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I patched my forge with Satinite over kaowool because of a large cracked void about a 2 weeks ago. Fired it up once for about 5 minutes to dry out the patch  4 days later.

 

Prier to this patch job the forge was working well. I had to disassemble the plumbing to do the patch and reassemble. Anyway, I was working today on a billet and everything was going well until the forge stalled (small explosion)!!!!!!!!!!!!!!!!!!!!!!!!!! I SHUT IT DOWN IMMEDIATELY. After thinking about what happened for a few minutes I adjusted the gas down and the air up a tad and let the gas in. It was working fine so I continued on until BOOM..........STALLED OUT AGAIN about 15min. later. So whats going on??????????????

 

Gayton

  

ribbon burner2.jpg

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The first thing I notice, it looks like you have a squirrel cage fan that will not develop the necessary pressure.  Check out this blower:

 

Https://www.amazon.com/Sunlar-Electric-Blacksmith-Centrifugal-Barbecues/dp/B071NQDNRK/ref=sr_1_1?crid=1UKUQNDVS7OFY&keywords=blacksmith+blower+110v&qid=1563467670&s=gateway&sprefix=blacksmith+b%2Caps%2C235&sr=8-1

 

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A "boom" means that somehow you're getting incomplete combustion,  allowing a gas pocket to build up until there's enough air to let it ignite.  Might indeed be not enough blower pressure, might be some bug has blocked a few holes in the burner block, or a wasp nest in the air pipe, a leak around the burner block letting the gas mix get under the refractory, or something like that.  If it's the last one, that is potentially dangerous.  

 

First, check the holes in the burner block. If they're all clear, step two: With the gas off, try blowing smoke through the system from the blower and see if you get odd concentrated pockets. If you get smoke coming out from within the refractory you have a problem. 

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If the gas /air volume moves too slowly in your system and the system gets hot, explosions may occur inside the ribbon burner and the associated plumbing. This can be due to creating back pressure by closing the forge with a door or blocking the exit of gasses out of the forge. It is possible the whole thing is just too slow in the burner block allowing the burning to go to the volume behind the little holes.  I had this happening in a forge ( not a ribbon burner ) which I had plumbed with 2 " pipe ...did the same thing. 

 

I would have another look at the burner block..cast one that will stay cool in use .

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Here is a pic. of the inside of the forge where I patched. I made a big lump and changed the shape of the cylinder. Could that cause a problem with gas being trapped?

forge inside.jpg

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I think Jan is on to something here.  His observation, plus your pic of the lump-o-refractory, makes me think the burner block is getting hot enough to cause ignition in the plenum.  Anything that changes the gas flow path in the forge can cause weirdness, and that lump may well be the issue since it seems to be the only major variable pre- and post- patching.  

 

If you smooth that out, and maybe plaster the burner block in flush with no gaps, that may fix it.  With the block sticking out like that, and having pockets within the main forge chamber, it's going to get a lot hotter than it would if it were seamlessly flush or even a bit recessed.  Just like if you leave the end of a venturi burner sticking in the forge, it'll burn off flush or slightly recessed, with a lot of pre-ignition on the way.  Makes sense to me, at any rate. B)

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I agree with all low back pressure causes ignition behind the ribbon burner. Mine can easily do it if I'm not careful, it has happened when I try to get down below 1300f . I wonder if you could shorten your plumbing and remove a 90* bend by turning that initial 90* (at the burner) almost 180* and switching the side the blower is on that could give you better flow. I use a blower like yours with the smaller of my 2 forges I wouldn't use on the bigger forge. 

20210815_124737.jpg

Edited by Gilbert McCann
Clarity
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OK..........Thanks all for the input.

 

I am going to remove the lump patch, move the ribbon block back a bit and fill in the gap around the burner.

 

I should say before this patch job the forge was functioning without problems. I will hold off on replacing the blower for now since it has been working ok.

 

I want to set up a safety system like seen in Gilberts system but I need hands on help with that. Right now I have little control of the temp. and 2psi is what I run the gas at

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@Gayton Arrigottithat forge above is PID with no safety and can easily hold 5 degrees or less accuracy. This one is PID and safety. On that second forge (first picture) I skipped the safety a friend told me you don't leave your forge unattended anyways. I would be happy to help with safety and or PID. 

20210815_154903.jpg

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13 hours ago, Gayton Arrigotti said:

2psi is what I run the gas at

 

With a blown burner you shouldn't even have a reading on the gauge.  Are you using a MIG tip or something as an injector?  If so, don't. Just dump gas in through 1/8" copper line with a needle valve adjustment.  Do use the regulator, of course, that's a safety thing.  Adjust the gas with the needle valve, and the air with whatever you've been using.

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The 2psi is a tank gauge reading. There is a needle valve going into a 2" pipe for gas  control and a 2" gate valve for air flow.

 

Picture shows needle valve and gate valve.

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What Alan means is that even at the tank- with a forced air system, you shouldn't or won't have a steady pressure reading on the guage...

 

My attempt at explanation-

 

the force of the air flow thru the burner pipe will or should- suck the gas into the pipe and burner as fast as it flows. This will drop your line pressure guage down to zero pressure, even though you still have a 2psi flow coming out.

 

The effect is zero line pressure with full flow.

 

My forge runs the same.

I have a shut off valve at the forge- when closed, I read pressure on my tank guage.

 

When running/ burning- it shows zero.

 

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