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BecMoore

Electric-Propane kiln conversion advice

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...the worst that's happened to me in 8-ish years of firing my kiln is I had a burner blow out while candling the kiln up to temp from the wind swirling around outside. We have those Santa Ana winds here in the SoCal desert. I have sheet aluminum covers over the burners and I sit kiln shelves around the burners to help defray blowouts like this.

That said, I babysit the firings, and rarely leave the property while firing, checking up every 1/2 to 1 hour. My kilns sit 40 feet away from the house BTW.

I'm far from not recommending using a safety valve, but I've never used one on any kiln I've built. Call it lack of knowledge.

If you do intend to turn it on and let it run it's gamut, then yes, by all means install a safety valve. When I revamp my burners again, I might just do it myself. It would be nice to leave and go for a ride while the kiln does it's thing...

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It doesn't take long for enough gas to pump into a kiln to cause an explosive situation. 1/2 hour would be more than enough to blow the thing apart and do lots of damage to anything and anyone nearby. Ever turn your grill gas on and take more than a few seconds to get it lit? WHUMP as all that gas ignites at once. Now imagine pumping a much larger volume of gas into an enclosed space for 10, 20, 30 minutes and having it ignite. Pilot valves are the bare minimum needed for a gas kiln to function safely.

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Agree with Neil,
additional  thoughts on burner auto shutdowns when the flame is blown out:
When designing and operating a gas fueled kiln think about safety as well as the mechanics of the burners. 
Keep in mind that propane (C3) is significantly heavier than air (relative density 1.5), and will collect in low pockets and flow downhill.  Natural gas (NG) is lighter than air (relative density 0.65) and rises and dissipates upwards.
flammable range for NG are about 5-15% volume in air and for propane the range is 2.1-10.1% volume in air. 
LT

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I built those black pipe burners back in 1971. They were called Bendel burners named after Don Bendel retired professor from Flagstaff , AZ. They worked well with propane which was the only accessible gas at the time on a 50 acre estate. 

I agree with Neil that weed burners are a poor kilns burner by design. If using propane you really need to use a regulator for controlling the BTU output.  

As for converting electric brick kilns to gas, there is a huge differential: electric kilns use radient heat, atmospheric kiln use air flow-period. Wood kilns, oil kilns, sawdust kilns, coal fired kiln and gas kilns propane or natural gas, all require considerations for air flow from sea level to whatever. I was firing a wood kiln in Banff  (at 5000 Ft above sea level) that was exactly built to Fred Olsen specs. It continuously stalled at 1900. I got in trouble for opening the damper wide open to get it to draw.  Les Manning called Fred re: the problem. Fred said he forgot to mention in his book about adjusting for altitude. Bernard Leach does mention it in his writings somewhere. I followed his specs when building the kilns for the university in Billings at 3000 ft.. We fired with natural gas venturi burners.  I also built converted household oil burners  for pottery kilns and followed Bernard Leach's advice on how to avoid klinker buildup from inefficient oil combustion.

My point is that a brick tube designed for radiant heat does not configure easily to meet  the combustion needs of what ever fuel you are using. The best reconfiguration I have ever seen was on the cover of Pottery Making Illustrated  possibly in the early 2000s. where someone made several chambers using electric kiln carcasses for a wood burning kiln. 

Atmospheric kilns are breathing entities meaning inhale through the primary and secondary intakes on ports and the exhale  and force or pull  of the draught on the stack/chimney. You have to figure how to make them breathe for whatever fuel you are using and each fuel has different requirements. There is a lot of technical information out there. My favorite for oil burners were German tech magazines from the 60s.

Marcia

Form follows Function

 

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19 hours ago, Rex Johnson said:

...the worst that's happened to me in 8-ish years of firing my kiln is I had a burner blow out while candling the kiln up to temp from the wind swirling around outside. We have those Santa Ana winds here in the SoCal desert. I have sheet aluminum covers over the burners and I sit kiln shelves around the burners to help defray blowouts like this.

That said, I babysit the firings, and rarely leave the property while firing, checking up every 1/2 to 1 hour. My kilns sit 40 feet away from the house BTW.

I'm far from not recommending using a safety valve, but I've never used one on any kiln I've built. Call it lack of knowledge.

If you do intend to turn it on and let it run it's gamut, then yes, by all means install a safety valve. When I revamp my burners again, I might just do it myself. It would be nice to leave and go for a ride while the kiln does it's thing...

I had a flame out a few years ago in on of the two, well sheltered/secure, regulated, tiger torch kilns I run. I babysit my kilns as well but this burner might have been running for 15 minutes unlit. Suffice to say everything things came to an immediate halt while the kiln got partially unbricked and vented. Even after 30 mins of sniffing and fussing and toe tapping i was a bit nervous hitting the striker again.

I sure enjoy running gas kilns but I will never fully trust them.

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On 04/01/2018 at 5:15 PM, High Bridge Pottery said:

After thinking on this thread I decided to finally buy myself a valve and flame sense rod for my burner. After about 30 minutes ebaying trying to figure out the right search terms I ended up spending £25 ($34) on the lot so really not that much. Valve seems to have just about the right BTU throughput. Think they are both second hand.

After the burner arrived I noticed the 50mb (0.7PSI) rating and thought to myself oh crap, must be for natural gas only.... I had a look at the one on my bought venturi burner and now bought myself one of those. The thing is, this one has 25KPa (3.6PSI rating on it but also a sheet with it stating a maximum working pressure of 30PSI. What is this rating I can see as it doesn't seem to match anything. The bit that the thermocouple attaches to says 4PSI so that matches nothing. 

 

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Nobody knows the answer to this question?

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HBP

There are low pressure natural gas valves and high pressure LP gas valves .

Not sure of your across the pond pressures but over here the natural gas house pressure is what they refer to as 1/4 pound or 7 inch on a manometer.That is a water filled device (I have one) it measures the low pressure of natural gas in a home system. 

In propane or LP gas the pressures are much more -my field of expertise in with low pressures .

I do work with high pressure in my scuba diving world-my compressors  can work at 5,000 PSI with air pressures .I have them set at 3,200 max

Back to gas the thing is the shut off valve needs to handle whatever pressure the system is handling. Often e-bay stuff is not well described (user beware)

 

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Same here. All my gas work was done on natural gas, not propane. Your best bet is to contact your local propane supplier and have them help you out. Always good to refer to a professional. You'll need to figure out the total BTU needed to get the kiln to temperature (Ward Burner has  info on that on their web site), and then calculate the volume of gas needed at the pressure you're working with. The orifice on your burners will also be determined by those numbers. The general issue that most folks have is making sure that the equipment can not only handle the pressure, but also the volume of gas needed. Your basic gas grill propane regulator can't usually provide the volume. Again, talk to you propane supplier about the best methods for doing this safely.

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Have not messed with natural gas or propane for kilns; but have built 100's of houses that used one or the other for heating systems. Commercial natural gas have pressure regulators that the homeowner hooks their supply lines to. Propane tanks also have regulators that your supplier would install; that you would have to hook up to. I would strongly advise you to allow your supplier to supply and install these "commercial" regulators: not something a homeowner should be tinkering with. Commercial regulators are designed to handle high pressure and their seals are rated to handle those pressures as well. Let them assume those liabilities. I have several 100lb. Propane tanks I use for temporary heat. I purchased a commercial regulator from my supplier, that I can move from tank to tank.

remember also that the orifices in the burners are different sizes for natural gas and propane. 

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if you are using ventures burners the draft must draw the flame through. If you are using forced air...blowers, you don't need to worry as much but the size of the flue needs to be adaquate. At least the same size as the burner port. A brick extensions can help if you are at a high altitude.

Marcia

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If you take the value of 700dm3/h = 24.7ft3/h and 1ft3 of propane = 2,488 BTU then you get 61,000~ BTU/h which is about right for my burner/kiln, not sure if propane will be more or less than their air spec. The confusing thing is the 25KPa or 3.6PSI stamped on it.  

Edited by High Bridge Pottery

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On 1/4/2018 at 4:33 PM, neilestrick said:

It doesn't take long for enough gas to pump into a kiln to cause an explosive situation. 1/2 hour would be more than enough to blow the thing apart and do lots of damage to anything and anyone nearby. Ever turn your grill gas on and take more than a few seconds to get it lit? WHUMP as all that gas ignites at once. Now imagine pumping a much larger volume of gas into an enclosed space for 10, 20, 30 minutes and having it ignite. Pilot valves are the bare minimum needed for a gas kiln to function safely.

Agreed. The 'teaching story' my first professor used on us was the time she closed the kiln before lighting, forgot the striker, and went inside to get it. by the time she came back out (she'd been distracted) and lit it without thinking, the force was enough to lift the entire kiln and shift the bricks. 

whether or not it was bull, it definitely left an impression on me, but when I say babysitting, I mean I'll be sitting five feet away either reading or working, more than close enough to ear the burners change from their burning noise to their leaking-gas noise. 

On 1/4/2018 at 9:08 PM, Marcia Selsor said:

The best reconfiguration I have ever seen was on the cover of Pottery Making Illustrated  possibly in the early 2000s. where someone made several chambers using electric kiln carcasses for a wood burning kiln. 

That sounds fascinating. I wonder if I could build something like a miniaturized noborigama with old electric kilns. I certainly have the geography for one. 

Quote

You have to figure how to make them breathe for whatever fuel you are using and each fuel has different requirements. There is a lot of technical information out there. My favorite for oil burners were German tech magazines from the 60s.

I don't suppose you could point me towards where I might find some of that info? Waste oil was my first choice for fuel, but I can't for the life of me understand oil burners.

 

I do have to reiterate, whatever initial burner I end up going with, I'm definitely adding regulators on. I can't imagine any propane application that doesn't require regulators. 

(sorry for the long absence, I graduated and took a three-week long nap)

Edited by BecMoore

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I found this and part 2 is on there also. This is from 2008. Not the article I mentioned before that was earlier and used 3 chamber almost "hillclimbing. This is a conversion to gas and wood.

https://ceramicartsnetwork.org/daily/clay-tools/ceramic-kilns/converting-an-electric-kiln-for-wood-and-gas-firing-part-1/

Marcia

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3 hours ago, Rex Johnson said:

O.K., I'm sold on a safety valve for my two forced air burners. Where do I start?

The easiest thing would be to add a Baso valve and pilot light to each burner. You can get them at Ward Burner. Last I checked they weren't much cheaper anywhere else.

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I contacted Ward, of course I got the form letter. Busy guy.

Meantime I found Cooperworks while searching the interwebs for info.

Jim Cooper has been quite helpful.

I'm was considering just replacing both my home built forced air burners with a new set up that has the incorporated Baso and pilot,

Even though mine are almost identical as the pic shown minus the gauges and Baso, and pilot burner, the only real diff I can see is that  instead of a 1/4" pipe inserted crossway thru the 2" pipe that contains the gas feed/orifice, his has a straight feed welded in which is probably more efficient. The brass burner orifice and fitting  is located just upstream from the elbow on the burner.

 

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