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Bushing
Heater Application Basics
Bushing Heaters (often referred to as Screw Plug heaters)
are primarily intended for liquid immersion heating
applications. Some low watt density, alloy sheath models are
also suitable for air heating applications.
Bushing Heaters are intended for installation in threaded
holes or pipe couplings (or half coupling) welded to the walls
of tanks or pipe vessels. The diameter of the heater tube bundle
is sized to fit the I.D. of the bushing pipe size.
Catalog assemblies are offered in several sheath materials
for different application medium and operating temperatures. It
is recommended that a number of smaller rated heaters be used in
larger applications instead of one larger heater, both from a
standpoint of better heat distribution and of easier replacement
of heaters. Outputs that are too high may be reduced by running
at a lower voltage or incorporating multiple circuits for
variable heater output wattage.
All immersion type heaters mounted in tanks should be
mounted horizontally near the bottom, however, above any sludge
in the bottom of the tank and away from any combustible surfaces
or material. Heater must be installed in system so that heater
sheath tube is covered by liquid at all times during operation.
A minimum of 2 inches (50.8 mm) of liquid should be maintained
above heater tubes.
Heating performance in tanks can be improved by agitation
of the liquid in the tank. Immersion heaters used in pipe
installations must allow free circulation of the liquid around
the heating elements at all times. Heaters in circulating
systems can be mounted horizontally or vertically.
Care should be taken to avoid air entrapment or pockets of
overheated liquid around the heater. Avoid mounting fittings and
couplings that result in placement of the heated section of the
heater tube(s) outside of the larger liquid area which could
result in localized overheating. Please refer to specific models
for cold lengths, contact Vulcan for extended cold section
design if required.
System should include a flow switch, low liquid level
cut-off switch, or overtemp (depending on type of system,) to
prevent heater failure or system damage.
Sheath corrosion resistance and watt density (rated heater
wattage spread out over the heater surface) is extremely
important in direct immersion heating applications. The
suggested sheath watt densities in the technology section tables
should be considered maximums unless testing in the particular
application shows that higher densities can be used.
Higher wattages over a smaller heater surface
area can be normally be achieved with increasing flow over the
heater. (higher flow rates increase heat transfer efficiency and
pull heat away from the heater). Attention must be given to the
free movement of liquid around the heater, particularly if
several heating elements are combined in one system.
As with any electrically heated product, the
proper application of Vulcan Heaters and the temperature control
is the most important factor in optimum performance, efficiency,
and longevity. 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.
Please refer to general application guidelines,
recommended watt densities, sheath temperature limitations,
corrosion guide, and other engineering data to assist you with
product selection.
Please do not hesitate to contact us for application or
product assistance. |
