the smallest common denominator - global emergency stop

Jan 11, 2017

Icelandic company Marel is the worlds leading provider of advanced food processing solutions for the fish, meat, and poultry industries. These solutions are provided in the form of modern equipment, systems, and services. From individual system modules through complex processing lines and beyond to portions packaged ready for consumption by end customers, the company supports every aspect of advanced food processing. Marel requires its production lines to deliver flexibility and modularity. System operators need to be able to replace individual machine modules, integrate new modules into the overall plant, and combine modules in new ways. However, this must be achieved without having to invest huge amounts of time and money in wiring or programming in order to ensure the safe and secure networking of machine modules.   Picture_1

It is for this reason that Marel chose to draw on SICKs safety expertise. Working in collaboration, the two companies have created a solution that is simply genius: the Global E-Stop. Marel uses a variety of machine modules on its processing lines. Simple machines can be protected with relay technology; complex machines require a safety controller. In cases where safety functions in one machine module need to be available to other modules as well, the process logic of these overarching functions has to be networked. The latest point at which this can happen is when the individual machine modules are put together in the overall equipment network. If a fault occurs, it may be sufficient to shut down just one machine, depending on the nature of the problem and where it has arisen. However, in some cases (continuous material transportation applications is one example) all upstream machine modules have to be shut down too, in order to prevent damage or product losses. It is a question of identifying the right overarching safety function which can also be relied upon to deliver flexibility and safeguard system throughput. Marel uses SICKs Flexi Soft softwareprogrammable safety controller in complex machines. The Flexi Line interface is designed to support the safe and secure networking of modular machine elements. This is due primarily to the inclusion of this functionality in the Flexi Soft main module as standard. In modular systems with a small number of complex machine modules, where using a Flexi Soft safety controller for each of them would be too laborious a solution, networking with Flexi Line was one option, but Marel considered this excessive. So the company had to look for a solution that was more straightforward yet still comprehensive. Picture_2


Global E-Stop

It was important that safe controllers used in machine modules which have been manufactured separately can still be combined at their subsequent installation site in as little time - and with as little effort - as possible. Ideally, it should also be possible to do this without the need for addressing - in other words, by simply connecting and then teaching in to confirm. So the developers from SICK integrated a cut-down version of the Flexi Line functionality into a new module for the Flexi Classic safety controller. The new Global Unit module (GU module) makes provision for a global emergency stop function. Multiple GU modules can be interconnected using a special signal. Each GU module knows its direct colleague, as they have previously been introduced via teach-in. All applications provided by a GU module, each selectable via a rotary switch, have a global emergency stop function. This function acts on all of the safety outputs in the system. In plain English, this means that pressing an emergency stop pushbutton on a GU module stops all other safety outputs of the interconnected modules. To reset the global emergency stop (Global E-Stop), the reset function must be activated on the same GU module on which the emergency stop button was triggered (local reset).


Safety is always exciting when it permits flexibility

The concept for Marel makes provision for one GU module for each machine module. The system operator simply interconnects all of the Flexi Classic nodes and Global E-Stop is ready. The signal lamp on a machine module flashes when that machine module triggers a global emergency stop. The lamps on the other modules simply light up but do not flash. In more complex machines, the Flexi Soft software-programmable safety controller is responsible for the higher-level safety function. The market is looking for a way to safely and easily network modular machine modules that might be equipped with their own dedicated safety controller, says the engineering team of Marel, describing the starting point for the collaboration between the two companies. Higher-level controllers entail a great deal of manual programming, especially if machines from different manufacturers are being used - and this goes beyond just the initial programming work they require. It is particularly felt in the amount of work required to carry out changes, and not only costs time and money, but also makes the system more complex. Together with SICK, we have developed a simple, elegant, and customer-focused solution. Safety is always exciting when it permits flexibility.



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