Hello Bob, to answer your question simply, the 80cf tank would last twice as long. Now to answer your question somewhat more realistically. When people use oxy-fuel systems to cut steel they tend not to utilize their set-ups as well as they possibly could. You need to pay close attention to the tip size that you are using to do the cutting. By using the proper sized tip you will utilize both the fuel gas and the cutting oxygen to their fullest potential. Make sure that you are using the correct type of tip for the gases that you are using, there are different types for oxy-acet., oxy-propane, oxy-chemolene, etc. Use a cutting chart to select the proper tip size and also the correct pressures to operate the given tip. It does no good to run higher oxygen cutting pressures than those recommended for a given tip and only waste the extra oxygen. Cutting tips are very carefully designed to operate at the pressures listed by the manufacturer of a given tip, make sure you are using the information for a tip that is supplied by that specific manufacturer and not someone elses. Also pay close attention to how clean the tip is and if you clean it, use care not to damage the orifices in the tip. To determine how long roughly the tank will last, look at the cutting tip chart, it will most likely have a column that will list a specific tip size and how much oxygen it will consume in a Cubic Feet Per Hour value (CFH), divide this number into 80 or 40, the resulting number will roughly give the time in hours that you will be able to cut continuously. This number will probably seem rather low, so you need to consider that this will be based on non-stop use. Hope this helps some. Best of luck and Regards, aevald
Hi, I understand all about the right tip size for specific sizes of steel . I just didnt know if i got a 40cf oxy tank would i get enough pressure to cut 1/2 to 1 in. steel ? Also about how long would i be able to cut this ? (This would be for home use every now & then),, Or would i be wasting my time running for oxy every time i want to use it ? So instead of paying the price for a 40 cf tank to find out i need a 80cf instead ,,, Thought maybe someone in here could inform me before hand. Does anyone in here use 40cf oxy tanks ? Thanks again , Bob
Hello again Bob, unless I read your response incorrectly you were asking if the 40cf tank would have enough pressure to cut 1/2" or 1" steel. Any cylinder regardless of size will basically have enough pressure to cut the material you are inquiring about, it is how long they last that is determined by the cylinder size. New filled oxygen cylinders all have approximately 2250 to 2500psi in them, the regulator knocks that pressure down to a usable pressure that is set on the regulator. I glanced in the Smith book that I have for reference, if you were using a smith tip# SC40A-1 which is suggested for cutting 1/2" material, it would require approx. 109 CFH to operate, this means that you could operate this tip off of an 80 CFH cylinder for around 44 minutes, the 40 CFH cylinder would last approx. 22 minutes. Hope this explains better what you are trying to determine. Regards, aevald
aevald , Thanks for your help, that explains it Very well to me now. I think a 40cf tank is useless to me & a 80cf would be the smallest size i will go with. Thanks again, Bob
Hello Bob, depending on how portable you want this to be and how far you live from your gas supplier, you may want to go with an even larger tank. I know when I've done weekend projects and have run out of oxy. it's very aggravating, that's why I actually have a spare cylinder for those times. If a larger tank size isn't an inconvenience for you, you may want to price the larger ones, you may find that the price really doesn't increase that much for the larger tanks. Glad to be of help and Regards, aevald
Forum