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Hot Air Welding Plastics???

sig-mansig-man Member Posts: 591 ✭✭✭✭
edited September 2002 in General Discussion
Has anyone done any of this? I have been mig and tig welding for 20 yrs. and today I began welding PVC with a hot air welder, is their any secrets or tips, Any input would greatly be appriciated, thanks...
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Comments

  • RembrandtRembrandt Member Posts: 4,486 ✭✭
    edited November -1
    Have done a bunch of this on automotive parts....technique is just like oxy-acytelene or tig welding. Only tricky part is identifying the type of plastic and getting the appropriate rod for that type of plastic, ABS, PVC, polystyrene, etc. If you don't have the correct rod for the family of plastics you are welding, cut scrap strips from extra pieces of the same material. Make sure you "v" out butt welds, use a backer for reinforcing structual joints etc.
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  • twinstwins Member Posts: 647 ✭✭✭✭
    edited November -1
    Never heard of it, does this mean I can throw out my PVC cleaner and cement? Just kidding. On a serious note, when Poly Vinyl Chloride, PVC burns, it produces toxic fumes, at least when coated around cables it does, is this a different chmical composition that you are welding or does it not smoke, emit fumes, etc.... when welded? And yes I have welded so I know you don't "burn" what you are welding.

    Thanks
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  • BlueTicBlueTic Member Posts: 4,072
    edited November -1
    We do oil tank bottom replacements in the refinery. Part of our job is to install the secondary liner - which is an 1/8" plastic barrier under the steel floor and 12"of sand. We weld this together with plastic extrusion guns. The best tips I can give - if any - is to tack your material with a hot air gun. and make sure you buff the area that you will weld - we use polyfan wheels on 4" angle grinders and go over each seam before welding. You have to have a somewhat even temp. of around 498 - 505 F on the material that your weld in. Now if you are talking PIPE, they do have a pressure welding device - that basically smuuushes the 2 pipe ends together, but they also are heated to around 500 F. and buffed.
    What application are you doing????

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  • sig-mansig-man Member Posts: 591 ✭✭✭✭
    edited November -1
    I am welding 3/4 to 1/2 PVC fillet welds,this is for a chlorine generator for a water treatment plant in Texas, I am having to use multi-pass with 3/16 pvc rod, it is hard to keep the rod from getting to hot, I am using about 2 1/2- 3 psi of air flow, and holding the tip aprox,3/4-1 inch away using a circular faning motion, any other suggestions you can think of? thanks everyone for all the input so far,and by the way they're no fumes unless you get the material to hot, actually if you are used to tig welding plastics can be deceiving, since you can't really see the penetration like in metal, thanks again guys...
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  • BlueTicBlueTic Member Posts: 4,072
    edited November -1
    Man - you got me beat - we use 1/4" rod in the extrusion guns (spool) and the tip is a flat ceramic piece, that kinda just glides along the surface. Just a thought - try throwing the rod in a freezer and keeping it froze until use. Just a another structural welder's hair-brain idea - at least you'll get a laugh outta the other guys at work.....

    IF YOU DON'T LIKE MY RIGHTS - GET OUT OF MY COUNTRY (this includes politicians)
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