Natural Gas Forge Designs -

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cca1618

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Mar 1, 2013
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I run the College of the Arts wood/metal shops for UL Lafayette. Due to an ongoing issue of smoke from our coal forges getting pulled into the building, I am currently planning on building three natural gas forges to replace them.

Years ago we were planning on a large exterior addition, part of that was to build a natural gas forge - specs based on a Johnson #133. I had two burners built to match the size/btu's - don't remember the rooms gas pressure other than I was told it was higher than "normal".
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The space was previously a boiler test lab for engineering - they had the capability/pressure to run multiple boilers at once. Once the final funding for the new space fell through, the new forge was on indefinite hold.

Now instead of one large forge I'd like to build smaller ones with a single burner. Other than Johnson's open top, pivoting lid design - has anyone built an enclosed, open on each end style? Hoping to get some examples of forges before I get too deep in the wrong direction.

My plan is to weld up a steel stand, stack brick in various configurations until I get a good design. Ceramics faculty helping with rough ideas, working with Physical Plant on running a new gas line, electrical and modifications to the existing vents.
 
The first thing to do is to find out exactly what pressure your gas supply provides.

If you have a high-pressure feed (PSI), much of the "normal" Propane stuff will be applicable. If you only have a low-pressure feed (Inches Water Column), things get slightly more difficult.
 
I would think a blown forge burner would work almost exactly like it does with propane, considering the low pressures and lack of gas velocity required.
 
Yes, NG forges take very little pressure. If you have an industrial line ( as it sounds) you have far more pressure than needed.
A blown forge blower can run full blast on residential regulator which is around 1/2PSI ( 14" of WC).
The difference between a NG forge and a blown forge burner running on propane is in the line size. A propane forge usually has a regulator with a 1/4" outlet, 1/4" hose/line, connected to a 1/4" valve and a 1/4" pipe as the inlet ( orifice). A NG burner has a 1/2", 3/4" , or 1" pipe incoming line, regulator, and fittings. It delivers far more volume of NG at a lower pressure. Industrial incoming pipes are often as large as 2".

The difference is around five times the volume for a residential regulator to over fifteen times the volume for an industrial line.

If connecting a forge to the incoming NG line, it is best to do it right after the meter by adding a Tee and a separate regulator before the regulator to the house. This will give you a regulator you can set higher than the house pressure.
 
But, I doubt your line is higher pressure "than normal." It's likely just larger like Stacy said. We use NG to fuel our CNC torches at work and must run it through a compressor to get it to the pressures required for the torches to work properly. Our NG line is the same pressure as the one at your house. It's just much larger.
 
The gas line coming into the meter we'll be using is 2.5" OD, not sure the ID - waiting to meet with Physical Plant to double check the pressure and then plan out best way to run new lines to where forges will be located. Talked to them a bit about how they preferred to get from 2.5" pipe down to the 3/4" inlet on the burner? Still waiting on a definitive answer. Are there any examples of NG forges other than the Johnson Furnace types? Looking for design ideas. Thanks.
 
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There is some reduction in pressure through a residential meter. There is also a loss from it going through smaller pipes coming to the house. An industrial meter has larger ports, and the supply pipes are much larger ... resulting in less reduction. I don't remember what the ratings were when I ran the restaurants, but IIRC, it was higher than residential supply.
 
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