Modular safety system avoids PLC complexity

Modular safety system improves safety and removes cost and complexity of PLC based safety system on 100m long corrugator machine.

Modular safety system improves safety and removes cost and complexity of PLC based safety system on 100m long corrugator machine.

Installing an Allen Bradley Guardmaster MSR200 modular safety system on a 100 metre long corrugator machine with multiple safety interlocks has enabled Mondiboard Coalville to improve safety through enhanced monitoring and faster alert signalling.

The advanced facilities offered by the MSR200 have also removed the requirement for a PLC in the safety system of the machine, overcoming the cost, maintenance and system update problems associated with multiple wiring of safety trip devices to a centralised controller.

Mondiboard Coalville is one of 30 plants owned and operated by Mondi in the UK.

The site produces fibreboard packaging sheet from raw paper material.

The board is graded in terms of thickness and strength to suit client requirements (packaging assembly and box manufacturing companies), and is supplied flat and scored ready for assembly.

The fibreboard is produced on two 100m long corrugator machines, each having 17 safety trip devices, varying from Allen Bradley Guardmaster Lifeline stop switches to emergency push button stop switches, guard locks, proximity sensors for belt alignment and power overload trips.

Both machines have been converted from a system employing a series of safety relays wired individually to a PLC in a control room, to an MSR200 modular safety system.

The latter wires directly to the safety trip devices on the corrugator machine, and directly to a display in the control room via a simple shielded two-wire connection - an arrangement that completely removes the requirement for a PLC.

The problem with the PLC- based system was the large amounts of wiring and programming it required.

These meant that any maintenance to the system, changes, upgrades and replacement of parts was time consuming and complex and had to be carried out in the few, long planned plant shut down periods available to Mondiboard.

The MSR200 system, in contrast, can be updated and added to quickly and easily because of its simplicity.

Even the unit's display is quickly programmed; the "alert" descriptions and positions on the machine accomplished using a Windows based software utility downloaded from the Guardmaster web site.

Underlining the flexibility and modularity of the MSR200, the maintenance team at Mondiboard are planning, in early 2004, to replace pad locks on the main machine gate access doors with Guardmaster trapped key interlock systems.

Integrating these interlocks into the safety system using the MSR200 will be an easy and fast operation, requiring just a simple rail mounted plug in module and a brief display update using a laptop and an RS232 connection to the display.

This contrasts with the many metres of wire and installation time - plus reprogramming, that would be required to effect the same installation with the previous PLC- based system.

In addition to its many production, maintenance and installation benefits, the MSR based system also improves safety on the corrugator machines, the "alert" signal provided being faster and more informative about which safety circuits have been broken.

This enables faults to be identified faster in the case of genuine emergencies, and also means that the machine can be up and running faster in the case of false alarms.

MSR200 Modular Safety System - the MSR 200 is a Safety Category 4 (Stop Category 0/1) system, offering features that are ideal for today's increasingly decentralised control environment.

Easily expandable, the MSR200 overcomes the problems of complicated individual wiring of safety relays, and the cost of programmable systems, with a modular design that allows the required number of safety control outputs to be configured exactly to specific application requirements.

This is achieved using a combination of autoconfiguration modules, which require no programming, and simple plug and play technology, which ensures easy and reliable set-up.

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