Discussion in 'General Electronics Chat' started by Cerkit, May 14, 2009.

  1. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
    How is it that with conventional welding of say two pieces of metal being welded using electrodes in a workshop, that the operator can be holding the metal he is welding and not be affected by the high current?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Welding is generally done with low voltage and high current. The welder holds the one electrode with gloves and the electrode is chucked in an insulated handle. He also wears a glove on the other hand.

    It takes some amount of voltage to cause electrical shock, generally more than is present between welding electrodes. As the welder is not making an electrical contact with either electrode, he is not subject to a level of voltage that can cause shock. The welding current has no bearing in this case.
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    Personally, I wear gloves when welding. I get fewer cuts and burns that way.

    Have a quick review of resistances in parallel: http://www.allaboutcircuits.com/vol_1/chpt_5/3.html

    The metal has a tiny resistance, measured in micro-ohms or milli-ohms. The human's resistance is much higher. The arc is also low resistance, whereas the loose grip of flesh on metal is a higher resistance.

    Also, the metal being welded is usually at ground potential (spot welding being an exception) - and the electrode is not actually touched by the weldor. Spot welding does not require as much heat as many other forms of welding, the metal is thin and has even lower resistance, so an even lower voltage can be used
  4. Darren Holdstock

    Active Member

    Feb 10, 2009
    Gloves are an absolute necessity, and you don't want any flesh at all exposed to the light of the electric arc as the high levels of UV given off will give a nasty sunburn. And it's that short wavelength UV that produces a lobster red burn and massively increases the risk of skin cancer, rather than the longer wavelength UV that produces vitamin D and a nice healthy tan. Long sleeves, long trousers, gloves and a full face mask with a suitable filter are minimum requirements.

    Years ago, when I didn't know any better, I borrowed a neighbour's arc welder. He couldn't find his face mask, so I bought the appropriate glass filter plate and duct taped that onto some ordinary workshop goggles. My eyes were safe, but I burned my face nastily, except for around the goggles, so I looked a bit like the photo negative of a panda for a while.

    There's not enough voltage generated by the electric welding process to be a safety hazard, not even the back-EMF, but when welding a car it's advisable to disconnect the battery to power down the cars electronic systems, as the huge currents flowing through the car chassis can either cause damage or at least make systems behave oddly.
  5. mbohuntr

    Active Member

    Apr 6, 2009
    You might want to avoid kneeling on damp ground when you strike an arc, it really SMARTS!!!:eek:
  6. Tobias

    Active Member

    May 19, 2008
    A year ago I was getting some lessons in TIG welding. We were in Memphis Tn, late summer. I was wearing gloves yet a short sleeved shirt. I rested my forearms against the stainless steel tubing I was welding. Apparently my sweat from my forearms made for a nice ground path and the next thing I remember I was hammered with electricity. It made for good entertainment, yet when I weld now I make sure no skin it touching the metal I am welding.
  7. caladina

    New Member

    May 10, 2009
    just a quickie on the subject of mig welding, as an experianced mig welder 20+ years one that still catches me out from time to time is tip explosion with flying hot bunnies after welding

    what i mean by that is when you finish the weld and lowwer the mask you are still holding the mig torch, sometimes the tip can get stuck to the shroud, when you move or twist the torch it can flick a hot spark into your face as the tip frees itself from the shroud,not a regular thing but can happen, just one to watch out for along with all the other hot bunnies running across the floor and down your overalls