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Compliance with safety standards in mechanical engineering is a crucial aspect for manufacturers, operators and other parties involved to ensure that machines and their working environments comply with applicable legal requirements and offer the highest level of safety. Therefore, the effective machine and plant safety is a fundamental criterion and forms the basis for accident-free working on machines, plants and equipment. However, the evaluation and testing of all parts usually takes a lot of effort. Generally applicable safety standards are therefore a good way to regulate and subsequently verify the safety of components and products. In this context, this article examines the safety of machinery and some common safety standards and guidelines.
Machine safety in mechanical engineering refers to the design, construction and operation of machines with the objective of preventing accidents and ensuring the safety of persons working with or near these machines. This includes various aspects such as the avoidance of hazard sources, the ergonomics of operating elements, protection against electrical, mechanical or thermal risks, and the implementation of safety precautions such as emergency shut-off switches or protective devices.
The functional safety of machinery refers to the concept that machinery should be designed, constructed and operated in such a way that they reliably fulfill certain safety-related functions, even if errors or malfunctions occur. The objective of functional safety is to minimize the risk of accidents and injuries by identifying potential sources of hazards and dealing with them appropriately.
In order to ensure the functional safety of machines, various measures are taken, including identifying safety functions, the analyzing risks and hazards, determining safety objectives, selecting suitable safety measures, as well as validating and verifying the implemented safety measures.
A risk assessment is a systematic process for identifying, analyzing and evaluating such potential hazards associated with a machine. The main objective is to understand the risks and to identify appropriate risk mitigation measures to ensure the safety of people, the environment and property.
Machinery Directive 2006/42/EC requires manufacturers perform a risk assessment. The risk assessment must cover the entire life cycle of the machine, including manufacture, transport, installation, commissioning, use, maintenance and disposal. The results of the risk assessment must be documented, including all identified hazards, assessments, actions taken and the justification for the safety decisions.
The structured implementation of a risk assessment is regulated in the international standard DIN EN ISO 12100:2011-03 with the title “Safety of machinery - General principles for design - Risk assessment and risk reduction (ISO 12100:2010); German version EN ISO 12100:2010”. ISO 12100 is a so-called A standard and defines general principles and procedures for the implementation of risk assessments relating to machineries.
In this step, the application limits of a machine are determined. Among other things, it must be clearly defined which functions the machine performs and under which conditions the machine can be operated safely and as intended. This also includes user boundaries, i.e. the specification of who is allowed to operate the machine and what qualifications or experience are required to operate the machine safely. In addition, spatial limits such as safety distances and space requirements as well as time limits such as service life of the machine or maintenance intervals of components must be defined.
Hazard identification and analysis is designed to identify potential hazard sources that could be associated with the design, operation or maintenance of a machine or a system. These include mechanical, electrical, thermal, chemical, and ergonomic hazards, as well as hazards related to working environment conditions.
The risk assessment is intended to examine the identified potential hazardous situations in more detail and assess their impacts. Important aspects are the probability of occurrence and the assessment of the severity of potential damage. This involves examining the probability that a certain hazard can actually occur or what type of damage or injuries can be caused if a hazard occurs.
The identified risks are classified based on the probability of occurrence and the severity of the potential damage. This can be done, for example, by using a risk graph. The machinery safety risk graph is a graphical representation used to visualize the potential hazards and identify risk mitigation measures.
Example illustration - Risk graph for risk assessment
S = Severity of the injury: S1 = minor injury, S2 = serious injury
F = Frequency and duration of hazard exposure: F1 = rare or of short duration, F2 = common
P = Possibilities to avoid or limit risk: P1 = possible, P2 = hardly possible
a = low risk, e = high risk
Based on the results of the risk assessment, appropriate protective actions are identified that can contribute to preventing, mitigating or controlling potential hazards.
Risk mitigation covers three steps:
Further standards must be consulted with regard to the technical protective actions. The harmonized standard DIN EN 60204-1 for electrical equipment of machines specifies requirements for the selection and use of electrical protective actions to minimize the risk of electric shock, short circuits and other electrical hazards. This includes measures such as protective grounding, protective insulation, switching off circuits and ground-fault circuit interrupters. In addition, DIN EN 60204-1 includes requirements for electrical control of machines, including emergency shut-off switches, safety controls and other safety-related functions.
The standards EN ISO 13849-1 and 13849-2, on the other hand, deal with the description and implementation of safety-related functions. Safety functions such as emergency shut-off, guard door monitoring, and safe stop functions can be provided by safety controllers. The requirements for such safety controls are regulated in EN ISO 13849-1. ISO 13849-2 sets the requirements for validating safety control systems to ensure that they are properly designed, implemented, and operated. This includes testing, analysis, and documentation to ensure that the safety controls meet the expected performance requirements.
This step involves reassessing the risks after the risk mitigation measures have been implemented. It is checked whether the measures taken were effective and have actually reduced the risk to an acceptable level. In this assessment the same criteria used in the original risk assessment can be applied, including the probability and severity of potential damages.
All steps of the risk management process must be carefully documented. This includes the results of the original risk assessment, the identified hazards and risks, the assessment and selection of the risk reduction measures, as well as all measures that have actually been implemented.
The CE marking on machinery is a symbol that indicates that the machinery complies with the applicable European Directives and Standards with regard to health, safety and environmental protection. The CE marking indicates that the manufacturer or its authorized representative declares that the product meets the applicable requirements specified in the corresponding EU Directives. For machinery and other technical products, the most important guidelines are the Machinery Directive (2006/42/EC), the Low Voltage Directive (2014/35/EU) and the EMC Directive (2014/30/EU).
The Machinery Directive (2006/42/EC) is a European Directive that defines the requirements for machinery and safety-relevant components that are placed on the European market. It establishes basic safety and health requirements that manufacturers must meet to ensure that machinery can be used safely and as intended. The Directive covers various aspects such as the design, manufacture, operation and maintenance of machinery as well as the risk assessment and the CE marking.
The Low Voltage Directive (2014/35/EU) regulates the safety requirements for electrical equipment of machines and other products operating at a voltage of 50 to 1000 volts alternating current or 75 to 1500 volts direct current. It ensures that electrical equipment is designed and manufactured safely to minimize the risk of electrical shock, short circuits, and other electrical hazards. The Directive relates to the design, manufacture and CE marking of electrical products.
The EMC Directive (2014/30/EU) specifies the requirements for the electromagnetic compatibility of electrical and electronic equipment. It ensures that equipment is designed and manufactured in such a way that it can prevent or tolerate electromagnetic interference so as not to cause interference with other equipment. The directive covers various aspects such as electromagnetic emissions, immunity to interference and the CE marking of equipment.
It is important to note that the CE marking on a machine should not be considered as a quality mark or certificate, but it merely indicates that the machine complies with the applicable requirements. Compliance with the CE marking is verified through a series of procedures and assessments that must be carried out by manufacturers before the machine can be placed on the market.