Greg Blackman assesses the implications of revised EU PPE regulations, which ask for an operational lifespan to be put on laser safety eyewear
A new EU regulation on personal protective equipment (PPE), which came into effect on 21 April, will mean laser eyewear manufacturers will have to place a shelf life and an operational life on their products.
PPE regulation 2016/425 will have significant implications for manufacturers and users of laser safety eyewear. Manufacturers will have to put a date stamp on their products and give them a shelf life as well as an operational life once they are sold – both time periods are yet to be defined – after which the user will have to scrap the eyewear or have it recertified as being fit for purpose.
The new PPE regulation was established in 2016 with a two-year transition period, which ended on 21 April. Products made before 21 April are allowed to be sold within the next 12 months, as long as the certificate is valid until April 2019 – the old certificates will not be renewed.
The directive covers all personal protective equipment including laser safety eyewear. Manufacturers of PPE now have to, firstly, provide a certificate of conformance for their product; secondly, manufacturers or resellers are responsible for ensuring that PPE is fit for purpose; and the third change is that manufacturers must specify a rated shelf life and operational life for their products.
Robert Yeo, managing director of Pro-Lite Technology, updated members of the UK Association for Industrial Laser Users (AILU) about the changes to the PPE regulation at AILU’s annual general meeting on 26 April. Speaking to Electro Optics, he explained that the EU was attempting to solve the problem of end users buying PPE based on price from internet resellers without any technical consultation, which is especially dangerous for equipment like laser safety eyewear.
Pro-Lite distributes laser safety goggles from Laservision, part of the Uvex Safety Group. ‘As resellers we [Pro-Lite] are responsible for ensuring that what we sell is suitable for the application,’ Yeo commented, adding that the company, as a matter of course, would match the eyewear it sells to the type of laser, based on various calculations.
Putting a shelf life and an operational life on laser safety eyewear is, however, a new requirement for manufacturers of laser safety equipment. In the wider context of PPE – where most of the products, such as gloves, shoes and respirators, are cheap or disposable – defining an operating period doesn’t have a huge cost implication. But for laser safety eyewear where the average selling price is typically hundreds, or in some cases for specialist applications, thousands of pounds for a pair of goggles, ‘the fact that the EU is now demanding that the product theoretically has to be thrown away after a certain period of time becomes an expensive problem’, Yeo remarked.
Pro-Lite advises users not to scrap eyewear after it has exceeded its operation life, but they should speak to the supplier who can advise if it’s possible to return it to the manufacturer so that it can be recertified.
‘No manufacturer, including Laservision, has yet stuck their head above the parapet and said: “this is the storage period, this is the usage period for my product”,’ Yeo continued. ‘Whatever those numbers are will be highly contentious, because we’re going to be telling our customers you can only use your eyewear for a certain number of years, after which they have to be replaced or recertified at some cost.’
Companies have to submit products for independent testing in order to sell laser safety eyewear; manufacturers cannot self-certify. To apply a CE mark to the eyewear, manufacturers have to conform to the European PPE directive and the European standard EN207. EN207 takes into account the optical density of the filter – the percentage of light transmitted through the filter – along with ensuring the eyewear can withstand the power density from the laser for five seconds or 50 pulses. The level of protection for a specific laser will depend on factors like wavelength, power or energy of the laser, the size of the beam, pulse repetition frequency and pulse length, among other criteria. Eyewear filters are tested to destruction to determine their damage threshold.
EN207 was last revised in 2017 and takes into account the beam diameter of the laser. The revision effectively forces the user to buy slightly more protective eyewear for continuous wave lasers.
Laser safety eyewear is usually made of a plastic frame and a mineral glass or plastic filter – higher power lasers tend to require an absorbing mineral glass filter. The frame mustn’t have a lower damage threshold than the filter. There are degradation mechanisms for eyewear: plastic materials can chemically degrade, glass and plastic can bleach, glass filter materials can delaminate, or a customer might scratch the surface, which can cause the beam to burn through the filter material more quickly. ‘There’s certainly nothing wrong with the idea that a product has a certain lifetime, but the PPE regulations don’t tell the manufacturer how to determine this; it’s up to the manufacturer to specify what they consider to be the storage and usage life,' Yeo said.
This could put manufacturers in a dilemma, and it’s basically a question of risk management. Manufacturers will have statistical data on the lifetime of their products, but this has to be balanced against the user taking legal action if something goes wrong. On the one hand, manufacturers don’t want to make lifetimes too short because that will put them at a commercial disadvantage compared to other suppliers – this equipment isn’t cheap – while on the other hand, an indefinite operating life could result in a lawsuit if the product fails after a certain period of time.
‘Laser safety eyewear is effectively going to be treated as disposable [under the new PPE directive],’ Yeo said.
‘Manufacturers will have to nail their colours to the mast and say “this is our storage life, this is our operational life”, and they will probably be quite conservative numbers.’
The new PPE regulation puts the emphasis on the manufacturer or reseller to ensure the product sold is fit for the customer’s purpose, which for specifying laser safety equipment can be quite complex. Users normally need expert guidance. Software can help – Lasermet is the sole supplier of LaserSafe PC laser safety calculation software – while Laservision has designed a demonstrator product that uses RFID to match the protective equipment to the laser type to make it easier for the user to ensure they are protected. Laservision will be showing the demonstrator at the trade fair Lasys, in Stuttgart, in June.
‘A lot of users find it hard to understand how laser protection levels are specified in the EN207 standard,’ observed Dr Roland Mayerhofer, business development manager at Laservision. ‘There’s a lot of information and different ways of specifying lasers, for example according to energy density or power density. This is one of the things that need to be improved, to make it easier for the user to understand if they are wearing the correct goggles for the laser.’
Laservision will show several eyewear products equipped with RFID tags at Lasys. Users can scan with a smartphone RFID reader to bring up various product specifications, including laser protection levels, user manuals, cleaning advice and spare part or accessory lists. A second RFID could be placed on the laser device containing its specifications, so that the laser can be matched to the correct safety eyewear, depending on how the laser will be used.
LaserSafe PC software, from Lasermet, is designed to assess hazards and the level of protection needed for a laser installation – ‘what you want is to be able to verify that all [safety] eventualities are covered without testing every one. This is where the value of good laser safety calculation software comes in,’ said Jim Webb, the software’s author and owner of GL Services, which makes the software. Working closely with the late Professor Bryan Tozer, who founded Lasermet and helped write the forerunner to the BS 60825 laser safety standard, Webb developed the software originally for assessing safe scenarios for lasers at the BBC.
‘Good software enables laser safety officers to make informed decisions regarding laser safety once they are provided with the right laser protection information conforming to the appropriate standard,’ Webb continued. The standards are IEC/EN 60825 for Europe (EN207 is just for laser eyewear) and ANSI Z 136 or CDRH 21 CFR 1040-10 for the USA.
Software calculations are only as good as the data the user puts in, but laser safety calculation software can help to engineer a safe laser solution.
One example that Webb gave was a laser enclosure where the cabin roof had to remain open to the rest of the manufacturing facility. An assessment was made about whether the laser used would pose any threat to those nearby if the beam pointed upwards and reflected off the underside of the building. Calculations made using LaserSafe PC software showed that under the worst potential scenario there would be so little laser radiation exposure that the situation was deemed to be laser safe and therefore conformed to the EN60825-1 laser safety standard. No laser test firings were necessary for the enclosure because of the engineering controls in place, and the certification that the materials used in each of the modular wall panels complied with the EN60825-4 levels for power density.
The calculations showed the amount of laser energy transmitted to the laser cabin walls was well within limits specified for the permissible exposure level (PEL) and therefore safe.
LaserSafe PC gives results for all major standards; it offers safety eyewear recommendations, product classification to a specified standard, labelling recommendations for equipment and enclosures based on the required standard, and it provides documentation.
The storage and operational lifetime of laser safety eyewear will most likely differ depending on whether the filters are made from polymer or mineral glass. Mineral glass is generally used to protect against higher powers, but polymer filters are preferable, because they are lighter and the goggles are more comfortable to wear. Mayerhofer, at Laservision, noted that there’s a trend towards using polymer safety windows over glass versions, as polymer windows can be made larger, up to 2 x 3 metres if necessary – glass windows are restricted to A4 size.
UK optical filter manufacturer, Brinell Vision, is now starting to coat complex Bragg mirrors onto plastics, which has only been possible on glass till now. The firm’s Adam Brierley presented the technology at AILU’s annual general meeting in April.
A Bragg mirror is a stack of high and low refractive index coatings that creates interference. By selecting the right materials with the correct coating process, Brierley explained that the absorption properties of the mirror can be reduced down to fractions of a per cent, less than 0.1 per cent absorption, for instance. This gives an almost 100 per cent mirror coating. In this way, the power handling of the plastic is enhanced because most of the energy is reflected away, while at the same time the laser blocking is increased as less laser light gets through.
Laser testing of coated plasic lenses produced by Brinell Vision, which has started coating complex Bragg mirrors into plastics
Brierley said that a low-level laser coating would be around 24 to 30 layers, but higher powers coatings can reach more than 60 layers. Typically, a 12-layer coating would give an optical density of one, according to Brierley. Going to 48 layers might just about achieve an optical density of three. ‘A combination of absorbing plastic with a high reflection coating would take its power handling up to that provided by glass – roughly 1kW/mm2,’ he said. There are some glasses that can go up to 10kW/mm2, but these would tend to have both absorption and mirror coatings.
The ability to put a Bragg mirror coating on polymers is thanks to advances in the coating deposition process. High temperature deposition can be used to coat glass substrates, but this is unsuitable for working with plastics. ‘We’re now using much more sophisticated coating methods to give the same quality of coating at 60°C,’ Brierley said. ‘Generally, we’re using plasma processes that are either plasma-assisted physical vapour deposition, or high-energy pulsed plasma sputtering.’
Engineering a safe solution
New laser technology can also generate unanticipated hazards – ultrashort pulsed laser processing can produce secondary radiation, notably soft x-rays from the plasma formed when machining metals at high energy densities. The levels are very low – similar to exposure levels of soft x-rays from flying at 12,000 metres, according to Mayerhofer, at Laservision. The hazard cannot be underestimated, he added, and there’s no measurement device for the levels of radiation produced.
Whether or not the revised EU PPE regulation will curb laser users buying cheap safety eyewear without technical consultation remains to be seen. Whatever happens though, laser safety eyewear manufacturers have a year to decide on the operational life of their products.
Suppliers of laser safety products like Laser Components and Lasermet will specify the equipment needed to protect against a certain laser set-up, but there can often be varying levels of understanding from laser users as to what safety equipment is required.
According to Andrew Gilbert at laser equipment provider Laser Components, customers can be told to buy eyewear by their organisation without knowing much about the laser source. He said that Laser Components has had issues where customers buy the same eyewear – because that’s what they’ve always bought – even when the laser wavelength has changed.
Laser Components supplies laser safety curtains from Kentek, along with small enclosures, eyewear and safety windows. Absorption curtains are used to surround an area and contain any stray laser light. For low powers, Gilbert suggests a Flex-Guard curtain, a fabric curtain that seals off an area. But moving to higher powers, he said that aluminium Ever-Guard panels are required.
As the power levels rise, protective enclosures and laser safety interlock controls can come into play. Typically, at up to around 5kW, lasers can be contained in a certified passive cabin for a specific power density, providing the density is not exceeded, according to Lasermet.
Active enclosures are required for lasers in excess of 5kW and those with high-power densities. This is especially critical for three-dimensional multi-axis robots, where the laser beam could potentially point around the cabin, Lasermet advised. In addition, there is the possibility of reflections that can develop when metal is melted into a liquid ball, which can then reflect the laser light.
Active laser guarding ensures the laser is immediately switched off if the beam is inadvertently pointed anywhere around the enclosure and strikes the wall, roof or doors. Lasermet supplies both passive and active enclosures, as well as interlock controllers.