What psi is best and why?

knittyditty · #1 2014-10-21, 1:21pm

Ok, I've read and read and read....
I'm getting ready to set up my first surface mix torch. From what I've read, the psi for the propane is between 3 and 8 and oxygen twice. Ok, I get that, what I want to know is where do you start and how do you know you need more or less?
Why do you need to change? Is the flame too cool and taking too long to melt, so you increase the psi on the propane or oxygen? How do you decide to change at the tank and not just the torch?
Is this going to be another one of the "learning curves" that everyone says, "you just have to play with it"? I want a good starting point, then know what to look for to decide if I need to adjust.
thanks,
Kristin

shawnette · #2 2014-10-21, 1:25pm

You should start with whatever the manufacturer recommends, and then work from there.

2xMI · #3 2014-10-21, 1:30pm

Kristin, you didn't mention what kind of torch or oxycon you're working with. Most torch manufacturers give the oxygen and propane requirements for the torch-- start there and adjust as you see fit. As you use your torch more, you'll get a feel for how to adjust it (if at all) dependent on how you work.

Mimi

losthelm · #4 2014-10-21, 5:15pm

Often its ball parked and then adjusted to the job.
Flame charicteristics vary a bit depending on the type of glass.

De Anza Art Glass Club · #5 2014-10-21, 5:56pm

As Shawnette suggested, start with the manufacturer's recommendations. If you don't know what these are, let us know what burner you are using.

If you are not satisfied with the performance, and you are using flashback arrestors, try a step change increase in propane pressure by 5 psi. The reason for that is because, for Western Enterprises flashback / firecheck combination, the rated pressure drop is 5 psi. If you are using an oxygen concentrator, there is nothing else, but if you are using tanked oxygen and a flashback arrestor, also increase the oxygen pressure by 5 psi.

I'm not sure what books you are reading or videos you are watching, but to start with, in your reference materials or the manufacturer's instructions there should be a candle length given for a neutral flame (maybe 3/8" to 1/2"). If you can get that with either the manufacturer's recommended pressures or recommended pressures plus 5 psi, then you can play around with finding the "sweet spot" of the flame by working further away or closer to the face of the burner.

This is just to give you an idea of what followup questions you might want to ask after thinking about these answers or after you get some experience with your particular setup.

knittyditty · #6 2014-10-23, 5:40am

Thank you very much for all the answers.....Much appreciated!

It is a Spartan and I'll be working with tanked oxygen. I do have flashback arresters...all from Devardi.

Just gotta find the time to set up, play, and practice, practice, practice...which I hate. I just want to know how to do it and just do it

Kristin