Knowing the dangers and taking adequate precautions
January 15, 2008
Lasers are capable of cutting thin-gauge metal and plate at incredible speeds and with outstanding results. But a laser also is capable of great damage to operators if the proper safety steps are not followed. To keep everyone safe and the laser cutting machine operating, a fabricating operation should have a safety program in place.
Nd:YAG (neodymium-doped yttrium aluminum garnet) lasers are commonly used in laser welding applications. These types of lasers typically are operated inside Class I enclosures, which ensures that a user cannot gain access to the laser during normal operation. (Photos are courtesy of TRUMPF Inc.)
Lasers are used in a variety of industrial manufacturing operations, such as cutting, drilling, welding, marking, and heat treating of metals and other materials. Like any other manufacturing tool, the laser comes with safety concerns that need to be addressed.
Many of the industrial laser tools in use today employ laser beams that are not in the visible spectrum or are obscured by peripheral equipment and not readily visible. While safety awareness is fairly easy with lathes, grinders, extruders, and other tools commonly found on the factory floor, how can you protect yourself and your team from hazards you cannot even see?
The laser beam itself is the first safety concern. It can be dangerous to both the eyes and the skin.
Visible and near-infrared lasers, such as Nd:YAG (see Figure 1), can cause retinal damage, while far-infrared lasers, such as CO2 (see Figure 2), and ultraviolet lasers can cause corneal damage. Injuries occur when a person is overexposed by viewing the laser beam directly or by a specular or diffusely reflected beam. Proper laser safety eyewear and other control measures can help reduce the risk of eye injury. Protective eyewear—which involves lenses of various densities and colors—is tailored specifically to the wavelength and power of the laser being used. Check with a laser professional or industry associations for what would work best for your application.
The CO2 laser has been known to cause skin injuries. Most notable are holes through fingers and third-degree burns. In most cases, these injuries are not debilitating. Once again, proper skin protection can help reduce the risk of injury.
Other nonbeam hazards need to be considered as well. These include laser-generated air contaminants (fumes), fire, explosion, plasma production, and robotic mishaps. One of the most dangerous nonbeam hazards is electrocution. Since 1960 at least eight people have died from contact with high-voltage, laser-related components. Generally, these mishaps occur during maintenance or installation when protective barriers are removed.
Laser-related fires and explosions have resulted in injury and property loss. This can happen in any number of ways. A laser can come into contact with flammable items, causing them to ignite or heat up some other surrounding material (such as cloth) beyond the material's combustion temperature. Clogged ventilation systems and gas cylinders are other sources of fire or explosion hazards.
CO2 lasers are used in many metal fabricating shops for laser cutting of sheet metal.
With all these possible injuries, it might seem that using lasers in the industrial workplace is a bad idea. On the contrary, understanding these hazards has resulted in improved safety for everyone involved.
Strong standards are in place for the safe use of lasers and laser systems, specifically, the American National Standards Institute document ANSI Z136.1, "Safe Use of Lasers." This document was created upon request of the Department of Labor in 1973 and is the principal standard for laser safety in the U.S.
The standard was produced by the consensus of a committee made up of volunteers from industry, government, education, and national professional societies. It has been revised six times, most recently in 2007. It addresses hazard evaluation and classification of lasers and laser systems, control measures, education and training requirements, medical examinations for workers, nonbeam hazards, eye and skin exposures, and laser safety program management.
The ANSI standard also outlines the responsibilities of the laser safety officer (LSO). According to the standard, an LSO is required for all operation of Class 3B and 4 lasers and laser systems. The LSO is defined by ANSI as "one who has authority to monitor and enforce the control of laser hazards and effect the knowledgeable evaluation and control of laser hazards."
The LSO administers the overall laser safety program, with duties such as confirming the classification of lasers, conducting the nominal hazard zone evaluation, ensuring that proper control measures are in place and approving substitute controls, approving standard operating procedures (SOPs), approving eyewear and other protective equipment (including appropriate signs and labels), approving overall facility controls, and conducting proper laser safety training as needed.
In most industrial situations, the LSO is a part-time activity, depending on the number of lasers and general laser activity.
Any organization operating a laser should implement an internal laser policy and effect safety practices based on the ANSI Z136.1 standard, as well as its own corporate safety requirements. Following are steps to take when establishing a laser safety program:
Control measures should be devised to reduce the possibility of exposure of the eye and skin to hazardous laser radiation and to other hazards associated with the operation of lasers and laser systems. These measures apply to users' normal operation and maintenance, as well as to manufacturers during the manufacture, testing, alignment, and servicing of lasers and laser systems.
Engineering control measures are simply those safety measures that are engineered for the specific laser system and application, such as protective housings, key controls, remote interlocks, controlled areas, and laser warning systems.
While many laser hazards can be controlled adequately by engineering features, some must be handled by either administrative or procedural controls. Common controls cover SOPs, authorized personnel, alignment procedures, spectators, and personal protective equipment.
The backbone of any safety program is the continuous effort of management and employees to follow established safety protocols. This can be achieved only with a strong support for training and education.
Industrial lasers are wonderful tools for improving productivity and reducing waste. As we find more and more applications for these tools, our need for vigilance also will grow. Safe operations mean better products, healthy workers, and steady profits.