O/A Torch Question

[BrentD]

A couple of years ago I bought one of those Harbor Freight Oxy/Acetylene kits that has the two bottles in a little red plastic carrier. Wasn't planning on using it very much so I didn't want to spend a fortune on a professional rig.

I've used the rig maybe twice since I've had it and it seemed to work OK for what I was doing. Until today. I needed to do a quick braze on a part that I had to modify so I got out the torch and opened the acetylene valve 1/4 turn and set the regulator to about 10psi. I opened the Oxygen valve and set the oxygen to about 20 psi. Tried to light the torch and it was a no go and I couldn't smell any acetylene. I thought maybe I had forgotten something and had the valves reversed so I opened the other valve and got the same result.

Then I looked down at the gauges and noticed my Acetylene gauge was now up around 20PSI. I quickly shut off both bottles and bled the lines, then turned both regulators fully off and started over. I opened the acetylene bottle 1/4 turn again and this time set the regulator to only about 5 PSI. Then I opened up the Oxygen bottle and started to slowly turn up the regulator. I had already double checked to make sure both torch handle valves were fully closed. Once the Oxygen passed 5 PSI I noticed that both the Oxygen and Acetylene gauges started increasing as I increased the oxygen pressure. At that point I decided that maybe I wasn't understanding something so I decided to come ask the experts what's going on with my torch.

Am I correct in assuming that the oxygen and acetylene aren't supposed to mix until they pass the valves in the torch handle and enter the mixing chamber in the tip? Is it possible that there is a crack somewhere inside my torch handle that is allowing the oxygen to feed back into the acetylene line?

I'm also guessing at this point I should maybe disconnect the lines from the regulators and bleed them out in case the acetylene line has an Acetylene/O2 mixture in it that might be unstable.

 

[wushaw]

Turn both of the valves at the base of the torch off and see if the regulator still increases.

 

[BrentD]

Turn both of the valves at the base of the torch off and see if the regulator still increases.

This torch only has 2 valves on it, and they are right below the couple where the torch tip attaches to the body. With both of those valves off turning the oxygen up increases the reading on the Acetylene gauge.

Another interesting thing... When the O2 pressure is say 20 psi and the Acetylene pressure is 10 or less, opening the valve on the torch marked "Fuel" releases oxygen instead of acetylene, and no I don't have the hoses on the wrong ports because opening the oxygen valve also releases oxygen.

 

[Scotty370]

I'm wondering if over the years, you Ace bottle went 'flat'. When you first tryed it, your Ox tank pressurized the Ace bottle with Ox! I can't imagine how it would back feed it to do that! Do you have double gauges so that you can read tank pressure and feed pressure? Did you 'crack' the Ace bottle and smell Ace?

 

[BrentD]

I'm wondering if over the years, you Ace bottle went 'flat'. When you first tryed it, your Ox tank pressurized the Ace bottle with Ox! I can't imagine how it would back feed it to do that! Do you have double gauges so that you can read tank pressure and feed pressure? Did you 'crack' the Ace bottle and smell Ace?

Yep. Separate gauges on both regs. The Acetylene bottle is only about 2 years old and it's still showing plenty of pressure in the bottle.

I'm betting that the two valves in the handle are machined from one piece of brass. If there was a flaw in the brass that separates the valves and that flaw turned into a crack, that would allow the gasses to mix inside the torch body.

 

[Cap-n-Cray]

Sounds like the Acetylene regulator is bad. The same thing happened to me the other day. I had not used my Smith torch for some time. I turned on the Oxygen tank and adjusted the pressure, but the pressure kept increasing. It finally started blowing the safety release so I closed the tank valve fast. Rebuilt the regulator and all is well. The seals went bad over time.

Cary

 

[BrentD]

Sounds like the Acetylene regulator is bad. The same thing happened to me the other day. I had not used my Smith torch for some time. I turned on the Oxygen tank and adjusted the pressure, but the pressure kept increasing. It finally started blowing the safety release so I closed the tank valve fast. Rebuilt the regulator and all is well. The seals went bad over time.

Cary

But in my case, if I turn the acetylene bottle main valve off and just leave the regulator set where it was then turn on the oxygen the acetylene pressure immediately starts going up.

Did another test and the opposite is true. Turning the oxygen bottle valve off and leaving the regulator set, bleeding the Oxygen line then turning on the Acetylene and turning the pressure up gives a rise on the Oxygen pressure gauge as well.

Bottom line is that the Oxygen and Acetylene are somehow mixing inside the torch body between the hose connections and the control valves.

 

[Cap-n-Cray]

That doesn't sound good. Does the torch body have two valves on it? My torch you open the Acetylene first, light it and then add Oxygen. The gas are mix but only in the torch body and tip. Could your tip be blocked? Can you blow though it?

Cary

 

[BrentD]

That doesn't sound good. Does the torch body have two valves on it? My torch you open the Acetylene first, light it and then add Oxygen. The gas are mix but only in the torch body and tip. Could your tip be blocked? Can you blow though it?

Cary

Tip is definitely not blocked and yes there are two valves. What started was when I tried lighting it and it wouldn't light, so I checked for that distinct Acetone/Acetylene smell at the tip and realized it was blowing oxygen. Thought the hoses were maybe reversed so I opened up the Oxygen valve and still got oxygen. That's when I checked the regulators and discovered that the pressures start cross-feeding when both torch valves are closed.

 

[Cap-n-Cray]

Is it this kit?

Can you try disconnecting one of the hose (Oxygen) at the torch body. Open the Acetylene to see if the acetylene come back though the torch body. Can you stop it by putting you finger over the disconnected side? Does it come out the tip? Is there something blocking the torch body at the tip? The gas is mixed in the tip if I remember correctly. There are two "O" rings on the tip.

Cary

 

[Lazy]

Acetylene bottle is only about 2 years old and it's still showing plenty of pressure in the bottle.


Hi
Pressure means nothing, the only way to tell if you have acetylene is to weigh the bottle and subtract the tare weight. leave the oxy off and if you can't light the torch then chances are you are out of gas and the pressure you see is just acetone.

Charlie

 

[Gary Fowler]

Your problem it that the oxygen is bleeding back through the torch head connection where it screws on to the mixing barrel (that is the part with the 2 valves where the hoses attach. You either have the cutting head nut not tightened where the two connect or you have one or both orings bad on the cutting head. You should have 2 orings on the cutting head, a small one and a larger one. The small one has to seal the high pressure oxygen or it will bleed back into your mixing barrel and back into your acetylene tank if you dont have any check valves installed. This is potentially very dangerous situation. But it is easy to correct, just tighten the cutting head and if it still is increasing the pressure on the Acetylene gauge take it apart and check the o-rings and replace as necessary.

 

[djradz]

Your problem it that the oxygen is bleeding back through the torch head connection where it screws on to the mixing barrel (that is the part with the 2 valves where the hoses attach. You either have the cutting head nut not tightened where the two connect or you have one or both orings bad on the cutting head. You should have 2 orings on the cutting head, a small one and a larger one. The small one has to seal the high pressure oxygen or it will bleed back into your mixing barrel and back into your acetylene tank if you dont have any check valves installed. This is potentially very dangerous situation. But it is easy to correct, just tighten the cutting head and if it still is increasing the pressure on the Acetylene gauge take it apart and check the o-rings and replace as necessary.

Not that I disagree, but it seems something more is wrong. I've not read yet where he has gottern any acetylene to flow no matter what he has done.

Maybe trying just acetylene with the oxygen tank valve shut off for starters?

 

[BrentD]

Ok, tried this.... Removed the tip. Double checked that BOTH control valves on the handle were closed. Disconnected the oxygen hose from the handle and turned on the Acetylene. Sure enough acetylene came out the Oxygen connector on the handle. Cobbled together a fitting from some tubing and an air compressor pressure gauge and stuck it on the connector where the oxygen would connect. Pressure of acetylene coming out the oxygen fitting is roughly the same as what I set at the acetylene regulator.

Verified that at no time was any gas coming out of the end of the torch body where the tip would connect.

Then I reversed the setup, hooked the oxygen back up and disconnected the acetylene hose. Turned on the oxygen and oxygen came out the acetylene hose connector. Again, nothing came out the holes where the tip would connect.

Reconnected both hoses and turned on Acetylene only and was able to light the torch, but oxygen regulator pressure rose to match acetylene pressure. Oxygen control valve on the torch was fully closed.

Turned Oxygen on at the regulator but left oxygen control valve on torch tip fully closed. Flame behaved as if the oxygen control valve as fully opened and oxygen was only being adjusted at the regulator. I kept increasing oxygen flow at the regulator until the flame went out. Once I passed the pressure of the acetylene, the acetylene pressure gauge started to rise with the oxygen and there wasn't any hint of acetylene at all coming out of the tip.

Cap-n-Cray: Yes, that is the kit. I'm not using the cutting tip, just the brazing tip.

 

[Baby Grand]

Just my opinion ...

1)As Gary Fowler observed, remove & inspect the O-Rings for cracks, nips, tears, etc.
2)Regardless of the O-Rings condition, replace with fresh ones.
3)If you still see communication between the two sides, then pitch the torch and buy a good quality replacement.

Consider it cheap life insurance.

Jim

 

[BrentD]

I really don't think it's O-Rings as it's still cross-feeding with the tip removed and the control valves off. There's got to be a crack somewhere in the torch body either at or before the control valves.

At this point I think I'm going to toss the torch and go pick up one at the local welding supplier. I don't mind Harbor Freights disposable tools when the worst that can happen is a motor burns out, a bearing wears out too fast or a wrench cams out, but in this case where the flaw is causing the mixing of flammable gases and creating a situation that could prove extremely dangerous, I'm not going to trust my life to it. Further I feel like I should do something more than just toss the torch. This flaw is pretty serious and needs to be reported to somebody.

 

[Cap-n-Cray]

A torch body is not that complicated. It is just two adjusting valves that flow gasses to the tip. Has the torch body been damaged? If the torch body is crossing gasses then as Jim said pitch it or return it. Something is missing?

Be sure not to mix Oxygen with any oil. That is not good and can explode.

Cary

 

[Lazy]

 

[DanD78]

When you buy the new torch head get one with check valves built in or buy check valves to protect your self. They go in line on each hose.

Dan