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Carbon Potential Variation

Carbon Potential Variation

Carbon Potential Variation

(OP)
How much variation in actual carbon might one expect from control set point when evaluating by way of carbon shim sample?
IQ atmosphere furnaces are supplied endo-gas at 35 degree dew point and enriching gas is natural gas (no peak shaving is is expected currently).  Carbon control is via oxygen probe and automatic,two-channel instruments.  Shims (.004" thickness) are soaked for 40 minutes, atmosphere cooled, and evaluated in a LECO carbon analyzer with regular referencing.  With typical C/P running between .85% and 1.05%, I was expecting +/- .05, and would like to know if this exopectation is reasonable.

RE: Carbon Potential Variation

Have you checked you NG supply?
It's been many a year but I recall on several ocassions that moisture and composition problems with NG caused our heat treating group problems.  

RE: Carbon Potential Variation

(OP)
I am not suspicious of any natural gas issues presently.  As I am comparing multiple furnaces, there does not appear to be any correlation that would indicate a general source problem.  That is, variations are divergent on different units.

RE: Carbon Potential Variation

What is the variation on your standard sample?

RE: Carbon Potential Variation

(OP)
Variations I am finding run from -.07 to +.13 from set point in one furnace.  Another falls in the narrow range of .05.  Three other furnaces are between these extremes.  As we work to improve variations, I seek to understand a reasonable expectation of range.  Targeting is adjustable through CO2 or process factor settings.

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