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Improving operating efficiency and maximizing component life has always been
critical, but never so much as today. Nearly half of forced power plant
shutdowns today can be attributed to impurities and other cycle chemistry
problems. With each shutdown costing a plant millions of dollars and
competition between utilities increasing continually, ignoring the proper
measurements in a water treatment program is not an option. An increased
understanding and improved management of these measurements and their
applications is one of the most significant methods of improving the water
quality in a plant. This in turn will guarantee increased profits, efficient
operation, long-term integrity of the materials of construction and improved
plant performance.
Basic measurement parameters such as conductivity, pH, dissolved oxygen, and
sodium ion are the backbone of any water treatment program. It is obvious
that continuously maintaining and improving these critical measurements
should be of utmost importance in the effort to improve system life, plant
integrity, and overall efficiency. However, many of the applications where
these basic measurements are made as well as the measurements themselves are
often misunderstood and neglected. These individual applications include the
makeup water, condensate water, feedwater, blowdown, steam, cooling tower
water and effluent water.
Measurements
One of the initial difficulties in making pure water measurements such as
conductivity, pH, dissolved oxygen and sodium ion is preserving the
integrity of the sample. This is especially difficult in power plants, where
different sample points vary widely in their respective pressure,
temperatures, and flows. Because of its low ionic content, pure water will
quickly dissolve traces of contaminants from sample lines, flow chambers,
containers and even the atmosphere. It is necessary to rinse new or unused
sample lines a surprisingly long period of time before a representative
sample can be obtained.
A constant threat of contamination comes from the atmosphere which contains
oxygen, O2, as well as carbon dioxide, CO2. Oxygen
from the air which leaks into the system can cause a perceived high
dissolved oxygen reading. Carbon dioxide ionizes in the water to form a weak
solution of carbonic acid. Carbon dioxide can cause errors in both pH and
conductivity readings. For this reason, all pure water measurements should
be made on closed, flowing samples which are free of leaks.
The flow rate of steam and boiler samples should be high enough so that any
iron oxide particles or deionizer resins do not become caught in sample
lines or flow chambers. The exchange of ionic species with accumulated
particles in the sample lines or the electrode flow chamber can cause errors
which are often very difficult to troubleshoot. This problem can be minimized
by utilizing low volume flow chambers and small sample line diameters which
enhance flow velocity.
Conductivity / Resistivity / TDS
Conductivity is the ability of a water sample to carry electrical current.
In water, current is carried only by ionic materials - typically mineral
contaminants which dissolve into positive and negative ions. Conductivity
measurements remain the first line of defense in determining upsets,
unacceptable contamination and other corrosive and depositing conditions
which may exist. The high reliability, sensitivity and relatively low cost
of conductivity instrumentation makes it the primary parameter of any good
monitoring program. Many applications are measured in units of resistivity,
the inverse of conductivity. Other applications require the measurement of
total dissolved solids (TDS), which is related to conductivity by a factor
dependent upon the level and type of impurities.
In power plant water applications, conductivity measures contaminants
consisting mostly of mineral salts, although carbon dioxide from the air,
organic acids from treatment amine decomposition, and other acids or bases
are not uncommon. Conductivity is a non-specific measurement in that it
responds to the concentration of any conductive material dissolved in the
water. It cannot distinguish between materials present, whether they are
treatment chemicals or contaminants. However, two types of conductivity
measurements - specific and cation - can be made in order to obtain a more
accurate determination of the level of contaminants vs. chemicals in a plant.
Specific Conductivity
Direct conductivity measurement of a water or condensed steam sample
includes response to treatment chemicals such as ammonia or amines,
corrosive mineral contaminants and carbon dioxide. By itself, this specific
conductivity cannot distinguish among them because all of the ions will
contribute to the overall conductivity of a sample. However, under normal
operating conditions, treatment chemicals have the highest ionic
concentration and dominate the response. Specific conductivity is therefore
used along with pH as a reliable indicator of treatment chemical levels.
Cation Conductivity
Specific conductivity can detect only large amounts of corrosive
contaminants, since the conductivity of the treatment chemicals serves to
mask out lower levels typically present. To improve sensitivity to these
corrosive contaminants, a water sample is passed through a cation exchanger,
where two mechanisms are used to increase sensitivity to contaminants. In
the first mechanism, the cation exchanger retains ammonia and amines on the
cation resin in the cartridge, effectively removing their large background
contribution to conductivity. The second mechanism consists of mineral salts
being retained in the exchanger and replaced by acid which actually boosts
the conductivity, increasing measurement sensitivity. The overall effect of
the cation exchanger is thus to reduce the chemical contribution to
conductivity and amplify the contaminant conductivity. Because of this,
cation conductivity continues to be the most useful measurement for
corrosive contaminant detection.
pH
pH is the measurement of the free acidity or alkalinity of a solution; in
this case, the solution is water. The measurement of pH is critical to
prevent corrosion processes from occurring. The second leading cause of
boiler failure can be attributed to corrosion. However, pH measurement in
high purity water can be extremely difficult. Pure water has a high
resistance and a high vulnerability to contamination, and often possesses
extremely high temperatures in the steam/ water cycle, so pH is often a very
challenging measurement which can easily be measured improperly.
It has been argued that pH should not be measured in pure water since a
conductivity measurement is simpler and assures high purity. If water
treatment systems always produced pure water there would be no need for pH
measurement, but treatment systems are never perfect. Conductivity cannot
distinguish among contaminants, and therefore pH can be used in conjunction
with conductivity to distinguish between contaminants which may lend more to
a more acidic or basic pH level. pH has thus proven to be a very useful
measurement in diagnosing system problems, such as a condensate leak in the
condenser. The level of pH-adjusting ammonia or amine also requires pH
measurement in addition to conductivity measurement to assure proper
contamination detection.
Dissolved Oxygen (D.O.)
The measure of the amount of dissolved oxygen gas in the water is used to
monitor performance of deaerators, control chemical injection and to detect
air leakage into vulnerable parts of the feedwater and condensate system.
Oxygen corrosion and the associated corrosion products represent a great
expense to power plant water components. Oxygen pitting is often seen in
economizers during operation, while superheaters and reheaters are
especially susceptible during standby conditions. All carbon steel
components in a system are vulnerable to this type of attack. Copper alloy
corrosion in condensate and feedwater systems is a function of oxygen.
Oxygen can cause corrosion fatigue of boiler tubes as well as turbine disks
and blades.
Totally eliminating oxygen from the water is virtually impossible. Potential
sources of oxygen ingress include leaking turbine/condenser expansion
joints, low pressure heater flanges and connections, turbine explosion
diaphragms, leaking pipe joints, etc. Because the oxygen will always find a
way into the system, the oxygen level is constantly monitored and controlled.
This is typically done by means of a mechanical deaerator and/or chemical
reaction. Regardless of the type of treatment used, the dissolved oxygen
level is always controlled to the parts-per-billion range. Continuous
measurement of dissolved oxygen at several points is critical to the long
term reliability of critical components, especially the boiler.
Sodium Ion
On-line measurement of sodium ion concentration is typically much more
sensitive than conductivity in determining upsets, unacceptable
contamination and other corrosive and depositing conditions. Sodium is a
pervasive contaminant and can be applied to boiler systems to detect
condenser leaks, boiler carryover, evaporator entrainment, break-through in
cation exchangers and condensate polishers, and sodium content in water
supplies and other processes. Sodium ion is often the choice measurement
over conductivity in monitoring cation exchangers, where the effluent is a
highly conductive dilute acid and sodium is the first ion to break through
the deionizer bed. It is also used for monitoring treated boiler water and
condensate containing a pH-adjuster or oxygen scavenger which can add to the
background conductivity.
POWER PLANT APPLICATIONS
In any power plant, there are numerous components that are part of the water
treatment system. There are also a wide variety of treatments that are
performed on the water from the point it enters the plant (makeup water) to
the point it exits (effluent water). Each plant has its own components and
treatments based upon the specific requirements of that plant as well as the
water that is available to use. It is a rare occurrence to find two plants
exactly alike, since they each can differ in power output, boiler or steam
generator type, metallurgy, fuel type, and water supply characteristics.
Regardless of whether a plant is fossil-fuel based or nuclear-based, the
applications that are most common from plant to plant are the makeup water,
condensate water, feedwater, blowdown, steam, cooling tower water and
effluent water. Figure 1 is a diagram of a typical fossil-fuel power plant.
Figures 2 and 3 are diagrams of typical nuclear-reactor power plants.
Makeup Water
Since there is a constant loss of cycle water for one reason or another, it
is always necessary to have a continual source of incoming water. Treating
this water is the beginning of the power plant’s cycle chemistry.
Makeup treatment almost always consists of demineralization to remove
dissolved impurities. Other pretreatment equipment consists of softeners,
clarifiers, and filters. On an increasing basis, membrane technology is
being used along with ion exchangers for effective demineralization
treatment. The overall goal of the demineralization treatment is to yield
high purity water for use in the overall feedwater/condensate cycle. Figure
4 illustrates a typical makeup water system.
Ion exchange treatment will typically involve the use of at least a cation
exchanger followed by an anion exchanger. Often times a mixed bed exchanger
will follow these, with a vacuum degasifier somewhere in the series.
Membrane treatment, either of the reverse osmosis (RO) or electrodialysis
(ED) type, is a technique frequently utilized to yield a more efficient
demineralizer system. This treatment is often upstream of the ion exchangers
to reduce the dissolved solids, thus cutting back the load on the ion
exchangers.
Makeup water is usually not directly added to the system; rather, it is
stored in the makeup water storage tank, where enough water is available to
plant operations for a short period of time if the need should arise. This
water is continually monitored to ensure integrity and may be reprocessed
through the demineralizers if necessary.
Condensate Water
The condensate portion of the cycle includes the condenser, hotwell, and the
condensate polishers. The condenser is cooled by water from the cooling
towers in order to condense the steam into water, where it collects in the
hotwell. Makeup water is also typically added to the hotwell or condensate
storage tank. The mixture of makeup water and condensate is then transferred
by a condensate pump to the condensate polisher system for further treatment.
Although the makeup water should be high purity water, the condensate may
often contain some water hardness, corrosion products, and impurities,
usually resulting from a condenser leak. The polishing treatment is
necessary to prevent these corrosive products and impurities from building
up in the cycle and causing problems in the boiler (fossil fuel plants),
steam generator (nuclear reactor plants) or turbine.
A polishing treatment system is made up of combinations of filtration and
ion exchange, although some nuclear reactor treatments use membrane
technology. The filtration system must be adequate to effectively remove
insoluble corrosion products. The ion exchange is necessary for removal of
dissolved solids, although it can serve as a filter as well. Mixed-resin
demineralizers are typically used. The system used is dependent upon the
water requirements and characteristics.
After water exits the condensate polishers, it is usually delivered to high
and low pressure heaters, as well as a mechanical deaerator. These
components increase the temperature substantially and lower the dissolved
oxygen to acceptable levels. The water is now called feedwater.
Feedwater
The purpose of feedwater treatment in a power plant is to deliver a minimum
level of contaminants and corrosion products to the boiler or nuclear
reactor. It is considered to be the most important part of cycle chemistry.
The cycle chemistry control of feedwater can vary extensively depending upon
the type of boiler or reactor, operating pressure, and water characteristics
at a plant.
The boiler's purpose is to convert water into steam. Most power plant
boilers, regardless of operating pressure, are catagorized as either
once-through or drum-type units. The type of boiler greatly affects the
cycle chemistry control. A drum-type boiler has a drum where the water-steam
mixture is separated. Since the majority of contaminants are retained in the
water, they are removed from the cycle by blowdown. Condensate polishers are
not usually used in plants where drum-type boilers are used, although the
polishers are beneficial and should be used for optimal cycle chemistry.
Once-through boilers do not have a separating drum, so the steam/water
mixture continues out of the boiler directly to a superheater. This allows
impurities to affect components downstream of the boiler. Once-through
boilers will thus have more stringent cycle chemistry control and will
almost always utilize a condensate polisher.
Three separate types of feedwater treatment are typically used, primarily
depending upon whether the boiler is a drum-type or a once-through unit, and
secondly upon the existing metallurgy. If a drum-type boiler is used, either
phosphate or all-volatile treatment is used. In once-through units,
all-volatile treatment is utilized. However, a new type of oxygenated
treatment is also being employed in both types of boiler units.
In plants where a drum type boiler is present, a coordinated phosphate/pH
treatment is often utilized. This treatment is used to precipitate the
hardness constituents of water and provide alkaline pH control, which will
reduce boiler corrosion. This type of program maintains the sodium-to-
phosphate molar ratio within a narrow range of about 2.1 to 2.9. This ratio
must be maintained within this established control range to prevent
formation of phosphoric acid (ratio below 2.1) or free sodium hydroxide
(ratio above 2.9). The pH typically ranges anywhere from 8.4 to 10.6
depending upon the pressure of the boiler. Phosphate treatment offers
excellent buffering protection against potentially corrosive contaminants.
The objective of All Volatile Treatment (AVT) is to provide a high pH, high
purity, low oxygen environment to minimize the corrosion of metal surfaces.
The usual materials of construction in a fossil plant drum or once-through
boiler are carbon or low-alloy steel. In high temperature boiler systems
(greater than 400o F), a protective metal oxide layer of
magnetite (Fe3O4) forms on steel surfaces to prevent
corrosion. However, cooler temperature, steel surfaces in the steam/water
loop (primarily those in the condensate/feedwater cycle), remain active and
vulnerable to corrosion. The AVT objective is accomplished by adding ammonia
or morpholine to elevate the pH level to somewhere between 8.8 to 9.6,
depending upon the metallurgy. Mechanical deaerators and an oxygen scavenger
such as hydrazine or sodium sulfite are used to lower the dissolved oxygen
level to less than 7 ppb.
While elevated pH is the basis of AVT, a new trend in corrosion prevention
known as Oxygenated Treatment (OT) uses oxygenated ultrapure water to
minimize corrosion in the feedwater train. In plants using OT, oxygen is
added to the system to form a protective oxidized layer of hematite
(Fe2O3) on low temperature steam/water loop surfaces.
With OT for once-through units, an oxygen level of 30-150 ppb is monitored
across the whole plant cycle. The use of oxygen as a corrosion inhibitor
allows satisfactory operation over a large pH range; therefore, a reduction
in plant cycle pH down to a level of 8 to 8.5 (once-through boilers), or 9
to 9.5 (drum boilers), is possible. It must be noted that in order to use
OT, the system must have all-ferrous metallurgy downstream of the condenser.
In pressurized water reactors (PWR), there are two separate loops, a primary
and a secondary. The primary loop water is circulated through the reactor
itself to become heated. The heat from the primary loop is then transferred
to the secondary loop, which transforms this secondary feedwater into steam.
This place where the heat transfer takes place in the PWR is known as the
steam generator, and the water chemistry is very similar to that of a drum
type boiler. The other type of nuclear reactor, a boiling-water reactor
(BWR), has just one loop and the feedwater is converted to steam by
contacting the reactor.
Blowdown
When steam is driven off the boiler drum, the chemicals and impurities in
the water are left behind. The concentration of solids (scale-forming salts)
will increase with every gallon of makeup water, and sludge buildup in the
drum will reduce transfer of heat through the drum wall. Also, accumulated
concentration of solids increase the danger of carryover into the steam
lines. Solid material in the steam can damage steam driven equipment. To
prevent (or at least minimize) the concentration of solids in the drum from
building up as the steam is driven off, a small amount of water is
continuously removed. This is called blowdown. A similar type of blowdown is
done in nuclear reactor plants as well.
Since blowdown is typically inadequate, it is usually accompanied by
addition of chemicals to control precipitation or condition sludge. Blowdown
is wasteful since heated water is being effectively removed from the cycle;
therefore, it is important to properly control the cycle chemistry such that
blowdown is minimized. Current guidelines allow for operation with a minimum
of 1% (100 cycles) of blowdown.
Steam
The ultimate purpose of maintaining a good water chemistry program is to
ensure that highest quality steam is produced on a continual basis.
Regardless of whether a plant produces steam based on a boiler or a nuclear
reactor steam generator, the steam purity is essential. Steam purity for a
given system is dependent upon the intended use for the steam.
Considerations such as the type of boiler or reactor as well as the type of
turbine greatly affect the limits on purity, as do component type and
initial water purity.
Once the steam passes from the boiler or steam generator, it usually passes
into a superheater where it is heated above the temperature at which it was
produced in the boiler. This helps to improve the thermal range of the steam
cycle and reduce downstream condensation. The superheated steam is then
passed through the first turbine. The steam exiting this high pressure
turbine is then usually sent back to a reheat superheater, where the steam
is reheated to be sent to lower pressure turbine stages. Usually these lower
stages will consist of a single low pressure turbine or a combination of an
intermediate turbine followed by a low pressure turbine. After the final
stage, the steam enters the condenser, where it changes back to water.
Cooling Towers
In order to provide cooling water for the heat exchangers present in the
condenser, sample lines, and other parts of a power plant, a properly
maintained cooling tower must be present. Cooling tower cycle chemistry is
often misunderstood and thus neglected, although it remains a critical part
of a plant's efficiency. Even though the water from the cooling towers is
usually completely separate from that in the boiler cycle, proper cycle
chemistry is just as vitally important to prevent scaling, corrosion, and
microbiological fouling so that heat exchange is as efficient as possible.
Cycle chemistry in a cooling tower is always determined by the makeup water
available and the materials of construction. Each cooling tower will add a
variety of chemicals on a continual basis to ensure that heat exchange is
kept at a maximum level. In almost all cooling towers, blowdown is done on a
cyclical basis. A good cycle chemistry treatment will minimize blowdown and
makeup water intake.
Effluent water
Any water that cannot be reused is some part of the plant, typically from
the blowdown from the boiler and the cooling tower, will be discharged.
Environmental standards must be met for all water released from a plant.
Typically the dissolved oxygen must be raised to the parts-per-million (ppm)
level and the pH must be neutralized to levels somewhere between 6 to 9 pH.
Many plants are being designed for zero discharge. This means that no water
will be discharged. The water, whether from boiler or cooling tower
blowdown, will in some way be recirculated, usually to the makeup water
treatment system for the boiler cycle or occasionally for the cooling tower.
If zero discharge is the goal, this recirculated water will also typically
be monitored on a continual basis to determine water characteristics.
APPLICATION SAMPLING POINTS AND MEASUREMENTS
Makeup Water - Conductivity is almost always monitored continuously, as well
as pH, ORP, and sodium ion depending upon the components in the makeup
treatment system.
- Cation conductivity is measured in the makeup water storage tank
to ensure water integrity. Typically this water is at a minimum of 1
megohm-cm of resistivity (1 micromho/cm conductivity), with usual
limits being 5 to 10 megohms-cm resistivity.
- ORP may be monitored if some form of chlorination /
dechlorination exists, whether as a monitor of incoming water or as
a controlled parameter to protect some types of reverse osmosis or
deionization resins.
- Specific and cation conductivity is typically measured in
various places to determine efficiency of ion exchangers, softeners,
and reverse osmosis systems.
- pH or conductivity may be measured as part of the ion exchange
regeneration cycle.
- Sodium ion concentration may be measured at the inlet and outlet
of the ion exchangers to determine process efficiency and the need
for regeneration.
Condensate Water - pH, conductivity, sodium ion and dissolved oxygen are
normally measured.
- Specific and cation conductivity are typically continuously
monitored at the inlet and outlet to the condensate polisher. These
measurements are done to check the total dissolved solids level as
well the process efficiency, water purity, and need for regeneration.
- Dissolved oxygen is monitored continuously at the inlet and
outlet of the condensate polisher to detect air leaks.
- pH may be monitored continuously or periodically at the inlet
and outlet of the condensate polisher to monitor for process leaks
and to ensure that a scale-forming pH level does not occur.
- Sodium ion concentration is measured at the inlet and outlet of
the condensate polisher to determine process efficiency and the need
for regeneration.
- Specific and cation conductivity will be continuously monitored
after the condensate pump discharge to determine overall water
quality.
- Specific and cation conductivity are continuously measured at
the deaerator inlet to monitor water purity. Conductivity is also
usually measured at the inlet and/or outlet of the high and low
pressure heaters.
- Dissolved oxygen is measured at the inlet and outlet of the
deaerator to monitor the deaerator efficiency. It is also typically
measured at the inlets and/or outlets of the high and low pressure
heaters to detect air leaks.
- Conductivity is typically measured in condenser leak detection
trays and/or hotwell zones to ensure that a condenser tube leak is
detected significantly earlier than the condensate pump discharge.
Feedwater - Conductivity, pH, sodium ion and dissolved oxygen are measured
on a continuous basis to ensure that requirements for water entering the
boiler are met. Some of these measurements are also done for feedwater to a
boiling-water-reactor (BWR) or pressurized water reactor (PWR).
- Dissolved oxygen is measured in the final feedwater to ensure
that no process leaks have occurred, as well as for feedforward
control of any oxygen scavenger that may be used to lower the oxygen
level further.
- Specific and cation conductivity, and occasionally sodium, are
continuously measured in the final feedwater to guarantee that the
water meets the purity standards required for the boiler cycle.
- pH is measured in the final feedwater to control the pH level in
the boiler, preventing a scaling or corrosive condition.
Blowdown - Conductivity is measured to monitor the periodic or continuous
blowdown in the boiler or cooling tower.
- Specific conductivity determines the cycle of concentration,
used to determine the need for blowdown.
- pH is often measured to ensure that a scaling or corrosive
condition does not exist.
- Dissolved oxygen is often measured in blowdown water to detect
corrosive oxygen levels.
Steam - Steam sampling, whether saturated or superheated, is difficult and
therefore is often not done by many plants. However, obtaining information
about steam purity is useful to detect contamination in steam lines.
- Cation conductivity is often continuously measured in
superheated, saturated, cold reheat, and hot reheat steam.
- Sodium ion is continuously monitored in saturated steam to
ensure that excess carryover is not occurring.
Cooling Tower Water - pH, conductivity and ORP are normally measured in
cooling tower water treatment systems to minimize scale, corrosion and
biological growth.
- pH, typically controlled by sulfuric acid addition, should be
monitored to control scaling or corrosive conditions.
- ORP will be used to monitor the optimum amount of oxidizing
biocides, such as chlorine, bromine, or ozone, which are added to
cooling tower water to control microbiological fouling. ORP may also
be used to alert personnel of process leaks in the cooling tower
heat exchangers.
- Conductivity is used to determine cooling tower blowdown.
Effluent Water - pH and dissolved oxygen should be measured on a continuous
basis to ensure that environmental requirements are met.
- Dissolved oxygen is measured to guarantee that oxygen levels in
water meet environmental regulations. This may occasionally require
some sort of aeration, which may use the dissolved oxygen
measurement for control.
- pH should be measured to ensure that levels in the water are
safe for discharge. This may require neutralization, so the pH
measurement is also used for control of reagent addition.
HONEYWELL’S ANALYTICAL SOLUTIONS
pH Measurement
The 7082 pH/ORP
Analyzer/Controller offers a wide variety of advanced features in a reliable
instrument. The monoplanar front panel incorporates a user-friendly display
with specific word messages and offers a clearly labeled keypad with tactile
feedback. A solution temperature compensation feature compensates for pH
changes in the boiler water, referenced to 25° C. A variety of electrodes
and mountings are available, including two types specifically for high
purity water measurements.
Features
- Large digital display showing pH, ORP, or temperature
- Specific electrodes and mountings for difficult high purity water measurements
- Up to four alarm relays
- Up to three 4-20 mA outputs
- Unattended, automatic electrode cleaning and calibration
- Controls one or two reagents through current adjusting, pulse
frequency, or duration adjusting proportional outputs
Benefits
- Ideal for high purity water measurements where component life
and corrosion is dependent upon measurement accuracy
- Temperature compensation for electrode and solution changes
Conductivity / Resistivity / TDS Measurement
Using industry-accepted algorithms, the 7082
analyzer accurately compensates for conductivity changes with
temperature, making it ideal for a wide variety of boiler water
applications. The superior electronic design ensures reliable signals from
the cells over the full display range, allowing separation of cell and
analyzer by as much as 1,000 feet without reduction of accuracy. A wide
variety of conductivity cells with cell constants specified for individual
processes allow reliable, continuous measurements.
Features
- High purity water temperature compensation for neutral salts, cation / acid, ammonia, or morpholine
- Steam purity measurements
- Large digital display showing conductivity/resistivity, temperature, total dissolved solids (TDS), or calculated variables (% passage, % rejection, ratio, difference)
- One or two cell input
- Multiple outputs for transmitting up to three measured or calculated variables
- Up to four relays available
- Withstand pressures up to 250 psig and temperatures up to 285 ° F (140° C)
- Cells specifically designed for boiler processes to ensure maximum accuracy
- Rugged cell body available with various materials of construction, including stainless steel and polyethersulfone (PES), titanium and high density graphite
Benefits
- Temperature compensation specific to high purity water applications for improved accuracy
- Rugged materials of construction, reducing cell costs
- Flexible mounting assemblies, reducing installation costs
- Computing needs are streamlined with automatic computations for improved process results
Dissolved Oxygen Measurement
Honeywell's 7020 series
analyzer is unique in both technology and operation. The system combines a
patented equilibrium probe - unaffected by inert fouling or changes in flow
conditions - with a menu-driven analyzer/controller. Note that Honeywell's
equilibrium probe should not be used in BWR water where dissolved hydrogen
may be present.
Features
- Unique equilibrium probe technology with no internal maintenance and no flow dependence
- Temperature and pressure compensation
- Extensive probe and analyzer diagnostics, including data storage of dates and times of alarms and diagnostics
- Isolated outputs, alarm relay contacts, and PID control all standard
- Automatic air calibration/cleaning
Benefits
- Heavy-duty membrane - eliminates replacement requirements
- Reduced maintenance costs
- Accurate, reliable dissolved oxygen readings despite fouling and changes in flow rates
- Reduced costs for oxygen scavenger chemicals
Sodium Ion Measurement
The sodium ion
measuring system provides continuous measurement of sodium ion
concentration in various boiler water applications. This highly sensitive
system is composed of a microprocessor-based analyzer combined with a highly
sensitive sodium electrode with calibration facility and sampling system.
Features
- Sample conditioning (if necessary) using ammonia or an amine, depending upon pH levels
- Four SPDT alarm relays
- Two, three, or four decade logarithmic and bilinear output ranges
- Automatic calibration
- Automatic linear output range changing
Benefits
- Sodium level detection as low as 0.1 ppb
- Detection of sodium levels in ammonia-treated water without use of pH-adjusting reagents
- Two-stream sample switching
- Accurate measurements provided by sampling system, preventing similar ion interference
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