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Joseph F

Upcoming 300th Firing - Kiln Repairs

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I have been thinking about this. I think I am going to replace my TC and fire. Just to see if it makes a difference in my overfiring or if it is the elements. Figure why not. Knowledge is powa! But I am going to order elements too. I just want to see for science.

Edited by Joseph F

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@Joseph FThe best way to check your elements is to measure the resistance with a multi-meter. A visual check can also let you know they're shot- if the coils are laying over and bunching up then they're done (probably past done).

@dhPotter I'm not sure about the bisque-cone 6 shedding thing. Probably some difference in the atmosphere or the speed of firing. The metal sheathed ones don't usually shed as bad as the unsheathed, but still do a little bit. I've added protection tubes to several Olympic kilns. It's super easy to drill the brick- I usually drill it close then file it super close, then use the tube itself to do the final little bit. Only takes about 5 minutes. Once you change the TC offset it's good to go.

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8 minutes ago, neilestrick said:

@Joseph FThe best way to check your elements is to measure the resistance with a multi-meter. A visual check can also let you know they're shot- if the coils are laying over and bunching up then they're done (probably past done).

Then I will just replace it all then. They are not all laying over, but some of them are laying over like halfway. Either way something is up. The middle of my kiln is overfiring.

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Thanks. Min for reminding about that email. This what Olympic had to say about protection tubes...

"We do not use the protection tubes on our thermocouples.  If your kiln or thermocouple is 7 years old or less it has a high temp Inconel protection tube already installed.  We discontinued using the porcelain protection tube because they tend to hold heat and give incorrect readings."

The way I read this is the TC itself has a protection of some type - "high temp Inconel protection tube already installed".

The new TC in my pic is 5 inches long. It protruded into the kiln about 1 inch. This latest TC change they sent me a 6 inch one. It sticks into the kiln about 2 inches and the back end of it is only a 1/4 inch from the electronics. Olympic said this is OK. I think this difference in length is why the TC had to be offset 20*F.

Question - Can any make TC be used in any kiln?
 

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59 minutes ago, dhPotter said:

Question - Can any make TC be used in any kiln?
 

Yes, you can use any type K you want, although there may be small differences in calibration. You also need to deal with the diameter of the TC. If the one you're using is smaller than the hole in the brick, you need to stuff some fiber into the hole to seal it up.

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1 hour ago, Sputty said:

 @glazenerd how long have yours lasted?

Breakage is a very real issue. I just worked on 4 kilns yesterday that have type S, and replaced the thermocouple on 2 of them due to breakage. They are just so stinkin' thin that it takes very little contact to break them. And that was in a very small professional studio with only 3 people using the kilns. I know I couldn't get through 2000 firings without breakage unless I pulled the thermocouples out of the kiln each time I loaded and unloaded. It's the same thing with APM elements. They last a really long time, but if you get a glob of glaze on them they're done. For most people it's not worth the risk. I definitely recommend type S to some of my customers, though, because they ned the durability and accuracy for higher temps.

Edited by neilestrick

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Did they have an outer sheath? I haven't exactly been very careful with mine as it's ok, maybe luck is on my side. I will start taking better care now I know it can last forever.

None of this makes me want to use a type K thermocouple. I am going to keep my eyes out for cheap second hand kilns with good thermocouples in.

Edited by High Bridge Pottery
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29 minutes ago, High Bridge Pottery said:

Did they have an outer sheath? I haven't exactly been very careful with mine as it's ok, maybe luck is on my side. I will start taking better care now I know it can last forever.

None of this makes me want to use a type K thermocouple. I am going to keep my eyes out for cheap second hand kilns with good thermocouples in.

Type S are two very thin wires run through a ceramic sheath that's really not much thicker than a pencil. Very easy to break it it you hit it with a shelf.

Type K are accurate and durable enough for most applications, and cheap to replace. That's why they're standard in kilns here.

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Neil:

typically they last in the 450-500 firing range (for me). Still usable, but drift enough to effect crystalline glaze. Rhodium wire is  suppose to last forever, so I assume the assertion is made from that perspective. My current S is at the 400 mark. I do agree with you that K in cone six use is fine unless you are doing specialized firing schedules.in cone 10, I think S should be considered across the board.

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16 hours ago, neilestrick said:

 @glazenerd how long have yours lasted?

Breakage is a very real issue. I just worked on 4 kilns yesterday that have type S, and replaced the thermocouple on 2 of them due to breakage. They are just so stinkin' thin that it takes very little contact to break them.

Were they sheathed? 'S' and 'R' almost always are. I've yet to even fracture the sheath of any thermocouple, let alone break one irremediably, and I've been prodding them into kilns with theatrical abandon since the late 80's.

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5 hours ago, Sputty said:

Were they sheathed? 'S' and 'R' almost always are. I've yet to even fracture the sheath of any thermocouple, let alone break one irremediably, and I've been prodding them into kilns with theatrical abandon since the late 80's.

Yes, but small, like the width of a pencil. You're obviously more adept than you give yourself credit for. I see a lot of 8ga type K's that have been bent or broken, and they're pretty tough. You've given me a mental picture of you dancing about your studio with a kiln shelf, like Fred Astaire with a hat rack.

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2 hours ago, neilestrick said:

You've given me a mental picture of you dancing about your studio with a kiln shelf, like Fred Astaire with a hat rack.

You're not far off! I absolutely love the old dance/musical films - Fred Astaire, Gene Kelly - I've dozens and dozens of them on DVD.

Now, if only I could actually dance...

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So. I love my L&L Kiln. Nothing like finishing in less than 2 hours. Changing elements and TCs was a breeeeeeze. 

@neilestrick just to confirm. I put the TCs in the tube, then loosened the screws that hold them in place. Then I pushed them all the way until they hit the end of the protection tube, then I pulled them back about 1/4''. That sound about right?

Here is a picture of the new and TC with 290 firings. Also here is a video of what was inside of my protection tube. Both of them were like this.

59eba36412436_IMG_20171021_135338(Copy).jpg.ea1ea945afcf428f778adb628fcf61d1.jpg

 

 

Edited by Joseph F
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Yep, that TC was shot! And no, don't pull it back. Just leave it tight against the end of the tube. Fire away!

Imagine if all that black metal from inside the protection tube had shed into your kiln and onto your pots and shelves....

Edited by neilestrick
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13 minutes ago, neilestrick said:

Yep, that TC was shot! And no, don't pull it back. Just leave it tight against the end of the tube. Fire away!

Imagine if all that black metal from inside the protection tube had shed into your kiln and onto your pots and shelves....

Yea. I think that was why my kiln has been overfiring recently. It has slowly gotten worse and worse. My elements were bad as well. They broke several times when I was taking them out. 

Gonna start replacing them a lot sooner I think. Maybe at 100 firings. I will also change TCs then I guess.

The black metal was like that in both tubes, so double that amount shedding on pots. Who in the heck would put up with that. No way I wouldn't have a protection tube installed if that was happening!

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Bet it was a type 'K' ;)

By coincidence, I changed the elements of a friend's kiln today. The old elements were so brittle, you could crunch them to dust in your hands like cornflakes. I've never seen anything quite like it.

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14 minutes ago, Sputty said:

Bet it was a type 'K' ;)

By coincidence, I changed the elements of a friend's kiln today. The old elements were so brittle, you could crunch them to dust in your hands like cornflakes. I've never seen anything quite like it.

It is definitely K type. I replaced it with another. I mean 16 dollars is pretty cheap for 2 TCs. 

Mine were not that brittle, thats crazy.

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You should be able to get about 150 firings, combined bisque and cone 6, from a set of elements. TC's may last longer. Just check the element resistance at 100 firings with a meter and see where you're at. No sense changing them early if you don't have to.

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@neilestrick I misread your post earlier. So I should push the TC to the end of the tube and leave it touching? I mean I can hear it physically touching the end of the tube. I thought I read one of your post somewhere else that it shouldn't be touching the end of the tube. I am confused. Just want to confirm, right now it is not touching the end.

Edited by Joseph F

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6 hours ago, High Bridge Pottery said:

At least it all make sense now when I looked at my thermocouple and it looked nothing like the crusty black type K's I have been seeing. I guess $16 for around three years of thermocouple use is not bad.

lol. I don't think it was supposed to last 3 years. But hey. It did. Although these last 20 or so firings were looking rough. I was wondering why my kiln kept having firing issues. Sometimes to cool sometimes too hot. Mostly too hot though, which kept causing mini blisters. Which is why I haven't had as much for sale as I wanted to. But this will change. Just finished cooling down from the breaking element firing. Smells so fresh and so clean in my studio. I mopped and wiped down everything. 

But yea. Even for 1 year $16x2 isn't bad at all. It was just crazy how much was in those tubes. !!! :ph34r:

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