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General
Description
The Alpha Rod Heating element is a resistance type silicon
carbide heating element. The elements are rod shaped or
tubular depending on the diameter. They have a central
heating section referred to as a hot zone and two terminal
sections called cold ends. The cold ends are impregnated
with silicon metal to lower their resistance. This. Causes
them to, operate at a lower temperature. The extremities of
the elements are metailized with aluminum to provide a low
resistance contact surface to which the electrical
connections are made with braided aluminum straps.
Elements are described by giving the overall length, the
heating section length, and the diameter. As an example, 43
x 24 x 1 is an element 43" overall with a 24" hot
zone, and 1" in diameter.
Superior
Performance
1 Alpha Rod Heating element will give you superior
performance due to their high density approximately 2.4 gms/cc.
This gives the element very slow aging characteristics and
additional strength.
Interchangeability With Brand "X"
Alpha Rod Heating element are interchangeable with all
standard silicon carbide elements. They are offered in
equivalent sizes and have almost the same resistance values.
Before attempting to substitute the tubular or solid
elements for spiral type elements, please contact us.
Sizes Available
The elements can be manufactured in any length up to 127
inches. The maximum hot zone length is 96 inches at this
printing. The following diameters are standard - 3/8, 7/16y
1/2, 5/8, 3/4, 1, 1-1/4, 1-1/2, 1-3/4, and 2-1/8.
Operating Temperatures
The Alpha Rod Heating element can be operated at furnace
control temperatures up to 3100°F in an air atmosphere or
inert atmospheres of argon or helium . In reducing
atmospheres the maximum operating-temperature is 2500°F
.There is a protective coating of silicon dioxide on the
silicon carbide. The hydrogen reduces this, coating and
causes the element to deteriorate. Very dry or very wet
hydrogen are both detrimental to long element life.
Electrical Characteristics
The Alpha Rod Heating element is a linear type resistance
heater that converts electrical energy to heat energy
(Joule's Law W = 12R). W = power in watts, I = current in
amperes, R= resistance in ohms.
The heating elements are often referred to as self-bonded,
for the lattice structure or bonds that hold the elements
together are formed by re crystallizing the silicon carbide
at very high temperatures. The elements are manufactured of
green silicon carbide. which is classed as an excess
electron type semiconductor.
The resistance of a silicon carbide element is difficult to
measure at room temperature due to minor impurities,
self-heating, and contact resistance. Also the green silicon
carbide has a negative resistance temperature characteristic
from, room temperature to approximately 12000F. It turns
positive at this point and remains so throughout its normal
operating temperature range. A typical resistance
temperature characteristic curve of a silicon carbide
heating element is shown below.
for
further details contact
B
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