Process safety enhancement of feedforward control using foundation fieldbus

Abstract

This paper presents a practical technique in engineering phase for enhancing safety of Foundation Fieldbus (FF)-based feedforward control through propagation of measurement validity and status information in the loop using function block language to prevent hazards in the presence of a transmitter failure. The proposed technique is based on fault diagnosis of FF devices to increase the safety beyond that found in basic control loops using traditional technologies. For hybrid architecture by assigning basic and advanced function blocks to execute in H1 field instruments and H1 interface module, respectively, all possible cases for configuring parameter options not only to shut the loop down when the failure occurs but also to resume the loop to normal when the failure disappears are described. The feedforward on temperature control of H1 segment configured and operated on the DeltaV integrated host is used for experimentally testing the correctness of the defined parameter options to provide function block interlocks and failsafe actions as well as fault recovery mechanisms. In addition, the Petri net model to represent the control loop behaviors for comparing the process safety enhancement in different scenarios from five cases of parameter configurations is also included.