Any HVACR Pros Here - Question about Oxy/Acetylene Setup

[Dennis Peacock]

I have a son who recently graduated from an HVACR Trade School. He's now working with a local HVAC company getting his "feet wet" in the trade. I'm trying to learn about Oxy/Acetylene setups that he needs for his trade. I don't want to kill the bank, but I don't want short-lived stuff either. I know what it means to have good tools that can get you going until you can buy top of the line stuff later.

I'm looking for advice on what he needs to get his setup for doing HVACR work for brazing/soldering/welding. I've looked but there seems to be so many choices with prices to go along with them...so I come to the place on the web that I feel most comfortable in asking and getting advice.....here on SMC.

TYIA

[Bruce Wrenn]

Look over at Ebay for torches made by Uniweld, Harris, Smith, Victor, or Prestolite. Don't over look the small Oxy/ Ace from Harbor Freight. Their price on gas bottles is hard to beat. Visit one of the welding web sites for more info. I doubt he will be doing much welding as tubing is copper. His boss should furnish the torch. Will he need a nitrogen rig for purging lines before soldiering, actually silver soldiering?

[Tom M King]

Compare online prices with those of your closest Welding Supply/Gas store. Ours has prices as good as Amazon, and they have all the torch parts, and tips, in stock.

[Stan Coryell]

Hi Dennis,
For most silver brazing we use a "Turbo Torch ". It's not the same as a regular acetylene torch. I've never done any gas welding related to refrigeration. Gas welding and oxygen- acetylene welding are different from brazing. A turbo torch is good up to at least 1 1/8 copper. As mentioned above, a torch is usually company supplied. For a oxy- acetylene torch setup, Victor makes a decent small set using a "MC" tank and a very small oxygen tank.

Does anyone know where the "MC" and "B" designation came from?

Stan

[Bill Dufour]

I believe MC is a small tank intended for a motorcycle headlight or maybe a motorcar. I have heard b size is a larger size for a bus?
Bil lD.

[Bill Dufour]

He needs to be very aware that the acetylene cylinder has acetone in it and the acetone must not be burned off. I have heard that if the acetylene runs low you will see sparkles in the flame this is the acetone burning. If all the acetone is burned off the acetylene will explode if the pressure is more then 30psi? Beyond 29.4 psi, it becomes self explosive. No other chemicals are needed. No air, no oxygen no nothing just pure acetylene and pressure. This is why acetylene tanks have fusible plugs in the bottom. To blow out before the pressure becomes too high.
I guess a jet of burning acetylene is considered better then a exploding tank of it.
Never set an acetlyne tank on it's side or upside down.

[Bill Dufour]

I do not think it applies to regulators and hoses but the tanks have to be tested and stamped every few years. A set of expired tanks may be more expensive then renting ones that the gas company will hydrotest as needed.
Bill D.
5 years for O2, 10 years for acetylene. May be different in your state or province.

[Stan Coryell]

Bill, you are correct. MC for motor car and B for bus. I read that in Wood Magazine? A few years ago.

As for the acetone, the only way to draw it from the cylinder is to exceed the maximum withdrawal rate or to use the cylinder in a position other than up right. The maximum withdrawal rate is 1/7 of cylinder capacity in cubic feet. If a cylinder is stored on it's side, it NEVER should be, it must be stored upright for as long as it was laying down or 24 hours, whichever is shorter. If the acetone is withdrawn from the cylinder, the flame will skinny and BRIGHT white (like a sword). The fuse plugs, one on top and one on the bottom are there in case of flash back. When flash back occurs, the flame is drawn into the touch tip. It's possible that the flame could burn all the way back into the cylinder. The heat from the flame inside the cylinder would melt the plug and release pressure, preventing the cylinder from exploding. In theory anyway. When the flame draws into the torch tip it makes a wicked screaming sound. Acetylene regulators should not be able to be set above 15 psi . Any plumbing/ refrigeration/ welding supply should sell MC or B tanks. They have different fittings, I think. When the tank is empty you take it to any other supply house and they exchange it with a full one. As far as I know they are all "customer owned", but they exchange them so you don't have to worry about inspection or pressure testing.

Stan

[Mike Henderson]

I do not think it applies to regulators and hoses but the tanks have to be tested and stamped every few years. A set of expired tanks may be more expensive then renting ones that the gas company will hydrotest as needed.
Bill D.
5 years for O2, 10 years for acetylene. May be different in your state or province.

I've always exchanged my tanks. I always ask for good looking tanks just because I don't like working with grungy looking tools. Sometimes I get nice looking tanks, sometimes not.

Mike

[John K Jordan]

I've always exchanged my tanks. I always ask for good looking tanks just because I don't like working with grungy looking tools. Sometimes I get nice looking tanks, sometimes not.

Mike

I also exchange tanks. With customer-owned tanks they will refill instead of exchange if you want which will let you keep a new pretty tank, but that often takes a day or two and a second trip to pick it up so I just exchange for one on the dock which is immediate, don't care what it looks like. I buy the largest tanks that can be purchased and don't have to be rented, Q, and keep oxygen, argon, argon+co2, nitrogen, and helium. The supplier doesn't care if I bring in a nitrogen tank and want something else in exchange.

Our gas supplier exchanges for the cost of the gas and the supplied tank is always within inspection date.

JKJ

[Tom M King]

A couple of Oxygen tanks ago, I got one that had U.S. Navy stamped in it. I didn't ask any questions, but do get some with obvious, strange histories. I never asked what they do with the little HVAC portable tanks, since I don't really have a use for them. I just back up to the loading dock, and they swap the tanks.

[Stan Coryell]

I don't normally pay any attention to the stamps on gas cylinders, but I remember seeing a couple with swastikas back when I started in 2000. In theory a cylinder never goes bad. I'm pretty sure HP cylinders have to get pressure tested every 10 years. This is regulated by the DOT.
When I go over setting up a oxy- acetylene torch with apprentices, I point the inspection stamps out to them. It is common to see stamps back to the 50's. I also show them a valve, or "skeleton" key. The old acetylene cylinders required a valve key. They were pretty much gone by 2005. Does anybody still see them?
Most of the "B" tanks have valve handles now. I haven't seen a "MC" cylinder in a very long time, so I'm not sure about them. Does anybody know if they have the same valve as a "B" tank?
At some point high pressure cylinder valves had to be "back seated" or they would leak around the stem. I have no idea when they switched to a packing type stem, but I've never run across one that didn't have a modern valve.
My dad has a 20# propane cylinder that has threads on top of the valve to accept a "lantern" that holds a lead pot. That valve has to be back seated. I'll try to find a date on it.

[Bruce Wrenn]

Back in the seventies we regularly got oxygen tanks that had dates in the previous century. Something to think about is how these tanks are made.

[Scott T Smith]

Hi Dennis,

For over 40 years I've owned oxy-acetylene, oxy-propane, and a plethora of different gas bottles for the TIG and MIG machines, and have done HVAC work in the past.

What is common in the industry for HVAC is a oxy-acetylene setup called a "Port-a-torch", such as this one from Harris.

https://www.harrisweldingsupplies.co...utfit-4400177/

Acetylene is preferred over MAP because it gets hotter, quicker.

Other manufacturers have their versions of this same thing. It uses an MC sized acetylene tank and a 20CF o2 tank. The #1 and #3 brazing/welding tips that are included with it are all that he will need for HVAC work. This size is the best balance between portability and capacity. Get a good pair of gloves and safety glasses of the appropriate shade to go with it.

Typically local HVAC suppliers such as Johnstone Supply will sell these, or you can buy them from a local welding supplier (LWS). The small bottles are considered to be "owner bottles" and your LWS will usually swap your empties for full ones. You should not have to worry about tanks being in certification times for these small bottles that you swap. HVAC suppliers will have the correct silver brazing alloy rods. Here are two that I use:

Silver brazing 2.jpg

He will need some flux to go with them, and also some tube brushes and sandpaper for cleaning the copper. A small container of acetone for cleaning the joints after brushing/sanding. He will learn in class that cleanliness is extremely important for a leak free work.

One other nice thing to give him is a good set of digital guages. The old "steam guages" have been around for a long time, but I really prefer my Fieldpiece digital set. Mine is older, but their SMAN 360 would be an excellent set for him. It is a digital manifold that has the superheat calculations built in, and has a digital micron meter for measuring vacuum. This is very important when checking for leaks when pulling a vacuum on a new system. Fieldpiece digital manifolds are pretty much considered to be the Cadillac of the industry.

If you don't want to invest that much, get him a good digital vacuum guage such as this one and a good set of manifold guages. Yellow Jacket and Robinair are two respected brands in HVAC work.

https://www.amazon.com/Fieldpiece-SV...3788923&sr=8-1

https://www.amazon.com/dp/B01N1M19P4?tag=aclabnew-20

Hope this helps. Best of success to your son and kind regards,

Scott

[Bill Dufour]

Thanks Scot. I could not remember the name. the "port a torch" set up is designed for plumbers. Harbor freight even has a version. You can find a usa made one on craigs list for around $200. just make sure any older set up has check valves and flame arrestors at the torch head.
Bil lD