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New L & L kiln


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9 hours ago, Pres said:

I might even try running the glaze load at ^4 to see how close that comes to my ^5-7 cone pack.

Just curious and apologies if it’s already been stated, the programs that have run have been the automatic cone fire?  And looking at your data and some familiarity with The Genesis control. Zone 3 in your firing ended particularly cooler than the rest so my thought is: the controller has an automatic lag function which I believe delays the other zones while the cooler one catches up. We used to have the ability to use the center element to help with the top or bottom to catch up, but I believe this  has been replaced by the automatic lag function. Anyway, maybe some food for thought if there is an obvious reason that zone is cooler (open site plug, misaligned lid) it might have the effect of extending the firing too long.

Sorry, just brainstorming a bit here. Glad to hear the protection tubes have gone by the wayside so to speak, which brings one last thought as to how deep are the actual thermocouples embedded into the kiln so they all sense equally and as accurate as practical.

Just thinking........

Edited by Bill Kielb
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2 hours ago, neilestrick said:

 

@Pres Make sure your thermocouples are all the same distance from the end of the protection tubes, about 3/8 in from the end.

I inserted (gently) a drill bit approximately the same diameter as the hole on the tubes, Using thumbnail as a stop, top 3/16" as is the bottom, and the center is 1/4". Not anywhere near 3/8".

@MinThe peep holes look to be close to 1/2 inch in diameter. I could line up a cone pack as in the old kiln, but would really be tough to see it, or at least to know what cone is down.

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2 hours ago, neilestrick said:

Why? They work great. I've never had accuracy problems with them. I have several customers who have added them to their Skutt kilns to keep the TCs from shedding all over.

Just glad he needs no offsets. I take it you do not believe the new hollow tubes are a better overall idea?

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49 minutes ago, Bill Kielb said:

Just glad he needs no offsets. I take it you do not believe the new hollow tubes are a better overall idea?

At first I was concerned they won't keep the TC's from shedding into the kiln, but so far they seem to be doing the job just fine. The downside of the open end is that TC longevity will probably be reduced. We'll see. I'm only about a dozen firings in on mine, so too early to tell.

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Please do not add thermocouple covers to your Skutt Kilns. They will cause the kiln to overfire because there is a delay in the actual thermocouple reading  the temperature. L & L offsets their controllers to make this "kinda" of work but it will act differently when the kiln is rising in temperature vs a hold in temperature.

 

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On 4/27/2021 at 5:55 PM, neilestrick said:

At first I was concerned they won't keep the TC's from shedding into the kiln, but so far they seem to be doing the job just fine. The downside of the open end is that TC longevity will probably be reduced. We'll see. I'm only about a dozen firings in on mine, so too early to tell.

That was my question when I first read about the open protection sheath.  I know how much metal I get out of that cover when i change the TCs.  I would not want that dropping out into pots.   I will be interested to know what your experience is with that @neilestrick  Is the TC back quite a bit from the end of the cover?

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25 minutes ago, Roberta12 said:

That was my question when I first read about the open protection sheath.  I know how much metal I get out of that cover when i change the TCs.  I would not want that dropping out into pots.   I will be interested to know what your experience is with that @neilestrick  Is the TC back quite a bit from the end of the cover?

I have my TC's about 3/8" from the end of the tubes, and I haven't seen any flaking into the kiln yet after about 20 firings. Definitely some flakes visible inside the tubes, though. So far so good.

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Fired a bisque to 08 hoping to drop cone 06. Could not see cone through the peep, so fired blind. When cooling at 200F. opened kiln to check cones, all witness of ^06 were darkened, but not down. Refired kiln to 06, and cones were as if it had hit 04. I figure the extra heat work confused the issue, but ware was fine.  

Today I loaded a fast fire glaze to ^5, even though I want ^6. Preheat for 4 hrs as they were just glazed and I had undried cone packs of ^5, 6, &7. Will see how this goes. I am hesitant to mess with TC or Cone corrections until I really know that is going on.

 

best,

Pres

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12 hours ago, Pres said:

Usually do a fast up, slow down, but this was on the old L & L.  

Might be worth trying the medium slow. Pretty popular schedule and for larger kilns generally can finish more even and on cone with a pre programmed final segment of 120 degrees per hour. Definitely closer to the Orton specified 108 per hour. With our glazes we could only get away with fast glaze in our little test kiln, all others just didn’t have the power to really maintain the rates so the results and evenness would vary significantly amongst our four other kilns which range from L&L to Paragon to Cone Art.

Might be worth a try, still can slow cool as you like.

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47 minutes ago, Pres said:

In my reading, I found that the factory setting is +18F. ??? Why do they do that?

 

best,

Pres

The factory thermocouple offset of 18F was used with the closed-end protection tubes because the tubes insulate the TC a bit. With the open-ended tubes they started using this year, they do not need an offset because of the tubes since they're open. An offset may be needed for typical calibration reasons, though.

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Didn't see one. I have gone through all of the material looking for a separate flier. . not.

The section where I found that number says: . . This has changed over time as we have improved the tube and the offsets pre-programmed into the  control to reflect the testing that we do in the factory. It is currently +18F. when it leaves the factory.

 

best,

Pres

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1 hour ago, Pres said:

It is currently +18F. when it leaves the factory.

I wonder if yours are at +18 and you have the open tubes, so just a construction error. You probably already checked this though........ scratch that thought, that would be opposite your symptoms

Edited by Bill Kielb
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So took a quick peek at 230F. ^5 is down, ^6 is probably at 35 degrees, and ^7 is not touched. Looks like on the medium speed that it would have been just about perfect ^6. Don't understand, but will try on the next glaze firing to match. This was a light load in some ways with just 9 patens and shelves in it. I need to get more shelves and furniture.

 

best,

Pres

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@Pres might be a good time to see what the final segment speed was in the fast and med slow firing. I am guessing it’s in the graphic, could be good knowledge and provide insight.

The expected final segment rate for fast fire I believe  is 200 degrees per hour, the expected rate for med slow is 120 degrees per hour. Often when that cannot be maintained, things start to overfire as the firing time increases.

could be good knowledge to have.

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This may be a bit geeky for the average artist, but with the Genesis controller, you can extract a data file for each of the last 10 firings that lists the setpoints, actual temperatures, and percent of power-on time every 30 seconds. Import that into a spreadsheet like Excel and calculate rates of temperature rise at various stages of the firing and for each section of the kiln. If you are facile with the spreadsheet, you can construct graphics of programmed vs. actual. Like I said, it's a geek's toy, but it can be useful to see where the variances are from expected in the programming and imbalances between the sections. This is particularly useful when elements begin to wear and the ramp rates at higher temperatures begin to significantly lag the program. You can see how the run up to bisque seems to be normal while glaze firings go on forever until the dreaded E1. I've also used this by setting a high ramp rate for a long cooling segment down from peak (set it to over 400F/hr) just to keep the controller from turning the elements on at all while logging the natural cooling rate of the kiln. I doubt you'll find a brand new kiln to be generally lagging the expected program, but it can help diagnose section imbalances that can be tweaked with a thermocouple offset.

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I have found that my kiln can go 350F/hr to about 2050F. It's not because of a lack of power, but rather because for it to go faster than that the  middle section will have to run farther ahead of the top and bottom sections than the controller will allow it to. At 2000F and a rate of 350F/hr, the bottom section will be on 100%, the top at about 97%, and the middle at about 45%, and the three sections will be dead even in temp. For the firing to increase in speed, the middle is the only section that can speed up, which would put it ahead of the other sections. The heat from the middle would help push the top and bottom faster, but the middle would also get ahead of the other sections. Personally, I don't think it's a problem for the middle to jump ahead by 30 degrees if you're then slowing down to 108F/hr for the last 200 degrees, because there would be plenty of time for the sections to even out at that point. 350F/hr is plenty fast, so it's not really a problem in terms of the results. That said, it would be nice for the middle section to take some of the work from the other sections so that the elements wear more evenly.

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51 minutes ago, neilestrick said:

350F/hr is plenty fast, so it's not really a problem in terms of the results. That said, it would be nice for the middle section to take some of the work from the other sections so that the elements wear more evenly.

350f per hour is killer speed for last segment firing rate. Not that you would ever do it, but I find most kilns are lucky to maintain 120 per hour at the very end. Nice kiln!

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1 hour ago, Bill Kielb said:

350f per hour is killer speed for last segment firing rate. Not that you would ever do it, but I find most kilns are lucky to maintain 120 per hour at the very end. Nice kiln!

It's not that fast at the final ramp. I explained that poorly, and have corrected it. It can keep up with 350F/hr to about 2050F, but then it starts to lag a little bit. It can keep up 300F/hr up to 2100F, though. That I've tested. When I fire I ramp at 300F/hr to 2030F, then I ramp at 108F/hr to 2230F. At the peak of my last firing, which was a pretty full load, it was running 93% top, 47% middle, 90% bottom. So there's definitely room for more speed but not 350F/hr. I bet it could run 150-200F/hr at the peak.

BTW, it's an L&L eQ2827-3, 14950 watts, 41.5 amps on 208V 3P service, solid state relays.

One of the cool things about the SSR's is if you get really close to the kiln you can hear the elements buzz in a pulsing rhythm as the relays cycle twice per second. It's like a faint drum beat.

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