1.5. Mains supply plugs get warm in use, and the repeated heating and cooling tends to loosen the terminal screws. What happens if the earth wire pulls out? At best, the plant stops working. At worst you’re dead through an unearthed set. Use an earth-trip protected power supply and check for screw tightness every few weeks.
General points on equipment and procedures are in pictures 1.4-1.19. Do take a very good look through these, as keeping yourself (and others) in one piece is not unimportant. See also the next section which covers safe working.
SMAW welding heat usually comes from a simple transformer (1.4). AC output models are the cheapest to make as they run straight from an AC power source, like the mains or a generator, and are easily the most common – though DC (direct current) versions are rapidly gaining ground. What’s the difference? AC welding current cycles 60 times every second in a continuous wave, from positive to negative and back again. In DC operation the current doesn’t go through zero, with the result that a DC arc tends to be more stable. But as DC sets need a rectifier to change AC into DC, they usually cost more.
In both cases single- or three-phase mains power is transformed down to about 50V. Most sets offer at least one higher output alternative, with 80V common. In simple sets, welding current is adjusted by a selector which alters the relationship of windings inside the transformer. Increasingly seen these days is the welding inverter – a clever box of tricks that uses electronics and a small transformer to deliver current. Lightweight and portable, SMAW inverters are usually DC sets which, given the necessary torch and gas adapters, can be used for TIG too.
Pain in various forms
Burns apart, arc eye is the nastiest short-term hazard in any electric welding process. It’s caused by high-energy ultraviolet radiation from the arc burning the retina, and will happen if the arc is viewed either directly or indirectly. Short doses of radiation produce a very painful ‘gritty’ feeling in the eyes after exposure, with the effects lasting a few hours. Bigger doses can end in blindness. Either way, it is not to be risked.
1.6. To be certain of UV eye protection, check welding filters for proof of compliance with ANSI standards (as of 2012 the latest version is Z87.1) before buying.
Bystanders can suffer arc eye too, from either reflected light or by looking sideways (as well as directly) at the arc. UV light will also burn exposed skin, so it’s good practice to make a dedicated welding bay. Paint the walls a dark matte color to cut reflections and curtain it from outside view. When working outside the bay, warn helpers and children about arc eye danger and keep curious livestock away.
If you have a heart monitor or pacemaker fitted, don’t weld. The strong magnetic fields around leads and equipment may cause the unit to malfunction.
A good welding filter is the only protection from UV light (1.6). ‘EW’ on a filter glass means it’s designed for electric welding. The higher the code number is, the denser the filter on a scale of 8 to 14. Use EW 10 or 11 for most work; lower numbers only protect up to currents of 100A, while the highest numbers cut too much light from farm-size welding currents. Keep arc filters scratch-free with a plastic or glass screen, wiping it often during work (1.7) – you can’t see much through fog. Be very sure there’s no gaps around the mask’s filter housing where arc light can creep in. And whatever you do, NEVER use gas welding goggles for arc work: they don’t filter UV light at all.
Which mask to use? The lolly-on-a-stick sort that usually comes with a cheap welding set doesn’t last and often isn’t big enough for full protection. A flip-down welding helmet lets the operator use both hands when welding or tacking, though these don’t suit everyone. If you’re planning a lot of work, an automatic self-darkening welding mask is a fine investment: go for one with adjustable shade density and ideally, a manual mode. Various makes are on offer from welding suppliers. See picture 2.28, page 50.
Electric-shock ‘tingles’ can come from the rod while changing an electrode. These are unpleasant and reflect the relatively high voltages present. The problem is usually worse in damp weather, when current conduction to earth is better. Wearing gloves is the answer.
This takes us to clothing (1.8). Go for leather boots on the feet, as sneakers or rubber boots offer no resistance to white-hot metal spatter. Back these with cotton trousers minus spark-catching turn-ups, then cover everything with non-synthetic overalls or a stockman’s jacket, done up at the collar to stop flying sparks and slag.
1.7. Fume can soon fog up a mask — keep it clean.
1.8. What the well-dressed welder is wearing this autumn.
1.9. Fixed or mobile extractors pull away fume, making them the ideal (if expensive) solution for a welding bench.
Leather gauntlets protect against ultraviolet light and stop hot metal disappearing up your sleeves when welding vertically or overhead. Clear goggles look after the eyes during slag chipping or grinding, while a cap hides any bald patch from showering sparks.
Electrode fume is not the best of stuff to breathe, so OSHA legislation sensibly insists on operator protection. Ideally, remove fume at source with a fixed or mobile purpose-made extractor (1.9). Where fume concentrations are relatively low, a ventilated welding mask (1.10) supplies clean air from a filter pack and simultaneously streams a cooling breeze across the face. Otherwise, a disposable respirator designed to fit under a welding helmet may be enough. Be sure to check for minimum safety specs.
1.10. A ventilation pack supplying filtered air to the welding mask is an option if fume can’t be removed at the source.
Where work is intermittent and good air movement can be achieved by opening doors or windows, fume will be moved on and extra protection may not be needed. If in doubt, the local OSHA office will advise. Whichever arrangement is used, work out of the rising fume column (1.11).
Grind away paint and plating to either side of the weld line to minimize fume problems and maximize the chance of a good job. Be sure to grind off yellow cadmium plating, for its fume can be a killer. The blue-white smoke from overheated zinc galvanizing is nasty stuff too, at best making you feel ill if breathed for long. Drinking milk may help