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Propane flame

Old 11-03-19, 10:59 AM
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Propane flame

The pic below shows the hottest propane flame location, is this the correct distance(+-) from the lug/fillet the tip should be while brazing?

thanks , Brian

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Old 11-03-19, 04:55 PM
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It's more complex than keeping the point of the flame at its hottest distance. It is one of the controlling factors including what size tip you choose as well as the speed you are moving the flame at what angle. When I am fillet brazing with brass I like to be a lot closer and use a smaller tip than when I am brazing a lug. When I am cleaning the shorelines I turn down the flame and move in closer. It is useful to know that the hottest part of a propane flame is not right at the tip like an acetylene flame but rather out in space a bit.
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Old 11-17-19, 10:56 AM
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Here's another propane flame pic, from Paige Tools, to go with the above. I'm trying oxy/propane brazing(with oxy tank and bbq propane tank), how does one determine a reducing/neutral/oxidizing propane flame, easily determined with acet but not sure what to look for with propane.

This from: Welding Notes and Application in Cycle Frame Building Jim Cook, Nimbus Design in UK

Filler material is typically Nickel.Bronze type C5 or Silver Alloy type 1665 using a welding nozzle size of VICTOR 000 / 00TE Tip. Flame setting for Nickel bronze, very slightly oxidizing to eliminate the possibility of porosity in the braze deposit. Silver alloys should be applied with a slightly reducing flame by virtue of the rapid oxidation of silver. Actual joint temperature in fillet brazing is lower due to the process being in the solidous range of the filler material.

Does the fact this refers to C5 rather than C4 make a difference, or that this is in reference to OA? Should the propane flame be oxidizing?

thanks, Brian


Looks like the rose bud is slightly reducing but no idea on the others
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Old 11-17-19, 06:30 PM
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Doug Fattic 
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Originally Posted by calstar View Post
How does one determine a reducing/neutral/oxidizing propane flame, easily determined with acet but not sure what to look for with propane?
By the color of the flame. When the ratio of propane to oxygen is greater, the color of the flame is kind of greenish. As more oxygen is added it goes from greenish to bluish (when it is a neutral flame) to purplish (when it is an oxidizing flame). A propane flame is not nearly as precise as the cones of an acetylene flame which allow you to clearly see the divisions. After awhile you get an instinct for setting the flame correctly.
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Old 11-17-19, 08:41 PM
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Thanks Doug!
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Old 11-18-19, 01:25 PM
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thanks for asking the question, I had no idea
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Old 11-20-19, 11:01 AM
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Here is something I copied and pasted from somewhere to a section in my frame building class manual and I'm copying it here now. It tells the temperature in fahrenheit of the 3 different fuels usually used in bicycle frame brazing and also the ratio of fuel to oxygen. I didn't make a footnote of where I got this information. Looking at it fresh now I had forgotten how much more oxygen is used with propane than acetylene. I primarily use an oxygen generator so it doesn't matter to me what the ratio is as long as my concentrator can keep up. This is why those disposable oxygen canisters (with CGA600 fittings) wouldn't work well for making a frame because a person would use too many of them before they got done. There probably is enough propane or map gas in one of those canisters to make one frame. I experimented a couple of years ago with a 2 bottle (oxygen and map gas) Bernzomatic unit. The tip was actually about the right size for what we do but the oxygen bottle lasted just a bit more than 15minutes. A $10 each it would not be an economical solution.

NOTE: There will be a noticeable performance and temperature difference when using propylene (MAP//Pro) versus acetylene and an increase in oxygen consumption. Acetylene burns at 5589 deg F with an oxy/fuel ratio of 1-1 respectively. MAP//Pro burns at 5193 deg F with an oxy/fuel ratio of 3.5 - 1. Propane burns at 4579 deg F with an oxy/fuel ratio of 4 - 1.
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Old 11-27-19, 11:05 AM
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Originally Posted by Doug Fattic View Post
...... Propane burns at 4579 deg F with an oxy/fuel ratio of 4 - 1.
Given this ratio is needed to reach that temp how does this relate to oxy/pro pressure? From searches I've done most recommended regulator pressures for brazing are roughly 5 psi propane/5 psi oxy( 1 - 1) when using an oxy cylinder(not an oxy generator) and # 2-3 torch tip(Victor), how does the 4 - 1 ratio fit in to these recommendations? Also wasn't sure if the Victor TEN tips had the same orifice size as acet tips, found this:



thanks, Brian
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Old 11-27-19, 03:18 PM
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The Victor TEN tips have the same diameter orifice as other Victor tips with the same identifying #. The only difference is that the end is recessed a bit to help keep the flame attached to the tip. The depth of the recess is about the same as the orifice diameter. The illustration you provided shows that the orifices are all the same size but the doted line on the end of the TEN tip shows the recess diameter. I usually go up 2 Victor sizes when doing propane as compared to acetylene to get the same amount of BTUs. In other words a cooler frame but more volume gives the same heat output.

The Victor UN-J mixer elbow designed specially for propane has more and bigger oxygen supply holes than an acetylene mixer elbow. This is to up the ratio of oxygen to the flame. This means that the pressure in the line can be the same. In fact it is a problem to increase the oxygen pressure because it is more likely to blow out a propane flame.
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