FEATURE MACHINE SAFETY IMPENDING CHANGES TO ELECTRICAL SAFETY REQUIREMENTS


BS EN 60204:2018 was published in the UK last September. In this article, Stewart Robinson MIET MInstMC, principal engineer and functional safety expert at TÜV SÜD Product Service, discusses some key differences between the new standard and IEC 60204:2016


T


he key standard for machinery electrical safety in Europe is EN 60204,


which includes, but is not limited to, enclosures, isolators, colour coding of actuators and documentation. BS EN 60204:2018 was published in the


UK last September, with the target date for publication for all European Member States being 14th March 2019. While it is based on the international standard IEC 60204:2016, there are some key differences between both versions. These differences include where “should” in the IEC version has been replaced by “shall” in the EN, making it much more prescriptive and mandatory in tone. The change from EN 60204:2006


to EN 60204:2018 is littered with updates, and there are some significant technical changes: added requirements to address


applications involving power drive systems (PDS); revised electromagnetic compatibility


(EMC) requirements; clarified overcurrent protection


requirements; requirements for determination of


the short circuit current rating of the electrical equipment; revised protective bonding


requirements and terminology; reorganisation and revision to Clause 9


(control circuits and control functions), including requirements pertaining to safe torque off of Power Drive System (PDS), emergency stop, and control circuit protection; revised symbols for actuators of


control devices; revised technical documentation


requirements; general updating to current special


national conditions, normative standards, and bibliographical references. The complexity of 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. The changes highlighted in the following are just a small selection of those key updates.


KEY CHANGES IEC 60204:2016 now includes a list of “…differing practices of a less permanent nature…” in various countries. For example “Disconnection of the neutral conductor is mandatory in a TN-S system (France and Norway).” This would make it possible for machine builders to


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include disconnection of neutral as a standard feature of the isolators which they use to cover all countries in the European Economic Area (EEA). The new version of the standard also sees


terms and definitions being renumbered and expanded, often to be more specific. For example, the term “basic protection” replaces “protection against direct contact”, “fault protection” replaces “protection against indirect contact”, and “emergency operations” has replaced “emergency stop function”. While Clause 4.4.2 (EMC) is significantly


reduced, a detailed informative Annex H has been added. The clauses in the published versions of both the IEC and EN standards are in fact the same, despite it being previously suggested that the new EN version would have a significantly reduced EMC clause compared to its IEC cousin. The information in Annex H should help machine builders because of the extended detail. However, detailed guidance is also contained in the specific EMC standards e.g. IEC 61000. Clause 5.2 now 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 should now take into account motors supplied by converters or similar devices. And now the operating means for a supply disconnecting device that is not intended for emergency operations may have a supplementary cover or door for protection against environmental conditions. Clause 5.5 is now “Devices for isolating


electrical equipment” instead of “Devices for disconnecting…”. While there has always been a distinction between “isolation” and “disconnection” it has not always been easily understood. This addition helps with clarification. There are significant changes to


section 9.2 “Control functions”. Clause 9.2.4 is now 9.3.6 “Suspension of safety functions and/or protective measures” and has specific requirements for mode selection, delivering additional clarification and emphasis. Section 10.2 is now called “Actuators”


(was “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


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an abnormal condition of the process, or to interrupt an automatic cycle.”


PROVING COMPLIANCE Section 17 of the standard outlines what technical documentation is required to prove 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. The verification process is intended to


assure the conformity of a product, which can be done at different stages throughout the design and development lifecycle process, or at the end of it. Ideally this should be done as early as possible in the design stage as it is more cost effective for faults to be identified and rectified, rather than waiting until the final machine is produced. EN 60204 often requires only a self-


declaration against the conformance process. However, this does depend on the type of machine. For example, if EN 60204 was used for the presumption of conformity of an Annex IV machine, the electrical parts would still be included in the “special procedures” required. Compliance is therefore complex, coupled with the potential lethal consequences if electrical safety is incorrectly administered, this is not a process that machine builders and owners can afford to get wrong.


TÜV SÜD Product Service www.tuv-sud.co.uk


Stewart Robinson MIET MInstMC, principal engineer and functional safety expert at TÜV SÜD Product Service


Electrical safety is not a process that machine builders and owners can afford to get wrong


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