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When Board24 made a £7.5m investment in its corrugated packaging, sheet board and box production facility in Preston, Lancashire, it also took on the challenge of updating the safety systems on its existing machinery to be best-in-class. As a result, Board24 achieved an exemplary integrated safety system for its existing Mitsubishi corrugator with a design developed by industry-specialist system integrators JKSP and enabled with SICK Flexi safety controllers and software.
Installed in 1995, the 120m-long Mitsubishi corrugator has a line speed of up to 300m a minute and a maximum sheet width of 2.5 metres. The corrugating machine comprises a Wet End and a Dry End process during which the paper is fluted, laminated, glued, cut and stacked.
Lee Bullen, Corrugated Services Manager of Board24 takes up the story: “We undertook a safety audit according to PUWER98 and as a result identified an opportunity to upgrade the safety system on the existing machine to bring it right up to date with current standards. An important problem that we needed to fix as part of the system upgrade was the amount of production time being lost through use of the emergency stop for non-safety reasons. The corrugator line operatives used to press the E-Stops for incidents that were not emergencies, for example to deal with a breakage or misfeed.
“It might happen that someone would hit an E-Stop on a Sunday run. Then, maintenance would come in on Monday and spend many hours trying to find the E-Stop that had been activated, while the line remained down.
“We had a word for it: we called it a ‘ghost stop’. We would need to spend a lot of time going around the machine opening and closing gates to try to reset the system. Even when the operator in the control room would confirm the E-Stop had been deactivated, it was often not possible to identify which switch had stopped the machine.”
Board24 turned to JKSP, a Warrington-based system integrator with specialist knowledge of installing safety systems for packaging and corrugating machinery all over the UK. In consultation with Board24 and SICK, JKSP devised a safety zoning plan with different spans of control for the global and local safety functions so that the machine can run more safely and efficiently.
As designed by JKSP, the function of the new safety system is to control all safety devices and actuators within the corrugator zone. The layout has been designed to deliver the full capability of the corrugator, while offering the highest levels of safety to ensure protection to operators in the event of a hazard occurring.
Ellis Brown, Electrical Design Engineer, JKSP, explains: “A key requirement was to have a global emergency stop. As the safety system spans over a great distance, it also required zoning for non-emergency stops. This is organised as a global stop loop and stop loops for each zone. A major benefit of the Global Emergency Stop System is that it gives the operators of the Wet End and Dry End the ability to hit an Emergency Stop at one end of the corrugator knowing that it will disable the other end also.
“Global Emergency Stop pushbuttons positioned at strategic points along the machine act as a total system stop. Each zone has local safety and the information needs to be shared between zones. This creates a global network so, if an E-Stop pushbutton was pressed on zone 1, then every zone would react by operating full system safety shutdowns.”
Flexi Soft design for safety and productivity
Using the SICK Flexi Soft system made design, installation, diagnostics and commissioning easier and quicker, Ellis continues: “We were looking for a networked safety solution that offered communication both between and across safety zones. SICK Flexi Line and Flexi Loop delivered both of these, where other manufacturers could only offer one or other. So, we were able to complete a fully compliant update of the whole line and use zoning to create Spans of Control.”
Additional functionality and installation savings
SICK Flexi Line enables up to 32 Flexi Soft stations to be easily connected via twisted pair cable allowing a virtual safe process image to be linked to all zones. Connecting stations in this way offers a very simple, cost effective method of connecting E-Stop information between different parts of machines to high safety levels (PLe/SIL3). It also allows easy implementation of span control using function block logic rather than complicated wiring.
JKSP also took advantage of the ability within SICK Flexi Loop to add auxiliary circuits and developed a Fast Stop system, as a non-safe machine stop condition for production issues such as machine jams and threading/spooling. For example, across the Single Facer 1, pushbuttons are provided as a fast stop procedure for the main drive to shut down, if a paper jamming problem occurs.
Easy fault identification and better production flexibility
The SICK Flexi Soft gateways enable diagnostic information to be displayed on local HMIs identifying which safety device has been pressed. HMI viewpoints local to the production line aid rapid location of the cause of stoppages. In this way, time spent checking an entire line or zone for an unidentified fault is saved, so there is less production downtime.
“If someone does hit an E-Stop and then walks away from it, the action is on an HMI indicating which one’s been hit,” adds Lee Bullen. “Then the operator can easily identify the cause of the stop and reset it, rather than having to go around the whole machine checking all of the Emergency Stop buttons.”
SICK Flexi Line demonstrated particular benefits in the upstairs LV Panel Room where all the main drive motors are located. Without Flexi Line, it would have been necessary to run 20 cables through the room wall and a large cable entry would have needed to be constructed. Instead, the Flexi Line installation required just one Flexi Line cable and one PROFINET cable, to carry all the control, diagnostics and feedback information.
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