Welding as a profession has its own share of hazards. There are risks of getting burnt and nauseating due to the smoke that emits during welding. But most dangerous is probably the damage of eye that takes place when the arc is created and the harmful electromagnetic energy given off by the arc. This is most dangerous for the eyes because the damage done cannot be undone.
The burnt skin can get cured and the poisonous gas you inhale by accident may be sorted by taking some medicine. But the radiant energy or light radiation happens to affect your eyesight and it cannot be reduced by any method.
welding lens shade chart
So to stay protected while welding, it is your responsibility to arrange for safety glasses, goggles, a good auto-darkening welding helmet or welding face shields. The eyewear should have proper protection on the filter lens, which is indicated by the shade number.
Lens shade number:
The eyewear engineered to give your eyes some protection comes with a particular shade number and that is the general process of understanding how good or useful the eyewear is for your purpose. The shade number provides information about the intensity of the light radiation that it will protect you from. So the higher the shade number is the better protection you will avail from it.
Correct lens shade to use:
This is a myth that the lens shade is corresponded to the amount of protection for the eyes of the wearer. But this is not the real picture. Any well constructed lens has a screen which filters out 100% UV and IR rays or wavelengths, so you get full protection. The shade number means the amount of darkness the lens will provide. This darkness basically differs in requirement for various professions.
- There are some suggested lens numbers that you can use as a guide when you are unsure of the application. These numbers correspond with the welding amperage. But you must choose a shade that allows you to see the puddle clearly and without any difficulty you can weld.
Also the lens should provide ample visibility in time of welding. So the guide may help you to decide which lens number is best suited for your job.
Requirement of lens protection for different profession:
The shade number of lens differs in case of different professionals. The shade that is perfect for a fire watch will not be suitable for a professional in automobile industry. The filter lens which comes along with the welding helmet can be reduced. But the combined value of the lens shade number and helmet should be equal to the value shown in the tables below.
There are different charts for different kind of welding jobs, hereby we are mentioning the same:
Filter lenses for protection during shielded Metal Arc welding
| Operation | Electrode Size-inch (mm) | Arc current (Amperes) | OSHA Minimum protective shade number | ANSI & AWS shade number |
| Shielded metal arc welding (SMAW) | Less than 3/32 (2.4) | Fewer than 60 | 7 | |
| 3/32-5/32 (2.4-4.0) | 60-160 | 8 | 10 | |
| More than 5/32-1/4 (4.0-6.4) | More than 160-250 | 10 | 12 | |
| More than ¼ (6.4) | More than 250-550 | 11 | 14 |
Filter lenses for gas welding and oxygen cutting operations
| Operation | Plate thickness (inches) | Plate thickness (mm) | OSHA Minimum Protective Shade Number | ANSI & AWS Shade Number recommendation |
| Gas welding | Under 1/8 | Under 3.2 | 4 | 5 |
| 1/4 to 1/2 | 3.2 to 12.7 | 5 | 6 | |
| Over 1/2 | Over 12.7 | 6 | 8 | |
| Oxygen cutting | Under 1 | Under 25 | 3 | 4 |
| 1 to 6 | 25 to 150 | 4 | 5 | |
| Over 6 | Over 150 | 5 | 6 |
Fixed shade lens or variable shade lens:
The welding helmets which come with single shade that is pre defined are normally with #10, whereas there are variable shade helmets which can be darkened by a number of shades. It depends upon your choice and comfort level of which welding process you will be using.
If you weld only a single material then a fixed shade lens will suffice. So you should not invest in a helmet with variable shade lens. But if you are flexibly managing to weld different materials and using different procedures to do that, then a variable shade lens is must.
Lens reaction time/ auto darkening:
The emission of IR (Infrared rays) and UV (ultraviolet rays) during welding damages the naked eye. There are high quality auto darkening helmets that protects you by getting activated within 4/10ths of milliseconds. But you will receive such good response time only in the high quality helmets. The darkening takes place right at the moment of the spark. In order to prevent your eyes the lens should get darkened by 1/3600 of a second. In a higher version, you can expect 1/20,000 seconds of response time to get darkened.
Arc sensors:
ADF helmets come with quite a few numbers of sensors that can detect the weld spark and thus the shade gets darker within a very short time. The sensors those are located at the helmet decides how fast the helmet will darken. The position, sensitivity and number of sensors are crucial to decide the quality of the lens shade and the helmet. 2 sensors are good if you are not attempting any out of position welding.
Conclusion:
There are helmets with lenses or else you can get them separately and clip them with the helmets. Also there are corrective lenses that you can wear under the helmet. In time of choosing clip, take the lowest dioptre as it will allow you to see clearly at the time of welding. People aged over 40 should choose higher level for better visibility.