Enzyme, Pharmaceutical Aids, Miscellaneous Last Part of Chapter no 5th.pdf
Steam and power.pptx
1. STEAM AND WATER ANALYSIS
SYSTEM (SWAS)
SUBMITTED BY
PRIYANK MODI
DEPTT. C&I
BLA POWER PVT LTD.
2. Contents
➢Why Required SWAS
➢Sampling Conditioning/ Wet Panel
➢Schematic Diagram of Sample Inlet
➢ Important Equipments of Sample System
➢Sample Analysis
pH Analyzer
Conductivity Analyzer
Silica Analyzer
DO Analyzer
Phosphate Analyzer
➢DO’S & DON’TS
➢CONCLUSION
3. What is the need for boiler water treatment?
• Inhibit corrosion
• Prevent freezing of the water in the system
• Increase the boiling point of the water in the system
• Inhibit the growth of mould and bacteria
• Allow improved leak detection
4. What Happen if You don’t have SWAS
• 50% of forced power plant shutdowns can be attributed to
impurities and other cycle chemistry problems.
• A well designed SWAS package directly attacks these
problems.
• People with good knowledge, experience and expertise prefer
on-line monitoring of all the necessary parameters involved in
plant cycle chemistry.
• You will always find a properly maintained SWAS in all power
plants that are running at 95+ PLF / PAF
5. • Why Required
• In any power plant running on steam, the purity of boiler feed
water and steam is absolutely crucial; especially to steam
turbine, steam boiler, super heater, condenser and other steam
equipment. To prevent damage of steam turbine, steam boiler
and other apparatus due to scaling and corrosion, on line
steam and water analysis of critical parameters such as pH,
Conductivity, Dissolved Oxygen, Silica, Sodium, Phosphate
etc. is a must. The steam can be as hot as 560ºC.The
pressures can be as high as 250 bar. To keep the power plant
up and running, with minimum erosion and corrosion of steam
turbine, steam boiler and condenser.
• To protect these equipments SWAS works in to stages:-
1. Sample Conditioning
2. Sample Analysis
6. 1. Sampling Conditioning or Wet Panel
The Sample is First cooled in Sample Coolers, depressurized in
pressure regulators and then fed to various analyzers while
keeping the flow characteristics constant by means of a Back
Pressure Regulating Device. There are a lots of safety
equipment provided in wet panels, so that the operators feel
safe while working with these systems.
8. SAME OF THE IMPORTANT COMPONENTS OF SAMPLING
SYSTEMS (WET RACK)
1. SAMPLE COOLER
• Sample Coolers are COIL-IN-SHELL type CONTRA-FLOW heat
exchangers.
• Coil Materials are available such as Stainless Steel AISI
316,Monel 400 & Inconel 625 and so on.
9. 2. High Pressure Regulator
• Piston Type High Pressure Regulators. These are used in
primary conditioning where sample pressures are higher
than 100 Kg/cm2.
• As these are piston type Pressure Regulators , there is
no fear of diaphragm rupture etc.
10. 3. Back Pressure Regulator
• Back Pressure Regulator (BRP) to avoid low flow (or
fluctuating flow) conditions to analyzers in the event grab
sample valve operation. In the absence of such a device ,the
sample would flow to grab sample line when the grab sample
valve is opened. This can create low flow alarm conditions in
sample going to analyzers.
• A pressure Regulator and Back Pressure Regulator
combination provides very stable pressure & flow conditions,
thereby ensuring reliable, efficient and accurate analysis.
11. 4. Sight glass
• Sample flow Indicator (sight Glass) to view the sample flow
inside the sample line.
• A rotating wheel indicates presence of cooling water. The sight
glass is made of high grade stainless steel.
12. 5. Sample Filter
• The Filter which is required to ensure particle -free sample.
• Any particle of size up to 40 microns size can be filtered out.
• Forged stainless steel body and hexagonal cap help easy cleaning
of filter element.
13. 6. Pressure Relief Valve
• Pressure relief Valve comes fitted with Sample Cooler.
• Pressure Relief Valve is important as it protects the Sample
Cooler in case the coil fails.
• This is also important for human safety as pressurized cooler
may burst due to full sample pressure under coil failure
conditions.
14. 7. Hi-Temp Isolation Valve
• This valve is an easy to operate & can be used for most high
pressure and temperature applications.
• Its unique plug/seat geometry and stuffing box design allow
these valves to operate for extended period of time without
gland leakage and passing.
15. 8. Cation Column
• The Duplex type Cation Conductivity Column is a field
proven design.
• The Cation Conductivity measurements are considered to be
more reliable than ordinary conductivity measurements
• This ensures Elimination Of Masking Effect of desired
chemicals used in treating the water.
• This provides a more realistic picture of dissolved impurities
in sample
18. General Specification of Analyzers
SNO. Descriptions Model No. Range Accuracy
Sample Flow
rate
1 pH Transmitters SMART Pro 8966 P 0 - 14 pH +/- 0.01 pH 10~15 LPH
2 Conductivity Transmitter SMART Pro 8967 P 0-100 μS/cm +/- 0.01% 10~15 LPH
3
Dissolved Oxygen
Analyzer
Polymetron 9100 0-150 ppb O2 +/- 0.5 ppb 10~15 LPH
4 Silica Analyser Polymetron 9210 0-2000 ppb +/- 2 ppb 1~5 LPH
5 Phosphate Analyzer Polymetron 9211 0-10 ppm 0.2 ppm 3 - 5 LPH
6 Total Dissolved Solids SMART Pro 8969 P 0-10 ppm 0.2 ppm 3 - 5 LPH
19. pH Analyzer
• pH is a measure of the acidity and alkalinity properties of a
water solution, which are determined by the concentration of
hydrogen ions (H+) present in the solution.
• pH is defined as pH=-log10［H+］
20. Why pH Measurement Required
• The steam which goes to the turbine has to be ultra pure.
The pH value of the feed water gives direct indication of
alkalinity or acidity of the water.
• The ultra pure water has pH value of 7.
• In a steam circuit, to keep the pH value of feed water at
slight alkaline levels.
• It helps in preventing the corrosion of pipe work and other
equipment.
• pH Analyzers are recommended at following location in a
steam circuit : high pressure heaters, DM Makeup, CEP
discharge
23. THE MEASUREMENT OF pH (Glass electrode method )
• pH measurement is based on
i) pH sensitive electrode (usually glass),
ii) a reference electrode,
iii) a temperature element
• pH sensitive glass develops a potential (voltage) proportional to the
pH of the solution.
• The reference electrode is designed to maintain a constant potential
at any given temperature.
• The difference in the potentials of the pH and reference electrodes
provides a mill volt signal proportional to pH.
• Most pH sensors are designed to produce a 0 mV signal at 7.0 pH,
with a (theoretically ideal) slope (sensitivity) of -59.16 mV / pH at
25°C.
24. REFERENCE ELECTRODES
• The reference electrode consists of a silver wire(Ag) coated with silver
chloride (AgCl ) in a fill solution of potassium chloride(KCL) .
• The purpose of the potassium chloride (KCL) is to maintain a reproducible
concentration of silver ions(Ag+ ) in the fill solution
25. “Dual point calibration”
1. The flow chart for “Dual point calibration” is shown considering two buffer solutions of
pH 4 and pH 9.
1. Dip the sensor in the buffer solution with pH 4.
1. Press Enter when message “ready” appears on screen.
1. Dip the sensor in the buffer solution with pH 9.
1. Press enter when message “ready” appears on screen.
1. %slope, Zero Offset are shown. Enter the date.
1. These parameters can be seen in future in menu
“Single point calibration”
1. The flow chart also shows “Single point calibration” method, also called as
standardization.
2. In this method the pH value of the solution is measured with the standard pH
instrument
3. The sensor is dipped in this solution, and earlier measured pH value is fed during
calibration
26. How to clean the electrode
The pH electrode is an electro-chemical sensor. When the pH electrode is used, the
junction and glass membrane contaminates because of process fluid. This in turn
increases the sensor response time.
Salt deposits
Immerse the electrode in tap water for 10 to 15 minutes.
The salt dissolves in water.
Rinse the electrode with distilled water.
Oil/Grease film
Use mild detergent and water to gently wash the electrode bulb.
Rinse the electrode tip with distilled water.
Protein deposits
Dip the electrode in a solution prepared as 1% pepsin solution in 0.1M of HCL for 10
min.
Rinse the electrode with distilled water.
Clogged reference junction
Heat diluted KCL solution to 60 to 80 deg C.
Place the sensing part of the electrode into the heated solution for about 10 min.
Allow the electrode to cool in unheated KCL solution.
27. 6.6 Do’s and Don’ts for pH (Glass) electrodes
1. Remove the special transportation seal, Before putting the electrode in process line,
2. Clean the pH electrode under low pressure tap water or any suggested cleaning
solution.
3. Do not touch the diaphragm or tip of the electrode during cleaning.
4. Gently tap dry the tip of the electrode using a clean and soft tissue paper.
5. Do not rub the tissue paper on the electrode as it may generate static charges.
6. Calibrate the transmitter with pH electrode as a system.
If you change/replace transmitter and/or electrode it is necessary to recalibrate as a
system.
7. Keep the electrode wet when not in use.
8. Dip the electrode in 3M KCL solution (or any storage solution as recommended by
manufacturer).
28. Error During Sensor Calibration
Error Message Action
Zero error
This shows that sensor “zero point” is
shifted by more than 1pH units from the ideal
value.
Use the procedures to clean and rehydrate the
bulb. Check again. If the same message repeats
then replace the sensor.
Remedy
Slope error
This shows that sensor “slope” is out
of the normal acceptable slope range 70% to
110%.
Use the procedures to clean and rehydrate the
bulb. Check again. If the same message repeats
then replace the sensor
Remedy
29. How to rehydrate the bulb?
1. Immerse the electrode in pH 4 buffer solution for 10 to 30
minutes.
2. Rinse the electrode with distilled water.
3. Check the response of the electrode.
30. CONDUCTIVITY ANALYZER
• Conductivity is the ability of a solution, a metal or a gas - in brief all
materials - to pass an electric current. In solutions the current is
carried by cation and anions whereas in metals it is carried by
electrons.
• How well a solution conducts electricity depends on a number of
factors
• Concentration
• Mobility of ions
• Valence of ions
• Temperature
31. • Conductivity
Electricity is the flow of electrons. This indicates that
ions in solution will conduct electricity. Conductivity is
the ability of a solution to pass current. The
conductivity reading of a sample will change with
temperature.
κ = G • K
κ = conductivity (S/cm)
G = conductance (S), where G = 1/R
K = cell constant (cm-1)
32. • Conductance
Conductance (G) is defined as the reciprocal of the electrical resistance (R)
of a solution between two electrodes.
G = 1/R (S)
The conductivity meter in fact measures the conductance, and displays the
reading converted into conductivity.
• Cell constant
This is the ratio of the distance (d) between the electrodes to the area
(a) of the electrodes.
K = d/a
K = cell constant (cm-1)
a = effective area of the electrodes (cm2)
d = distance between the electrodes (cm)
34. Sensor Wiring
● The Cable of the conductivity sensor
consist of a screw cap at one end.
● The Four wires on other side are to be
terminated at the transmitters
35.
36. CONDUCTIVITY SENSOR
● 2- pole conductivity sensors are ideal
for pure & ultra pure water
applications.
37. FM 8310/8311/8312 SPECIFICATION
SENSORS FM 8310 / FM 8311 / FM 8312
TYPE 2 Pole cell
CELL CONSTANT K=0.1
CONDUCTIVITY RANGE Up to 20 uS/cm
ELECTRODE CONNECTION ¾ “ NPT(M) or 1.5" TC
TEMPERATURE RATING T max = 80ºC
PRESSURE RATING 6 bar
ELECTRODE MATERIAL SS 316
TEMPERATURE SENSOR Built in Pt 100
CABLE
Integrated 7.5m, 6-wire doubled shielded, open
ended
38. Conductivity Solution
• Conductivity is typically measured in aqueous solutions of
electrolytes.
• Electrolytes are substances containing ions, i.e. solutions of
ionic salts or of compounds that ionize in solution.
• The ions formed in solution are responsible for carrying the
electric current.
• Electrolytes include acids, bases and salts and can be
either strong or weak.
39. How to clean the electrode
● Make sure that conductivity sensor is clean, dry and no deposition is
observed.
● Clean the sensor in case of deposition, clean the electrode with Iso Propyl
Alcohol (IPA) before using.
● If required keep the electrode in IPA overnight
● It recommended to clean the electrode before each calibration.
40. Conductivity values at 25°C
• Pure water 0.055 μS/cm
• Deionised water 1 μS/cm
• Rainwater 50 μS/cm
• Drinking water 500 μS/cm
• Industrial wastewater 5 mS/cm
• Seawater 50 mS/cm
• 1 mol/l NaCl 85 mS/cm
• 1 mol/l HCl 332 mS/cm
41. Why Conductivity Measured
• Conductivity is an important parameter for detecting any
contamination of steam in the boiler circuit.
• Conductivity of pure water is almost zero (1-2 μ Siemens)
• Ingress of any kind of dissolved impurity will raise
conductivity instantly.
• Thus conductivity is an important parameter for the detection
of leakages.
42. Parameters to be Maintained
• 1) Boiler drum water
i) before Cation conductivity between 10 to 30
μS/cm
ii)after Cation conductivity between 5 to15 μS/cm
• 2) Extraction pump discharge
i) after Cation conductivity between 0.1 to0.3
μS/cm
with an alarm value of 0.5 μS/cm
• 3) Economizer inlet
after Cation conductivity between 0.1 to0.3 μS/cm
• 4) Hotwell conductivity between 2 to 4 μS/cm
• 5) Make-up treated water outlet conductivity between 0.02
to0.1 μS/cm with alarm level at 0.2 μS/cm and trip at 0.4 μS/cm
43. Indications of the Problem
• If the conductivity at the make-up treated water outlet goes
a) >0.1 μS/cm stream in service is exhausting
needs to be taken out of service with the other mixed-bed
stream brought into service
• In the case of the hot well, if the conductivity reading is
i) < 2 μS/cm LP dosing failure
ii) > 4 μS/cm over-dosing of LP dosing or condenser
tube leakage
• At the economizer inlet if
the conductivity increases Cation column
exhausting .
44. Conductivity decreasing before the cation column
Probable reasons
• Boiler water tube leakage
• Boiler blowdown is in progress
• Boiler drain valves or blow down valves passing
• Instrument reading wrongly due to fault or loss of sample flow
The corrective action
• Confirm tube leak and dose caustic soda through HP dosing system
and maintain conductivity
• Check drain valves and blowdown valves for any leak and attend
• Check for free flow of sample or rectify instrument if needed
45. Conductivity increasing before the Cation column
Probable reasons
• Condenser tube leakage
• Boiler HP dosing is in progress
• Instrument reading wrongly due to fault or loss of sample flow
The corrective action
• Confirm condenser tube leak and take action to maintain conductivity
till shutting down unit
• Check for free flow of sample or rectify instrument if needed
46. Conductivity decreasing after the Cation column
Probable reasons
• Boiler water tube leakage
• Boiler blowdown is in progress
• Boiler drain valves or blowdown valves passing
The corrective action
• Confirm tube leak, check conductivity before cation column
and dose caustic soda through HP dosing system and
maintain conductivity
• Check drain valves and blow down valves for any leak and
attend
47. Conductivity increasing after the Cation column
Probable reasons
• Condenser tube leakage
• Cation column getting exhausted / exhausted
• Contamination of make-up water from the water treatment plant
• Instrument reading wrongly due to fault or loss of sample flow
The corrective action
• Confirm condenser tube leak and take action to maintain
conductivity till shutting down unit
• Inform chemist regarding increase in conductivity after checking
other possible causes
• Ensure mixed bed and final treated water outlet conductivity
• Check for free flow of sample or rectify instrument if needed
48. Total Dissolved Solids
● Total Dissolved Solids (TDS) are the total amount of mobile
charged ions, including minerals, salts or metals dissolved in a
given volume of water.
Unit :- mg per unit volume of water (mg/L) or PPM
● In general, the total dissolved solids concentration is the sum of
the cation (positively charged) and anions (negatively charged)
ions in the water
● Parts per Million (ppm) is the weight-to-weight ratio of any ion to
water
49. Where Do Dissolved Solids Come From?
● Dissolved solids come from
1)Organic sources :- leaves, silt, plankton, and industrial waste and
sewage
1)Inorganic sources :- Rocks and Air that may contain calcium
bicarbonate, nitrogen, iron phosphorous, sulfur, and other
minerals
1)Note:- The efficacy of water purifications systems in removing
total dissolved solids will be reduced over time,
It is highly recommended to monitor the quality of a filter or
membrane and replace them when required.
50. Deciding on the required boiler water TDS
● The actual dissolved solids concentration at which foaming may start
will vary from boiler to boiler.
● Conventional shell boilers are normally operated with the TDS in the
range of 2 000 ppm for very small boilers, and up to 3 500 ppm for
larger boilers.
51.
52. Calculating the blowdown rate
● The following information is required:
1) Boiler water TDS (PPM)
2) Feed water TDS (PPM)
3) The quantity of steam which the boiler generates, usually
measured in kg / h
Boiler water TDS measurement :-
conductivity (µS / cm) x 0.7 = TDS in parts per million (at 25°C).
F=Feed water TDS (ppm)
S=Steam generation rate (kg / h)
B=Required boiler water TDS (ppm)
53. Closed loop electronic control systems
● These systems measure the boiler water conductivity, compare it with
a set point, and open a blowdown control valve if the TDS level is too
high.
● The actual selection will be dependent upon such factors as boiler
type, boiler pressure, and the quantity of water to be blown down
● The measured value is compared to a set point programmed into the
controller by the user
54. ● The labour-saving advantages of automation.
● Closer control of boiler TDS levels.
● Potential savings from a blowdown heat recovery system (where
installed).
Manual Blowdown Closed loop electronic TDS control
60. Calibration & Commissioning
● Power On the Transmitter
● Calibrate the Temperature sensor with standard Thermometer in
Water at Ambient Temperature.
● Calibrate the sensor with the help of Standard Conductivity Solution.
● Dip The sensor in known conductivity solution
● Solution temperature is Shown 25 Deg C
● Enter The Cell Constant
● Enter the conductivity of the Solution
● Displays Actual Measured Value of Solution
● Check & Set Transmitter Range as required by the Process
● Mount the sensor carefully in Process Pipe
● Set the Flow through the chamber or tank as per requirement.
62. Silica Analyzer
• The Presence of silica in the steam and water circuits of a
power generation plant is associated with a number of problems
both in the Super Heater and Turbine sections.
• The solubility of silica in steam increases with pressure. Hence
there are chances of silica carryover. The Presence of Silica in
the steam can lead to deposition in Superheated tubes and on
Turbine Blades which may lead to loss of efficiency and Turbine
blade Failure.
• Silica in the steam cycle can result in deposition of a “glass”
layer on surfaces, resulting in a loss of thermal process
efficiency.
• Deposition of silica on the turbine blades can result in the
turbine becoming imbalanced, reducing efficiency and, in
extreme cases, causing extensive damage to the turbine.
65. Working principal
1. The 9210 can analyze up to six different samples.
2. Adjustment of the flow is carried out with the help of a needle valve (2)
3. At the beginning of the analysis, the sample is introduced into the measuring
cell (4) with the use of a solenoid valve (5).
4. The reagents R1M and R1A are first added using two of the reagent pumps
(9).
5. The silica contained in the sample then reacts with the molybdate and forms
the silicomolybdic complex.
6. The reaction will take up to 5 minutes. Oxalic acid is then added using a
reagent pump (9) to avoid phosphate interference and to intensify the color.
7. The silicomolybdic complex is reduced to a blue molybdenum complex by
means of ferrous ions
8. A photometric measurement is carried out at the end of the reaction.
66. Specifications
Sample
Number of channels 1 - 6
Measurement cycle < 10 min / channel
Sample pressure 0.2 to 6 bar (3 to 87 psi)
Temperature 5 - 50°C (41 - 122°F)
Sample flow Minimum 5L / hour
Maximum 30L / hour
Analysis
Value measured Dissolved SiO2
Cycle time Approximately 10 minutes per channel
Measurement range 0 - 1000 ppb
Repeatability ± 2% or ± 0.5 ppb
Detection limit 0.5 ppb
Maintenance
Calibration Chemical zero, slope with calibration solution
Reagent consumption Approximately 1L per month and per reagent
Calibration solution consumption Approximately 200 ml / calibration
68. ●Calibration solution :-
● +
DILUTE 100
TIMES
● 2 liters of calibration solution When
DM Silica =0
CONCENTRATE
D SOLUTION
(Use of Titrisol®
(Merck) cartridge )
DM
water
(1 Lit)
2139 mg/lit
of SiO2
10 mL per liter to give a
concentration of 21.39
mg/liter SiO2
69. Connecting the canisters
● Each reagent tubing is labeled individually and delivered already connected
to the analyzer. They are fed through, and attached to, caps that attach to the
reagent canisters
● Connect each cap to its canister:
• Tube R1M to reagent canister labelled R1M: Sodium molybdate
• Tube R1A on reagent canister labelled R1A: Nitric acid
• Tube R2 on reagent canister labelled R2: Oxalic acid
• Tube R3 on reagent canister labelled R3: Sulfuric acid and ferrous ammonium
sulfate
70. Calibration
● Calibrations allow the adjustment of:
• ZERO of the system
• SLOPE of the system
• Both ZERO and SLOPE of the system
1. ZERO calibration is performed chemically by the analyzer. In order to avoid
the use of water free of SiO2, the analyzer carries out a measurement
without a colorimetric reaction .
1. Slope of the system is then calibrated with a standard solution of known
concentration of SiO2.
72. Monitoring Silica for Demineralization
• Demineralization is an effective means of removing
dissolved solids such as silica through the use of anion or
mixed bed ion exchangers. Silica has a very low ionic
strength and it is one of the first ions to break through when
the bed is reaching exhaustion
• For proper working of Turbines, Continuous Monitoring of
Silica is highly recommended.
• In Steam circuit where Silica Analysis is required are :-
1. Low Level Silica Measurement :- HP & LP Turbines,
Drum (Saturated) Steam, CEP Discharge, DM Make up
Water
2. High Level Silica Measurement:- Drum Water
73. Dissolved oxygen
• The DO determination measures the amount of dissolved (or free)
oxygen present in water or wastewater
• At elevated temperature dissolved oxygen causes corrosion which may
cause puncture and failure of piping and components respectively.
• Dissolved oxygen also promotes electrolytic action between dissimilar metals
causing corrosion and leakage at joints and gaskets.
• Mechanical Dearation and chemicals scavengers additives are used top
remove the DO.
• DO monitoring is imperative in power stations using neutral or combined
operating conditions (pH 7.0-7.5 or 8.0-8.5)
• In steam Circuit where DO monitoring is required are Deaerator Inlet and
Outlet (Feed water, Condenser & Deaerator Outlet) .
74. Working principle
The measurement of dissolved oxygen is based on the well
known Clark cell principle.
● An oxygen-permeable membrane isolates the electrodes
from the sample water, thus obviating the need for sample
conditioning
● A gold working electrode (cathode) reduces the dissolved oxygen to
hydroxyl ions:
O2 + 2H2O + 4e- ® 4OHA
● 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 linearly proportional to the dissolved oxygen concentration
● Electrochemical reactions and diffusion rates are temperature-sensitive
75. Main characteristics
● Range 0-2 ppm
● Calibration in the air
● Temperature compensation
● Programmable alarm levels, outputs on relays
● 4-20 mA, 0-20 mA analogue outputs (standard) and RS485
(option)
● Wall- , panel- and tubing mounting
76. Technical characteristics
SAMPLE
Number of channels 1
Temperature 0-45 °C (32-113 °F)
Working pressure Atmospheric pressure
Flow rate 4...10 l/h
MATERIALS
Working electrode Cathode: gold
Counter-electrode Anode: silver
Membrane holder Noryl
Membrane PFA
Probe with optional immersion Stainless steel 316L
OPERATING CONDITIONS
Ambient temperature -20...+60 °C
Relative humidity 10...90 %
Power supply voltage fluctuation ± 10 %
81. Zero Calibration
● Make sure the water used for the chemical zero is really oxygen-free (< 1 ppb).
● Press ENTER, the "CAL" message flashes and indicates the instrument is in
calibrating mode.
● Wait for the current stabilization (approximately 10 min.) and press OK to validate
the calibration.
● The oxygen concentration value flashes during 3 seconds. The instrument displays
zero.
82. SLOPE Calibration
● Humidify the wadding of the calibration cap and take off the probe from the sample
● Position the cap on the electrode and press ENTER.
● The probe should be positioned vertically with the membrane downwards
● The flashing "cal" message indicates that the instrument is in calibration mode.
● Wait for the current stabilization (approximately 10 min.) and press OK to
validate the calibration.
● The oxygen concentration value flashes during 3 seconds.
83. Dismounting the membrane
1. A. Unscrew cap and gasket.
2. B. Unscrew nut.
3. C. Remove electrode without scratching the cathode.
4. D. Empty the electrolyte left in the probe.
5. E. Unscrew the worn membrane.
84. Mounting the new membrane
1. F. Screw the new membrane on the body till the dead stop.
2. G. Replenish the probe body with 5 ml of electrolyte. Check there is no
impurity or bubble in the electrolyte.
3. H. Preposition the electrode without forcing. It should take its place by
simple gravity.
4. I. Screw the probe nut till the electrode meets a resistance.
5. J. Put back the cap and gasket, screw the cap to ensure water tightness.
85. Oxygen electrode rejuvenation procedure
● A dark Ag Br 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 an electrode rejuvenation
according the following procedure is needed :-
1. Soak the anode in 10 % ammonia for about 1 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 repolishing softly (coating is a only few microns thick) the
areas covered with silver bromide with soft abrasive (N° 400 to 600)
3. After polishing, rinse the anode with demineralised water and wipe it with a
soft cloth.
4. The cleaned electrode performs immediately as well as a new electrode.
86. Functional troubleshooting
Causes Solutions
1. An electrolyte leak (through the membrane).
The current is too high because of an excessive
penetration of oxygen
Change the membrane
2. An important pollution of the electrolyte due
to an incorrect adjustment of the filling Screw
Change the electrolyte. Check there is a
gasket and the screwing. Check the Teflon
band is correctly positioned
3. The membrane holder is incorrectly screwed.
Risk of electrolyte pollution
Change the electrolyte and tighten
correctly the membrane holder
4. Mud or particles on the golden cathode Clean the cathode with an absorbent soft
tissue and rinse the membrane
5. The probe current is null There is no electrolyte in the probe (leak).
6. The probe current is negative •Connation problem to the anode
circuit (loose contact).
• Ag Br deposit on the anode
87. PHOSPHATE analyzer
● This treatment is used to precipitate the hardness constituents of
water and provide alkaline pH control, which will reduce boiler
corrosion.
● Maintains the sodium-to- phosphate molar ratio – (2.1 to 2.9)
● This ratio must be maintained to prevent formation of phosphoric acid
(ratio below 2.1) or free sodium hydroxide (ratio above 2.9)
● The use of phosphate analyzer is to provide a safe alkaline
environment in the boiler.
88. Phosphate water boiler treatment serves 2 basic purposes:
● I) Phosphate controls the ph in the range that is least corrosive
to carbon steel
● II) The event of a condenser leakage or other process upset,
phosphate or the alkalinity produced by it, reacts with Ca, Mg,
Si and other minerals to produce soft sludge that can be blown
down
90. Working Operation
• The 9211 can analyze up to six different
samples
• Adjustment of the flow is carried out with the
help of a needle valve (2).
• At the beginning of the analysis, the sample
is introduced into the measurement cell (4)
with the help of a solenoid valve (5).
91. Two different methods are available
1) For standard measurement range 0-50ppm PO4
( "Molybdate-Vanadate yellow“ )
1) When the sodium molybdate and the ammonium meta-vanadate are
added using the pump (10)
1) They react with the orthophosphate to form a yellow-coloured phospho-
vanado-molybdate compound in an acid medium.
+ Reactions with orthophosphate
1) This method, known as the "Molybdate-Vanadate yellow“ method,
provides measurements across a wide range of values (0.5 to 50 ppm),
with equivalent accuracy to that of the "Molybdate blue“ method.
(sodium
molybdate)
(pump 10)
(ammonium
meta-
vanadate)
a yellow-
coloured
phospho-
vanado-
molybdate
92. Limited to a range of 0 and 5 ppm PO4: "Blue method"
● Sodium molybdate, added with the pump (10), reacts with the
orthophosphate to form a yellow-coloured phosphomolybdate compound.
● Previously, for total acidity reasons, the reducing reagent is added using the
pump (9). Thus, any phosphomolybdate compound formed is immediately
reduced to molybdenum blue.
● The formation of this molybdenum blue compound is highly dependent upon
the pH of the solution and upon the type and amount of reducing agent.
● It is therefore critical to carefully follow the reagent preparation instructions.
The "blue method" will be selected specially when local susceptibility restrict
the use of vanadate from the "yellow method".
● Please note that "blue method" restrict measurement range (0-5 mg/L PO4
only) and temperature ranges of samples and room (0 - 35°C).
+ +
(sodium
molybdate
) (pump
10)
Orthophosp
hate
Phosphomol
ybdate
compund
(yellow)
Reducing
Agent
(pump 9)
Molybdenu
m (Blue)
93. Technical specifications
SAMPLE
Number of channels 1 – 6
Measurement cycle < 10 min / channel
Sample pressure 0.2 to 6 bar (3 to 87 psi)
Temperature «Yellow» method: 5 - 50 °C (41 - 122°F)
«Blue» method: 5 - 35 °C (41 - 95 °F)
Sample flow 15 to 20 L / hour during sampling,
ie, 3 to 5 L/hr, on average, per sample.
MAINTENANCE
Calibration Chemical zero, slope with calibration solution
Maintenance No particular maintenance is necessary. Cleaning can be
done with a soft non-aggressive cloth.
MAINS POWER SUPPLY
Mains • 100- 240 VAC 50 - 60 Hz.
• Automatic switching.
• Max. consumption: 80 VA.
96. Reagent preparation
● Vanadate method - 0 to 50 ppm
To make 2 litres of the reagent:
• Sodium Molybdate dihydrate 180 g
• Ammonium Metavanadate 9 g
• H2SO4 500 mL
● ANSA method - 0 to 5 ppm
Reagent 1 = Molybdate reagent
To make 2 litres of the Molybdate reagent:
• Sodium Molybdate dihydrate 90 g
• Concentrated sulfuric acid 500 mL
Reagent 2 = Reducing agent
To make 2 litres of ANSA reducing agent:
• 1-Amino-2-naphtol-4-sulphonic acid 2 g
• Sodium meta-bisulphite 140 g
• Sodium sulphite 84 g
99. Water Treatment Technologies for Thermal Power Plants have
been examined and improved as a countermeasure against
damage due to factors such as corrosion and scale deposition.
As shown in figure abnormalities in water quality can be a
precursor of problems and therefore serious problems can
be prevented by analyzing the data and taking necessary
measures.
100. SWAS Do’s And Don’ts
Do’s
● Always keep the coolants flowing, even if sample is stopped.
● Check the wiring for the possible loose connections.
● Always flush all the Sample / Coolant lines before starting operation.
● Ensure that sufficient differential pressure exists in coolant inlet and outlet
header (Typical Minimum 2.5 Kg/sq cm)
● Check for leaks in both sample and coolant lines.
● Check whether the connections to valves / pressure regulator / Flow
indicators etc are in right direction.
● Always switch Off the mains power supply while carrying out any
maintenance on the system
Don’ts
● Don’t disturb the settings of Pressure regulator, temperature switch, pressure
switch and safety valve without consulting service Engineer.
● Don’t stop the coolant supply, before isolating the sample supply.
● Don’t carry any maintenance function without isolating the sample supply
