Cartridge Heaters
Recommendations for Improving the Life of Hi-Density Cartridge Heaters
High Operating Temperature
Tempco Hi-Density heaters are designed to operate at sheath
temperatures up to 1400°F (760°C). When process temperatures
approach the maximum heater sheath temperature, make sure
the sheath temperature doesn't exceed its limitations. Location
of the thermocouple and the type of temperature and power controls are factors that affect sheath temperature and potential overshoot conditions.
Although the heater is designed to run at temperatures up to
1400°F (760°C), heater lead wires and terminations are rated for
much lower temperatures. Care should be taken to make sure
that the heater lead end temperatures do not exceed their limitations.
Heaters can be made longer with unheated sections at the lead
end to bring the lead end out of the high temperature area.
Tempco can also provide you with a high temperature wiring harness, which can withstand temperatures up to 1400°F (760°C).
See page 15-5 in the accessories section for details.
High Wattage Rating
Heaters with very high wattage ratings can create temperature
overshoots, uneven temperature distribution and high heater
sheath temperatures, causing premature heater failure.
For liquid immersion heaters, maximum watt density depends
on the type of liquid being heated. The heavier or thicker the
liquid, the lower the maximum watt density. Higher watt density can cause the liquid to carbonize and accumulate on the heater
sheath, which will cause premature heater failure.
Scale and Sludge Buildup
In liquid immersion applications, periodic cleaning of the heater
sheath is necessary to remove any scale buildup on the sheath.
Scale can accumulate on the sheath and cause the heater to overheat and fail. When used to heat liquid in a tank, be sure to clean
any sludge from the bottom of the tank. A heater sheath covered
with sludge will overheat and fail.
Note: As explained in the above paragraphs, the single major cause for cartridge heater failure is the selection
of the wrong type of heater lead end termination for the specific application. To assist you in selecting the right
termination type, pages 2-39 through 2-57 give detailed descriptions of over 40 terminations designed to solve
many of the common application problems. If you need further assistance, consult Tempco.
Important Installation Considerations • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
1. For closest fit and best heat transfer, use reamed holes.
2. When possible, drill holes through the object being heated.
This will make heater removal easier.
3. When using an anti-seize coating like Tempco’s BNS spray
or paste, do not apply over lead wires or any other current
carrying conductors.
4. When using insulated tape or sleeving, check to make sure it
is rated for the temperature of the application. Lower
temperature rated materials can contain an adhesive or binder
that can carbonize and become electrically conductive.
5. When using heaters near their maximum recommended watt
density, it is recommended that the temperature sensing
probes be at maximum 1/2" from the heater sheath.
6. Lead wires should not be located in the hole containing the
cartridge heater during operation. This may cause the lead
wires to be exposed to temperatures above their rated
7. When used in a vacuum application, make sure the lead end
of the heater is outside the vacuum. If the lead has to be in
the vacuum, consult Tempco for specific recommendations.
8. Many applications will subject a heater’s electrical terminations to one or more of the following potentially damaging
• Moisture
• Flexing
• Oil and other
• Abrasion
• High temperature
Note: To protect the heater from damage in these harsh
environments, Tempco has a wide selection of terminations and
options available. See pages 2-39 through 2-60 for details.
BNS Anti-Seize Cartridge Heater Coating • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
This high temperature, electrically
insulating and thermally conductive
coating will minimize oxidation and
improve heat transfer from heater to
the object being heated.
Brush a thin layer of paste or spray
lightly over the cartridge heater prior
to inserting the heater into a hole.
Do not apply over lead wires
or other bare current carrying
conductors, since the water in
the paste and spray can cause
an electrical short circuit.
13 oz.
Aerosol spray can
Part Number:
T Temperature Range
1562°F (850°C)
T High Heat Transfer
(800) 323-6859 • Email:
4 oz.
Paste w/brush applicator top
Part Number: CML00020
T Temperature Range
1562°F (850°C)
T High Heat Transfer
Note: Formulated to assist
in the removal of cartridge
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