| Custom
Thermocouples Available Upon Request
Thermowells are
not required on all heaters. Heaters are sometimes controlled with
percentage timing devices, which switch the heater on and off based on a
time cycle or by means of an optical thermometer. The temperature
sensitivity of the application dictates the need for a closed loop,
which makes use of a temperature controller and a temperature sensing
device, or an open loop, which does not make use of a temperature
sensing device and commonly operates on a percentage on/off basis.
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END
MOUNT THERMOWELL/THERMOCOUPLE
The end
mount thermowell is the most common design. The thermowell is either a
quartz tube (most common due to faster response) or ceramic tube located
parallel to the heating element. The tube is typically 5" (127mm)
long and has an inner diameter of 0.157" (4mm). A thermocouple
bracket is mounted outside the thermowell tube for the purpose of
properly positioning and holding the thermocouple in place. The
thermocouple is then located 4" into the thermowell and fastened
using the bracket. It is important to assure that the thermocouple is
not over extended into the thermowell. This may result in incorrect
temperature readings or heater failure. A thermocouple with a male plug
is displayed. |
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BACK
MOUNT THERMOWELL/THERMOCOUPLE
The
back mount design makes use of an L-shaped quartz tube that runs
perpendicular to the coil toward the back of the heater. The thermowell
then makes an arced 90° bend, continuing for a short distance parallel
to the heating element. This design is used when the heaters are
surrounded, not allowing side access, and requires the use of a .040" (1
mm) diameter thermocouple in order to make the 90° bend. A thermocouple
with a male/female plug combination is displayed. This design is not
available for the Q-Series. |
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BACK
MOUNT BAYONET STYLE
The
bayonet style thermowell is sometimes used with the metal, koramic,
glass or quartz face heaters to measure the actual face temperature
(emitting surface) as opposed to the heating element temperature. The
thermocouple goes through a bayonet fitting and is compressed using a
stainless steel spring. This approach assures that the tip of the T/C
makes good contact with the heater face. |
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PYROMETER
HOLE
It is
becoming more common for equipment manufacturers and end users to make
use of optical pyrometers (non-contact thermometers) to sense the
product temperature as opposed to the heater temperature. In virtually
all applications, the product temperature is the temperature of choice.
The heater temperature is only used as a reference in order to attain a
particular product temperature. The price reduction of these devices and
the quest for better process control has driven the use of optical
pyrometers. For that reason, it is sometimes necessary to provide an
opening (1.5" - 2" (38 - 51mm) diameter hole) through the
heater where the optical pyrometer can be placed to monitor the product
temperature. The hole size can vary based on the specific requirements.
A smaller hole is always preferred to avoid non-uniform heating of the
product. |
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WARRANTY
Solar
Products panel heaters are covered by a one year warranty against
manufacturing defects. |
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