Machinery Directive for machine safety requirements

A preview of IEC 60204-1 and a comparison with BSEN 60204-1

Many readers will be familiar with BS EN 60204-1: 1998 and some will be aware that this may be superseded later in 2003 or early2 004 by IEC 60204-1.

Many readers will undoubtedly be familiar with BS EN 60204-1: 1998 (Safety of machinery. Electrical equipment of machines. General requirements), and some will be aware that this is most probably going to be superseded later in 2003 or early in 2004 by IEC 60204-1 (Safety of machinery. Electrical equipment of machines. Part 1: General requirements). For those less familiar with the topic, BS EN 60204-1: 1998 relates to the application of electrical and electronic equipment and systems to machines not portable by hand while working, including groups of machines working together in a co-ordinated manner but excluding higher level systems aspects (ie communications between systems). There is currently a Committee Draft of IEC 60204-1 that is at Edition 5.0 and is dated March 2002. Comments have been requested by June 2002 so there is a reasonable chance that the standard will be ratified within the next six months or so. Nevertheless, it is still possible that there will be last-minute changes, so it should not be assumed that the final standard will be identical to this draft. However, we can learn a great deal from the current committee draft, especially the direction in which the standard is going. For example, the main effects are those changes in clause 9 that allow the use of software, programmable electronic systems and communications networks in machine safety systems. This is a major step to bring the standard in line with the state-of-the-art and, in comparison with this, other changes seem minor. Detailed comparison between old and new The first thing to note is that the scope, references and definitions remain unchanged. Clause 5.4 relates to devices for switching off and for the prevention of unexpected start-up. An addition in the new standard is that it is now permitted to use control isolation in specific circumstances, such as for inspections or adjustments. Clause 7.2.4 relates to control circuits, and the new standard gives examples of overcurrent protection for control circuits supplied by transformers. Clause 7.3 was previously one clause dealing with overcurrent protection of motors. However, the new standard has three separate clauses looking at overload, over-temperature and current limiting. Clause 8.2 relates to protective bonding; the new standard adds a clause concerning mobile machines. Clause 8.3 has been retitled "Functional Bonding". Also, whereas this was previously three clauses, it is now just one. Clause 9.1.4 of the old standard related to the connection of control circuits and was concerned with switching elements in the conductors connected to the protective bonding. However, this clause is deleted from new standard. Clause 9.2.5.4.2 refers to the emergency stop function. The comments regarding the use of programmable systems and systems using communication networks or links has been removed. Clause 9.2.7.4 , relating to serial data communications, is deleted in the new draft. Clause 9.3.2 was previously titled "Overtravel limits"; it is now renamed "exceeding operating limits" and includes speed, pressure, etc. Clause 9.3.4.1 relates to earth faults. This clause is expanded in the new standard and outlines three methods; drawings are included. Clause 10.7 relates to devices for emergency stop. Three sub-clauses are deleted from the new standard, but otherwise the general gist remains as before. Clause 10.8 , relating to emergency switching off, has been changed a little but, again, there are many similarities between the old and the new. Clause 10.9 is a new clause entitled "Enabling control devices". This gives advice on the operation on hold-to-run type devices. Clause 11 of the old standard, relating to electronic equipment, has been deleted in the new draft and, as a result, the old clause 12 has been renumbered as clause 11 in the new standard. Clause 13 , relating to conductors and cables, is likewise renumbered as clause 12 in the new standard. Clause 14 , relating to wiring practices, becomes clause 13 and the text appears to be little changed. Clause 15 , relating to electric motors and associated equipment, becomes clause 14 and, again, the texts are very similar. Clause 16 , relating to accessories and lighting, becomes clause 15; textual changes are minimal. Clause 17 , relating to markings, warning signs and reference designations, is renumbered clause 16. Clause 18 , relating to technical documentation, becomes clause 17 and has very few textual changes. Clause 19 , previously entitled "Testing and verification", is retitled as simply "Verification" in the new standard, and is also renumbered as clause 18. In addition, many more clauses have been included to cover test methods in TN systems. These are mainly concerned with the verification of the bonding circuits. Aside from the main body of the standard, there are also changes in the annexes. A new Annex A is concerned with protection against indirect contact in TN-systems. Annex B is unchanged. A new Annex C gives examples of machines covered by the standard (and is therefore similar to the old Annex A). The new Annex D is similar to the old Annex C, relating to "current carrying capacity and overcurrent protection of conductors and cables ". The new Annex E is the same as the old Annex D, relating to "Explanation of emergency operation functions". Annex F is a new annex entitled "Guide for the use of this part of IEC 60204". Annex G corresponds to the old Annex E, being a bibliography. Closing remarks Although there could be some detail changes between this draft and the final standard - and major changes are possible but far less likely - machine builders and system integrators now have a clearer picture of the situation as it may be in the near future. Nevertheless, it should be noted that the EN version of the standard will almost certainly differ in the detail from the versions of the standard that will be published in the USA and elsewhere. As with anything relating to standards, check everything and assume nothing.

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