In many industries, a Distributed Control System (DCS) serves as the hub of a processor’s operations and controls and monitors key variables such as flow, applied temperatures, pressure, level, and material conveying/handling. The DCS’ HMI collects all the data from the production equipment and presents it in a highly “human-factored” manner for an operator.
However, many factors affect DCS design such as:
- the type of equipment
- the material processed
- the operator’s actions
- the control system
Still, the DCS must be robust and designed to handle common, expected disturbances as well as unexpected anomalies in a predictable way. One of the best ways to achieve this aim is by standardizing programming and design by:
- committing to a shared design philosophy
- using tools and techniques that reduce programming complexity
- adopting best practices like the ANSI/ISA 18.2 Standard, whichaddresses the entire lifecycle of alarm management
“Basically, the ISA committee determined that an alarm should only be used if it requires an operator’s response. That is probably the number one thing most processing plants violate. They use alarms for all kinds of notifications, alerts, and reminders,” says Robert M. Ard, Director of Applications Engineering at Valmet, a leading global developer and supplier of process technologies, automation, and services for the pulp, paper, energy, marine, and other process industries. Valmet recently acquired the D3 Control System from NovaTech Automation.
DCS Design Example: Alarm Management
Problem: 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.
Solution: 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 notifications, alerts, and messaging.
For example, Valmet’s D3 DCS is designed to meet or exceed the requirements outlined in the ISA-18.2, albeit with slightly different terminology. This includes limiting alarms, supporting alarm prioritization, alarms by classification, and allowing dynamic alarm management.
For more information, visit www.valmet.com or call 410-753-8300.