Welding grade specifications are application specific and are often misunderstood. HighLine Polycarbonate produces a welding grade material that is designed to go around robot welding enclosures. They allow people outside the enclosure to see what is going on inside the enclosure safely. The products were specifically designed to meet the standard ISO 25980: 2014 – “Health and Safety welding and allied processes – transparent welding curtains, strips and screens for arc welding processes”.
Welding grade specifications and ISO 25980: 2014
ISO 25980:2014 has a number of requirements related to light transmission in various parts of the spectrum:
The transmission between 210nm and 313nm shall be less than 2 x 10-5
The transmission between 313nm and 400nm shall be less than 3 x 10-2
For the transmission between 400nm and 1400nm the hazard level G shall be less than 1. Where the calculation to define G is given in the specification. This calculation places more emphasis on reducing light in the violet and blue parts of the spectrum. There is decreasing impact of light in green and yellow parts of the spectrum. As the light gets towards, orange, red and infra-red there is very little impact.
In fact the full range of the near infra-red spectrum is not considered as the specification only considers up to 1400nm.
HighLine has two products that meet this specification, a welding shade red with a luminous transmission of 4.5% and a welding shade green with a luminous transmission of 0.05%.
The emphasis of these welding grade specifications is really to reduce the transmission of light in the lower wavelengths that have the most energy. Therefore, the lower the wavelength of the light, the more of it needs to be removed in order to meet the specification. This is why our green product has to have a lower transmission than our red product. It is also why the specification does not consider wavelengths above 1400nm.
ANSU Z.87.1 – 2003 and the Welding Shade number.
We are often asked what “Welding shade number” is your product? Welding shade number is defined by ANSI Z.87.1-2003 “Practice for Occupational and Educational Eye and Face Protection”. This specification includes protection for welding masks. The application is very different from that covered by ISO.25980:2014. The ANSI standard is to protect the eyes from close up work where the user is looking directly at the welding light source. The ISO standard is designed to protect viewer outside a welding enclosure that does not need to look directly at the welding light source. The welding grade specifications are very different.
When we look at the ANSI standard, it focuses on five areas:
- The effective far ultraviolet transmittance (between 200 and 315nm)
- The near ultraviolet transmittance (between 315 and 380nm)
- The luminous transmittance (between 380 and 780nm)
- The infra-red average transmittance (between 780 and 2000nm)
- The blue light transmittance (between 400 and 1400nm)
Within each of these areas it gives weightings to different wavelengths. For exact details of how each of these values are calculated you will need to review the specification.
Effective far ultraviolet transmittance
HighLine’s welding shade red has an effective far ultraviolet transmittance of 0.0025 and the green has a value of 0.0017. For this parameter the products would meet the welding shade level 8 and level 9 respectively as they let through very little light in this part of the spectrum which is critical to a good welding screen barrier.
The near ultraviolet transmittance.
HighLine’s welding shade red has an affective near ultraviolet transmittance of 0.005 and the green has a value of 0.000. For this parameter the red would meeting the welding shade number of 8. The green would clearly meet level 9 or higher. Again this is important for eye protection.
The luminous transmittance.
The red product has a luminous transmittance (defined by ANSI) of 5.19. The green product has a luminous transmittance (defined by ANSI) of 0.036. These values correspond to welding shade numbers of 4 and 9 respectively.
The infra-red average transmittance.
The red product has an infra-red average transmittance of 28.9% and the green product has a value of 5.28%. The red product would not qualify for a welding shade number. The green would be classified as meeting welding shade 3 in this part of the spectrum. The infra-red wavelengths are much less damaging to the eyes, particularly when used as a welding screen.
The blue light transmittance.
The blue light transmittance of the red product is 0.34 and the value for the green product is 0.049. ANSI specification requires that this value be less than the luminous transmittance. The red product clearly meets this part of the requirements, but as the green has a very low luminous transmittance, it does not.
Welding grade specifications – conclusion.
In the Far UV, near UV, and luminous parts of the spectrum our red product would correspond to Welding shade number of 4 and the green product would correspond to Welding shade number of 9. However, the products do not meeting this welding shade requirements for the infra-red average transmittance and the blue light transmittance part of the specification. The reason that they do not meet these requirements is that the products were not designed for the applications covered by the ANSI specification, they were designed for welding screens which the ISO specification was written for.
To summarize, HighLine’s welding grade products are designed for welding screens and fully meet ISO 25980: 2014 which was written for this application. To give users an idea of how dark or light the products are, the red would be able to meet the UV and visible parts of the ANSI Z87.1 Welding Shade 4 and the green would be able to meet the UV and visible parts of the ANSI Z87.1 Welding Shade 9.