WaterChemistry-SC-Units-PMI-SK-NOV-2015.ppt

power plant water chemistry

1. WATER CHEMISTRY FOR SUPER CRITICAL UNITS
SHARAT KUMAR
AGM (OS/CC)-NTPC
19-NOV-2015

2. INTRODUCTION
1.In supercritical units the water entering the boiler has to be of
extremely high levels of purity. Since supercritical boilers do not
have a steam drum therefore, if the entering water quality is not
good the impurities may deposit in the boiler and carry over of
impurities can result in turbine blade deposits.
2.The practice of cycle chemistry control consists of:
•Purification of water outside the cycle (makeup).
•Removal of impurities within the cycle (air removal, condensate
polishing, chemical cleaning).
•Addition of water treatment chemicals.
•Monitoring.
•Proper design, operation, and maintenance are also a part of the cycle
chemistry control.

3. OBJECTIVES OF WATER CHEMISTRY CONTROL
The objectives of water chemistry control are:
Prevention of corrosion, scale and deposit formation.
•Reducing corrodentconcentrations.
•Minimizing the ingress of impurities.
•Reducing the generation and transport of corrosion
products.
(Thus leading to no Boiler Tube Failure, no turbine failure due to
corrosion, and minimal turbine efficiency losses due to
deposits)

4. Corrosion mechanisms in the water/steam cycle of
Supercritical plants
•Flow-accelerated corrosion (FAC), due to the accelerated
dissolution of the protective oxide (magnetite) on the surface of
carbon steel components caused by flow.
•Corrosion fatigue (CF), due to repetitive applied stress causing
damage to the internal protective oxide layer (magnetite).
•Pitting corrosion due to inadequate shutdown procedures
throughout the cycle.
•Stress corrosion cracking (SCC)of sensitive steel components
in the superheater, reheaterand steam turbine due to the
presence of impurities, such as sodium hydroxide and chloride.
Corrosion must be prevented through treatment of the water.

5. SINGLE PHASE FAC-CARBON
STEEL
FAC ON AN HP-FW TUBE SHEET

6. TWO PHASE FAC-SHELL SIDE OF LP HEATER
A-UNIT OPERATING ON OT-(Red area-single phase flow and is
protected by FeOOH, Black area-two phase FAC).
B-UNIT OPERATING ON AVT(R)-(Heavy deposition in single phase
area-left side, Two phase FAC-right side).

7. PITTING AND STRESS
CORROSION CRACKING
CORROSION FATIGUE

8. FACTORS INFLUENCING FAC
SOLUBILITY OF MAGNETITE AS A FUNCTION OF TEMPERATURE AT
VARIOUS AMMONIA CONCENTRATIONS

9. PITTING CORROSION
Internal pitting corrosion is caused by chloride/sulfate and/or oxygen
plus water and it happens when the unit is shutdown. Pitting is a form
of corrosion that occurs only while the unit is offline. It is typically
caused by oxygen-saturated stagnant water. It can also be caused by
salt contaminants (chlorides and sulfates) that are deposited on boiler
tubes coming in contact with moisture during unit shutdown and layup.
To control pitting corrosion, proper shutdown and layup procedures of a
unit must be utilized every time a unit is shutdown. A dry layup involves
completely drying the boiler to remove all water. A wet layup is used if
no oxygen is present in boiler water and a nitrogen blanket can be
applied to the unit to prevent the ingress of oxygen. Or, if oxygen is
already present, circulation of the boiler water can be achieved to
eliminate stagnant conditions.

10. STRESS CORROSION CRACKING
Stress Corrosion Cracking (SCC) is a defined as cracking of metal
produced by the combined action of corrosion and stress. It is caused
by chlorides plus water. It is initiated on shutdown and propagated
during operation.
Essentially, SCC is initiated by the creation of pits and over time the
combination of the environment and stresses will grow the pit until it
forms a crack. Once a crack is formed it is only a matter of time until
the material fails.
The risk for SCC can be reduced by eliminating the water chemistry
related initiating steps of pit creation. As such, it is extremely
important to perform layup and reheat drying procedures to control
pitting corrosion. The best practice is to control boiler water pH and
trip the unit when it drops below 7.0.

11. CORROSION FATIGUE
Corrosion fatigue occurs with the combined action of cycle loading and a
corrosive environment.
Corrosion fatigue is caused by the synergistic effects of stress and the
environment. This leads to a breakdown of the protective magnetite layer on a
tube surface by both mechanical stress and an aggressive chemical
environment.
Stresses due to cyclic loading (startup/shutdown of unit) create pits at
unprotected boiler tube surfaces. Further cyclic stresses cause pits to align in a
crack, eventually leading to failure.
Proper boiler water chemistry can help reduce the risk for corrosion fatigue.
During startup, cyclic stresses are at their highest. Low pH excursions or high
levels of dissolved oxygen combined with high cyclic stress have been proven
to be particularly damaging to the protective magnetite layer. As such, it is
extremely important to maintain proper water chemistry during unit startup, and
that OEM heat-up and cool-down rates are not exceeded. Best practices
include controlling dissolved oxygen, especially on startup and pegging the
deaerator as soon as possible on startup.

12. FEEDWATER TREATMENTS
Feed water chemistry is critical to the overall reliability of fossil plants.
Corrosion products are generated here, flow around the cycle, deposit in the
various boiler areas acting as the main initiating centers for most of the major
failure mechanisms and need chemical cleaning for removal.
Reducing, AVT(R)-Reducing agent (N
2H
4) is added at CEP
discharge. pH is maintained by using ammonia. Here the ORP
(oxidation-reduction potential) is in the range –300 to –350 mv.
Oxidizing, AVT(O)-No reducing agent is added. Ammonia is added
after the condensate polisher. Here the ORP should be positive and
the range around 0 mv to + 50 mv.
Oxygenated, OT-Ammonia plus oxygen is added. Here the ORP will
be around +100 to +150 mv.

13. Itshouldbenotedthat,whetheritis
AVT(R),AVT(O),orOT,thechemistry
offersnoprotectiontowardsaninfluxof
impurities,sayfromacondensertube
leak,makeuptreatmentsystemupset,or
othersource.Continuous,on-line
chemistrymonitoringisnecessaryto
detectproblemsandmakequick
corrections.
FEEDWATER TREATMENT

14. FEEDWATER CHEMISTRY
•AVT(R) [Reducing All Volatile Treatment]
•Elevated pH of 9.0 –9.3.
•Cation conductivity of less than 0.20 µS/cm.
•Minimum air in-leakage to ensure less than 10 ppb dissolved oxygen
at CPD.
•Addition of reducing agent (N
2H
4) to the feed water to ensure
reducing ORP (-300 to -350 mv).

15. Fe = Fe2+ + 2e–
2 H2O + 2e–= 2 OH–+ H2
2 Fe2+ + OH–= Fe(OH)+
Fe(OH)+ + 2 H2O = 2 Fe(OH)2 + + H2
Fe(OH)+ + 2 Fe(OH)2 + + 3 OH–= Fe3O4 + 4 H2O
The dissolution of iron is inhibited by increasing pH, which
causes a reduction of the Fe2+ and Fe(OH)+ ion
concentrations corresponding to the solubility products of
Fe(OH)2 or the dissociation constants of the reactions:
Fe(OH)2 = Fe(OH)+ + OH–
Fe(OH)2 = Fe2+ + 2OH–
MAGNETITE FORMATION UNDER AVT (R)

16. Ripple Magnetite Formed on a Waterwall Tube of a Once-
Through Boiler

17. Ripple Magnetite Formation

18. FEEDWATER CHEMISTRY
•AVT(O) [Oxidizing All Volatile Treatment]
•Elevated pH of 9.2 –9.6.
•Cation conductivity of less than 0.20 µS/cm.
•Minimum air in-leakage to ensure less than 10 ppb dissolved oxygen
at CPD.
•No addition of reducing agent (N
2H
4) to the feed water to ensure
oxidizing ORP.

19. •OT (Oxygenated Treatment)
FEEDWATER CHEMISTRY
•Cation conductivity of less than 0.15 µS/cm.
•Minimum air in-leakage to ensure less than 10 ppb dissolved oxygen at CPD.
•Addition of oxygen to the feed water to ensure oxidizing ORP (100 to 150 mv).
MAJOR DIFFERENCE BETWEEN AVT(R) AND OT

20. BENEFITS OF OT
a)Minimized corrosion in the feed water, low rates of corrosion product transport to
boiler resulting in
• Reduced or avoided fouling of orifices.
• Reduced boiler deposition, allowing either elimination or the need to clean
or substantial extension of the interval between operational cleanings.
• Prevention of pressure drop problem in once through boilers due to the
formation of ripple magnetite deposits on the generating tubes.
• Reduced risk of boiler tube failure by thermal fatigue and overheating
mechanism.
b)Minimized deposition of corrosion products on boiler feed pumps.
c)Establishment of an operating environment which does not support single phase
flow accelerated corrosion (FAC).
d)Minimized turbine fouling.
e)Lowest possible cycle chemical treatment costs.
f)Extended CPU runs with commensurate reductions in operating costs.
Collectively these benefits are enumerated as increased unit availability & reliability
and associated reductions in operating and maintenance costs.

21. OXYGEN DOSING SYSTEM

22. TARGET VALUES
S.NO
.
PARAMETER AVT(R)
(Mixed
metallurgy)
AVT(R)
(All
ferrous)
AVT(O)
(All
ferrous)
OT
(All ferrous)
1.pH at Eco inlet9.0 -9.3 9.2 -9.69.2 -9.6 9.0 -9.6 (drum)
8.5 -9.5 (once through)
2.Cation
Conductivity
(μS/cm) at Eco
inlet
< 0.2 < 0.2 < 0.2 < 0.15
3.O
2
(ppb) at Eco
inlet
< 5 < 5 5 -10 30 –50 (drum)
50 –200 (once through)
4.O
2
(ppb) at CEP
Discharge
< 10 < 10 < 10 < 10
5.ORP at Deaerator
inlet, mV
-300 to
-350
-300 to
-350
0 to + 50+100 to +150
6.Fe (ppb) at Eco
inlet
< 5 < 2 < 2 (< 1)< 2 (< 0.5)
7.Cu (ppb) at Eco
inlet
< 2 -- -- --
•The figures in ( ) indicate achievable values.

23. CYCLE CHEMISTRY MONITORING
The chemistry parameters that may be monitored under the cycle
chemistry guidelines fit into two general categories:
•Those parameters which all fossil plants should have for
optimum chemistry control (termed the core parameters).
•Those parameters which are regarded as diagnostic parameters
that may be monitored as needed for troubleshooting or during
commissioning.

24. CYCLE CHEMISTRY CORE MONITORING PARAMETERS FOR
CONVENTIONAL FOSSIL UNITS
S.NO.PARAMETER MONITORING POINTS
1. Cation
Conductivity
Condensate pump discharge, Condenser polisher outlet or Economizer
inlet, Reheat or main steam, Boiler water
a
2. Specific
Conductivity
Treated makeup, Boiler water
b
3. pH Boiler water
c
4. Dissolved oxygenCondensate pump discharge, Economizer inlet, Boiler water
d
5. Sodium Condensate pump discharge, Economizer inlet, Reheat or main steam
6. Phophate Boiler water (PC only)
7. Oxidation-
reduction potential
(ORP)
Deaerator inlet
e
8. Air in-leakage Condenser air removal system exhaust
9. Carryover Calculated from Boiler water and saturated steam readings
f
Notes:
a–Drum boiler units only
b–Drum boilers on PC and CT
c–Drum boiler units only
d–Only required in drum boiler units on OT
e–Only required on units employing AVT(R) as feedwater chemistry
f–Based on either on-line monitor readings (if available) or analysis results for grab samples
*-Boiler water sample shall be drawn from downcomer.

25. DIAGNOSTIC MONITORING PARAMETERS
In customizing the cycle chemistry programs, monitoring one or more of
the diagnostic parameters with on-line analyzers can be done. The
diagnostic monitoring parameters are listed below.
•Ammonia
•Chloride
•Hydrazine
•Various ions in water and steam (by Ion Chromatography)
•Iron and Copper
•Phosphate
•Silica
•Total Organic Carbon
For many of the parameters and techniques more than one approach
may be available. In some instances, particularly when chemistry data
are needed for diagnostic purposes, collection of grab samples for
laboratory analysis may be sufficient.

26. DESCRIPTION OF MONITORING PARAMETERS
CONDUCTIVITY
There are three types of conductivity measurements:
•Specific conductivity
•Cation(acid) conductivity
•Degassed cationconductivity
Conductivity, more specifically cationconductivity is a Core Monitoring parameter. Cation
conductivity is continually monitored on-line to indicate the ionic concentration in the
solution being monitored and to warn of contaminant in-leakage. These three types of
conductivity are also monitored for one or more of the following reasons:
•To facilitate the correlation of a water chemistry parameter (e.g., pH, conductivity,
ammonia correlation).
•To check the accuracy of water chemistry control (such as ammonia or pH).
•To warn of condensate polisher malfunction.
•To provide feedback signal for automated process control.
•To facilitate demineralizer system operation and/or regeneration.
•To monitor for the intrusion of volatile contaminates (e.g., CO
2or volatile organics).
•To monitor the laboratory pure water system.
•To determine the concentration of ions in solution.

27. DESCRIPTION OF MONITORING PARAMETERS
pH
In boiler water, pH is a Core Monitoring Parameter. As such, pH should
continuously be monitored on-line to check the acceptability of the water
chemistry, thereby ensuring that corrosion rates are kept at low levels.
In fossil plant steam-water cycles pH may also be monitored for one or
more of the following reasons:
•Corrosion of metals and alloys is a function of pH.
•Alkaline pH values increase the stability of the oxide film and reduce
oxide solubility in water.
•To facilitate the correlation between two or more water chemistry
parameter (e.g., pH, conductivity, ammonia correlation).
•To provide a feedback signal for automated process control.
•To warn of in-leakage of contaminants.
•To warn of condensate polisher malfunction.
•To troubleshoot or verify the accuracy of other on-line pH monitors.
•To check the pH of water streams not routinely monitored continuously
by on-line monitors.

28. DESCRIPTION OF MONITORING PARAMETERS
DISSOLVED OXYGEN
Dissolved oxygen (DO) is a Core Monitoring Parameter. As such, the reason
for continuous on-line monitoring of DO is to check the acceptability of
water chemistry, thereby ensuring that dissolved oxygen is maintained at
acceptable levels.
Dissolved oxygen may also be monitored for one or more of the following
reasons:
•To check the accuracy of water chemistry control, so ensuring that
corrosion rates are kept at acceptable low levels.
•To facilitate the correlation of a water chemistry parameter with plant
operating variables, with an aim to optimizing operations (e.g.,
condenser air removal or deaeratoroperations).
•To provide feedback stimulus for automated process control, e.g., for
oxygen control on oxygenated treatment (OT).
•To monitor for condensate pump seal leakage.
•During and following changes in feedwatertreatment.

29. SODIUM
DESCRIPTION OF MONITORING PARAMETERS
Sodium is a Core Monitoring Parameter. As such, it should be monitored
continuously on-line to check the acceptability of water chemistry, thereby
ensuring that corrosion rates are kept at low levels.
Sodium may also be monitored for one or more of the following
reasons:
•To warn of in-leakage of contaminants.
•To warn of boiler water carryover.
•To identify cooling water in-leakage at the main steam
condenser.
•To warn of condensate polisher malfunction.

30. PHOSPHATE
DESCRIPTION OF MONITORING PARAMETERS
Phosphate is a Core Monitoring Parameter. The on-line monitoring
equipment is used most frequently to monitor phosphate in the continuous
blowdownof fossil boilers. Optimal phosphate concentration is both a
function of the operating pressure of the steam/water cycle and the
likelihood of boiler contamination.
Phosphate is continually monitored on-line in the plant for the following
reasons:
•To check the accuracy of water chemistry control (such as the sodium-
to-phosphate molar ratio).
•To facilitate the correlation of phosphate content with plant operating
variables.
•To warn of in-leakage of contaminants.

31. OXIDATION-REDUCTION POTENTIAL
DESCRIPTION OF MONITORING PARAMETERS
•Oxidation-reduction potential (ORP) is a Core Monitoring Parameter, in
mixed metallurgy systems using all volatile treatment including a
reducing agent—ATV(R). The purpose for monitoring ORP is to assure
the feedwateris in a reducing condition as needed to minimize copper
transport when operating with AVT(R) Chemistry.
•ORP is continually monitored on-line in units with copper alloy
feedwatersystem components to monitor the chemistry environment.
Negative ORP values indicative of a reducing environment are needed
under all conditions to minimize copper corrosion and transport.

32. AIR IN-LEAKAGE
DESCRIPTION OF MONITORING PARAMETERS
•Air in-leakage is a core parameter. It is the primary source of oxygen and
carbon dioxide in the condensate and feedwatersystem. Carbon dioxide
may degrade condensate polisher performance and elevate cation
conductivity readings around the cycle. High air in-leakage rates can also
cause corrosion damage to the condenser shell and can result in reduced
condenser vacuum, thereby reducing the efficiency of the cycle.
•Carbon dioxide also can have an effect on the pH of feedwater.
•Air in-leakage should be restricted to no more than 1.0 scfm(1.7 m
3
/h) per
100 MW of generating capacity. Monitoring and limiting the amount of air
in-leakage (condenser air removal system flow) is essential for proper
control of dissolved oxygen and carbon dioxide in the cycle. Such
monitoring will determine when an exhaustive effort must be made to find
and fix the source of air leakage.

33. CARRYOVER
DESCRIPTION OF MONITORING PARAMETERS
Carryover is defined as the ratio of concentration of a chemical species in the saturated
steam exiting the boiler drum to the concentration of the same species in the boiler water.
Total carryover (T) is defined as follows.
T = M + V
M is mechanical carryover (due to steam moisture) and V is the vaporous
carryover (due to volatile partitioning into the vapor phase).
•Mechanical carryover represents any boiler water fine droplets or mist that exits the
boiler drum with the saturated steam. It is dependent on factors such as boiler
pressure, drum water level, and the design and integrity of the internal separator
devices employed to prevent boiler water from entering the steam.
•Vaporous carryover represents those impurities which partition from the liquid to the
vapor phase during the boiling process. The partitioning tendency of individual
chemical species is dependent on operating temperature and pressure. These
partitioned impurities cannot be removed by the steam separator devices which are
provided to control mechanical carryover. The extent to which a species partitions to
steam often exceeds its solubility in steam, which can lead to deposition in
superheaters, reheatersand steam turbines.

34. AMMONIA
DESCRIPTION OF MONITORING PARAMETERS
Ammonia is monitored to:
•Check the accuracy of water chemistry control, so ensuring that
corrosion rates are kept at acceptable low levels.
•Facilitate the correlation of ammonia with other chemistry
parameters (i.e., pH and specific conductivity).

35. DESCRIPTION OF MONITORING PARAMETERS
CHLORIDE
Chloride is not a Core Monitoring Parameter but its analysis is recommended
as a troubleshooting tool and for commissioning purposes. Elevated chloride
concentrations in the boiler can lead to corrosive conditions which can
damage the waterwalltubes. Carryover can degrade steam purity, lead to build-
up on turbine components and promote corrosion mechanisms. Minimizing
this carryover is an additional reason to control the chloride content of boiler
water.
Chloride is most frequently monitored in the plant for the following reasons:
•To warn of in-leakage of contaminants (primarily condenser cooling water
ingress).
•To facilitate the correlation with other chemistry parameters (i.e., cation
conductivity).
•To check the accuracy of water chemistry control (for chloride), so ensuring
that carryover and deposit rates are kept at acceptable low levels.
•To warn of condensate polisher malfunction.
•To warn of make-up demineralizer malfunction.

36. HYDRAZINE
DESCRIPTION OF MONITORING PARAMETERS
Hydrazine is not a Core Monitoring Parameter but is often monitored in
mixed metallurgy feedwatercycles using reducing All Volatile Treatment -
AVT(R).
Hydrazine is continually monitored on-line in the plant for the
following reasons:
•To check the accuracy of water chemistry control, so ensuring
that corrosion rates are kept at acceptably low levels.
•To evaluation of other chemistry parameters (i.e., ORP and
dissolved oxygen).
•To provide feedback stimulus for automated process control.

37. DESCRIPTION OF MONITORING PARAMETERS
VARIOUS IONS IN WATER AND STEAM (by Ion Chromatography)
Ion chromatography (IC) is a detection technique that is applicable to quantification of both
cationsand anions.
Ion chromatographs are used on-line in the plant for the following reasons:
•To warn of in-leakage of contaminants.
•To warn of condensate polisher malfunction.
•To check the accuracy of water chemistry control (such as sodium, ammonia, chloride,
sulfate, phosphate), so ensuring that corrosion rates in both the boiler and steam system
are kept at acceptable low levels.
•To detect and quantify organic acids which may be the result of water treatment plant
inadequacy, condenser in-leakage, or degradation of organic boiler treatment chemicals.
•To facilitate the correlation of a water chemistry parameter with plant operating variables,
with an aim to optimizing operations.

38. DESCRIPTION OF MONITORING PARAMETERS
IRON AND COPPER
Iron and copper are not defined as Core Monitoring Parameters but it is
suggested that samples be taken and analyzed periodically to measure
corrosion product levels in the steam-water cycle.
Corrosion product monitoring in the plant is conducted primarily for the
following reasons:
•To facilitate the correlation of a water chemistry parameter with plant
operating variables.
•To check the accuracy of water chemistry control (such as reducing
agent, oxygen, ammonia or pH), so ensuring that corrosion rates are
kept at acceptable low levels.

39. DESCRIPTION OF MONITORING PARAMETERS
SILICA
Silica is not a Core Monitoring Parameter for fossil plants but is widely
monitored for diagnostic and troubleshooting purposes. It is included as a
Core Monitoring Parameter for combined cycle plants. Elevated silica
concentrations in steam can lead to silica deposition in the low pressure
turbine so it is desirable to control the silica content of boiler water. Silica
content is also the primary indication of anion resin exhaustion in both
makeup and condensate polishing equipment.
Silica is most frequently monitored in the plant for the following reasons:
•To warn of in-leakage of contaminants.
•To facilitate the correlation of a water chemistry parameter with plant
operating variables, with an aim to optimizing operations.
•To check the accuracy of water chemistry control (for silica), so
ensuring that carry-over and deposit rates are kept at acceptable low
levels.
•To warn of condensate polisher malfunction.

40. DESCRIPTION OF MONITORING PARAMETERS
TOTAL ORGANIC CARBON
Total organic carbon (TOC) is not a “Core Monitoring Parameter” but it is
sometimes used for continuous monitoring of organics in make-up water
treatment systems and within the steam-water cycle.
TOC is monitored by means of grab sampling and analysis or by on-line
monitoring in the plant for one or more of the following reasons:
•To provide additional temporary information for troubleshooting
unusual problems.
•To warn of in-leakage of contaminants.
•To monitor make-up water quality for organic carbon content.

41. REQUIREMENTS FOR SUPERCRITICAL UNITS
1. Use of any copper or copper alloys in the condensate and
feedwater cycle is not permitted.
2. Copper or copper alloy condensers are acceptable.
3. 100% full flow deep bed condensate polishing with
external regeneration is required.
4. Cycle chemistry should be oxygenated feedwater
treatment (OT).
5. Makeup water plant should be capable of producing
water with
•Sp. conductivity <0.1 µS/cm, with
•Chlorides, Sulfates and Sodium <3 ppb
•Silica <10 ppb
•TOC <100 ppb

42. ACTION LEVELS
There are four action levels which have been developed based on the
following criteria:
1.Normal-Values are consistent with long term system reliability. A safety
margin has been provided to avoid concentration of contaminants at
surfaces and under deposits.
2.Action Level 1-There is a potential for the accumulation of contaminants
and corrosion. Return values to normal levels within 1 week.
3.Action Level 2-The accumulation of impurities and corrosion will occur.
Return values to normal levels within 24 hours.
4.Action Level 3-Rapid corrosion can occur. Shutdown the unit within 4
hours.
•Immediate shutdown-Rapid boiler tube damage by low boiler water pH.
Immediate shutdown is required.
•Action Level 1 value: 2 x (Normal target value)
•Action level 2 value: 2 x (Action level 1 value)
•Action level 3 value: > (Action level 2 value)
•Immediate shutdown: In case of supercritical units when economizer
inlet pH drops below 7.0, the unit should be tripped immediately.

44. CONDENSATE LIMITS
Sample PointParameter Normal
Value
Action Level-
1
Action
Level-2
Action
Level-3
Immediate
shutdown of
Unit
CPD Cation
conductivity
(µS/cm)
<0.20 > 0.20 NA NA NA
CPD Sodium (ppb) <2.0 > 2.0 NA NA NA
CPD Dissolved oxygen
(ppb)
<10 <20 NA NA NA
CPD TOC (ppb) <100 > 100 NA NA NA
CPU EffluentCation
conductivity
(µS/cm)
<0.10 <0.3 <0.6 > 0.6 > 1.0
CPU EffluentSodium (ppb) < 2.0 <4.0 <8.0 > 8.0 > 50
CPU EffluentSilica (ppb) <10.0 > 10.0 NA NA NA
CPU EffluentSulphate (ppb)< 2.0 > 2.0 > 6.0 > 12.0> 24.0
CPU EffluentChloride (ppb)< 2.0 > 2.0 > 6.0 > 12.0> 24.0

45. FEEDWATER LIMITS
Sample Point Parameter Normal Value Action
Level-1
Action
Level-2
Action
Level-3
Immediate
shutdown of
Unit
Economizer InletCation
conductivity
(µS/cm)
<0.15 <0.3 <0.6 > 0.6 NA
Economizer InletpH 8.5-9.5 < 8.5
> 9.5
NA NA NA
Economizer InletAmmonia &
Sp. Cond.
Consistent with
pH
Economizer InletIron (ppb) <2.0 > 2.0 NA NA NA
Economizer InletCopper (ppb)<2.0 > 2.0 NA NA NA
Economizer InletDissolved
oxygen (ppb)
50-200 NA NA NA NA
Economizer InletSuspended
Solids (ppb)
< 10 > 35 > 50 > 100 > 150

46. MAIN/REHEAT STEAM LIMITS
Sample Point Parameter Normal
Value
Action
Level-1
Action
Level-2
Action
Level-3
Immediate
shutdown of
Unit
Main/RH Steam Cation
conductivity
(µS/cm)
<0.15 >0.3 >0.6 > 0.6 NA
Main/RH Steam Sodium (ppb)<2.0 <4.0 < 8.0 > 8.0 NA
Main/RH Steam Silica (ppb)<10 <20 <40 > 40 NA
Main/RH Steam Chloride
(ppb)
<2.0 <4.0 < 8.0 > 8.0 NA
Main/RH Steam Sulphate
(ppb)
<2.0 <4.0 < 8.0 > 8.0 NA
Main/RH Steam TOC (ppb) <100 > 100 NA NA NA

47. MAXIMUM ANNUAL EXPOSURE TO
CONTAMINANTS
TARGETS CUMULATIVE
HOURS PER YEAR
N (NORMAL) --
1 (ACTION LEVEL-1) 336 (2-WEEKS)
2 (ACTION LEVEL-2) 48 (2-DAYS)
3 (ACTION LEVEL-3) 8
IMMEDIATE SHUTDOWN 1

48. STEAM PURITY LIMITS DURING STARTUP
PARAMETER FREQUENCY LIMIT
Cation conductivity,
µS/cm
Continuous < 0.45
Sodium, ppb Grab, daily < 12
Silica, ppb Grab, daily < 40
Chloride, ppb Grab, daily < 12
TOC, ppb Grab, weekly < 200
Sulphate, ppb Grab, daily < 12
1.Typical operation duration would be about one week.
2.After this the normal chemistry limits would be met and maintained.

49. CYCLE ON-LINE CHEMICAL INSTRUMENTATION
1.All chemical instrumentation needs to be alarmed and trended in the main
control room.
2.Ensure cycle samples are maintained at 25
0
C.
3.Hotwell cation conductivity mounted locally on each condenser half.
4.Condensate –Cation conductivity, sodium.
5.Common condensate cleanup outlet –Sodium, silica, specific conductivity.
6.Condensate downstream of cleanup –Specific conductivity mounted
locally. Used to control cycle water pH.
7.Deaerator Inlet –Dissolved oxygen/ ORP.
8.Deaerator Outlet –Dissolved oxygen/ ORP.
9.Economizer Inlet –Cation conductivity, specific conductivity, pH.
10.Main Steam –Cation conductivity, sodium, specific conductivity.
11.High Pressure Heater Drain –Dissolved oxygen/ ORP (only need to monitor
one of the drains).
12.Reclaim/Miscellaneous Drain Tank –Cation conductivity mounted locally
and used to trip valve from drain tank to waste.

50. KEYS TO SUCCESS
1.Operate safely within designated parameters 100% of the time.
2.Proactive/Preventative approach.
3.Understanding and attention to chemical impacts all through the organization
for all equipment.
4.Integrated water chemistry plan.
5.Identify performance gaps and develop plan to close those gaps.
6.Continuous benchmarking.
7.No boiler tube failure or turbine problems form cycle chemistry.
8.Process improvement continuously.
9.Zero cycle chemistry equipment failures [turbines, condensers, feed water
heaters, etc].
10.Complete organizational alignment on goals, parameters, and action points.
11.Employees are knowledgeable of water chemistry issues and take appropriate
actions.

51. THE BASIS FOR CYCLE CHEMISTRY
1.To form the proper protective passive layer.
2.To protect this passive protective layer during operation.
3.To protect this passive protective layer during shutdown.
All boiler tube and turbine blade failures influenced by cycle water
chemistry have the breakdown of the passive protective layer as
part of the failure mechanism.
If you protect your protective layer 24/7 seven days a week 365 days
a year, you will not have boiler or turbine blade failures due to
cycle chemistry.