[TheForge] hot portable atmospheric forges may need propylene

Tue May 31 21:11:42 EDT 2005

Mike,
I will be moving to a new shop location with a natural gas 
supply for heat.  I am wondering about using NG to power a 
new gas forge.  Is it a good fuel to use for forging?  It should 
be a bit safer than propane as it is lighter than air.  Where can 
I get info about burner designs (I assume blown).  Thanks 
ahead.
-Rick

---- Original message ----
>Date: Tue, 31 May 2005 18:46:27 EDT
>From: Keporter at aol.com 
>Subject: Re: [TheForge] hot portable atmospheric forges 
may need propylene  
>To: theforge at mailman.qth.net
>Cc: skipjack394 at verizon.net
>
> 
>
>
>
>
>Yes, atmospheric burners are self limiting, but no, they 
aren't  limited by 
>the amount of oxygen they can draw in (any of these 
designs can  be tuned to an 
>oxidizing flame). The limit is the amount of nitrogen--not  
oxygen--found 
>within the intake air. Nitrogen contributes nothing to  
combustion, and is 
>therefore a drag on the flame's energy density. This is  the 
sole reason that 
>oxy/fuel flames are hottest. However, the theoretical limit  
of an air/propane flame 
>is listed as 3600 degrees, so you might not want to  
dismiss them out of 
>hand. 
> 
>Liquid oxygen costs money to use. Quite a bit more money 
than the cost of  
>many fuels. If you want to take the temperature of an 
existing forge higher  
>than you can get by using the best of tube burners 
(correctly tuned), the  best 
>IR coating (water separated ITC #100), and the best 
exhaust system  (larger 
>openings with exterior baffles), then the next logical step is 
the use  of 
>propylene fuel gas, rather than oxygen enrichment. 
Propylene will cost you  about 40 
>percent more than small amounts of propane, but it is still 
only  about 60 
>percent of the cost of MAPP gas; at least in Seattle.  
Propylene was rated 
>between 25 and 50 degrees of the temperature of MAPP.  
However, Air Liquide has 
>replaced the propane content in its formula with  propylene, 
so this can no 
>longer hold true. In fact, I'll have to write them now  and find 
out what the new 
>flame temperature of MAPP is supposed to be.
> 
>I have done a study of oxygen enrichment, and it works 
great as an  
>economical means of raising natural gas flame 
temperatures.  With twenty percent 
>enrichment, you receive about a 1000 degree boost.  That's 
an excellent investment, 
>when you factor in the low cost of NG. The  reason 
enrichment works so well is 
>two fold: First, you get the biggest  temperature increase for 
oxygen 
>enrichment at the lower end of a sliding scale;  the upper 
end of that scale shows 
>only a 50 degree increase for the final  twenty percent 
oxygen invested. 
>Secondly, the fuel it's commonly used  with (natural gas) 
requires the least amount 
>of added oxygen (1.5 to  1) of any fuel but acetylene (1.1 or 
1.2 to 1 
>depending on whose  figures you use). Using it with propane, 
you would need 3.5 to 1 
>of added  oxygen. Therefore, you can multiply the needed 
percent of added 
>oxygen by the  difference between these figures; at this 
point switching to 
>propylene is  not only looking simpler, but cheaper too. 
Propylene uses the same 
>fittings and  regulators as propane. I have used it during 
burner tests, and it 
>will give the  same comparative heat increase over propane 
with top flight 
>burners or  ancient designs. On the other hand, my interest 
in propylene is for 
>hand torches  and burners being used as hand torches, 
where ambient air can help 
>cool  the SS nozzle. When you start running internal forge 
temperatures up to 
>the  higher ranges for very long, you well most certainly 
melt the SS nozzles 
>right  off your burners, so you want to use a good grade of 
ceramic to build  
>a burner port, with the nozzle shape incorporated,  instead. 
> 
>I have not bothered with recuperative schemes, because 
the temperature  boost 
>simply isn't worth the added building expense and lack of 
design  
>flexibility, for ordinary forge work. Since, these higher 
temperatures are  needed for 
>some projects, one of you might give them a second look.  
There is the Sandia 
>forge with plans already existing, but I think an all  ceramic 
version would be 
>the best design. It would probably also work best  with the 
ceramic nozzles 
>everyone will need to operate at the desired  temperatures. 
However, it will 
>either need a tall stack or fan to suck hot air  down into the 
furnace, and 
>neither scheme sounds very compatible with the word  
portable. In the meantime 
>propylene out on a demonstration site is a very  minor cost 
compared to say a 
>hot-work permit, or even just your  time and travel 
expenses :-)
>Mike P. 
> 
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>___________
Rick Korinek
Emerald City Forge
46 Joseph Road
Framingham, MA  01701
508.320.7425