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Gas kiln stalled . Why?


Linda A
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If you can make your exit flue wall undereath solid, and all the way up the shelf bottom as this green...

1901069467_1573053938_thumbnail(14).jpeg.489c0d6b8bc1e04e9a3e9086d0a406642(1).jpeg.15b99de464d8b2559ce18829617cda59.jpeg

It will force the flame up the side and give it a longer path of travel.

Your flame is going to follow the path of least resistance, and if that chimney draws well, when you open the damper, that will be directly around that first brick.

I reckon your chimney draws well!

Sorce

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54 minutes ago, Sorcery said:

If you can make your exit flue wall undereath solid, and all the way up the shelf bottom as this green...

1901069467_1573053938_thumbnail(14).jpeg.489c0d6b8bc1e04e9a3e9086d0a406642(1).jpeg.15b99de464d8b2559ce18829617cda59.jpeg

It will force the flame up the side and give it a longer path of travel.

Your flame is going to follow the path of least resistance, and if that chimney draws well, when you open the damper, that will be directly around that first brick.

I reckon your chimney draws well!

Sorce

Ok. These changes seem simple enough..the only thing I have a question about is the brick above the damper. Should I have a diverter brick above the damper also?

Thank you

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On 10/9/2020 at 6:52 AM, Mudfish said:

Thank you, Mark. I plan on getting these details done and I will do another test fire this weekend. I will post results 

well here we are and after 12 hours the kiln is still stalling. it reached 2110.. It started to stall around 1950- 2000* or so. I have made all the corrections. shelves were cut about two inches-one inch each side and about two inches off the edge opposite the exhaust port. I set up the firebox exactly like you showed in the picture. Do I need three burners instead of two?

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1 hour ago, Mudfish said:

Do I need three burners instead of two?

If you go back a few posts here, In my view we really need the gas pressure, etc... and a few pics As previously suggested. It’s hard to speculate without that info. Intuitively guessing at flow often  does not solve the issue. We really need to establish what your burners are doing and how much output you actually have. What is the highest pressure you run them? Is the primary air shutter open so the flame is oxidizing? Stuff like that.

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58 minutes ago, Bill Kielb said:

If you go back a few posts here, In my view we really need the gas pressure, etc... and a few pics As previously suggested. It’s hard to speculate without that info. Intuitively guessing at flow often  does not solve the issue. We really need to establish what your burners are doing and how much output you actually have. What is the highest pressure you run them? Is the primary air shutter open so the flame is oxidizing? Stuff like that.

how do I measure pressure?

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23 minutes ago, Mudfish said:

ok. Maybe this is another stupid question but does a guage just measure the pressure or does it also regulate it to proper pressure?

The gauge measures the pressure. The kilnmaster fires by turning the pressure up as needed. Similar to the accelerator on your car. More gas, car goes faster. Gas kiln, more gas firing goes faster.

its actually fairly simple once you get the hang of it. Your burners will only put out the amount of heat they are rated at a certain pressure. We need to make sure they are performing as anticipated. If you are not raising the pressure during your firing then it’s gonna be really hard to fire. 

Pictures of how you are doing this would help a bunch

Imperial measure

  • Natural gas = pressure in inches of water column
  • Propane = Pressure in pounds per square inch

Nat gas pic below

2E0660CB-F90E-40A9-A7D5-A1BA2AC0C77F.jpeg

Edited by Bill Kielb
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13 minutes ago, Mark C. said:

o 1 ,1/4 inch for 30 feet then 1 inch for 60 feet-90 feet total from meter (regualr small house meter??)

two MR  venturi 75,000 burners right

Not sure I understand the question but If a friction loss and piping thing we need type of gas, supply pressure, operating pressure and some idea of fittings. Then pick from a table for acceptable drop for 150000 btu max output. At what pressure do the burners put out 75k?

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Natural gas at 1/4 pound (7 inches water column ) need a large pipe for long runs-hers is just that  a long run.

Its the lkow pressure (many do not work with or understand low presure high volume NG  gas)

If you are a propane person for example this does not make sense 1/4 pressure and large gas pipes. what the heck is all that??? I need presure and small pipe is fine.

I had a kiln once that was 35 feet away from meter with 1 1/4 inch pipe and it was 4 burners the gas company speced it out for me in 1973. I did the piping and kiln did not work at 1/4 pound presure. I replaced it all with 2 inch and walla worked fine.Now I only use 2 inch for 1/4 pound kiln work.Mt kiln has 8 burners and is 40 feet away. My salt kiln is 140 feet away with 4 burners and 2 inch is fine supply line. You can usew smaller pipe but you need to control the length and have a larger volume suppy from the meter.

Granted the burners where a bit more thirsty than the pair poster has of  MR750s. But long gas lines (90 feet) is a long ways for 1/4 low presure so to make up for that a larger pipe size is needed 

By the way this is a bit out of context as I was answering her on the status update (thats why the 90 feet deal was a qoute from poster) and wanted to bring it here for future reference 

Now the meter size is also important as small house meters pass less volumes than say my Sprague 1000 which you see outside most large fast food restaurants -large volume low presure meters are biger than house meters. Poster I think has a small house meter ??-good for 1 stove  a  home heater -water heater and a small other gas appliance. 

I think that 90 feet with those smaller burners is ok pipe size wise. what we do not know is the burners full on and what presure is at the burner and if there is enough volume of gas to supply the burn and still agin temp. lots of unknowns

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7 hours ago, Mark C. said:

think that 90 feet with those smaller burners is ok pipe size wise. what we do not know is the burners full on and what presure is at the burner and if there is enough volume of gas to supply the burn and still agin temp. lots of unknowns

I skimmed through these several times, I can’t find any reference here but maybe I am missing it. I am sure it’s somewhere.
Sizing piping,:  use a table know the actual pressures, count your fittings and valves and make sure everything has the capacity rating you need or greater. Give yourself some reasonable percentage to over size the design losses say 10- 20%. Guessing and rule of thumb are fine but confirm with the tables  and the actual numbers to save yourself the headaches. All that stuff today is available on the web and fairly easy to do IMO.
I agree, I feel I have no idea on how either of these kilns are being fired and whether it is propane and if the burners are orificed for low or high pressure.

Edited by Bill Kielb
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4 hours ago, Mark C. said:

That kiln is natural gas with 90 feet total pipe (30 feet of 1 1/4 and and 60 feet of 1 inch)  fired at 7 inches with two MR 750 burners.

I think that will supply those burtnmers ar 1/4 # presure.Its a hunch.

Yes it is a residential meter. I don't really understand the rest of your comments, but I will refer all this to the guy who has done the gas line work. All this is way beyond me. Thanks guys. I will order a natural gas gauge from somewhere. Mark Ward probably.

Thank you. 

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Just install the gauge so it always measures the pressure to the burners which should be downstream of All valves and regulators. Then you should be able to Confirm you have the energy available and learn how to fire by pressure. We have plenty of ready made free spreadsheet logs we can share as well if you eventually have the need.

6F603A06-256F-481E-A3B0-584C19F819BA.jpeg

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13 hours ago, Bill Kielb said:

Just install the gauge so it always measures the pressure to the burners which should be downstream of All valves and regulators. Then you should be able to Confirm you have the energy available and learn how to fire by pressure. We have plenty of ready made free spreadsheet logs we can share as well if you eventually have the need.

6F603A06-256F-481E-A3B0-584C19F819BA.jpeg

Thank you, Bill

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