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Technical Data
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Paratherm NF® vs. Glycol Heat Transfer Fluids |
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Paratherm NF® non-fouling, non-toxic heat transfer fluid has for
years successfully replaced high-temperature glycol fluids in a broad range of applications. Here are some comparisons.
Temperature
Although the highest temperature glycols are rated for service to 500°F, field reports indicate that fluid degradation has frequently
occurred at 400°F and below. The NF fluid provides extended, trouble-free service in demanding applications to 600°F.
Hard Carbon Deposits
Hard carbon deposits baked onto heated surfaces result from severe fluid overheating. Overheating occurs when the fluid flows
decrease, and its molecules linger too long in contact with overheated surfaces.
Overheating can be reduced or eliminated by maintaining good fluid flow and turbulence at the heated surfaces.
With a decrease in fluid flow, glycol fluids overheat and produce a fine sooty carbon ("coke") that adheres, bakes on to, and builds up
on heated surfaces.
Under similar severe overheat conditions, the NF fluid evolves carbon granules - granules that don't adhere, that remain in suspension and
that are easy to filter out.
Disposal
Glycols are considered regulated waste in most states, and can be very costly to dispose. The
NF non-toxic fluid can be safely combined with used or contaminated lube oils and sent to the local
oil recycler (EPA, citation 57FR21524). Note: Some state and local regulations may differ from federal regulations.
Purchase Cost
High-temperature glycol heat transfer fluids can cost upwards of $15.00 per gallon in 55-gallon drums - and
much more in smaller quantities. Cost of the NF fluid? One-half to two-thirds this.
Corrosion
Glycol fluids are naturally hygroscopic. They readily mix with water and absorb water vapor from the air. Allowed to stand in thermal
systems and tooling, the fluid/water mixture almost always produces corrosion. The
NF fluid is hydrophobic. It does not absorb water, and provides the same high degree of protection to metal surfaces as
the finest lubricating oils.
Cavitation
When glycol fluids are heated, dissolved water will flash to steam. This significant volumetric expansion to vapor can cause pumps to
cavitate, and may cause hot fluid to spurt from the system (similar to the geyser that occurs when you remove the radiator cap from a hot
engine).
Water dissolved in the glycol fluid must be slowly vaporized off before the system can be brought much above 230°F.
Water is immiscible with - and more dense than - the NF fluid. It
will seek the system's low points, where it can be easily and quickly drained off.
Flash/Fire Points
High-temperature glycols have among the highest flash and fire points of any heat transfer fluid. In fact, they are even higher than
glycol's maximum rated operating temperature.
In closed-loop heat transfer systems however, the autoignition* temperature - not flash and fire point - is the most critical.
Heat transfer fluids are routinely operated above their flash and fire points, but
never above autoignition temperature. While they will burn under the right conditions, heat transfer fluids have
for years proven exceptionally safe in a broad range of high-temperature
applications. The NF fluid is so safe that it is used in demanding high-temperature die-casting service. It is widely specified by die
casting machinery OEMs as well.
Toxicity
Although glycols are not generally considered extremely hazardous, more and more regulatory attention is being paid them. Aware of the
potential hazards, system operators have begun to steer away from these fluids. Problems most commonly mentioned are disposal, cost,
fumes (odor), skin dermatitis, and miscibility with water (effluent containing water/glycol can ultimately leach into the water table).
The NF fluid is safely and easily disposed by combining with used lube oils and sending to the local oil recycler. Environmentally,
water-accommodated fractions of the NF fluid have passed Bioassay with Rainbow trout,
Daphnia pulex and Mysidopsis bahia. No organisms died, and there were no observable ill effects.
Food Service
Industries involved in the production of food, pharmaceuticals and many types of packaging prefer completely non-toxic fluids. In lower
temperature applications for example, we often suggest a mixture of food grade
propylene glycol and water. Propylene glycol is typically used to 275°F. The
NF fluid is widely specified in higher temperature applications.
Mixing of Fluids
Because of the severe problems that may result, we strongly recommend that heat transfer fluids
never be mixed. A typical example surfaced where automotive-grade ethylene glycol was mixed with a
high-temperature glycol. Finding they were out of glycol heat transfer fluid, the plant found it expedient to send the maintenance
person to the local automotive store. The antifreeze was cheap and readily available. It even performed satisfactorily
-- for a short
time.
Unfortunately for this plant, all glycols aren't the same. Even if they're called glycol.
*Autoignition is the temperature at which the fluid will
spontaneously ignite in the presence of air. See Paratherm technical data
sheet, "Significance of Flash and Fire Points in Heat Transfer
Fluids."
Questions? We'd like to hear from you. Call toll-free, 800-222-3611 -- or fax or e-mail.
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| Note:
The information and recommendations in this literature are made in good faith and are believed to be correct as of the below date. You, the user or specifier, should independently determine the suitability and fitness of Paratherm heat transfer fluids for use in your specific application. We warrant that the fluids conform to the specifications in Paratherm literature. Because our assistance is furnished without charge, and because we have no control over the fluid's end use or the conditions under which it will be used, we make no other warranties-expressed or implied, including the warranties of merchantability or fitness for a particular use or purpose (recommendations in this bulletin are not intended nor should be construed as approval to infringe on any existing patent). The user's exclusive remedy, and Paratherm's sole liability is limited to refund of the purchase price or replacement of any product proven to be otherwise than as warranted. Paratherm Corporation will not be liable for incidental or consequential damages of any kind.
Some product names of companies found in Paratherm literature are registered trademarks. This statement is in lieu of individually noting each.
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