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Real-Time Kiln Advice (Kiln Curently Firing)


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#161 Kristin_Gail

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Posted 25 June 2014 - 02:07 PM

Just in case anyone is hanging on the edge of their seats:

 

I spoke with numerous potters; no one was willing/able to help me.  So I gave it a go alone again.

 

The temperature stopped rising at 2175 (an additional two tanks and new regulator gave me 200 degrees!  Woo!) - I held there for quite a bit, then shut it down.  I reached anywhere from Cone 4 to Cone 6.  Still that same flame that just goes through one shelf and out the flue.  Still only one shelf with any reduction.  I used twice the amount of soda as I had in the past (2 kg in this 19 cu ft kiln), and there's really no evidence of having added more than before.  I believe the majority of it is going up the chimney (which, at that point, is less than 1" open at the damper).

 

In any event. This system, I believe, is fried. Done.  The amount of heat radiating from the two burners - and the gauges just behind them - is absurd.  I can't fathom the inter-workings to be still functioning properly.  (The heat in the burners is almost immediate upon lighting, as that blue flame is in the throat [but not to the orifice].)

 

Currently in the Frustrated stage, scheming about building a wood kiln.



#162 JBaymore

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Posted 25 June 2014 - 02:21 PM

Kristin,

 

God I wish I was nearby.  What likely gave you the 200 degrees is the higher pressure on the downstream side of the (still) crappy (cheap) regulator.  More BTU/hr available.

 

IF that burner system is putting out about 200,000 BTU/hr when the system is fully cranked up, you should be able to FILL that chamber with the products of combustion and have the flame front burning off in the base of the chimney.

 

If you can't get that kind of situation to happen when the kiln is at about 1700 F or so (create 'backpressue' with flames licking out of every crack and crevice in the kiln)......... we are likely right back to the burner setup.

 

Still could be your adjustment.... but it is not sounding that way to me.

 

best,

 

..................john


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Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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#163 Mark C.

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Posted 25 June 2014 - 02:33 PM

speaking of basics please refresh my memory on how many cubic foot your interior is (the whole space)

Our 24 cubic salt kiln  is run on 4 MR100 burners (they do not have much reserve left when firing-like none)

Its also natural gas a tad less BTUs than your propane and the presure is 1/4 #.

 

I'm thinking you are still under powered with those regulators

The 4 tanks will help you down the road so do not get bummed out.

Hey is the snow gone yet and is the outside temp above 50 degrees in daytime?Now that the days are getting shorter?

Mark


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www.liscomhillpottery.com

#164 Kristin_Gail

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Posted 28 August 2014 - 10:03 AM

Howdy, guys.

 

I have just returned from a firing workshop at Watershed Center for the Ceramic Arts.  We fired two propane-fueled Venturi-burner downdraft kilns, one with salt.  Phew, did I never need that experience.  I have such a better understanding now, of so much.  Too much to mention.  But yes, I believe I had been focusing too much on turning up the burners instead of fiddling with the damper and waiting.  And now I understand what a reduction atmosphere looks like, when peering into the kiln.

 

Really, though, I don't think I have been doing that much wrong.  I really believe it's a burner issue.  Simply the heat coming off of them is enough tell me sum'n ain't raight.  I could grab hold of those burners at the workshop, even at the height of the firing.  I can't touch mine within seconds of ignition.

 

Here's what I would like to do:  Re-build my kiln so that it's a proper downdraft, sized to run on two B-2 burners, situated on either side of the chimney.  (As I already have one, and the high-pressure regulator, etc.)  It's 19 cu. ft. right now.  I'm guessing I'll need to make it about 2/3 of this size? (Unsure as of yet how to do the specific calculation; looking for a formula for BTU requirements with my 3" thick IFB walls.  Will figure it out though.) 

Having run through various scenarios (including turning the kiln on its side - which would make it front-loading - making the now-walls shorter, then building a sprung-arch top), I'm wondering if I couldn't just do this:

Leave it just how it is, but move the far wall (the one that now has burners) closer to the chimney, however many inches to get the cu. ft I need.  Does this make sense?  Just re-build that one wall, making the kiln more box-shaped than its current rectangle shape.  This would leave part of the roof and various metal parts of the kiln hanging out there are the end, but I think otherwise the concept will work?  I'd have a little 29"h x 27.5"w x Y"d flat-topped downdraft kiln.

Would love to hear comments on this, the latest of my hair-brained ideas.



#165 Kristin_Gail

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Posted 28 August 2014 - 10:20 AM

In case that wasn't clear - here, let me make it even less clear.  This is my idea:

 

26.jpg

 

The lid would still sit on the metal frame, there would just otherwise be empty space over there on the right. 

Important to note:  I understand I need to build a proper kiln; no more of this conversion craziness.  But it appears we are moving - far, far away - next summer.  I want to stick with this one until that time, when I do build a proper kiln (from someone else's plans!) at our new home.



#166 JBaymore

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Posted 28 August 2014 - 11:46 AM

Yes... those cheapie MR burners are not working correctly...... said so all along. 

 

However....... instead of changing things immediately..... maybe take the new understanding you have about firing process from your watershed experiences....... and try firing it one more time as is.

 

best,

 

..................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#167 Mark C.

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Posted 28 August 2014 - 12:23 PM

I would agree with John making more changes is not what I suggest.

Now that you better understand things give it a go-How about getting another B-2 burner and trying again.

Mark


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www.liscomhillpottery.com

#168 Kristin_Gail

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Posted 28 August 2014 - 12:25 PM

I can try it again with the MRs (I think that's what John is suggesting?) but I don't think two B2s are the proper size for the kiln - that's how I ended up with these MR-100s in the first place.



#169 Mark C.

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Posted 28 August 2014 - 01:14 PM

Use whatever are the most powerful burners you have

 

(I believe I had been focusing too much on turning up the burners instead of fiddling with the damper and waiting)

 

I only turn my burners up a few times and then the whole fire is with the damper adjustments after 1800 degrees -and very few of them as well.

​Having a digital pyrometer tells you that the kiln is climbing or stalled or cooling

Mark


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www.liscomhillpottery.com

#170 JBaymore

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Posted 28 August 2014 - 01:30 PM

We talked earlier in this thread (or one of the other related ones) about the fact that damper adjustments can be VERY fine changes....and make all the difference in the world.   Given you new knowledge base.... I'd also say go back and re-read everything that has been discussed in all of the threads on this kiln.... with a new set of eyes.

 

best,

 

.....................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#171 jrgpots

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Posted 28 August 2014 - 04:23 PM

Can you take a picture of your burners, showing what is directly behind the burner? I have an idea that might help

#172 jrgpots

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Posted 28 August 2014 - 04:27 PM

My idea is to change these burners to power burners. This would prevent the backburning in the throat of the burners.

Jed

#173 jrgpots

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Posted 28 August 2014 - 04:29 PM

John does this idea have merit?

Jed

#174 JBaymore

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Posted 28 August 2014 - 04:39 PM

Not with those MRs. Not worth the effort.

 

Even with a blower... no retentionm nozzle that works.  Adding air would just cause them to fluff out..... and at low settings they'd stuill backburn.

 

You could build power burners with some black iron pipe easier and even make a more effective retention nozzle.

 

best,

 

.................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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