They were suddenly seeing massive product deviations from their box-anneal operation. The financial loss was substantial and growing by the day. Responding immediately, we spent two days inspecting rows of furnaces, sensors and operational details. The tubes appeared to be in good condition, but upon closer examination they exhibited signs of unusual age.
One of the metal protection tubes was removed from service and was cut off about 3 inches from the hot end. Looking into the cut piece, the tube appeared as a clogged artery lined with plaque. There was a very thick lining of inky-black carbon. This indicated that the tube had not been replaced in several years.
Upon reviewing the maintenance logs, it was discovered that there was a lapse in tube replacement going back over three years. In this scenario, thermocouple life, which should have been close to one year, was shortened to within a week. Another example of unseen forces impacting the accuracy and life of a thermocouple occurred in a large steel operation.
Out of the blue or so it seemed , our customer was experiencing rapid failures of their high-value, Type-R platinum thermocouples. The situation was promptly investigated, and it was found that the internal conductor wires were melting near the junction. This is an unmistakable sign of silica contamination causing eutectic formation, which allows platinum to melt at very low temperatures Fig. Through a collaborative, open dialogue, we identified they were in fact now treating a product containing silica.
As it turned out, the steel composition had seen a major change, which included a significant silicon content. Based on that revelation, a thermocouple was designed that was better suited to resist the infiltration of the silica, thereby protecting and extending the life of the assembly.
A final example for consideration was at an established steel-forging operation whose maintenance routine was to replace their Type-S elements every six months of operation. Through a mutual investigation, we focused on the replacement frequency of the protection-tube assembly, which contained both a primary and secondary alumina protection tube.
In this scenario, placing the brand-new element in the used protection-tube assembly Fig. Depending on how contaminated the used assembly was, the accuracy and longevity of the new element was negatively affected at an accelerated rate. The infrequency of replacement resulted in immediate contamination of the new thermocouple element Fig. One thing that I have learned Family owns 25 rental units is that these thermocouples can more often than not be recycled.
Try this next time: using a scotch brite pad, scuff the surface. Also, the blue tip of the flame assuming it is a standing pilot should be pointed at the mid section of the TC.
How old is the furnace? Reply to My name. Stormin Mormonn Contact options for registered users. Can you hold it up to the monitor? I can't quite picture that. Reply to Stormin Mormonn. Joseph Meehan Contact options for registered users. The thermocouple generates a small amount of electrical current when it has been heated by the flame.
This small amount of electric current keeps the pilot gas valve open. If the pilot light goes out, the electrical current stops and the gas valve closes. Simply put; no flame, no gas flow. Not all gas water heaters have a thermocouple. Some newer models have an advanced temperature control system. Essentially, it is a microprocessor that constantly monitors and controls burner operation and maintains consistent and accurate water temperature levels. The flashing LED indicates that the pilot is on.
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