Elements or Thermocouple or both?

[Brandon Franks]

So, my crystalline usage on my kiln is finally catching up to me. After about 12 (I think) cone 10 crystal firings and 15 or something glaze firings plus 20 or so bisques, my kiln is starting to slow down a bit. I have talked with many people who own Bailey kilns, and they think that my problem may not be the elements, but be the thermocouple. I have a firing going right now, but tomorrow, I will replace all three thermocouples but should I replace elements? The slowdown is no more than 10 min to a glaze firing.

 

Most of my crystal firings have very few pieces, in my attempt to keep the kiln "health" a bit better. I usually only have 3-8 pieces in each load, taking up no more then the bottom shelf.

 

I think my kiln is now over-firing, which is screwing with my crystalline results.

 

Any tips? 

 

Thanks!

[Mark C.]

10 minutes seems like no big deal yet

Since you have three thermocouples thats a zone kiln. The off temp is the part that needs to be adjusted.Seem s you need a offset adjustment and it would help to have a cone as well in a few spots.

If you contuine to fire to cone 10 consider the higher quality elements when your really need replacing.

If you are concerned the elements need to be ohm metered to see what they are compared to factory spec-lets see what Neil says as he is the last word on electrics with computers and element specs.

[Brandon Franks]

17 minutes ago, Mark C. said:

10 minutes seems like no big deal yet

Since you have three thermocouples thats a zone kiln. The off temp is the part that needs to be adjusted.Seem s you need a offset adjustment and it would help to have a cone as well in a few spots.

If you contuine to fire to cone 10 consider the higher quality elements when your really need replacing.

If you are concerned the elements need to be ohm metered to see what they are compared to factory spec-lets see what Neil says as he is the last word on electrics with computers and element specs.

Alright, I'm going to replace the thermocouples, I'll see if that helps, after like 40 firings, it seems like the smart thing to do - plus its only like $50.

I never found cones to work well with crystalline because of the temps I hold at. It seems to mess up the cones, so in some spots, especially near the bottom, they will be over-fired and completely slumped over, but at the top, they are perfect. However, both the zones (when I did a multi-level crystal firing) were equally fired (glaze wise).

Thanks,

Brandon

[liambesaw]

There's a thermocouple offset setting in your controller, you just adjust that instead of replacing the thermocouples.

[Brandon Franks]

1 minute ago, liambesaw said:

There's a thermocouple offset setting in your controller, you just adjust that instead of replacing the thermocouples.

I'm aware of the control, but I was inspecting the thermocouples yesterday and they have a lot of ware on them and are beginning to flake and crack. I also did a cone 6 firing with other day and between the different climates, they all were reading the same peak temp, but one zone overtired (bottom) and the top was under-fired. I'm only able to offset the kiln as one zone, so If it is offset to +5 degrees, wouldn't that just make the bottom even further over-fired?

 

Thanks for the help,

Brandon

[Bill Kielb]

33 minutes ago, Brandon Franks said:

Alright, I'm going to replace the thermocouples, I'll see if that helps, after like 40 firings, it seems like the smart thing to do - plus its only like $50.

I never found cones to work well with crystalline because of the temps I hold at. It seems to mess up the cones, so in some spots, especially near the bottom, they will be over-fired and completely slumped over, but at the top, they are perfect. However, both the zones (when I did a multi-level crystal firing) were equally fired (glaze wise).

Thanks,

Brandon

Thermocouples generally either are good or they are not. Generally corroded through actually. Elements can be measured and ten minutes is fairly minute actually. Cone ten firing is super tough on elements, 10% increase in resistance usually dooms most elements to replacement at cone six  since most kilns are marginally powered. 

At cone six, elements last 150 firings. At cone ten, maybe 20 to 50 firings. Generally firings begin to take an additional hour  or so  at cone six when they are worn. You are correct this extra time then begins to cause everything to overfire.

Here is to hoping  your thermocouples are the cause but it really sounds like your elements are wearing, possibly too much for your intended use. It would be a good idea to measure their value now and record for reference. If they are the root cause of the trouble but you still want to get more use, offsets and relay turn on time can be adjusted to get some more use out of them.

I would also encourage checking any points for excess voltage drop. Relay contacts, less than .1 volt, not to exceed .3v and any connections thermal scanned not more than 10 degrees above ambient of similar or adjacent connections.  Any of these heat the outside of your kiln and not the inside wasting energy each firing.

Bad thermocouple below. Still works fine but only Maybe 10 decent firings left in it.

[Bill Kielb]

43 minutes ago, Brandon Franks said:

I'm aware of the control, but I was inspecting the thermocouples yesterday and they have a lot of ware on them and are beginning to flake and crack. I also did a cone 6 firing with other day and between the different climates, they all were reading the same peak temp, but one zone overtired (bottom) and the top was under-fired. I'm only able to offset the kiln as one zone, so If it is offset to +5 degrees, wouldn't that just make the bottom even further over-fired?

 

Thanks for the help,

Brandon

Usually each zone can be offset. Look in you instructions for thermocouple offsets Tc1, Tc2, Tc3 In a kiln with a bottom element as the firings grow longer over firing can occur bottom and top which sounds crazy but the center element will often cycle with the top to try and make up for the heat loss. It’s often hard to even this out with offsets especially as the elements wear. Relay cycle time is often the only thing that might help this track better as a temporary fix.

[neilestrick]

There are two possible offsets in the controller- Thermocouple Offset and Cone Offset:

Thermocouple offset will allow you change the setting on each thermocouple individually. If you have problems with unevenness between sections, or the kiln is running hot/cold across all cones, then use the thermocouple offset.

Cone Offset is used to calibrate the temperature of a specific cone. If, for instance, cone 5 is firing a little hot but cone 04 isn't, then you want to do a cone offset for cone 5.

[Brandon Franks]

11 minutes ago, neilestrick said:

There are two possible offsets in the controller- Thermocouple Offset and Cone Offset:

Thermocouple offset will allow you change the setting on each thermocouple individually. If you have problems with unevenness between sections, or the kiln is running hot/cold across all cones, then use the thermocouple offset.

Cone Offset is used to calibrate the temperature of a specific cone. If, for instance, cone 5 is firing a little hot but cone 04 isn't, then you want to do a cone offset for cone 5.

Thanks, I see this now. 

 

This helps a lot, thanks!

 

Brandon

 

 

[Mark C.]

You could also put a protection tube over the new pyrometers and they will last much longer-especially at cone 10 which without tube eats them like candy 

[Brandon Franks]

12 minutes ago, Mark C. said:

You could also put a protection tube over the new pyrometers and they will last much longer-especially at cone 10 which without tube eats them like candy 

Like the one L&L uses?

[neilestrick]

28 minutes ago, Brandon Franks said:

Like the one L&L uses?

Yep.

[Brandon Franks]

1 hour ago, neilestrick said:

Yep.

Do you know where I can get them? The thermocouples for Bailey kilns are eight inches.

[neilestrick]

8 hours ago, Brandon Franks said:

Do you know where I can get them? The thermocouples for Bailey kilns are eight inches.

From L&L or a distributor near you. L&L is in NJ, so you may be close to them. Or there are many places online that sell them if you just search 'thermocouple protection tube'.

[Dick White]

The above information about the hardware from @Bill Kielb and @neilestrick is good. A comment about your crystalline firings - it is good to keep the loads light unless you have a super powerful kiln like the L&L JH series (named for the late Jesse Hull, a crystallier who helped them design it specifically for crystalline work). A light load allows ordinary kilns to maintain the specific fast ramps needed for crystalline work. You mentioned you load the few pieces all on the bottom shelf. That puts all the thermal load in the bottom zone and nothing but hot air for the upper zones. Over time, that will result in uneven wear on the elements, leading to uneven firings. Add a few small shelves and spread the work within the kiln.

[Brandon Franks]

3 hours ago, Dick White said:

The above information about the hardware from @Bill Kielb and @neilestrick is good. A comment about your crystalline firings - it is good to keep the loads light unless you have a super powerful kiln like the L&L JH series (named for the late Jesse Hull, a crystallier who helped them design it specifically for crystalline work). A light load allows ordinary kilns to maintain the specific fast ramps needed for crystalline work. You mentioned you load the few pieces all on the bottom shelf. That puts all the thermal load in the bottom zone and nothing but hot air for the upper zones. Over time, that will result in uneven wear on the elements, leading to uneven firings. Add a few small shelves and spread the work within the kiln.

Just removed the elements, I got a free pair with the kiln and forgot about it.

You are totally right, the top elements, don't get me wrong, are worn, but the bottom were breaking and cracking all over the place as I removed them.

 

I will absolutely use your tips for loading my next Crystal load, thanks for that!

 

Brandon

[Mark C.]

7 hours ago, neilestrick said:

From L&L or a distributor near you. L&L is in NJ, so you may be close to them. Or there are many places online that sell them if you just search 'thermocouple protection tube'.

Tubes come in all lengths and you can cut them with a wet diamond saw as I do but most folks do not have one so get the right length. A protection tube is really needed at cone 10 as the metal just flakes off at a rapid pace. With  a tube its still hot but will last much longer. Of course S thermocouples are far superior but very spendy and the reading unit needs to be able to read the output for S thermocouples (not all do)