March 2020

63 www.drivesncontrols.com March 2020 MACHINE SAFETY n Stay safe by avoiding unexpected start-ups of automated machines I t is often necessary for personnel to enter a danger zone to performmaintenance, so being able to ensure that a machine is in a stopped condition is essential. However, as levels of machinery automation have increased, so has the probability of hazards caused by unexpected start-ups, resulting in potential injuries – or lucky escapes. After more than 20 years, BS EN ISO 14118: 2018 has superseded BS EN 1037:1995+A1:2008. It states what procedures should be followed to ensure that personnel can safely enter a dangerous area of a machine. The overriding guiding principle is to ensure that a machine is in a state of zero energy, ensuring that it is isolated from the power supply and that latent energy within the machine has been dissipated. There are quite a few changes to the standard, with some being more obvious than others. I cannot cover all of them in detail, but here are some of the key highlights to ensure that you are compliant. Section 4 ( General measures to prevent unexpected start-up ) introduces a new element requiring that a risk assessment is performed and that procedures to prevent unexpected start-ups are described in the instruction handbook and/or as warnings on the machine. Section 4.4 ( Signalling and warning – delayed start ) is also new. It states that an audible and/or visible warning signal and delayed start shall be provided, if required by the risk assessment, to alert a person to an impending start-up, with the delayed start giving them enough time to leave the danger zone. Section 5 has been renamed Isolation and energy dissipation , and a new sub-section (5.1) now covers unexpected start-up prevention when power supplies are restored. Sub-section 5.2.2 also introduces two new elements when considering the location and number of power supply isolation devices, which must be present to ensure a reliable disconnection or separation from the energy source: n Note 2: where it is necessary to have access to individual parts of large machinery, a separate additional isolation device is required. n Note 3: the isolating device must be located either at the place of the intervention, or along the access route. Locking isolation devices are essential because they stop anyone being tempted to override safety measures. The old and new standards both require that:“The isolation devices shall be capable of being locked or otherwise secured in the ‘isolated’position,”but the new standard goes into much more detail. It also makes a further suggestion about a suitable locking device, in the form of personal keys, which can be released from a trapped- key interlocking device and retained by a person, so that no one else outside the machine can start it up accidentally. Devices for stored-energy dissipation or restraint must now be provided where stored energy can give rise to a hazard. The old standard simply required that the necessary procedures are described in the instruction handbook, or in warnings on the machine. The newer standard adds the requirement (section 5.4.1.4) that“the machine shall not be able to be started with dissipation devices activated or restraint devices in place if this generates new hazards.” When considering measures to prevent unintended actuation of manual start controls, the new standard adds some additional detail (section 6.2.1):“Where a control device is designed and constructed to perform several different actions, namely, where there is no one-to-one correspondence, the action to be performed shall be clearly displayed and subject to confirmation, where necessary.”This is intended to ensure a positive understanding of any action taken by that control, and where this may not be clear, that it is displayed and requires confirmation before the action can take place. Section 6.3 of the new standard covers measures to maintain stop commands. One key update is a note which specifies that the emergency-stop function cannot be considered as a measure for preventing unexpected start-ups. This means that the emergency function must be an addition to any systems designed to prevent unintended start-ups when people enter a dangerous area of the machine, essentially ensuring a“belt and braces”approach to safety. n A recent standard lays down measures to ensure that maintenance personnel stay safe when entering a stopped machine. Paul Taylor, general manager for machinery safety at TÜV SÜD Product Service, explains how it differs from its predecessor. The new standard is designed to ensure that personnel stay safe when they enter automated machinery