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Paratherm
News
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Spring 2000
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Useful information
for professionals who use heat transfer fluids for precise
uniform process temperature control
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Fluid
Fine Tunes VOC Heat Recovery
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 It
takes arresting design and lively colors to move consumer
goods packaged in paperboard boxes from supermarket shelves
to shopping carts. The Jefferson Smurfit plant in Stone
Mountain, Ga., should know. It prints tons of eye-catching,
high consumer appeal paperboard annually.
The paperboard is run through eight different presses, each
with a different ink or coating. Approximately 450 cartons
are converted every minute on 55-in.-wide web presses. To
avoid smudging, the inks and coatings printed on each pass
must be dried almost instantly.
A year ago, the plant redesigned and improved the process
whereby the solvent-laden exhaust gases from its printing
presses provide the energy required to heat the dryers.
A heat recovery process designed by Thermo Wisconsin using
Paratherm heat transfer fluid generates about 85 percent of
the hot air needed to dry the printed paperboard.
Organic solvents facilitate the high-speed drying of the
inks and coatings used by JSC, but federal and state
regulations limit the release of VOCs to the environment.
The best solution for JSC is to burn them.
The system starts with the ductwork at the top of the eight
printing units designed to capture the VOC-laden gases and
send them to a Thermo Wisconsin Titan recuperative thermal
oxidizer (Model 2270). The 150°F incoming gases are
preheated to 1,000°F by the primary heat exchanger. At
that point, they pass through the burner where processed
VOCs and natural gas are used to increase the temperature of
the gases to the desired combustion temperature. Once VOC
oxidation is complete, the gases are returned to the primary
heat exchanger at 1,400°F to preheat newly arriving
VOC-laden gases.
The clean air then leaves the oxidizer and enters an
air-to-oil heat recovery coil, which extracts energy from
the clean oxidizer exhaust gases and uses it to heat thermal
oil. The thermal oil is then returned to the process dryers,
supplying nearly all of the heat required.
JSC selected Paratherm NF® as the heat-transfer fluid
for the new system because of its environmental and safety
characteristics. "We did not want a big clean-up problem if
there was a leak or spill," says Melvin Johnson, plant
engineer.
When the VOC capture system was designed by Thermo
Wisconsin, the physical properties of the NF fluid were used
to calculate heater size, pressure drop and other system
design considerations. The ink drying application required
heat-transfer fluid heated to 400°. The NF fluid is
"nonfouling" and will not cause hard carbon formation to
build on heated surfaces - even when overheated. Moreover,
it reportedly has one of the lowest viscosity ratings of any
high-temperature heat-transfer fluid. This becomes
increasingly important when the primary heat-transfer fluid
loop is a long one - such as at JSC.
Johnson says the Paratherm NF® fluid is performing well
and passed the company's regularly scheduled testing and
evaluation with consistently high marks.
A Thermo Wisconsin oil economizer is installed in the stack
of the thermal oxidizer. When supply temperatures fall below
required levels, reserve is provided by a fully modulating 6
MM Btu/hr thermal fluid heating system.
All temperatures are controlled and monitored at each press
by CNC controls outside the pressroom. The air heated for
the drying operation is drawn from ambient air in the
plant.
Return to
page index
From
Converting Magazine, November, 1998.
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Recommended
Hot Oil System Components
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 In
designing and constructing a thermal oil system, attention
must be paid to the selection of appropriate components. If
care is not taken, poor operation, system failure and fires
can result.
Pipe
Welded and flanged throughout. Specify schedule 40 ASTM A
106 Grade B seamless carbon steel tubing. We strongly
recommend the use of materials and methods to minimize entry
of weld spatter and slag into the pipe, and to assure strong
and leak-free welds. Pipe should be free of mill scale,
welding flux, quench oils and lacquers.
Note:
Threaded connections are NOT
recommended.1
Do
NOT use copper or copper bearing materials in hot oil
systems.
Flanges/Fittings
Must be rated for 600°F (316°C) service. For
optimum service we recommend 300 lb. forged steel, 1/16"
raised face, schedule 40 bore (ASTM-A 181).
Studs/Nuts
Continuous threaded, alloy steel (ASTM A 193, Grade B7),
with heavy hex nuts (ASTM A 194, Grade 2H).
Gaskets/Packings
Flange gaskets: Spiral-wound type
(FlexitallicTM,
Garlock FlexsealTM,
or equal).
Valve stem packing: Rings of die formed graphite foil
(GrafoilTM
PalfoilTM
or equal).
Pump packing: End (non-extrusion) rings of braided carbon
yarn (PalmettoTM
#1585, GarlockTM
#98 or equal), center (sealing) rings of die-formed graphite
(GrafoilTM,
PalfoilTM
or equal).
Elastomeric O-Rings/Seals
For service to 400°F (204°C): Fluoroelastomer
(VitonTM,
FluorelTM)
For higher temperature service, specify perfluoroelastomer
rubber:
To 450°F (232°C):
ChemrazTM
or equal.
To 480°F (249°C):
ZalakTM
or equal.
To 600°F (316°C):
KalrezTM
or equal.
Insulation2
2" thick 900°F (482°C) rated cellular glass
(Pittsburgh-Corning FoamglasTM
or equal). Heat loss value not to exceed 80 BTU/ft.
Valves
300 Ib cast or forged steel, or nodular (ductile)
iron3
rated for 600°F (316°C) continuous service
minimum, with steel or stainless steel trim
(LunkenheimerTM
1110-W1 or equal; WorcesterTM
4446XM or equal ball valves-- specify for thermal oil
application). For optimum service, bellows valves may be
considered (ARITM
or equal).
Note:
Install valves stem sideward
2
Pumps
Centrifugal: Cast carbon steel, carbon/tungsten carbide
metal bellows mechanical seals (Dean
BrothersTM
R-400 or equal); magnetic
drive--KontroTM,
DickowTM
or equal, “canned” (Sunstrand or equal). Positive
displacement: Alloy steel,
(VikingTM
Pump Division or equal).
Flexible connections at inlet and outlet should be used.
Pressure Gauges/Thermometers
Ratings to 100 psi, 650°F (343°C). Temperature
range of 300°F to 600°F; thermometers should be
calibrated to provide accurate readings in this range.
Expansion Joints
We suggest you provide for an expansion growth of 4" per 100
ft. minimum. Both loops and joint expansion devices are
acceptable. Either must be high-temperature rated and must
be considered part of the piping system.
Strainers
While many systems are supplied with 60 mesh mechanical
screens (casings of forged or cast steel), we generally
recommend 20 mesh for 1/4" to 3" pipe, and .045"
perforations for 4" diameter pipe and above.
Strainer
Removal
Note: In new
or significantly remodeled thermal fluid systems, once the
"logs" are filtered from the system, many start-up
technicians remove inline strainers entirely. They
do this to eliminate restrictions that would reduce flow to
the heater(s). Reduced flow to the heated surfaces can be
the cause of severe fluid overheating and possibly even
subsequent system damage.
Sealants
Customers report satisfactory service with
LoctiteTM
PST to 400°F, and Fel ProTM
HPS Sealer and Jet
LubeTM
TFW to 600°F. For permanent installations, satisfactory
service has been reported with
X-pandoTM.
Flow Protection
Most systems utilize a pressure differential switch to
provide a method of shutting the system down when fluid
flows drop below set limits. Another method used by some
manufacturers is to provide flow switches which control
flows independently through each branch of the heater.
Some systems are equipped with flowmeters in addition to the
pressure differential switches. While this is an acceptable
"belt and suspenders" technique, if the heat transfer fluid
deteriorates, flow meters can provide false readings.
These false readings can result from significant changes in
the fluid's physical characteristics that occur with thermal
degradation and normal aging.
Notes:
- Contractors must
apply all national and local codes for thermal
applications.
- Thermal heater room
must be provided with a 2-hour fire rated enclosure.
- Full pump capacity
must be maintained at all times when heater is in
operation.
1.
Due to the expansion and contraction of components in the
typical thermal oil system, and the low viscosity, high
lubricity and low surface tension of heat transfer fluids,
threaded joints and compression fittings will often leak
regardless of the type of sealant employed. We suggest that
you back (or seal) weld all threaded
connections.
Return to
Article
2.
Hot organic heat transfer fluid permitted to wick through
porous insulation will oxidize and decompose at system
temperature. This oxidation process creates extra heat.
Confined within the insulation, the heat has little chance
of escaping. Temperatures within the insulation can rise
dramatically, and in some cases will exceed the autoignition
temperature of the heat transfer fluid. With the entry of
fresh air, there is a hazard of fire (spontaneous
combustion.)
Repair all leaks,
and replace oil-soaked insulation immediately. Mount all
valve stems facing sideward, and leave potential leak points
un-insulated.
Return to
Article
3. Ductile
iron only. We do not recommend the use of cast iron in
thermal oil systems.
Return to
Article
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page index
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Ideas
for a Cleaner World
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At the
office
If
you're in charge of purchasing office supplies, choose
stationery and other office supplies with the maximum
post-consumer recycled content available, at least 20%. And
buy the lightest-weight paper possible for the job.
Publish or distribute documents electronically wherever
possible. If you have a web site, make your publications
available for viewing and download. Assemble e-mail lists
and send an e-mail version instead of hard copies of
publications. An added benefit is that e-mailed publications
can readily be distributed by the recipient to additional
recipients, thereby easily spreading your work.
If more than one person needs to look at the same document,
when possible, place a routing slip on the document instead
of making copies.
Ask for cleaner, greener printing. Tell your printers you
want a product with minimal environmental impact and work
with them to design it. Ask them what they are doing to
minimize air and water pollution, energy use, and chemical
waste. The more printers hear about your concerns the sooner
they will make improvements.
For more ideas on steps to conserve forest resources, log on
to: www.edf.org/pubs/Brochures/BuyRecycled/b_labels.html
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Paratherm's
Web Site Makes Top Ten List
In Nationwide Study and Awards Program
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Paratherm Corporation
has one of the 10 best-designed Web sites among mid-market
manufacturers, according to a nationwide study and awards
program conducted by RSM McGladrey, Inc.
RSM McGladrey is one of the largest accounting, tax and
business consulting firms in the U.S., and is a recognized
authority on Web site design, presentation and usage.
McGladrey recently conducted the Outstanding Web Sites
Mid-Market Businesses Study to identify industry Web sites
which reflect excellence in content, technique, and
execution. The study and awards program were co-sponsored by
AT&T and the National Association of Business
Manufacturers.
For the first annual Outstanding Mid-Market "Manufacturing"
Web Site Awards, judges reviewed the web sites of nearly
1,000 manufacturers. In judging the web sites, they
evaluated how well the sites met criteria in five major
categories considered crucial to developing and maintaining
an outstanding presence on the Web. The categories are
information, customer service, design and layout, quality,
and connectivity.
Paratherm's Web site (www.paratherm.com)
successfully meets the study's criteria, in part, by
ensuring easy accessibility and convenience for the user,
including such areas as download time. The Web site judges
deemed the information provided on Paratherm's Web pages as
timely, accurate and substantial in the quality of its
content.
Paratherm's Web site includes comprehensive product
specifications, technical data comparing Paratherm's heat
transfer fluids to competitive products, user benefits,
safety and maintenance tips, company news and case
histories, company history and other information. The Web
site's design allows for seamless navigation to any desired
point of reference. Interactive tools are also available to
the user, and purchases of heat transfer fluid can be made
immediately on-line.
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Heat
Transfer Fluid Tips
(Continued
from previous "In The Loop")
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Leak
Testing/Prevention
Pressurize the system
with inert gas and use soap bubble fluids at potential leak
points. Heat transfer fluid can leak through gaskets, seals
and packing if they're not properly installed.
Draining Your
System
Bring the oil temperature up
to about 225°F, and circulate the fluid until you are
assured of thorough mixing. At this temperature the fluid
will be less viscous, and many solids will be suspended.
Thoroughly drain using valves at the system's low points. As
the fluid drains, it's best to observe what comes out. If
you see chunks of carbon and other solids, you should
consider flushing with the heat transfer fluid you intend to
use. Call us for additional information.
Note: We suggest that you consider cleaners other than
water-based types. Water is difficult to remove, and can
itself cause corrosion.
Charging Your System
Connect a small positive displacement pump to a system
low-point valve. A convenient place to fill is through the
blow-down valve which is many times located on the strainer.
The strainer is usually located upstream of pump suction.
Bottom-filling can substantially reduce the entrainment of
air, a common cause of both pump cavitation and fluid
oxidation. And, bottom-filling allows the system to vent
normally as the fluid enters.
You may wish to consider purging the system with inert gas
prior to charging. Inert gas forces the air out, and can
assist with the removal of water vapor as well. And once the
system is brought up to temperature, inert gas bubbles will
not contribute to fluid oxidation.
Preventing Oxidation
All organic heat transfer fluids--whether natural or
synthetic--will oxidize in contact with air. Oxidation can
begin as low as 250°F, and will double with every
20°F rise in bulk fluid temperature. Oxidation will
cause the fluid to thicken and to become acidic and
corrosive. And the fluid can become more susceptible to
thermal degradation.
If your system is not equipped with a cold-seal tank, and
the temperature of the fluid in the expansion tank runs
hotter than 200°F, we strongly suggest you consider
blanketing the tank with inert gas (nitrogen is inexpensive
and readily available). We also suggest that you purge the
system with inert gas prior to charging. This, coupled with
the inert gas blanket will not only protect the fluid
against oxidation, but will assist in keeping contamination
and water vapor out.
Note: If your system employs a deaerator/cold-seal
expansion tank, insulate the deaerator portion only, leaving
the remainder bare.
Cold Weather Deliveries
During shipment, air bubbles can be entrained in the fluid.
If the cold fluid is immediately pumped into the system, the
air bubbles can cause pump cavitation. It's best that the
fluid be as near room temperature as possible prior to
charging the system. You might store the drums in a warm
room, or employ drum warmers to bring the fluid up to room
temperature. The warmer the fluid, the more easily it will
flow into your system.
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Ask
George!
Got any questions
about the stories featured here, or on our products? Please
contact George Wilt at:
Tel: 800-222-3611
Fax: 610-941-9191
E-mail: info@paratherm.com
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