Overview of the main national and international requirements concerning the safety of machinery and functional safety.
Do your products fall within the scope of Machinery Directive 2006/42/EC? Are they intended for the European single market? If so, you must observe the requirements of the Machinery Directive. It is only when these requirements are met in full that machines are allowed to bear the CE mark. This mark is required in order for a machine to be placed on the market and operated without restrictions in the European Economic Area.
The aim of the Machinery Directive is to reduce the number of accidents that occur when using machinery. This directive therefore requires that the aspect of safety is included in the design and construction of machinery. In addition, you must also make sure that the technical documentation required by the Machinery Directive has been created. The technical documentation for a machine must make it possible to assess whether the machine complies with the requirements of the Machinery Directive.
The manufacturer of a machine or their authorized representative is responsible for creating the technical documents as well as adhering to all requirements.
In addition to traditional safety functions, such as emergency stop equipment, programmable and networked safety systems are increasingly being used to safeguard complex machines.
In the interview, our safety and security experts discuss the implications of the current revision of international standards ISO 13849 and IEC 62061 for safety-related software and the topic of cybersecurity.
The Machinery Directive contains essential health and safety requirements. The harmonized standards for the Machinery Directive are listed in the corresponding Official Journal of the European Union.
A machine meets the essential health and safety requirements if it has been manufactured in accordance with these harmonized standards.
The EN standards are divided into various types:
Functional safety concerns the correct application of safety-related (control) systems and other risk reduction measures that are crucial to the safety of a system. In this case, when a critical error occurs, the controller initiates the safe state.
Standards EN 62061 and EN ISO 13849-1 were derived from EN 61508 for the machine building sector. Both of these standards specifically address the requirements for safety-related components of control systems on machinery.
The following standards for functional safety are the main standards:
The term “harmonized standards” refers to European standards for products. They are part of the European Commission's “New Approach” where essential requirements for products are defined by standards organizations CEN and CENELEC. The harmonized standards are published in the Official Journal of the EU. Only goods and services that satisfy the essential requirements may be placed on the market. They can be identified by certificates or CE markings.
For example, if a machine has been manufactured in accordance with the specified harmonized standards, it can be assumed that the machine satisfies the essential health and safety requirements of the Machinery Directive. EN 62061 and EN ISO 13849-1 were derived from EN 61508 specifically for the machine building sector. Both of these standards address the specific requirements for safety-related parts of control systems on machinery.
Both standards are harmonized for the Machinery Directive and represent state-of-the-art technology. Unlike the previous standard, EN 954, these standards can also be applied for complex and programmable systems. In addition, they include all aspects of functional safety derived from EN 61508. It is therefore no longer the case that only deterministic aspects play a role. Furthermore, the statistical probability of failure of systems as well as organizational measures, measures for fault avoidance, and measures for error detection are also important.
The degree of safety is measured in both standards by the level of safety integrity. EN 62061 uses SIL 1 to SIL 3 and EN 13849 uses PL a to PL e as discrete levels for safety integrity.
Why are there two different standards for supposedly the same area of application? You'll find the answers to this question in the table below.
EN 62061 | EN ISO 13849-1 |
---|---|
EN 62061 describes the functional safety aspects of safety-related electrical, electronic, and programmable control systems. | EN ISO 13849-1 describes the design of safety-related parts of control systems. An important parameter for the reliability of safety-related functions is the performance level (PL). |
Simple electromechanical systems such as relays or electronics. | Simple electromechanical systems such as relays or electronics. |
Complex electronic systems as well as programmable systems with all architectures. | Complex electronic systems as well as programmable systems with planned architectures. |
The requirements are specifically designed for electrical control systems. Nevertheless, the defined framework and methodology can be applied to other forms of technology. | Can be applied directly for technology outside of electrical engineering, such as hydraulics and pneumatics. |
EN 62061
An important parameter for the reliability of safety-related functions is the safety integrity level (SIL). Various criteria are assessed in order to determine the required SIL:
EN ISO 13849-1
In order to determine the required PL, various criteria must be assessed: the extent of harm, frequency and duration as well as possibilities for avoiding the hazard.
Risk parameters
Note: Where the probability of occurrence can be classified as low, PLr may be reduced by one level.
EN 62061 and EN ISO 13849-1
When it comes to the specification of the functional requirement, the relevant safety functions must be described in detail. To ensure this is done, the crucial interfaces to other control functions and error responses must be defined. Finally, you must define the safety integrity level (SIL) or performance level (PL).
EN 62061
The safety-related parameter for subsystems is based on the following values:
Relationship between the PL and SIL concepts
EN ISO 13849-1
The performance level (PL) of the safety-related part of a control system (SRP/CS) is determined by assessing the following parameters:
EN 62061 | EN ISO 13849-1 |
---|---|
As a result of hardware failures, it is possible that other dangerous failures of the SRCF (safety-related control function) may occur. Here the probability must be less than or equal to the failure threshold defined in the specification (step 2). The SIL (safety integrity level) that is achieved by the SRECS (safety-related electrical control system) is less than or equal to the lowest SILCL (safety integrity level claim limit) of any subsystem involved in the performance of the safety function. |
For the various safety functions, the PL (performance level) of the corresponding SRP/CS (safety-related parts of control systems) must match the “required PL”. Where various SRP/CS form part of a safety function, their PLs must be greater than or equal to the required performance level for this function. |
EN 62061 and EN ISO 13849-1
Finally, the entire safety-related control function of an application must be assessed to validate its capability in the application. Here suitability can be determined by analysis or testing, for example, by simulating defined error types.
Source:
In accordance with ZVEI – Safety of Machinery: Notes on the application of standards EN 62061 and EN ISO 13849-1 (Edition 2).
Technical market access conditions for essential electrical products
Europe | USA | China | Brazil | |
---|---|---|---|---|
Mandatory certification with mark | (-) | (+) | + | (+) |
(Quasi-) monopoly of the certification authority | - | (+) | + | - |
Mandatory works inspections (with follow-up inspections) | (-) | (+) | + | (+) |
Property rights possible in standards | (-) | + | - | (-) |
Specific national standards instead of international standards | (-) | + | (+) | (+) |
Non-recognition of test results | - | (+) | (+) | (-) |
Public “Black List” | (-) | (+) | (+) | (-) |
Key: + Applies / (+) Applies to a greater extent / (-) Applies to a lesser extent / - Does not apply
Source: ZVEI
Functional safety – standards and directives
Several international institutions are responsible for safety directives and standards:
New Approach
Joint efforts of the three European Standards Organizations (CEN, CENELEC, and ETSI) together with both the European Commission and EFTA.
The European Committee for Standardization
Information on European standards, applications, and developments.
European Committee for Electrotechnical Standardization
Standards for the field of electrotechnical engineering.
International Organization for Standardization
International standards for business, government, and society.
International Electrotechnical Commission
International standards and conformity assessment for all electrical, electronic, and related technologies.
EUR-Lex
Portal for access to EU law.
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