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Troubleshooting This Converted Kiln O' Mine: Taller Chimney?


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#21 Mark C.

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Posted 25 February 2014 - 11:30 AM

Hopefully the slab was at least 4 inches thick and maybe had some rebar or steel mesh in it?? Poured on undisturbed ground?

What can happen sink into ground?

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#22 Kristin_Gail

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Posted 25 February 2014 - 12:02 PM

4" thick.  On gravel. No rebar/mesh.  He's convinced it will crack and move, pulling the chimney away from the kiln.



#23 Kristin_Gail

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Posted 25 February 2014 - 12:40 PM

This is the pilot burning. The t-valve is all the way open, but if I turn it all the way closed, nothing changes.



This is what happens when you turn on the MR-100.



I remember my little B2 burner used to shoot out a clean, straight blue flame when you had it shooting into nothing like that.

This is the hose setup:

http://youtu.be/L8eFfMHpAU4

#24 JBaymore

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Posted 25 February 2014 - 01:13 PM

Unfortunately, by taking the whole chimney down and re-building it. Easy for me to say. :)

 

Dead load on a concrete foundation is a valid concern. The 9x9 chimney has an 18" x 18" footprint. Hardbricks are at about 8 pounds apiece. It takes six per course of 2 1/2 " high. At 8 feet that is already about 39 courses, plus the solid floor courses (lets call that 8 per course for 3 courses). So the brick total so far is about 2035 pounds, so that is a dead load on the slab of about 904 pounds per square foot. Add fopur more feet of hardbricks and that goes up by another 960 pounds to about 2995 or 1198 pounds per square foot.

 

What is the design of the concrete slab? How thick? Is there rebar in it? How large is the slab? How close to one edge of the slab is the chimney?

 

Dropping single wall metal pipe in there is not really a good choice at all. It is going to detreteriorate very quickly inside the jacket of bricks due to the temperature and the corrosive action of the stuff coming from the wares. Plus by inserting a round into a square, you are decreasing the square inches of flue cross-section (ducting) from 9 x 9 square and 81 square inches to at most (for a perfect fit) 9" round for 63.6 square inches. On a kiln you are trying to increase the darft on.... not a good choice. Flow in a pipe is directly related to cross-section also. While a flue XC of 64 square inches might actually be a good size for that kiln if everything else were "good" (better burners, etc.) .... in this case it is likely not. Even 8 inches of round would liekly work... if it was the correct material and if the burners were better.

 

A kiln is a "system". All of the parts work WITH each other. What works on one situation if you look at the components as "stand alone" elements.... may just not work in a diffent situation.

 

Plus single wall metal pipe will lose heat to the environment quickly above the brickwork.... dropping the exit point temperature. Again, on a kiln you are trying to increase the darft on.... not a good choice. At the least use double wall (with airspace) gas appliance venting pipe for the top 4 foot extension. And go larger than 9" diameter to try to maintain the cross section better. Use low temoperature castable to connect the brick and the pipe. The pipe will eventually rust out within the covering castable at the join..... buit it'll take a while. Better yet use an actual insulated flue pipe like the common "Metalbestos".... which has not asbestos in it... but ceramic fiber. It is lined with stainless metal.... will last a LOT longer. And it will maintain flue exit temperature well.

 

Again.... hope this is helping.

 

best,

 

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


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#25 JBaymore

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Posted 25 February 2014 - 01:25 PM

Just saw the last posting that came in as I was doing mine.

 

Yup.... MRs on low gas pressure.  The character of that flame tells it all........ no primary air.

 

Your kiln part of the system will have to make up for the burners weaknesses.

 

Comparing a Ransome to a MR is like comparing a Piper Cub to a Learjet.  And comparing a Ransome to a Pyronics or North American burner is like comparing the Learjet to an F-15.  Ransome casts are true venturis.... far better casting and machining than the MRs that barely qualify to use the term 'venturi'.  The Ransome B-anything will burn blue-er for sure. It is pulling in more primary air at any given pressure setting....with that steadily decreasing (as a %) as the setting gets lower.

 

Where did the regulator on the tanks come from?  (BTW>.. are they yoked..... hooked together with a Y connection then to the regulator?)  Did the GAS COMPANY supply it?  Or is it one you got from Marc?

 

best,

 

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


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#26 Mark C.

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Posted 25 February 2014 - 04:24 PM

(comparing a Ransome to a MR is like comparing a Piper Cub to a Learjet)

I gotta love that qoute

 

 

As far as the concrete work always use rebar and always overbuild it. I learned this the hard way long ago.

One other point you could stablize the satck with angle iron wraped at corners and guy wires or steel supports if you are worries its going to piza tower on you.

 

I'm done with comments/suggestion until I hear about the nespaper draw test with hand torch is chimmney heating it up a tad before lighting newspaper. Please post this results as its fast and almost free. Then we will see what draw you have. This may answer the taller stack needed question in a few minutes

I have on top of my brick work a 12-15 foot stanless steel (3/16 thick ) stack-no rust zero corrosion. Its 12 inch ID from a pulp mill scrap . My salt kiln as one as well only 8 inch diameter-no yada yada either. Both are on top of 8-10 feet of brickwork.

Guyed with stainless wire-no rust yada yada.

Mark


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#27 schmism

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Posted 25 February 2014 - 04:54 PM

Looking at the vid of your hoses,   The regulator your useing from your tanks looks to be a standard RV style regulator.  Those regulators are preset for 11" water column (wc) usually only good for 100K-150K bTU/HR

 

As Jbaymore stated, those MR100 should put out twice that.

 

In short I'm fairly shure your regulator your useing is not allowing enough gas to pass through it.   (not enough volume)   

 

a manually adjustable regulator is a cheap thing to try before you tear into rebuilding something on the kiln.   

 

http://www.amazon.co...opane regulator



#28 JBaymore

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Posted 25 February 2014 - 05:01 PM

The regulator your useing from your tanks looks to be a standard RV style regulator.  Those regulators are preset for 11" water column (wc) usually only good for 100K-150K bTU/HR

 

That's right where I was going with those questions. ;)

 

best,

 

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


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#29 neilestrick

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Posted 25 February 2014 - 05:37 PM

According to the Ward Burner site, those burners come standard with orifices for 11" water column pressure. If you go to a high pressure system to increase the BTU output, you'll have to order non-standard orifices.


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#30 JBaymore

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Posted 25 February 2014 - 06:02 PM

According to the Ward Burner site, those burners come standard with orifices for 11" water column pressure. If you go to a high pressure system to increase the BTU output, you'll have to order non-standard orifices.

 

I'm more concerend with the actual pressure being "seen" by the burners from watching the videos. When a regulator is put in the position of being over drawn (exceeding capacity) by the units drawing the gas, they have the tendency to drop pressure as we ll as volume suddeenly. I'm thinking that the regulator there is not sized to the required volume of gas.

 

The regulator in that above link is for high pressure usage. As you say, if the orfices are not changed out....... problems.

 

And every burner has a pretty narrow range of orfices that put the expanding gas flow coming out of the hole close to tangental to the narrowest point of the throat. When that gets too far out of whack.... the percentage of primary air that the burner unit can entrain goes down from even the target design specs.

 

Core concept of industrail kiln design work: Air Handlig Capacity.   It is not about the fuel... fuel is pretty easy. It is the AIR that is the place that the design revolves around.  First thing they teach in combuistion courses.

 

best,

 

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


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#31 Mark C.

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Posted 25 February 2014 - 06:14 PM

Looking at the vid of your hoses,   The regulator your useing from your tanks looks to be a standard RV style regulator.  Those regulators are preset for 11" water column (wc) usually only good for 100K-150K bTU/HR

 

As Jbaymore stated, those MR100 should put out twice that.

 

In short I'm fairly shure your regulator your useing is not allowing enough gas to pass through it.   (not enough volume)   

 

a manually adjustable regulator is a cheap thing to try before you tear into rebuilding something on the kiln.   

 

http://www.amazon.co...opane regulator

I use that exact same regulator on my 3 burner propane saltwater cooker for salt kiln.(we heat water and spray salt saturated water into kiln) The burners need larger volumes and this supplies them.

I'm guessing this simple fix may be a solution.

Mark


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#32 Marcia Selsor

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Posted 25 February 2014 - 06:36 PM

You could probably get by using a pipe to extend your height.
or flu liner tiles are much lighter than brick.

Marcia

#33 Kristin_Gail

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Posted 26 February 2014 - 09:51 AM

It's about 15F out there, and breezy. We started a little fire in the chimney to warm it up slightly, the fire went out, then took this video:



Then we threw some burning newspapers into the chimney, and took this video:



It drew both times, no? But better the second, I think.

The newspaper actually drew into the chimney *far better than the pilot does*, when it runs after the chimney has been warmed up.

#34 Mark C.

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Posted 26 February 2014 - 11:17 AM

The kiln is drawing the flames in =which is a good sign

How about the regulator most feel its not leting enough gas thru-I tend to agree you need a high volume  regulator like the one posted above at amazon link.

I think thats the next move as well as building a higher much bag wall.

Mark


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#35 High Bridge Pottery

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Posted 26 February 2014 - 12:53 PM

Kilns... Simple and very complicated at the same time. Great reading all this information. Good look with your diagnostics 



#36 Kristin_Gail

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Posted 26 February 2014 - 01:09 PM

The kiln is drawing the flames in =which is a good sign

How about the regulator most feel its not leting enough gas thru-I tend to agree you need a high volume  regulator like the one posted above at amazon link.

I think thats the next move as well as building a higher much bag wall.

Mark

 

Does that mean I'd need to change the orifice?  I'm finally beginning to get confused.

 

It does mean I maybe don't need more chimney, if I have the draw, correct?



#37 Mark C.

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Posted 26 February 2014 - 03:19 PM

Your orifice needs to be for Propane not natural gas. Change out your regulator as mentioned in this post

from schism-

(Looking at the vid of your hoses,   The regulator your using from your tanks looks to be a standard RV style regulator.  Those regulators are preset for 11" water column (wc) usually only good for 100K-150K bTU/HR

 

As Jbaymore stated, those MR100 should put out twice that.

 

In short I'm fairly shure your regulator your useing is not allowing enough gas to pass through it.   (not enough volume)   

 

a manually adjustable regulator is a cheap thing to try before you tear into rebuilding something on the kiln.   

 

http://www.amazon.co...opane regulator

 

If this works  it will fix the burner issues and we can move on to the chimney issues if its still and issue-taller would not hurt you but if the draw is good then its worth trying firing again with the regulator change-The burners are yet to be right 

I cannot say if the chimney is tall enough as your burner issue and bag wall issue is enough for now to change. As long as you have good draw I'd go with it until your try after fixing these other items-The burners need to work better and the high volume regulator

should fix that issue you can test it after installing it. The bag wall needs to be taller and the target bricks are a great idea as well. Make these changes and test it. I have never had a kiln that I had to warm the stack to work -the kiln usually starts a draw within minutes of lighting. Take that brick out of flue opening as well or at least make it 1/2 size. Remember to many changes and you may still not know wants going on so keep it basic-open the flue- change regulator- raise bag walls- add target brick (or part of a brick)

You want the flame to go up into load then at rear down into flue

this is the basic downdraft design. You could add some height to stack as it will not hurt you-and you may have to later its an unknown at this point.

ain't ceramics fun

When this kiln works right all this will long forgotten.

Mark


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#38 JBaymore

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Posted 26 February 2014 - 03:27 PM

Writing quickly from school...... students are working on a project .... triaxial blends.

 

The regulator listed above is a high pressure regulator.  Your burners (apparently and hopefully from Marc) have orifices drilled for low pressure gas. If you use high pressure gas thru a low pressure sized orifice, two things happen.  One is that the amount of gas that comes out of the orifice in a unit of time (per minute or hour) is significantly greater than at low pressure (remember the pressure conversion I listed above).  Second, the WAY that the gas will squirt out of that orifice is affected , so that it affects the flow at the throat of the venturi aspect of the burner...... DECREASING the percentage of primary air it will entrain. 

 

So while the BTUs per hour coming out of the burner will go up if you leave the orifices the same but increase the pressures, the ability of the burner to realize (combust) those additional BTUs will not go up.  So you are still gonna' be dependent on secondary air and the in-kiln mixing function to do that job. 

 

I'm thinking that unless you want to change out the orifices, that you should look more at a low pressure (11" Water Column) HIGH VOLUME regulator.  Regulators have two ratings...... delivery pressure and total gas volume that they can pass in a unit of time (minute / hour).  The issue here is likely volume... not pressure (see my comments above).

 

That being said, one of the great advantages of having propane over having natural gas is the ability to easily run a high pressure system.  There ARE advantages to be had.  Most natural gas supplies, unless you live in an industrially supplied zone, max out at 11" WC.  Some places max at 4" WC.  Propane has a high tank pressure... so you have lots of available pressure to work with. 

 

High pressure gas does impart some kinetic energy to the flow of gas and air out of the burner nozzle, thereby acting to lessen (slightly) the impact of the kiln system's own draft characteristics.  Also, well designed venturi burners for high pressure operation can entrain more percentage of primary air than the low pressure versions can.  (Not much of an issue with the MRs....... low or high pressure, they are not all that great.)

 

So you would gain SOME advantage by changing to high pressure.  But you'll have to change the orifices, otherwise the burner gas output will be so high, that the burners will be VERY touchy to operate, and low settings will be very problematic.  Additionally, you'll have to run the "high pressure" set so low at the max, as to not gain any advantage of the higher pressure on the "driving forces" on the flow thru the kiln.

 

And we still are back at needing MORE AIR with those burners..... no matter what you do.  Kinetic energy from high pressure can help a bit.  As can more flow induced by the chimney (larger exit flue opening, taller stack, higher exit point temps). 

 

But the first place to go is finding out if the existing burners are getting the gas flow that they are supposed to get.  You should get the specs on the existing regulator, and make sure it is delivering what you THINK it is.  If it is wrong......... then you can ddecide where to go.

 

Don't treat the disease until the diagnosis is in based on the tests.

 

best,

 

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


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#39 Kristin_Gail

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Posted 26 February 2014 - 03:49 PM

The regulator is a Gas-Flo Model GR-9950

 

And I see how that the gauge is listed very clearly as H20, not PSI, right there on top.  I'm so sorry for not knowing that from the get-go; would have saved a fair amount of confusion.

 

The entire system came, built, from Marc Ward.  Hoses, connectors, burner already clamped to pilot burner, etc.  I realize I need to call him, but am somewhat afraid to do so.  I always end up feeling ... well, not very bright.  I don't even really know what I'm asking this time besides, "Why doesn't this thing work?"  Poor guy.  I'm certain he talks to 20 mes every day.



#40 Mark C.

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Posted 26 February 2014 - 04:02 PM

You should really call him as he knows his stuff and he sold it to you. This call may solve all your burner issues in mere moments.

You still will need a taller bag wall etc but fix the burner isssue as John says 1st.

Mark


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