The updated Machinery Safety Directive (2006/42/EC) introduced new requirements for machine guards, however some machine designers are failing to take these changes into account. Paul Laidler, business director for Machinery Safety at TÜV SÜD Product Service, explains the requirements
The updated Machinery Safety Directive (2006/42/EC) came into force in December 2009, introducing a range of new requirements for guards, which must now be observed by anyone supplying a machine in the European Union.
While previous incarnations of the Directive referred only to ‘safety components’, the latest edition specifically lists what those safety components are – and one is guarding. However, many machine designers are failing to take these changes into account and do not realise that they are breaking health & safety laws.
Essential health and safety requirements (EHSRs) cover aspects such as guarding that designers must build into their machine before it can carry CE marking, which shows it conforms with all applicable EU standards. A few examples are EN 953, ‘Safety of Machinery – Guards – General Requirements’; EN ISO 13857 – ‘Safety of Machinery – Safety distances to prevent hazard zones being reached by upper and lower limbs’; and EN 349 – ‘Safety of Machinery – Minimum gaps to avoid crushing of parts of the human body’.
Guarding receives specific attention in the ESHRs. Section 126.96.36.199 requires that all fixed guards must be removable only with the aid of tools. While a similar requirement was contained in the previous Machinery Directive, the fixing systems must now remain attached to the guards when the guards are removed. This means that ordinary machine screws and bolts can no longer be used as a means of attaching guards unless provision is made for the screws or bolts to be held captive when the guard is removed.
One of the other requirements of Section 188.8.131.52 states that guards should be incapable of remaining in position when their fixings have been removed. Some careful thinking will therefore be required by designers to ensure, for example, that hinged guards open automatically when they are released, and that guards on the top of machines are not retained in position by gravity when their fixings have been removed.
Foreseeing operator misuse
While a raft of standards underpin the new Directive, when it comes to guarding one of the most relevant is BS EN 1088, ‘Safety of machinery – Interlocking devices associated with guards – Principles for design and selection’.
When designing machinery, Section 5.7 of EN 1088 is one of the key statements to take into account:
“If the specification of the safety interlocking device is such that it is possible to defeat the safety function solely by a reasonably foreseeable action at the interlocking device itself and if the device itself is to be relied upon to prevent defeat, it should provide measures to minimise the possibility of defeat.”
Exactly what constitutes ‘a reasonably foreseeable action’ is explained as an intentional attempt to defeat the interlock either manually or with the aid of some readily available object – i.e. situations when operators are not using machinery correctly or choosing to take short cuts during production. If a manufacturer can prove they took all reasonable steps to ensure that an interlocking device could not be defeated, then it becomes a ‘deliberate misuse’ by the operator, rather than the fault of the company that supplied the machine.
The standard goes further by stating that “defeat in a reasonably foreseeable manner” includes the removal of actuators and switches with the intention of disabling an interlocking device. However, a little thought will show that this requirement has interesting ramifications. How is it possible to fix switches and actuators in such a way that they can’t be removed with normal tools? At first sight, the options are limited to methods such as high-strength adhesives, welding, and the use of special anti-tamper fixing devices such as screws with one-way heads.
The approach most strongly supported by EN 1088 is for companies to recognise the reasons why operators attempt to defeat interlocks (often, it is to improve productivity) and to address these in the machine design. The real question here is whether the machine design can be modified so that the guard no longer inhibits productivity which, in turn, means that the operator will not be tempted to defeat the interlock.
Ignorance is not bliss
Clearly, achieving full standards compliance for a guard to carry the CE marking is no trivial task. CE marking, along with the design and manufacture of guards, now requires specialist expertise as guards perform an indispensable function to minimise the risk of injury as well as meeting the multitude of regulatory requirements.
Since the changes to the Machinery Directive, a considerable level of expertise is now needed to ensure that guards satisfy all regulatory requirements. The plea of ignorance is not acceptable as failing to comply with the Machinery Directive, whether knowingly or unknowingly, can have serious and far-reaching consequences for machinery designers, the businesses that use them and their operators.