Applying flexibility, safety, and control

Learning how flexible and configurable I/O can be applied to more than safety systems could open many doors regarding how engineers approach automation and control projects.

06/12/2013


The cover story in this issue of AppliedAutomation is as much about I/O as it is about safety. While safety systems are fundamental to critical processes and operations, extrapolating the implications of how flexible and configurable I/O can be applied to more than safety systems could open many doors regarding how engineers approach automation and control projects.

This issue also includes a case study about a safety system upgrade at the SLAC National Accelerator Laboratory at Stanford University. Although the lab’s original 1940s-era relay-based system was functional, it had exceeded its useful life span. The lab upgraded its relay-based safety system with a new control and safety platform based on a safety PLC, which includes a safety controller and distributed safety I/O. The new system provides SLAC with preventive maintenance alerts and diagnostic capabilities that were not possible with the relay-based system.

The third article revisits temperature control. Tuning PID control loops can be challenging, and this article offers guidance on proper loop tuning. While most modern temperature controllers employ auto-tune features, units from different manufacturers may not behave the same way. Because control loops are in fact closed loops, tuning is inherently application dependent. The quest for ideal tuning assumes that the system is properly designed. Because the physical environment is part of the loop, the available Btus must be appropriate for the load. As the authors state, “The system is tuned well when it heats up and settles quickly at setpoint and when the temperature settles at a new setpoint without oscillating excessively.” The authors also point out that “quickly” and “excessively” are relative terms. 

See links for ways to manage process safety.



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