Natural gas programmable Geil16F shutting off at 1900 degrees

[Potterbabe]

I own a natural gas Geil 16F reduction kiln which I’ve been firing on the same program for years.  During the past 5 or so firings, the left front quadrant was slowly oxidizing after each firing.  Thinking it might be the burners I cleaned all of them, loaded my kiln as usual, set the same program  and found that the kiln shut itself off at about 1900 degrees - twice .  

My kiln is enclosed in a shed designed to keep wind out, my stack has no variables and Im pretty sure the thermocouples haven’t died.  Can anyone help me here?

[Mark C.]

I would use a letter drill bit and hand spin into the orfice as gas over time leaves deposits and the orfices become smaller. You want the right bit so work up in size (I forgot exactly what letter size but Geil will tell you if you call them)

[neilestrick]

What sort of burner setup is it? Does it have a ring pilot that goes around to all the burners? Baso valve(s)?

[Bill Kielb]

6 hours ago, Potterbabe said:

I own a natural gas Geil 16F reduction kiln which I’ve been firing on the same program for years

Which controller do you have, the ramp soak - high limit, proportional or full blown atmospheric? Post a picture if you can. Shutting down at 1900 degrees indicates a safety of sorts. Either high limit or your pilot sensing dropped out. Since this happened twice at 1900 degrees it points to high limit, post your program.

Uneven reduction points to air leaking in which usually indicates the management of the atmosphere and the pressure in the kiln. Which can be damper operation, change in kiln power: gas pressure, burners, excess leakage, restricted flue…..

Natural gas should be very clean, (properly dirt trapped) and screens built into the the gas valve ought to catch any real small stuff. Cleaning orifices is fine, usually a spider web / dust. Normal recommendation would be NOT TO enlarge them even by a few thousandths so most often you will see a toothpick or soft copper wire suggested. Also ……… blow them out opposite of the gas flow. You need to remove the orifice to do this so the dirt is not blown back into the pipe only to return later stuck in the orifice.

If you have restricted orifices it’s usually obvious comparing one burner flame to the others, especially natural gas. Very blue flames are achievable. Not so much with propane.

BTW: it is common for gas kilns to be FULLY supervised throughout the firing. Set it and forget it more of an electric kiln thing. For gas check on it every 15 to 30 minutes seems to be the compromise to100% supervision.

 

Edited June 11, 2023 by Bill Kielb

[Potterbabe]

I want to add that I’m loading and unloading a Geil with natural gas.  This kiln has the automatic damper system and microprocessor programmable temp control and fully vented.  The owner is having serious health issues with problems lifting anything heavy. I’m taking possession of the kiln and moving , setting it up for propane in late August.  My friend is working with a commercial heating tech who sets up her programs and starts the kiln- he thinks it might be the oxyprobe is degrading so I contacted Geil and by my description of the problem Paul  thinks it may be  with the High Limit controller or pilot sensing device dropped out.   The kiln is 13 years old and has been fired maybe once a month or less which is why I am pleased to finally own this.  Visually it is in beautiful condition and in a clean environment.  However it has never seen any maintenance for the life of the kiln.

when a section of the kiln slowly began to oxidize I just thought that it was a burner cleaning issue.  The commercial heating tech cleaned the ports with confidence and that’s when the kiln began to shut down prematurely .

When I finally take possession of this kiln I am going to disconnect all the programmable stuff and just fire it manually with cones because replacing any parts of the programmable component is just too expensive and my experience is firing a kiln manually.  However my friend wants to fire it one more time and I’m not comfortable doing a manual firing without running the kiln several times with cone packs to establish a cone 10 reduction firing.

I know this is a lot to read, but I’m searching for answers prior to moving this kiln.  Any natural gas to propane advice should be helpful too-I have the propane conversion kit from Geil ready to install.

[Bill Kielb]

So my thoughts above seem to align with Paul’s…… shutdown by high limit or ……. Programming. I have experience with various Geil kilns and depending on configuration, pilot safety can be a bit touchy..

My observation converting these kilns is you may need to increase the pilot orifice size when all is said and done to obtain a stabile pilot and stabile operation so the kiln does not shut down unexpectedly in pilot safety.

Notice the before and after photos below. Before = lazy soft flame along the pilot bar, After = robust better defined flame.

Additionally we built monitors for these so I should have decent relatable engineering with respect to potters atmosphere on the Geil probe as well as oxyprobe. They are very useful in hand firing and following a schedule. The values for each are a bit relative so if you get to a point of using the probe I may be able to help quantify what we found. Picture of the Geil relative reduction scale below as well on one of the monitors.

Oh last piece of advice, get the operating pressure correct. This will most likely operate propane 0-14 inches max so a two stage regulator from the propane tank and the orifices sized for inches of pressure.

Edited July 21, 2023 by Bill Kielb

[neilestrick]

What sort of thermocouple/flame sensor system does it have? Typically when gas kilns shut down unexpectedly it's because of the pilot/thermocouple system. Either the flame is inadequate like Bill showed, or the TC/flame sensor is worn. It's difficult to tell if the thermocouple/flame sensor is worn, so it's easiest to just change it out and see if that helps. Sometimes it's a simple as the TC is no longer properly in the flame path for whatever reason- getting bumped, warping bracket, etc.

[Mark C.]

Paul is your best source of advice. Funny thing is I'm moving this very kiln myself this summer to my place. Its a 16 cubic soft brick Geil. Its only got the older DD system that holds whatever temp you set asa hold themp, not the auto damper or the reduction control. Much less auto controls and I'm converting it back to natural gas-maybe  I could get your orfices for Natural gas???