Feature Machine Safety


The risks of installer liability E


Alex D’Arcy of Hylec-APL, offers an insight into the current legislation surrounding emergency stop devices and explains how installers who fail to specify suitable components could be at risk


mergency Stop devices are an essential safety requirement for almost any electrical application which is operated in the public, industrial or commercial domain, such as escalators, large machinery and com- mercial plant vehicles. Such a safety critical device understandably is gov- erned by legislation to make sure that it is suitable for the job in hand. So what are the risks of failing to install suitable emergency stop functions, and who could be found liable in the event of injury caused by component failure? Emergency stop devices are not only important to the safety of the machinery and people in an industrial environ- ment, but they are also often required to be present on production lines, usually within the line of sight of workers. Furthermore, several E-stops may be required on a single machine, as they are commonly required to be mounted as frequently as every two metres along the production line.


Regulations and directives Health and safety in the workplace is at the forefront of developments to modern machinery and there is a raft of regulations and directives from a number of sources that must be imple- mented by machinery manufacturers as well as those using the equipment. Amongst all the ‘red tape’ lies the EU Machinery Directive, 2006/42/EC and the European Standard for the Safety of Machinery Emergency Stop equip- ment, BS EN ISO 13850:2008, which replaced EN 418, all of which define the specific requirements for emer- gency stop devices and actuators. Equipment destined for use within


the EU must meet the requirements of the European Machinery Directive, which includes BS 13850 (EN 418). Initially, Annex I of the directive states, ‘Machinery must be fitted with one or more emergency stop devices to enable actual or impending danger to be averted’. This is accepted as meaning that all machines require an emergency stop unless there are exceptional exten- uating circumstances where the risks cannot be controlled effectively with an emergency stop, or if the risk would be increased or new risks would be intro- duced by the action of an E-stop system. For the majority of cases which will require an e-stop, BS 13850 (EN 418) defines the specific requirements for emergency stop devices and actuators,


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Above and below: Hylec-APL has developed a range of control stations and pushbuttons, including a number of BS 13850 (EN 418) compliant components


which are summarised as follows: ●


All emergency OFF devices must be ‘self latching’ (maintained) devices. With regard to an E-Stop, this means it must be either a twist to release, pull


to release or key to release device. ●


OFF signal. ●


The latching mechanism must be engaged prior to the electrical contact change of state to avoid a momentary


All devices must have a ‘mush-


The background immediately sur- rounding the emergency OFF device


room’ head that is red in colour. ●


must be yellow in colour. ●


All emergency OFF devices must have positive opening operation. This means there must be a direct mechani- cal link between the operation of the mushroom head and the contacts to


drive the electrical contacts open. ●


automatically - manual


The devices must not be reset reset


is a


requirement. The main concept of the standard is that emergency stop switches must have a ‘fool-proof’ capability. Such an emergency stop device incorporates a latching mechanism which is acti- vated when the actuator of the device is operated to a certain point. This latching mechanism prevents the actu- ator from being pulled back out again - it also ensures that the contacts will not


be opened prematurely. The


method by which the actuator is reset must be clearly indicated by arrows which are marked on the actuator or associated legend plate. Resetting the electrical system can


only be done by first releasing the E- stop that was originally activated. If E- stops were activated at multiple locations, all of them must be released before the machinery can be restarted. It should be noted that resetting E-


stops does not in itself restart the machinery - it only permits restarting through normal procedures appropri- ate for the machinery involved. The duty of care to ensure that all machinery complies with these regula- tions and that proper risk assessments have been carried out, falls upon a number of people. Obviously the owner of the machinery and site managers must make sure that all equipment is suitably equipped and that all operators are fully trained. However, also the machine builder, or electrical installer that specified the E-stop component is deemed to be responsible for ensuring that it uses components which are suit- able under European legislation. Failure to do so could lead to a judgement of negligence should a failure of the com- ponent lead to injury or death.


Meeting safety requirements In order to help manufacturers, employ- ers and installers to meet these safety requirements Hylec-APL has developed a range of control stations and pushbut- tons, including a number of BS 13850 (EN 418) compliant components. Available as complete control stations or as individual components for mounting in panels, the range of E-stop buttons and accessories are rated to IP56.


Emergency stop devices are not a replacement for proper safeguarding or automatic safety devices, just as an employee would not be expected to rely on PPE as the foremost protection from danger. Rather, they should be used as a back-up measure which pro- vides manual override of operations in the event that a hazard presents itself. Furthermore, the activation of the emergency stop should not impair the effectiveness of other safety devices fitted to the equipment. Ensuring that all E-stop components conform to BS 13850 (EN 418) stan- dards is the joint responsibility of the machinery manufacturer/installer and the owner and operator of the machine. However, your component supplier should be able to help you choose a product that is suitable. Good suppliers will be knowledgeable about the legislation and will be able to pro- vide you with evidence that their com- ponents meet all the requirements.


Hylec-APL www.Hylec-APL.com T: 01933 234 400


Enter 207 JANUARY 2014 Automation


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