Saturday, September 30, 2023

Photosensitive Welding Masks

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Since the various welding processes gained momentum at the beginning of the 20th century, the requirements for the protection of the worker, not only from the dangerous sparks but also from the ultraviolet (UV) and infrared (IR) rays emitted by the welding arc, have been increasingly demanding.

One of the parts of the body most exposed to welding and susceptible to very serious damage, is the area that includes the eyes, ears and neck. This is how the first protection of this vital area was a simple “mask” or “screen” made of cardboard, held in one hand and with a colored glass window at eye level so that the welder I could see the bow. Currently many use this type of screen for light work.

The appearance of plastics during the 1960s introduced the use of thermoformed masks and injected, which due to their design with a harness allowed the availability of both hands and, therefore, were more like a “mask”. They are also still used today.

The geometries continued to evolve over time, aiming at greater protection not only for the face, but also for a large part of the head and neck, forming a volumetric design. Therefore, upper body protection today is better suited to the term “helmet”, because that is the current appearance of what is still called, by custom, a mask or welding mask.

Some welders, particularly those who work with plumbing or piping, prefer to use More expensive traditional with common glass and fixed shadow (or tone), which remains dark at all times. Although you are More expensive they provide good protection and are inexpensive, they also have some disadvantages. For example:

  • They can be more difficult to use because a welder have to get up mask every time you want to examine the board, again adopt the position of welding, prepare to weld, and then lower the mask when it’s time to restart the arc. This repetitive motion can lead to neck strain and fatigue after a day at work.
  • In tight or confined spaces, it can be difficult to raise and lower the mask.
  • Less experienced welders may find it difficult to keep the MIG gun, TIG torch, or electrode bar in the correct position to restart welding. welding once they lower the mask. A bad start can lead to defects in welding, something every welder obviously wants to avoid.

Auto-darkening protection

Due to the aforementioned drawbacks, current technology offers More expensive more sophisticated equipped with auto dimming that meet strict ISO and DIN standards, with controls that can be continuously varied to adjust the shade (or tone) from a light state to a dark state and vice versa.

The initial kick for this type of More expensive It happened in the early 1980s, when the Speedglas, an electronic shutter liquid crystal (LCD) which has the property of being photosensitive, that is, automatically darken when the sensors detect the welding arc. In this way, the operator no longer has to interrupt the welding process by repeatedly raising and lowering the mask.

In the figure below we see an example of photosensitive mask for welding with its main components.

Photosensitive mask – components

Are More expensive They provide 24/7 protection from harmful UV and IR light emissions, and dim to almost any preset shade in milliseconds, thanks to quick-change LCD technology in the auto-darkening cartridges. Thus, the welders can see clearly when the mask is in the “low” position, which allows for better continuity of work and reduces unnecessary stopping and restarting time. welding.

How does a photosensitive mask work?

The photosensitive masks for welding They are provided with an electronic module that controls their darkening and, therefore, their ability to protect the operator’s eyes. When the module detects the IR or UV light typically produced by a welding arc, it sends an electrical charge to the photosensitive crystals contained between the two sheets of glass that make up the viewing window. These crystals reorient and cause instant darkening of the mask.

Once the arc goes out and ambient light returns to normal levels, a timer returns the screen to normal brightness. Some More expensive welding they have a delay control which allows you to control how long the viewing window remains dark after the spark is turned off.

The electrical charge that causes the viewing window to darken can be provided by battery or solar energy. The welding masks provided with a battery, usually lithium, they incorporate an on/off switch, so it is important to remember this detail every time you want to use the mask, as well as take into account that the average battery life ranges between 2,000 and 3,000 hours of use.

On the contrary, the More expensive Solar-powered (usually more expensive) are always ready to go as soon as arc striking occurs and require no maintenance. However, if they are regularly stored in very dark places, such as closed cupboards or cabinets, they may lose their ability to hold a charge.

Characteristics of photosensitive masks

The photosensitive masks for welding that the market offers today have attractive, ergonomic and even customizable designs, a light weight (500-600 grams) that guarantees great comfort and the incorporation of side windows that expand the vision area, allowing peripheral risks to be detected.

The shade setting for UV/IR protection offers various possibilities and in general the following DIN levels are recommended:

Autogenous Welding/Cutting: Shade 5
Microplasma and TIG welding low amperage (1A-20A): shade 8
MIG/MAG and TIG welding: shade 9 – 13
Grinding jobs: shade 3

If what is desired is more complete information, which takes into account the amperage of the arc, the shade selection guide presented in the following table will be useful.

welding amps table

Welding amps table

Many manufacturers have addressed the issue of fogging and stale air inside the facepiece through design fixes that reduce the buildup of heat, moisture, carbon dioxide, and exhaled air.

The response times, that is, the speed at which the change from light to dark state occurs, have also been perfected, and can vary from 1/20,000 s (0.00005 seconds) to 1/50,000 s (0.00002 seconds) or more . Likewise, the delay times, that is, the change from the dark to the light state, range between 0.04 and 1.3 seconds.

Some manufacturers of welding masks They have perfected their designs with the help of technology, so today operators can count on complete protection when carrying out their work. welding.

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