dfshorn1
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Muffle theory 101
Mark,
I understand exactly your concerns. I have had this conversation countless times over the years and would like to mention a few things about how I can make such a claim, at least for porcelain muffles. I believe the same can be achieved for burnout ovens as well. I am not sure of the need versus the cost.
First, radiant energy is just that, an energy. It knows no specific level or intensity, it IS. It is just there. When measuring radiant energy, it is the measuring device's output that gets interpretted, ultimately, as temperature, at that one physical point. A muffle's heat radiation pattern which produces a temperature of 1600 F at the thermocouple and a specific point "A" when new will not vary after years of service to 1550F at point "A" while the thermocouple point still remains at 1600 F. In short, the watt loading per inch varies very little to none of the years as to be non-consequential to the radiant energy produced over the whole length of the element. That asssumes that your heating plates have not moved, cracked or the wires popped out and your insulations is still in good shape. With all physical things being equal, it is not the radiator that changes but the measuring device, the thermocouple and associated electronics that have changed. So when you see a change in the performance of your burnout oven it is most probably the slow but steady changes to the "K" type thermocouple that is the culprit. The electronics gets into more complicated stacking errors associated with tolorence changes due to ambient operating temperatures and age derating. These 2 factors combined can create some interesting calibration swings as the oven ages with no additional help from the muffle itself.
In the porcelain/ pressing furnaces, these factors have been greatly minimized as to make calibration unnecessary. I have units in service now for over 2 years and when checked, have not varied 1 degree from when manufactured. I check temperatures at various place within the muffle.
Let me know if this helps you in understanding the variables.
Daniel
Mark,
I understand exactly your concerns. I have had this conversation countless times over the years and would like to mention a few things about how I can make such a claim, at least for porcelain muffles. I believe the same can be achieved for burnout ovens as well. I am not sure of the need versus the cost.
First, radiant energy is just that, an energy. It knows no specific level or intensity, it IS. It is just there. When measuring radiant energy, it is the measuring device's output that gets interpretted, ultimately, as temperature, at that one physical point. A muffle's heat radiation pattern which produces a temperature of 1600 F at the thermocouple and a specific point "A" when new will not vary after years of service to 1550F at point "A" while the thermocouple point still remains at 1600 F. In short, the watt loading per inch varies very little to none of the years as to be non-consequential to the radiant energy produced over the whole length of the element. That asssumes that your heating plates have not moved, cracked or the wires popped out and your insulations is still in good shape. With all physical things being equal, it is not the radiator that changes but the measuring device, the thermocouple and associated electronics that have changed. So when you see a change in the performance of your burnout oven it is most probably the slow but steady changes to the "K" type thermocouple that is the culprit. The electronics gets into more complicated stacking errors associated with tolorence changes due to ambient operating temperatures and age derating. These 2 factors combined can create some interesting calibration swings as the oven ages with no additional help from the muffle itself.
In the porcelain/ pressing furnaces, these factors have been greatly minimized as to make calibration unnecessary. I have units in service now for over 2 years and when checked, have not varied 1 degree from when manufactured. I check temperatures at various place within the muffle.
Let me know if this helps you in understanding the variables.
Daniel
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