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Kristin_Gail

Troubleshooting This Converted Kiln O' Mine: Taller Chimney?

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Mark C.    1,800

(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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schmism    21

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.com/Bayou-Classic-5HPR-40-Adjustable-Regulator/dp/B0033JF0GE/ref=sr_1_4?ie=UTF8&qid=1393365232&sr=8-4&keywords=propane+regulator

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JBaymore    1,432

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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neilestrick    1,381

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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JBaymore    1,432

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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Mark C.    1,800

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.com/Bayou-Classic-5HPR-40-Adjustable-Regulator/dp/B0033JF0GE/ref=sr_1_4?ie=UTF8&qid=1393365232&sr=8-4&keywords=propane+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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Kristin_Gail    12

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.

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Mark C.    1,800

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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Kristin_Gail    12

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?

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Mark C.    1,800

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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JBaymore    1,432

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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Kristin_Gail    12

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.

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Mark C.    1,800

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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Kristin_Gail    12

I did give him a call this afternoon.  His knee-######## reaction was there is something plugging up the process in the kiln-chimney, but needed more info.  I did send him an e-mail with more photos and videos than a body would ever want or need.  Hopefully we will get this hammered out tomorrow.

 

I came here first because I figured it was a me problem and-or a chimney problem.  But now that we are talking burners so much ... My fingers are crossed he can help me easily.

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Neil, I'm amazed you made it through that ramble. I so appreciate your perseverance.

 

I never intended to make this a wood-burning kiln. I was just going to throw in a little stick or two when I added soda, because someone, somewhere, said it would make the flame longer and take the soda deeper into the kiln. When I wasn't able to get to temp, and the wood was just sitting there, I ended up throwing it in to get me over the hump. I'd rather fire the kiln as it was intended, for sure. But can't figure out how to do it.

 

I have made acquaintance with a very kind man who teaches pottery at a craft college a couple hours away. My next course of action is to do whatever sweet-talking I can to get him over to help (cookies help, right?). Because my constant messing with the burners, the pressure gauge, the damper, isn't getting me anywhere. Same flame, same stalling. Perhaps he'll have the magic touch.

 

And I'm definitely raising that bag wall!

 

Will playing with the burners and damper, with the kiln empty, teach me anything? Or do I need to do it with a full kiln, as I have been?

 

I'm still perplexed about all the cracked pots. Am I just firing too fast through a certain temp range? I loved the idea of blaming it on the accidental crash cool last time, but that obviously wasn't the case.

 

Forever thankful!

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You are having several issues with your kiln.  Firstly, your burners need to be adjusted to burn cleaner with a bluer flame that allows you to increase your temps at a good rate.  Cracking is probably happening because your pieces are subjected to different temps as the kiln heats unevenly.  You might start out with bisqued pots to avoid this obvious problem.  Take the brick out of your exit flue. It is the right size for the interior of your chimney.  The chimney is the engine of your kiln.  Add a pipe, don't worry about sealing it and see if that changes anything.  I do believe it will.  I had a small soda kiln and the chimney was 16 feet high.  The interior of the kiln was 15 cu ft.  Also, forget the sprayer.  What a pain they are.  Look up Gail Nicols from Austrailia, she uses a mixture of whiting and baking soda or soda ash in a paper burrito that you toss into the burner ports.  So much easier and less stressful than spraying and the soda coverage was much better.  Good luck.

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JBaymore    1,432

His knee-######## reaction was there is something plugging up the process in the kiln-chimney, but needed more info.

 

This is why I was saying lose that "venturi" idea in the chimney earlier.  It is NOT helping you.

 

Is that REGULATOR supplied by Marc?  You listed the burners the hoses and the yoke...... but did not say the regulator.

 

best,

 

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

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JBaymore    1,432

The regulator is (theoretically) good for 195,000 BTU flow... so it is just OK for that installation.

 

Just by chance, did you touch the screw assembly that adjusts the outlet pressure via the diaphragm?  I expect not... but covering all bases here.

 

I still keep coming back to the video of the burners running by themselves.  The lack of a decent flame on the Ransome pilots and the VERY yellow and fluffy yellow and poorly directional quality of the MRs is really not looking correcet... even for the MRs. 

 

Another "grasping a straws" kind of thought trying to diagnose from afar.  How full are your tanks and how cold has it been when you've been firing and testing?  If the tanks get too low and it is very cold, the vaporization rate drops off greatly.  But to get that below the inlet pressure for the regulator is HIGHLY unlikely in this case.... but it COULD happen (looking at everything here). 

 

In fact... are you SURE that the valves on BOTH storage tanks have been fully open all the time?

 

best,

 

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

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Marcia Selsor    1,301

It is really difficult to understand all the complexities from all the bits of information and not being able to get the whole picture.

 

Marcia

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Kristin_Gail    12

I know how difficult it is. I just wish I could whisk a few of you out here to figure it out!

 

I never touched anything on the regulator - in fact, I didn't even know you could. It was supplied by Marc. Everything but the tanks came from him.

 

The two 100-lb tanks were just filled to the top, and the valves on them were open all the way. It was about 40 degrees out on the day of the firing. (The first time I fired the kiln, it was cold enough out that the [full] tanks frosted on the outside, but not this time. No frost to be seen. Much warmer this time.)

 

I grasped at the "Maybe propane tanks are under a different amount of pressure in Canada!" straw last night. The husband laughed.

 

Marc did mention that it isn't right, that the dials on the burners only open up to 5.5". Will hopefully chat with him again soon.

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Kristin_Gail    12

.... And the burner manufacturer's response:

 

#1. Fix the bag wall.

#2. Chimney needs at least one foot.

#3. Maybe also try to adjust the regulator - open up the black thing and screw closed completely whatever is inside there.

 

Every point of which everyone else is already saying - including me!

 

After these changes, I think I'll put everything back in that I just took out and light it up next week.  It was all headed to the shard pile, anyhow.  Might as well use it to test out all these theories.

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JBaymore    1,432

Maybe the regulator got inadvertantly shipped to you without the discharge pressure setting set to the expected 11" W.C..  That kind of thing can happen...... no one is perfect.

 

With that "so-called" venturi business in the chimney.... I'm guessing it'll need more than an additional foot of height.  But maybe if the gas pressure is also increased,....... the two will combine to help you out.

 

Venturi operation (and engineering application) is SO misunderstood.  People somehow seem to ignore "science-y" things that apply like Reynold's Number and the Venturi Discharge Coefficent and what a venturi actualy does and how it is used.  Simply narrowing a duct/tube more typically creates what is known as an orifice plate or restrictor plate.  It does not increase flow...... it decreases flow.  Friction losses increase. 

 

The engineering of the necessary CURVES that keep the Discharge Coeffieint high is sophistiocated.  Jagged rectalinear brick changes are not going to do anything but induce turbulent flow and add friction losses, as well as thelosses induced by the change in relationship between cross section of the duct, and the wall contact surface area.

 

If you already have too much volume... it can apperar to help.... but not becasue of any action of a "venturi" impacting it.

 

The bagwall raising and tuning is a "no brainer".... HAS to be done.  Crossdraft circulation requires either a bagwall to distribute the heat energy evenly........ or using wares designed and stacked to do the same job (ala' an anagama kiln).

 

best,

 

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

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