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While in school for HVAC the teacher said to always set the acetylene to 7 psig and the oxygen to 15 psig for silphos brazing copper HVAC line sets. I was reading a welding Handbook and it says to set them both at 3 psig. Who is correct?
Reply:The handbook.Pressures for O/A welding and brazing should be the same for both the oxygen and acetylene, as you're using them at the same rates (and it is a little safer if both pressures are the same). As for 3psi, that depends on the tip size, but it's a decent starting point.5 would be ok for many tips too, but 15 is WAY too high.Doesn't sound like you'll be O/A cutting, but in that situation (or if you're using a different fuel, like propane), then your oxygen pressure would be higher.
Reply:The largest tip I use is a #2. As far as the cutting I did buy a cutting head today for my torch. I have those pressures down as 10-15 for oxygen and 1-2 for acetylene. This would be for cutting 1/4 steel. The handbook Im reading has a great pressure chart in it for cutting steel.I wonder where the HVAC industry gets the high settings from? Im a member of a HVAC forum and I would say they all use ranges 5-8 for acetylene and 10-15 for oxygen. They had a long thread on the subject and setting them all at 3-5 psig never came up. Im sure if I had mentioned that they would have torn me a new one.Will setting both oxygen and acetylene at 3-5 psig also mean I will be using less gas? One last question on brazing. I was also taught in school to braze with an oxidizing flame and the Handbook says to use a carburizing flame. Again, who is correct. Thanks.
Reply:Originally Posted by BrianM07Will setting both oxygen and acetylene at 3-5 psig also mean I will be using less gas?
Reply:So I have been brazing wrong for 6 years. WOW. I wish I had found this forum 6 years ago. Maybe I will practice some correct brazing practices tommorow. Thanks for the help.
Reply:This is the internet, someone is always looking to tear someone else a new one. That doesn't make them any less ignorant.As for a #2 tip. That doesn't mean much without knowing who made the tip. They are not standardized like drill sizes. Each manufacturer has different sizing, but a #2 is HUGE for brazing if it is a Victor, so I'm guessing you maybe have a Smith? Is your torch silver colored? ESAB and Harris have totally different sizing too.No, you won't be saving gas. You'll just have a more stable flame, and an easier time adjusting the knobs.You want a neutral flame. The oxidizing and carburizing flame's are highlighted in handbooks as examples of what to avoid. Welding is much more sensitive to this than HVAC brazing, which is using copper-phosphorus-silver alloys on copper. An oxidizing flame should be avoided at all times when brazing onto steel (which is probably what your book refers to), and an ever so slightly carburizing flame is recommended to help the flux work on steel. When brazing copper, the brazing alloy has its own fluxing action (so there is no separate flux), and a carburizing flame can contaminate the surface, making wetting more difficult.In all cases, an oxidizing flame will oxidize the surface, making wetting and proper brazing alloy flow worse.Anyway, don't sweat it. Air/acetylene and air/mapp swirl torches such as the turbo-torch are more than adequate for most HVAC brazing and soldering applications, and they don't have any of these considerations.
Reply:Originally Posted by BrianM07So I have been brazing wrong for 6 years. WOW. I wish I had found this forum 6 years ago. Maybe I will practice some correct brazing practices tommorow. Thanks for the help. |
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发表于 2021-9-1 00:26:13