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Heater
diameter is varying precise in designing
the heaters. Units without mounting /fittings
are designed to fit holes with a diameter
tolerance of + .0254 mm - minus. 000 of
nominal heater diameter. For example a heater
of 12.7 mm i. e. ½"diameter
is designed to fit a hole size of 12.71
mm -0.000". Higher rated watt densities
on the heaters combined with larger hole
clearances will reduces the heater life.
Holes preferably
rimed to accept heaters should be rimed
all the way through are advisable. Corrosion
or scaling may make heater replacement difficult
in blind holes.
Do not allow the heated portion of heater
to operate in air or an air pocket. Do not
operate any standard cartridge heater in
open air.
Straightness or total run-out along the
axis can be held to plus or minus 0.5 mm
per 25 mm for length upto 100 mm & 1
mm per 25 mm upto 300 mm. Heaters are normally
flexible enough to fit into long holes.
Heaters installed
into moving blocks or dies should have provisions
for preventing the leads from being damaged
from motion.
Cartridge heaters with liquid tight mountings/fittings
could be used for liquid application. Heaters
mounted in a tank or vessel should be mounted
horizontally near the bottom. Heater must
be in liquid all the time. Product, process,
or system should include a device to protect
heater from operation if no liquid covering
the heater. System should be designed to
avoid air entrapments or pockets of overheated
liquid around the heater.
Heating performance can be improved by agitation
of liquid in the tank. In all cases, due
to normal high temperature attainable on
any metal-sheathed heater, avoid contact
with combustible surface or materials.
As with any electrically heated product,
the proper application of heater and temperature
control is the most important factor in
optimum performance, efficiency. No two
systems are alike It is extremely important
that attention has been given to the total
product or system design as well as operating
environment.
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