APPLICATION FOCUS: SAFETY


MITIGATING THE FIRE AND EXPLOSION RISKS OF LASER METAL PROCESSING


Proper extraction system maintenance and design is vital, says BOFA International’s Joshua Evans, to reduce fire and explosion risks associated with laser metal processing


Fibre laser technology looks set to expand rapidly in the next few years, as coding and cutting companies switch from CO2 lasers to take advantage of the reduced running costs and increased productivity gains associated with the technology. An Allied Market Research


report has predicted that the fibre laser market will be worth around $4.4bn by 2025 – compared to $1.8bn just over a year ago – thanks to processing speed improvements unlocked by the high beam quality that they offer.


This has the potential to bring


significant productivity benefits to the laser coding processes used on metals (typically applying sell-by dates, product and tracking information to canned goods), in addition to laser cutting, engraving, machining and AM applications. To set the potential productivity gains into context, it is not unusual for fibre laser coding lines to run at 120,000 cans per hour.


Central to optimising the


return on investment in this new laser era is effective fume extraction during metal processing. Fibre lasers seem to penetrate deeper into the base metal, where previously CO2 lasers only removed the surface oxide. This has implications on the design of the extraction systems used in metal processing, particularly when


42 LASER SYSTEMS EUROPE SUMMER 2019


it comes to managing fire risks during the laser processing of aluminium and titanium, for example in the coding industry.


Fire safety The risk of fire in fibre laser applications is guided by four simple principles: 1. Lasers generate a large quantity of micron and sub- micron-sized particles


2. The smaller a particle, the larger its surface area to mass ratio


3. The larger the surface area, the faster the rate of reaction


4. Aluminium and titanium possess highly exothermic oxidation reactions (fire)


While these principles


provide the conditions for combustion, a properly specified, installed and maintained extraction system will mitigate the risk. Without effective extraction, the laser can generate a large number of


“Fibre lasers penetrate deeper into the base metal … this has implications on the design of the extraction systems used in metal processing”


un-oxidised particulates that can gather around the laser area – in either hoses/ducting, or in filters – or the laser can act as a source of ignition for an object trapped in front of it. While this type of event is


rare, aside from the risk of fire to human health, it will inevitably lead to a disruption in production and costly investigations, let alone causing damage to expensive equipment. That is why working


with reputable equipment manufacturers in specifying and maintaining extraction systems is so important. BOFA, for example, offers solutions for fibre laser systems that


incorporate fire-resistant materials for casings and filters and that extend to thermal cut-out protection, should overheating occur. The objective is to design-out


any fire risks associated with thermal industrial processes, including lasering, particularly where a combustible dust can be generated by the process. This might also include protection through an inline fire-suppression system, which incorporates a fire extinguisher discharge mechanism, automated air flow shut down and isolation valves which cut off the oxygen supply when a fire is detected, thereby protecting the fume extractor


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Figure 1: Particle size distribution of aluminium laser fume in a laser coding application


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