as to be injurious to human, plant, or

    animal life, to health, or to property, or to unreasonably interfere with the enjoyment of life or

    property.

    The pollutants monitored in Power plants Flue gas are Sulphur dioxide (SO2), Nitrogendioxide (NO2), Carbon Monoxide (CO) and Suspended Particulate Matter (SPM).

    POLLUTION CONTROL BOARD NORMS

    National Ambient Air Quality Standards:

    1. The level of air quality necessary with an adequate margin of safety, to protect the public

    health, vegetation and property.

    2. Whenever and wherever two consecutives values exceeds the limit specified below for the

    respective category, it would be considered adequate reason to institute regular/continuous

    monitoring and further investigations.

    POLLUTANT SULPHUR DIOXIDE

    (SO2)

    OXIDES OF NITROGEN

    (NO2)

    SUSPENDED PARTICULATE

    MATTER (SPM)

    Time Weighted

    Average

    Annual

    Average *

    24 hours

    average **

    Annual

    Average *

    24 hours

    Average **

    Annual

    Average *

    24 hours

    Average **

    Industrial Area

    Residential

    Rural and otherArea

    Sensitive Area

    80 ug/m3

    60 ug/m3

    15 ug/m3

    120 ug/m3

    80 ug/m3

    30 ug/m3

    80 ug/m3

    60 ug/m3

    15 ug/m3

    120 ug/m3

    80 ug/m3

    30 ug/m3

    360 ug/m3

    140 ug/m3

    70 ug/m3

    500 ug/m3

    200 ug/m3

    100 ug/m3

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    Method ofMeasurement

    ImprovedWest and

    Gaekemethods

    Ultravioletfluorescence

    Jacab andHocheiser

    modified(Na-Arsenite

    methods)

    Gas phaseChemilumio

    ne scence

    High volumesampling

    (Averageflow rate not

    less than 1.1m3/minute)

    * Annual Arithmetic Mean of minimum 104 measurements in a year taken twice a week 24-hourly at uniform interval.

    ** 24-hourly/8-hourly values should be met 98% of the time in a year. However 2% of the time, it may exceeded but not two

    consecutive days.

    For coal based power plants, emission standard for particulate matter is 350 & 150

    mg/Nm for the power plants having capacity less than 200/210 MW and more than

    200/210 MW respectively. Gaseous emissions are controlled through dispersion at

    adequate heights. The stack height requirements for different capacities of power plants

    are as follows:

    Capacity Stack Height

    Less than 200/210 MW H=14(Q) Where Q is SO2 emission Kg/Hr.

    200/210 MW to 500 MW: 220 Mtrs.

    More than 500 MW: 275 Mtrs.

    Concentration based standards for gaseous pollutants are not in existence for coal based

    power plants. However as and when it is required, the monitoring of those pollutants may

    be conducted following the methodology as suggested in CPCB (Central Pollution Control

    Board) publication namely Emission Regulation Part III

    CPCB does not have any guidelines or suggest methodology for verifying Flue gas

    analyser systems. It is up to buyer or user to procure these equipments as per their

    requirement. However, for valuation of performance of these equipments generally

    Calibration gas is used to verify the performance of the equipment as per suppliersguarantee. In case of particulate matter, the performance of Opacity meter / continuous

    monitoring equipment may be verified by manual isokinetic monitoring.

    Flue Gas Analysers are required for the monitoring of Air Quality of Flue gases coming out of

    Power Plant Boiler Chimney.

    Flue gas analyser measures flue gases - Its probes are placed in chimney at required height or

    appliance exhaust and level of Oxygen (O2), Carbon Monoxide (CO), Carbon Dioxide (CO2),

    etc and flue gas temperatures are recorded. If the CO level in the flue of a gas appliance is

    above 100ppm (parts per million) then an investigation must take place. For oil or coal fired

    appliances the CO should not be above 200ppm.

    Equally, Oxygen (O2) levels should be in the region of 3-5% for gas appliances and 5 - 8%for oil & solid fuel appliances - Any other levels suggests an inefficient use of energy,

    wasting fuel and money, or a potentially unsafe situation where too much CO is created

    through oxygen deficiency

    4. Flue Gas AnalyserMain components of this system are:

    1. Flue Gas Analyser for measuring the quantity of SO2, NO & CO.

    2. Flue Gas Sample Probe for collecting Flue gas sample from Chimney inlet.

    3. Heated Flue Gas Sample line for transporting Flue gas sample from probe to Analyser.

    4. Sample Gas Cooler for cooling of Flue gas sample to remove moisture.5. NO2/NO Converter converts NO2 in Flue gas sample to NO for Analyser analysis.

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    6. Diaphragm Pump for sucking the Flue gas sample from probe to Analyser.

    7. Peristaltic Pump for removing condensed water form the cooler drain.

    8. Sample handling system consisting of Solenoids, valves, filters, etc.

    9. Programmable Logic Controller (PLC) for logic programming of Purge cycle.

    10. Power supply source 24 VDC Power supply for PLC

    11. Oxygen Analyser for measuring the quantity of O2 in Flue gas.12. O2 Probe (Zirconium) for collecting & conditioning of Flue gas sample from Chimney

    inlet.

    13. Power supply MCB and alarm JBs

    14. Air Conditioner for keeping the ambient temperature inside the panel around 26C so

    that electronic equipments like PLC and Analysers can funtion properly.

    15. Certified Calibration Gas cylinders of SO2, NO, CO, N2 & O2 (Span & Zero).

    OPERATING PRINCIPLES

    FLUE GAS ANALYSER

    Flue gas analyser is for continuous measurement of IR components, including H2O for cross

    sensitivity correction. It measures gas components with NDIR measuring system. It measures

    all components simultaneously. The time that analyser needs to determine all measuring

    values once depends on the number of measuring components and the physical measuring

    range. Typical time: 5 20 Sec.

    A wide band infrared radiation is emitted by a non-metallic, high stability source. For each

    measured gas this radiation is routed alternatively through an interferential filter, a cuvette

    filled with nitrogen and a filter, and a cuvette filled with high partial pressure of the gas to be

    analyzed.

    A suitable optical system drives the IR radiation inside the analysis chamber and then to thedetector, which receives and amplifies alternatively the two signals: one is the measure and

    the other is the reference. The gas concentration is proportional to the difference of the two

    signals. Gases which may have a cross sensitivity with the measured gas, generate the same

    variation of the measure and reference signals. Therefore the measure is not affected. The

    wheel that holds the cuvettes and filters rotates at 3000 r.p.m. The sensor can acquire 50

    measures each time one of the cuvettes is in front of the I.R. source. A high quantity of

    measures is available. They must be amplified and computed, having a very high precision

    and stability.

    Two microprocessors connected via a dual ram are used. With this approach no measures are

    lost and the instrument can manage all functions.

    Due to physical reasons, the NDIR measuring principle has a certain cross-sensitivity againstH2O when measuring SO2 or NO. The measuring system cannot be optimized for both

    measuring components, as it is when only one component is measured. As a result, the H2O

    cross-sensitivity is higher when simultaneously measuring SO2 and NO. Therefore this

    analyser additionally determines the actual H2O concentration in the sample gas and

    compensates the cross-sensitivities arithmetically with this measured H2O value.

    Three different test gases can be used to calibrate the sensitivities (Spans).

    INSTALLATION DETAILS

    The Flue gas analyser panel is generally installed inside or nearby Chimney. Panel have 1.0Ton AC installed on it for maintaining the ambient temperature inside the panel.

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    During Operation of Flue Gas Analyser, the allowable ambient temperature range must be

    kept (545C), otherwise the measuring accuracy might not be as high as specified.

    LOCATION DETAILS

    The installation location should be free of mechanical oscillation and vibration. Especiallylow frequency vibration for example, caused by road traffic or heavy machinery can

    disturb the measuring operation. Please avoid exposing the analyser to direct sunlight. It must

    be installed / mounted horizontally. An extreme case inclination would interfere with the

    accuracy of the flowmeter.

    RECOMMENDATION

    The gas analysis instrument is part of a measuring system. In order to ensure that the analysis

    is trouble-free, that it requires a minimum of maintenance and produces good analysis data, it

    is necessary to set up the whole measuring system logically. The correct choice of the point of

    gas removal, the devices for preparing the sample gas and careful installation are as crucial to

    the success of measurement as the analyser itself.

    The Sample gas probe is installed on the gas duct before Chimney

    CALIBRATION

    Why is calibration necessary for Gas Analysers?

    The characteristics of optical and electronic components slightly change in the course of

    operation. These changes affect a high-precision measuring system and results in small

    changes of the measuring results. This effect is known as Drift. To compensate drift, a gas

    analyser must be regularly calibrated. In a calibration, the measurement result of the analyseris checked with the Certified Calibration Test Gases, and then the offset from the correct

    NOMINAL value is adjusted to bring the analyser back to the true reading.

    The two important parameters in the measuring system are:

    1. The Zero point: defined as the reaction of the instrument when the component of interest

    (measuring component) is not present.

    2. The sensitivity or span: defined as the reaction of the instrument when the component of

    interest (measuring component) is present.

    There is a Zero point drift and sensitivity drift for each measuring component. Each must be

    determined and corrected independently.

    Calibration gas standards are invaluable in ensuring exact results.

    Zero gas: The Zero Gas is used to calibrate the zero points of all measuring components.

    The Zero Gas must NOT contain any of the measuring components. As a rule Nitrogen can

    be used for the Zero Gas, either Technical of Top grade depending on the application.

    Test Gases: The Test Gases are used to calibrate sensitivities. A test gas is a mixture of Zero

    gas and one or more measuring components.

    Nominal values of the test gases

    The nominal values are the actual concentration of the measuring components in the test gas.

    The nominal values should be within 60 to 100 % of the physical measuring range end valueof the corresponding measuring component.

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    STANDARD LIST OF CALIBRATION GAS CYLINDERS

    1. Zero Gas: 100% N2 in a 10 liters C.S. Cylinder

    2. 1600-1800 ppm of SO2 balance N2 in a 10 liters Al. Cylinder

    3. 200-225 ppm of CO balance N2 in a 10 liters Al. Cylinder4. 800-900 ppm of NO balance N2 in a 10 liters Al. Cylinder

    5. O2 Zero Gas: 2 % O2 balance N2 in a 10 liters C.S. Cylinder

    6. O2 Span Gas: 18 % O2balance N2 in a 10 liters C.S. Cylinder

    CERTIFICATES

    1. Concentration and Stability Certificates for Calibration Gas Cylinders of SO2, NO, CO,

    N2 & O2 (Span & Zero) gas is required. The validity of these certificates is specified by

    Calibration gas filling agency. Gas Validity may be for 6 or 12 months depending upon

    the type of gas and its concentration.

    2. Vendor provides Chief Controller of Explosives Certificate for each Calibration gascylinder. These certificates are useful document for refilling of calibration gas cylinders.

    PROBLEMS ENCOUNTERED AND RESOLVED

    Flue gas sample line choking is the biggest problem in Thermal Power Plant Flue Gas

    analyser system. Ceramic Flue gas sample probe filter also gets choked frequently due to

    accumulation of fly ash and gas condensation. Most of the time the Instrument air purging

    cycle is ineffective in clearing the sample line choking. Another reason for improper air

    purging is failure of PLC controls. 24 VDC Power supply is required for PLC operation. This

    is provided by 24 VDC Power supply module having input 230 VAC. Improper slope of Flue

    gas sample line also result in gas sample condensation in line. Some time Flue Gas Sample

    Probe internals (filter & holding spring) was also found eroded and broken. The insufficient

    heating capacity of Heat Tracing line is also responsible for moisture condensation in sample

    line. At temperature less SO2 dew point moisture condenses to form Aserol (sticky powder).

    Over the period of few weeks this substance blocks the sample line. We have observed the

    choking of Flue gas sample cooler due to Ice formation in sample line if setting and wiring of

    potentiometer wire of temperature control circuit is not done properly. SO2 / NOx / CO

    readings become unstable due to insufficient flue gas sample flow. The condensed water from

    cooler drain needs to be drained without allowing air ingress into the system. This is madepossible by using Peristaltic pump. The low rating pump initially provided was not able to

    drain all the water at faster rate. This resulted in accumulation of water in cooler and sample

    line inside the Analyser cabinet. The outer covering of the Electrically heated hose, which was

    kept in rolled form, got melted at overlap point within one week of its operation. Poor

    response of Vendors for attending to system problems and insufficient supply of

    commissioning spares may leads to the total system failure.

    COMMISSIONING FEEDBACKS

    The Ceramic filter in the Flue gas sample probe is for fly ash removal. It should bechecked for its specification and its Test Certificate must be requested from the

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    Vendor. Extra Filter needed to be installed in sample line for the removal of very fine

    fly ash.

    Some times Flue gas sample line needed to be cleaned to remove choking, it can be

    done by using high-pressure hand operated pump.

    The Flue Gas Sample Probe casing must have heat-tracing wound on it. This is to

    avoid the flue gas sample condensation in probe.

    Peristaltic Pump operation should be checked as per the actual requirement. This

    pump must remove all the condensed water in cooler. If required higher capacity

    pump can be installed.

    It is necessary to check the setting of Heat tracing Thermostat. By installing RTD in

    the sample line we can monitor the temperature of Flue gas sample.

    Flue gas sample line (with heat tracing) must be installed with proper slope to

    avoiding moisture condensation in sample line.

    Timing of Air purging cycle must be adjusted so as to avoid frequent choking of Flue

    Gas Probe filter.

    The installation of electrically heated Teflon hose (if provided) must be done as pervendor instruction. It should not be kept in coil form otherwise its outer sheath will

    melt at contact points.

    Reading of O2, SO2, NOx, CO and load should be configured in DCS Trends for

    continuous monitoring of Flue gas analyser system.

    Certified Calibration gas cylinders validity must be checked before using it for

    Calibration of Analysers.

    SUGGESTIONS

    1. Flue gas sample line between sample Probe and analyzer panel must be purged at regular

    interval with Instrument air along with sample probe purging. For doing this, one solenoid

    valve with instrument air supply to be installed in analyser panel. Sample probe purging

    timer can be used for the operation of this solenoid.

    2. A catch pot should be placed between sample probe and flue gas sample line, just after

    sample probe (near duct) with air operated solenoid drain valve. This drain valve should

    open during gas sample line air purging cycle.

    3. Diaphragm pump should be of high capacity for the suction of Flue gas sample.

    4. The AMC offer shall separately indicate one year annual maintenance contract including

    all the spares, consumables required.

    5. Scope Of Analyser Vendor Should Includea. Necessary rectification / modification in the Analyser system as per site conditions.

    b. Total Commissioning of the system.

    c. Field acceptance of the system by BHEL and Customer.

    d. Handing over the system to Customer O&M with necessary guidelines and spares for

    further Operation and Maintenance.

    e. Annual Maintenance Contract (AMC) for Analysers. (During BHEL one year

    Warranty period)

    f. Refilling of Certified calibration gas cylinders.

    DOCUMENTS REQUIRED FOR COMMISSIONING OF FLUE GAS ANALYSERS

    1. Installation and commissioning procedure of Flue Gas Analyser.

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    2. OGA drawing (Location Drawing) of Flue gas analyser panel in Power plant.

    3. Heat tracing route drawing.

    4. Heat tracing Instruction Manual.

    5. PLC O&M and Instruction Manual.

    6. Write-up for the Routine Maintenance

    7. List of Mandatory spares for Flue Gas Analyser system.8. Concentration and Stability Certificates Certificate and Chief Controller of Explosives

    Certificate of calibration gas cylinder of N2, SO2, NOX, O2 (Span gas), O2 (Zero gas)

    and CO.

    MODIFICATION DONE FOR BETTER OPERATION OF SYSTEM

    It was found that the moisture content in the flue gas is high because of Soot blowing in boiler

    at the rate of 2 hours per shift. The slope of sample line was not sufficient to drain the excess

    moisture from the sample line. It was jointly decided by vendor, Customer and BHEL Site

    Engineer in consultation with EDn Bangalore Design Engineer to modify / re-route the Flue

    gas sample lines to avoid moisture condensation. After above modification it was observedthat the moisture condensation is not taking place in sample line.

    5. OXYGEN ANALYSER

    INTRODUCTION

    Oxygen Analyser measure oxygen concentrations in boiler with the help of probes located at variouslocations in boiler. The zirconia method eliminates the need for sampling equipment, is easy to install,

    provides quick response and stable display, and is easy to maintain. The probe is attached to a terminal

    block. The lead wire, which is directly connected to the internal electric pole, and cell heater are

    contained within the probe. Therefore there is no contact with the direct exhaust gases. The

    measurement range, output signal, and calibration gas concentration can easily be changed.

    OPERATING PRINCIPLES

    OXYGEN ANALYSER

    The working element of the gas sensor is a closed-end tube made of a ceramic oxide,

    Zirconium Oxide (Zirconia). When it is hot (temperatures that exceed 600 C) it becomes a

    conductor of electricity because of the mobility of the Oxygen ions in its crystal structure.

    Electrodes of porous platinum are coated onto the inside and outside of the cell and connected

    to the measurement circuitry.

    When the sensing cell is hot, a voltage is produced that is logarithmically proportional to the

    ratio of the oxygen concentration of the gas on the reference side of the cell (usually ambient

    air) and the oxygen concentration of the sample. If the oxygen in one gas is known (the

    reference gas is normally air 20.9 % O2), the oxygen of the other gas is indicated directly by

    the voltage from the cell. The sensing cell does not produce a signal when air is on both

    sides, and the voltage increases as the oxygen concentration in the sample diminishes, relativeto air. Because of the high operating temperature of the cell, combustible gases that are

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    present may burn, when this occurs, the cell will generate a higher than expected millivolts

    and cause the display to indicate less oxygen than is actually in the gas.

    INSTALLATION LOCATION

    Probe locations of Oxygen Analysers in boiler are generally as follows:

    1. Economiser Outlet- (Left): 01 No.

    2. Economiser Outlet - (Middle): 01 No.

    3. Economiser Outlet - (Right): 01 No.

    4. Air PreHeater-A Outlet: 01 No.

    5. Air PreHeater-B Outlet: 01 No.

    COMMISSIONING PROCEDURE, CALIBRATION

    Commissioning procedure will be as given in Instruction Manual of Oxygen Analyser Calibration can

    be carried out with O2 Span (8.0 %) and Zero (0.4 %) gas for all Oxygen Analysers.

    CERTIFICATE & CALIBRATION ACCESSORIES

    1. Oxygen Gas concentration and stability Certificates

    2. Chief Controller of Explosives Certificate

    3. Certified calibration Oxygen gas cylinder for Unit 3 & 4.The details of Calibration Oxygen

    cylinders are as follows:

    Zero Gas: 0.4 % O2 balance N2 in a 10 ltrs C.S. Cylinder (SGC18375, SGC18397): 02

    Nos.

    Span Gas: 8.0 % O2 balance N2 in a 10 ltrs C.S. Cylinder (SGC18387, SGC18371): 02

    Nos.

    PROBLEMS ENCOUNTERED AND RESOLVED

    Electronics module of Oxygen analyser got defective. Vendor representative repaired it at site.

    6. DUST / OPACITY MONITOR

    INTRODUCTION

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    The Opacity Monitor is used for continuous opacity or dust monitoring of flue gas in stacks and

    ductwork.

    A opacity monitors give vital analysis of pollutant particulate emission levels and provide a primary

    indicator of overall boiler efficiency.

    Opacity measures the percentage of absorbed light. An advantage of opacity is that the measuring

    devices need not be calibrated. A disadvantage is that the results vary with the location of the monitor

    itself. However, the results can be recalculated for the distance from the monitor to the stack emission

    outlet. The influences of the color, shape, and surface structure of the dust particles are not taken into

    account, shown in the non-linear relationship between dust load and opacity. For example, opacity

    increases only about 15% when the dust load is doubled in the upper measurement ranges.

    Measurements can be displayed as opacity or optical density.

    The extinction (optical density) has a linear relationship to the dust load because it is calculated

    logarithmically: doubling the dust load results in a doubled measurement. A calibration curve is

    calculated for the measuring location according to VDI 2066 or EPA CFR 40 Part 60 #5 with the

    extinction coefficient k. Under normal operating conditions, however, the same dust load can lead to

    different readings depending on grain size and flow distribution, so the uncertainty ranges are also

    calculated.

    OPERATING PRINCIPLE

    Operating Principle: Cross-stack double pass transmissometer

    The beam transmissometer measures the fraction of light, from a

    collimated light source, reaching a light detector a set distance away.

    Light, which is absorbed or scattered by the media, between the

    source and the detector does not reach the detector. The fraction of

    light received is converted to the beam attenuation coefficient

    (usually called "c") by the formula c = ln(T)/z where T is the fraction

    of light transmitted and z is the path length of the instrument. The

    exact relationship varies with the type of particles present.The measuring system is based on the single pass/dual path-

    architecture, illustrated by the enclosed picture.

    Method - I

    The laser beam sent by the laser unit crosses the measuring section

    only once and the receiver unit measures and evaluates the laser

    beams weakening caused by dust content. Additionally the laser unit

    sends the reference signal around the stack via optical fibre to the

    receiver unit, 40 times per second. This system improves the long-

    term accuracy of the analyser, because in traditional analysers with a

    dual-pass design, the retro-reflector is excluded from the zero/span calibration. The optical reference

    path around the stack ensures that all affected surfaces are included in the calibration. The monitorautomatically corrects for dirt that can accumulate on these surfaces.

    Method - II

    Opacity monitor operates on the auto-collimation (double-pass) principle. The light beam crosses the

    measurement path twice and the system measures the light attenuation from dust in the stack. A

    photoelement alternately reads the measurement beam and a comparison light beam 2 minutes to

    insure accuracy. Since one joint amplifier is used for both the measuring and comparison light beams,

    temperature fluctuations and long-term amplifier drift are automatically compensated. The system

    generates light internally with the Super wideband Light Source to prevent distortions from sunlight or

    other sources. The broad spectrum of emitted light means results are not distorted by temperature. This

    ensures a more stable measurement than a conventional narrow band LED.

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    INSTALLATION DETAILS, LOCATION, RECOMMENDATION

    System alignment is performed using a direct view alignment port

    built into the light source optics. The retro reflector also contains a

    built in alignment port, to align the retro reflector. Alignment of

    both opacity monitor light source and reflector is critical for

    accurate off stack zeroing of opacity monitors.

    COMMISSIONING PROCEDURE & CALIBRATION

    Zero and span calibrations are performed hourly and timed for

    continuous stack sampling with no monitor down time. Calibration

    drift is automatically compensated for and we report the

    information daily on user-selected outputs. The hourly system calibrations assure minimal erroneous

    data collection. Dirty window compensation is corrected hourly and we display a visual alarm on the

    operator panel if the correction limit is exceeded.

    TYIPICAL CONFIGURATION DATA OF DUST / OPACITY MONITOR (LAND Model 4500)

    UNIT TYPE = MKII AVG TIME = 01 MIN PLCP = 0.500

    MODE = DUST DUST_CAL = BLK AVG DUST GAIN = 110

    DUST BKGD = 0.000 ALERT = 0.00 mg/m3 ALARM = 800 mg/m3

    ALRT DELAY = 10 SEC ALRM DELAY = 15 SEC O.D. = 3.00

    CAL. EVERY = 24 HRS OUTPUT 1 = I DUST OUTPUT 2 = I DUST

    RANGE 1 = 1000 mgm RANGE 2 = 1000 mgm OUT 1 = 4 - 20 mA

    OUT 2 = 4 - 40 mA LINE FREQ = 50 HZ S/W VER = 3.12

    CAL IN = 6:00 BAUD RATE = 9600 INPUT RANGE = 4 - 20 Ma

    Passwords:

    1. For changing TYPE and O.D: 4172. For normal calibration check: 10

    3. For Input Current calibration: 27

    PROBLEMS ENCOUNTERED AND RESOLVED

    1. Display on LCU of Opacity/Dust Monitor not visible on both the units.

    2. Opacity/Dust Monitor Blower found burnt and needed rewinding. It was repaired twice.

    3. Transceiver units found faulty and cannot be repaired at site and need to be taken at vendor

    Service center.

    Following items serviced by vendor at their works and reinstalled at site:

    Transceiver unit of Unit #3 (Location: Flue gas duct): 01 No

    LCU of Unit # 3 (Location: LCU JB): 01 No

    Micro P.C.B of Unit # 4 (Location: inside transceiver): 01 No

    Control P.C.B of Unit # 4 (Location: inside transceiver): 01 No

    4. Constant Over range reading in Dust Monitor was due to loose current loop connector.

    5. CRU Units Range and Dust gain could not be set due to program error. Hence, the CRU unit has

    been bypassed and mA output has directly been connected to Control Room Panel.

    6. BHEL Ranipet did not give opacity versus Dust level curve.

    7. Calibration Check was not operational because of faulty calibration motor.

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    7. STEAM & WATER ANALYSIS SYSTEM (SWAS)

    INTRODUCTION

    We understand that within power stations the aim of water and steam analysis is to minimize

    contamination of the circuit, thereby reducing corrosion as well as the risk of the formation of harmful

    impurities and operation costs. Whether it's water or steam, we need accurate control of pH

    & conductivity in our process. Errors can lead to costly equipment damage or wasted time &

    materials. The purity of Boiler Feed Water and Steam is absolutely crucial in turbine applications.

    To prevent costly plant shutdowns due to scaling and corrosion, over two dozen steam and water

    samples have been taken to measure pH, Conductivity, Dissolved Oxygen, Silica, Sodium and

    Hydrazine. These samples can be as hot as 560 C, with pressures up to 250 bars. SWAS system is

    for Conditioning and Analysing steam / water sample at elevated temperatures and pressures. For each

    Analysers there are single line units, pre-piped to include all necessary elements required to reduce

    temperature and pressure of hot samples, so that they can be safely handled and analyzed. Each unitconsist of a Sample cooler, Pressure regulator, Isolating and regulating valves for sample and coolant,

    indicators for temperature, pressure and flow, as well as necessary tubing and fittings.

    SWAS generally consists of following Analysers:

    1. PH Analyser(example 9135 - ZELLWEGER ANALYTICS,Polymetron make )

    2. Conductivity Analyser(example 9125 - ZELLWEGER ANALYTICS,Polymetron make)

    3. Silica Analyser(example 9097 - ZELLWEGER ANALYTICS,Polymetron make)

    4. Dissolved Oxygen Analyser(example 9182 - ZELLWEGER ANALYTICS,Polymetron make)

    5. Sodium Analyser(example SODIMAT 9073 - ZELLWEGER ANALYTICS,Polymetron make)

    6. Phosphate Analyser (example PHOSPHAMAT 8892 - ZELLWEGER ANALYTICS,Polymetron

    make)

    7. Chlorine Analyser(example CHLOROMAT 9184 - ZELLWEGER ANALYTICS,Polymetron make)8. Hydrazine Analyser (example HYDRASTAT 9186 ZELLWEGER ANALYTICS,Polymetron

    make)

    9. Chloride Analyser(example MODEL 1517 ORION make)

    OPERATING PRINCIPLE

    SWAS ANALYSER PANEL

    The sample is tapped from the process stream and fed to the system through a 1 OD line. A bulkhead

    connector is provided at the sample inlet point. The sample reaches the sample cooler after passing

    through an isolating valve, which may be high pressure or low-pressure quality depending upon the

    service.

    The Sample cooler is coil in shell type construction and can operate under severe operating conditions.

    There could be one or two sample coolers in series depending upon the total heat load in the sample

    stream.

    The coolant enters the sample cooler from the coolant header, fills the shell and goes back to the return

    header. The shell is protected from excessive pressure, which may arise due to accidental rupture of

    sample coil by means of a relief valve. The flow indicator is provided to check the coolant flow in the

    coolant lines.

    The sample than passes through a sample filter, which removes any suspended matter from the sample

    to the pressure regulator, which brings the outlet pressure down to a set level.

    A relief valve is also built-in with the pressure regulator, which may be set to blow off at preset

    pressure, thus protecting the down stream apparatus.

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    After pressure reduction, the conditioned sample is taken in a header where its temperature and

    pressure is monitored. Temperature and Pressure gauges are provided for this purpose. The Analysers

    that are fed by this system operate under temperature and pressure that are very low (Typically 2 to 3

    Kg/sqcm & 30 to 40 C). Thus it is essential to protect them from over temperature or over pressure

    conditions, which would damage the instruments. The temperature and pressure switches are fitted

    into SWAS as safety precautions to prevent such system failure. The switches receive a signal fromtemperature and pressure sensor mounted on the header and operate solenoid valve, which blows the

    sample down in case of over temperature or over pressure condition.

    The sample than goes to respective Analysers through Rotameters. Adjusting the regulating valve

    provided with the Rotameter regulates the flow rate.

    PH ANALYSER

    pH is the negative logarithm of the hydrogen ion activity and measure of the acidity, oralkalinity of a solution. pH = - log10 [aH+]

    pH is normally measured using a glass electrode and a reference electrode. the

    glass electrode acts as a transducer, converting chemical energy (the hydrogen

    activity) into an electrical energy (measured in millivolts). The reaction isbalanced and the electrical circuit is completed by the flow of ions from the

    reference solution to the solution under test.

    The electrode and reference solution together develop a voltage (emf) whose

    magnitude depends on the type of reference electrode, the internal construction

    of the glass electrode, the pH of the solution and the temperature of the solution.

    For every unit change in pH (or decade change in ion concentration), the emf of

    the electrode pair changes by 59.16 mV at 25 Deg C. This value is known as the

    Nernstian slope of the electrode.

    The pH electrode pair is calibrated using solutions of known and constant hydrogen ion concentration,

    called buffer solutions. The buffer solutions are used to calibrate both the electrode isopotential and

    slope.

    CONDUCTIVITY ANALYSER

    Measuring the conductivity of the liquids has become an increasingly important quality control tool

    for the process industries where it is often used to indicate a change in the process rather than an

    absolute analysis. In other words, unlike ion selective measurements, the total quantity of ions present

    in the solution is measured, rather than the type of ions itself.

    The conductivity of a liquid is somewhat similar to that of an electric current flowing though a metal

    when a voltage is applied. The main difference, however, is that in a metal conductor the current flows

    by transport of electrons, whereas in a liquid, it flows by transport of ions. It follows that the greater

    the numbers of ions present in the liquid, the higher is the transport of charges per unit time and hence

    the conductance of the liquid. In effect it is the inverse of electrical resistance and the unit of

    measurement is Mho.

    The electrolytic conductivity of a liquid (sometimes called its conductance per cm or m) is dependent

    on the concentration of the liquid, (i.e the number of available ions), as well as the valency and

    mobility of the ions and the degree of dissociation of the electrolyte.

    The mobility of the ions is itself dependent on the temperature of the solution, so that at constant

    temperature, the conductivity is directly related to concentration. Typical industrial applications for

    conductivity measurement include water purity, Boiler Feed water protection, check on water hardness

    and boiler blow down control. The conductivity measurement of pure water is a special case, since the

    specific conductivity of pure water relates to the sum of the specific conductivity

    values of all the salts present and the dissociated H+ and OH- ions.

    SILICA ANALYSER

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    Polymetron Silkostats Silica Analysers offer online monitoring of low-level silica in pure sample

    water and steam. Soluble silica reacts with ammonium molybdate to form a yellow-coloured

    silicomolybdate complex. The latter may be reduced, by means of a suitable reducing agent, to the

    strongly blue-coloured molybdenumblue complex:

    Photometric analysis of silica by measurement of molybdenumblue is substantially more sensitive

    than the assay via the yellow silicomolybdate complex. The formation of molybdenum blue is strongly dependent upon the solution pH, the type and

    amount of reducing agent, as well as various other factors. It is important, therefore, that the

    instructions for the preparation of the reagents and the method are strictly adhered to.

    Phosphates, analogous to silicates, are also capable of producing yellow phosphomolybdate

    complexes and, in the presence of reducing agents, molybdenumblue. It is possible, within limits,

    to suppress this interference by judiciously adding oxalic acid.

    In order to assure optimum turbine performance, continuous monitoring of silica in superheated steam,

    boiler water and feed water is of utmost importance.

    DISSOLVED OXYGEN ANALYSER

    The measurement of dissolved oxygen is based on the Clark cell principle. An oxygen-permeable

    membrane isolates the electrodes from the sample water, thus obviating the need for sampleconditioning. Other reducible or oxidisable ions do not interfere, because they cannot pass through the

    gas-permeable membrane. A constant voltage supply powers two electrodes, maintaining each at a

    constant potential. A gold working electrode (cathode) reduces the dissolved oxygen to hydroxyl ions:

    O2 + 2H2O + 4e- => 4OH-

    A large silver counter electrode (anode) provides the oxidation reaction, which occurs on its surface:

    4Ag+ + 4Br- => 4AgBr + 4e-

    The reduction of oxygen is the current limiting reaction, thus making the cell current linearity

    proportional to the dissolved oxygen concentration.

    Electrochemical reactions and diffusion rates are temperature sensitive. The measuring cell, therefore,

    is equipped with a temperature sensor, which allows automatic temperature compensation.

    Technical characteristic

    Sample:

    Temperature: 0 to 45 Deg C. Working pressure: Atmospheric pressure

    Flow rate: 4 to 10 liter/hr

    Material:

    Working electrode: Cathode: gold Counter electrode: Anode: silver

    Membrane holder: Noryl Membrane: PFA

    Transmitter: Aluminium + polyester Probe body: Noryl

    SODIUM ANALYSER

    Modern high-pressure power plants require highly pure Feedwater. Polymetron Sodimats offer onlinemonitoring of low-level sodium in ultra pure water and steam.

    The measurement is based on a direct potentiometric technique using a highly sensitive sodium glass

    electrode. The sodium glass electrode is placed in a sample which has been previously conditioned to a

    pH > 10. Sample conditioning is necessary because sodium glass electrodes are not perfectly specific

    sensors, but are subject to interference by ions, especially ions H+. Low level sodium measurement,

    therefore, require that the H+ of the sample water be adjusted to a level several orders of magnitude

    below the level of sodium. The difference of potential between the glass electrode and the reference

    electrode is directly proportional to the sodium concentration. Sodium cations and anions are always

    linked. Most cations have a corrosive influence in water and vapor cooling circuits. Because of this

    chemical link between sodium ions and anions, sodium measurement presents particularly important

    risks of corrosion and other effects.

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    PHOSPHATE ANALYSER

    It uses photometric analysis to monitor the levels of phosphates in water.

    Orthophosphate reacts with ammonium molybdate to form a yellow-coloured

    phosphomolybdate complex. The latter may be reduced, be means of a suitable reducing agent, to the

    strongly blue coloured molybdenum blue complex. Photometric analysis of phosphates by

    measurement of molybdenumblue is substantially more sensitive than the

    assay via. the yellow phosphamolybdate complex.

    The formation of molybdenumblue is strongly dependent upon the solution

    pH, the type and the amount of reducing agent, as well as various other

    factors. It is important, therefore the instructions for the preparation of the

    reagents and the method are strictly adhered

    Ammoniumolybdate reacts with orthophosphate. The rate of reaction of this

    complex formation is practically instantaneous. Direct photometric assay of

    the yellow complex is possible, in principle, but the sensitivity of the

    measurement is insufficient for the analysis of phosphate concentration in thelow ppm range. for this reason, the phosphamolybdate is reduced with ferrous

    ions to the much more sensitive molybdenumblue.

    Note:

    1. Ferrous iron solution is particularly suitable as a reducing agent because of its stability against

    oxidation by air, as well as its fast rate of reaction with phosphomolybdate.

    2. A high sample-to-reagent ration minimizes errors arising as a result of inaccuracies of the reagent

    delivery rate.

    Its principal application is phosphate analysis in Boiler Feed water, Steam generation, etc. Boilers

    operating at medium to low pressures frequently utilize sodium phosphates for alkalization (pH 9

    10), and prevent the formation of residual water hardness scale in the steam generating components.

    CHLORINE ANALYSER

    Polymetron Chloromat Analysers were designed for the on line monitoring of Chlorine levels in

    water circuits. The Chloromats feature controlled potential amperometry

    and a self-cleaning working electrode system.

    Active chlorine measure lies on the Clark cell principle.

    The Sensor amperometric type is composed of:

    one gold working electrode, where the main reaction occurs.

    one silver counter electrode, which is also used as reference electrode.

    a potassium chloride based electrode.

    one microporous membrane selective to HOCl

    The HOCl molecules contained in the sample diffuse through the membrane. HOCl is then located in athin electrolyte layer, between the membrane and the cathode. A constant working potential is applied

    to the working electrode (cathode) where HOCl is reduced: HOCl + H + 2e- => Cl + H2O

    At silver electrode (anode), silver is oxidised into Ag+ ions which then percipitate with the chloride

    ions

    2Cl + 2Ag => 2AgCl + 2e-

    HOCl reduction at the cathode generates a current directly proportional to its

    concentration.

    The electrochemical reaction and the diffusion through the membrane depend on

    temperature. The measuring cell is therefore equipped with a temperature sensor

    which enables to operate an automatic compensation of the measurement.

    HYDRAZINE ANALYSER

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    Hydrazine is one of the most common water treatment chemicals used on modern boiler houses. Butdosing too mush is an expensive waste, while too little leads to equipment damage. PolymetronHydrastat analysers are designed for accurate on-line monitoring of hydrazine levels in water samples.

    This analyser continuously measures the amount of dissolved hydrazine and onter oxygen reducers in

    water. The measuring principle is based on the electrochemical method of 3-electrode amperometry.

    A polarization voltage (+ 480 mV) is applied between a platinum anode (working electrode) and a

    stainless steel cathode (counter-electrode). Hydrazine is oxidized at the surface of the platinumelectrode working electrode and the resulting current is directly proportional to the hydrazine

    concentration in the range of 0 to 500 ppb N2H4.

    The reaction is enhanced in the alkaline environment, sample is conditioned at pH = 10.2 adding

    diethylamine or disopropylamine through a Venturi tube, before the sample enters the measuring cell.

    Compensation of the temperature effect is achived through a semiconductor sensor integrated to the

    measuring cell.

    The chemical reaction is

    (1) N2H4 + 4OH => N2+4H2O + 4e-

    The anode-cathode torque potential is kept constant par rapport with respect to a third electrode

    (reference electrode, Ag/AgCl). The system avoids interference effects interference effects resulting

    from the variations of water composition that appear when using the 2-electrode system.

    At + 480 mV, the cell current is linearly proportional to the Hydrazine Concentration.

    CHLORIDE ANALYSER

    The sample stream enters the Low Chloride Monitor and passes through a sample bypass valve, which

    allows excess sample to be diverted to a waste drain. Bypassing excess sample to drain allows the

    analyser to respond more quickly the changes in sample chloride concentration, especially where there

    is a long sample line prior to the analyser. Sample is filtered to remove particulate matter to prevent

    the clogging of analyser. Enters a pressure regulator and a flow meter / needle

    valve assembly to ensure a constant pressure and flow rate in the Analyser.

    Passes through the three way solenoid valve and then either flows through or

    bypasses a deionization cartridge before being cooled down to 5 C. Passesthrough the reagent diffusion bottle where pH adjustment takes place. Reagent

    consumption is held at a constant level because sample temperature is

    maintained at 5 C. Re-cooled to 5 C 0.1 C, eliminating the need for

    temperature compensation due to varying sample temperatures. Sample is than

    passed from the chloride or measuring electrode, whose voltage output varies

    with changes in chloride concentration. It passes by the reference electrode. The reference electrode

    maintains the fixed voltage output when in contact with the sample. the combined chloride and

    reference electrode voltage outputs are amplified and displayed. Sample is than drained into

    atmosphere.

    Note: The Reference electrodes position is downstream of the chloride electrode to avoid chloride

    contamination of the sample from the reference electrode filling solution.

    INSTALLATION DETAILS, LOCATION, RECOMMENDATION

    ANALYSERS INSTALLED FOR:

    Boiler Drum Conductivity (Mho), pH, SiO2 (ppb), PO4 (ppm)

    Saturated steam Conductivity (Mho), pH

    Superheated Steam Cation Conductivity (Mho), pH, Conductivity (Mho), SiO2 (ppb)

    Feed water DO2 (ppb), pH, Conductivity (Mho), N2H4(ppb)

    Condensate Water Sodium (ppb), pH, Conductivity (Mho), SiO2 (ppb), Cation

    Conductivity (Mho), Chloride (ppb)

    Deaerator DO2, pHMakeup DM Water Conductivity (Mho), pH

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    Condensate Cooling Water Chlorine (ppb)

    Hotwell Conductivity (Mho) - Right side, Conductivity (Mho) - Left side

    LOCATION

    DRY PANEL: All SWAS Analysers are mounted in this panel. During Operation of SWAS Analysers

    in Dry panel, the allowable ambient temperature range must be kept (545C), otherwise the

    measuring accuracy might not be as high as specified. In other words Air-conditioning required. The

    installation location should be free of mechanical oscillation and vibration. Please avoid exposing the

    analyser to direct sunlight. It must be installed /mounted horizontally.

    WET PANEL: This entire panel must be located near to Dry panel. All Sample coolers, Pressure

    regulator, Isolating and regulating valves for sample and coolant, indicators for temperature, pressure

    and flow, temperature switches, as well as necessary tubing and fittings are mounted in this panel. It

    does not require Air-conditioning but installation location should be free of mechanical oscillation and

    vibration.

    Typically following nos. of each type of Analysers may be required in each Unit

    PH Analysers: 07 Nos. Conductivity Analysers: 08 Nos.Silica Analysers: 03 Nos. Dissolved Oxygen Analysers: 03 Nos.

    Sodium Analyser: 01 No. Phosphate Analyser: 01 No.

    Chlorine Analyser: 01 No. Hydrazine Analyser: 01 No.

    General Specification of Analyser

    Applicable for all Analysers

    Power Supply 230 V AC, 50 Hz

    Moniotor Enclosure IP65

    Ambient Temperature 5 - 55 Deg C

    Output signal 2x4~20 mA

    SN

    O.

    Descriptions Model No. Range Type Accuracy Sample

    Flow

    rate

    Typical

    Dimensions

    1 pH Transmitters 9135 0 - 14 pH 2 relay contacts +/- 0.01

    pH

    10~15

    LPH

    144x144x150(D)

    2 Conductivity

    Transmitter

    9125 0-100 uS/cm 2 relay contacts +/- 0.01% 10~15

    LPH

    144x144x150(D)

    3 Dissolved

    Oxygen Analyser

    9182 0-2000 ppb O2 2 relay contacts +/- 0.5

    ppb

    10~15

    LPH

    144x144x150(D)

    4 Silica Analyser 9097 0-1000 ppb 2 relay contacts +/- 2 ppb 1~5 LPH 890x485x290(D)

    5 Hydrazine

    Analyser

    Hydrastat

    9186

    0-500 ppb Amperometric +/- 2 ppb 10~12

    LPH

    300x1000x212(D)

    6 Sodium Analyser Sodimat

    9073

    0-01 ppb ~

    10000 ppm

    Microprocessor

    based Ion selective

    < 5 % 3 - 5

    LPH

    485x890x285(D)

    7 PhosphateAnalyser

    Phosphamat 8892

    0-10 ppm Microprocessor based

    0.2 ppm 3 - 5LPH

    483x746x290 (D)

    8 Chlorine

    Analyser

    Chloromat

    9184

    0-5 Mg/L Microprocessor

    based

    ---- 3 - 5

    LPH

    ---

    9 Chloride

    Analyser

    1517-A1

    (Orion)

    0-500 ppb Ion selective --- 50

    Ml/Min

    1180x300x130(D)

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    SWAS Dos And Donts

    Dos

    1. Always keep the coolants flowing, even if sample is stopped.

    1. Check the wiring for the possible loose connections.

    2. Always flush all the Sample / Coolant lines before starting operation.

    3. Ensure that sufficient differential pressure exists in coolant inlet and outlet header (Typical

    Minimum 2.5 Kg/sqcm)

    4. Check for leaks in both sample and coolant lines.

    5. Check whether the connections to valves / pressure regulator / Flow indicators etc are in right

    direction.

    6. Always switch Off the mains power supply while carrying out any maintenance on the system

    Donts

    1. Dont disturb the settings of Pressure regulator, temperature switch, pressure switch and safety

    valve without consulting service Engineer.

    2. Dont stop the coolant supply, before isolating the sample supply.

    3. Dont carry any maintenance function without isolating the sample supply.

    COMMISSIONING OF SWAS

    1. All samples to be made available in Wet and dry panel as per requirement.

    2. After commissioning and calibration of all Analysers, daily readings may be jointly recorded

    atleast for one month along with Customer chemist in the Observation sheets. Readings to be

    made available in DCS (MAX).

    3. Alarms to be commissioned

    4. Insulation of Chiller water lines to be done properly.

    5. Operation of chiller to be ensured

    6. BHEL site to handed over the required chemicals for 12 months for the operation of Silica,

    Phosphate, sodium, Hydrazine Analysers to customer

    Major highlights of SWAS MOM with Customer during Handing over of SWAS:

    1. Date of handing over to be mentioned clearly.

    2. List of Chemicals and other consumables with quantity to mentioned.

    3. Handing over of all Manual and Procedures (including O&M Manuals of all Analysers).

    4. All Normal / routine maintenance jobs involving Instrument re-calibration, fuse replacement,

    leakage found if any will be attended by vendor

    5. Major defects like equipment failure due to design deficiency or manufacturing defect will be

    attended by BHEL during Warranty period. In such case BHEL will make all out effort to rectify

    the defect in shortest possible time.

    TYPICAL CALIBRATION ACCESSORIES OF SWAS

    Box No. 01:

    Chloride analyser calibrator set

    a. Calibrator with 230 V AC charger: 01 No.

    b. Tube set with connector: 01 No.

    c. Syringe: 02 Nos.

    d. Electrode accessories with sand paper: 01 No.

    Box No. 02:

    Chloride analyser calibrator set

    a. Calibrator with 230 V AC charger: 01 No.

    b. Tube set with connector: 01 No.

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    c. Syringe: 02 Nos.

    d. Electrode accessories with sand paper: 01 No.

    Box No. 03:

    Reagent bottles of Chloride with tubes (faulty reagents): 08 Nos.

    Box No. 04:

    Reagent bottles of Chloride with tubes (O.K reagents): 03 Nos.

    Box No. 05:

    a. DO2 kit: 06 Nos.

    b. Oxistat solution bottles: 06 Nos.

    c. Oxistat membrane box (total 14 nos. membrane): 06 nos.

    d. Packing circular SS plates: 06 Nos.

    e. Silica Analyser keys: 02 Nos.

    f. Fuses: 19 Nos.

    g. PVC connectors: 15 Nos.

    Box No. 06:

    a. Chlorine kit: 02 Nos.

    b. Chloromat refilling solution bottles: 03 Nos.

    c. Chlorine membrane box (total 06 membrane): 02 Nos.d. Plastic can cover: 03 Nos.

    Material given to Customer (MSEB) by M/S Forbes Marshall:

    Empty Plastic cans of 10 Liters capacity each for: 12 Nos.

    Storage / Maintenance of Analyser Reagents

    DOCUMENTS & CERTIFICATES

    1. TEST CERTIFICATES for the SWAS wet panel sample line Isolation valves (03 pages)

    2. O&M Manuals of SWAS:

    a. Instruction Manual for PHOSPHAMAT - Model 8892: 03 Nos.

    b. Instruction Manual for SODIMAT Model 9073: 03 Nos.

    c. Instruction Manual for CHLOROMAT Model 9184: 03 Nos.

    d. Instruction Manual for Metering Pump (SWAS): 03 Nos.

    e. O & M Manual for Diamond Chiller (SWAS): 03 Nos.

    f. Instruction Manual for HYDRASTAT Model 9186: 03 Nos.

    g. Instruction Manual for DYNAMIC CALIBRATOR Model 15 DC: 03 Nos.

    h. Instruction Manual for CHLORIDE MONITOR: 10 Nos.

    i. Maintenance Procedure: 03 Seti. Sample Cooler Maintenance:

    ii. SWAS Maintenance

    iii. Sodium Analyser Maintenance

    iv. Hydrazine Analyser Maintenance

    v. Silica Analyser Maintenance

    vi. Phosphate Analyser Maintenance

    vii. DO2 Polishing procedure

    viii. Regeneration procedure of Cation Column

    ix. Instruction for changing over of compressors of chiller unit

    j. O&M Manuals of SOX/NOX/CO Analyser

    k. O&M Manuals of Oxygen Analyser

    PRECAUTIONS20

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    General Precautions

    Replace the calibration solution when the empty alarm is flagged.

    Check the reagents level & replenish after 40 days.

    While making new reagents use de-ionised water which conductivity is < 0.2 s/cm.

    Use the all laboratory utensils of plastic (Not glass). If the plant is under shutdown for more than week, run the analyser with DM water for 2 to 3

    hours.

    MAINTENANCE PROCEDURES

    SILICA ANALYSER

    Periodic: Check reagents solution level & replenish if low

    Monthly: Check for possible dirt deposits in the flow circuit.

    Quarterly: Change pumps tubes, each tube set will last 2x90 days by using the reversiblefeature.Annually: Clean level detector with a soft tissue.

    DISSOLVED OXYGEN ANALYSER

    Approximate membrane lifetime: 6 month depending on the sample

    Cleaning: Clean the instrument with a soft tissue and without any aggressive agent.

    Transmitter:

    The electronic unit amplifies the signal of the amperometric measuring cell and converts it into a

    direct digital readout in ppm, mg/l, g/l, Deg. C, Deg F. The transmitter comprises the following

    items:

    1. Potentiostat which maintains the working electrode potential constant.

    2. Amperometric measuring module.3. Analog multiplexer

    4. Microprocessor

    The analog multiplexer allows measurements to be acquired from the measuring cell, temperature

    sensor and internal checkpoints. Further, the microprocessor operates the relays, the RS485 interface

    (optional) and analog outputs (2 x 4 to 20 mA isolated from input signal, 800 ohms load maximum).

    The unit has a built-in concentration autoranging feature and a microprocessor operated calibration

    routine.

    The output of the Potentiostat is monitored for possible overdrive of the Potentiostat output stage. This

    condition can occur with the connections to the measuring cell open, inoperable electrodes or a

    defective reference electrode.

    Oxygen Electrode Rejuvenation Procedure

    After some months of operation (3 to 12 depending on sample oxygen concentration, plant shut-down

    frequency, etc), a dark AgBr coating may cover part of the silver anode.

    This coating does not affect the measurement until more than 90 % of the surface is contaminated.

    When changing the electrolyte and membrane, visually check the silver anode. If more than 2/3 of the

    surface is covered then electrode rejuvenation according to the following procedure is needed:

    1. Soak the anode in 10 % ammonia for about one hour then rinse it with demineralised water and

    wipe it with a soft cloth.

    2. If the ammonia cleaning is not sufficient, rejuvenation of the silver electrode has to be done by re-

    polishing softly (coating is an only few micron thick) the area covered with silver bromide with

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    soft abrasive (N400 to 600). After polishing, rinse the anode with demineralised water and wipe it

    with a soft cloth.

    Obviously, re-calibration is required.

    SODIUM ANALYSER

    Weekly:

    Check the level of Calibration solution.

    Check the level of conditioning reagents.

    Check the level of electrolyte (KCl)

    Monthly: Check visually the filter cartridge, change or clean

    Half Yearly: Check the flow meter calibration.

    Electrode Reactivation Procedure

    If the sodium selective electrode may loose its sensitivity because of clogging, reactivate electrode

    with following procedure:

    1. Immerse half of the measuring electrode in a de-mineralised solution with 2 % of hydrochloricacid for 5 to 10 Seconds.

    2. Rinse immediately & wash electrode with DM water.

    3. Put the electrode in a KCl 0.1 m solution for a couple of hours before putting it back into the cell.

    PHOSPHATE ANALYSER

    Periodic: Check reagents solution level & replenish if low

    Monthly: Check for possible dirt deposits in the flow circuit.

    Quarterly: Change pump tubes, each tube set will last 2x90 days by using the reversible feature.

    Annually: Clean level detector with a soft tissue.

    HYDRAZINE ANALYSER

    Weekly:

    Check the level of sample conditioner. Replenish if low.

    Check the sample flow rate. Reset to 10 Lt/hr if it has drifted.

    Check the filter for dirt. Replace or clean if flow is impeded.

    Monthly:

    If the platinum electrode is deposited or if this electrode is dirty do not remove it for cleaning, but

    proceed as follows:

    1. Turn off the sample flow needle valve.

    2. Using a syringe, inject 5 % nitric acid into the measuring cell via the venturi-valve inlet

    tubing.

    3. Wait 5 minutes for the acid react.

    4. Turn the sample flow again and set it to 10 Lt/hr

    5. Recalibrate the instrument.

    Half Yearly: Check the flow meter calibration.

    Regeneration Procedure Of Cation Column

    Remove the Cation column, which is exhausted.

    Take 25 ml (36%) HCL in beaker, dilute to 250 ml in water add 1000 ml DM water = 1250 ml.

    Take above solution in 5-liter bucket.

    Add cation resin into above solution; stir well about 30 to 40 minutes.

    Rinse the resin 3 to 4 times by using five-liter DM water every time.

    Fill the resin in to vessel along with DM water.

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    Always keep resin in wet condition by using low conductivity water.

    CHLORIDE ANALYSER

    Daily:

    Ensure that:

    1. Pressure: 15 psi

    2. Flow: 40 ml/min

    3. Level of Reference solution in bottle Not to increase

    4. Level of Reagent in Bottle: Not to increase

    Level in Reagent bottle should not increase more than the available level. If it increases than it

    indicates that there is a leakage in tube inside the bottle.

    Weekly:

    1. All the points of Daily Maintenance.

    2. Chloride Analyser Refrigeration (Chiller) unit water level should be maintained.

    Monthly:

    1. All the points of Weekly Maintenance.

    2. Calibration of the Instrument (chloride Analyser).Three Monthly Maintenance:

    1. All the points of Monthly Maintenance.

    2. Change the Reagent bottle if empty.

    3. Change the Diffusion tube.

    4. Change the Reference Solution bottle if empty.

    Yearly Maintenance:

    1. All the points of 3 monthly Maintenance.

    2. Change the Electrode and De-ionization Cartridge.

    Things to do during Plant Shut Down

    Because leaving reagent bottle on instrument for unit shutdown of ONE DAY or LONGER willcause Chloride Electrode Failure, diffusion tubing breakage, exhaustion of deionization cartridge and

    corrosion in cooling coils.

    1. Change the Reagent Bottle with the bottle filled with DM Water.

    2. Remove both the electrode carefully from the Flow Cell and clean with DM water. Wipe it with

    tissue paper and let them hang by their connectors.

    3. Remove the Reference Solution from the Electrode and rinse clean with DM water. Wipe it with

    tissue paper, as salt will be formed at the Reference junction.

    Low-Level Chloride Monitor (Product Number: 1517)

    Model 1517 Low-Level Chloride Auto Zero Monitor, complete with chloride electrode (100025),

    reference electrode (100031), with one 2-oz. bottle internal filling solution, deionization cartridge(150013), shorting straps (150030), auxiliary cooling unit (60 Hz), and one instruction manual.

    Requires reagent (151711), or consumables kit (151750), and dynamic calibrator (150095).

    Chloride Consumables Kit (Product Number: 151750)

    Chloride 1 Year Consumables Kit, includes four 1-liter bottles reagent with diffusion tubing (151711),

    chloride electrode (100025), reference electrode (100031), with one 2-oz. bottle internal filling

    solution, five 2-oz. bottles reference electrode internal filling solution (150071), deionization cartridge

    (150013), four sets inlet filter (4 x 151720), two 60 micron filters (181170), four sets O-ring kit (4 x

    151735), syringe kit (150096), and one pint chloride standardizing solution (941707).

    SAMPLE COOLER MAINTENANCE (SWAS)

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    Keep the heat transfer surface clean. Brush the internal surface of shell & inner cylinder by steel

    wire to remove scale deposits.

    Check regularly for any clogging of the small bore coil by foreign particles or sediments, specially

    the bottom portion.

    Physically inspect the parts as a good engineering practice.

    During operation, the drain plug provided on the shell can be occasionally opened and coolingwater allowed to blow through allowing the sediments to be ejected.

    Do regularly tighten the flanges bolts to ensure leak tightness.

    Dont ever shut off the cooling water supply before shutting off the steam sampling line. This may

    overheat the coil tube.

    Temperature of Sample line was not being maintained at 175 Deg C as envisaged in system

    PROBLEMS ENCOUNTERED

    1. Chiller Unit for Sample Cooling:

    Motor winding got burnt due to voltage fluctuation in customer Power supply.

    Both Chiller pumps failed2. DM Water Pump:

    DM water pump, which is used to pump the DM water sample to SWAS Wet panel, has failed. It

    was sent to their vendor works for repair

    3. Cooling Water Sample Line:

    This line got choked very frequently due to muddy cooling water.

    4. SWAS Panel:

    SWAS Room layout was changed by vendor at latter date. Due to this the location of wet panel

    and dry panel has also changed. Sensor cable with 4Cx1.5 sqmm and 6Cx1.5 sqmm in 10 meters

    length loose pieces. After change in room layout the sensor cable required between wet panel and

    dry panel were of 20 meter length pieces. New cables were procured.

    5. Dissolved Oxygen Analyser (Dearator Do2 Analyser) Of Unit 4 SWAS System:

    Electrodes silver coating pilled off during calibration in the presence of Vendor representative.6. Hotwell Conductivity Module Failed During Operation:

    Card was replaced by vendor.

    7. Isolation Valves:

    As per the specification the Isolation valves, which came, fitted with SWAS wet panel were not of

    SS316 material. Vendor was informed about the discrepancy and therefore vendor replaced 16

    nos. isolation valves per unit.

    THE END

    Prepared by: Vinay Kuhikar, Sr. Manager, BHEL, PSWR

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