Pic heavy, insulation problems

[Trevor84]

Hello all, my first post here. 3rd forge build. First was soft brick pile and (worked well) , second was the Zoeller "simple forge" (too big) 

I'm looking for some guidance, possibly too late unfortunately. I'll start with the description of my build as best I can and then ask a few questions. 

1/8 steel plate for the body

2600 deg soft fire brick floor and doors 

Two 1" layers of ceramic wool 

2nd layer Rigidized (400ml too much

1/4-3/8" kast-o-lite 30 let sit in wet bag for 24hrs (first coat) 

1/4-3/8 kol flame face floor

Apx 300-350ci and interior

3/4" Reil style burner with a mig tip mod

I've only fired this up to dry out the Rigidized and to dry out(?) the KOL (at least I thought I dried it out) . I've dragged the forge back and forth to carve a groove for the base of the forge to sit in the soft brick floor to seal the joint. With the forge running I held my hand at the joint where the body meets the floor and feel no heat escaping through it. After running the forge for 5-10min in short runs at 2.5- 5-10-15psi the whole outer body has gotten almost too hot to touch evenly on both sides not just the side the burner faces. I have no dragon breath shooting out the ends, doors open or closed. 

I am at a loss to why this is happening the interface of the upper to floor does not seem to be leaking exaust. I only rigidized the second layer of wool but could I have over wet it so steam inside the wool is super heating the steel shell I used 400ml apx of the rigidizer? 

Should I worry about the flame heating the steel at the base of the upper shell that holds the insulation......? The paint on that part isn't even burning though. Should I gouge a deeper trough for the upper body to sit down into? 

With all this keep in mind I hadn't even gotten to full forging temp. 

I hope this makes sense and sorry for the length. I'll try to shrink the photos if possible from my phone. 

 

 

 

 

Not sure if these links will work, I'm new to you tube. 

[Buzzkill]

Are you concerned because the outer shell of the forge is getting hot?  Though I don't claim to be an expert, I have built several propane forges with different configurations and burners.  The one thing they all have in common is that when they are at operating temperatures the outer skin gets too hot to comfortably rest my hand on, but not hot enough to burn me if I touch it briefly.

If your outer skin gets hot enough to burn the paint or gets glowing hot (other than around the openings) then you have a problem.  There are probably some people who have built forges where the outer skin remains cool enough to rest your hand on when it's up to temperature, but I am not one of those people. 

I did not see any obvious construction issues that need to be addressed, although I would expect the handles for your door openings to be unpleasant to use bare-handed after the forge has been running for a little while.

[Trevor84]

Ya it's the temp of the outside of the forge I'm surprised at. My old Evey day forge was brick so I never really touched it or thought about it getting too hot aside from feeling my fuel lines. 

I keep thinking that there must be steam inside by the way it heats so evenly I'm just not sure if that's possible. 

No the paint isn't even burning at the bottom where it meets the floor. 

Thank you, I expect I'll be adding wood or something to the handles or keep a glove handy. 

[Dasher]

I'm a relative newbie, so my advice has no real merit re experience, but the guy who advised me on my forge build was adamant that cracks, fissures etc on insulation joints were real heat sinks/ escape routes, advising me to stagger and overlap joints in a step keyed method, to counter escaping heat. My 1st thought on seeing your forge was the parallel joint at the floor making an easy escape route for heat to leave the furnace and be soaked up by the shell. I hope I've not poked my nose in and misled you, but that is what I think.

[Trevor84]

Ya it's either where the forge meets the floor or steam or both. I'm thinking of adding a bit more material to the floor and let's say key the upper into the soft bricks a bit more or kinda dish the floor so there is more of an overlap. 

I probably have to run it for a bit and see just how hot it gets. And no you're not sticking your nose in that's what I wanted, I'm trying to get ideas. 

[Frosty]

Trevor: Do NOT change things yet, you haven't given it time to dry out and indeed ANY residual moisture in the liner will turn to steam. Rather than dig the channel for the top half to seat in any deeper check with a stove shop for some "stove rope." It comes in cords hence the name rope but also comes in belt. It's designed to seal stove and furnace doors and works a treat in a forge.

You have the psi gauge in a bad place. Where it is it's AFTER the jet so there will be a fractional pressure drop to it. Put it where you need it, on the regulator so you can watch while you adjust pressure. Yes? Most regulators have a plug where the gauge goes, if not just put a T on the outlet for the gauge and gas line. This position will give you the most accurate pressure measurement as the entire supply circuit will act as a plenum equalizing pressure. 

I know intuition says if being on the far side of the jet makes for a pressure drop and inaccurate readings then being right next to the regulator outlet must lead to a higher reading. That makes sense but doesn't hold or manufacturers wouldn't put the gauge fitting ON regulators.

About psi readings, do NOT make the mistake of trying to judge performance by the readings, they only have meaning for YOUR forge, what other people run only  means something on THEIR forges. The best use for a gauge is to make it easy to repeat forge temperatures without having to wait for it to get hot and adjusting. For example a person might do basic forging at high orange heat and THIS psi reading is 6psi. The psi reading for welding might be say 9psi. You write these down in your notebook and double check until you know them by heart. So, here's where it helps. You weld up a couple billets in the morning but are going to do some decorative forging the rest of the day. Rather than waiting for it to cool enough to eyeball the adjustment you just turn it down to 6psi when you get back from a coffee or tea break and go to work. 

Make sense? Repeatability is where gauges really shine, we're not doing high precision stuff here.

Frosty The Lucky.

[Trevor84]

Hey thanks Frosty fire place rope makes perfect sense. I'll see what type I can find around here. 

I hear you on the gauges I really do I basically use it like you say, for refrence. Like the odometer on my old chev. The sound and vibration tell me when to shift but I do make mental notes on what rpm I happen to be at different speeds. (2100 is about 100kmh) I think I see what you mean, stating the psi in pics isn't really necessary due to each build being different. I just often read references to it.

I do have a gauge on my regulator the one on the burner was an extra I had and thought it may be handy there. In all honesty though I'm planning on taking the one off the burner, without gas pressure it still reads 5psi so it's faulty and it just looks clumsy up there. I'm just going to cap that nipple off. 

How do my flames look? This set up is a 0.030 7"mixing tube. With this set up I assume I would do most of my around 5psib

[Buzzkill]

My current forge is "D" shaped as well.  Where the upper portion of the forge meets the floor on both sides I used some strips of scrap fiber blanket (delaminated to half thickness) and sprayed with rigidizer.  The weight of the upper shell compresses it nicely so there's little to no direct flame exposure for the blanket, and the rigidizer kind of glues the blanket to the upper and lower surfaces.  Fire place rope should work well too though.

[Mikey98118]

You need to cut the metal shell back away from the openings. Leave at least an inch of of ceramic showing beyond the shell, to keep it from overheating from hot exhaust gasses.

[Frosty]

That's another thing, the heat from the forge or what convection carries up the burner when you shut it off ages gauges quickly. The convection heating of the burner is commonly called the "Chimney effect."

Your flames look pretty good, does steel scale in the forge?

Ditto Mike, the exposed steel shell around the doorways will warp when it gets hot. I KEEP making the same mistake and I know better but it's a hard habit to beat. 

Frosty The Lucky.

[Trevor84]

Mikey, I was worried about the steel lips being over heated, I will try the gasket of sorts (wool or rope) and see how it reacts if that's doesn't cool it down I'll trim out some steel and get some wool exposed. I should have asked more questions earlier 

I'm fixing my choke so I can close it right off at shut down to hopefully reduce the chimney effect. 

I've removed the gauge and capped the pipe, what you say about the gauge makes sense. 

Ill shine up some steel later and see what happens. If it's rich I'll see scale build while in the forge..... I believe that's the typical test/reaction. 

Thanks guys

[Buzzkill]

14 minutes ago, Trevor84 said:

If it's rich I'll see scale build while in the forge

If it's neutral or fuel rich and there is no direct flame impingement you should not see scale form while the piece is in the forge.  If it is oxidizing (fuel lean or air rich) you will see scale form on the piece while it is still in the forge.

[MCalvert]

I just want to say well done on your forge. I know you are working a couple bugs out and all, but this thing looks fantastic to me. When you get it dialed in just how you want it, I bet it ends up being a pleasure to use! Bravo.

[Trevor84]

Thanks Buzzkill, that's what I thought. I tested a piece of steel in there and it scaled up so I'm a little lean. 

Thanks MCalvert, ya a couple design flaws but that's par for the course for all my projects. 

I ran it for a half hour or so, the burners running lean and the outer body is still heating quite a bit. I can't feel heat coming out the gap where the upper meets the floor and no burnt paint yet. I did note steam escaping from a couple holes in the welded seems on the body plates (not sure how much that would affect the heat of the outer shell). My weekends over and I will try some wool as a gasket next weekend but if that doesn't help too much maybe I'll trim out these sections where the Xs are that will leave me tabs at the ends and one in the middle to help support the insulation and again use a gasket. 

Thanks for the pointers thus far. 

[Mikey98118]

1 hour ago, Trevor84 said:

I did note steam escaping from a couple holes in the welded seems on the body plates (not sure how much that would affect the heat of the outer shell).

It probably won't natter much. The thing about steam is that it tends to shoot out under high pressure; not so much for flame when the steam is done

[Trevor84]

Ya my welds aren't the best, I've got no worries that I made a boiler if that's what you mean I just keep hoping that the steam is causing extra heat. But if that's not the case and the gasket doesn't work then I'll be trimming the steel. I would trim a big strip off the bottom lips but the thought of the insulation dropping out when I move it worries me. 

[Mikey98118]

If you rigidized the blanket, it isn't going anywhere; If you didn't rigidize, it's cheap and easy to do...

[Trevor84]

I did not rigidize the first (outer) layer of wool or stick it to the body. I did rigidize the second (inner) layer though. 

How stiff would 400ml of rigidizer make one layer of wool? Say if I left a 1" tab at each end of the bottom lip should that hold itself possibley? 

[Trevor84]

I guess that's a silly question because each forge will be different. Sorry typed before I thought. 

[Frosty]

Mike and I make our own rigidizer by mixing fumed silica in water and spritzing it on wetted blanket. I don't recognize the brand you're using but I'm not familiar with commercial rigidizers at all. Anyway, I don't think he can answer your question in a meaningful way, I know I can't.

Frosty The Lucky.

[Trevor84]

Ya I figured that question would be about the same as "will this 3/4" burner work for my forge" without knowing whether the forge is 300 or 800ci. 

I used 400 mililiters of colloidal silica rigidizer from a pottery store. (what ratio they mix it at is unknown) The inside layer of insulation would be 10x20". 

I'll play around with this more in a couple days, see what the gasket does then trim metal off the bottom if needed. Thankfully I only have 4day weeks

 

Thanks for you patience with these silly questions guys. I thought I was on track with this build until I got to here and ran into this heating issue and now I'm kinda panicking. I know exaust heats things up but this seems excessive, anyway I just need to BREATHE and work through these steps ONE piece at a time. 

[Mikey98118]

18 hours ago, Trevor84 said:

I did not rigidize the first (outer) layer of wool or stick it to the body. I did rigidize the second (inner) layer though. 

Unless you added a seal coating, nothing stops you from rigidizing that layer now.

BTW, there is nothing at all wong with your burner; it was a good build

[Trevor84]

Thank you I do appreciate your approval of the burner I definitely pulled it out of Burners 101.  The unrigidized wool is sandwiched to the steel body so I'm kinda stuck with it for now.......oops  I shoulda spent more time in Forges 101 I guess

[Mikey98118]

The inner layer of rigidized wool will not stop a generous amount of rigidizer from passing through it to affect the outer layer; it just takes more than it otherwise would

And yes, you do have the approval of lots of us on this forum for your burner. I just thought it was overdue to be mentioned

[Frosty]

8 hours ago, Trevor84 said:

Thanks for you patience with these silly questions guys.

Nothing silly about them Trevor, you're still figuring this stuff out.  

The shell of my forge is too hot to touch for more than a second and it's about average. I think you're focusing on a problem that isn't, the outside of any furnace that reaches in excess of 2,000f internal temperatures and only has 2" of insulation WILL be hot on the outside.  It's not a thing.

It's also no THING if you didn't get the outer layer of kaowool rigidized, it's sealed into the forge so particles can't escape. If you see a spot rigidize it. 

You're doing better than most folk building their first propane forge who didn't follow a proven plan. You're good, relax, maybe just light that beauty up and beat some HOT steel.

Frosty The Lucky.