Oxy pressure in external mix torches

[Kevan]

If the gas and oxy are mixing outside of the torch, why would it matter (within certain limits of course) what the regulator pressure was? Since you are controlling the flow of gases with your torch?

[navarre]

One thing that comes to mind is - the higher the pressure the sharper the valve response adjustment - such that you can reach a point where it just isnt practical to control the flame.

Next you have the flow characteristics of the gasses - it can just get too turbulent at the torch face and again you cant control the flame.

[Dale M.]

One thing that comes to mind is - the higher the pressure the sharper the valve response adjustment - such that you can reach a point where it just isnt practical to control the flame.

Next you have the flow characteristics of the gasses - it can just get too turbulent at the torch face and again you cant control the flame.

Good answer!

Dale

[Cosmo]

To a certain extent, it doesn't matter as long as there is a certain minimum pressure supplied to the torch. If a torch runs fine at, say 5 psi, I highly doubt you'll see any difference at 6 or 7 psi. You probably would at 20 psi, but, like you said, you need to stay within certain limits.

[kbinkster]

Very good question, Kevan. Navarre gives a pretty good answer, but I'm going to expound upon it.

One thing that comes to mind is - the higher the pressure the sharper the valve response adjustment - such that you can reach a point where it just isnt practical to control the flame.

Next you have the flow characteristics of the gasses - it can just get too turbulent at the torch face and again you cant control the flame.

True, the valve response changes. The lower your pressure, the more you have to turn the valve to let in a given amount of fuel or oxygen. The higher the pressure, the less of a turn you have to make. How much that matters depends on what pressures you're talking about and the quality of the valves used in the torch. Some torches have much better valves than others and can be satisfactorily tuned on higher pressures without any problems, while others are hard to fine tune regardless of pressures.

Torches are not straight-through pipes like a garden hose (the garden hose theory does not apply to torches). They have restrictions within them that interrupt flow (baffles, etc.) and knock down any turbulence. How turbulent the flame is depends more on the internal structure and the valves of the torch. Every torch has its limit of where its flame will fall apart.

It is always a good idea to keep your pressures set within the range recommended by the manufacturer.

When using tanks, the pressures dictate how much volume is available. So, a higher presure setting means that more gas is available for a larger flame. The drawback may be that on some torches, the user would have to readjust the pressures again to get better control of a small flame.

Sometimes, they have to run really low pressures just to get the valves to work better for them for finicky glass. If the glass has a narrow window of workability to achieve a certain affect, they may need the valves to be more precise than what they are. To compensate for that, they lower the pressure so they have to turn the valve more to let in gas, thus getting more abilty to fine-tune the flame. If you have truly high precision valves to begin with, you don't need to lower the pressure beyond the lower limit of what the manufacturer recommends to fine tune the flame for finicky glass.

For the GTT torches, the valves are very precise (and very high quality). I can run my GTTs at high pressures and still have fine-tunability with a soft non-turbulent flame. The high pressures I'm talking about are like 50 psi oxygen and 20 psi for propane for a Lynx. I don't need that high of a pressure to run it (it maxes out at 12 psi and can run at lower pressures than that), but I have done this test to prove a point. Below is a picture of a Lynx hand torch. It shows the same small, soft, non-turbulent flame on various pressure settings. I could still get the same flame on that torch and fine tune it using 100 psi oxygen and 50 psi fuel, if I wanted to. The valves and the torch can handle it.

26117

[Kevan]

Thanks for the response. And the pictures.