Expert: Ernie Leimkuhler - 5/1/2009

Question
QUESTION: I just purchased an oxygen/acetylene set up after stick/mig welding for a number of years in order to bend certain structures.  Gas is a whole new beast.  I was looking for instructions on how to adjust the flame for a rosebud (heating) tip.  Thank you for any help you can offer!

ANSWER: Running a rosebud tip on acetylene has some real problems.
Acetylene tanks can produce a lot of gas, but not quickly, because they store their gas dissolved in acetone to stabilize it.
Extracting this gas from the acetone can't happen quickly.
This poses a problem with rosebud tips.
Rosebud (or multi-flame) tips come in a variety of sizes.
The medium to large rosebuds require a higher volume of gas than an acetylene tank can produce continuously, so they tend to backfire and "pop".
The problem is magnified if you are using a smaller acetylene tank, like those owned by most hobbyists and homeowners.
So if you are stuck with acetylene as your fuel gas you will be limited to only the smallest of rosebud tips
You can overcome this if you run several acetylene tanks in a manifold, all feeding to one regulator.
Obviously this is not a solution for a homeowner or hobbyist.

What I recommend is to run a rosebud tip on oxygen and PROPANE.
A little known fact is that you can attach an acetylene regulator onto any propane tank.
Even the small 5 gallon (20 lb.) BBQ bottles have internal threads in the valve head that accept a standard acetylene regulator.
This gives you access to a few other options as to oxy/fuel gas applications.

Because Propane is stored in a liquid form, it expands to a gas quickly, and in high volumes.
Even the largest rosebud tip can be fueled by a BBQ bottle without a problem.

Using oxygen with propane is a great combination for rosebud tips, but also works great for cutting.
When oxygen and acetylene burn the highest heat is at the tip of the inner blue cones, and this flame is just around 5800 degreesF.
Steel melts around 3100 degreesF so there is more than enough heat to melt steel.
This works well for welding, but for all other applications LP gasses, like Propane, actually work better.
When you burn oxygen with propane the highest heat is actually 3/4" to 1-1/2" from the tip.
This means you have more heat further from the tip, which works much better for cutting heavy plate steel than acetylene.
Also LP gases don't burn as hot as acetylene (between 5100 and 5500 degF) so you have less trouble with over heating the steel, leading to rounded cut edges and over melting of thin steel.
You will need propane cutting tips, since they are quite different from acetylene cutting tips.

The one thing you can't do with propane, or any LP gas, is weld.
When LP gasses burn with oxygen they infuse too much hydrogen into the flame to allow gas welding of steel, and the welds would end up quite brittle.

Back to your original question about adjusting a rosebud tip...
You need the fuel gas to be roaring, loud with no soot showing, before you add oxygen.
The flame should pull back to the tip as you add oxygen, until you have a ring of small blue cones.
Rosebuds are LOUD when adjusted correctly.

---------- FOLLOW-UP ----------

QUESTION: Thank you for the information!  I have a pretty large oxy/acetylene tank combination, but the idea of using the propane appeals to me even more.  Are there any certain precautions using LP with the rosebud?  Just turn on LP, get it flaming crazy and then apply Oxygen?

Answer
You should upgrade your hose from an "R" hose for Acetylene to a "T" hose for all gasses.
Using propane with an R hose won't dissolve the hose before your eyes, it just reduces the lifespan of the hose from about 10 years to about 5 years.

Lighting LP gasses is different than acetylene.
The flame from the fuel gas alone is much softer than an acetylene flame, so it can be hard to to keep lit in a crosswind before you add the oxygen.
You can fight this by cracking both the fuel and oxygen valves and lighting the mix.
This works best if you have the tip held against a metal surface at a 45 degree angle.
Once lit just keep increasing the oxygen and then the fuel gas until you get a flame large enough for your needs and fairly balanced.
You can play with the oxygen to fuel ratio.
Too much oxygen can create a flame that will overly oxidize the metal, but this also works well for stripping heavy paint from steel objects.

Excess fuel gas yields a sooty flame, but may be kinder to thinner pieces.

I forgot to mention gas pressures.
With acetylene you run the fuel gas around 10 psi for a rosebud, with about the same on the oxygen, but with LP gasses, never go above 5 psi on your fuel gas.
10 - 15 psi is fine for the oxygen.