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Old 03-23-2013, 03:07 PM   #1
tlmartin84
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Default Oxy/Acetylene Torch problems.......possible backflash???

Here is the setup, Purox ty 202 torch with older Victor gauges.

I just had everything rebuilt this summer, probabally don't have more than 4-5 hours of use on them. Haven't even burned through a tank of gas yet.

I was trying to cut some 1/2" plate today for some brackets. I started out with a #3 tip at 5psi Ace. and 40 psi Oxy. I spent several minutes heating and trying to cut and could never get a through cut.

I thought the tip may be to small so I checked my chart and Purox says to use a #4 tip at 5/40 psi. Well I didn't have one so I switched to my number 5 tip with the same pressure.

It looked to be promising, metal heated up quick started to make my cut and the it happened......

I heard a pop/crack and backed the tip away from the plate, the torch sounded like a pack of firecrackers going off......then the handle and plunger lost all feeling and opened up completely leaving the torch whistling. This all happened in a split second and I shut everything off.

The handle was limp and the plunger was not returning. When I removed it the spring and the ball valve on the end of the plunger were completely melted.....

Can any of you tell me what the heck happened??? Or what I did wrong???
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Old 03-23-2013, 04:40 PM   #2
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

From your description, I'd say you dodged a bullet. Backflash was about T-minus 2 seconds after you closed the acetylene bottle.

Obviously, your cutting torch needs a rebuild. I wonder if the root of your issue was a faulty acetylene working pressure gauge. Anytime I've had a close call it was due to insufficient acetylene pressure.
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Old 03-23-2013, 04:55 PM   #3
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

You had the tip too close to the workpiece. It back flashed. You lucked out big time dude. Get your torch rebuilt, and get yourself some arrestors to install on your setup.

http://www.iigas.com/fba.htm
These are just an example. There are quite a few available.
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Old 03-23-2013, 08:11 PM   #4
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

I have arrestors on it at the torch handle, hmm, I hope I can find just the plunger assembly. Everything else is brand new.
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Old 03-23-2013, 08:17 PM   #5
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

you also might not have tightened the #5 tip very good..which can aslo cause flashback
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Old 03-23-2013, 08:56 PM   #6
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

ever seen or heard a bottle blow ? you will never forget it..
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Old 03-23-2013, 09:21 PM   #7
tlmartin84
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

I just checked the torch top to bottom. The only sut in it was at the valve on the handle and the plunger chamber.

The insides of the lower valves and arrestors looked like they did the day I put them on.



I hope I never hear one blow......... I have a pretty good feeling if one of mine blew I'd onl hear it for a split second.
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Old 03-23-2013, 09:22 PM   #8
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

That's why you should keep the same pressure in both Oxy and Acetylene lines, so a plugged tip can't backfeed the higher pressure gas into the wrong line and BANG!
Do the tips use O-rings? If so, replace them often. If not, you may have to lap the tips into the torch body to restore the seal.
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Old 03-23-2013, 09:29 PM   #9
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

Quote:
Originally Posted by R Pope View Post
That's why you should keep the same pressure in both Oxy and Acetylene lines, so a plugged tip can't backfeed the higher pressure gas into the wrong line and BANG!
Careful there partner. Some serious miscommunication in your statement. To cut 1/2" plate you need 30 to 40 psi of oxy. At 15 psi acetylene becomes unstable and may spontaneously combust without a spark..... at 28 psi (and room temp) it will, without a doubt combust with catastrophic results.
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Old 03-23-2013, 09:35 PM   #10
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

Quote:
Originally Posted by tinmann View Post
Careful there partner. Some serious miscommunication in your statement. To cut 1/2" plate you need 30 to 40 psi of oxy. At 15 psi acetylene becomes unstable and may spontaneously combust without a spark..... at 28 psi (and room temp) it will, without a doubt combust with catastrophic results.

Thats what I was taught, NEVER go over 15 psi on Acetylene.... What combo would you guys have ran to cut 1/2" plate....


My Purox 5 tip is comparable to a Victor Smith and Harris 2.
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Old 03-23-2013, 09:53 PM   #11
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

Seems I remember you would open the acetylene on the tourch most of the way and adjust the flame with the regulator untill the black smoke stops and the flame is not jumping away from the tip and then adjust the ox till the blue feather come down to the short blue flame when you hold down the lever.
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Old 03-24-2013, 03:55 PM   #12
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

Anyone else???
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Old 03-24-2013, 04:30 PM   #13
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

Acetylene is very volatile and should be treat with the upmost respect...on no account take risks with dodgy gear.If your torch is not working correctly either bin it or get it professionally repaired and checked.I remember seeing the remains of a garage on the national news a few years ago after an acetylene explosion.....nothing left but a massive crater.
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Old 03-24-2013, 04:47 PM   #14
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

i ve been cutting steel since 1980 i always use 39 oxy and 9 actetyline at the gauge ,,,, open the gas and spark it,,, close the gas till the little sootballs go away,,, then open the oxy till you get sharp blue points,,,, this i have cut 1/8 to 1/2 with no problems,,, AND YOU DEFINATLY NEED ARRESTERS AT THE GAUGES !!!
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Old 03-24-2013, 05:16 PM   #15
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

YouTube cutting torch watch there is a lot of them on there that may give you your answer
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Old 03-24-2013, 05:41 PM   #16
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

i would set mine at 5 and 20 with a #0 tip, i have a Harris, i also have a Victor machine torch i run on a pantograph and i'd run the same setup for that.
heres a Harris tip size and pressure quide
http://www.harrisproductsgroup.com/e...del-1-GPN.aspx

Quote:
Originally Posted by tlmartin84 View Post
Thats what I was taught, NEVER go over 15 psi on Acetylene.... What combo would you guys have ran to cut 1/2" plate....


My Purox 5 tip is comparable to a Victor Smith and Harris 2.
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Old 03-24-2013, 05:52 PM   #17
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

I would have to see you cut to know what was wrong. A while back there was a poster who described using the oxygen valve on the handle next to the gas valve to adjust the pre-heat flame instead of the one on the cutting attachment. The oxygen valve on the handle has to be wide open and the one on the cutting attachment used to control the pre heat flame or there won't be any additional oxygen pressure available when you squeeze the cutting handle and the flame can back up into the torch. Holding the tip too close or at the wrong angle can also cause flashback. Rusty metal often causes flashbacks as the rust pops.
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Old 03-24-2013, 06:18 PM   #18
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

We use Harris cutting torches with propane and normally have a #3 tip in it to cut anything from 1/4 to 3 inch but we usually use plasma to cut up to 1/2 inch steel for a cleaner cut. If I wanted a nice clean cut on 1/2 inch using a torch, I would use a #1 tip because it is the smallest we keep in stock. If I used acetylene it would be at 6 psi with oxygen about 35 psi and keeping the tip at about 15 degrees from vertical.
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Old 03-24-2013, 10:03 PM   #19
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

I have been using cutting torches for 35 plus years and I never use more than 20 pounds on the oxygen for cutting 1/2" plate and it works perfect. Use more and I figure you are wasting it. 5 pounds on the acetylene. # 1 tip should work fine for half inch. You shouldn't need anything bigger.
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Old 03-30-2013, 10:54 AM   #20
tlmartin84
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Default Re: Oxy/Acetylene Torch problems.......possible backflash???

THANK ALL OF YOU FOR THE REPLIES!!! I got it fixed.....

I talked to the guys at regulatorandtorchrepair, http://www.regulatortorchrepair.com/...s/purox-cw-275 and got the parts I needed, put it back together. I also ordered 3 new tips, ESAB/Purox 1/4" #3, 1/2" #4, 1-1/2" #5. The char I was using was from airgas that says Purox uses a #5 for 1-1/2" so I used the old tip I had labelled as a No. 5 Purox.

Well here is the old tip (right) vs the new #5 (left).


After talking to them and listening to the advice above, I think I wasn't enough gas for that size tip and it backflashed. It also shows my inexperience, I guess guys doing this all the time would look at that tip and realize it was not what I needed.......Lessoned Learned.

I am glad I had the arrestors on the handle, I also put a new set at my regulators. With the nice new tip I busted this piece in half in a matter of minutes.



I was amazed at how fast, easy, and clean the cuts were (with some practice they will be really nice). Even on the smaller stuff I have been cutting the cuts were rough, what a difference the new tips made.

Again THANKS A TON!
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