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Ross Jones

Putting a Blower on a Venturi Burner

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I've recently learned from fellow bladesmiths on this forum that forced air burners are more economical than their venturi counterpart. After tearing my hair out about thinking that I'd have to buy new burners, I also learned that you can possibly put a blower onto a venturi via the large orifice on the T-pipe that the burner sucks air through. Does anyone know which blower is best, how to attach it, and if this is really possible? If it helps to have the info, I'm using two side arm burners from Zoeller Forge. Would I need a blower for each burner, or is one for the front burner enough? I heard of a smith using a big shop vac motor as a blower, but I also know that a small hair dryer works for a coal forge. Any thoughts on that? I know this is kind of scattered, so thanks for the help in advance.

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This is a complicated issue that you are oversimplifying. Forced air burners are not inherently more economical than ventauri burners, though they are arguably easier to tune and configure for various forge geometries. Actually they cost more to make (particularly if you include the recommended safety systems) and all things being equal, use slightly more energy for the fans. For a given supply pressure of fuel gas you can get more heat out of a blown burner than a naturally aspirated one, but that typically isn't a factor with a propane forge where you have more gas pressure than you can use (you do have a propane regulator, don't you?). In your shoes I would not attempt to modify the Zoeller burners if they are already working for you. If you want a more efficient system I would investigate coating the interior of your forge with an IR reflective coating and improving your forge door system.

 

Just want to add that this is assuming that your ventauri style propane burner is designed in such a way so that all the air required for full combustion of the propane is added prior to entry of the forge. If you are wasting propane without properly combining it with air, or have a flame configuration that is not being used to heat the forge interior, a blown system may be superior. It appears that ribbon style burners work extremely well to spread the flame out over a larger surface area and heat the forge interior quickly and quietly. Ribbon heads can be used with either type of burner, but a very high quality NA burner with a expanding taper mixing chamber is usually used. It is easier to use a ribbon head on a forced air burner.

Edited by Dan Hertzson

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Have a look at this thread about blown burners. A 60-100 cfm bathroom vent fan will work, if you can find something like this, I use these and they work fine (that is a lot more than I paid, but that was a one time thing).

 

Geoff

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I am interested to hear where you got the information that blown burners are more efficient (economical) then naturally aspirated burners? I would like to hear some figures.

 

I used to use blown burners and now have completely changed my ways, to naturally aspirated......

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By more economical I meant that they get hotter at lower gas pressures. I only have one tank that I'll exchange and I want to keep down the number of times I have to make the trip to Jetmore and spend $23.

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People were telling me that they were getting to welding temps at around 7 psi while I'm getting steel to a dark orange at that pressure. They told me it was because they use forced air.

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Pressure means nothing when comparing venturi versus blown. Venturi burners use high pressure through a tiny orifice to work, blown burners use low pressure through a huge hole. A good blown burner may hit welding temps at less than 1 psi, but it's dumping a huge amount of propane through an 1/8" line. That 8 psi venturi is pushing through a 0.030" hole. The only way to compare efficiency is by weighing the tank after use. Somebody had a thread on here about just that recently.

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So would the combination of a venturi pushing gas through a small hole and a blower adding more oxygen be the most effective combination?

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Nope. Blow into a venturi and you lose the venturi effect. It's one or the other, even though many have tried.

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Thanks for the help, guys. Looks like I'll keepy setup.

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