Thermocouple Question

[Knobhead]

Gadge,

The refractory linings the thermocouples are embedded in, are they multi layer brick?

On shut down cooling some of ours could shift especially with new linings until the inner had surface had really fused.

We would be running the after burner 4 days at 1300/1500°C, 1 day cooling followed by 1½ days at ambient, then ½ day warm through. The usual time for a failure would be on our “pre burn” before the furnace burden was charged in. The temperature would rise from 200°C to 900°C in ½ hour, the lining could shift again.

Just an idea.




Temperature inside the furnace? Forget it! An optical pyrometer through the port holes was the only way to get a temperature. The burden could wear 3” of the inner refractory in a week.

Won’t be the first time the refractory has fallen out on start up. Then it is panic stations!

 

[Gage]

Gadge,

The refractory linings the thermocouples are embedded in, are they multi layer brick?

On shut down cooling some of ours could shift especially with new linings until the inner had surface had really fused.

We would be running the after burner 4 days at 1300/1500°C, 1 day cooling followed by 1½ days at ambient, then ½ day warm through. The usual time for a failure would be on our “pre burn” before the furnace burden was charged in. The temperature would rise from 200°C to 900°C in ½ hour, the lining could shift again.

Just an idea.




Temperature inside the furnace? Forget it! An optical pyrometer through the port holes was the only way to get a temperature. The burden could wear 3” of the inner refractory in a week.

Won’t be the first time the refractory has fallen out on start up. Then it is panic stations!

Just pretty basic furnace bricking I'm afraid. It's layed out like this:

Furnace walls -> Layer of furnace bricks -> Space & Thermocouple tip -> Workzone & Custom made brick shapes of which I don't know the material.

 

[malcoa]

I would call in a rep from the manufacturer, i think they should really be lasting longer and they dont appear to be an an envirnment alien to them, maybe they have advice on alternatives

 

[Bobster]

I know the thermocouples we used on the cyclones had a knack to fitting them. We slid the probe out of its protective sheath and put a slight bend in it, just enough so when it was put back into the sheath it was 'held in' if that makes sense.

Doing this stopped vibration from rattling them round inside the sheath and breaking them. We also had two probes in the same locations and programmed the plc to take an average, so if one failed it wouldn't matter.

1800degC alkali dust being blown over the probes used to wear them away fairly regularly.

 

[Knobhead]

There was no point trying to taking the sheath out once it failed. I had a dolly to knock them in.

Pre heat cyclones must be one of the harshest environments possible.