FEATURE ATEX EQUIPMENT
HYBRID SAFETY
SWITCHES S
ome good news on work-related fatalities in the UK: according to the HSE they fell
between April 2019 and March 2020 to 111, the lowest total on record. This has got to be due to a combination of stringent safety measures introduced over the years to eliminate or control the risks in the workplace, and the availability of high-quality equipment to help meet those obligations. It is impossible to walk into a factory these
days and not see myriad machinery safety measures such as safety switches, rope pull switches and guard locking – and thankfully there are plenty of engineers who are very knowledgeable on safety requirements and the most suitable equipment for each application. Likewise there are many processing environments to which the ATEX directive applies – and guess what? Plenty more specialist engineers and safety equipment solutions. What there is not quite so much of is safety
equipment that offers a solution when both ATEX and machinery safety demands are in play. What happens then? To prevent access to machinery in such a processing area requires equipment that is certified for use in ATEX areas as well as for machinery safety. It is not exactly every day this crops up – and that is probably why there has not been much growth in such dual-function solutions such as switches over recent years. Until now, that is. The fact is, equipment such as conventional
switches for monitoring or securing doors are generally not suitable within facilities where combustible materials including gases, vapours, mist or dust could be present. Similarly, the common ATEX safety switch and locking solutions for these zones often fall short of the applicable machinery safety standards, including EN-ISO- 13849-1 (safety-related parts of a control system) and EN-ISO-14119 (safety of machinery:
14 SUMMER 2021 | INDUSTRIAL COMPLIANCE BRINGING THE BEST OF BOTH
WORLDS IN REDUCING RISK There is machine safety, then there are ATEX safety measures, and plenty of specialist engineers work in both fields – but what happens when those two worlds collide? David Dearden, UK&I country manager of leading safety specialist Euchner, examines how best to unify machinery and ATEX safety and suggests a singular solution.
interlocking devices associated with guards). We have seen and heard about some rather
inventive implementations by engineers who should really know better. Taking a gamble with just a standard ATEX switch and barely a nod to machinery safety? Check. Or maybe doubling up switches to ensure that a single failure does not knock off all safety functions? Check. But why take any chances when there is now a range of switches pioneered by Euchner that cover both ATEX standards and machinery safety, to a suitable Performance Level (PL r) according to EN-ISO-13849? Since there is a huge choice of ATEX switches
that are applicable to hazardous environments, and an equally huge choice of switches applicable to machinery access safety, why not just select one of each and have done with it? Simple – the sum of the two do not make a satisfactory solution. It is a lot less hassle, safer and more cost-effective to go with a single switch that covers all your bases. Euchner combines the strict requirements of ATEX protection with the innovative engineering principles for machinery safety, such as using RFID to prevent
manipulation, to provide extremely safe and well-built equipment for the demanding applications that fall into the hybrid position. To cover safety requirements across the
board and ensure a high level of protection against tampering, dual-purpose switches should contain a uniquely coded transponder actuator, meeting the highest safety category and Performance Level (PL) according to EN ISO 13849-1. Many devices within Euchner’s range, for example, also significantly surpass the requirement in EN ISO 14119 for a type 4 switch with high coding level. When unicode is specified, the actuators must
be taught-in on the safety switch and during this operation the actuator code is assigned to and saved in the safety switch. Whenever an actuator is read, the safety switch compares the code just read with the code last saved. The actuator is recognised and the safety outputs/status signals are switched only if the two-bit patterns are identical. Simple, but highly effective. Beware of using multicode where the possibility of manipulation exists as there is no exact comparison of the actuator
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