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My first real kiln build


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The kiln in the photos is running on propane. Don't know what pressure he has it set up at. My old kiln, which had the same burner design, ran on natural gas with 15"+ WC. I think Ward has an orifice chart on his web site. The orifice holes aim in the direction of the air flow. I put a notch on the outer cap of the orifice pipe to show which direction the holes were drilled so I could line them up properly. The 3 holes had the same total area as the necessary orifice size, so you'll have to do some math there. You can always drill them larger if it's not working properly. Each burner needs its own Baso valve, since the Baso feeds the pilot light. The system in the photos also has a high temp shutoff connected to solenoids on the gas lines. The more safety systems the better. Sorry, I don't have the parts list. It was several years ago that I built it. The flame retention nozzle is from Eclipse. There are others out there on the market now, even on eBay. My burners used a 2" pipe, 8 inches long. The old Alpine kilns used 6" pipes, but you get better air/gas mixing in the longer pipe. Alpine uses a 75cfm blower for their kilns up to 24 cu/ft (stacking space), and 148 cfm for the larger kilns. Ideally you'll want to hook up the blower to an appropriate rheostat to control the speed, so the blower size isn't critical, as long as it's not too small.

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Guest JBaymore

In very round numbers, you need 10 cubic feet of air (at SATP) to combust any fuel gas (or any other fuel in fact) supplying 1000 BTUs of heat value. That is for stoichiometric (perfect) combustion. If you want to have oxidation capabilities, then you need more than that amount (or you are then dependent on secondary air entrainment...which is not a great way to go due to potential poor in-chamber mixing issues). So for a 100,000 BTU per HOUR burner....you need to actually supply to the burner's mixing tube 100,000 / 1000 = 100 X 10 = 1000 cubic feet of air per HOUR.

 

Since most blowers are rated in cubic feet per MINUTE (CFM) you have to convert that above demand in the units used 1000 / 60 = 16.6 CFM. If you want a specific oxidation capability out of the burner.... say like 10% excess air... then you have to add that to the above number .10 x 16.6 = 1.66 CFM more air.

 

Now simply mounting a 16.6 CFM blower onto a home made pipe burner assembly will NOT end up getting that 16.6 CFM mixing into the gas supply....due to the Static Pressure created by all of the burner mixing tube pipes, any elbows, restrictions of the flame retention nozzle, and so on. So the blower selected will have to have MORE capacity than what the above number represents. The Static Pressure can be reasonably calculated... but the exact configuration of the burner would have to be known. Hence the kind of larger blower numbers Neil mentions on the A.D. Alpine kilns.

 

best,

 

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

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In very round numbers, you need 10 cubic feet of air (at SATP) to combust any fuel gas (or any other fuel in fact) supplying 1000 BTUs of heat value. That is for stoichiometric (perfect) combustion. If you want to have oxidation capabilities, then you need more than that amount (or you are then dependent on secondary air entrainment...which is not a great way to go due to potential poor in-chamber mixing issues). So for a 100,000 BTU per HOUR burner....you need to actually supply to the burner's mixing tube 100,000 / 1000 = 100 X 10 = 1000 cubic feet of air per HOUR.

 

Since most blowers are rated in cubic feet per MINUTE (CFM) you have to convert that above demand in the units used 1000 / 60 = 16.6 CFM. If you want a specific oxidation capability out of the burner.... say like 10% excess air... then you have to add that to the above number .10 x 16.6 = 1.66 CFM more air.

 

Now simply mounting a 16.6 CFM blower onto a home made pipe burner assembly will NOT end up getting that 16.6 CFM mixing into the gas supply....due to the Static Pressure created by all of the burner mixing tube pipes, any elbows, restrictions of the flame retention nozzle, and so on. So the blower selected will have to have MORE capacity than what the above number represents. The Static Pressure can be reasonably calculated... but the exact configuration of the burner would have to be known. Hence the kind of larger blower numbers Neil mentions on the A.D. Alpine kilns.

 

best,

 

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

 

 

Thanks for this. I was pretty sure that the math was done for this. This info is very helpfull.

Richard

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  • 2 years later...

You can get more efficiency out of you blower if you have it in line with the burner pipe. It's a little more work, but the air doesn't have to make a 90 degree turn to get out. Instead of a cross, join the 2" burner pipe to a floor flange using 2" coupling and close nipple. Ideally, you'll want a coupling that isn't cast, as it will be harder to drill through. The burner pipe should be at least 8" long for good air/gas mixing. Attach the blower to the floor flange. It's now a straight line for the air. The orifice will be a 1/4 pipe nipple that goes through the 2" coupling. Just drill a hole through the coupling (both sides/all the way through) and insert the nipple. Put a cap on one end outside the coupling, and make the necessary gas connections on the other end, outside the coupling. The orifice holes will be 3 holes drilled in the side of the nipple, aimed away from the blower. This is essentially the burners used on Alpine kilns, which run great.

 

Here's a burner system I built for a friend using this type of burner. Sorry for the poor photo quality.

 

attachicon.gif1controls.jpeg attachicon.gif16Burner.jpg

 

What holds the 1/4 pipe nipple in the 2" coupling?  Friction fit, trapped by the cap and other fittings, welded, or sorcery?  Thanks :)

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You can get more efficiency out of you blower if you have it in line with the burner pipe. It's a little more work, but the air doesn't have to make a 90 degree turn to get out. Instead of a cross, join the 2" burner pipe to a floor flange using 2" coupling and close nipple. Ideally, you'll want a coupling that isn't cast, as it will be harder to drill through. The burner pipe should be at least 8" long for good air/gas mixing. Attach the blower to the floor flange. It's now a straight line for the air. The orifice will be a 1/4 pipe nipple that goes through the 2" coupling. Just drill a hole through the coupling (both sides/all the way through) and insert the nipple. Put a cap on one end outside the coupling, and make the necessary gas connections on the other end, outside the coupling. The orifice holes will be 3 holes drilled in the side of the nipple, aimed away from the blower. This is essentially the burners used on Alpine kilns, which run great.

 

Here's a burner system I built for a friend using this type of burner. Sorry for the poor photo quality.

 

attachicon.gif1controls.jpeg attachicon.gif16Burner.jpg

 

What holds the 1/4 pipe nipple in the 2" coupling?  Friction fit, trapped by the cap and other fittings, welded, or sorcery?  Thanks :)

 

 

The fittings on either end will hold it in place. You may need to add a couple of fender washers to the nipple to snug it all up. If you're confident the orifice holes are all correct and everything is good, you could spot weld it in place, but that shouldn't be necessary.

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