Forging questions

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Dec 14, 2019
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A colleague brought in a Mathewson MetalSmith forge that he has had for a few years. I've made a couple of leaves and bottle openers and it's been a lot of fun. I am wondering if the forge burner is adjusted right, though. Initially, the forge did not seem to get very hot. I pulled the burner tube back a little bit and it gets much hotter now and there is no more flame coming back out of the forge around the burner. The forge now reaches 2,050°F in around ten minutes. However, every time I use the forge, I start noticing a propane smell at some point. If I crank the gas adjustment all the way to max, this is most noticeable. There is no gauge on the gas, so I don't know what pressure it is operating at. Almost forgot, this is a venturi burner. There is an air intake adjustment, basically a piece of pipe that you can slide over the air supply holes in the burner tube. I've been running that mostly wide open. I cannot detect any leaks on the fittings, so I suspect not all the propane gets burned. There is a lot of dragon's breath when I crank up the gas. When I start smelling propane, I reduce the gas pressure and the smell goes away after a while. The forge is in a large, well ventilated shop and it does not take very long to dissipate.

I am obviously a bit concerned about the propane smell and cannot imagine that this is normal. My question is how to properly adjust the burner to eliminate the issue, or at least minimize it if it cannot be completely eliminated. Any help would be greatly appreciated.
 
If there is a threaded tip in the end of the burner I’d plug it, put maximum pressure on the system and check everything for leaks by spraying soapy water on all fittings and lines.
 
If there is a threaded tip in the end of the burner I’d plug it, put maximum pressure on the system and check everything for leaks by spraying soapy water on all fittings and lines.
The orifice is drilled into a threaded brass plug. I'll see if I can find one without a hole and pressure test it.
 
I could not find a plug. I tested with the forge running again, no bubbles. Then it occurred to me that I don't need a plug, I have a pressure gauge with the same thread. I replaced the orifice with the pressure gauge, and what do you know, I get bubbles where the gas line connects when turned up to maximum pressure. The fitting that leaks is a flare fitting. I think it was probably overtightened. I had a hard time getting it apart, and there is a pretty good depression in the female part.

Is there any way to fix this and make it seal, or do I have to buy a new hose?
 
The proper way is to replace the fitting depending how it’s attached to the hose. Flared fittings don’t take much to seal and after they’re over tightened a few time will always leak. Never use Teflon tape or pipe dope on flares!
 
The proper way is to replace the fitting depending how it’s attached to the hose. Flared fittings don’t take much to seal and after they’re over tightened a few time will always leak. Never use Teflon tape or pipe dope on flares!
I think it is probably best to replace both the hose and the elbow fitting from the burner. It is a metal braided hose with a crimped end and I don't see a way to just replace the fitting. I'll see if I can find a hose with the correct fittings sometime next week. I did find some gaskets online for this type of fitting, but I don't want to mess with it.
 
Don’t use those gaskets. They’re junk and will eventually leak. Fittings and hose are cheap. You don’t have to have a braided hose, but they’re definitely safer. Just don’t cheap out on things like this, that’s how you end up burning down ur shop. It happens more than people realize.
 
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I ordered a new braided gas hose and an elbow fitting, should both arrive tomorrow. Plumbing fittings are weird, the size they are labeled does not appear to have any relation to their actual size. I hope I got the right elbow fitting, the original measured a little over 1/2", so I went with 1/4" based on a chart I found online.

I titled this thread "Forging questions" with the intention of posting a few questions about getting this forge working right, but then only posted the question about the propane smell. My second question is about the lining of the forge. There are lots of cracks in the lining and some chunks are beginning to break off, exposing the insulation underneath. There are a couple spots near the burner tube where quarter sized holes in the lining have appeared. The floor seems to be in decent shape. I am wondering at what point this needs to be addressed and how. Can this be patched or does the whole forge need to be relined?
 
I hope the new fittings get you taken care of. Just to stress, no tape on flare fittings and snug is generally tight enough.


Without knowing what the forge is made of or lined with could present a problem. I’d try to make repairs and maybe a 1/8” to 1/4” coat of satanite over the interior of the forge. It’s pretty easy to use and not too expensive.
 
I hope the new fittings get you taken care of. Just to stress, no tape on flare fittings and snug is generally tight enough.
Thanks for the pointers. I'll put tape on the threaded connections only and will try not to over tighten the flare fitting.
Without knowing what the forge is made of or lined with could present a problem. I’d try to make repairs and maybe a 1/8” to 1/4” coat of satanite over the interior of the forge. It’s pretty easy to use and not too expensive.
It is ceramic fiber insulation that has been rigidized, sealed and coated with cement according to the website. I don't think my colleague used it much at all, maybe two or three times, and then it sat in a corner for a couple of years. I am a bit surprised that the lining is already disintegrating. How much satanite would I need? The forge is pretty small, about a 4.5" round opening by 9" long.
 
I got a 5lb bag from hightemptools to line mine which is a propane bottle and had some left over. Your dimensions seem quite a bit smaller though, you could probably do it with the 1lb. I applied mine directly to the inswool, now I’m honestly not sure how well the satanite would bond to the cement already in your forge. If you email Wayne at hightemptools he will get you set up right.
 
I got the replacement hose and elbow and they were the correct parts. Curiously, the flare fitting on the gas hose had a rubber gasket in it. I removed the gasket before assembly and pressure tested it and it does not leak.

I sent an email to the maker of the forge about fixing the lining but have not heard back.
 
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