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ANALYSERS COMMISSIONING REPORT purging

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ANALYSERS COMMISSIONING REPORT purging Powered By Docstoc
					CASE STUDY ON ANALYTICAL INSTRUMENTS
             (ANALYSERS)




                  BY
            VINAY KUHIKAR
        SR. MANAGER, TSX, PSWR




   BHARAT HEAVY ELECTRICALS LIMITED
     POWER SECTOR WESTERN REGION

                                       1
                                   CONTENTS




                                                   NO. OF   PAGE
SL. NO.                  DESCRIPTION
                                                   PAGES     NO.
  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), Nitrogen dioxide
(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                        OXIDES OF NITROGEN                    SUSPENDED PA RTICULATE
                               (SO2)                                  (NO2)                       MATTER     (SPM )
Time Weighted        Annual        24 hours                 Annual       24 hours                 Annual       24 hours
Average              Average *     average **               Average *    Average **               Average *    Average **
Industrial A rea     80 ug/m3      120 ug/ m3               80 ug/m3     120 ug/ m3               360 ug/ m3   500 ug/ m3

Residential     60 ug/m3                 80 ug/m3           60 ug/m3           80 ug/m3           140 ug/ m3          200 ug/ m3
Rural and other
Area

Sensitive Area       15 ug/m3            30 ug/m3           15 ug/m3           30 ug/m3           70 ug/m3            100 ug/ m3

Method of            Improved            Ultrav iolet       Jacab and          Gas phase          High volu me
Measurement          West and            fluorescence       Hocheiser          Chemilu mio        sampling
                     Gaeke                                  modified           ne scence          (Average
                     methods                                (Na-A rsenite                         flow rate not
                                                            methods)                              less than 1.1
                                                                                                  m3/ 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/Nm³ 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)º´³ 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
                                                                                                                                              3
   verify the performance of the equipment as per supplier’s guarantee. 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 Analyser
Main 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.
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 JB’s
14. Air Conditioner – for keeping the ambient temperature inside the panel around 26  C 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 the
detector, 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
                                                                                                    4
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 against H2O
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 1.0 Ton
AC installed on it for maintaining the ambient temperature inside the panel.
During Operation of Flue Gas Analyser, the allowable ambient temperature range must be kept
(5…45C), otherwise the measuring accuracy might not be as high as specified.

LOCATION DETAILS

The installation location should be free of mechanical oscillation and vibration. Especially low
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 analyser is 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.
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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 ra nge end value of the
corresponding measuring component.

STANDARD LIST OF CALIBRATION GAS CYLINDERS

1.   Zero Gas: 100% N 2 in a 10 liters C.S. Cylinder
2.   1600-1800 ppm of SO 2 balance N 2 in a 10 liters Al. Cylinder
3.   200-225 ppm of CO balance N 2 in a 10 liters Al. Cylinder
4.   800-900 ppm of NO balance N 2 in a 10 liters Al. Cylinder
5.   O2 Zero Gas: 2 % O 2 balance N 2 in a 10 liters C.S. Cylinder
6.   O2 Span Gas: 18 % O 2 balance N 2 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 gas cylinder.
   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 “SO 2 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. SO 2 / 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
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the system. This is made possible 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 be checked
       for its specification and its Test Certificate must be requested from the 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 per vendor
       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 Include
   a. 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.
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     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.
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 observed that 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 various
locations 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.
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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, relative to air. Because of the high
operating temperature of the cell, combustible gases that are 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.



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6. DUST / OPACITY MONITOR

INTRODUCTION

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
beam’s 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 monitor automatically
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: 417
2. 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 Unit’s 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 unit consist 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.
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 from temperature 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.


                                                                                                            12
PH ANALYSER

pH is the negative logarithm of the hydrogen ion activity and measure of the acidity, or alkalinity 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 is
balanced 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

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.


                                                                                                              13
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 sample conditioning. 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 pr oportional
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 online monitoring 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.


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
                                                                                                           14
measurement is insufficient for the analysis of phosphate concentration in the low 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 a thin
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

Hydrazine is one of the most common water treatment chemicals used on modern
boiler houses. But dosing too mush is an expensive waste, while too little leads to
equipment damage. Polymetron Hydrastat analysers are designed for accurate on -
line monit oring 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 platinum electrode – 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.

                                                                                                             15
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. Passes through 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 electrode’s 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, pH
Makeup DM Water               Conductivity (Mho), pH
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 (5…45C), 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.



                                                                                                          16
    General Specification of Analyser

SN Descriptions          Model No. Range              Type        Accuracy Sample               Typical
O.                                                                          Flow                Dimensions
                                                                            rate
1     pH Transmitters 9135      0 - 14 pH     2 relay contacts    +/- 0.01 10~15                144x144x150(D)
                                                                  pH        LPH
2     Conductivity    9125      0-100 uS/cm   2 relay contacts    +/- 0.01% 10~15               144x144x150(D)
      Transmitter                                                           LPH
3     Dissolved       9182      0-2000 ppb O2 2 relay contacts    +/- 0.5   10~15               144x144x150(D)
      Oxygen Analyser                                             ppb       LPH
4     Silica Analyser 9097      0-1000 ppb    2 relay contacts    +/- 2 ppb 1~5 LPH             890x485x290(D)
5     Hydrazine       Hydrastat 0-500 ppb     Amperometric        +/- 2 ppb 10~12               300x1000x212(D)
      Analyser        9186                                                  LPH
6     Sodium Analyser Sodimat   0-01 ppb ~    Microprocessor      <5%       3-5                 485x890x285(D)
                      9073      10000 ppm     based Ion selective           LPH
7     Phosphate       Phosphama 0-10 ppm      Microprocessor      0.2 ppm 3 - 5                 483x746x290 (D)
      Analyser        t 8892                  based                         LPH
8     Chlorine        Chloromat 0-5 Mg/L      Microprocessor      ----      3-5                 ---
      Analyser        9184                    based                         LPH
9     Chloride        1517-A1 0-500 ppb       Ion selective       ---       50                  1180x300x130(D)
      Analyser        (Orion)                                               Ml/Min

    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


    SWAS Do’s And Don’ts
    Do’s
       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

    Don’ts
       1. Don’t disturb the settings of Pressure regulator, temperature switch, pressure switch and safety valve
           without consulting service Engineer.
       2. Don’t stop the coolant supply, before isolating the sample supply.
       3. Don’t 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.
                                                                                                             17
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.
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




                                                                                                        18
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 Set
          i.   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

PRECAUTIONS

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 reversible feature.
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 dire ct
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



                                                                                                        19
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 soft
    abrasive (N400 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 hydrochloric acid 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.
                                                                                                         20
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.
   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 will cause
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.



                                                                                                              21
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)

   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 cooling water
    allowed to blow through allowing the sediments to be ejected.
   Do regularly tighten the flanges bolts to ensure leak tightness.
   Don’t 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 failed
2. 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

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




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