One Burner 10 Cubic Ft Gas Kiln?

[tomhumf]

Last year I converted my old electric kiln to gas . It's worked out pretty well and I now love gas firing. 

Due to needing a bit more kiln space (my current one is around 3 cubic ft) I've decided to try and build a new 10 cubic ft kiln from scratch. 

One major decision before starting to design the construction is whether I need to buy another burner.  The burner I have is rated for use up to 10 cubic ft sizes. 

I see other gas kiln of this size mostly use two burners . I'm not sure if that's because they are lower powered weed burner types.

I think someone said once  that the temperatures will be more even throughout the kiln with a two burner system.

Perhaps there is a way to make one burner spread nicely? I'm thinking I could split the flame path on the way in and deflect it on the way up...see sketch

Anyone using/used a one burner kiln that's this sort of size? 

 

 

[neilestrick]

You need to know the specific BTU rating of the burner. Saying it will handle up to 10 cubic feet can mean a lot of things. Does that mean 10 cubic feet of total interior volume, or 10 cubic feet of stacking space? 10 cubic feet built with soft brick, fiber, or hard brick? 10 cubic feet with walls of what thickness?

I have built single burner kilns, and I've always done them as a cross draft:

 

 

[Mark C.]

Generally speaking more burners mean more even firing.

That said if its a power /fan burner one may be enough. Power burners are powerful.

I tend to favor two to even the heat for 10 cubic feet.But I'm a natural draft guy

[tomhumf]

Thanks both. The manufacturers don't have much info, I've emailed them to ask for the BTU of the burner. It's the one pictured. I guess I'll wait until I hear back from them before proceeding. 

My other quandary is that I've been given three 23" circular kiln shelves. It seems to make sense to build the kiln around those...and maybe buy another one or two. But would a square kiln with round shelves make sense?

[liambesaw]

Doesn't make sense to me, round shelves won't fit inside as well, less room to jam stuff in, more empty space.  Plus kiln shelves aren't so expensive, might as well build the kiln around standard sized

[neilestrick]

Kilns need room to breathe, so round shelves wouldn't be a deal breaker, but you will be wasting space. I would cut the shelves down to a rectangular shape with rounded ends, so that if you ever replace them you could use standard 12x24 rectangular shelves.

[Luitreth]

I'm in the UK and also going to build a  square kiln but with two burners, have you seen the "power kiln" design in Andrew Holdens book the Self Reliant Potter? This is what I'm intending to build, posted a picture on my earlier thread, may be the kind of design you are looking for.

[Mark C.]

just get some rectangular shelves

[tomhumf]

On 4/30/2019 at 9:01 AM, Luitreth said:

I'm in the UK and also going to build a  square kiln but with two burners, have you seen the "power kiln" design in Andrew Holdens book the Self Reliant Potter? This is what I'm intending to build, posted a picture on my earlier thread, may be the kind of design you are looking for.

I have got that book yes, it's a good read. I don't think that design will really be the best way for the materials I have available. 

Regarding the burner, I got this reply from supplier: 

BTU ratings as follows:-

3 psi 82,750

10 psi 151,100

30 psi 261,700

My regulator goes up to 2 bar so I guess in theory I could get 261,700? I never currently turn it up that high though. 

I'm thinking I may do a similar design to the diagram you posted Neil. It would be downdraft with 12" X 24" shelves and a sprung arch roof. 

[neilestrick]

Here is a link to the data guide at Ward Burner so you can calculate the size of kiln you can build with that burner and whatever type of bricks you plan to use. To be safe, I would use the high end on the charts, and not the high end of your burner.

[tomhumf]

Thanks Neil, it seems it would work if I understand those charts correctly. I assume when it refers to 9" walls it means  9" long bricks layed with a 3" wall thickness...

Thinking of what bricks to use - I can get soft bricks and 42% alumina hard bricks. I was thinking to use hard bricks as the kiln floor, layed with 4.5" thickness, and as the first layer of bag wall / firebox.  And then soft bricks everywhere else. 

I wonder if one layer of hard bricks at the base will give enough insulation, it would be light concrete blocks underneath that. 

 

 

[Mark C.]

The 9 inch refers to the total thickness of 9 inches of wall not 3 inches of wall. Most cone 10 kins have 9 inch walls-which is two layers of 4.5 wide bricks.

One layer of floor is not enough. Especially hard brick-you will need at least two  layer and then something else like expanded metal. Most kiln books show 3 layers of bricks in floor. One layer and you will overheat the concrete floor bricks

I have fired a few kilns to cone 10 with only 4.5 walls of soft brick then a thin  layer of fiber outside.The walls are always running on the hot side. I suggest not making it this way.

hard brick one layer (bricks turned sideways-4.5 inches) will be to hot on the outside. If you do not have enough bricks to make a 9 inch wall use fiber on the outside say 2-4 inches You could them wrap in metal or expanded wire

Kiln conversions like electrics with those thin walls do not last long as the outer walls get to hot and the metal jackets fail over time.They are simple short term kilns that will not hold up for decades under weekly use.

[neilestrick]

Like Mark said, 9" thick walls are standard for gas kilns. Bricks are 2.5 x 4.5 x 9 or 3 x 4.5 x 9. If you can get 3" brick, use them, because it speeds up construction vs using 2.5" brick. Walls are two 4.5" layers, with staggered joints. Run a soldier course every 5 layers to tie them together. No need to use mortar with soft brick, you'll put steel on the outside to hold it all together.

I would make the floor from soft brick as well, and go 3 layers thick. With 3" brick that will be the same thickness as the walls. With 2.5" brick it'll be a little thinner but will work. Lack of floor insulation is often the cause of slow firings. Don't skimp. You can use hard brick for all 3 layers where you need to put supports for the shelves, but make the rest of the floor with soft brick.

[tomhumf]

Wow ok, that's a lot more bricks than I thought then. My supplier does the 3 x 4.5 x 9 ones so those are what I'll use.  

For the roof I suppose it would be easiest to do a one layer arch with them stood up @  9" thick...or would you do a 2 layer of 4.5" arch? 

I'm a bit worried how difficult it will be to cut the arch bricks to get a good seal. 

[Mark C.]

You have a few choices-for a small roof you can clamp them with rods as a flat unit under pressure .I would do the 9 inch thick with that.Use agnle iron on the 4 corners. and two threaded rods on each leg. This is for small roofs as you lift it into place.

The arch is a better choice.

My arch is 4.5 inchs thick made from k 28s and some k26 soft bricks-K23 do not hold up well over time at cone 11.

Over that arch is 2 inchs of 8# fiber and its cob=vered with corrugated sheet metal over that to keep the dust off-its all under a huge metal roof so its dry always.

This kiln has had two roofs in 40 years and this one has many hundreds of fires on it.The 1st one was made from k23 which faoled over time.

You can cut soft bricks on a radial arm saw witha 14 inch carbide blade. Set a jig up and a dust vacuum.Make sure the brick fits into the jig  well and tight and use a piece of wood to hold brick  in the jig as the saw is pretty nasty.You dial in the angle on the saw arm and cut all the bricks twice to get the angle you need.

This technique is little known but It works very well. I have a deadacated old radial arm set up for just this as those saws  are pretty worthless now that miter saws have displaced them.

The bricks cut like butter-use a dust mask and safety glasses.

I make the standard arch size and 1,2, or 3s not a special size so the bricks can be used again with other standar arch sizes.

[neilestrick]

You can buy arch bricks and skew bricks pre-cut. They are cut along the length, so when you lay them in, the arch is 4.5" thick. Then you add another layer to get the full 9". If you lay it out right, you can do it without having to cut a key brick, but even if you do have to cut one, they cut really easy. Your brick supplier can probably help you figure out the number of straight brick and arch brick (#1 or #2) needed for an arch of a given span and rise, and which skew brick to use so you don't have to cut your own.

[Mark C.]

My 1st arch was two layers soft brick. It was over kill.

In Fred Olsens book it shows you how to lay out arches if I recall.Pretty easy stuff.

 

[neilestrick]

You can go with one layer of arch and then fiber, but if you don't want to mess with fiber you'll need two layers of arch brick.

[tomhumf]

On 5/3/2019 at 12:59 AM, Mark C. said:

The arch is a better choice.

Would this be because the arch is stronger and will be more durable over time? 

I've ordered the Olsen book so will have a read of that.

My brick supplier says they can cut bricks to my spec, the only ready cut arch bricks I could find elsewhere are super expensive. Otherwise I'm thinking if I calculate the angles I could set up a jig and hand cut them...

13 hours ago, neilestrick said:

You can go with one layer of arch and then fiber, but if you don't want to mess with fiber you'll need two layers of arch brick.

I don't really want to use fiber, but 2 arch layers seems super hard to calculate. Would one layer layed in 9" thickness be a silly idea? I see them done in houses this way round. 

[neilestrick]

An arch is the strongest method of building a kiln roof.

You can cut the arch bricks to be 9" with one layer. The joints don't stagger as much, though. I don't know if that's an issue or not. The benefit of having two layers is that if there's a gap in a joint, the second layer will cover it.

[tomhumf]

I've had to put this on hold due to money but, now have the funds ready...

This is my latest plan after your suggestions and some other reading. 9" thick walls, will probably do 4.5 " arch with fiber over the top and 9" thick floor.

I'm hoping to make it work with one burner, my biggest concern from this plan is the space around shelves. It's probably a bit tight top and bottom ( 1½" ) and too much at the flue side (4½") but can't see a better way without having to cut a load of bricks.

I plan 8 courses for walls, which would give about 10cu ft total internal space with arch. 

 

 

 

[neilestrick]

I'd give another inch of width in the firebox, then just center the shelves in the space. What diameter is your burner port?

[tomhumf]

Ok thanks. My plans for burner port is currently 3" X 4" opening. I plan the chimney at 6" X 6" inside with 3" thick walls.

[Michael murphy]

 I don’t know how far along you are in this process of building a kiln . I have a 10 ft.³ alpine kiln With two forced air blowers. Is set up for Cone ten firing with reduction. The skill also has a hood system for it. It requires 7 pounds water column pressure of gas to run it. I also have a branch slab roller extruder bats shelving furniture. I want to let it all go for very reasonable. Give me a call if you’re interested  Michael murphy 661-599-5180 

[tomhumf]

Thanks, I'm still early stages, I'm in the UK though and I guess you're US.