Safety instrumented functions (SIFs), also known as safety valve loops, are comprised of a sensor to sense the process condition, a logic solver to decide the safety action to take, and a final element to perform the action. Emerson's Riyaz Ali and I & C Specialist's C B Chakradhaar gave a presentation at the 2010 Emerson Exchange focusing on the final element in the loop. Their presentation, SIS "Final Element" Diagnostics Including The SOV, Using A Digital Valve Controller, explored the safety functions that rely on valves as their final element. These must operate on demand to make the process safe.
Some of the diagnostic alerts that help reduce PFD include stuck valve indication, low supply pressure, valve travel, shaft integrity, and travel and pressure deviation. Special safeguards are build into the DVC6000 SIS such as safety demand automatic override of a PST and write protection to deter local, unauthorized access to calibration or configuration parameters.

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