Richard mahaffey on fri 20 sep 96
Dear Ken and clayarters,
I would check the thermocouple to see if:
a) the end of it is in the flame of the pilot or other flame source.
b) that there is no carbon build up on it. The carbon can act as an
insulator.
c) that the end that screws in to the saftey shut off valve (sometimes
called a "Baso" valve) is tight
d) if it is tightly screwed in, remove it and clean the inner surface with
an eraser cut down to fit ( we are dealing with microvolts that
makes the electromagnet stay open so gas can pass to burners, so
cleanliness and good contact is critical)
e) if the above does not work fit a new thermocouple. ( I always try to
have a spare on hand to replace if the one on the kiln burns out.
That way I get the pleasure of repalcing it under a hot kiln.)
Thermocouples work because they are made of two different metals and there
is always an electric charge across two dissimilar metals (like any metal
on your fillings, yeow!!!!!) As the metals are heated the voltage
changes, increases actually, and viola the charge of a certain level
(like 400 MV (micro volts)) acts as a signal proving a heat source and
there for a flame so it is safe (well sort of safe). this is from memory
so the details might be off, ie. number of MV, but it should be
substantially correct otherwise.
I hope this helps.
Rick Mahaffey, Art Dept.
Tacoma Community College, Tacoma, Washington, USA
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