Process automation systems and safety instrumented systems (SIS) have been changing with the rapid pace of technology change. An ARC Advisory Group whitepaper, Business Issues Driving Safety System Integration, outlined some of the various ways automation suppliers have been integrating these systems for process manufacturers. They described three integration levels: interfaced, integrated, and common.
Emerson’s Chuck Miller has written a whitepaper, Realizing the Capital and Operational Benefits of a ICSS System. It explores how the technologies and integrated approach of the basic process control system (BPCS) and SIS, combined with work processes, can improve capital expenditure (CapEx) and operational expenditure (OpEx) performance.
In the whitepaper, Chuck describes the integrated control and safety system (ICSS) that is built upon redundant Ethernet control networks, distributed and scalable process controllers, distributed and scalable safety controllers, human machine interfaces (HMIs), engineering workstations, and application servers. He describes how CapEx savings can be achieved if the engineering tools are common when configuring the process and safety controllers and the HMI is common in communicating with the controllers. Functions such as alarm handling, time synchronization, user security, and device health monitoring are also shared between systems.
Another example on the CapEx side is compliance with the IEC 61511 international safety standard. Device audit trails, calibration histories, process and safety configuration audit trails, process and event histories all contribute to the detailed documentation and change management required for a process manufacturer’s safety management program.
For the safety instrumented functions (SIFs) managed by the safety controllers (or logic solvers in safety parlance), Chuck notes the importance of diagnostics from the sensors and final control elements. From a sensor standpoint, HART device alerts can be sent to operators and maintenance personnel as an early warning of problems with the device or surrounding process (see my earlier HART diagnostics post). For final control elements, non-disruptive actuator partial stroke testing can be performed to make sure the safety valves do not become stuck from long periods of inactivity.
These predictive tests help on the OpEx side of the equation. Through a continuous process of detection and notification, which in turn feeds the work process associated with rapid correction, spurious trips and on-demand failures can be avoided. Chuck uses the analogy of an automobile service technician. The process begins by performing diagnostic tests. With the results in hand, the person or people with the right set of skills can be assigned to resolve the situation quickly.
Similarly, process manufacturers can organize to take advantage of the diagnostics within both the process automation and safety instrumented systems to avoid unplanned shutdowns and respond more quickly to abnormal situations.
Give the whitepaper a read for many more ways both the CapEx side and OpEx side of your plant budget are impacted by the integration of these systems. Also, look for and join the discussions on SIS integration in the Process Automation Usability Project site, on the DeltaV SIS LinkedIn group, and from the @DeltaVSIS Twitter account.
