Let's consider the hazards involved when MIG welding.
MIG welding is an electric welding process. This means that the machinery involved referred to as the welding plant is powered by mains electric. The machine, officially described as a rectifier, is designed to convert high mains voltage (i.e 415 volts AC or 240 volts AC to direct current where the current flows from positive to negative.) This is known as DC+ve.
1/. The potential for electric shock when welding.
The welding machine is connected to the mains supply. On a weekly basis, check the security and electrical integrity of the cables. Check the cable insulation is not showing any signs of wear, discolouration or signs of overheating and that there are no splits or cracks. Only attempt to repair any damage if you are qualified to do so. If you are not, employ the services of an electrician.
Electric welding, including MIG, operates on the basis of a series circuit. There are two leads involved, a welding lead and the welding return lead.
The welding lead connects to the positive terminal of the machine and carries the welding current from the machine (away).
The second lead, the welding return lead is clamped to the work bench or on to the work piece as close as possible to the welded joint.
Both leads have current carrying capacity and consequently are live during the welding process. The leads must be checked every day before use to ensure there is no damage to the insulation along their length and that the connection to the terminals of the machine are secure. Pay particular attention to the connection of the return lead to the clamp. There are often signs of the copper cable, fraying as it connects to the return clamp. Fraying reduces the current carrying capacity of the welding cable.
Both leads must be rated electrically the same as the maximum output of the welding machine. This means that if your machine is rated at 315 amps, the leads must be able to carry out and return 315 amps safely.(Refer to a welding cable ampacity chart if necessary). Using for example, a set of leads that are only rated at 250 amps exposes the welder to the threat of being burnt and potential electric shock. Should the leads catch fire they can melt and also cause irreparable damage to the machine.
2/. Radiation burns from welding.
Electric welding involves extremes of light and heat. The welding arc generates three types of light: ultra-violet, infra-red and white. This light effect when combined with the heat generated when welding (6500˚C) is harmful and can lead to radiation burns to the eyes, face, neck, arms and hand. In fact, any bit of skin exposed will be burnt.It looks like a dose of sun burn & could increase the chance of skin cancers in later life.
Personal protective equipment (PPE) is essential in protecting the operator from radiation burns. The most essential item is a welding helmet fitted with an appropriate welding lens. The lens is designed to filter out the harmful UV and IR rays during welding and protects the forehead, face and neck too. Lens shade levels are dependant on the welding process & strength of the welding arc light.
For welding, you require the following PPE:
Other leather PPE can include a skull cap, sleeves, cape, apron and spats. These items are normally used when welding in position (e.g vertically or overhead and are essential in preventing burning from hot metal and limiting the effects of the 'welder’s dance.')
'Welder’s dance' is the movements generated by the welder when feeling the intense burning sensation caused by hot molten metal going down the neck, sleeves or into footwear. The burns are very painful and partial thickness burns and will leave scarring.
Never look directly at the welding arc with your bare eyes, a moments neglect can lead to possibly the most uncomfortable 12 to 36 hour period of your life. We refer here to a condition known in the industry as “arc eye”.
Exposing the eye to the welding arc can lead to a burning of the eyeball and an inflammation of the cornea. The condition develops over a 3 to 4 hour period and starts with an itching of the eye.
There is no real treatment for arc eye. Eye drops with some local anaesthetic can be prescribed and applied and give some relief for a short period in every four hour period. If you can safely do so and you have no allergy, paracetamol and ibuprofen help. Some advise going to bed, closing the curtains and sleeping.
The effects of arc eye are not permanent or permanently damaging and last anywhere between 12 and 36 hours. Your eyes will be sore and tired. Your head will ache due to lack of sleep. You will be incapable of welding and should refrain from doing so for a minimum of 24 hours after the effects have worn off.
Having ensured your own safety, don’t forgot to protect other operatives from the effects of the welding arc. Erect Welding Curtains & Screens around your work area, post warning notices and tell anyone close to you that you are about to strike your arc. The words “ mind your eyes” alerts colleagues that you are starting the welding process and will be very well received.
3/. The effects of heat and burns
The temperatures involved in the process present other hazards other than burning. We’ll talk about physical burns to the hands and body. To safeguard yourself, wear fire resistant overalls and the leather protective equipment. Check the seams on your gauntlets are intact; the smallest particle of hot molten metal at a temperature in excess of 1400˚C will find its way through the smallest of holes in any seam and burn you. This is a painful exercise, simply avoided by a 10 second visual inspection of your PPE.
If you experience a burn, the first aid will still be effective regardless of the type of burn you receive. Burns can be superficial; red and sore with no swelling or blistering, swollen, blistering with removal of layers of skin or burnt through skin, fat and muscle layers to reveal bones. Regardless of the burn immerse the burnt limb or digit into cold water or pour copious amounts of cold water onto the injury until a cooling effect can be felt. Do not remove any burnt clothing from a burn site and after cooling, cover the injury with a sterile dressing. If you are in any doubt or worried about the burn seek professional medical advice.
With the high temperatures involved in welding that there is a risk of dehydration. Ensure that you drink plenty of water to keep yourself hydrated and that natural ventilation is made the most of. If you can create a through draft it is a good thing, however the draft should not be so great that it interferes with the gas shielding required by the welding process.
4/. Fire caused by welding sparks
Your work area can be alight in a second if you’re not careful and do not pay attention to detail in the preparation of your working area. We know that the sparks given off by the welding process are extremely hot and are the perfect source of ignition for any solid fuel fire. Before welding remove any paper, wood, rags, paints and solvents from your work area. Check the floor area in the immediate vicinity (10 ft² min) for flammables and remove them as necessary.
Ensure that you have the appropriate fire extinguisher at hand and that you know how to correctly discharge this equipment in an emergency. If you can have someone as a second pair of eyes to look for early signs of fire, particularly if you are working on a vehicle, in a production area or in a confined space. This person is known as a fire watch. Fire watch should be maintained for a period of up to 1 hour after the welding activity has finished.
Suitable fire extinguishers are Carbon Dioxide or Dry Powder because of the risk of electrical fires in the welding area. Do NOT use a water based extinguisher on an electrical fire.
*NOTE: Fire extinguishers must be fit for purpose and inspected by trained and competent professionals.Only use a fire extinguisher if you feel confident that you can subdue or put the fire out by using it. Do not put yourself at risk. If in doubt sound the alarm and leave the building.
5/. Welding flammable containers or vessels
Try to avoid this as there is a real chance of some form of explosion occurring. Vapour has a much lower flashpoint than the liquid and will explode with much greater energy. If you decide that you are going to undertake this repair you must ensure that any residual vapor has been removed by prolonged high pressure steam cleaning (the longer the better). Needless to say the water vapor left by the steam cleaning process requires time to dry. This type of repair can be expensive to undertake because of the cleaning and drying time involved and the cost of this must be considered against the benefits of buying a new vessel. In this instance “penny pinching” could seriously injure you and others around you.
You may not need to steam clean; the objective here is to nullify the explosive environment of the enclosure. An alternative is to fill the vessel with an inert gas such as Argon or Nitrogen and displace the explosive gases.
6/. Welding fume
Welding uses high temperatures to essentially melt metal at a point local to the heat source. This creates a cloud of harmful smoke that can contains particles of filler wire, parent material, weld metal, oils, paints or grease and the shielding gas being used.This fume is unpleasant and where possible should not be breathed in.
There are lots of actions you can take to protect yourself as a welder.
-Be aware of your breathing zone;This is the area 12” up from the joint area and 12” from the front of your welding helmet. Your objective is to minimise the amount of fume cloud passing through or hanging about in this area. If you use a fume extractor system position the extractor fan nozzle at the back of your breathing zone to draw the fume cloud away from you. An extractor nozzle or hood positioned above your head is completely ineffective and just draws the fume cloud past your breathing zone quicker. The objective is to get the fume cloud away from your breathing zone and not through it quickly.-Don’t expose yourself to welding fume. The Health & Safety Executive issued a directive in Febraury 2019 around the welding fume created by Mild Steel welding. The latest scientific research suggests that all welding fume carries a risk of lung cancer. Ensure you seek advice around your current Respiratory Personal Equipment(RPE) & Local Exhaust Ventilation(LEV).-Take regular breaks away from the task and drink plenty of water.
As mentioned earlier, choose PPE & welding fume extraction based upon your budget and your welding enviroment.All the equipment recommended above will offer a level of protection for you in your own right and become more effective when used in combination. Safety Summary
- Be aware of the hazards involved.
- Check your welding equipment and work area before starting welding.
- Understand your equipment and how it works.
- Ensure you have Respiratory Personal Equipment(RPE) & Local Exhaust Ventilation(LEV) in place.
- Look after your co-workers by purchasing fume extraction & screening off the job.
Next, we explain How MIG welding works in lesson 2