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Oxy/Acetylene Torch problems.......possible backflash???

Discussion in 'The Hokey Ass Message Board' started by tlmartin84, Mar 23, 2013.

  1. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

    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???
     
  2. tinmann
    Joined: Nov 11, 2005
    Posts: 1,548

    tinmann
    Member

    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.
     
  3. 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.
     
  4. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

    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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  5. wbrw32
    Joined: Oct 27, 2007
    Posts: 4,580

    wbrw32
    Member

    you also might not have tightened the #5 tip very good..which can aslo cause flashback
     
  6. black 62
    Joined: Jul 12, 2012
    Posts: 1,890

    black 62
    Member
    from arkansas

    ever seen or heard a bottle blow ? you will never forget it..
     
  7. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

    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.
     
  8. R Pope
    Joined: Jan 23, 2006
    Posts: 2,978

    R Pope
    Member

    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.
     
  9. tinmann
    Joined: Nov 11, 2005
    Posts: 1,548

    tinmann
    Member

    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.
     
  10. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV


    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.
     
  11. saltflats
    Joined: Aug 14, 2007
    Posts: 2,357

    saltflats
    Member
    from Missouri

    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.
     
  12. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

  13. reefer
    Joined: Oct 17, 2001
    Posts: 609

    reefer
    Member

    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.
     
  14. big vic
    Joined: Jan 3, 2010
    Posts: 407

    big vic
    Member
    from cary il

    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 !!!
     
  15. Olderchild
    Joined: Nov 21, 2012
    Posts: 477

    Olderchild
    Member
    from Ohio

    YouTube cutting torch watch there is a lot of them on there that may give you your answer
     
  16. budd
    Joined: Oct 31, 2006
    Posts: 3,471

    budd
    Member

    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/...Tips-and-Mixers/Hand-Cutting/Model-1-GPN.aspx

     
  17. Engine man
    Joined: Jan 30, 2011
    Posts: 1,963

    Engine man
    Member
    from Wisconsin

    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.
     
  18. Engine man
    Joined: Jan 30, 2011
    Posts: 1,963

    Engine man
    Member
    from Wisconsin

    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.
     
  19. 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.
     
  20. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

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

    I talked to the guys at regulatorandtorchrepair, http://www.regulatortorchrepair.com/store.php/categories/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).
    [​IMG]

    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.

    [​IMG]

    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!
     
  21. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

    Note the 1/2" flange above was cut with the new # 4 tip.
     
  22. Engine man
    Joined: Jan 30, 2011
    Posts: 1,963

    Engine man
    Member
    from Wisconsin

    Thanks for the update. Often we don't hear about the solutions to a problem. Back in the day, most manufacturers used the same numbering system but as many manufacturers were purchased by offshore companies, numbers were changed and things get confusing. I work in a scrapyard and most scrapyards use Harris cutting torches because the cutting tips cost about a third as much as others. We use propane for cutting because it is cheaper and most cuts are made just to make smaller pieces.
     
  23. 73RR
    Joined: Jan 29, 2007
    Posts: 5,092

    73RR
    Member

    Care to share the information on the new spark arrestors ? It could be helpful to some folks.

    .
     
  24. Deuce Daddy Don
    Joined: Apr 27, 2008
    Posts: 3,457

    Deuce Daddy Don
    ALLIANCE MEMBER

    Can't believe some of these answers!!
    First off, Always buy Victor equipt.---Gauges too.
    35 lbs. on oxy. turn tank handle open all the way, then regulate diaphram to 35 lbs.
    7-10 lbs. on acet. turn tank valve only 1/4 open for saftey, regulate diaphram to 7-10 lbs.
    When done,----Bleed both hoses---Back off both regulators so you don't rupture diaphrams when used next time.
    On torch butt, open oxy valve full turn, open acet. valve 1/2 turn, light tip, adjust oxy.on side valve drawing back to sharp points on tip, then press cutting handle all the way & draw back tip points for best sharpness, release handle & start pre heating process for cutting.
    As for the "Tanks blowing"---Thats BS---Remember,PRESSURE on inside is always trying to get OUT!---Fire on acet.tank is easy to put out either by simply blowing out wit your own lung blast or gloved hand.
    Fire on hoses----Simply turn off both tanks & back off the regulators!
    Used this process since 1951 USN to present day!!----Don
     
  25. 65standard
    Joined: Jun 14, 2011
    Posts: 691

    65standard
    ALLIANCE MEMBER
    1. COE's (Cab Over Engine)

    For 1/2" plate, I use a victor torch with a #0 tip, oxy at 40psi and ace at 12psi.
     
  26. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 338

    woodiewagon46
    Member
    from New York

    I agree with deuce daddy NEVER by off shore crap, Victor has been around forever. I might be wrong but I was told by my welding supply that the flashback arrestors get mounted at the regulators, not the torch handle.
     
  27. tinmann
    Joined: Nov 11, 2005
    Posts: 1,548

    tinmann
    Member

    Since we're talking flashback arrestors, here's a tidbit..... I teach High School Metal Shop so you can well imagine safety figures fairly highly into everything we do. When I arrived at my present job seven years ago, the flashback arrestors looked like they may have come across to the new world on a viking ship. I replaced them. A few years after, I thought to ask at my welding supply place, what is the relative lifespan of these arrestors since they do have a date on them. No one could answer my question, but one guy said, when they stop flowing gas, replace them. That makes me nervous. So far, I've replaced them every three years or so. Cheap insurance when kids are involved. And speaking of consumables, in my home shop I am still using the Victor regulators that I bought thirty years ago. At school, I probably replace regulators a couple of times per year. My instruction is very detailed and my supervision of the kids is thorough. It's a combination of overuse, minor abuse that causes the regulators to creep by 2 to 3 lbs. Again my paranoia makes me send them off for a rebuild rather than take chances.
     
    Last edited: Mar 30, 2013
  28. saltflats
    Joined: Aug 14, 2007
    Posts: 2,357

    saltflats
    Member
    from Missouri

    I would think if a flash back arester was that big of a deal thay would come with a tourch set?
     
  29. tlmartin84
    Joined: Jul 28, 2011
    Posts: 752

    tlmartin84
    Member
    from WV

    Mine at the regulators are Victor FBR1 flamebusters. The ones at the torch handle are Western Enterprises.


    I have vintage victor single stage 400 series regulators with a Purox W202 Torch I had rebuilt that belonged to my Great Grandfather.


    As far as lifespan on the arrestors, The Victor paper says change after five years of use. It also says that you can check them by doing the following.....


    Hook your hoses directly to the tank, then hook the arrestors to the lines so that the airflow/ check valve is backwards. Then submerge them in water and tune your tanks to 2-5 psi. If you see more than 2 bubbles in 10 seconds they need replaced.
     

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