© 2004 Heatec, Inc. Heatec, Inc. 5200 Wilson Road Chattanooga, T ennessee 37410 www.heatec.com (423) 821-5200 (800) 235-5200 Fax (423) 821-7673 Publication No. 6-04-128 Thermal fluid—when should you replace it? Are you using a hot oil (thermal fluid) heater to heat asphalt at your HMA plant or asphalt terminal? If so, do you know when it’s time to replace the thermal fluid? The fluid should be analyzed at least once a year. For HMA plants, an ideal time is at the end of the paving season, before the heating system is shut down for the winter. The analysis should be done by a specialist experienced and properly equipped to analyze chemical properties of the fluid. Fluid suppliers may do a free analysis for you. Or you may need to have an independent laboratory to do the analysis. The sample should be taken while the heat is shut off and the fluid has cooled down somewhat, but while the system is circulating the fluid. Although you cannot reliably tell if the fluid is okay by visually inspecting it, you may be able to detect problems. So, every time you inspect the strainer on the heater, be sure to watch for signs of problems with the thermal fluid. (Y ou should inspect the strainer once a month and clean it if it is dirty .) If the app earance of the fluid shows signs of a problem, you should have the fluid ana lyzed. Watch for the following signs: • Flakes of carbon • Foam or milky appearance • Presence of asphalt that may hav e leaked into the fluid • Unusual thickening of the flui d Remember, these may be early signs of a problem that could become more serious if allowed to continue. It is almost always better to correct problems at their early stages. When you replace old thermal fluid with new fluid, the new fluid will loosen carbon and other debris left in the system by the old fl uid. This debris will flow through your thermal fluid piping and rapidly begin to clog the strainer. Debris can bypass a clogged strainer and enter the circulating pump, causing unnecessary wear and damage. A very effective solution to this problem is to install a sock filter in the heater’ s thermal fluid piping. The sock filter acts as a secondary filter to the strainer . The extra protection is worthwhile. It not only protects the circulating pump, it greatly helps to keep the new fluid clean. New thermal fluid. Old thermal fluid with bad signs. Your thermal fluid supplier may offer fluid analysis as a service. Check to see if they have collection kits like this one available. Take sample while heat is shut off and fluid has cooled, but while the sys- tem is circulating fluid. Sock filter (in color) and bypass valves installed in the thermal fluid piping of a heater. HEATEC TEC-NOTE
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© 2004 Heatec, Inc.
Heatec, Inc. 5200 Wilson Road Chattanooga, Tennessee 37410 www.heatec.com (423) 821-5200 (800) 235-5200 Fax (423) 821-7673
Publication No. 6-04-128
Thermal fluid—when should you replace it?Are you using a hot oil (thermal fluid) heater
to heat asphalt at your HMA plant or asphalt
terminal? If so, do you know when it’s time to
replace the thermal fluid?
The fluid should be analyzed at least once a year.
For HMA plants, an ideal time is at the end of the
paving season, before the heating system is shut
down for the winter.
The analysis should be done
by a specialist experienced and
properly equipped to analyze
chemical properties of the fluid.
Fluid suppliers may do a free
analysis for you. Or you may
need to have an independent
laboratory to do the analysis.
The sample should be taken
while the heat is shut off and
the fluid has cooled down
somewhat, but while the system
is circulating the fluid.
Although you cannot reliably
tell if the fluid is okay by
visually inspecting it, you may
be able to detect problems.
So, every time you inspect the
strainer on the heater, be sure
to watch for signs of problems
with the thermal fluid. (You
should inspect the strainer once
a month and clean it if it isdirty.) If the appearance of the
fluid shows signs of a problem, you should have
the fluid analyzed. Watch for the following signs:
• Flakes of carbon
• Foam or milky appearance
• Presence of asphalt that may have leaked into
the fluid
• Unusual thickening of the fluid
Remember, these may be early signs of a problem
that could become more serious if allowed to
continue. It is almost always better to correct
problems at their early stages.
When you replace old thermal fluid with new fluid,
the new fluid will loosen carbon and other debris
left in the system by the old fluid. This debris will
flow through your thermal fluid piping and rapidly
begin to clog the strainer. Debris can bypass a
clogged strainer and enter the circulating pump,
causing unnecessary wear and damage.
A very effective solution to this problem is to
install a sock filter in the
heater’s thermal fluid
piping. The sock filter
acts as a secondary filter
to the strainer. The extra
protection is worthwhile.It not only protects the
circulating pump, it
greatly helps to keep the
new fluid clean.
New thermal fluid. Old thermal fluid with bad signs.
Your thermal fluid suppliermay offer fluid analysis asa service. Check to see ifthey have collection kitslike this one available.
Take sample while heatis shut off and fluid hascooled, but while the sys-
tem is circulating fluid.
Sock filter (in color) and bypassvalves installed in the thermal fluidpiping of a heater.
HEATEC TEC-NOTE
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