IEC 62061:2021 - What's New and How to Apply It for Machine Safety

What is IEC 62061?

IEC 62061 is an international standard that specifies requirements and provides guidance for the design, integration and validation of safety-related control systems (SCS) for machines. It is applicable to control systems used, either singly or in combination, to carry out safety functions on machines that are not portable by hand while working, including a group of machines working together in a co-ordinated manner.

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IEC 62061 is a machinery sector specific standard within the framework of IEC 61508, which is a generic standard for functional safety of electrical, electronic and programmable electronic systems. The design of complex programmable electronic subsystems or subsystem elements, such as systems on chip or microcontroller boards, is not within the scope of IEC 62061. This is in the scope of IEC 61508 or standards linked to it.

IEC 62061 was first published in 2005, with amendments in 2012 and 2015. The latest edition was published in 2021, with significant technical changes and improvements.

Why is IEC 62061 important for machine safety?

As a result of automation, demand for increased production and reduced operator physical effort, safety-related control systems of machines play an increasing role in the achievement of overall machine safety. Furthermore, the SCS themselves increasingly employ complex electronic technology.

IEC 62061 specifies requirements for the design and implementation of SCS of machines that aim to reduce the risk of hazardous situations arising from the hazards of the machine itself or from a group of machines working together in a co-ordinated manner. It only covers functional safety requirements, which are related to the correct functioning of SCS according to their design intent.

IEC 62061 provides a machine sector specific framework for functional safety of an SCS of machines. It sets out an approach and provides requirements to achieve the necessary performance and facilitates the specification of the safety functions intended to achieve the risk reduction. It also provides methods for verifying and validating that the SCS meets its requirements.

By applying IEC 62061, machine designers, control system manufacturers and integrators, and others involved in the specification, design and validation of an SCS can ensure that their SCS conforms to internationally recognized best practices and standards for machine safety.

How to apply IEC 62061 in the design process?

IEC 62061 covers those aspects of the safety lifecycle that are related to safety requirements allocation through to safety validation. It is intended to be used within the framework of systematic risk reduction, in conjunction with risk assessment described in ISO 12100, which is a standard for general principles of machine design.

The following are the main steps and requirements for applying IEC 62061 in the design process of an SCS:

Risk assessment and safety integrity level assignment

The first step is to identify the hazards and estimate the risks associated with the machine and its intended use. This can be done by using methods such as hazard identification, risk estimation, risk evaluation and risk reduction, as described in ISO 12100.

The next step is to assign a safety integrity level (SIL) to each safety function of the SCS, based on the required risk reduction. A SIL is a measure of the performance required of a safety function to achieve or maintain a safe state for a given hazardous event. There are four SILs, from SIL 1 (lowest) to SIL 4 (highest).

IEC 62061 provides suggested methodologies for SIL assignment, such as risk graph, risk matrix and layer of protection analysis. The SIL assignment should take into account the frequency and duration of exposure to the hazard, the probability of occurrence of the hazardous event, the severity of harm and the possibility of avoiding or limiting harm.

Safety function specification and verification

The next step is to specify the safety functions of the SCS, which are the functions that achieve or maintain a safe state for a given hazardous event. The specification should include the following information:

• The description and identification of the safety function

• The required SIL

• The input and output variables and their characteristics

• The functional behaviour and logic

• The response time and fault tolerance time

• The reset mode and start-up mode

• The diagnostic coverage and test interval

• The common cause failures and their mitigation measures

The next step is to verify that the safety function specification meets its requirements and is consistent with the risk assessment. The verification should be done by using methods such as review, analysis, inspection, testing or simulation.

Safety-related control system architecture and reliability calculation

The next step is to select and evaluate the hardware and software components of the SCS, which are used to implement the safety functions. The selection and evaluation should consider the following aspects:

• The suitability of the components for their intended use and environment

• The conformity of the components with relevant standards and specifications

• The compatibility and interoperability of the components with each other

• The reliability data and failure modes of the components

• The diagnostic capabilities and test procedures of the components

• The configuration management and traceability of the components

The next step is to calculate the reliability of the SCS, which is expressed as the probability of failure per hour (PFH) or as the mean time to dangerous failure (MTTFD). The calculation should take into account the following factors:

• The failure rates and failure modes of the components

• The architecture and redundancy of the SCS

• The diagnostic coverage and test interval of the SCS

• The common cause failures and their mitigation measures

• The demand mode and operation mode of the SCS

IEC 62061 provides methods and formulas for reliability calculation, as well as typical values for failure rates, diagnostic coverage and common cause factors. The calculation should show that the PFH or MTTFD of each safety function meets or exceeds its required SIL.

Safety-related control system integration and validation

The next step is to integrate the SCS with the machine, which involves connecting, installing, configuring, parametrizing, testing and commissioning the SCS according to its specification. The integration should ensure that:

• The SCS functions correctly and safely with the machine

• The SCS does not introduce new hazards or increase existing risks

• The SCS does not interfere with other systems or devices on or near the machine

• The SCS complies with relevant regulations and standards for electrical safety, electromagnetic compatibility, etc.

The next step is to validate that the SCS meets its requirements and achieves its intended purpose. The validation should be done by using methods such as inspection, testing, simulation or operational experience. The validation should demonstrate that:

• The SCS performs its safety functions correctly under normal and fault conditions

• The SCS reduces the risks associated with the hazards to an acceptable level

• The SCS does not adversely affect other aspects of machine performance or usability

What are the main changes in the latest edition of IEC 62061?

IEC 62061:2021 cancels and replaces the first edition, published in 2005, Amendment 1:2012 and Amendment 2:2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:

• The structure has been changed and contents have been updated to reflect the design process of the safety function

• The standard has been extended to non-electrical technologies, such as pneumatic, hydraulic or mechanical systems

• The definitions have been updated to be aligned with IEC 61508-4, which is a standard for terminology and definitions for functional safety

• A functional safety plan has been introduced and configuration management has been updated (Clause 4)

• The requirements on parametrization have been expanded (Clause 6)

• A reference to requirements on security has been added (Subclause 6.8)

• The requirements on periodic testing have been added (Subclause 6.9)

• Various improvements and clarifications on architectures and reliability calculations have been made (Clause 6 and Clause 7)

• The shift from "SILCL" to "maximum SIL" of a subsystem has been made (Clause 7)

• Use cases for software have been described including requirements (Clause 8)

• The requirements on independence for software verification (Clause 8) and validation activities (Clause 9) have been added

• A new informative annex with examples has been added (Annex G)

• New informative annexes on typical MTTFD values, diagnostics and calculation methods for the architectures have been added (Annex C, Annex D and Annex H)

These changes aim to improve the clarity, usability and consistency of the standard, as well as to reflect the current state of the art and best practices in machine safety.

How to download IEC 62061 pdf for free?

IEC 62061 is a copyrighted document that can be purchased from the official IEC webstore or from other authorized distributors. However, there are some options and sources for accessing the standard online for free or at a lower cost.

One option is to use the IEC public commenting platform, which allows anyone to view and comment on draft standards during their development stage. The draft version of IEC 62061:2021 was available for public review until November 2020. Although it may not reflect the final published version, it can provide an overview of the main contents and changes of the standard.

Another option is to use online libraries or databases that offer free or discounted access to standards for academic or research purposes. For example, some universities or institutions may have subscriptions to services such as IEEE Xplore, SAI Global or Techstreet, which include access to IEC standards. Alternatively, some open access repositories or platforms may host copies of standards that are legally shared by their authors or publishers.

A third option is to use online search engines or tools that can help find free or low-cost copies of standards on the web. For example, some websites such as Free Standards PDF Download or Machine Safety Blog may provide links or summaries of standards that are available for download. However, these sources may not be reliable or up-to-date, and may not comply with the copyright laws or terms of use of the standards.

Therefore, it is recommended to use caution and discretion when using these options and sources for accessing IEC 62061 pdf for free. The best way to ensure that you have the latest and most accurate version of the standard is to purchase it from the official IEC webstore or from other authorized distributors.

Conclusion

IEC 62061 is an important standard for machine safety that specifies requirements and provides guidance for the design, integration and validation of safety-related control systems for machines. It is based on the framework of IEC 61508, which is a generic standard for functional safety of electrical, electronic and programmable electronic systems.

IEC 62061 covers those aspects of the safety lifecycle that are related to safety requirements allocation through to safety validation. It provides a machine sector specific methodology and requires users to assign a safety integrity level to each safety function, enable the design of the safety-related control system, and integrate and validate the safety-related control system with the machine.

IEC 62061 was first published in 2005, with amendments in 2012 and 2015. The latest edition was published in 2021, with significant technical changes and improvements. These changes aim to improve the clarity, usability and consistency of the standard, as well as to reflect the current state of the art and best practices in machine safety.

If you are interested in learning more about IEC 62061 or want to purchase a copy of the standard, you can visit the official IEC webstore or other authorized distributors. Alternatively, you can use some of the options and sources mentioned above to access the standard online for free or at a lower cost.

Thank you for reading this article. I hope you found it useful and informative. If you have any questions or feedback, please feel free to contact me. ?

FAQs

Here are some frequently asked questions and answers about IEC 62061:

What is the difference between IEC 62061 and ISO 13849?

• IEC 62061 and ISO 13849 are two international functional safety standards applicable to machinery. They have many similarities, but also some differences. The main difference is that IEC 62061 uses a probabilistic approach based on safety integrity levels (SILs), while ISO 13849 uses a semi-quantitative approach based on performance levels (PLs). Both standards intend to achieve the same risk reduction, but they use different methodologies and terminology.

How to choose between IEC 62061 and ISO 13849?

• There is no definitive answer to this question, as both standards are valid and widely accepted for machine safety. The choice may depend on various factors, such as the type and complexity of the machine, the availability and reliability of data, the preference and experience of the user, and the market and regulatory requirements. In some cases, it may be possible or necessary to use both standards in combination or in parallel.

How to comply with IEC 62061?

• To comply with IEC 62061, users need to follow the requirements and guidance provided by the standard for the design, integration and validation of safety-related control systems for machines. This involves performing a risk assessment and assigning a SIL to each safety function, specifying and verifying the safety function, selecting and evaluating the hardware and software components of the SCS, calculating the reliability of the SCS, integrating and validating the SCS with the machine, and providing information for safe use.

How to calculate SIL in IEC 62061?

• To calculate SIL in IEC 62061, users need to estimate the required risk reduction for each safety function based on the risk assessment. Then, they need to use one of the suggested methodologies for SIL assignment provided by the standard, such as risk graph, risk matrix or layer of protection analysis. These methodologies help users to determine the appropriate SIL for each safety function based on factors such as frequency and duration of exposure to the hazard, probability of occurrence of the hazardous event, severity of harm and possibility of avoiding or limiting harm.

How to download IEC 62061 pdf for free?

• the standards. The best way to ensure that you have the latest and most accurate version of the standard is to purchase it from the official IEC webstore or from other authorized distributors.

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