Safety
protocol type to another. IP connectivity allows the Commander to be located locally to the distributed network panels, but at the same time caters for remote programming and remote third-party system access. Te PLC takes data from the Commander and performs actions based on what the received signals are, for example, displaying icons on the touchscreen for alarms. Similarly, actions are performed within the PLC based on communication with the touchscreen Human Machine Interface (HMI). Te PLC systems used here are based on fail- safe SIL2 architecture to comply with the requirements of IEC61508. Te company has in-house TUV functional safety certified engineers who will ensure that systems are verified and validated prior to release of the software to site. Te SIL2 fail-safe CPUs have safety functions built in
to the software and hardware to ensure that monitoring and proof testing of outputs can be easily activated and reported. Te alarm and diagnostic functions of the application program are used to alert the operators within the internal and external HMI and third-party systems. Local HMI applications provide control, visualisation, alarm annunciation and diagnostic of the PLC and fire alarm systems. For any control functionality good engineering practices will always be used to prevent inadvertent single-click activation of control. Tis can be an issue with touchscreen HMIs with the screen saver activated. Terefore, all control actions are implemented with selection and confirmation prompts to validate the actions to the PLC system, with confirmation prompt designed to be in a different area on the screen than the initial
selection to ensure the operator confirms the action. For interaction with other equipment,
the PLC is capable of communications with third party systems with a variety of protocols allowing integration to provide a simple, single operator interface.
The bigger picture With careful and considered selection of the right components and implementation of the system, digitalisation of safety systems is possible, providing an effective solution to protecting remote or unmanned assets, reducing costs to the client and improving safety and efficiency of the asset. l
Stephen Pratt is safety critical systems manager at Blaze Manufacturing Solutions
www.blazeman.co.uk
www.engineerlive.com 39
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