Dear Allan, Tim, Welderbent and everybody here,
Thank you so much for the sincere concern and detailed description as usual 
Well, as I told you before, Egypt is a big producer of natural gas. I think the industry here should just make use of this advantage not available for everyone. We noticed, me and the professor I am working with, that still most of the workshops or related industries rely on the acetylene as the fuel gas in the oxyfuel cutting processes. So, what I am trying to do some is to conduct limited series of experiments to cut different thicknesses of low carbon steel (A36) with the natural gas and try to publish this out for alls' benefit here. The thicknesses are 3mm, 6mm, 10mm and 12mm. do you think these thicknesses are enough?
I think in doing so, we are saving a lot of money here.
I almost have all the equipment and the operator ready. The welder himself is worried and afraid to try the natural gas. He wants me to use these mixtures used at our houses in ovens (mixture of propane and butane). He said he tried this before and it is safe. He thinks that cutting with natural gas is not safe!! I think it can't be more dangerous than acetylene. The only concern would be when the gas is in direct contact with air. Right?
So if I have set the working pressures, the proportions of oxygen to natural gas, the preheat time, and made sure of hoses being in good condition, then that is it.
Anyway, I am preparing the procedures from the materials you sent me and others as well.
If you do not mind, I am sending you this procedure to take a final look at it before going ahead in the experiments.
P.S
I am enjoying this Allan more than you could imagine :)
Thanks everyone
Yours truly,
Mona
Safety is only as good as the person following the "rules". I can't think of any reason why methane would be any greater hazard than acetylene. Methane might be stored in a much higher pressured container, but acetylene in its free state is unstable after 15 psi. Oxy-acetelyne has a much hotter flame than any of the other gases. From my thinking, acetelyne requires more precautions (note, I did not say more dangerous!). As for the mixed gas issue, that I would think is purely economical..costs /cu. ft. and container handling vs. perhaps supplied via pipeline into the shop. Anything can be unsafe, and a hazardous material if handled improperly air, water, a sack of flour etc. I've worked with explosives in the past (wiring detonation cord to RDX shaped charges...) in the oilfield perforating formations. Kind of scary in concept, just follow the rules...DON'T deviate! Once again...Safety is only as good as the person following the "rules".
"The only concern would be when the gas is in direct contact with air. Right?" This holds true to any flammable gas. What about unlit and exposed to pure oxygen?
After about 16mm you might want to consider preheating a little (dry run as we used to call it, follow the cut line using the pre-heat only), but, after 20mm, it is advantageous to preheat using acetylene.
Wish you success in your experiment.
John
John hit the items I was considering. The thicknesses are you propose are easily cut with natural gas as the fuel. We used it for years in a pipe forming shop I worked for. They had it piped in as it appears you are doing and had it piped to each major work station where we attached our equipment and went to work. We used it to 3/4" (18mm) with no problems. As John stated, at about 1/2" it pays to run over your cut area to pre-heat. Improves the quality of the cut enough to make it worth the time. I often would warm my heavier section from the bottom side with a hand held torch as well. It is the side opposite where the torch will be running that doesn't get as much heat even when you pre-heat.
Safety is a consideration in all stages of welding and with all fuel gases. No more so really than with propane, propylene, acetylene, or MAPP.
If you have a good chart so you can get the right tip from your supplier for the thickness being cut, monitor travel speed, proper gas pressure maintained, everything should go very well. Good Luck.
Have a Great Day, Brent
Yes,
"Weed burners" are an efficient tool to pre-heat pieces a square meter or over in size.
Now that you mention it, we used to use those to pre-heat the sides of tanks in cold weather ahead of the submerged arc girth welders for CBI. I generally use either a regular torch head or a rosebud in similar fashion to what you had mentioned but from the bottom of the plate instead of the top.
Have a Great Day, Brent
welderbrent,
Yes excellent advice, pre-heat from the bottom and "dry run" from the top. On dirty or excessively scaly steel, two dry runs, 1st pre-heat only to loosen the scale, then another run over with the cutting jet on to blow away the scale, can make for quality cuts.
Absolutely. And if burning freehand, do rough layout, run torch over to 'pop' mill scale, rust, etc off, then do accurate lay out for cutting. Takes time, but you'll get a better finished product. Could have a helper wire wheel whole thing first, but then a lot more gets cleaned than what may need to be. Or, just buy new, clean steel in the first place. Should be so lucky.
Have a Great Day, Brent
By Superflux
Date 11-21-2008 01:36
Edited 11-21-2008 02:12
Cup stone on grinder
Wire wheels don't usually stand a chance against millscale. That's some bad to the bone stuff. "Or, just buy new, clean steel in the first place. Should be so lucky." What planet and quadrant of the galaxy do you weld in??? Got any more openings??? Have hood ..will hyperspace there tommorow or yetesrday if (super)flux capicitor is at full charge!!!
With regard to safety, the hoses should be grade "T" I believe this is neoprene. The grade "R" and "RM" hoses commonly used with acetylene are not compatible with other fuel gasses, and will detriate prematurely.
Well, i did not know this hoses issue. So, do u really think the normal ones used with the acetylene are not used with the natural gas? Ok then i'll have to look for the "T" type you mentioned.
Thank you guys so much and you are really making things easier for me to prepare. only some points left to sum the whole thing up for the experiment. I am still working on the precedure i am going to follow. Looking forward to sending it next Sunday
Thanks again and regards to all of you.
Mona
Dave is exactly right.
I had forgotten all about that.
Good point Dave!
Tim
There is 'safety' in a multitude of counsellors. That had appearently not crossed several of our minds till now. Most all the gases outside of Acetylene require a different hose for a totally proper set up. Thank you Dave for reminding us.
Have a Great Day, Brent