potterpat Posted October 6, 2015 Report Share Posted October 6, 2015 Hello, I have a 12 cubic foot updraft gas kiln, with 4 burners made by Contemporary Kilns about a hundred years ago...or at least 30. At any rate, I successfully fired this kiln with propane for the past 25 years that I have had it. Now being in the city, I am having to switch to natural gas. I talked to my local furnace supplier, and they contacted Ward Burners- found out that my propane orifices were size 50, and that I needed size 39 for natural gas. So they ordered them for me. I have installed them, explained to the gas company all the specifics of the burners- (80,000 BTUs / burner) and had a plumber come and put in gas line and regulators etc. So today we fired it up for the first time with natural gas... hmmm...very colorless flames that seemed bland. I used to only have the gas valve open just a bit with the propane, yet it was half open with the natural gas and still seemed not very serious... Ideas? Input? what am I doing wrong? Thank you for any ideas! Pat Link to comment Share on other sites More sharing options...
Mark C. Posted October 6, 2015 Report Share Posted October 6, 2015 Propane is higher pressure. So 1st off the whole process will feel a bit less with natural gas at 7 inches water column or 1/4 pound pound pressure. That said whatever you used to have the valve at no longer applies -its needs to be way more open Now. Propane has more BTUs (hotter faster) so you make up buy having more gas going in now. Your orfices are larger now tp allow more gas. Turn it up more.Forget about what you used to turn it to.Where are you located? Mark Link to comment Share on other sites More sharing options...
neilestrick Posted October 6, 2015 Report Share Posted October 6, 2015 Do you have a pressure gauge on the gas line? What type of burners? Link to comment Share on other sites More sharing options...
oldlady Posted October 6, 2015 Report Share Posted October 6, 2015 mark is right. to verify, contact marc ward at ward burners. the eXpert Link to comment Share on other sites More sharing options...
potterpat Posted October 6, 2015 Author Report Share Posted October 6, 2015 I am located in South Dakota. I used to live in the mountains, over a mile above sea level. Now I am not living at high altitude. I know when I lived there, I had placed a 2 inch block on the edges of my burner stand to elevate the kiln body. It seemed to help with air flow and the temp climb. Not sure if that will be necessary now that I am not at high altitude. Keep talking! I am taking notes!! Pat Link to comment Share on other sites More sharing options...
neilestrick Posted October 6, 2015 Report Share Posted October 6, 2015 What type of burners- venturi or power? Do you have a pressure gauge on the gas line? Link to comment Share on other sites More sharing options...
Mark C. Posted October 6, 2015 Report Share Posted October 6, 2015 Contemporary Kilns I think are natural draft so the air flow is a big deal-put the blocks back under as its not going to hurt and can help. My guess is 3/4 on -not full will work good now. It may take almost all on you will need a good temp guage(digital) to see if it stalls. Mark Link to comment Share on other sites More sharing options...
potterpat Posted October 7, 2015 Author Report Share Posted October 7, 2015 Sorry Neil, didn't mean to ignore you! Yes, Venturi burners, and there is a pressure regulator, which is adjustable, but no gauge on it. Thank you! Pat Link to comment Share on other sites More sharing options...
neilestrick Posted October 7, 2015 Report Share Posted October 7, 2015 If possible, put a gauge on it. It makes firing much easier, and easier to repeat the settings you use. Link to comment Share on other sites More sharing options...
JLowes Posted October 7, 2015 Report Share Posted October 7, 2015 I am going through this as well, as I am switching to natural gas from propane for my fiber raku kiln. The Venturi burner I bought is supposed to be 100,000 btu, so should do well in my kiln. This is based on 7" w.c. pressure at my home studio. The kiln is 6# fiber, 1" thickness, 20" interior diameter by 24" high. The propane weed burner never had any problem getting to, or beyond, my glaze maturing temperatures, but the new natural gas burner seems to top out at 1850 F, and then only with much fiddling of distance from inlet port, covering the exit port, etc. I am going to rebuild the kiln and am thinking that the ports for the weed burner are too large for the ng Venturi. They are both about 4"x4". I am thinking I need to make the inlet port 3"x3" & leave the exit port the same since I can damper it with a piece of kiln shelf. I have in my collection of stuff, enough 8# fiber, 2" thick that I will be able to make the walls over. Not sure there is enough for the lid too, though, but I could always double up 1" thick. Any thoughts from gas kiln folks on the 1850 F top temperature will be appreciated. I think this should be able to exceed that if I get the ports configured correctly. John Lowes Buford, Georgia http://wynhillpottery.weebly.com Link to comment Share on other sites More sharing options...
neilestrick Posted October 7, 2015 Report Share Posted October 7, 2015 What type of kiln is this- raku, updraft, downdraft? How hot do you need to fire? Link to comment Share on other sites More sharing options...
JLowes Posted October 7, 2015 Report Share Posted October 7, 2015 Raku kiln, updraft (flame under shelf, exit port in center of the top), and I have a couple of glazes that mature at Cone 05-ish. I was having a hard time holding onto he 1,850, but could stay in the 1,825-1,830 range easily. I was full open with a 1/2" ball valve, fed by a 3/4" line. The orifice in the Venturi is approximately 9/64" (it was sized by the Venturi manufacturer for natural gas.) John Link to comment Share on other sites More sharing options...
neilestrick Posted October 7, 2015 Report Share Posted October 7, 2015 Ward Burner recommends 25,000 btu/hr for 1" fiber kilns. That means you'll need 109,000 btu/hr, which your burner can't do. Add another inch of insulation and you'll need about 87,000 btu/hr. You need more insulation. Link to comment Share on other sites More sharing options...
JLowes Posted October 8, 2015 Report Share Posted October 8, 2015 Thanks Neil. I have a supply of thicker insulation and bought supplies for a new build this afternoon. John Link to comment Share on other sites More sharing options...
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