Gas forge cement popped off - Heellppp

Jonas Liebel

Jonas Liebel

Joined
Jan 20, 2018
Messages
34
Hi there,

I wanted to use my propane tank gas forge for the first time and started to slowly heat it up, but apparently I didn't let the cement dry long enough, resulting in a loud "bang", a huge flame and a hole in my cement walling.

First of all, do you think the big flame that shot out of both ends of the forge was caused by the cement coming off or the other way round?

Second, how do I fix the holes? Should I just put some new cement into them and hope that everything bonds together nicely?

I'm a little bit lost, so any help would be greatly appreciated :(

Jonas

PHOTO_20180206_144725.jpg PHOTO_20180206_144720.jpg
 
I don't know the correct english term, it's a furnace cement that is meant to withstand up to 2900F
 
Ok, just checking. I would clean the damaged area up and just mix a small batch and patch the area. That's what I do with my satanite costed forge.
 
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Probably trapped moisture which became super-heated steam and blew, propelling the flame out. Probably want to let is dry a bit longer post repair (like 1-2 weeks) and do some low temperature runs before going to forging temperatures.
 
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But, to repair, just spackle some more in there to cover. It will bond fine.
 
There are some refractory cements that are better than other for this, specially designed to "patch", and are more consistently grained, and stick better to vertical surfaces. That spot should be able to fill with anything, so if you've got more of the same refractory on hand, use it, if you have problems on the roof of the forge later though, check with your local supplier for a recommendation.

I use APG Greenpatch in my forges when shit falls or gets knocked off. I can't ever get the usual stuff like Mizzou to stick in a repair.
 
Several more pictures/details of your forge would be helpful in diagnosis. I know some recommend a thick 1/4" coating of mortar, but I prefer a thinner coat that can be more easily repaired. Additionally, a thinnner coating is less prone to the type of popping you experienced. If your goal is to simply prevent fibers from breaking off and going into your lungs, it doesn't take 1/4" of satanite to accomplish that. If you're goal is to build a hard shell forge, use bricks.

PS The burner appears to be too far into the forge chamber. At least 1/4" back of the chamber interior is recommended.
 
I think you need to slowly cure your forge lining. Allow it to dry, then fire it SLOWLY. Use a heat gun or heat up chunks of steel and place them inside. heat it gradually.

And get a refractory coating like Plistix or ITC ... it makes a HUGE difference.
 
The thicker the coating, the longer it needs to dry before curing.

Patch it up and let dry a week or two. Moisten the bad area first, then apply the refractory.
Start with a warm only heating. Light the burner and run it on low for 30 seconds and shut it down. wait 10 minutes and repeat , running it 60 seconds. Repeat with 30 second increases every 10 minute rest until it is up to a 3 minute run at low flame. Let rest an hour and then fire on high for 15-20 minutes. At that point the lining should be fully cured and hard. If there are small cracks, patch them and give a few low temp cycles, then fire on high to fully dry.
 
What your looking at is spalling. It can happen from heating one area quickly while the area around it heats much slower. The refractory expands in the hot area much faster then the surrounding area. This builds pressure that cause it to flake off and blow out like you see. I’m a boiler operator at a large lumber mill and this can be a big problem in our cells. We keep our 3 cells running 24-7 and turn one off at a time to clean every 24hr. But we do this while it’s still VERY hot (glowing). This is one reasion in the industry it’s better that once it’s hot you keep it hot. Nothing shortens the life of your refractory more then heating and cooling over and over.
 
Thanks for your help guys! I didn't know I should put the burner flare further out, that's good to know. :)
 
MBB said:
Probably trapped moisture which became super-heated steam and blew, propelling the flame out. Probably want to let is dry a bit longer post repair (like 1-2 weeks) and do some low temperature runs before going to forging temperatures.
Click to expand...
Yep.
Just light it and let it run for about one minute. Shut it off until it stops steaming.
Repeat.
Repeat.
When I reline my forge and it has freshly applied Satanite I light it right up. Soaking wet.
 
I will suggest once more that you look into a high emissivity ceramic coating like ITC-100, Plistix IR or Metrikote. It will give your refractory longer life and increase the heat in forge by reflecting IR back into the cavity. This will save you fuel, too. I was shocked at the difference that thin layer of white made.... SHOCKED!
 
I agree, ITC-100 seems expensive, but a small can does a whole forge, and it will increase efficiency a lot.

Some tips on lining a forge. Build the chamber lining up slowly. 1/4" is the max per coat, 1/8" is even better. When a coat has dried a day, wet the inside and put on the next coat. The last coat should be thinner and be worked out smooth. Ridges and bumps create turbulence. After the lining has dried well for a week or two, fire it SLOWLY. Once fired and cured at full heat for 10-15 minutes, let cool overnight and then apply a coating of ITC-100. Mix it like very thin pancake batter ( crepe batter for those who cook). Paint it on with a brush, repeating until a good coat is on. It does not need to be more than 1/16-1/8" thick. Let dry well and fire again as before. From here on the lining should last for years with no issues.
 
Thanks guys for all your comments.
I have never heared of ceramic coatings like ITC 100, propably because we can't get any here in Germany ^^ Or does anyone know an european alternative to it by chance?
 
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