Propane Orifice at High Altitude

J

joedhiggins

Joined
May 31, 2016
Messages
485
Gents,

I recently moved from sea level to 6200' and built a new forge. The ceramics place nearby recommended I use some .050 orifices. I have tried running them, and the forge sounds a bit off and I get a huge amount of propane burning outside of the forge, especially at higher propane pressures. This is regardless of the adjustment of the venturi shutter.

I am assuming this means I need to use a smaller orifice at higher pressure. Anyone have any ideas on what size I should use?
Not sure if I have given enough info. If I need to provide more, let me know.

Thanks.
 
Yes, I figured I would try the Venturis first, because I wanted to keep it simple. Perhaps it was a mistake. Can't find anything in the .030 range. I guess I could silver solder the orifice and redrill. Thanks.
 
Sort of, I will have to match the existing thread, or replace some parts. Will look to see if I can find one. may be easier.
 
Most orifice tips used in building burners are MIG tips. You can pick the size and change them if needed. .030 is sort of the standard.

A blown burner is much simpler than a venturi. A blower of some sorts, a 3" gate valve ( can be PVC), a 1/4" brass needle valve, some pipe.
No orifice or jet to make.
No need to an air sleeve or fiddling with the jet position.
No problems getting the air/fuel mix right.
 
The 100K Graham burner has been tested at 7200' above sea level and operated fine. It uses a .042" orifice and functioned almost identically to 900' above sea level.
 
So I have tried it with a number of orifice hole sizes, 70, 65, 60. It seems to work the best with the size 60, but where I live it is quite windy, and the air flow around the venturi cover hole seems to be drawing a sufficient partial vacuum as to cause premature ignition (burning just beyond the orifice) unless I shield the venturi covers.

I imagine I will continue to have similar problems with varying wind speeds, and am considering using a forced air setup. The burners I am running are 3 of the Axner MR-750s (http://www.axner.com/mr-750venturiburner.aspx).

Is it worth it to try and convert the existing burners to a forced air setup? Should I just replace them with another burner? Make one myself? Haven't built a forced design yet, so I am not sure of the details.
 
Also, The interior of my forge is approximately 18"x7"x4.5". I am assuming that I need about 400k BTU for that size box to be comfortable in reaching welding temps.
 
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