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Heat transfer fluid systems have been in safe operation in the U.S. in excess of 80 years, and in Europe since well before the turn of
the century. The rapid spread of these systems today is testament to their safety of operation.
| Note: Heat transfer systems typically and routinely operate at
temperatures well in excess of their fluid's flash and fire points. |
Flash and Fire Points
A heat transfer fluid's flash and fire points are the temperatures at which the fluid's vapors, mixed with the right proportions of air,
will ignite in direct and intimate contact with a spark or open flame.
Fluid to be tested is placed in a cup along with a temperature probe. The cup is placed on a hot
plate and an ignition source (gas flame or electric arc) is located just above the cup. The hot plate is turned on.
As it heats up, the fluid produces vapors. When enough vapors are produced so that the cloud is ignited by the open flame (the cloud
"pops"), the technician reads the thermometer. This is the flash point.
Continuing to heat, the fluid produces more and more vapor. When the "popping" becomes a continuously burning flame, the technician again
reads the thermometer. This is the fire point.
Until the fire point is reached, should the ignition source be removed, the fluid merely sits there and oxidizes (it smokes).
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System Leakage
Unlike high-pressure hydraulic systems, thermal oil systems are not generally pressurized. The typical atmospheric closed-loop heat
transfer system employs a vent line that runs from the head space in the system's expansion tank to a catch container beneath. Even
though these systems are normally unpressurized, there are occasional leaks. The leaks that do occur are found mostly in
threaded fittings, joints, valves and pumps - the fluid will slowly weep rather than gush or spray. This "weeping" is similar to the way
bolt loosener works its way through tiny openings.
Upon contact with outside air, the hot fluid oxidizes (it will smoke). This is nearly identical to the smoke vegetable oil produces
when it is overheated on the kitchen stove. Leaking heat transfer fluids will typically smoke rather than burn, even at temperatures in
excess of their flash and fire points. The smoking will continue until all that remains on the piping is a dark stain.
| Note: Unoxidized thermal oil vapors leaking from a system can be
highly flammable. You should take immediate action. |
Insulation Fires
Should heat transfer fluid be allowed to wick through porous insulation however, oxidative decomposition will take place within
the insulation. As the fluid oxidizes, heat is produced. This is similar to the way heat is generated in a pile of oily rags or wood
chips.
Heat produced from this oxidation process adds to heat from the system that is already present in the insulation. And the insulation
prevents the extra heat from quickly escaping.
Temperatures within the insulation begin to climb higher and higher - and may ultimately exceed the fluid's
autoignition temperature, the
temperature at which the fluid spontaneously ignites.
If air enters the insulation at this point and contacts the partially oxidized and degraded fluid, spontaneous ignition can immediately
result.
Insulation
It is very important to quickly find and eliminate leaks in heat transfer systems. We suggest you locate
all potential leak points in the system, and, at these points, specify the use of high-temperature closed-cell insulation
(Pittsburgh Corning Foamglas or equal) - or no insulation at all. Most important, you should never fail to perform regular system
checks.
Like many other thermal liquids, the Paratherm heat transfer fluids have proven exceptionally safe. For years they have been used in a broad range of demanding systems where bulk fluid temperatures well
exceed the fluid's flash and fire points.
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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