Industrial
How electrically safe is your machinery?
By Stewart Robinson MIET MInstMC, principal engineer and functional safety expert at TÜV SÜD S
afety is one of the most significant issues facing machinery owners today, and the electrical element is an essential consideration for keeping machine
operators and maintenance personnel safe. The key standard for safety of electrical equipment of machines in Europe and the UK is BS EN 60204-1:2018, published by the International Electrotechnical Commission (IEC) and
published in parallel by CENELEC (European Committee for Electrotechnical Standardization). The standard provides requirements and recommendations relating to the electrical equipment of machines which includes, but is not limited to, enclosures, isolators, colour coding of actuators and documentation. Following the UK’s exit from the European Union (EU), the actual process required for manufacturing compliant products has not changed from a legal perspective. As the EU Directives are transposed into National Law, the UK already has a legal system in place that applies. EU harmonised standards have therefore simply been carried across as UK designated standards in order to maintain a single model.
The standard requires that electrical live parts be located inside enclosures or suitably insulated to provide protection against a human having direct contact with them. Any enclosures should only be able to be opened under one of three conditions: 1. A key or tool must be used to open it. 2. Before it can be opened, live parts must be automatically disconnected. 3. If opening with a key or a disconnection device is not possible, opening of the enclosure should only be possible when all live parts are protected against direct contact to at least IP2X or IPXXB (see standard IEC 60529). While the machinery industry has been
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using this standard for many years, it is complex and there are significant changes between the old and new versions. I have highlighted a few key ones below and many of our customers still do not realise that there have been changes, so it’s vital to recognise them and ensure the appropriate changes to process and procedure are made. While the content of Clause 4.4.2 (EMC) was reduced, a detailed informative Annex H was added, which should be helpful to machine builders because it describes practical measures that can be used to reduce the effects of electromagnetic influences. However, detailed guidance is also contained in the specific EMC standards e.g. the IEC 61000-6 series. Clause 5.2 requires that the terminal for the external protective conductor shall be in the same compartment as the incoming supply instead of “in the vicinity”. Also, for the breaking capacity of the supply disconnecting device, the calculation must take into account motors supplied by inverters or similar devices (Power Drive Systems [PDS]). BS EN 60204-1 also allows for the operating means for a supply disconnecting device, that is not intended for emergency operations, to have a supplementary cover or door for protection against environmental conditions. Clause 5.5 is now titled “Devices for isolating electrical equipment” instead of “Devices for disconnecting…”. This is because while there has always been a distinction between “isolation” and “disconnection”, it has not always been easily understood. This addition therefore helps with clarification.
Significant changes were made to section 9.2 “Control functions”, for example clause 9.2.4 is now clause 9.3.6 “Suspension of safety functions and/or protective measures” having specific requirements
for mode selection to deliver additional clarification and emphasis. Section 10.2 “Actuators” was previously “Push-buttons” and includes reserving the red/yellow colour combination for “emergency operation devices”. It also now reserves the colour yellow “…for use in abnormal conditions, for example, in the event of an abnormal condition of the process, or to interrupt an automatic cycle”.
Is your machinery compliant? Section 17 of the standard outlines what technical documentation is required to demonstrate compliance. This includes information relating to a machine’s electrical installation, operation, and maintenance, which can be in the form of drawings, diagrams, charts, tables, and instructions.
While verification can be done at different stages throughout the design and development lifecycle process, even at the end of it, it would be better to do this as early as possible during design. As verification is intended to assure the conformity of a product, it is more cost effective for faults to be identified and
rectified during design, rather than waiting until the final machine is produced.
The extent of the verification that is required is made clear in the specific product standard that relates to each different type of machine. However, where there is no such dedicated standard, EN 60204-1 requires that it must always include: • verification that the electrical equipment complies with its technical documentation • in case of protection against indirect contact by automatic disconnection, conditions for protection by automatic disconnection shall be verified according to 18.2 • functional tests
The complexity of BS EN 60204-1, coupled with the potential lethal consequences if electrical safety is incorrectly administered, means that it is not a process that machine users can afford to get wrong. However, the development of a practical checklist is a useful approach that will help ensure all relevant considerations have been covered.
www.tuvsud.com/uk Components in Electronics April 2022 17
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