Gas Burner Question

[Wyndham]

The gas kiln I have now is homemade down draft with 6 raku style burners, 3 on a side of a kiln that is about 45 cu ft stacking area. This works fine but I'm looking at making a smaller size kiln that is similar in design as a Geil, where the burners come in from the floor and has no bag wall.

I have looked at a burner from from summit kiln conversions that has 4 pipe style burners(50k btu/burner) that attach to a manifold but do not have primary air ports(PAPS) or butterfly air intake adjustments. This system relies on the damper to create a reduction atmosphere. I believe the gas orifice is drilled into the manifold and the primary air  is drawn in around the manifold into the pipe burner.

Since I have  used a different system with PAPS and damper, I'm wondering how responsive this type of burner is in giving overall reduction.

Most folks that have this system have converted an electric to gas but I was thinking of building a small downdraft with this burner setup. My main concern is controlling reduction as I start at about 1550 and adjust on the way up to cone 10.

Hope to hear from some folks that have used this type of burner setup.

Thanks Wyndham

[neilestrick]

Personally, I would never use a burner that has no air adjustment. I like to have as many options as possible for getting a kiln to fire properly, which means being able to adjust the gas, damper and air. They all work together to achieve the correct rate of climb, degree of reduction, and pressure in the kiln. Take out one of them and you're asking for headaches.

[Guest JBaymore]

I am reminded of the Eharmony TV commercial in which the owner guy says to the girl...... "Beth, Do you want fast or forever".

 

So re-worked a bit (a lot) here......... "Do you want good, or cheap?"

 

All of the cheapie burners "work" at a certain level. They combust gas to some degree.  They create a flame.  Will that flame cause a temperature increase in an insulated chamber?  Yes. 

 

The better a burner, the more efficiently it will combust that gas, and the more uniform mixing it gives to supply the MIXTURE into the chamber. Fuel firing results are not just a product of heat energy... they are also the product of the even-ness of the atmosphere.  That relates to something called mixing.  There is also a property of burners called "load penetration". 

 

Cheapie burners do not offer good mixing properties, not do they offer good load penetration properties.  You have to "work around them".  Firing profiles and loading layouts get created to do this.

 

Industry uses burners that have both excellent mixing proper ties and high load penetration properties.

 

A good burner will "buy" you cheaper firing costs, more control over the kiln, and a higher percentage of firsts (assuming no operator error).

 

For that kind of design, go with commercial burners unless you have the time to study burner design, and have a well equipped shop to produce a quality product.

 

I'm also reminded of the saying "pay me now or pay me later".

 

best,

 

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

[Marcia Selsor]

I fired an old Olsen kiln when I was teaching at UT Brownsville. It had 14 burners on 2 separate manifolds. The gas pressure was adjustable. These burners were venturi type and came up into the floor of the kiln. The only way to adjust the air flow these burners was with the damper and the gas pressure because the primary air discs were completely rusted. 

 

So if could be done. I just followed the kiln log from the previous instructor. Piece of cake. You would not have that luxury.

 

Marcia

[neilestrick]

I fired an old Olsen kiln when I was teaching at UT Brownsville. It had 14 burners on 2 separate manifolds. The gas pressure was adjustable. These burners were venturi type and came up into the floor of the kiln. The only way to adjust the air flow these burners was with the damper and the gas pressure because the primary air discs were completely rusted. 

 

So if could be done. I just followed the kiln log from the previous instructor. Piece of cake. You would not have that luxury.

 

Marcia

 

I think most folks who fire with venturi burners do not adjust the air intake on the burners during firings once they have figured out the best air setting for the burners. But without having that option at the start it wouldn't be easy.

 

It's much easier to adjust the burners than redesign the kiln.

[Wyndham]

As with the burners I have on the 45 cu ft ,I have the paps open til reduction then closed but for 1 turn then around cone 6 open another 1/2 turn while adjusting the damper as needed.

The issue with burners under the kiln is the paps adjustment, too many issues with stiff joints, old age and the like so I might have to stay with burners either 2 in back or some on the sides so as to adjust the  paps and a bag wall.

My gut feeling was there might be a possible problem with this type of burner, just wanted to see if I missed something.

Wyndham

[Mark C.]

I shot a few burner photos for you today-I'll post on Saturday as today was glaze day my 3rd friday in a row -glazed two kilns and loaded them-I'm beat tonight . I'll load the photos in am and talk story then.

Mrark

[Wyndham]

Thanks, looking forward to it.

Wyndham

[Mark C.]

My two friends with Geils kilns never adjust them air flab wise. They do have a air adjustment but once set its done.

The same is true with my 8 venturi ones on my car kiln and my 4 on salt kiln-once they are set right I never have changed the air setting-these are all commercial burns.

I do not use home made burners anymore. I have a pile of them stored away.

I love Ransome burners but only have one for raku.

My small commercial 12 cubic updraft (Berman brand from Hollywood,Ca which is long gone) which I bought used long ago has the square gas manifold  system and pilot ring

These are cast burners  made from refractory material like stilts or posts sitting in metal rings with replaceable offices-no air adjustment. That said it not been an issue these reduction wise

the kiln fires as good as an updraft can ( I am not an updraft fan). All reduction is with damper which is still true with my other kilns as well (as I never adjust them)

The pots on the bottom of this updraft are reduced well as is most of the load. The top is the exception but thats because its an updraft. I block up the exit flue with a broken shelve near the top and this slows down the gas and tends to even it out so top is hotter (updraft usually has a cool top) It fires about 1 cone apart.

Now as far as the cast burners . As far as I can tell these are made by a commercial burner company-I have seen them on other kilns.

These burners are not particularly powerful but since they are 6 of them they easily do the job.

since the air is what comes in under the steel ring and has no adjustment. I do think they where engineered as to how much space under etc. 

They are very much better than any pipe burner but they are not a say Ransome burner.

I saw a kiln last year with 24 of them-about a 60 -80 cubic double sided  door kiln

My 12 cubic fires for under $20 so they seem efficient .

One thing about the design of shooting straight up hence the no bag wall-this design can have some drawbacks.

These are- not enough room between walls and shelves-to close to corners-to close to load. These all make for hot spots on wares or refractories (spalling bricks)

Make sure you use k 28s around any of these burner penetrations -K 23's fail right away.. I also suggest coating the hot spots with a coating either ITC or the zircon mixture i have posted with milled zircon and colloidal silica. Both work well for this.

Mark

 

All this talk is using soft bricks on floor (except for stilt spots)

 

 

[Wyndham]

Thanks for the pixs, lots to consider. The k28 vs k23 is something I had not accounted for.I have the pad for the kiln, just need a shed(metal one) and this spring try out a a new kiln build.

 

Wyndham

[Marcia Selsor]

Neil,

I beg  to differ with you on adjusting Venturis during firing. I had monsters on a car kiln I designed and 2 more on a 30+ cu. ft Sprung Arch kiln. This was on natural gas. They were purchased for me without my input by the facilities services at the University where I taught for 25 years. I fired these burners for 20 years and I had to adjust the primary intake several times during the firings in coordination with the dampers. 

I agree you can't really adjust burners that are under a hot kiln. The largest pair of venturi s was

about 18" before turning a 90 degree angle vertically for another 2 feet up. They would backfire on occasion. Not the greatest set up . Way over powered.

The smaller pair was 2 feet. Both kilns fired well once I got it down. When the firing started for the semester , I fired each kiln 2 xs per week til we got everything fired. I had 60 students/ semester.

Marcia

[Mark C.]

The reason I say better soft bricks is over my life I have had to redo so many k23 issues. For myself and friends. I now use k 26 and k 28 in all hot spots starting with 28s and working away from the burner ports(hard brick) I switch to 28's to k26's.

K23s do not hold up well in hot spots over time. As I fire to soft cone 11 this is very true but my friends who fire to cone 10 also have k23 issues in hot spots. So if you start with a better brick then repair is not down the road .The drawback is they do not insulate as well but for example if you have to tear them out whats cheaper? the gas cost or the brick repair ?If you drill your port holes thru soft brick a k 28 is what you start with.

I replaced my arch with k 26s and 28's long ago as the 23s all fell apart. Now if you only fire now and then this all may be mute  point somewhat but I'm taking about professional use which applies to you or school use as well.

My little 12 cubic is all k23s and the inside is spall city-really a poor choice of brick.

My kilns get used almost weekly so brick choice is key and after so many rebuilds one learns to do it right. I used stockpile cases k23s now its 26's and 28's.

I only use 23's in cool spots far away from flames or ports or bag walls. I coated 1 inch fiber over most 23's on walls long ago and I coated all 23's from day one.

All burner port areas are hard brick then 28s then 26s and finally some 23's away fro all that heat.

All this talk is about cone 10 kilns not cone 6 for those who fire to 6 and none is about electrics.

One last note on burners is those sweet ransomes that have 90s on  the end of them you can have them point up and adjust them from outside the floor area as they are long-just a thought if money is no issue

Mark

[Marcia Selsor]

If you mean the ones I had, there was limited space and money was always an issue at the University.I fred them to ^6 reduction.

Unfortunately some hot shot engineers were responsible for much of the design layout and ventilation system of the Univ. kiln room. Supposedly the louvers were to open when the gas was turned on. This never was hooked up after installed. Ultra violet sensors by Honeywell. Any accidental nudge would misalign them but that was easy to adjust.

 

Marcia

[Guest JBaymore]

 

Unfortunately some hot shot engineers were responsible for much of the design layout and ventilation system of the Univ. kiln room.

 

I've done more work to "fix" kiln installations for clients and also for the institutions I've worked for that were "designed" by "hotshot engineers" than you can imagine.

 

On one move to a new space/building.... if they'd gone ahead with the original engineers plans.... it would have been the "conceptual ceramics" department.   No firing would have worked after the FIRST firing.

 

I LOVE telling an engineer that his calculations are wrong on the effluent temperature that the fan at the top of the stack is going to see.... and it exceeds the specified use temperature of the fan unit that HE selected.  And then showing him the air volume dilution calcs on paper... and then having him reluctantly change it.  He was likely getting 10X the hourly rate that I was.

 

Arrrrggggghhhhhhhhh !

 

best,

 

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

[jrgpots]

I am reminded of the Eharmony TV commercial in which the owner guy says to the girl...... "Beth, Do you want fast or forever".

 

So re-worked a bit (a lot) here......... "Do you want good, or cheap?"

 

....

 

A good burner will "buy" you cheaper firing costs, more control over the kiln, and a higher percentage of firsts (assuming no operator error).

 

For that kind of design, go with commercial burners unless you have the time to study burner design, and have a well equipped shop to produce a quality product.

 

I'm also reminded of the saying "pay me now or pay me later".

 

best,

 

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

Can you give us your top 5 choices of "better to best" burners. Also comment on Flat burners, silicone carbide combustion tubes, high velocity burners....

 

Jed