LASER SAFETY An active system will


theoretically protect against any power level. Tere are still considerations to be made though, even with active protection, as Tozer noted: ‘With really high powers, you have to consider the passive guarding you’ve got behind the active portion, because if it takes 200ms to shut down a laser then you’ve got to contain the laser beam for that period of time. With a very high power laser of 20kW or 30kW with a small beam diameter, then you could have issues with containing that beam. All these factors have to be considered when designing the enclosure.’ Tere are many variables when it


comes to laser protective equipment, and while safety standards must be met, the design will influence the cost of a system. Pro-Lite Technology runs laser safety training courses at its Cranfield, UK facility to ‘ensure that laser users don’t make a mistake and under protect’, remarked Ian Stansfield, a director at Pro-Lite, ‘but by the same token they don’t spend a fortune on protective equipment – that the user protects where it makes sense.’ Pro-Lite runs the courses in


conjunction with Uvex Academy – Pro-Lite distributes products from Laservision, a German company and part of the Uvex safety group. Te courses are designed to teach a range of people, from laser safety officers to maintenance employees in industry who might have to clean or do other tasks around lasers. ‘When designing a laser safety


Active laser clothing


Lasermet has been developing active clothing and an active laser faceguard for use with high-power handheld lasers. The company will demonstrate its technology at TWI, a research institute based near Cambridge, UK. TWI has built a 5kW laser for nuclear


decommissioning (see Energy article on page 22 for more on this) which sometimes is used as a handheld device. ‘We found a way of incorporating our Laser Jailer [active] system into clothing,’ commented


20


Paul Tozer, managing director of the UK branch of Lasermet. ‘We’ve also developed a safety-rated wireless protocol for the clothing, so that you don’t have to have a trailing cable. It’s easy to use wireless communication, but there’s nothing that exists on the market that’s safety-rated to the highest performance levels.’ Lasermet has developed a wireless safety protocol that achieves performance level E under EN 13849-1, the highest rating there is. ‘Active guarding systems or any


LASER SYSTEMS EUROPE ISSUE 30 • SPRING 2016


interlock system needs to achieve performance level E under EN 13849-1, which is what our Laser Jailer product is rated at,’ Tozer said. Performance level E (PLe) to EN 13849-1 is the standard that governs safety-related control systems. That would apply to any interlock system, including active guarding systems, active windows and active clothing. ‘We’ve developed our wireless communication protocol to meet PLe, which I think is unique,’ he added.


enclosure, first we work out what is needed according to the standards,’ stated Stansfield. ‘Te protection level is based on power density for CW lasers or energy density for pulsed lasers. We take a minimum output power that we expect to see in the system, and work out the distances for enclosures. From this we can specify a certain protection level according to the standard.’


Safety windows Te level of protection given by laser safety windows or eyewear is measured to a certain extent by its optical density, which reflects how effective a material is at blocking the light. According to the EN 207 standard (for more on safety standards, see box), safety eyewear and windows have to have a high enough optical density to stop the


upgrades to an 8kW laser then you need to be thinking, is a passive enclosure good enough?


If the company


light, and the material has to remain intact for five seconds and 50 pulses without damage. Polycarbonates are the preferred


material for protective windows for lower laser powers. However, as power increases, mineral glass is used as it is better at dissipating the heat. Laservision is developing higher power protective polycarbonates for


Barriers and screens can be made using polycarbonate materials


windows and screens. ‘Tere are polycarbonates with really high optical densities, of 11 for instance, which is great, but a 2kW CO2


laser


can cut 18mm thick armour plating, and will melt polycarbonate material very quickly,’ Stansfield explained. Laservision is now releasing high


power polycarbonates, which are competing with a lot of the mineral glass, according to Stansfield. Mineral glass windows are limited in size, which traditionally have maximum dimensions of 100 x 200mm or an A4 paper size. In addition, these sorts of sizes of windows are expensive. ‘Tat’s quite restrictive when people are building systems where they want to view what’s going on inside an enclosure,’ said Stansfield. ‘Tey want bigger windows without compromising on


the protection. Laservision is launching these high-power polycarbonate materials for just such a purpose.’ Tozer at Lasermet warns of the


danger of using polycarbonate windows for high-power systems. ‘Tere are a lot of people using polycarbonate windows where really they’re not appropriate for a multi-kilowatt laser,’ he commented. ‘Above around 300W then a plastic window is really not suitable to protect against a direct beam. Once higher than around 3kW, then a glass window isn’t any good either – you need an active window.’ Lasermet’s Glaser Jailer is an


active guarding window, while Pro-Lite supplies a large active polycarbonate window, which has been tested with a 16kW fibre laser. Pro-Lite’s window is made up of two polycarbonate sheets and a central sheet that acts as a light guide connected to a detector, which shuts the laser off. Te window can be made to dimensions of around 500 x 840mm. ‘Tere’s a big shiſt in the customers we’re seeing wanting to use this specialised polycarbonate material [from Laservision],’ said Stansfield. In addition to the protection level


of windows and eyewear, there are also considerations concerning


@lasersystemsmag | www.lasersystemseurope.com


Laservision/Pro-Lite


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