T Burner tuning

[Trees]

I have a recently built propane tank forge with two 1/2" Frosty T burners.  When I fired it up tonight (fifth firing), one of the burners was behaving a little differently than it had before.  It was much quieter than the other one and the flame was weird looking, not really staying together.  I thought it must be a blockage in the fuel supply, so I detached the propane hose from the top of the burner to see if the orifice had some debris in it, but the MIG tip looked clean (gave it a couple swipes with a torch tip file anyway just in case), and I couldn't notice any obvious fuel restriction on that side of the system.  Could it just be that the MIG tip extension in the T needs adjusting for fuel/air mix in the T, maybe it somehow got bumped deeper or shallower relative to the air intakes?  Or does it look like it must be a fuel supply constriction somewhere?  When the forge got up to heat, metal on that side did seem to visibly scale up a lot more, so I'm guessing that could either be a sign of fuel supply blockage or a MIG tip that's too far back?

Any insight or suggestions where to start would be greatly appreciated.

Here's what it looked like tonight - the naughty burner is in the foreground and the flame is mostly visible as  the blue on the forge bottom and a little broken blue flame trickling down the wall, compared to the other side which is a uniform lighter blue cone (though hard to see in this picture):

When I turned off the better functioning burner:

 

Another shot from when it was a bit hotter, the flame in the foreground is almost making a dark blue halo on the floor:

The floor here:

 

And here's some pictures from previous firings when it was behaving differently - I haven't (at least knowingly) adjusted the burners between then and now:

[Frosty]

The cool circle in the center of the flame on the forge floor is caused by the flame being long and impinging on the floor before combustion is complete. If you can pull the burner farther out of the forge the cool spot will diminish and eventually disappear.

If that doesn't work we'll have to look at the other probability and lean it out a bit. It looks to be burning a LITTLE rich but that just may be an effect of how the flame is contacting the lining in the burner port. 

Frosty The Lucky.

[ThomasPowers]

Can we see a picture of the gas getting to the burners?  I've seen some oddities where folks had burners inline on the supply instead of the supply going to each burner equally.

[Trees]

Thanks Frosty - I should have mentioned that the other troubleshooting I did last night was to push the burner in and out and tilt it as it was running and it wasn't changing anything.  Both burners were installed about 1/4" into the cast (KOL) nozzles.  The forge is 2" kaowool covered with a 1/2" KOL & Plistix on top. The burner ports were cast using a wood form with a 1:12 slope for nozzles.

Thomas, here's some photos of the setup (I'm not lighting it in the wood shop).  Problem burner is on the right.  I didn't think the kink in the supply hose above the burner would affect the burner that way - It looks to me to be a pretty minor constriction in front of a much smaller orifice. But I might be wrong on that one:

Removing the burner mixing tube I may have found the culprit! I must have forgotten I put on a third coat of Plistix since the last firing (see the last pic in the first post where both burners seemed to be functioning much better).  The port on the funky burner has some pretty big clumps of plistix making the nozzle rough and irregular.  I wouldn't have thought it would affect performance that much, as I think even with the bumps the nozzle is still wider in ID than the mixing tube but is that the most likely culprit?  I probably won't get a chance to test fire it tonight after scraping the plistix clumps off as it's pretty stormy over here, but will post back when I get the chance.

Maybe while I'm at it I'll shamelessly plug my other post on the Plistix application as it was giving me fits and I still haven't figured out what I was doing wrong with it: https://www.iforgeiron.com/topic/68680-clumpy-plistix/?tab=comments#comment-747713

Here's the rough port followed by the cleaner one where the other burner seemed to be functioning OK:

 

[ThomasPowers]

Thanks for the extra pictures;  much like an ecosystem; everything seems to affect everything else and often our first guess at what's wrong may be totally in the wrong spot!

[Buzzkill]

Here's a way to narrow down the potential problems:  switch the fuel input lines for the burners.  If the problem stays with the same burner then the issue can only be in the burner itself (or where the burner enters the forge).  However, if the problem switches to the other burner, then you have a supply issue.  Once you can narrow the possibilities down a little we can work through them one at a time until we discover what caused the change.

[ThomasPowers]

If no change switching the lines; then do the same with the burners---should show if the clumps were the problem!

[Frosty]

You'd have to crush the propane line to effect flow enough to effect the burner. compare the ID of the mig tip to the ID of the hose, I run four 3/4" T burners through 1/4" pipe, then to 1/4" copper fridge tubing. You can open one or more of them without the one that is running flickering.

Yeah, I think the rough plistex could be the culprit. The less turbulence in the burner the better and even that little bit could disrupt the flame.

I don't know how I missed the thread about the cracks in the KOL liner in your forge. YES Plistex will cement them together, I'd mix the first coat a little thinner so it'll penetrate the cracks. I suppose it's a little late now but. . . 

Frosty The Lucky.

[Trees]

Thanks everybody - great suggestions. I'll report back when I can test them out. 

Frosty - I did try patching the cracks with Plistix, but I would be most interested to hear feedback on whether anyone else has had issue with the plistix clumping and drying instantly as it's as applied, and mostly drying into a powder that just dusts off as soon as the surface is touched. All coated parts of my forge are constantly shedding fine plistix dust. 

Changing mixing consistency, buttering, etc. didn't seem to help.

Just wondering if that is normal for plistix, or user error, or a bad batch... 

[Mikey98118]

17 hours ago, Frosty said:

If that doesn't work we'll have to look at the other probability and lean it out a bit. It looks to be burning a LITTLE rich but that just may be an effect of how the flame is contacting the lining in the burner port. 

 

actually, it may already be slightly tending to lean (it's very dark). What the flame looks like to me is just too strong. Cutting the gas pressure back is an easy way to find out if that hunch is false or true.

[Frosty]

How thick did you mix it? Plistex should be about the consistency of interior latex paint to kiln wash a forge. I'd make it a little thinner for the first coat to cement those cracks in the liner.

It should NOT be lumpy nor dry instantly, you need to let it dry for an hour anyway before applying the second coat.

I abide by Mike's evaluation of  the flame's fuel : air ratio he's better at it than I.

Frosty The Lucky.

[Trees]

Latex paint was the thickness I went for on average. I also tried thinner and thicker to see if it would help but the results were always the same. It would clump easily upon contact and dry (almost on contact) to a loose powder that would slough off, no matter how thick or thin the coating or how long I left it to dry...

Like this:

Each coat was more or less the same, even when firing between coats.  I get a constant dusting of fine plistix dust every time I pull out the forge or something rubs against one of the surfaces.

Mixed it well each time too. Noticed it felt extremely gritty when mixing, I'm guessing that's normal, but really wondering if I got a bad batch the way it behaves when it dries...

Another weird thing. I tried mixing a batch that had dried overnight in the mixing container with fresh water the next day, and it behaved the same as the stuff freshly mixed from the powder.

[Frosty]

I've only used it a couple times . . . well, applied it during the club forge build and it went on like thick latex paint and made a smooth coating, the brush marks smoothed naturally. 

Did you butter the brick first? That makes a real difference in how well it bonds to what you're applying it to or so basic masonry practices shows.

Frosty The Lucky.

[pnut]

I tried mixing it by hand and it didn't want to work. I used a blender from the thrift store to mix it before applying the next layers. It was much smoother. 

Pnut

[Trees]

Yep, buttered the surfaces first but no difference. 

The thrift store blender idea is great - thanks Pnut. 

The cloud of fine plistix dust coming out whenever something rubs a coated surface in the forge makes me feel like I should be using a respirator whenever I use it... 

Might make sense to buff off with a scotch brite pad and vacuum as much of the poorly bonded stuff as possible before trying another coat with the blender trick. 

[Frosty]

I'm going to have to call Pat and find out what Plistex he bought specifically. He bought in bulk on the club nickel for the burner / forge build clinic. A pallet of K-26 firebrick reduces individual price under $2 and he uses them and Plistex in his business casting bronze and teaching.

What we used mixed like plaster of paris and I don't recall it being noticeably gritty. Once dry, yellow heat fired what we used like matt glaze on pottery and it's been in daily use by some of the pro bladesmiths for a few years  now.

These differences are too great to be variations between batches, I need better info on my end. I've thinking of Plistex as being plistex, period but different types and properties is probable. I'll have to find out more.

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Did you get Plixtix 900F? Have you read this?

https://www.iforgeiron.com/topic/62088-plistix-900f-kiln-wash/

 

[Trees]

I'm assuming it's Plistix 900 - I ordered from Wayne and the bags were just labelled as Plistix.  I asked but he hadn't heard of this happening and didn't have any suggestions for why it's behaving weirdly.

I had read Glenn's thread, but hadn't noticed the last post:

Quote

According to the manufacturer, once at room temp you can apply the Plastix 900F to the dry refractory, let  the Plastix 900F dry, and add fire to the forge.

I wonder if me first 'buttering' the surfaces with water may have been the cause of it not sticking?

[Irondragon Forge ClayWorks]

Maybe, if you wet the bricks with too much water. I noticed in one picture a bottle of Windex (glass cleaner), didn't use that did ya.

[Trees]

Good eye - it's a repurposed Windex bottle with just water...

I sprayed a fair amount of water on first, but the bricks just suck it up so fast they didn't seem very damp before applying the plistix...  Same with KOL inside the forge.

[Frosty]

Nah, you can't get the brick too wet, masons I used to work with dipped brick in the water bucket and if it wasn't dripping when they took it out they'd let them soak. Some pallets had them with several bricks in the bucket soaking in rotation as they laid them. They usually didn't need to soak more than a few seconds but those guys didn't spend a few seconds laying a brick so the ones soaking were maybe 20-25 seconds in the water.

If the brick just soaked the water up and didn't have surface moisture when you applied the wash it was too dry. Sounds to me like the wrong kind of fire brick. Before I knew about proper kiln washes I was experimenting with Kaolin clay on hard fire brick and found dipping the brick in water and brushing the kaolin "slip" on worked fine. The kaolin wasn't a good kiln wash but spritzing or brushing water on the brick wasn't working like old school mason dipping.

I was using 3,000f hard fire brick and it absorbed only slightly more water than standard red brick.

I haven't heard back from Pat, I'll try again later.

Frosty The Lucky.

[Trees]

Well I never did figure out the issue with the Plistix, but I did figure out the burner issue I started the thread with...  For some reason I can't understand, if I start up the forge with the regulator set at 4 PSI or higher, most often one burner will have the flame starting way out of the burner port and into the forge with a little cold spot on the forge floor where it hits, and the other one the flame will light up the burner port and no cold spot on the floor.  But if I then drop the regulator down to about 2-3 PSI, the farther out flame jumps up into the burner port and the port starts glowing like the other one, then both burners behave normally when I turn the regulator back up again.

So starting like this at 4 or 5 PSI (there is a flame coming out of the near port, it's just far out and splashing onto the floor:

Then turning the regulator down and the other flame jumps up into the burner port and the port starts glowing:

Then right away I can turn it back up as high as I want and the flame stays put:

Has anyone else had this experience?  How do those flames look in the last picture?

 

[Frosty]

Who's plans did you follow making the burners? What are the specifics, eg. parts and sizes.

If they behave differently you didn't match them very well when you made them or plumbed them. 

Properly tuned psi is meaningless within operating range.  Knowing propane psi has only one useful function, repeating specific temp or conditions within the forge. 

Frosty The Lucky.

[Trees]

Hi Frosty, I followed your plans in the T-burner thread.  In the 4th post there are pictures of the 1/2" burners, using 3/4-1/2" tees, 4.5" long 1/2" nipple, and 0.023 MIG tips. They seem to be drilled nice and straight.

I should clarify that once I turn down the regulator very low, both flames stabilize immediately every time for the rest of the session, no matter what pressure I adjust the regulator to afterward.  I understand the PSI numbers are meaningless but I am using them for repeating adjustments - there is a point on the gauge (about 4PSI) where if I start above it, one of the burners has a weird flame that will stay weird unless I bring the pressure down below that point, after which it is stable no matter how it gets adjusted.

I think it's fine, as the forge seems to work fairly well once I figured out to drop the pressure down below that point just after lighting it. I'll hear the flame change immediately then I know it's good to go.  As this is my first forge, I am also happy to be told by those with more experience that it's not fine and I've made a mistake that can hopefully be fixed.  My best guess is that behaviour is something to do with the forge atmosphere maybe caused partly by the shape I cast the burner ports - maybe I should have made them widen a bit quicker than 1:12 over the 2.5" to the forge interior? 

In the last picture in my last post above, do those flames look OK to you?

 

[Frosty]

Would the weird burner be the one closest to the camera in the last pic? 

Those are two very different flames though both appear to have a pretty good fuel air ratio. Perhaps a little rich but pretty close.

How close to the end of the mixing tube in the T are the jets? (end of the mig tips)

Different shaped flames from two "same make" burners means there's something physically off in the poor performer. Yes?

Frosty The Lucky.