September 2021

n SWITCHING INTO SAFETY ENGINEERING Switching into safety engineering - The future of safety engineering O EE (Overall Equipment Effectiveness) is the gold standard for measuring manufacturing productivity. It identifies the percentage of manufacturing time that is truly productive. An OEE score of 100% means you are manufacturing only Good Parts, as fast as possible, with no Stop Time. The advent of Industry 4.0 technologies has improved the ability of production managers to obtain more data about the operation of their machines and processes. Measuring OEE is a manufacturing best practice. By measuring OEE and the underlying losses, important insights are unearthed on how to systematically improve the manufacturing process. It transpires that a manufacturing process where safety considerations are paramount are often the most productive, because there are fewer shutdowns due to machine stoppages. Safety on the bus For years, it has been normal to ensure safety at machines by means of extensive wiring and related switches. Wiring is visible and therefore tangible, which reinforces the feeling of safety. The safety logic intercepts any faults that occur in the wiring and thus the safety requirements are met in full. This begs the question "Why change this?" However, there are some very good reasons for considering the use of a safety bus system. One is the significantly reduced wiring work. At least as much safety can be achieved by using a bus system as with conventional wiring. There are many bus systems for every conceivable automation task. Often which bus system is used depends on the control system technology used. In Europe, above all PROFIBUS - and its successor PROFINET - is dominant, while ASI and EtherCAT are significant. Conversely, DeviceNet or its successor EtherNet/IP dominate in the USA. On the Asian market there is no one really dominating bus system. The more European companies can gain a foothold in the Asian and American markets, the more the related bus systems will spread in these markets. Security Issues Systems that are connected to a bus network are potentially at risk of intrusion. A cyber- attack could lead to the safety system being degraded or disabled. The safety of a machine is directly dependent on authorised access to functions and danger zones. Over time, various approaches have been developed to ensure that personnel can only obtain access to potentially dangerous machine functions under certain conditions. Safety guards on many machines and installations still must be overridden for maintenance and servicing work. Thus, service engineers have more access rights than machine operators. Providing a variety of operating modes allows the operator to select the required operation mode (eg setup) and activate the suitable safety guard (eg enabling switch). A very common method is the use of keys that permit the holder to use certain functions on a machine. An alternative is restriction via password. Both approaches have weaknesses: both keys and passwords can be exchanged between personnel. Passwords can easily be forgotten, or compromised very quickly. Electronic-Key-System (EKS) Euchner's Electronic-Key-System (EKS) acts as a replacement for both. It consists of a read station and at least one Electronic-Key. The Electronic-Key contains a writable memory. With the EKS, applications such as access to control systems/operating parameters and entry of an expiration date can be realised in addition to selection of operation mode. The Electronic-Key data are transmitted from the read station to the control system via the data interface (e.g. ProfiNet, Profibus, USB, Ethernet TCP/IP). Unlike passwords or conventional keys, EKS Electronic-Keys cannot be easily copied. With EKS, management always retain an overview of its group of users. If a key should be lost, it can be blocked. EKS Electronic-Keys can be allocated to individual people. Responsibility is thereby visibly transferred to the Electronic- Keyholder, effectively preventing Electronic- Keys from being passed along or left inserted. On many installations, there are particularly dangerous tasks that can be performed only with open safety doors and, in some cases, only at full speed. Persons must be specially trained to perform these tasks. The EKS with data interface offers the option of storing verification of training on the Electronic-Key. The dangerous work can then be performed only with valid verification. The EKS Light, can perform only a single function such as controlling access to selection of operation mode. The EKS FSA (For Safety Applications) offers additional options for improving selection of operation mode and making it safer. FSA devices have a second channel, which is generally available in the form of an additional output. This output is always evaluated for safety purposes. Using the EKS FSA, it is possible to develop a procedure permitting selection Recent developments relevant to safety engineering come inmany guises. In the fifth of a six-part series, Andy Pye reviews some of the significant ones. Sponsored by Part Five of a Six-Part Series