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Old 10-09-2018, 03:04 PM
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Richard Huntrods Richard Huntrods is offline
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Heating Refractory

My furnace is off right now due to either a loose wire, controller failure, or thermocouple problem.

Symptom: it was holding idle temp no problem (1900F). When I'd get ready to blow, I'd ramp up to 2100. At 2000, the temperature display suddenly flipped from actual to UUUU (so one of the above most likely causing it). This shut off the power to the elements until things dropped to under 2000, then it would come back on and try and recover. As I was there, I watched it happen a few times then shut it off as I was near my annual maintenance window anyway.

The most obvious suspect based on what happened is a loose thermocouple wire or connection. These things can work their way loose over time.

My plan is to tighten the connections on all the wires, and then fire up the furnace. Basically if it's a high temp (over 2000F) problem, no amount of low temp fussing will find it.

The elements have been checked and are all fine, as is power to the elements.

I want to bring the furnace up to 2100 quickly.

The crucible is out of the furnace right now as part of the overall maintenance, so the furnace is just K23, fiberfrax and alumina board.

Can I fire this up to 2000 without stopping for hours at the inversion point (900-1300F)? That is, does refractory also need to be babied through the quartz inversion or can I just crank it up? Is there a 'best ramp rate" to follow with just refractory?
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