THE ELECTRIC WELDING ARC AND ITS EFFECTS ON WELDERS.

To analyze the different effects generated by the welding arc, one must first understand what an electric arc is, how it develops, and how it can cause harm.

ELECTRIC ARC.

An electric arc is a very bright and luminous glow that takes on an almost conical shape when unrestricted or uncompressed. This arc is the result of the successful passage of electric current across an air gap from one conductor to another. It can form when two conductors of an electrical circuit come together making electrical contact or a short circuit; when they are separated, and if there is sufficient voltage available to maintain the flow of current, the arc is established and sustained. Considerable heat is generated by the resistance introduced into the current flow across this air gap. These heated and ionized gases (gases that conduct electricity) are called arc plasma, or sometimes referred to as an electric arc. The heat distribution in an arc depends on the current density (amperes per square inch of cross-sectional area of an electrode) at the electrode; seventy percent of the total electrical energy converted into heat is concentrated at the positive electrode at the densities used in welding. This occurs at the point where the electric current passes from the solid medium of the electrode to the gaseous medium of the arc plasma; the remaining heat is distributed in the arc plasma and at the negative work connection. These characteristics make this physicochemical phenomenon suitable for joining metals, but what happens during welding?

The electric arc can reach temperatures between 3,000°C and 15,000°C, which is why steel can be melted within seconds. This reaction generates ultraviolet and infrared rays that cause serious health effects if proper precautions are not taken.

Ultraviolet rays:  Their range begins at wavelengths shorter than what humans can perceive as the color violet; however, this light or wavelength is invisible to the human eye, as it lies beyond the visible spectrum. This radiation is an integral component of solar rays and produces various health effects, as it falls between non-ionizing and ionizing radiation. There are different types of UV radiation — for example, UV-A, UV-B, and UV-C — all of which are associated with the damage they cause to the human body. UV-C radiation is the most harmful to living organisms.

Moderate absorption of UV-B ultraviolet rays enables the synthesis of vitamin D in the skin, which is necessary for calcium absorption and its deposition in bones.

Among the damage that ultraviolet rays can cause to humans are skin effects such as irritation, wrinkles, loss of elasticity, blemishes, and cancer. They can also cause ocular conditions and may trigger systemic lupus erythematosus or actinic keratosis.

Infrared rays. These are a type of electromagnetic and thermal radiation, with a longer wavelength than visible light but shorter than that of microwaves. The wavelength range spans from 0.7 to 1,000 micrometers.  The extent of these rays ranges from 750 nanometers to 1 mm. Bands A, B, and C have boundary limits of 750, 1,400, 3,000, and 100,000 nanometers (nm).

The biological effects of infrared rays are limited due to their low penetration depth; only thermal effects occur. Infrared radiation penetrates the superficial layer of the skin to a depth of no more than 0.8 mm; therefore, the effect is limited to surface heating. It should be noted that wavelengths between 750 and 1,500 nm can cause burns and increased pigmentation. The eye is equipped with protective mechanisms against infrared rays; however, prolonged exposure can produce erythema, corneal lesions, burns, or even opacities.

The intense light associated with an electric arc can cause retinal damage, while infrared radiation can damage the cornea and lead to cataract formation.
Ultraviolet (UV) light from the arc, which is invisible, can cause “welder’s flash” or “arc eye,” even after brief exposure (less than one minute). Symptoms of arc eye typically occur many hours after exposure to ultraviolet light and include a gritty sensation in the eyes, blurred vision, intense pain, tearing, a burning sensation, and headache. It is important to consult a specialist and avoid home remedies, as these may complicate the condition and lead to more serious injuries.

In welding, both types of radiation are present, and as noted, both pose risk factors. Therefore, the use of certified welding filters and helmets is essential. The standard establishing filter regulations is presented below.

PROTECTION AGAINST THE ELECTRIC ARC.

First and foremost, the eyes must be protected from welding arc rays. Keep in mind that these are invisible rays, and the type of filter required depends on the amperage level — that is, on the welding process. The higher the amperage range, the darker the lens shade must be.

Welding protection filters are coded according to standard DIN 4647.

Protection levels for arc welding, from the lightest to the darkest filter:

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