Electricity and Control July 2023

CONTROL SYSTEMS + AUTOMATION

A DCS serves as the hub of a process operations and controls, monitoring key variables. graphical HMI. With standardisation top of mind, even seemingly minor details in the design of the presentation of the information have been considered in the high performance HMI layouts. Examples include consistent alarm notification terminology and phrasing, location on the screen, and colour-coding. “A well-designed graphical user interface improves sit uational awareness, reduces workload, and enables the operator to view the entire process at a glance so they can focus on mitigating any abnormal situations that may arise,” says Ard. Although the best practice for any control system has at its core a standardised approach to configuring the appli cation software, the challenge of designing a system from the ground up can be daunting. Ard is writing a comprehensive guide for control system design to assist processors in this endeavour; it is due to be published in Q4 of 2023. As well as presenting general guidelines control system engineers should know or con sider when tackling any DCS project, the book elaborates on the critical role of standardisation and includes exam ples of programming specific to the Valmet D3 DCS. “It is clear that a properly designed DCS can deliver robust and predictable control with constant monitoring of process conditions, clear and concise communications with operators, and smart alarm management – as long as we keep in mind the three most important factors: it’s all about standards, standards, and standards,” Ard emphasises. □

A well-designed DCS can deliver robust and predictable control, providing constant monitoring of process conditions. or visible means of indicating to the operator an equipment malfunction, process deviation, or abnormal condition re quiring an operator’s response. Poorly designed and maintained alarm management systems can overwhelm operators with chattering and nuisance alarms under normal conditions and debilitating alarm floods when abnormal states emerge. When this oc curs, it can be difficult for operators to ascertain and act on the most critical alarms, contributing to abnormal situ ations, lost production, and sometimes serious accidents. Recently, organisations like ANSI (American National Standards Institute) and ISA (International Society of Automation) have released updated guidelines related to alarm management. The ANSI/ISA 18.2 standard addresses the entire lifecycle of alarm management, from design and configuration through performance monitoring, auditing, and enforcing for the life of the control application. “Basically, what the ISA committee determined was that an alarm should only be used if it requires an operator’s re sponse,” Ard highlights. “And that is probably the number one factor that most processing plants violate. The tenden cy is to use alarms for all kinds of notifications, alerts, and reminders.” Leading process automation companies like Valmet have incorporated more of a standards-based approach to application development, focusing on differentiating alarms that require immediate attention from less urgent notifica tions, alerts, and messaging. Ard says Valmet’s D3 DCS is designed to meet or ex ceed the requirements outlined in the ISA 18.2 standard, al beit with slightly different terminology. This includes limiting alarms, supporting alarm prioritisation, ordering alarms by classification, and allowing dynamic alarm management. Standardisation of the HMI To facilitate operator monitoring and control, the DCS uses human machine interfaces (HMIs) to provide a visual over view of process systems and to monitor critical status and control information. The Valmet D3 interface, for example, displays real time process information in a complete customer-oriented

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JULY 2023 Electricity + Control

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