Tuyere question....

Keg construction was halted for the winter, keg base and lid was poured though. Keg walls not. Next step, forming inner bore and tuyere.

Initially planning on using 2" DOM steel tubing to form the tuyere (wrapped w/ aluminum flashing to aid removal) on the wall pour, then use the 2" DOM outside the keg to anchor the burner (three set screw type bolts probably). Steel flange/ doubler rolled to keg OD w/ the DOM stub welded on outside. Doubler then riveted to keg.

I'm using 1" Inswool inside keg wall w/ Kastolite over it. Cut out 1" of wool around the diameter of the tureye for solid wall Kastolite.

Plan B: Would it be okay to allow the 2" DOM to extend to the furnace bore? (trimmed w/ carbide burr to radius of bore so DOM tube is not sticking out).

TIA

 

1 It is preferable to have a conical tuyere which expands as it enters the furnace. It also should be tangential to the furnace ID.
2 Wax paper or kitchen plastic film is goo to keep refractory from sticking to anything.
3 Steel tubing is OK inside a furnace. It will soon disappear.
4 Are you putting reinforcing in the Kastolite?

 

Tangential like this, yes.


Expanding conical I have not seen anywhere in construction... yet. Got pics or a link? Was just going to use constant OD tubing or pipe to form.

Wax paper would be a good option.

So, the steel tube would degrade/ melt under heat even surrounded by refractory? (Carbon steel: 2600-2800°F)

No reinforcement is planned yet for the Kastolite walls.

 

I think your plan a is better than plan b. Steel tube inside the tuyere won't improve anything and could just be an unexpected encumbrance later. When I formed my tuyere I cut about 1/4" strip out of the length of the pipe I was using and then wrapped it tight with a couple turns of thin flashing and duct tape. The tube protruded out the side of the keg so I was able to collapse it a bit with channel locks and work it out after the refractory set up. Then I just peeled the flashing out. I have a mount welded to the outside of the keg which supports the burner.
I've heard guys talking about the conical tuyere recently. I never heard of it before, but it sounds like they are getting good results. Maybe OIF could point to the discussion.
I assume you'll vibrate the kastolite walls. I'm sure it will cause some compression of the wool, no telling how much but it may throw your volume calculations off a bit. In any event you'll want to line it with plastic food wrap or something so it doesn't suck the water from your refractory.

Pete

 

Several discussions, I don't know which in particular. You commonly see guys putting flares on the end of their propane burner tubes to use them outside the furnace. It helps keep the flame at the end and not burn back into the burner tube. Here's the one I made. Since I have a brick furnace I made a brick shaped tuyere.

 

Your burner tube will last a whole lot longer if it does not penetrate all the way to the furnace chamber. I learned this by hard experience. Initially mine ended in the tuyere near the chamber but did not abut a refractory shoulder. Even when made of 304 stainless it broke down due to heat exposure. As soon as I recast my tuyere so that it necked down (after stumbling upon Mifco's amnual) just the thickness of the burner tube and the tube dead ended against that necked-down shoulder it no longer heated up to a bright cherry red and looks like I will never need to replace it. Previously it lasted 40 to 60 hours.

Mifco furnaces use conical tuyeres with burner tubes abutting refractory.

Scroll down to page 19 or so in this document and you will see details of their burner tube and tuyere design.
http://mifco.com/B & C Manual-2014.pdf

Denis

 

I built my first propane burner as a test mule. 3/4" X 8" black pipe nipple, 1" X 3/4" SS bell reducer on hot end, 2" X 3/4" BMI bell reducer w/ primary air shutter, MIG tip orifices in .025, .030 and .035". It paid off in adjustability and learning process. Low fire, I can turn it down to 10 lbs pressure w/ .025 tip and air choke, may be good for starting dry out at lower temp. 30 lbs pressure w/ .030 tip seemed to be the sweet spot. 40+ lbs pressure w/ .035 tip it ran out of primary air, but it can roar, lol. It's all quick change too. I caught flack for the 1 X 3/4 hot end bell but this was all for experimenting outside the furnace. I'll probably swage a 3/4 coupling out 1/8" plus for the flare on hot end later and initial use. Again, it's only a test mule, once I get it dialed in I may do a weld fitting burner. I'll post a burner build later.

Was planning on a 10" bore using Quik-Tube form, that would only be a 2-1/4" wall. Maybe too thin for forming the tuyere in refractory. 8" bore would be better w/ thicker refractory wall. Quik-Tube forms vary in nominal diameters, they're made to nest 4 tubes for shipping so I could just pick off the shelf. Lathe cut wood or 3D printed expanding conical tuyere form might be the answer there, as well as making a socket fit for the hot end of the burner.

Glad now I didn't try to finish the furnace walls this season. Lotta time over the winter to plan this out now.

 

Been looking for a form for the tuyere when I stumbled across this. Dimensions noted on crappy rough sketch. I'll be using a 3/4" pipe for the burner tube so 1.050" OD into the flare w/ 1.970" flare exit. Seems like a lot of flare. Most burner people say only 1/8" flare is needed (to operate burner outside the of furnace) but is there a rule of thumb (dimensions or ratios) for a flare cast in the furnace wall?

 

Not to beat the drum for Mifco, but if you look at the link I posted a couple posts above, you will see they used a very gradual flare. I did not try to scale it off their illustration yet. But it looks to be just a few degrees—-I would guess 3 or 4 per side for a total included angle of 6 or 8 degrees. When I cast mine ( in the next couple days) that is what I will do as I figure they based their choice on experience and engineering.

Denis

 

Just going to throw this out there, take it for what you payed for it.

Try your burner with a stepped flare rather than a tapered flare...might surprise you. Still tinkering with things and certainly no expert, but the stepped flare in my furnace appears to work just as well as the tapered flare I use outside the furnace. I you have the book Gas Burners for Forges, Furnaces and Kilns by Michael Porter, you may notice that he uses stepped flares in his designs as well.

Can judge for yourself too, videos are "Propane burner with plug" and "Propane burner 5"

https://www.youtube.com/user/Gippetos/videos


Just something to toss around.

Al

 

I have a Hybrid Burners propane burner, and it has a stepped flair, or in other words a short larger pipe that slips over the end of the main burner tube.
This flair is needed if the burner is operated outside the furnace.
For operation in the furnace, the flair is optional.
I have used my Hybrid Burner with and without the flair in the furnace, and it does seem a bit more stable with the flair on it.

But there are plenty of examples of propane foundry burners that operate without any flair, and they apparently work fine, so I don't think the flair is critical, but it would not hurt to have it especially if you are going to burn propane.

I have never used a flair with an oil burner.

.

 

Good point. I may print that and try to scale it to my burner dimensions.

Could you post pics of the flare form and casting?

Thanks Denis

 

I haven't tried the step flare (pipe coupling) yet, even outside a furnace. That would be easy enough to try and would be the Easy Button for casting in the furnace wall. Definitely worth a shot.

Is that a 1" pipe for the burner tube? and how do you think that compares to a 3/4" pipe? (which I'll most likely be using). I patterned my 3/4" burner build mostly from internet and YT "how to's".

Nice vids.

Thanks Al.

 

The Hybrid Burners look like a very nice piece of kit, however pricey. So I've heard some are not using a flare inside the furnace at all as the furnace bore itself acts like a flare (to complete the venturi). I built a "pipe fitting" burner as a test mule just to test the adjustability of different components. It should be good enough for dry out and initial work but likely not the final version.

I'll most likely use a stepped or gradual flare (like Mifco) cast in the furnace wall.

Thanks PatJ

 

Pics of my 'mule' burner

SS 1 X 3/4 bell reducer was for outside the furnace testing.


Primary air shutter

 

Fasted, that does look tidy, nicely done! The propane burner I'm playing with is 1 1/4" pipe.

Al

 

Hey Denis, did you get to cast and how did it end up?

Any pics?

 

That tuyere casting is still to be “in the next couple days”

I have been working several hours each day on my new low mass furnace but have not cast the tuyere yet. But I now am at the stage of that process where I have to commit to a tuyere design and cast it out of Kastolite 30. I have been using the chimney hole liner as a Kastolite casting learning step. Got that done sans cracks having moments ago pulled it out of my kiln having cooled to 300F. I have found that the hot exhaust burns away thin gauge steel at chimney. So the liner, along with ceramic blanket will keep the flame from direct sheet metal contact.


Yesterday afternoon I tigged a bunch of tig wire suspension wires onto the underside of my lid. I intend to use them along with SS wire to “stitch” the first of two layers of wool to the undeeside of the lid. I’ll glue the second wool layer to this stitched layer and coat the wool with Satanite. Will it collapse? Maybe, but hoping not. The walls of the furnace will be made similarly.

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(Please bear with me as I try to edit my post and get backs some picks and text that disappeared.)

The above post is not formatted as I would like, but it seems to defy modification, so, I will leave it with pics duplicated and in the wrong places. Sorry.

The liner pictured above sitting on a trivet will fit in the hole in the lid. the entire shell of the furnace is made from a 30 gallon barrel cut down some and reinforced at the lid opening.

Denis