[TheForge] Re: TheForge Digest, Vol 57, Issue 18

[James Binnion]

On Oct 21, 2008, at 7:44 PM, Andrew Vida wrote:

>
>
> Cindy and James wrote:
>> Would a natural gas forge require added air, i.e. to be blown, to  
>> compare, heat-wise, with a propane?
>
>    I doubt that normal aspiration would produce the necessary  
> pressure drop required for proper venturi function.

There is absolutely no inherent reason that the venturi principle will  
not work at 7-11 in WC. Virtually every gas appliance uses venturi  
mixers to operate. In a forge it will work just fine but you need to  
have a precisely made venturi as you don't have any leeway for bad  
design at that low a delivery pressure. I have a commercial forge/ 
furnace made by Charles A Hones Co that runs on standard NG pressure  
of 11 inches WC. It gets to 2200 F in about 1/2 hour with a load of  
about 15 lbs of steel in it.  It cannot deal with the wide open doors  
that are typical on most blacksmith forges but it is much more  
conservative in its fuel use, its burner is rated at 1200 BTU. Hones  
Co. cast their own venturi mixers and they produce burners that range  
from 1100 to over 150,000 BTU's. Their big disadvantage is they cost a  
lot more than taking a piece of pipe and a mig tip  and cobbling  
together a mixer for a burner.



James Binnion
jbin at well.com