oxy-propane pressures & conditions

Anyone able to help me improve further, on the basis of this
recent experience?
I've recently had a "perfect" job to refine my oxy-propane cutting
conditions. "Goldilocks" ("just right") challenge.
I was doing paper engineering during the transition from oxy-acetylene
to oxy-propane - hence had to find my own way without much mentoring,
returning to steel fabs. now using oxy-propane for cutting.
The job was recovering steel to make temporary supports about 1 metre
(3ft) long - from heavy H-column used as beam. Cutting off all the
features from its previous application as a rack for tube.
Thickness 30mm.
Nozzle 1.6mm (1/16th-inch) oxy-propane.
None of the steel being recovered had any coating or paint on (nice
for me!).
All the severing was at fillet-welds - so the "retained" / "recovered"
steel made a nice guide to drag the torch along - reducing the number
of variables I needed to control, giving me a perfect focus on the
physics of the cut :-)
The ends needed precision-cutting to present a right-angles in every
direction /
sense, for easy placement and good fit-up without gap for
I found
* 40psi (2.7Bar)
fairly powerful preheat flame, but not over-driving nozzle as makes
flame "feathery" and lose focus
* neutral flame (? - still blue, just before any more preheat
oxo. would make the flame become more pale blue)
cut with torch at right-angle (or very slight forward tilt) to surface
Severing redundant side-features of previous application:
Removing all other features was "severing", without accuracy or
neatness requirement.
I found
* 70psi / 4.8Bar
* most powerful preheat flame the nozzle would give (accepting some
loss of focus)
slightly oxidising preheat flame
* cut at up to 45deg tilt-forward into direction of cut
This gave fastest cutting speed - and not-bad cuts.
The rationale for the conditions are, respectively;
- 70psi is maximum before the kerf became wider than nozzle-bore
- oxidising preheat flame meant minor knocks of the oxo. and propane
valves didn't result in a big drop in flame temperature
- oxidising preheat flame made "sweating" before could ignite the cut,
especially when piercing, more obvious
- oxidising flame "sweating" and slightly rounding the top edge of the
plate cut doesn't matter for this "severing" application
Where needed a bigger kerf in awkward locations with corners, etc.
Almost as-above, but increasing oxo. pressure to 80psi / 5.4Bar gave a
kerf at least twice as wide - presumably due to turbulence of the
oxygen stream from over-driving the nozzle? - while still a rapid
cutting rate, still going in a straight line no side-to-side
oscillating the torch.
I'd got literally a ton of oxygen, and others use a higher pressure
than these, so that isn't a pressing issue...
I got reprimanded already that learning to use an oxy-fuel torch
was about 1 year of an apprenticeship, so in that context, my skill
level is going to be somewhat basic.
OK - anyone benefit me with their wisdom? How well am I doing?
Rich S
Reply to
Richard Smith
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