FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY I
n the machine industry, the significance of functional safety has increased continuously,
with the focus of interest always being the safety of operating and maintenance staff. The other goal has been to minimise the costs of operation and servicing or maintenance. Consequently, machine manufacturing and operation are subject to a host of regulations and requirements. Machinery manufacturers must show
compliance with the European Machinery Directive 2006/42/EC. The harmonised standards EN ISO 13849 (Safety of machinery - Safety-related parts of control systems - General principles for design), Parts 1 and 2 and EN 62061 (Safety of machinery. Functional safety of safety-related electrical, electronic and programmable electronic control systems) cover the safety related parts of control systems within a machine, and can be used to achieve compliance in the field of functional safety. However, as state-of-the-art moves on at
a dramatic pace, with innovations such as Industry 4.0’s smart factories, new components and systems frequently become available which are too technologically advanced for current standard requirements.
Ensuring compliance with the Machinery Directive is becoming more complex as time goes. And with
technologies developing, both IEC 62061 and ISO 13849 are in the process of being significantly updated.
Stewart Robinson, principal engineer and functional safety expert at TÜV SÜD, comments
control systems for machinery’.
DEMONSTRATING COMPLIANCE In order to demonstrate compliance with the Machinery Directive, machine builders can choose to work to EN ISO 13849 or EN 62061. EN 62061 applies to electrical, electronic and programmable electronic control systems, whereas EN ISO 13849-1 is not technology specific so it can be applied for electrical, pneumatic, hydraulic and mechanical safety systems. To add a further layer of confusion, EN ISO
13849-1 also doesn’t make it completely clear which requirements apply to a particular situation, resulting in machine builders often misinterpreting how they should apply the standard. Over the years, both ISO 13849-1 and EN
62061 have seen revisions, but the long-term plan was to simplify the process by merging the two standards, thereby making them more accessible for the machinery community. However, following the collapse of this project, the ISO published an amended version of its standard (EN ISO 13849-1:2015) in December 2015. To address the levels of confusion in the market, the IEC and ISO have issued technical reports (IEC/TR 62061-1 and ISO/TR 23849) - ‘Guidance on the application of ISO 13849-1 and IEC 62061 in the design of safety-related
10 JUNE 2019 | DESIGN SOLUTIONS
COMPLEX REQUIREMENTS In recent years, the requirements imposed on machines and machine systems have grown more comprehensive and complex, as digitalisation and automation progress. This has seen the increasingly widespread use of electrical, electronic or programmable electronic systems (E/E/PES) in the field of safety applications. Growing complexity and connectivity bring new requirements for machinery functional safety, with previously separate applications growing closer together. New applications of functional safety are also emerging, such as collaborative robots working in the same workspace as humans. These technologies have contributed
significantly to greater efficiency and a higher degree of automation, improving operability and profitability. Alongside this, the importance of functional safety within the machinery industry has increased continuously, as the safety system contributes significantly to risk reduction and must therefore be aligned to these more versatile and complex applications.
AUTOMATED SAFETY The increasing connectivity of systems, plus the growing possibilities of remote control, further requires suitable approaches to protect systems against unauthorised access and safety-relevant manipulation of the safety functions that are embedded into both hardware and software. In the past, dangerous machinery movements
could be reliably stopped by opening one of the monitored doors in the safety guarding. However, some safety applications are starting to move away from access prevention and the reliable shutdown of machines, to the automated identification of people to allow for continuous machine operation, in order to minimise disruption to the production line. With such high levels of automated safety, the safety related parts of controls systems will become more complex. This will of course escalate with Industry 4.0/smart manufacturing. Both IEC 62061 and ISO 13849 are therefore
in the process of being significantly updated. At the time of writing, publication dates are not yet confirmed, but we should see something during the latter part of 2019. In the meantime, when using either standard, machine builders need to identify the individual safety functions of a machine, and then assign performance requirements against each of these to ensure that they comply. While functional decomposition (breaking each function into further sub systems) is a detailed and time consuming process, it can help with the calculations and also help to ensure that nothing is missed. While there are software packages that help to
guide users through the process, the growing complexities caused by ever greater technology innovations and integration means ensuring compliance with EN ISO 13849-1 is becoming a more complex and resource hungry task.
TÜV SÜD
www.tuv-sud.co.uk SAFETY MATTERS
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