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Abstract 5 -124
Handling Fouling in Plant Cooling Water Systems
Any object left in untreated water will experience marine
fouling. Facilities with coolingwater (CW) systems are vulnerable
to serious operating problems with economicconsequences.
Macro-fouling costs industry billions of dollars a year and is
difficult andexpensive to control. Traditionally, stationary
facilities have used chemicals to reducefouling, but the Clean
Water Act requires strict discharge permit conditions.
Solutions to control macro-fouling require a comprehensive
approach that addressessystem design and implements site specific
control measures. Any viable system requiresa sound foundation
providing essential support. For CW systems, Silicon foul
releasecoatings are the best practical technology that is
economically feasible, environmentallysound, while minimizing
operating problems. This technology is available for
unrestricted, immediate use when economically justified by the
plant owner-operator.
Bruce Woodruff PCS Corr-Coat Consulting8486 Oakstone Cir.
Huntington Beach, CA 92646
1849 N. Prospect Ave. Lecanto, FL 34461
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Handling Fouling in Plant Cooling Water SystemsBruce Woodruff
PCS Corr-Coat Consulting
Background - Introduction
Any object left in fresh, sea or brackish water will within
hours experience marinefouling - the attachment of algae (seaweeds)
and various small marine animals. There isan accumulative build up
over time. This fouling can lead to serious operational andeconomic
consequences. The consequences include reduced speed and increased
fuelconsumption for ships, accelerated corrosion and increased risk
of storm damage on fixedstructures, and operational difficulties in
power plants caused by heat transfer reductions.
Almost all facilities with cooling water systems are affected
and vulnerable tomacrofouling. Power plants (both nuclear and
fossil fuel), steel mills, refineries, papermills, a variety of
manufacturing facilities, and municipal water treatment facilities
must
have a comprehensive plan to alleviate the problems associated
with this fouling. Theirgeographic location will dictate the
potential kinds of fouling organisms that could beinvading and
creating havoc and the growth rates in any specific system.
The Zebra Mussel and the Asiatic Clam are the most prominent
mollusks that infiltratefreshwater industrial cooling water
systems. Some of the prevalent kinds of foulingorganisms to
brackish and seawater cooling systems include a variety of
mollusks(mussels and oysters), barnacles, hydrozoans, bryozoans and
for the more tropicallocations sponges, tunicates, anemones and
tube worms. As larval and juvenile stagesenter the cooling system
they aggressively settle and accumulate onto the surfaces of
thecooling systems pipes, intake bays, screens, and waterboxes. The
constant supply of air
entrained water and microorganisms as a food source provide the
"ideal" environment ofcooling water systems to allow the
macro-organisms to flourish.
Many industrial and municipal facilities have incurred
incredible costs due to theclogging of water intake systems due to
fouling. It is estimated that Macro-fouling costsIndustry billions
of dollars each year. In short, power stations are frequently faced
withsignificant bio-fouling problems and have to address these
without measurable dischargeseffecting water quality. Effects on
the plants can be acute (such as a total or partial loss ofcooling
water), or chronic (such as increased turbine backpressure and
degradedcondenser performance).
The Power Plant CW System
Older power plants are almost always costal and are directly
cooled using seawater. Theolder inland power plants are typically
built on lakes, rivers, or have a waterway access.Newer plants may
have closed cycle cooling system where water is cooled using
largehyperbolic cooling towers or forced air cooling towers. Here,
only a makeup source isrequired for water and very little of the
water is discharged back to a watershed or ocean.
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Power plants have a number of systems that are designed to
handle macrofouling in theircooling water intake systems. The
waterfront is typically guarded by bar racks, the firstline of
defense. These restrict large marine life, tree limbs, coconuts,
plastic bottles, and
other flotsam from entering the inlet bays and doing system
damage. It is not uncommonto see a large logjam at the waterfront
of plants. This jam must be relieved on occasionto prevent
structural damage to the intake structure itself.
Log Jam at a plant inlet Bar Racks & Mobil Trash Rake
System
The second line of defense is normally a trash rake or traveling
water screen (TWS), orboth. This system manages smaller marine life
such as weeds, large shell, and small fish;diverting them from the
cooling water inlet system and bypassing them directly to theplant
outlet or discharge. The TWS system is normally located in the
inlet bay orcirculating water pump (CWP) suction pit.
Trash Rake System with plant bypass TWSs and CWPs above an Inlet
Bay
From the inlet bay, the water is suctioned into large
circulating water pumps (CWPs) whereit is pushed through
underground large diameter pipe or concrete flumes to the
condenserwaterboxes that sit underneath the steam turbine at the
plant. Often the distance from thewaterfront pumps to the plant
turbine and condenser waterboxes is hundreds of yards.
Afterentering the waterbox, the water is directed through tens of
thousands of small diametercondenser tubes (a tube is typically to
1 in diameter and from 30-50 feet long). This
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collection of tubes containing cooling water condenses the
turbine steam into condensatewater, which is again fed to the
boiler to make more steam. It is also fed to service water
heatexchangers (SWHXs) that cool plant auxiliary equipment.
Lightly Fouled Tubesheet Inlet Heavily Fouled Tubesheet
Inlet
Some newer plants and refurbished or retrofit older plant units
have additional rotatingscreen systems or micro-macro fouling
collectors in or just before the inlet waterboxes. Thisenables
removal and bypassing of smaller objects in the cooling water that
may plug tubeswhich can greatly affect plant efficiency. These
systems are very expensive, costing millionsof dollars and
requiring extensive maintenance. Additionally, larger and newer
power plantunits may have condenser tube cleaning systems. There
are many types, all of which aredesigned to keep the thousands of
condenser tubes free of silt, fouling, scale and shell foulingwhich
would hinder heat transfer or worse yet, cause a failure in a tube.
A single failure of a
condenser tube, one small hole or leak, will cause the plant to
be shut down due to its effecton boiler water chemistry. A drawing
of a typical power plant CW system is shown below.
By design the cooling water circuit system would seem to work
reasonably well, filtering outany harmful marine life and
protecting the condenser tubes from blockage or fouling; except
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we forgot one thing. There are literally thousands of square
feet of inlet bay and CW pipefrom the pump suction to the condenser
water box. This area is subject and susceptible tomarine life
attachment and growth. The conditions are perfect for abundance
here; nutrientrich waters free of chemicals and biocides. It is not
uncommon to see shell several feet thickin inlets bays and many
inches thick in pipes, flumes and waterboxes. It is also not
uncommon to have some of this growth fall off due to its own
mass and the drag of the CWsystem flow, and plug a condenser
bringing the plant off line. What went wrong here?
Quite simply, marine life consisting of weed, barnacle,
clamshell, mussels enters the systemas microorganisms or small
marine life and attaches to the pipe, flume or structure. Here
itgrows, thrives, and procreates. This fouling is almost impossible
to control. The shearquantity of water moving through the system
(hundreds of thousands of gallon each hour)make it impossible to
treat with chemicals without exorbitant expense; and
biocidetreatments are not permitted with any chemical discharge
whatsoever.
This uncontrolled grown of marine life throughout the internals
of the CW system has
disastrous effects on condensers and any final filtration or
separation systems that areinstalled. In failing, falling off under
its own weight, sheets of mussels, clam shells, byssalfiber thread
carpets, and other tube blocking debris make their way downstream
to collect inand overpower filters and to collect on the inlet
condenser tubesheet face, blocking tubes andrestricting heat
transfer.
316b Kill Reduction - Debris Mussel Byssal Fiber CarpetSteam
turbines can trip off line on high backpressures of steam caused by
the condenserblockage. At the minimum plant unit heat rates drop
dramatically as does plant efficiencyand power output. Operators
must take action and drop loads, decrease power, and cut offsome
CWPs to drop shell and temporarily remove the blockage. Then the
power is again
increased but the condition repeats itself. Maintenance crews
are called in and late at night,when the power is not in demand,
the plant is reduced in load and one of several waterboxesis
drained, opened and entered to get rid of collected shell and
debris. It is removed by thedrum full. The conditions of this work
are terrible as the plant is still on line and thewaterbox is hot,
well over 100 to 1200F and 100% relative humidity. Workers are at
risk ofheat stroke, cuts from sharp shell, and it is a
backbreaking, demanding task. In one smallplant on Tampa Bay in the
summer months, dropping shell was required every few hours and
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that night, seven 55 gallon barrels of shell were removed from
one waterbox. Each powerplant unit has from two to four waterboxes
making this work constant over time.
The growth and removal cycle is continuous until a plant outage,
when the bays, pits, pipes,flumes and waterboxes can be entered for
cleaning and marine life removal. This is also
hard and dangerous work. Anyone who has been in a drained pit or
pipe full of dead anddecaying life knows the stench. A variety of
methods are available to clean these areasincluding steam killing,
ultra high pressure water blasting, and the old tried and true
sledgehammer and straight hoe scraper methods. In choked systems
with heavy build ups, thework is outright dangerous, and many
hundreds of man-hours are required to remove manytons of buildup.
No one should be put up against the risks involved in this confined
spacework, which may include disease, infectious cuts and scrapes,
and breathing ammonia fromdecay. It is also seemingly a thankless
task, because once it is done, there is similar work todo the next
outage and the one after that, and the cycle repeats. So what good
did we do?
Is there a means to break this cycle? Of course, there are
several, but it takes time and
money to fix this problem and break this chain, especially the
first time. Will it be worth theinvestment? On the health and
safety aspects of the work alone the answer is yes. Of course,each
operating plant will have to look at the numbers and evaluate the
benefits and risks.But if plant efficiency, reliability and
availability are in any way encumbered by foulingpresently, the
answer should be to break the cycle because of these losses. In
addition, theanswer is that we will have to. About 550 power plants
nationwide, fall under a new federalmandate to account for the life
forms they trap and kill, then reduce that by up to 95 percent.
Whats Available for CW Systems
Power plants are stationary structure facilities and are subject
to environmental laws, rules
and regulations including the Clean Water Act (CWA) and Clean
Air Act (CAA). Permitsare required for all discharges in these two
areas as well as for any biocides, pesticides orwater treatments
used. Outlines of these restrictions and conditions are discussed
in latersections of this paper on anti-fouling and foul release
coating technologies. In short, for now,suffice it to say that the
foul release technology is available for immediate and
unrestricteduse as required in the power plant industry. The use of
foul release technology only has tobe economically justifiable for
the plant owner-operator.
The technology is expensive on first application simply because
the CW system itself wasnot designed and maintained with coatings
initially, as perhaps it should have been. We cannot really fault
the designers here, as our competitive economic system demands the
least
initially expensive construction to compete with other power
plant builders and operators. Sothe fault, if any, belongs to the
short sightedness of the plant owners.
Fouling will latch on to and adhere at the point of least
resistance to its attachment. Thiscould be an attached shell, in a
concrete bughole or crevice, in a steel corrosion pit or on arust
tubercle. Now, this marine life has both an anchor and a home where
it can live,thrive, grow and propagate until its lifecycle is over.
We are already well aware of the futurecatastrophe that lies in
wait here.
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If we could start with a new plant, new construction with fresh
concrete with patchedbugholes, properly finished and sealed, and
properly coated steel; the foul release coatingtechnology is not
expensive. Costs should not exceed $6-8/ft2. However, we are faced
withan operating plant with concrete waterfront pits or bays, steel
structures, and concrete, steel,
or fiberglass pipe that was typically not designed with or for
coatings. In the few caseswhere steel with coatings was used, the
conditions now are probably far deteriorated to theextent that this
will also have to be addressed. Fouling is present and it will need
to beremoved and the concrete and steel must now be cleaned and
decontaminated, and repaired.
Foul release technology quite simply resists or rejects this
first attachment by means of itssurface tension. What is required
is a smooth, bughole free surface to which the siliconetechnology
can be applied. To create this surface we must clean and
decontaminate the oldsurface and apply a base coat (normally an
epoxy or thick film polyurethane that is suitablefor immersion
service) that fills any abnormalities and gives a smooth surface.
This is easyon new construction with concrete surfaces being the
most difficult to deal with, and most
difficult on existing, in-service surfaces where almost
everything needs restoration.
In fairness to the foul release technology available, the
refurbishment and repair costs shouldbe separated from the
economics of evaluating the viability of the silicone system
itself. It isin essence a one time charge and will not need to be
redone in large measure again. Anyeconomic pay back analyses
evaluations must take this into account and a separate line
itemshould be included. The refurbishment coating or base coat
restoration alone will greatlyreduce fouling attachment in and of
itself. However, when attachment occurs to this layer, itwill not
be easy to dislodge. Since the cost of this cleaning and
restorative base coatapplication is 3 to 5 times the cost of the
silicone system and topcoat, and because thesilicone will protect
this basecoat investment and extraordinarily inhibit fouling
attachment
and greatly promote fouling release, the silicone layers must be
applied.
The silicone foul release technology is normally good for 5 to
10 years dependent on systemconditions prior to the necessity for
renewing its effectiveness. Like all coatings and mostother man
made materials, there is a wear out and degradation of properties
in the siliconelayer over time. The silicones surface tension and
release effect dulls and diminishes, andit must be refreshed or
stripped off the base coat and reapplied to renew the
coatingseffectiveness.
This renewal or reapplication of the silicone topcoat in 5 to 10
year increments on the bays,pits, pipes and structures in the CW
system fits in well with most power plant planned major
turbine outages. The system should be inspected annually or
during planned shutdowns, andbe maintained during these
inspections. The maintenance would consist of low pressurewater
washing or wet broom brushing and sweeping away any weed, small
barnacle, orminor shell debris as necessary. If attached, the
attachment will be weak and should beeasily removed. This work
should require less than 1/10th to 1/100th the man-hours
expendedduring a typical outage before the foul release technology
application. Over time, theattachment will become more difficult to
remove and will require more man-hours. This
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information will tell operators and maintenance personnel when
Silicone refreshmentrecoating is required.
Without the attachment and sheeting off action, there will be
little or no growth within thesystem itself. All marine life larvae
will be small enough to pass directly through the
system. Under this scenario, there will be no typical
operational or availability incidentscausing loss of power or
generation revenues, no dropping shell incidents, no night crew
tounload shell, and lessened risk to maintenance personnel. This is
a much better and moreprofitable operations and maintenance
scenario than that prior to application of the foulrelease
technology.
Fouling Technology Using Coatings
The two main technologies to prevent or minimize fouling today
are antifouling and foulingrelease coatings. They will be discussed
separately. The rules for ships and structures differ,but the
differences are diminishing greatly, especially recently. It must
be noted that the
Antifouling technology was never available or permitted for
stationary structures such aspower plants, as they were known to
pollute the marine environment and threaten watersupplies with
persistent toxins.
The Clean Water Act gave the Environmental Protection Agency
(EPA) authority to regulatewater quality standards and criteria for
surface and navigable waters, and limit all pollutantsby permit.
The acronyms that have developed in recent years from the many
regulations are aringing testimony to the extent that these rules
have populated. We have bioaccumulativecontaminants of concern
(BCC), environmental effects analysis (EEA), federal
insecticidefungicide and rodenticide act (FIFRA), toxic pound
equivalent (TPE), water quality criteria(WQC), and uniform national
discharge standards (UNDS) to name a few.
Anti-Fouling Coatings & the Maritime Industry - Ships
Historically, marine antifouling paints have used compounds
toxic to marine organisms as ameans of combating fouling. The
principle behind antifouling coatings is that activeingredients
incorporated in the paint film are made accessible via a
combination of chemicaland physical action from the surrounding
water. Ships have employed anti-fouling paintsthat were designed to
slowly leach biologically toxic control agents into the water. In
the pastthese toxins included lead, copper and tin. A stay off me
Im poison approach.
In more recent ship coatings, the toxin release rate is
controlled by Rosins or controlled
depletion polymers (CDP), ablative self-polishing copolymers
(SPC), or hybrids of the twotechnologies that gave a controlled
release of tributyltin (TBT). These toxic coatings haduseable
service live ranges of 3 to 5 years. Most recently, TBT became a
victim of its ownsuccess as it was so widely used that it
accumulated in the marine life ecosystem and toxic,persistent
adverse effects were detected. Years ago, the International
Maritime Organization(IMO) drafted a treaty under which the
application of TBT-containing antifouling coatingswas banned, but
to date, not enough countries (16 countries of the 25 needed) have
ratifiedthe treaty to bring it into full effect. However, the major
marine coating manufacturers have
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voluntarily not supplied tin-based anti-fouling coatings to end
users for several years. So thelegal situation today varies from
one country to another, with some countries banning the useof TBT
on only small pleasure craft, and the European Union (EU) in effect
applying theIMO regulations unilaterally.
Advanced TBT anti-fouling coatings have a discharge TPE of
450,000 lb-equiv/yr and have1 identified BCC, although the biocide
is considered non-persistent. Advanced Coppercontaining
anti-fouling coatings have a discharge TPE of 220,000 lb-equiv/yr
produced bypersistent biocides, which results in a WQC exceedence
and contain two known BCCs.For ships, to keep the hull clean you
don't actually have to kill anything, just stop it attachingitself
and reproducing. In this way, silicone-based coatings can provide
non-toxic protectionfor fast-moving craft. But for most ships,
copper combined with organic biocides is today'sobvious replacement
for TBT. Essentially, in todays technology, TBT free
anti-foulingpaint means Copper is present. Copper is certainly less
toxic than TBT, but experts predictthat alternatives to Copper use
will ultimately have to be found. At costs estimates of over
$4million to undertake the testing required for anti-fouling
registration who will take the risks?
At present, for ships, the coatings industry has adopted a
diversification of technologies:making copper effective at lower
leaching rates, using toxicants derived from naturalresources,
providing foul release Silicone slippery hulls to which marine life
cannot cling,and developing more hydrophobic (and more hydrophilic)
binder systems. As larger andlarger ships ply the oceans, the cost
of removing them from the water to replace antifoulingcoatings
rises, and the demand for extended coating lifetimes therefore
grows. As in manyother areas, the combination of environmental
regulations and end-user demands means thatchanges are necessary.
The replacement of TBT coatings was not an easy task and
thereplacement of copper, which will soon come, will not be easy
either.
The cost comparisons of application and maintenance of the
silicone foul release coatings totypical copper ablative coatings
are very similar. The silicone materials cost more initiallyand the
application (labor) is slightly more expensive as well. However,
the silicone foulrelease maintenance interval is longer and waste
disposal charges are less, creating anequivalence of systems that
average $9 - $12/ft2 applied.
Fouling & Power Plants Foul Release
Industrial cooling water systems most often provide the "ideal"
environment for macro-organisms to grow and accumulate. During the
1980's the Zebra mussel achieved notorietywhen it was introduced in
the Great Lakes from the ballast water of ships originating
from
Europe. Since then Zebra mussels have been rapidly infesting and
flourishing in manyfreshwater lakes and streams. Power plants and
industrial facilities have experienced theaccumulation of Zebra
mussels within their cooling water systems by as much as
500,000mussels/square yard. This degree of fouling by the Zebra
mussel is analogous to other kindsof fouling organisms that
continue to plague the operation and function of industrial
maincirculatory, service-related, and safety-related cooling water
systems.
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Biofouling is difficult and expensive to control. Historically,
for stationary structures,chemical controls such as chlorine gas or
sodium hypochlorite have been utilized.Traditional methods for
controlling bio-fouling of water intakes depended on the use
oftargeted chlorination. We need to discontinue the use of chlorine
kills since chlorine incombination with humic substances generates
carcinogens such as trihalomethane. Other
chemicals are available but the large volumes of cooling water
that need to be treated requirecostly quantities, even at low
permitted concentrations.
Power plants and other industrial facilities are under continued
pressure to optimize wateruse and wastewater treatment while
improving operating efficiency, reducing costs, andensuring
environmental compliance. Increasingly stringent discharge permit
requirements fortrace metals, nitrogen compounds, biocides, and
other contaminants, as well as watershortages and changing aquatic
protection and water use regulations, are among thechallenges
facing facility owners. Typical discharge limits are zero, greatly
increasing therisks involved in using any chemicals. Specific
regulatory developments driving the todaysresearch include ramping
down of water quality criteria in receiving waters, loss of
dilution
credit for dischargers to running waters, new 316(b) rules for
fish protection, TotalMaximum Daily Loads (TMDL's) for managing
total loadings to watersheds, and limits onwater use, especially
for new facilities. Many new or repowered facilities are being
forced toconsider or adopt water-conserving cooling options as a
permit condition.
Section 316(b) of the CWA (40 CFR 125) provides that any
standard established pursuant tosection 301 or 306 of the CWA and
applicable to a point source must require that thelocation, design,
construction, and capacity of cooling water intake structures
reflect the besttechnology available (BTA) for minimizing adverse
environmental impact. It is applicablefor new facilities and
existing power generating facilities that have the design capacity
towithdraw at least fifty (50) MGD of cooling water from waters of
the United States and use
at least twenty-five (25) percent of the water they withdraw
exclusively for cooling purposes.
A facility may choose one of three options for meeting best
technology availablerequirements under this proposed rule. These
options include demonstrating that the facilitysubject to the
proposed rule currently meet specified performance standards (less
than 0.5ft/sec at intakes with fish mesh filtering); selecting and
implementing design and constructiontechnologies, operational
measures, or restoration measures that meet specified
performancestandards (reducing fish impingement kills by 80-90% and
marine life entrainment killswhich include shell by 60-90%); or
demonstrating that the facility qualifies for a
site-specificdetermination of best technology available because its
costs of compliance are eithersignificantly greater than those
considered by the Agency during the development of this
proposed rule, or the facility's costs of compliance would be
significantly greater than theenvironmental benefits of compliance
with the proposed performance standards. Theproposed rule also
provides that facilities may use restoration measures in addition
to or inlieu of technology measures to meet performance standards
or in establishing best technologyavailable on a site-specific
basis.
The EPA expects that this proposed regulation would minimize
adverse environmentalimpact, including substantially reducing the
harmful effects of impingement and entrainment,
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at existing facilities over the next 20 years. As a result, the
Agency anticipates that thisproposed rule would help protect
ecosystems in proximity to cooling water intake
structures,preserving aquatic organisms and the ecosystems that
inhabit in waters used by cooling waterintake structures at
existing facilities.
What is also relevant and made clear by these rules (phase I new
facilities and phase IIexisting facilities) is there will be a
phase III and possibly IV, and further measures will berequired.
These measures will probably go beyond fish kill reduction to
include other marinelife as well. EPRI research in this area has a
goal to find, develop, test and implementcontrol technologies to
reduce the costs associated with macrofouling to eliminate reliance
onchemical treatments and mechanical cleaning and avoid negative
impact on the environment.
Political and environmental pressures are growing concerns in
our world. Bioethics concernsitself with all living organisms and
non living resources in the biosphere, yet moderndevelopment
demands electrical energy. This is seemingly a conflicting
situation. Theethical dilemma is the human need to produce more
power and at the same time protect other
living organisms. In other words, rather than kill marine life
we should safeguard it, and letit travel through the system without
harm.
Silicone Foul Release for Power Plants
The Silicone foul release coatings are environmental friendly
paints that utilize a physicalrather than chemical approach to
solve the fouling problem. Advanced, layered siliconepolymers have
a unique surface chemistry creating a surface to which fouling can
not easilyadhere. The effect is due to the water-repellent physical
properties of the surface, instead ofthe coating exerting a
chemical effect on the surroundings. Any fouling attachment is
madedifficult and the difficulty increases with water flow or
velocity. Also, once attached, the
bond is weak and the coating simply releases the fouling
organisms with help from themotion of the water. There are no toxic
metals, so these coatings provide an environmentallysound fouling
solution. Because of this, Silicone coatings have been ruled exempt
fromreporting under FIFRA (Public Law 95-396).
The principle behind fouling release coatings has also been
known for over 30 years.However, exploitation as non-stick fouling
prevention has only recently been advanced.The new silicone
coatings have demonstrated more than acceptable performance
whenapplied to a variety of platforms in freshwater and marine
environments. The characteristicsevaluated included easy
application and adhesion to substrates, durability, ease of repair,
andability to easily remove with a water jet any fouling that did
occur. They have been applied
in many locations in the last 10 years and have met all local
environmental and occupationalhealth standards. Foul-release
coatings have a discharge toxic pound equivalent (TPE) ofzero and
are unlikely to result in any water quality criteria (WQC)
exceedence, and containno unidentified bioaccumulative contaminants
of concern (BCC).
After much testing, the Diablo Canyon Power Plant now uses
Silicone foul release coatingsin conjunction with intermittent
injection of proprietary chemicals and saves millions ofdollars
annually. Here, Silicone coating systems proved to be both
environmentally
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acceptable and serviceable for over 7 years. Arkansas Nuclear
One and Duane ArnoldEnergy Center use silicone coatings as
proactive measures to inhibit zebra musselcolonization on pumps,
trash bars, traveling screen frames, and intake pits. The
fullyburdened cost to apply coatings at Diablo ran approximately
$40/sf for 10,000 sf coverage,while costs were less at Arkansas and
Iowa facilities.
These improved biofouling control strategies at these and other
power plants have savedthousands in labor; and millions in power
replacement costs and the makeup for lost revenue.It has also
deterred operational impacts caused by aquatic pests and
Biofouling. The use ofsilicone coatings in these systems have paved
the way for longer fuel and turbine overhaulcycles that are
necessary for nuclear and conventional plant facilities to remain
competitivein the next century.
Concerns
There are two major concerns with this technology. One is they
are slippery and it is difficult
to walk or even stand on a coated floor, so this can be a safety
concern. This is normallyaddressed by rolling out hard rubber
runners or plants dont coat a narrow center walkway.Secondly, over
time the flexibility and release character of a Silicone fouling
release systemwill slightly decrease. This flexibility can be
renewed by applying a new layer of freshtopcoat on top of the old
topcoat, making it possible to operate for 10 years with only
3coating layers applied on the anticorrosive coating. It must also
be mentioned that there aresome concerns have been raised over the
silicone oil that is slowly released to the waterenvironment over
time.
Summary
Electric generation at power facilities across the U.S. is
frequently interrupted in order tocontrol or remove nuisance
species that proliferate in cooling water systems.
Uncontrolled,this fouling can quickly block flow in piping or
detach and hinder heat exchange. In the past,typical controls
ranged from massive injection of chemicals, such as chlorine,
laboriousmanual scraping, recycling of waste heat, or use of toxic
coatings. Our goal as an industryshould be to find, develop, test
and implement control technologies to reduce the costsassociated
with macrofouling to eliminate reliance on chemical treatments and
mechanicalcleaning and avoid negative impact on the environment.
The Clean Water Act is leading theway here.
Macrofouling costs industry billions of dollars each year. These
costs are associated with
plant shutdowns, reduced operating efficiencies, maintenance
expenses, replacement ofequipment and other costs associated with
controlling the fouling organisms. To overcomethe deleterious
side-effects of many of these methods, new techniques such as
Siliconecoatings have evolved to meet environmental, regulatory,
and economic concerns.
In addition to use at power plants, successful implementation of
new foul release coatingtechnology could substantially reduce
operating costs for the U.S. Department of Defense aswell as U.S.
maritime industries. An effective, environmentally benign coating
would reduce
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naval fuel costs by 10 to 15 percent ($35 million to $50 million
a year) with additional costsavings from reductions in dry docking
frequency, remediation of polluted harbors, anddisposal of
hazardous paint waste.
Solutions to control macrofouling is best achieved with a
comprehensive approach that
considers the design of the cooling system, recommends various
control measures, monitorsthe effectiveness of the controls and
addresses environmental requirements. There is adiverse range of
methods to consider, including mechanical, physical, chemical,
coatings,thermal, sonic, electrical, etc. Choosing the best
practical technology that is economicallyreasonable, provides a
return on investment, and meets environmental requirements tends
tobe site specific for each particular facility. As with any viable
system there is a backbone,something giving needed and necessary
support. For the CW system of power plants andnow for ships at sea,
this backbone should be Silicon Foul Release Coatings.
On a typical power plant, manual cleaning will cost from $20,000
to $100,000 (averagecleaning rates are 1 Man-hour/linear foot) and
would average a 15,000 KW penalty.
Installed coatings would range from $30,000 to $70,000 and 5-10
year refresher coatings$2,000 to $5,000 or about 1/10th to1/20th
the typical cleaning costs. First time installationcosts will range
from $10 to $40/ft2, dependent on the condition of the system
beingaddressed and the amount of refurbishment and repair to build
a smooth base system. For theSilicone coating system itself,
typical material costs are from $2.25/ft2 to $4.00/ft2 and
laborruns from $2.00/ft2 to $3.00/ft2. System costs for a 5 to 10
year maintenance recoating costsshould run around $10-$12/ft2 or
less.
Do these Figures make sense for your CW system fouling
problems?
Silicone Foul Release Coating Test Panels after Immersion
Service
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References
1. EPRI, Service Water System Corrosion and Deposition
Sourcebook, TR-103403,Puckorious & Associates, 12/93.
2. ASME Press, Steam Surface CondensersBasic Principles,
PerformanceMonitoring, and Maintenance, Richard Putnam, 2001.
3. The Economics of Regular Condenser MaintenanceReturn on
Investment Analysis,White Paper, Richard Putnam, Conco Systems,
post 2000.
4. HEI, Standards for Steam Surface Condensers,Ninth Edition,
1995, Heat ExchangerInstitute.
5. The NALCO Guide to Cooling Water Systems Failure Analysis,
Harvey Herro andRobert Port, McGraw-Hill, 1993.
6. Corrosion Atlas, Evert During, Elsevier, 1988, Association of
Industries andOrganizations for Energy and Environment.
7. Fouling during the use of Seawater as a Coolantthe
Development of a User Guide,
2003 Conference on HX Fouling & Cleaning, Fundamentals &
Applications, SantaFe, NM, Pugh, Hewitt, &
Muller-Steinhagen.
8. Fouling in Cooling Systems Using Seawater, Item 03004,
Engineering Sciences DataUnit, ESDU International Ltd, London, UK,
2003.
9. Optimize Heat Exchanger Cleaning Schedules, ODonnell, Barna
& Gosling, AICHE,CEP, June 2001.
10. Progress in Offshore Coatings; Mike Mitchell, Akzo Nobel11.
Factors that Influence Elastomeric Coating Performance; D.E. Wendt
et all,
Biofouling, 2006.12. Environmental Effects Analyses Report: Hull
Coating Leachate, Naval Sea Systems
Command and Office of Water-EPA, August 2003
13. Foul Release Coatings: Past, Present and Future, Raouf
Kattan, Marine CoatingsSupplement, JPCL 2/2006.
14. Performance and Effectiveness of Non-stick Coatings in
Seawater, B. Watermann etall, Biofouling 11:101-118.
