Natural gas burners, any suggestions?

[Gilli]

Just recently built my first forge a Coke forge in fact, and now after a few months of tinkering I've concluded I want to venture into the realm of gas forging. As far as a body goes, I'll recycle an old propane tank with ceramic wool for insulation with a refractory cement coating on the inside. Now I just need to contemplate a burner, any suggestions

[timgunn1962]

For Natural Gas, you are unlikely to have the pressure available to use a Naturally Aspirated burner to any of the usual designs. There are commercial burners out there that should work, but they will be expensive and considerably bigger than high-pressure Propane burners of similar output.

That pretty much restricts you to a blown burner.

[WayneCoeArtistBlacksmith]

With my Ribbon Burner I am running 1/2# of Propane pressure and forge welding Damascus billets, with no flux.  Natural gas burns a little different than Propane but you could build a Ribbon Burner using the instructions on the Forge Supplies page at www.WayneCoeArtistBlacksmith.com.  You also might want to view the attachment (Build a Gas Forge) for building a forge using a 20# Propane Bottle.  If the Ribbon Burner doesn't work well with the natural gas you can always just use Propane with it.  Just remember that Propane is lighter than air and will flow down while natural gas is lighter than air and will flow up to the ceiling .

Let me know if I can help you,

Wayne

[timgunn1962]

It's worth checking your NG supply pressure at an early stage, as it may impact your choice of blower. It varies by location, but here in England domestic gas is supplied at 8" WC, about 0.3 PSI.

There is not much point having a blower that gives more pressure than the gas supply because the gas will stop flowing altogether when the mixing chamber pressure reaches the supply pressure. 

 

[Mikey98118]

Well, no; the process of using high fuel pressure in a gas jet to induct air can just as easily be reversed, using compressed or fan-blown air to help draw low pressure natural gas into a burner. Nevertheless, you'll have to spend quite a lot of money to have a certified plumber lay gas pipe into the garage, in order to save a little money on piped gas over the price of compresed LPG.

[Frosty]

Well, seeing as we're talking a ribbon burner we're talking a gun or blown burner. NG is supplied at pressures too low to operate a naturally aspirated burner outside the kitchen range. To supply enough NG per second to develop the BTUs/hr to forge with you'll have to use a much larger jet orifice at such low pressure.

Don't worry the blower won't over come the NG if you introduce it at the blower intake. Let it flow into the blower with the intake air.

Frosty The Lucky.

[Latticino]

4 hours ago, Frosty said:

Don't worry the blower won't over come the NG if you introduce it at the blower intake. Let it flow into the blower with the intake air.

I would certainly not recommend introducing the natural gas at the blower intake unless you get a blower that is specifically designed for use with an explosive mixture (certified spark proof). 

9 hours ago, timgunn1962 said:

It's worth checking your NG supply pressure at an early stage, as it may impact your choice of blower. It varies by location, but here in England domestic gas is supplied at 8" WC, about 0.3 PSI.

There is not much point having a blower that gives more pressure than the gas supply because the gas will stop flowing altogether when the mixing chamber pressure reaches the supply pressure. 

 

 Most blowers the general public will use for burner construction won't get anywhere near development of 8" of static pressure at their outlets in any case.  Not that this really matters, as unless there is a significant restriction in the piping downstream of the mixing chamber (say an obstructed ribbon burner, or one that does not have sufficient free area to allow the volume of gas/air mixture required to pass relatively easily through the burner) the pressure at the mixing chamber will be much closer to atmospheric than that inside the gas supply line, and that pressure differential will allow flow.  Please recall that blowers, fans, and compressors are rated for a range of total static pressures (inlet to outlet) depending on their fluid flow rate (research fan curves).  If your burner assembly is correctly designed with limited restrictions downstream of the mixing chamber, the external static pressure from that section that the fan experiences will be low, and the assembly will ride the fan curve down to the intersection with a shallow parabolic system curve to a point of relatively high airflow and low developed static pressure.  In fact to modulate  this airflow you will likely want to install a butterfly valve upstream of the mixing chamber to add some resistance to the airflow and enable making the desired air/gas mixture.

I have constructed several successful residential natural gas/forced air burner assemblies and have never had a problem with the air pressure in the mixing chamber overcoming the gas flow.  However, note that for typical sized forges you will require a much larger gas line size and outlet orifice than the equivalent propane system.  I used industrial burner components that I was lucky enough to get from a glass studio that was getting renovated, but there are several sources of good plans for such burner assemblies available.

[Frosty]

Blower intakes are under negative pressure and can't blow anything into the motor. Still, I agree it's hard to be too careful working with flammable anything let alone gases. So use a brushless, motor that does NOT rely  on the blower for cooling air. No sparks and no direct air from one to the other. Prophylactic measures are good when you don't want cross contamination/contact.

Frosty The Lucky.

[mutant]

It's easy and simple!

I looked into this when I was building my foundry for casting aluminum. I'm thinking if you can melt AI , which is a little over 1200 degrees, you can probably do some forging with it.

http://www.plansandprojects.com/My%20Machines/natural_gas_burner_success.html