In accordance with the provisions of the 2006/42/EC directive, the risk assessment method related to the emission of laser radiation by machines should be carried out in accordance with the following harmonized standards:
· EN 12100:2012: Safety of machinery. General principles for design. Risk assessment and risk reduction
· EN ISO 11145:2010: Optics and photonics. Lasers and laser-related equipment. Vocabulary and symbols.
· EN 12254: 2010: Screens for laser working places. Safety requirements and testing.
From the above-mentioned standards, only the EN 12100 standard describes the general principles of risk assessment, while the other two, although they concern laser radiation, in fact do not describe the risk assessment method, as the EN 11145 standard provides only the definition from photonics and laser equipment domains, and the EN 12254 standard provides the principles of selection of screens for laser working places, which already refers to the aspect of risk reduction and the provision of means of protection against laser radiation emitted from the machine.
The other technical standards that can be used in risk assessment during the design phase of machines are:
· EN ISO11553-1 Safety of machinery. Laser processing machines. Part 1: General safety requirements
· EN ISO11553-2 Safety of machinery. Laser processing machines. Part 2. Safety requirements for hand-held laser processing devices
In accordance with the EN ISO 12100:2010 standard, the risk assessment of a machine, including a machine containing a laser device, is composed of two stages:
1. Risk analysis, i.e.:
· determining the limits of the machine (use, space, lifetime of the machine, properties of the workpiece, the environment, etc.).
· hazard identification for all the life cycles of the machine (commissioning, adjustment, setting, emergency stop, use during normal machine operation, maintenance);
· risk assessment (defining: the probability of the damage and the severity of the damage, people exposed, the type, frequency and duration of exposure, the human factor, the usefulness of protective measures);
2. Risk evaluation (checking whether the risk is sufficiently reduced):
As a result of the risk analysis, the information required for its evaluation is obtained, which, in turn, allows to make decisions about the necessity or lack of the necessity to reduce the risk. These decisions should be supported by qualitative and, where appropriate, quantitative method of estimating the risks related to the risks associated with laser radiation emitted by the machine.
The essential aspect here is the safety class of a laser device used in the machine and determining what will be the laser class after installation of the laser device in the machine. Depending on laser beam enclosure, introduction of beam limiters, expanders or optical instruments through which the beam passes, the laser safety class of a given machine might be different than the one of the laser integrated into this machine. Therefore, there is a need to determine the laser safety class for a newly manufactured machine, and thus to carry out the risk assessment of the potential exposure of its user to the direct or reflected laser beam. Determining the laser safety class is the responsibility of the manufacturer of the machine. To do so, it is necessary to carry out measurements of parameters of laser radiation in accordance with the IEC/TR 60825-13 standard: Safety of laser products. Part 13. Measurements for classification of laser products. Such measurements are carried out by specialized laboratories and there is no need to carry them out by the manufacturer.
It should be noted that the risk assessment should be carried out for different stages of the life of the machine, when the laser beam is emitted by the machine. This applies in particular to such phases as:
· setting (especially during adjustment of the laser — when a person is exposed to direct laser radiation; usually collective protection measures are not used; instead only goggles selected in accordance with the EN 208:2009 standard are used)
· operation — use of the machine during its normal operation (a person can be exposed to direct or reflected laser radiation; collective protection measures are usually used, and — if needed — protective goggles selected in accordance with the EN 207:2009 standard)
· maintenance of the machine (if there is a possibility of turning the laser source on)
When assessing the risk associated with laser radiation, the hazards posed by direct or reflected laser beam should be considered in the first place. Depending on the class of the laser, a potential health hazard differs. In the case of lasers of class 3B and 4, the risk assessment should be further performed based on the measurements of the reflected laser radiation.
Exposure to the laser beam typical for materials processing, where class 4 lasers are used (that is, posing a potential hazard to the eyes and skin by direct and reflected beam), may cause moderate or serious injury. The type and the severity of the damage depend on the wavelength of the laser, the type of exposed tissue (eyes, skin) beam parameters (power/energy mode, pulse length and frequency of repetition with pulse operation, and divergence of the beam). The probability of such exposure is a critical variable factor in the risk assessment. Reducing the risk to acceptable levels is an iterative process, and there is virtually no standard approach to procedures and documentation of the process, and general and universal procedure is provided by the EN ISO 12100:2010 standard.
After identifying the risks, assess the risk for each hazardous situation by identifying risk elements such as the severity of the damage and the probability of the damage. When determining these elements, the following aspects should be taken into consideration: the type, frequency and duration of exposure, human factors (fatigue, psychomotor performance, experience, stress, etc.), the usefulness of protective measures and the possibility of circumventing them. In the case of laser radiation by a machine, the measurements need to be made e.g. in relation to existing similar machine or prototype machine which allows the designer to:
· carry out the quantitative risk evaluation related to emissions;
· carry out the assessment of the effectiveness of protective measures implemented in the design phase;
· provide potential buyers with quantitative data on emissions in the technical documentation;
· provide users with quantitative data on emissions in information materials related to the use.
Examples of hazards and their effects are provided in annex 18.
The exposure limit values are generally determined based on relevant standards and directives, and if they are missing, based on the comparison with commercially available similar machines.
After estimating the risk, risk evaluation should be carried out in order to determine if it is necessary to reduce the risk. If risk reduction is necessary, appropriate protective measures need to be selected and applied. The decision if the risk was sufficiently reduced should be made after completing each of the steps for risk reduction, such as: the design solutions secure on their own, the application of technical protective measures, the information on use. As part of this iterative process in each case the designer should check whether the use of new protective measures did not result in the emergence of additional risks or increase in other risks. If indeed there are new hazards, then they should be included on the list of identified risks and appropriate protective measures need to be determined. The aim of these measures is to ensure sufficient risk reduction, which is achieved when:
· all types of work and all ways of interaction were taken into account;
· all hazards were eliminated or risks caused by them were reduced to the lowest level possible in practice;
· all potential new hazards that have emerged along with the protective measures were properly identified and appropriate protective measures used;
· the users were fully informed and warned of the residual risks;
· the adopted protective measures are compatible;
· the consequences of the use of a machine designed for professional/industrial use in the non-professional/non-industrial field were sufficiently taken into account.
The exposure limit values are generally determined based on relevant standards and directives, and if they are missing, based on the comparison with commercially available similar machines.
The summary of the activities consists in checking if the machine meets the essential safety requirements, which are summarized in the form of a short checklist. This list can be used in risk assessment — for hazard identification and assessment of potential health risks.