Feature Safety legislation Machine EMC cannot be ignored
Paul Laidler, business director for machinery safety at TÜV SÜD Product Service, a global product testing and certification organisation
E
lectromagnetic compatibility (EMC) is an issue that many machine builders find complex and confusing. However, machines offered for sale in the European Union are required to carry the CE marking to show compliance with the Machinery Directive. For any machine that includes electrical or electronic components in order to comply with the Machinery Directive it must also meet the EMC Directive (2004/108/EC).
There can be no doubt about the need for EMC. Who, for example, has not been listening to a radio that has experienced interference ‘chirps’ from a nearby mobile phone? When it comes to EMC and machinery, the situation could be much more serious. For exam- ple, if the control system of a machine experiences electromagnetic interfer- ence it may malfunction and create a dangerous situation. Conversely, if the electrical and electronic systems fitted to a machine generate a high level of interference, they may also cause other equipment nearby to malfunction. It is to help guard against situations like these that the EMC Directive, 2004/108/EC was put in place. In the UK, this directive is implemented by the Electromagnetic Compatibility Regulations 2006.
Understanding EMC requirements To understand the implications of these regulations, a good starting point is to look at the ‘Guide to the Electromagnetic Compatibility (EMC) Regulations 2006’, which can be viewed on the Department for Business Innovation and Skills web- site –
www.bis.gov.uk Section Two of this guide includes statements that can be summarised as saying that equipment must be designed and manufactured so that the electromagnetic disturbance it creates
S6
Paul Laidler, busi- ness director for machinery safety at TÜV SÜD Product Service
is not excessive, and that it has a rea- sonable level of immunity to electro- magnetic disturbances. In addition, a fixed installation, which of course includes the majority of machines, must be installed by applying good engineering practices and respecting the intended use of its components. But how can machine builders be sure that their products really do have satisfactory EMC performance? It is very tempting to think that the answer is to use only components that are themselves compliant with the EMC Regulations. Surely, if all of the com- ponents used in a machine satisfy the regulations, it is reasonable to con- clude that the whole machine must also meet them? Unfortunately, that’s not how it works and it is relatively easy to see why. Consider, for example, a variable speed drive that produces a level of electromagnetic interference about half of that acceptable under the regu- lations. Clearly, there is no problem in stating that this drive complies with the regulations. However, if you put four of those drives on a machine, is it reasonable to assume that the machine complies with the regulations, simply because each of the drives is compli- ant? The machine may be compliant, especially if measures to control EMC have been incorporated in its design, but the point is that it cannot be assumed to be compliant. This prob- lem can be neatly summed up with – ‘CE plus CE doesn’t equal CE’.
Demonstrate compliance But how should machine builders demonstrate compliance with the EMC
Directive? The directive specifies that they should compile technical docu- mentation to show that basic require- ments have been met and then complete a Declaration of Conformity. Nowhere in the EMC Directive does it state that testing is mandatory, but since there is no proven way of calcu- lating or modelling the EMC perfor- mance of a machine, the only way compliance can be verified is by test- ing. This opinion may be considered by some as rather controversial, but when the Health & Safety Executive was asked to comment on this issue, it provided the following statement: “Section Six of the Health & Safety
at Work Act (HSW) places a duty on manufacturers to carry out or arrange for the carrying out of such testing and examination as may be necessary to ensure that the article is so designed and constructed that it will, as far as is reasonably practicable, be safe and without risks to health. In the context of EMC, in most applications it is the electromagnetic immunity of equip- ment that is of interest in relation to Section 6 of the HSW. If it is reason- ably practicable to carry out testing for immunity to electromagnetic distur- bances, the HSW requires this to be carried out.”
This statement leaves no room for doubt about the necessity for EMC testing of machines in the vast major- ity of cases – there is simply no short- cut to achieving compliance with the EMC Regulations. Unfortunately, there is also no doubt that EMC testing can be com- plex and time consuming, especially for the majority of machine builders that lack in-house expertise in this specialist area.
Few would deny that meeting the EMC requirements in relation to machines can be a daunting process, but ignoring those requirements is not an acceptable solution.
There is no shortcut to achieving compliance with the EMC Directive in order to meet legislative requirements and to ensure safety, machines must be thoroughly tested.
TÜV SÜD Product Service T: 01489 558100
www.tuvps.co.uk
Enter 252 JUNE 2012 Machine Safety Supplement
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56