Machine Guidelines
Guidelines, markings and risk analyses
The manufacturers of machines and systems as well as their operators are obliged to minimise the safety risk for people in the vicinity of the machines.
Safety-related signalling devices provide support here. For example, a signalling light can be used to indicate the intended deactivation of a machine safety device. This may be necessary, for example, when introducing material into a dangerous area of the machine or system.
Safety related signalling technology
The Machinery Directive is a European directive (2006/42/EC) that relates to the safety of machines and systems. It specifies the essential health and safety requirements that machines must fulfil in order to be sold on the European market. This directive is relevant for a wide range of machine types and applications, including signalling technology.
It regulates a standardised level of protection for accident prevention when using machinery and for placing partly completed machinery on the market within the European Economic Area (EEA), Switzerland and Turkey. Based on a risk analysis, machine manufacturers must assess the hazards posed by a machine or system and take appropriate safety precautions.
CE marking: After a successful conformity assessment and declaration, the machines may be labelled with the CE mark. The CE mark indicates that the machine fulfils the requirements of European legislation.
Overall, the Machinery Directive ensures that signalling technology machines are designed, manufactured and operated safely. This helps to prevent accidents, ensure the safety of users and improve the quality of machinery on the European market.
Start-up warning application example
With complex machines and systems, there is a high risk that communication between the people working on the system will be difficult due to the lack of clarity. To prevent injuries during start-up, the machine manufacturer must install a safety-related start-up warning in the form of visual and acoustic signalling devices. When the operator starts the system at the control panel, the signalling system switches on first. The loud horn signal sounds and the signalling lights are active for three seconds. Then there is a pause, the duration of which depends on how long people usually need to get out of the danger zone to safety. Only then does the system start up.
The signalling devices used for this purpose must be included by the system manufacturer in the risk assessment of the overall system, as a failure of these components can lead to personal injury.
In this case, the standard EN 13849-1 Safety of machinery - Safety-related parts of control systems - Part 1: General principles for design forms the basis for the necessary risk analysis.
In order to be able to evaluate the signalling device used as part of this risk analysis, the machine manufacturer must be provided with a safety parameter, the performance level (PL) of the signalling device. The PL value is determined using a probabilistic approach (probability approach) and is essentially made up of the following two components:
MTTFd value: Mean time to a dangerous failure as a statistical value.
DC - Diagnostic Coverage: This describes the reliability with which the dangerous failure is recognised.
In the specific case of the start-up warning described, the performance level for the signalling devices must be PL c and therefore have a medium level of protection. This is achieved either by monitoring the special signalling devices or by using devices that are so fail-safe due to their design (high MTTFd) that a PL c is achieved even without monitoring. In any case, devices for this application should be certified by an external body, such as TÜV.
SISTEMA database - risk calculation tool
The ‘SISTEMA’ database is a tool used in connection with the Machinery Directive and the ISO 13849-1 standard. The database enables engineers to evaluate the performance level of their safety-related control systems in accordance with ISO 13849-1. This tool facilitates the selection and evaluation of safety components for conformity with the safety requirements of the Machinery Directive.
Tested safety: WERMA signalling devices
WERMA has had safety values determined by the TÜV for selected signalling devices. Machine builders can incorporate these values directly into their risk analyses. They make planning considerably easier and save time.
Signalling devices with the best MTTFd value - confirmed by TÜV
The MTTFd value describes the statistical mean time to dangerous failure (according to standard EN ISO 13849-1). These signalling devices all achieve the highest possible safety value MTTFd > 100 years.
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