JamesP Posted June 27, 2015 Report Share Posted June 27, 2015 I have a kiln I rebuild that is a 12 cubic foot updraft gas kiln. It has 4 venturi burners and an unusual exit flue that starts narrow inside the kiln an tapers out as it reaches the outside of the brick. I am having trouble reaching higher temperatures in a timely manner. I reached 1,750 F in 9 hours, and I have been going through the 1800s for the past 5 hours. I am at 1880's and 6 hours have passed. Through all of the firing I have had the kiln the exit flue dampened about 85% of the way if not more. Whenever I would open up the flue the temperature drops even earlier in the firing. I am only able to make slight changes through ajusting the gas and dapper, I am at a point where the only way for it to go up is on its own. I have no flame coming out of the flue or the bottom peep hole(only a single peep hole), but I strugle to see through the cloudy kiln atmosphere to witness the pyrometric cone. I have tried many things and that is why I am bringing my troubles to someone who may have a solution. Please help this is taking a tole on me, especially when I am unable to produce finished wares. Have any suggestions? Link to comment Share on other sites More sharing options...
neilestrick Posted June 27, 2015 Report Share Posted June 27, 2015 We need a lot more info. Updraft or downdraft, natural gas or propane, soft brick or fiber or hard brick, is there a bag wall, what's your gas pressure? Are these the original burners? Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 Natural gas updraft Soft brick lined with 1" 2300 rated fiber. I had a bag wall then removed it, gas pressure is half inch line so low. Yes original burners. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted June 27, 2015 Report Share Posted June 27, 2015 I think the primary air disc may be open too much and the secondary air may be a lot too. Can't tell from the photo. What positions are you operating your damper?Maybe you should put the bag wall back in. They are designed for a purpose. Can you find any information online about this kiln? Like what the btu's ratings and gas supply needed for the burners? How often have you fired gas kilns prior to this kiln? Marcia Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 It came with a jimmy rigged bag wall so I build a improved one, and it did not work. First firing had no bag wall and was the superior firing. How should I adjust the air discs, I played with them a little but did not notice a difference unless it was one extreme or the other. I have little experience with gas kilns, 15 firings at most with my converted kilns. Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 No online info dampers are 85% closed. No more than 100000 btu I am assuming but that is where my knowledge is limited so I am unsure Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 O and my dampers are 2inch thick fiber. As I said the exit flue tappers open and seems to create an odd method of venting, more than I would think it should if when I vent the flue half way dampened it drops temperature drastically. So currently I am fully open on the gas, air discs now half way, dampened 85-90%, peep hole closed, pyrometer 1890. Link to comment Share on other sites More sharing options...
Mark C. Posted June 27, 2015 Report Share Posted June 27, 2015 How large is the damper opening? 5x5 or larger-I do not care about taper only smallest opening size. Remember in an updraft all the heat goes stright up out the hole so you want to catch or slow that down. I'm firing my 12 cubic updraft today as well. Its taken about 4 hoyrs to get to 1850. How tight is the laod near the opening in flue-photos of your load and flue would really helpnext time. Mark Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 The flue has two exit rectangles about 3inches wide by 5 inches long, so 6 inch x 10inch. The inlet flues for the burners are 3x3, so multiply that by four. So if I recall correctly shouldn't that mean that there is less exiting than what is entering, on a quality build isn't the inlet and outlet suposed to be similar? Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 What do you mean how tight is the load? It is difficult to take pictures and measure flues at high temperatures. Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 The flame goes straight up from where the burners are positioned, the flame would than cut in towards the center at the top where the exit flue is. The load in terms of the flame traveling up and out has a clear shot till the top where larger pots interrupt a simple escape. Link to comment Share on other sites More sharing options...
Mark C. Posted June 27, 2015 Report Share Posted June 27, 2015 I meant photos before closing the door for firing not now.On my updraft I pack the top tight and put a busted 1/3 kiln shelve about 2 inches from flue/roof to slow exit flamesPutting your larger pots which are usually looser in top may not work well unless you can deck over them with a shelve.I assume you are doing reduction firing?if so put your damper in now(1800 degres) until a flame comes out flue.Where are you located? as phone call may work well now. Here is photo of my 12 cubic and how its stacked-my flue is in middle and about 6x6 with 6 small burners-the burners are not as nice as yours.Mark Link to comment Share on other sites More sharing options...
neilestrick Posted June 27, 2015 Report Share Posted June 27, 2015 Do you have a pressure gauge on it? Are you running on standard household pressure (7 inches water column), or have you had it increased? What size is the gas line from the meter? You should be able to get up to bisque temps without even trying, so I'm thinking you don't have enough gas pressure and/or volume. Link to comment Share on other sites More sharing options...
JamesP Posted June 27, 2015 Author Report Share Posted June 27, 2015 Yes standard, and no gauge just a regulator. One inch line into the house from the meter, which than turns into a 3/4 and t's into a half inch for the stove and my kiln. Then I have a rubber 1/2inch line to my kiln if that matters. Mark I sent you a message to contact me if you look at this prior to my message. Link to comment Share on other sites More sharing options...
neilestrick Posted June 27, 2015 Report Share Posted June 27, 2015 You don't have enough gas. You need to calculate the total interior volume of the kiln- 12 cubic feet is probably the stacking space, not the total interior volume. It's probably something closer to 18 cubic feet- then you need to figure out how many BTU/hr you'll need based on the materials used to build the kiln. Ward Burner has a good page for that. Then you need to look up what size gas line is needed to deliver enough gas volume to supply the total BTU/hr you need at the pressure you have. I recommend getting someone knowledgable involved, like a licensed HVAC tech. Did you get the proper permits to have this kiln at your house? If there's a problem and the house catches fire, your insurance will probably not pay for it. Make sure you're doing everything legally. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted June 28, 2015 Report Share Posted June 28, 2015 What color is the flag? Is any coming out the flu? You could damper down and also close some of the primary air (discs) . you may need more gas (BTUs ) as Neil says.. You need a tight stacking as mark says. You don't want a straight shot for the flame anywhere. You need a baffle or a maze for the flame. Maybe build a baffle for the flame to go toward the center with a wider gap between the lowest shelf and work a maze up from there. Marcia Link to comment Share on other sites More sharing options...
Mark C. Posted June 28, 2015 Report Share Posted June 28, 2015 I spoke to him about the pipe size on the phone after some other possibilities. Neil nailed it to long a run at 1/2 inch pipe size to start with.He is going to have to replumb to a larger pipe size from the meter.Mark Link to comment Share on other sites More sharing options...
Mark C. Posted July 1, 2015 Report Share Posted July 1, 2015 JPJ yesterdays unload- heres how I stack the top of my updraft.This slows down the exhaust . You can see the shelve in middle up near flue in the close up shot. The cones have been removed if you are wondering already. Mark Link to comment Share on other sites More sharing options...
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